There is provided a substantially binder-free catalytic molecular sieve which has been modified by being ex situ selectivated with a silicon compound. The ex situ selectivation involves exposing the molecular sieve to at least two silicon impregnation sequences, each sequence comprising an impregnation with a silicon compound followed by calcination. The catalyst may be used in a hydrocarbon conversion process, such as toluene disproportionation.

The present invention is directed to a selectivated binder-free catalytic molecular sieve.
The term xe2x80x9cshape-selective catalysisxe2x80x9d describes catalytic selectivities in zeolites. The principles behind shape selective catalysis have been reviewed extensively, e.g., by N. Y. Chen, W. E. Garwood, and F. G. Dwyer, Shape Selective Catalysis in Industrial Applications, 36, Marcel Dekker, Inc. (1989). Within a zeolite pore, hydrocarbon conversion reactions such as paraffin isomerization, olefin skeletal or double bond isomerization, oligomerization and aromatic disproportionation, alkylation or transalkylation reactions are governed by constraints imposed by the channel size. Reactant selectivity occurs when a fraction of the feedstock is too large to enter the zeolite pores to react; while product selectivity occurs when some of the products cannot leave the zeolite channels. Product distributions can also be altered by transition state selectivity in which certain reactions cannot occur because the reaction transition state is too large to form within the zeolite pores or cages. Another type of selectivity results from configurational constraints on diffusion where the dimensions of the molecule approach that of the zeolite pore system. A small change in the dimensions of the molecule or the zeolite pore can result in large diffusion changes leading to different product distributions. This type of shape selective catalysis is demonstrated, for example, in selective toluene disproportionation to para-xylene.
The production of para-xylene is typically performed by methylation of toluene or by toluene disproportionation over a catalyst under conversion conditions. Examples include the reaction of toluene with methanol as described by Chen et al., J. Amer. Chem. Soc. 101, 6783 (1979), and toluene disproportionation, as described by Pines in The Chemistry of Catalytic Hydrocarbon Conversions, Academic Press, NY, 72 (1981). Such methods typically result in the production of a mixture including para-xylene, ortho-xylene, and meta-xylene. Depending upon the degree of selectivity of the catalyst for para-xylene (para-selectivity) and the reaction conditions, different percentages of para-xylene are obtained. The yield, i.e., the amount of xylene produced as a proportion of the feedstock, is also affected by the catalyst and the reaction conditions.
Various methods are known in the art for increasing the para-selectivity of zeolite catalysts. One such method is to modify the catalyst by treatment with a xe2x80x9cselectivating agentxe2x80x9d. For example, U.S. Pat. Nos. 5,173,461; 4,950,835; 4,927,979; 4,465,886; 4,477,583; 4,379,761; 4,145,315; 4,127,616; 4,100,215; 4,090,981; 4,060,568; and 3,698,157 disclose specific methods for contacting a catalyst with a selectivating agent containing silicon (xe2x80x9csilicon compoundxe2x80x9d).
U.S. Pat. No. 4,548,914 describes another modification method involving impregnating catalysts with oxides that are difficult to reduce, such as those of magnesium, calcium, and/or phosphorus, followed by treatment with water vapor to improve para-selectivity.
European Patent No. 296,582 describes the modification of aluminosilicate catalysts by impregnating such catalysts with phosphorus-containing compounds and further modifying these catalysts by incorporating metals such as manganese, cobalt, silicon and Group IIA elements. The patent also describes the modification of zeolites with silicon compounds.
Traditionally, ex situ pre-selectivation of zeolites has involved single applications of the selectivating agent. It may be noted, however, that the suggestion of multiple treatments was made in U.S. Pat. No. 4,283,306 to Herkes. The Herkes patent discloses the promotion of crystalline silica catalyst by application of an amorphous silica such as ethylorthosilicate. The Herkes patent contrasts the performance of catalyst treated once with an ethylorthosilicate solution followed by calcination against the performance of catalyst treated twice with ethylorthosilicate and calcined after each treatment. The Herkes disclosure, however, shows that the twice-treated catalyst is less active and less selective than the once-treated catalyst as measured by methylation of toluene by methanol. Thus, Herkes indicates that multiple ex situ selectivation confers no benefit and in fact reduces a catalyst""s efficacy in shape-selective reactions.
In U.S. Ser. No. 08/269,051, the first multiple ex situ selectivation sequence of catalytic molecular sieves to enhance selectivity in hydrocarbon conversion reactions was described. These catalysts proved particularly useful in toluene disproportionation as demonstrated in U.S. Pat. Nos. 5,365,004 and 5,367,099 which issued on the 15th and 22nd of November 1994, respectively. The disclosures of U.S. Pat. Nos. 5,365,004 and 5,367,099 are herein incorporated by reference.
However, because the para-isomers of alkyl-substituted aromatic hydrocarbons (e.g., para-xylene) are utilized to produce a variety of commercial products, there is still a continuing need in the art to increase the efficiency of production.
Accordingly, it is an object of the present invention to improve the efficiency of producing alkyl-substituted aromatic hydrocarbons utilizing ex situ selectivated catalytic molecular sieves.
There is provided a method for preparing a catalyst, said method comprising the steps of:
(a) contacting a substantially binder-free catalytic molecular sieve under liquid phase conditions with an organosilicon selectivating agent under conditions sufficient to impregnate said molecular sieve with said organosilicon selectivating agent;
(b) calcining the impregnated molecular sieve of step (a) under conditions sufficient to decompose said organosilicon selectivating agent and leave a siliceous residue of said agent on said molecular sieve; and
(c) repeating steps (a) and (b) at least once.
There is also provided a method for preparing a catalyst, said method comprising the steps of:
(a) mulling and then extruding a mixture comprising water, ZSM-5, sodium ions and no intentionally added binder material under conditions sufficient to form an extrudate having an intermediate green strength sufficient to resist attrition during ion exchange step (b) set forth hereinafter;
(b) contacting the uncalcined extrudate of step (a) with an aqueous solution comprising ammonium cations under conditions sufficient to exchange cations in said ZSM-5 with ammonium cations;
(c) calcining the ammonium exchanged extrudate of step (b) under conditions sufficient to generate the hydrogen form of said ZSM-5 and increase the crush strength of said extrudate;
(d) contacting the substantially binder-free ZSM-5 extrudate of step (c) under liquid phase conditions with an organosilicon selectivating agent under conditions sufficient to impregnate said extrudate with said organosilicon selectivating agent;
(e) calcining the impregnated molecular sieve of step (d) under conditions sufficient to decompose said organosilicon selectivating agent and leave a siliceous residue of said agent on said molecular sieve; and
(f) repeating steps (d) and (e) at least once.
There is also provided a process for hydrocarbon conversions, such as toluene disproportionation reactions, using this catalyst.
Shape selective hydrocarbon conversions over the present modified catalytic molecular sieve may be conducted by contacting a reaction stream comprising an alkyl-substituted aromatic hydrocarbon, under conversion conditions, with the present modified catalytic molecular sieve. The modified catalytic molecular sieve is a substantially binder-free catalytic molecular sieve which had been exposed, preferably, to at least two ex situ selectivation sequences. Each ex situ selectivation sequence includes impregnating the substantially binder-free catalytic molecular sieve with a selectivating agent, followed by calcination after each impregnation. Selectivating agents useful in the present invention include a large variety of silicon-containing compounds, preferably silicon polymers soluble in organic carriers. Such organic carriers include various alkanes, preferably paraffins having 6 or more carbons.
The alkyl substituted aromatic hydrocarbon is preferably an alkyl-substituted benzene, such as ethylbenzene or toluene.
The modified catalytic molecular sieve may be further modified by in situ trim-selectivating the modified catalytic molecular sieve. The in situ trim-selectivation may be performed by coke trim-selectivation wherein an organic compound is decomposed in the presence of the modified catalytic molecular sieve, at conditions suitable for decomposing the organic compound. Alternatively, the trim-selectivation may be performed by exposing the modified catalytic molecular sieve to a reaction stream that includes a hydrocarbon to be converted and a trim-selectivating agent selected from a group of compounds including a large variety of silicon-containing compounds, at reaction conditions.
Advantageously, these modified catalysts have enhanced shape selectivity in the production of alkylaromatic hydrocarbons. The catalysts also provide the advantage of exhibiting enhanced selectivity at lower operating temperatures, which in turn lengthens the effective life cycle of the catalysts. Accordingly, the shape selective hydrocarbon process of the invention exhibits increased selectivity, especially in the production of para-xylene.
It has now been found by utilizing multiple ex situ selectivated catalytic molecular sieves that are substantially binder-free, enhanced selectivity for the para-isomer of the converted hydrocarbon can now be obtained at lower operating temperatures in comparison to catalytic molecular sieves that have been incorporated into a binder.
By reference to xe2x80x9csubstantially binder-free catalytic molecular sievesxe2x80x9d it is meant to include catalytic molecular sieves (or zeolites) that are binderless or unbound, i.e., have not been incorporated into a binder material. However, this phrase does exclude catalytic molecular sieves which may contain trace amounts of binder material as an impurity. Impurities can be inadvertently introduced during the manufacturing process, for example by utilizing equipment that had been previously used to manufacture bound catalysts. Another source of impurities can be non-zeolite material during processing of the unbound catalysts. This can be due to partial dissolution of the zeolite during aqueous treatment, extrusion with or without extrusion aids (e.g., caustics, burnout materials, etc.), steaming and other processes.
The binder-free molecular sieve is preferably in the form of an extrudate. Methods for preparing such binder-free extrudates are described in U.S. Pat. Nos. 4,582,815 and 4,872,968. A particular method for preparing such a binder-free extrudate may involve the steps of:
(a) mulling and then extruding a mixture comprising water, ZSM-5, sodium ions and no intentionally added binder material under conditions sufficient to form an extrudate having an intermediate green strength sufficient to resist attrition during ion exchange step (b) set forth hereinafter;
(b) contacting the uncalcined extrudate of step (a) with an aqueous solution comprising ammonium cations under conditions sufficient to exchange cations in said ZSM-5 with ammonium cations;
(c) calcining the ammonium exchanged extrudate of step (b) under conditions sufficient to generate the hydrogen form of said ZSM-5 and increase the crush strength of said extrudate.
The ability to operate the catalysts at a lower operating temperature provides many advantages which will be apparent to the skilled artisan. First, the reduction in operating temperature lengthens the cycle life of the catalysts. Thus, the catalysts can remain on-stream longer and require regeneration less often. This in turn makes utilizing the catalysts more economical in the sense that there is less down time in the hydrocarbon conversion operation.
The lower operating temperatures also make the catalysts well suited for high conversion processes since the catalysts of the present invention will run at lower temperatures in comparison to the bound counterparts. Thus, in high conversion processes where it may not have been practical to run bound multiple ex situ selectivated catalysts, the unbound catalysts of the present invention provide the skilled artisan a new alternative. By reference to high conversion processes, hydrocarbon conversion reactions at a conversion level of 35 wt. % or greater are contemplated. It is particularly contemplated that the present catalysts could be utilized in hydrocarbon conversion reactions up to 50 wt. % hydrocarbon conversion due to their lower operating temperature requirements. The ability to run these catalysts at such high conversion levels would allow their use as a possible substitute catalyst in the Tatoray process, which is widely utilized for toluene production.
According to an embodiment of the present method, a zeolite in unbound form is impregnated preferably at least twice, and more preferably between about two and about six times, with a selectivating agent. The selectivating agent comprises a compound or polymer containing a silicon. In order to facilitate a more controlled application of the selectivating agent, the selectivating agent can be dispersed in a liquid carrier, more particularly an aqueous or an organic liquid carrier.
In each phase of the selectivation treatment, the selectivating agent is deposited on the external surface of the catalyst by any suitable method. For example, a selectivating agent may be dissolved in a carrier, mixed with the catalyst, and then dried by evaporation or vacuum distillation. This method is termed xe2x80x9cimpregnationxe2x80x9d. The molecular sieve may be contacted with the silicon compound at a molecular sieve/silicon compound weight ratio of from about 100/1 to about 1/100.
The silicon compound employed may be in the form of a solution or an emulsion under the conditions of contact with a zeolite. It is believed that the deposited silicon compound extensively covers, and resides substantially exclusively on, the external surface of the molecular sieve. Examples of methods of depositing silicon on the surface of the zeolite are found in U.S. application Ser. No. 08/069,251, filed May 28, 1993, and in U.S. Pat. No. 5,403,800, which are incorporated by reference herein.
As was described above, the catalysts useful in the present invention are ex situ selectivated by multiple coatings with a selectivating agent, each coating followed by calcination and optional trim-selectivation with additional selectivating agent. The term xe2x80x9cpara-selectivating agentxe2x80x9d or xe2x80x9cselectivating agentxe2x80x9d is used herein to indicate substances which will increase the shape-selectivity of a catalytic molecular sieve to the desired levels in hydrocarbon conversion reactions, such as toluene disproportionation, while maintaining commercially acceptable levels of toluene to xylene conversion. Such substances include, for example, organic silicon compounds such as phenylmethyl silicone, dimethyl silicone, and blends thereof which have been found to be suitable.
Useful selectivating agents include siloxanes which can be characterized by the general formula:
where R1 is hydrogen, halogen, hydroxyl, alkyl, halogenated alkyl, aryl, halogenated aryl, aralkyl, halogenated aralkyl, alkaryl or halogenated alkaryl. The hydrocarbon substituents generally contain from 1 to 10 carbon atoms, preferably methyl, ethyl or phenyl groups. R2 is independently selected from the same group as R1, and n is an integer of at least 2 and generally in the range of 3 to 1000. The molecular weight of the silicone compound employed is generally between about 80 and about 20,000 and preferably within the approximate range of 150 to 10,000. Representative silicone compounds include dimethyl silicone, diethyl silicone, phenylmethyl silicone, methylhydrogen silicone, ethylhydrogen silicone, phenylhydrogen silicone, methylethyl silicone, phenylethyl-silicone, diphenyl silicone, methyltrifluoropropyl silicone, ethyltrifluoropropyl silicone, polydimethyl silicone, tetrachlorophenylmethyl silicone, tetrachlorophenylethyl silicone, tetrachlorophenylhydrogen silicone, tetrachlorophenylmethyl silicone, methylvinyl silicone and ethylvinyl silicone. The silicone compound need not be linear, but may be cyclic, for example, hexamethyl cyclotrisiloxane, octamethyl cyclotetrasiloxane, hexaphenyl cyclotrisiloxane and octaphenyl cyclotetrasiloxane. Mixtures of these compounds may also be used, as may silicones with other functional groups.
Preferred silicon-containing selectivating agents include dimethylphenylmethyl polysiloxane (e.g., Dow-550) and phenylmethyl polysiloxane (e.g., Dow-710). Dow-550 and Dow-710 are available from Dow Chemical Co., Midland, Mich.
Preferably, the kinetic diameter of the high efficiency, p-xylene selectivating agent is larger than the zeolite pore diameter, in order to avoid entry of the selectivating agent into the pore and any concomitant reduction in the internal activity of the catalyst.
Examples of suitable carriers for the selectivating silicon compound include linear, branched, and cyclic alkanes having five or more carbons. In the methods of the present invention it is preferred that the carrier be a linear, branched, or cyclic alkane having a boiling point greater than about 70xc2x0 C., and most preferably containing 6 or more carbons, optionally, mixtures of low volatility organic compounds, such as hydrocracker recycle oil, may be employed as carriers. Particular low volatility hydrocarbon carriers of selectivating agents are decane and dodecane.
It has also been found that a multiple selectivation scheme provides unexpectedly increased efficiency of deposition of the silicon compound on the surface of the catalyst. This increased efficiency allows for the use of relatively small quantities of the silicon compound as well as relatively small quantities of the carrier. A more detailed discussion on the increased efficacy of depositing silicon compounds via multiple ex situ selectivation is described in U.S. Ser. No. 08/069,251 filed May 28, 1993, as well as in U.S. Pat. No. 5,403,800.
Following each deposition of the silicon compound, the catalyst is calcined to decompose the molecular or polymeric species to a solid state species. The catalyst may be calcined at a rate of from about 0.2xc2x0 C./minute to about 5xc2x0 C./minute to a temperature greater than 200xc2x0 C., but below a temperature at which the crystallinity of the zeolite is adversely affected. Generally, such temperature will be below 600xc2x0 C. Preferably the temperature of calcination is within the approximate range of 350xc2x0 C. to 550xc2x0 C. The product is maintained at the calcination temperature usually for 1 to 24 hours, preferably for between 2 and 6 hours.
The catalyst may be calcined in an atmosphere of N2, an oxygen-containing atmosphere, preferably air, an atmosphere of N2 followed by an oxygen-containing atmosphere, or an atmosphere containing a mixture of N2 and air. Calcination should be performed in an atmosphere substantially free of water vapor, to avoid undesirable uncontrolled steaming of the silicon coated catalyst. The catalyst may be calcined once or more than once after each silicon deposition. The various calcinations in any impregnation sequence need not be identical, but may vary with respect to the temperature, the rate of temperature rise, the atmosphere and the duration of calcination.
Factors upon which the amount of silica incorporated with the zeolite is dependent include temperature, concentration of the silicon compound in the containing medium (the carrier material), the degree to which the zeolite has been dried prior to contact with the silicon compound, and calcination of the zeolite.
After the selectivation sequence, the catalyst may be subjected to steam treatment at a temperature of from about 100xc2x0 C. to about 600xc2x0 C., preferably from about 175xc2x0 C. to about 325xc2x0 C.; with from about 1% to about 100% steam, preferably from about 50% to about 100% steam; at a pressure of from about 0.01 psia to about 50 psia; for about two to about twelve hours, preferably from about three to about six hours. The selectivated molecular sieve catalyst can show improved selectivity upon steaming. Excessive steaming, however, can be detrimental to a selectivated catalyst.
The alkylaromatic may be fed simultaneously with a second selectivating agent and hydrogen at reaction conditions until the desired shape-selectivity is attained, whereupon the co-feed of selectivating agent is discontinued. This co-feeding of selectivating agent with alkylaromatic is one type of xe2x80x9ctrim-selectivationxe2x80x9d. Reaction conditions for this in situ trim-selectivation step generally include a temperature of from about 350xc2x0 C. to about 540xc2x0 C. and a pressure of from about atmospheric to about 5000 psig. The reaction stream is fed to the system at a rate of from about 0.1 WHSV to about 20 WHSV. Hydrogen may be fed at a hydrogen to hydrocarbon molar ratio of from about 0.1 to about 20.
The selectivating agent for trim-selectivation may comprise a silicon compound discussed in greater detail above. For example, organic silicon compounds such as phenylmethyl silicone, dimethyl silicone, and mixtures thereof are suitable. According to one embodiment of the present invention, a silicone containing phenylmethylsilicone and dimethylsilicone groups in a ratio of about 1:1 is co-fed to the system, while the other components, e.g., alkylbenzene and hydrogen, are fed in the amounts set forth above. The para-selectivating agent is fed in an amount of from about 0.001 wt. % to about 10 wt. % of the alkylaromatic according to this preferred embodiment. Depending upon the percentage of selectivating agent used, the trim-selectivation will last for at least one hour, preferably about 1 to about 48 hours, most-preferably less than 24 hrs.
In this scheme the silicon compound will decompose to deposit additional silica to on the catalyst. During the selectivation procedure the para-selectivity of the catalyst will be observed to increase further. The silicon containing polymer or molecular species may be dissolved in toluene or another appropriate hydrocarbon carrier.
Alternatively, the catalyst, prior to contacting with alkylaromatic under conversion conditions, may be subjected to trim-selectivation with a thermally decomposable organic compound at an elevated temperature in excess of the decomposition temperature of said compound but below the temperature at which crystallinity of the zeolite is adversely affected. Generally, this temperature will be less than about 650xc2x0 C.
Organic materials, thermally decomposable under the above temperature conditions to provide coke trimming, encompass a wide variety of compounds including by way of example, hydrocarbons, such as paraffinic, cycloparaffinic, olefinic, cycloolefinic and aromatic; oxygen-containing organic compounds such as alcohols, aldehydes, ethers, ketones and phenols; heterocyclics such as furans, thiophenes, pyrroles and pyridines. Usually, it is contemplated that a thermally decomposable hydrocarbon, such as an alkyl-substituted aromatic, will be the source of coke, most preferably the alkylaromatic being subjected to the conversion process itself. In the latter case, the alkylaromatic is initially brought into contact with the catalyst under conditions of temperature and hydrogen concentration amenable to rapid coke formation. Typically, coke trimming is conducted at conditions outside the operating parameters used during the main time span of the catalytic cycle. When the desired coke deposition has been effected, the alkylaromatic feed is continued in contact with the coke-containing catalyst under conditions of temperature and hydrogen concentration conducive to hydrocarbon conversion process, with a greatly reduced coking rate. While not wishing to be bound by theory, it is believed that the advantages of the present invention are in part obtained by rendering acid sites on the external surfaces of the catalyst substantially inaccessible to reactants, while increasing catalyst tortuosity. Acid sites existing on the external surface of the catalyst are believed to isomerize the solution-phase para-isomer back to an equilibrium level with the other two isomers. In the case of xylene production, for example, the amount of p-xylene in the xylenes is reduced to about 24%, equilibrium selectivity. By reducing the availability of these acid sites to the solution-phase p-xylene, the relatively high proportion of p-xylene can be maintained. It is believed that the para-selectivating agents of the present invention block or otherwise render these external acid sites unavailable to the para-isomer by chemically modifying said sites.
The catalytic molecular sieves useful in accordance with the methods of the present invention are preferably in the hydrogen form prior to modification, but may be in the ammonium or sodium form. Preferably, the catalytic molecular sieve comprises an intermediate pore-size zeolite such as a ZSM-5, ZSM-11, ZSM-22, ZSM-23, or ZSM-35 as discussed above. The catalytic molecular sieves, prior to selectivation, also preferably have a Constraint Index of about 1-12. The details of the method by which Constraint Index is determined are described fully in U.S. Pat. No. 4,016,218, incorporated herein by reference.
As previously described, the catalytic molecular sieves useful herein have a Constraint Index from about 1 to about 12 which includes intermediate pore zeolites. Zeolites which conform to the specified values of constraint index for intermediate pore zeolites include ZSM-5, ZSM-11, ZSM-5/ZSM-11 intermediate, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, and ZSM-57. Such zeolites are described, for example, in U.S. Pat. Nos. 3,702,886 and Re. No. 29,949; 3,709,979; 3,832,449; 4,046,859; 4,556,447; 4,076,842; 4,016,245; 4,229,424; 4,397,827; 4,640,849; 4,046,685; 3,308,069 and Re. 28,341, to which reference is made for the details of these zeolites.
The crystal size of zeolites used herein is preferably greater than 0.1 micron, e.g., from 0.1 to 1 micron, e.g., from 0.1 to 0.5 micron. The accurate measurement of crystal size of zeolite materials is frequently very difficult. Microscopy methods, such SEM and TEM, are often used, but these methods require measurements on a large number of crystals and for each crystal measured, values may be required in up to three dimensions. For ZSM-5 materials described in the examples below, estimates were made of the effective average crystal size by measuring the rate of sorption of 2,2-dimethylbutane at 90xc2x0 C. and 60 torr hydrocarbon pressure. The crystal size is computed by applying the diffusion equation given by J. Crank, The Mathematics of Diffusion, Oxford at the Clarendon Press, 52-56 (1957), for the rate of sorbate uptake by a solid whose diffusion properties can be approximated by a plane sheet model. In addition, the diffusion constant of 2,2-dimethylbutane, D, under these conditions is taken to be 1.5xc3x9710xe2x88x924 cm2/sec. The relation between crystal size measured in microns, d, and diffusion time measured in minutes, t0.3, the time required for the uptake of 30% of capacity of hydrocarbon, is:
d=0.0704xc3x97t0.31/2.
In the present case these measurements have been made on a computer controlled, thermogravimetric electrobalance, but there are numerous ways one skilled in the art could obtain the data. The larger crystal material used herein has a sorption time, t0.3, of 497 minutes, which gives a calculated crystal size of 1.6 microns. The smaller crystal material has a sorption time of 7.8 minutes, and a calculated crystal size of 0.20 micron.
The xe2x80x9calpha valuexe2x80x9d of a catalyst is an approximate indication of the catalytic cracking activity of the catalyst compared to a standard catalyst, and it gives the relative rate constant (rate of normal hexane conversion per volume of catalyst per unit time). It is based on the activity of the amorphous silica-alumina cracking catalyst taken as an alpha of 1 (Rate Constant=0.016 sec1). The alpha test is described in U.S. Pat. No. 3,354,078 and in The Journal of Catalysis, 4, 522-529 (1965); 6, 278 (1966); and 61, 395 (1980), each incorporated herein by reference as to that description. It is noted that intrinsic rate constants for many acid-catalyzed reactions are proportional to the alpha value for a particular crystalline silicate catalyst (see xe2x80x9cThe Active Site of Acidic Aluminosilicate Catalysts,xe2x80x9d Nature, 309, No. 5959, 589-591 (1984). The experimental conditions of the test used herein include a constant temperature of 538xc2x0 C. and a variable flow rate as described in detail in the Journal of Catalysis, 61, 395 (1980). The catalyst in the present invention preferably has an alpha value greater than 1, for example, from about 1 to about 2000. The alpha value of the catalyst may be increased by initially treating the catalyst with nitric acid or by mild steaming before pre-selectivation. This type of steaming is discussed in U.S. Pat. No. 4,326,994.
The silica to alumina ratio of the catalysts of the invention may be determined by conventional analysis. This ratio is meant to represent, as closely as possible, the ratio in the rigid atomic framework of the zeolite crystal and to exclude aluminum in the binder or in cationic or other form within the channels. The silica to alumina molar ratio of the present zeolites may be less than 60, e.g., from 20 to 40.
The modified zeolite catalysts are advantageously used in the conversion of alkylbenzene compounds to provide dialkyl-substituted benzene products which are highly enriched in the para-dialkyl substituted benzene isomer. Examples of alkylbenzenes to be utilized include ethylbenzene and toluene, toluene being more preferred. Conversion reactions of this type include alkylation, transalkylation and disproportionation. Alkylations of reactions in which the catalysts of the invention can be used are described, for example, in U.S. Pat. Nos. 3,755,483, 4,086,287, 4,117,024 and 4,117,026, which are incorporated herein by reference.
As described in U.S. Pat. No. 3,755,483 to Burress, aromatic hydrocarbons such as benzenes, naphthalenes, anthracenes and substituted derivatives thereof, e.g., toluene and xylene, may be alkylated with alkylating agents such as olefins ethylene, propylene, dodecylene, and formaldehyde, alkyl halides, and alkyl alcohols with 1 to 24 carbons under vapor phase conditions including a reactor inlet temperature up to about 482xc2x0 C., with a reactor bed temperature up to about 566xc2x0 C., at a pressure of about atmospheric to about 3000 psia, a mole ratio of aromatic/alkylating agent of from about 1:1 to about 20:1, and a WHSV of 20 to 3000 over ZSM-12.
As described in U.S. Pat. No. 4,086,287 to Kaeding et al., monoalkylbenzenes having alkyls of 1-2 carbons, such as toluene and ethylbenzene, may be ethylated to produce a para-ethyl derivative, e.g., para-ethyltoluene at a temperature of from about 250xc2x0 C. to about 600xc2x0 C., a pressure of 0.1 atmospheres to 100 atmospheres, a weight hourly space velocity (WHSV) of 0.1 to 100, and a ratio of feed/ethylating agent of 1 to 10 over a catalyst having an acid activity, i.e., alpha, of 2 to 5000, modified by pre-coking or combining with oxides of phosphorus, boron or antimony to attain a catalyst with a xylene sorption capacity greater than 1 g/100 g of zeolite and an ortho xylene sorption time for 30% of said capacity of greater than 10 minutes, where sorption capacity and sorption time are measured at 120xc2x0 C. and a xylene pressure of 4.5xc2x10.8 mm of mercury.
U.S. Pat. No. 4,117,024 to Kaeding describes a process for the ethylation of toluene or ethylbenzene to produce p-ethyltoluene at a temperature of 350xc2x0 C. to 550xc2x0 C., a critical pressure of greater than one atmosphere and less than 400 psia, with hydrogen/ethylene ratio of 0.5 to 10 to reduce aging of the catalyst. The zeolite described in U.S. Pat. No. 4,117,024 has a crystal size greater than one micron, and is modified as the catalyst in U.S. Pat. No. 4,086,287 to attain the sorption capacity described in U.S. Pat. No. 4,086,287.
U.S. Pat. No. 4,117,026 to Haag and Olson describes the production of para-dialkyl benzenes having alkyls of 1 to 4 carbons under conditions which vary according to the feed. When the feed includes monoalkyl-substituted benzenes having an alkyl group of 1 to 4 carbons, olefins of 2 to 15 carbons, or paraffins of 3 to 60 carbons or mixtures thereof, conversion conditions include a temperature of 250xc2x0 C. to 750xc2x0 C., a pressure of 0.1 to 100 atmospheres and a WHSV of 0.1 to 2000. For the disproportionation of toluene, the conditions include a temperature of 400xc2x0 C. to 700xc2x0 C., a pressure of 1 to 100 atmospheres and a WHSV of 1-50. When the feed includes olefins of 2 to 15 carbons including cyclic olefins, the conversion conditions include a temperature of 300xc2x0 C. to 700xc2x0 C., a pressure of 1 to 100 atmospheres and a WHSV of 1 to 1000. When the feed includes paraffins of 3 to 60 carbons, conditions include a temperature of 300xc2x0 C. to 700xc2x0 C., a pressure of 1 to 100 atmospheres and a WHSV of 0.1 to 100. However for lower paraffins of 3 to 5 carbons, the temperature should be above 400xc2x0 C. When the feed includes mixed aromatics such as ethylbenzene and toluene, and also optionally olefins of 2 to 20 carbons or paraffins of 5 to 25 carbons, conversion conditions include a temperature of 250xc2x0 C. to 500xc2x0 C. and a pressure greater than 200 psia. In the absence of added aromatics, the olefins and higher paraffins are more reactive and require lower severity of operation, e.g., a temperature of 250xc2x0 C. to 600xc2x0 C., preferably 300xc2x0 C. to 550xc2x0 C.
In general, therefore, catalytic conversion conditions over a catalyst comprising the modified zeolite include a temperature of from about 100xc2x0 C. to about 760xc2x0 C., a pressure of from about 0.1 atmosphere (bar) to about 200 atmospheres (bar), a weight hourly space velocity of from about 0.08 to about 2000, and a hydrogen/organic, e.g., hydrocarbon compound, mole ratio of from 0 to about 100.
Alkyl-substituted benzenes, such as toluene and ethylbenzene, may be disproportionated over a multiply-selectivated catalyst. Normally a single pass conversion of an alkylbenzene stream results in a product stream which includes dialkylbenzenes having alkyl groups at all locations, i.e., o-, m-, and p-dialkylbenzenes. A catalyst treated in the manner described herein exhibits a desirable decreased ortho-dialkylbenzene sorption rate parameter and yields a significantly para-selected product from alkylbenzene disproportionation. For example, diffusion rate constants in toluene disproportionation have been discussed by D. H. Olson and W. O. Haag, xe2x80x9cStructure-Selectivity Relationship in Xylene Isomerization and Selective Toluene Disproportionationxe2x80x9d, Catalytic Materials: Relationship Between Structure and Reactivity, ACS Symposium Ser. No. 248 (1984).
In toluene disproportionation, toluene diffuses into the zeolite with a diffusivity Dt. The toluene undergoes disproportionation to p-, m-, and o-xylene and benzene at a total rate constant kD. For high selectivity and catalyst efficiency it is desirable to have       k    D                 less than  less than                         D          T                          r          2                      .
The degree of para-selectivity depends on the activity and the diffusion characteristics of the catalyst. The primary product will be rich in the para isomer if initially produced m- and o-xylene diffuse out of the zeolite crystal at a rate (Dm,o/r2) that is lower than that of their conversion to p-xylene (kI), as well as lower than that of the p-xylene diffusion (Dp/r2) out of the catalyst, where:
Dm=diffusion of m-xylene;
Do=diffusion of o-xylene;
Dp=diffusion of p-xylene;
r=length of diffusion path (crystal size);
kI=rate of interconversion via isomerization of xylene isomers yielding secondary xylene product m-xylene and o-xylene.
It is desirable to increase the para-selectivity of the catalyst. Practically, this involves decreasing the o- and m-xylene diffusivities such that       k    I     greater than                     D                  m          ,          o                            r        2              .
In such a case the rate of conversion of m- and o-xylenes to p-xylene exceeds the diffusivities of the m- and o-xylenes. As a result, the proportion of the xylene yield that is p-xylene will be increased. Those skilled in the art will appreciate that similar considerations apply to the diffusivities of other alkylbenzenes.
Near regioselective conversion of toluene to para-xylene may be achieved by disproportionating toluene in a reaction stream containing a toluene feed with a selectivated and optionally steamed catalytic molecular sieve in the presence of hydrogen and at reaction conditions suitable to provide p-xylene selectivity of greater than about 80%, even greater than 90%.
As will be apparent to one skilled in the art, with an increase in conversion comes a decrease in regioselectivity for the para-isomer. However, the decrease in regioselectivity will still remain above the equilibrium level for the para-isomer, in the case of para-xylene above 24 wt. % regioselectivity.
The production stream will also contain small amounts of o- and m-xylene and trace amounts of impurities such as ethylbenzene. The amount of these non-desired products will become greater as the conversion level of disproportionation reaction increases.
As used herein, the term xe2x80x9cpara-xylene selectivityxe2x80x9d means the proportion of p-xylene, indicated as a percentage, among all of the xylene products, i.e., p-xylene, o-xylene, and m-xylene. Those skilled in the art will appreciate that the relative proximity of the boiling points of these xylene isomers necessitates relatively expensive separation processes for the isolation of p-xylene. On the other hand, p-xylene is more readily separated from other components in the product stream such as benzene, toluene, and p-ethyltoluene.
As explained in greater detail herein, the presently modified catalyst may be used in a process for obtaining p-xylene at toluene conversions of at least 10%, preferably at least about 15-35%, with a p-xylene selectivity of greater than 80%, e.g., at least 85%. As stated previously, in high conversion processes where toluene conversion exceeds 35% the p-xylene selectivity will decrease but still remain above equilibrium levels, i.e., 24% para-selectivity. For example, one skilled in the art can expect that the para-selectivity to decrease to as low as 50% when toluene conversion levels are pushed to 45%-50%.
The present toluene disproportionation product may comprise at least 80 wt % of paraxylene, based on the total xylene isomers in the product, while at the same time producing at least 14.2 wt %, e.g., at least 14.5 wt %, of paraxylene, based on the total weight of hydrocarbons in the product.
The toluene feedstock preferably includes about 50% to 100% toluene, more preferably at least about 80% toluene. Other compounds such as benzene, xylenes, and trimethylbenzene may also be present in the toluene feedstock without adversely affecting the disproportionation product.
The toluene feedstock may also be dried, if desired, in a manner which will minimize moisture entering the reaction zone. Numerous methods known in the art are suitable for drying the toluene charge for the process of the invention. These methods include percolation through any suitable desiccant, for example, silica gel, activated alumina, molecular sieves or other suitable substances, or the use of liquid charge dryers.
Operating conditions employed in the process of the present invention will affect the para-selectivity and toluene conversion. Such conditions include the temperature, pressure, space velocity, molar ratio of the reactants, and the hydrogen to hydrocarbon mole ratio (H2/HC). It has also been observed that an increased space velocity (WHSV) can enhance the para-selectivity of the modified catalyst in alkylbenzene disproportionation reactions. This characteristic of the modified catalyst allows for substantially improved throughput when compared to current commercial practices. In addition, it has been observed that the disproportionation process may be performed using H2 as a diluent, thereby dramatically increasing the cycle length of the catalyst.
A selectivated catalytic molecular sieve may be contacted with a toluene feedstock under conditions for effecting vapor-phase disproportionation. Conditions effective for accomplishing the high para-selectivity and acceptable toluene disproportionation conversion levels include a reactor inlet temperature of from about 200xc2x0 C. to about 600xc2x0 C., preferably from 350xc2x0 C. to about 540xc2x0 C.; a pressure of from about atmospheric to about 5000 psia, preferably from about 100 to about 1000 psia; a WHSV of from about 0.1 to about 20, preferably from about 2 to about 10; and a H2/HC mole ratio of from about 0.1 to about 20, preferably from about 2 to about 6. This process may be conducted in either batch or fluid bed operation, with the attendant benefits of either operation readily obtainable. The effluent may be separated and distilled to remove the desired product, i.e., p-xylene, as well as other by-products. Alternatively, the C8 fraction may be subjected to further separation, as in the case of xylenes, subjected to crystallization or the PAREX process to yield p-xylene.
The catalyst may be further modified in order to reduce the amount of undesirable by-products, particularly ethylbenzene. The state of the art is such that the reactor effluent from standard toluene disproportionation typically contains about 0.5% ethylbenzene by-product. Upon distillation of the reaction products, the level of ethylbenzene in the C8 fraction often increases to between about 3% and 4%. This level of ethylbenzene is unacceptable for polymer grade p-xylene, since ethylbenzene in the p-xylene product, if not removed, degrades the quality of fibers ultimately produced from the p-xylene product. Consequently, ethylbenzene content of the p-xylene product must be kept low. The specification for the allowable amount of ethylbenzene in the p-xylene product has been determined by the industry to be less than 0.3%. Ethylbenzene can be substantially removed by crystallization,by selective sorption or by superfractionation processes.
In order to avoid the need for downstream ethylbenzene removal, the level of ethylbenzene by-product is advantageously reduced by incorporating a hydrogenation/dehydrogenation function within the catalyst, such as by addition of a metal compound such as platinum. While platinum is the preferred metal, other metals of Groups IB to VIII of the Periodic Table such as palladium, nickel, copper, cobalt, molybdenum, rhodium, ruthenium, silver, gold, mercury, osmium, iron, zinc, cadmium, and mixtures thereof, may be utilized. The metal may be added by cation exchange, in amounts of from about 0.001% to about 2%, typically about 0.5%. For example, a platinum modified catalyst can be prepared by first adding the catalyst to a solution of ammonium nitrate in order to convert the catalyst to the ammonium form. The catalyst is subsequently contacted with an aqueous solution of tetraamine platinum(II) nitrate or tetraamine platinum(II) chloride. The catalyst can then be filtered, washed with water and calcined at temperatures of from about 250xc2x0 C. to about 500xc2x0 C. It will be appreciated by those skilled in the art that similar considerations apply to processes involving alkylbenzenes other than toluene.

Binderless ex situ selectivated zeolite catalyst


The invention concerns an optical cable with continuous accessibility, comprising a closed protective sheath surrounding a cavity having in cross section two substantially perpendicular axes intersecting at the center of the cavity, and at least two optical fibers optionally organized in at least two modules and arranged such that they occupy the greater part of the cavity in the direction of the long axis but that they allow a clearance in the cavity in the direction of the shorter axis of the cavity.

The present invention relates to an optical cable (also called an optical fiber cable) with continuous accessibility, particularly suitable for local subscriber loops and for internal cabling, providing very simple accessibility at any location and thus providing a very low cost branch-off without having to use a branch connection box.
Many types of optical cables are known, making it possible to supply local networks or the cabling of buildings. In the majority of cases, these cables have a very dense structure. They comprise a relatively large number of fibers, and they are branched off using a branch connection box. It is by virtue of this branch connection box that after an often lengthy and tricky operation of removing the sheath from the cable over relatively great lengths, then of distributing the fibers, that it is possible to branch off one or more fibers. However, this operation is expensive and tricky. In addition, it is not without risk for the unbranched-off fibers which, in the majority of cases, are moreover high datarate carriers, that is to say ones having a large number of links transmitting voice, data or images. In addition, because of their architecture, these techniques are very often synonymous with distributed systems (for the cabling of buildings in particular), requiring the placement of numerous elementary cables, not to mention the presence of optoelectronic end devices. These distributed systems thus have the major drawback of leading to extremely high laying costs, which, for optical systems, generates a negative end result compared with the known copper systems.
To compensate for this major drawback, and to reduce the cost of installation, the majority of optical cable solutions developed to date tend toward cables which are as dense as possible, based on either stacks of ribbons, or on cylindrical modules of very small dimensions. Each ribbon or each cylindrical module may, for example, contain from 4 to 12 fibers, or even more. All of these ribbons or of these cylindrical modules are packed as closely as possible in a protective sheath possibly provided with reinforcements, according to the functional specifications of the cable. The sought-after aim is to obtain maximum density while retaining the appropriate mechanical and thermal properties for the optical cable.
The density thus obtained in the highest performance cables of the prior art allows them to be laid in microconduits, for example by blowing or pushing or pulling. However, these cables have the drawback of being quite difficult to access thereby making the tap-off operation, that is to say the branching-off of one module among n or of one fiber among n, expensive and tricky. They are therefore better suited to distributed techniques where the breakout made necessary takes place in a box designed to this end. In addition, the dense and cylindrical structure of the jacket of such cables requires an internal xe2x80x9ccablingxe2x80x9d of the optical elements (modules or optical fibers). This internal cabling is an assembly of optical elements with a given pitch either in a continuous helix (helical cabling), or in SZ (SZ cabling), so as to guarantee the integrity of the fibers when winding the cables.
Thus, in these known techniques, in order to operate correctly from the mechanical and thermal point of view and in order to comply with the radii of curvature, the relatively dense cable structures require xe2x80x9ccablingxe2x80x9d of this sort, which only increases the difficulty of access to the fibers and in particular makes it necessary for all the sheath to be removed over considerable lengths so as to allow the operator to handle the bundles with enough flexibility to access the sought-after module and, even more difficult, the sought-after fiber. In addition, cabling of this sort decreases the speed of cablemaking, and increases the costs. It can therefore be seen that, whatever their shape, oval, cylindrical, or other, none of these structures has been designed for continuous and easy accessibility of the fibers.
There is therefore a need for a cable designed to allow continuous and easy accessibility, therefore allowing easy branching, while remaining a very economical solution and installation system. Solving this problem is all the more significant since placing several cables in parallel, for example in order to supply several workstations inside a building, remains an expensive operation which places optical systems at a disadvantage with regard to copper.
A branchable optical cable is known, the principle of which is to place cable elements in a sheath or profile in the shape of a U open on one side, which may then be opened out right along the cable, at any location on the cable, and thus allow access to the cable elements. This cable was the subject matter of patent application FR 99 13271 filed by the applicant. However, a cable of this sort involves the special manufacture of cable elements and the use of a profile which may prove heavy and bulky and quite difficult to utilize, especially in terms of its storage on a cable drum, its laying and its accessibility.
The applicant has therefore developed an optical cable with continuous and easy accessibility, therefore making it possible to extract very easily from it, at any location, an optical element protecting one or more optical fibers, intended to supply a room or a region comprising several workstations. The cable developed by the applicant offers tensile strength and crush resistance properties which enable easy installation, for example in a conduit or in cable trays, in the latter case with an increased ability to follow localized curves and with a density which remains reasonable. Because of its structure, the cable which is subject of the invention also has excellent thermal behavior and can be wound with no problem on cable drums, without requiring cabling of the elementary optical elements inside the sheath.
The subject of the invention is therefore an optical cable with continuous accessibility, comprising a closed protective sheath surrounding a cavity having in cross section two substantially perpendicular axes intersecting at the center of the cavity, and at least two optical fibers arranged such that they occupy the greater part of the cavity along one axis but that they allow a sizeable clearance along the other axis of the cavity. The optical fibers can be organized into at least two optical elements (also called optical modules). The optical fibers, or optical modules, therefore form a sort of sheet, which is relatively loose or not depending on the number of fibers or modules. This arrangement of the cable according to the invention does not exclude some superposition of the fibers or of the modules within the sheet. Preferably, one of the axes is longer than the other axis. The optical elements are preferably positioned along this long axis, and therefore the clearance is left in the short axis. The clearance left in one of the axes is considerable with respect to the usual clearance of a dense optical cable structure, which is generally reduced to the strict minimum. This clearance therefore allows variations, called overlength, of the order of one percent or of a few percent (overlengths considered in per thousand in dense structures). Moreover, the sheet of fibers or of modules may move by translation in the cavity while remaining on the same axis (on the long axis in the case of an ovalized cavity).
The cavity has any shape, for example circular or oval or ovalized (that is to say between an oval and a rectangle), preferably ovalized. The sheath has any external shape, for example circular or oval or ovalized, preferably ovalized. In a particularly preferred embodiment, sheath and cavity are of ovalized shape, and their long axes are coincident.
In some embodiments, the sheath may comprise one or more mechanical reinforcing members, preferably positioned on either side of the cavity, again preferably along the long axis. These reinforcing members will preferably be of the nonmetallic glass-epoxy type, but may also be metallic. In an application of cable run type and over relatively short lengths, these reinforcing members may prove not to be indispensable making the production of the cable even more economical.
Thus, contrary to the teaching of the prior art, which encourages the perpetual search for an ever increasing density, the density of the cable which is the subject of the invention is deliberately less than the density that could be reached if the cavity was full. However, a cable of this type retains enough density to be used simply in installations of the conduit or cable-tray type, while offering some clearance in the cavity, facilitating the accessibility of the optical elements therefore of the optical fibers, and this by means of an optimized filling, a compromise between maximum filling and too low a density.
The preferably ovalized external shape of the cable according to the invention, together with the possible reinforcing members, confer on said cable a curving behavior which favors the long axis of the sheath preferably coincident with the long axis of the cavity, and therefore ensures winding along this long axis taking advantage of the considerable clearance in the short axis. This makes it possible to avoid xe2x80x9ccablingxe2x80x9d of the optical elements, which may therefore be placed lengthwise without twisting. This also offers some flexibility to the cable, in spite of its dimensions, which makes it possible to apply the cable easily to the curves, which are sometimes severe, of the cable trays. Moreover, the cable obtained has very good thermal and mechanical behavior while offering very simple accessibility by localized opening parallel to the long axis and visibility of the possibly colored optical cable elements laid lengthwise in the cavity. The curvature favored along the long axis of the external ovalized part and the reasonable density of the cable also make easy storage of significant lengths possible on a drum before laying and facilitate installation, and especially the curvatures required by laying in cable trays.
Thus, the cable which is the subject of the invention advantageously contains very dense optical modules, for example made from fibers surrounded with a thin film in order to form elementary modules which may range, for example, from two to twelve fibers depending on the intended application. Within one and the same cable, it is possible to mix modules (for example 12) of different capacities. Moreover, such elements are perfectly known and mastered in order to bring together fibers (conventionally of 250 xcexcm diameter) in a minimum space with very simple accessibility given the ease of baring or stripping the thin film. These modules are modules used in cablemaking and therefore belong to known techniques for producing highly compact cables. These elements are thus placed lengthwise in the cavity of the cable which is the subject of the invention. The considerable clearance encountered by these elements along an axis, preferably the short axis, of the cavity makes it possible to achieve very high cabling rates and therefore to produce a cable quickly and very economically. They have a low coefficient of friction which makes it possible to extract them from a row of modules without any difficulty, that is to say without a force detrimental to the behavior or to the strength of the fibers, including over lengths which may reach several meters.
The protective sheath of the cable according to the invention and its cavity have dimensions suitable for the use envisioned. By way of example, the dimensions of the sheath may be from 10 to 15 mm for the long axis and from 6 to 8 mm for the short axis (for an ovalized sheath). By way of example also, the dimensions of the cavity may be from to 5 to 9 mm for the long axis and from 2 to 4 mm for the short axis. The optical elements or modules positioned in the cavity may have a diameter or a longer dimension in section of about 0.8 mm to 1.3 mm.
The optical elements therefore have a certain degree of freedom within the cavity, making it possible to remove stresses on these elementary modules, whether this is after an extension of the sheath under a certain tension or under the effect of an expansion, or after a contraction due to low temperatures.
For this, the cablemaking process, well known moreover in the field of cablemaking, provides, when making the protective sheath and inserting fibers, an initial overlength which is small but sufficient for there to be no actual stresses when the cable is under tension or expanding.
This high degree of freedom along one axis of the cavity allows the optical modules (or fibers) to spread out flat along the other axis of the cavity, and offers, as specified above, two considerable advantages. On the one hand, the possibility of lengthwise cabling of the modules, leading to a very simple process, allows high and very economical production rates. On the other hand, the xe2x80x9csheetxe2x80x9d of modules (or fibers) is easily accessible both because of the visibility of the modules and because of the considerable clearance of these same modules in the cavity making them extremely easy to extract including over great lengths. The branching-off of a module (or of a fiber) is carried out without stresses that could damage the module itself (or the fiber), and without an interaction that could damage the nearby modules (or fibers), which is essential for high datarate links and for interventions which may take place while some fibers or some modules are already in service.
The material used for making the sheath is preferably inexpensive, and makes it possible to obtain small radii of curvature, smaller radii of curvature being made possible the greater the lateral clearance of the modules in the cavity, and effective protection of the cable especially against shocks and crushing.
A suitable material may be chosen among elastomers of the natural rubber type, styrene/butylene/styrene and styrene/ethylene-butylene/styrene copolymers, flexible formulations from the elastomeric range, composed of polymers such as ethylene/methyl acrylate, ethylene/ethyl acrylate and ethylene/butyl acrylate copolymers, and ethylene/vinyl acetate copolymers, these polymers possibly being combined with flame-retardant fillers and antioxidant additives; copolymers of the polyesterether type such as the ARNITEL(copyright) copolymer manufactured by DSM or the HYTREL(copyright) copolymer manufactured by DuPont de Nemours. Preferably, it will be one or more halogen-free flame-retarded polyolefins, of the type commonly used in sheathing cables placed in a building. For external use, it is possible to envision producing a cable with a cavity accommodating the modules, surrounded with a sheath made, for example, of PVC, coated with a medium or high density polyethylene-type jacket more suited to pulling techniques in a conduit and comprising reinforcing members.
In one embodiment, the sheath may have one or more colored threads, obtained for example by coextrusion. The role of these threads is to indicate the regions where the windows can be drilled and, also, to identify the optical cable while giving it an attractive appearance. The windows may be opened on either side of the sheet of fibers or modules. The presence of these colored threads thereby facilitates the opening by the installer.
In another embodiment, the sheath may have one or more fracture initiators marked to a greater or lesser a degree and possibly colored, for example in the hollow of the initiator, possibly in combination with one or more colored threads. Such initiators further facilitate the opening of the windows. However, they tend to embrittle the structure of the cable. An embodiment of this sort is therefore better suited to cables subject to few stresses, for example in the case of buildings with cables laid on a cable tray.
In another embodiment, the sheath has a region of lower thickness, between two guides, so as to facilitate the opening of windows at this lower thickness region.
In the case of cables subject to considerable stresses, for example those placed by pulling, blowing or pushing in a conduit and on an external site, it will be preferred to use a cable comprising, in addition to the usual sheath, an additional external jacket.
In this case, the external jacket may comprise one or more colored threads, and/or one or more fracture initiators, and/or one region of lower thickness. This jacket may also contain reinforcing members. The material of this jacket may be of the medium- or high-density polyethylene type. The sheath and the jacket may be manufactured by coextrusion or, more easily, by successive extrusion of the sheath, for example made of PVC, then of the jacket.
When installing a cable according to the invention, it is therefore seen that it is possible to access, in a continuous manner, that is to say at any point on the cable and at any time, in an extremely simple manner, the optical modules or elements present in the cable.
For example, it is possible to open part of the cable along the long axis over a very short length, and to remove part of the sheath using a tool specially adapted to the shape and to the dimensions of the cable, thereby producing in this way a first window for access to the location intended for the branching-off. Because of its shape, the cable acts as a guide for the tool, which may comprise for example one or two cutting blades. The opening is without risk for the modules or the fibers because of their clearance in the cavity. It is possible to repeat the operation downstream, at a distance from the first window chosen according to the desired branching length, a length which may range, for example, from a few tens of centimeters to several meters, and thus to form a second access window. This is then enough to access the module chosen in the second window, to cut it, then to extract it through the first window, that is to say the window chosen for the branching.
An extraction of this sort is made possible and easy by virtue of the clearance of the modules or of the fibers in the cavity, by virtue of the low coefficient of friction of the material forming their sheath or film, and finally by virtue of the fact that the modules or fibers are laid lengthwise therefore without cabling. Moreover, the windows may be opened only over short lengths, typically a few centimeters.
After the branching, it is possible to close the windows again by attaching (for example by adhesive bonding) a lid which acts as a patch and makes it possible to establish better protection of the modules or fibers inside the cable, a cable which has retained its mechanical properties throughout the branching operation. Moreover, it is possible to place the branched-off fiber or module inside a corrugated sheath of suitable dimensions or any type of prerouted sheath depending on the envisioned use, without having to use intermediate splicings.
Of course, in certain applications, it is possible to envision cables of smaller dimensions with less fiber capacity, by placing possibly colored optical fibers directly in the cavity rather than modules. If modules are used, it is seen that there are many possibilities depending on the aims of the cabling project, each elementary module possibly comprising 2, 4, 6, 8 or 12 fibers for example, offering cable capacities ranging for example from 24 to 96 fibers or even more, depending on the number of modules.
According to the chosen technique, it will be preferred to work with low-capacity modules in order to serve only a single office for example, or it will be preferred to work with higher capacity modules so as to serve a dense region consisting of four, eight or twelve offices or one office containing several workstations.
It is therefore seen that the cable which is the subject of the invention may meet the needs of many engineering choices while retaining its intrinsic qualities of continuous accessibility and of considerable saving on the installation costs.
Of course, this principle of a cable with continuous accessibility is based on the fact that the cost of optical fibers has substantially decreased in the light of decisive productivity steps in modern production processes, and that the technique of continuous branching assumes, except when assuming looping of the links, that the parts of the fibers downstream of the branch are lost for the use in question. On the other hand, it is possible to use these fibers subsequently either to loop a link or to create intermediate links. The fact of losing lengths of fibers proves in any case to be markedly more economical, particularly when using monomode fibers, than laying series of short cables and producing a structure of the distributed type.
The fast and substantial increase of datarates for multimedia-type applications moreover strongly favors the direct use of monomode fibers, including in the vertical and horizontal parts of business cabling, provided that very bottom of the range and very low cost optoelectronic modules are attached for such use. The cable which is the subject of the invention therefore opens a new way of cabling a building or of cabling small town networks, loops etc., which is very economical and very flexible to use, making it possible to envision competitive optical solutions with respect to the successive solutions using copper media, while offering the user a medium capable of accepting considerable datarates.

Acome (Societe Cooperative de Travailleurs)


A driveline assembly includes a shaft that is rotatably supported on a bearing assembly within a drive axle. The shaft has a first mount portion with a threaded exterior surface and a second mount portion with a splined exterior surface. A retaining ring is threaded onto the first mount portion to engage and retain the bearing assembly at a proper location. A yoke member with a splined inner bored is mounted on the shaft in engagement with the splined exterior surface. The yoke member can easily be connected and disconnected from the shaft without having to remove the retaining ring. The yoke member also includes a quick disconnect device that simplifies removal and re-assembly of the yoke member from the shaft.

This invention relates to a quick connect/disconnect driveline assembly for facilitating service, repair, and change-out operations that occur over the life of the driveline. Specifically, the invention includes a retaining ring for engaging and retaining a bearing at a proper location on a shaft while allowing a yoke member to be separately mounted on the shaft. The yoke member can be connected and disconnected without having to remove the retaining ring.
Most vehicle drivelines include drive axles that are connected to a driveshaft or other driveline component with a universal joint. The drive axle can be either a single drive axle coupled to the driveshaft or a tandem axle assembly including a forward-rear axle that is coupled to the driveshaft and a rear-rear axle that is connected to the forward-rear axle via an interaxle driveshaft. Universal joints provide connections between the axles and the driveshafts.
The universal joint allows two shaft components to be oriented at different angles relative to each other to accommodate relative movement and angular misalignment while transmitting torque. The universal joint connections are used to interconnect driveline components that are not mounted to the vehicle in a straight line.
For example, the driveshaft powered by a vehicle engine provides input, via a transmission, to a center gear assembly of the single drive axle. The center differential has an input pinion shaft that is coupled to the driveshaft with a universal joint assembly. In another example, the driveshaft provides input to the tandem axle having the forward-rear axle connected to the rear-rear axle with the interaxle driveshaft. The forward-rear axle has an input pinion shaft coupled to the driveshaft and an output thru-shaft coupled to the interaxle driveshaft. The rear-rear axle has an input pinion shaft that is coupled to the interaxle driveshaft. Universal joint assemblies connect both axles to the interaxle driveshaft as well as connecting the driveshaft to the input pinion shaft of the forward-rear axle.
The universal joints typically include a pair of yoke members. One yoke member is supported on a shaft (i.e., the input pinion shaft and/or the output thru-shaft) operably connected to one of the axles and the mating yoke member is supported on the driveshaft or interaxle driveshaft. Bearing assemblies are mounted within the axles to rotatably support the input pinion shafts and the output thru-shaft. Typically the yoke members, which are supported on the input pinion shafts and the output thru-shafts, have a hub portion that slides over the shaft abuts against the bearing assembly. A nut is then threaded on the shaft and tightened to hold the yoke member securely against the bearing assembly.
In some applications, the nut is tightened to hold the yoke member securely against the bearing assembly to properly retain and position the bearing assembly on the appropriate shaft. In a tandem axle configuration, the yoke members are installed on the output thru-shaft and the input pinion shaft to the rear-rear axle and the respective nuts are tightened against the yoke members to retain the bearings. The interaxle driveshaft is then installed between the forward-rear axle and the rear-rear axle. The interaxle driveshaft is a two-piece telescoping shaft that is collapsed to a shorter length, inserted between the axles and then expanded to the desired length for attachment to the yoke members on the thru-shaft and input pinion shaft to the rear-rear axle. This installation processes is difficult and time consuming. Thus, it would be desirable to simplify the installation process of the yoke members on the shafts and the connection of the axles to the interaxle driveshaft.
In other applications, the nut is tightened to a predetermined torque level to provide a preload force for the bearing assembly. Sometimes, a preload force is required for the bearing assembly to operate and wear properly. This configuration is susceptible to having inconsistent torque applied to the nut due to the necessity of removing and reinstalling the yoke member for service. In other words, once a yoke member is removed for service, the preload force needs to be re-applied to the bearing assembly. When the yoke member is re-installed, the nut can be over or under-tightened resulting in an improper bearing preload force, which can lead to diminished performance, increased noise, accelerated wear, and pre-mature failure. This situation can occur when the yoke members are removed for repair, replacement, and/or when the yokes members are changed-out to accommodate greater or lesser load carrying capacities. Further, the process of removing and re-installing the yoke members and associated retaining nuts is time consuming.
For the above reasons, it would be desirable to simplify the assembly process for connecting and disconnecting yoke members and to eliminate the need to re-apply bearing preload forces after driveline service to avoid premature wear and failure in addition to overcoming other deficiencies in the prior art as outlined above.
A driveline assembly includes a first shaft that is supported on a bearing assembly for rotation within a drive axle. The shaft includes a first mounting portion and a second mounting portion. A retaining ring is installed on the first mounting portion to engage and retain the bearing assembly at a proper position along the shaft. A yoke member is installed on the second mounting portion for connecting the first shaft to a second shaft. To simplify service and assembly, the yoke member can be removed without having to remove the retaining ring from the shaft. Additionally, the yoke member can be re-installed without affecting the retaining ring.
In the preferred embodiment, the first mounting portion comprises a threaded surface on one portion of the shaft and the second mounting portion comprises a splined surface on another portion of the shaft. The retaining ring includes a threaded inner bore that installed in threaded engagement with the threaded surface on the shaft. The yoke member includes a splined inner bore that mates with the splined surface on the shaft.
Preferably, the yoke member includes a quick connect/disconnect device that permits the yoke member to be easily removed for repair, replacement, or change-out. The device includes components that are easily directed between connect and disconnect conditions. In one embodiment, the device includes at least one longitudinally extending slot formed in the body of the yoke member and at least one laterally extending thru-hole. To connect the yoke member to the shaft a clamping member is inserted into the thru-hole and applies a clamping force on opposing edges of the slot to clamp the yoke member to the shaft. To disconnect the yoke member, the clamping force is released.
In another embodiment, the device includes a laterally extending hole in communication, through a small opening, with the splined inner bore of the yoke member. To connect the yoke member to the shaft, a spring loaded pin is biased to engage an edge of the small opening to retain the yoke member on the shaft. To disconnect the yoke member, the spring loaded pin is depressed to disengage the edge of the small opening to permit removal of the yoke member from the shaft.
In some applications, the retaining ring is tightened against the bearing assembly to a predetermined torque level to achieve a predetermined bearing preload. The yoke member is then installed on the shaft. The yoke member is removable from the shaft without having to remove the retaining ring. Thus, the bearing preload force is not affected during driveline maintenance.
The drive axle can be a single drive axle or a tandem drive axle assembly. In the single drive axle configuration, the shaft that supports the retaining ring and yoke member is an input pinion shaft. The pinion shaft supports a pinion gear that is in driving engagement with a center gear assembly in the drive axle. The retaining ring is positioned on the pinion shaft between the yoke member and the pinion gear.
In the tandem drive axle assembly configuration, the assembly includes a forward-rear axle and a rear-rear axle that are interconnected via an interaxle driveshaft. The shaft that supports the retaining ring and yoke member is preferably an output thru-shaft from the forward-rear axle. The thru-shaft is driven by a center gear assembly of the forward-rear axle and is coupled to the interaxle driveshaft. Optionally, or in addition to, the input pinion shaft to the rear-rear axle can also include a yoke member and retaining ring as described above in reference to the single drive axle.
In the preferred embodiment for the tandem axle configuration, the interaxle driveshaft is fixed in length. The yoke member is splined to the thru-shaft of the forward rear axle, as described above, for sliding adjustment along the thru-shaft. Preferably, the interaxle driveshaft is a single piece component that is used in combination with the sliding yoke member to provide variable length adjustment on the thru-shaft.
The subject invention simplifies assembly of driveline components in addition to improving performance. These and other features of the present invention can be best understood from the following specifications and drawings, the following of which is a brief description.

Quick connect/disconnect driveline assembly


The line jammer device is a device for jamming a line which is under tension upstream of the device when it is in a locked state and releasing the line when it is in an unlocked state. The device has a first line gripping member and a second line gripping member. The first line gripping member has a circular surface around which the line is wound between a fraction of a turn corresponding to an angle of more than 180xc2x0 and at least one turn. The second line gripping member is arranged in such a way that the grip it exerts on the line is exerted once the line has been wrapped around the first gripping member between a fraction of a turn corresponding to an angle of at least 180xc2x0 and at least one turn.

The present invention relates to a line jammer device for, in a locked state, jamming a line which is under tension upstream of the device and, in an unlocked state, releasing this line.
The term xe2x80x9cupstreamxe2x80x9d defines that end of the line which is connected to the object that has to be tensioned using this line, and the term xe2x80x9cdownstreamxe2x80x9d defines the opposite end.
This device is intended in particular to be used on pleasure sailing boats, to jam various lines involved in the rigging of these boats, particularly the halyards, but this application is not restrictive. The term xe2x80x9cupstreamxe2x80x9d then, in the case of a halyard, defines that end of the line that is connected to the sail, and the term xe2x80x9cdownstreamxe2x80x9d defines the end via which the halyard is intended to be manipulated using a capstan.
Such line jammer devices are known in principle and are in widespread use on sailing boats.
An existing device, generally known by the name of a jamming cleat, comprises two pivoting cams, returned so that they pivot toward one another, and each having a curved lateral portion on its side that faces the other cam. The line is engaged between these cams, against the return force exerted on them, and the tension it experiences upstream causes the cams to pivot in the direction that causes the line to be gripped by these cams.
A device of this type exhibits a number of drawbacks, particularly as regards its limited ability to withstand high tension, the difficulty in releasing the line when such tension is exerted, the need to reinsert the line between the cams after each release, and the not insignificant amount of wear that the grip of the cams causes to the line.
These drawbacks appreciably restrict the use of these devices.
Another type of device, generally known by the name of a cam cleat, comprises a mount through which the line passes, and a cam with an eccentric which can move in terms of pivoting in this mount. The cam can be moved between a locked position in which it grips the line between it and the bottom of the mount, and an unlocked position in which it is located some distance from the line and therefore does not impede the free running of this line through the device.
This type of device is stronger than the jamming cleats described hereinabove, but retains many of their drawbacks. In particular, the cam may become very difficult, if not impossible, to manipulate if high tension is exerted on the line, as this entails exerting tension on this line downstream of the device to balance the tension upstream and thus allow the line to be released. Exerting this downstream tension entails an additional manipulation, preventing quick release of this line in certain emergency situations. Furthermore, the wear generated on the line by this type of device is high and the grip produced is not very effective on certain high-strength fibers, the coefficient of friction of which is low.
A third type of existing device comprises a mount containing a series of platelets, these platelets being inclinable and pierced with holes. The line is engaged through these holes and the tension it experiences causes the platelets to incline. This inclination allows the platelets to press firmly against the line, which jams the latter.
This type of device slightly reduces the amount of line wear but does not overcome the aforementioned drawbacks.
There is also known, from documents DE 1 231 and FR 2 753 169, a line jammer device comprising a first line-gripping member and a second line-gripping member between which this line is engaged. Said first gripping member is mounted so that it can pivot with respect to the device and comprises a circular surface around which the line can be engaged, and said second gripping member is arranged with respect to said first gripping member in such a way as to allow said line to be gripped between it and said first gripping member. At least one of these members can move between a locked position in which it grips the line between it and the other member, and an unlocked position in which it does not exert said gripping effort, so as to allow the line to run through the device.
These devices retain the aforementioned drawbacks relating to the difficulty of releasing the line in the event of high tension, to the not insignificant wear generated on the line and to the lack of gripping efficiency with certain lines.
The present invention sets out specifically to overcome these fundamental drawbacks of devices of this type by providing a line jammer device which allows both easy and quick release of the line in all circumstances, without the need to exert tension on the line downstream of the device, perfect jamming of a line made of fibers with a low coefficient of friction, and low line wear.
The device to which the invention relates comprises a first line-gripping member and a second line-gripping member like those disclosed in the aforementioned documents DE 1 231 and FR 2 753 169.
According to the invention,
the device is shaped in such a way that the line can be wound around said first gripping member over a fraction of a turn corresponding to an angle of more than 180xc2x0, or over a number of turns, and
said second gripping member is arranged with respect to said first gripping member in such a way that the grip it exerts on the line is exerted once the line has been wrapped around said first gripping member by a fraction of a turn corresponding to an angle of at least 180xc2x0, or once the line has been wound around said first gripping member over a number of turns.
Winding the line around said first gripping member makes it possible to greatly reduce the residual tension experienced by the line at the second gripping member. The grip exerted by the latter can therefore be reduced accordingly, thus limiting the wear generated on the line and the forces experienced by said members in this gripping. What this means is that manipulating the mobile gripping member or members with a view to releasing the line is easy, thus eliminating the need to tension the line downstream of the device to facilitate or achieve this release. Furthermore, winding the line in the aforementioned way gives a broad contact area between this line and said first gripping member, thus generating significant amounts of friction which increase with the tension exerted on the line. This friction combines with the gripping of the line to allow the latter to be jammed perfectly even when it is made of fibers which have a low coefficient of friction.
According to one simple embodiment of the invention, the mobile gripping member or members may be movable only by manually operated manipulating means, for example using a lever. According to a preferred embodiment of this invention, the device at the same time comprises:
manually operated manipulating means for bringing the mobile gripping member or members into their unlocked position, these manipulating means allowing the line to be released so that it can run; and
means allowing the mobile gripping member or members to be moved automatically into said locked position when the tension upstream is greater than the tension downstream and allowing these same members to be moved automatically into said unlocked position when the downstream tension is at least equal to the upstream tension.
A device such as this prevents any risk of uncontrolled release of the line while it is being manipulated.
According to one possibility, in this case of automatic movement, the second gripping member can move and consists of a pivoting cam, it being possible for this pivoting cam to pivot in one direction to engage with the line, when the tension upstream is greater than the tension downstream, and to pivot in the opposite direction to release the line when the tension exerted downstream is at least equal to the tension exerted upstream.
According to another possibility in this same instance, said first gripping member can be moved toward the second gripping member when the tension upstream is greater than the tension downstream, and can be moved in the direction away from this second gripping member when the tension exerted downstream is at least equal to the tension exerted upstream.
The first gripping member may be a transverse cylinder or may consist of a drum mounted so that it can rotate on a spindle. In this second instance, the line is made to run more easily through the device by the rotation of the drum, this allowing a quick action for releasing the line.
As a preference, in this case, the device comprises releasable means for preventing the drum from rotating in the direction that corresponds to the exerting of a tension upstream that is greater than the tension downstream; these means may in particular consist of a ratchet system connected to the device and of corresponding teeth formed on the drum.
Advantageously, in this case, the device comprises manually operated manipulating means designed to allow the following:
when the device is in a locked position, the line to be jammed if the tension upstream is greater than the tension downstream,
when the device is in an intermediate unlocked position, said second gripping member to be moved into its unlocked position while at the same time keeping said releasable means for preventing the drum from rotating in an active position, in which they prevent this rotation, and
when the device is in a fully unlocked position, the second gripping member to be kept in its unlocked position and said releasable means for preventing the drum from rotating to be moved into an inactive position, in which they allow this rotation.
In said intermediate unlocked position, the line can slip around the drum without the drum rotating, and therefore with friction, this corresponding to controlled release of the line. In said fully unlocked position, the drum is free to rotate so that this drum is made to turn by the running of the line, which corresponds to quick release of this line.
According to an improved embodiment of the invention, the second gripping member comprises, some way away from its gripping zone intended to come into contact with the line, a first cylindrical part, parallel to the axis of the drum, forming said ratchet and, on the same side as this gripping zone, a second cylindrical part, also parallel to said axis; this second cylindrical part is engaged, with the possibility of pivoting and of sliding, in a slot; this slot is oriented in such a way that the movement of said second cylindrical part within it causes the second gripping member to pivot about the axis of said first cylindrical part into its locked position when this second gripping member is moved in a curve by the drum via said first cylindrical part engaging with one of the teeth of the drum following the exerting on the upstream part of the line of a tension that is greater than the tension downstream.
The ratchet is thus formed directly on the second gripping member, and said slot allows this second gripping member to move slightly in a curve when the tension upstream greater than the tension downstream causes the drum to rotate. This curved movement, because of the orientation of the slot, allows the second gripping member to be moved toward this drum, until the line is gripped.
According to a further improved implementation of this embodiment of the invention:
the device comprises a mount on which a lever is mounted so that it can pivot, this lever being able to move between a locked position, an intermediate unlocked position and a fully unlocked position corresponding to the aforementioned locked, intermediate unlocked, and fully unlocked positions of the device;
said slot is formed in this lever and allows said second gripping member to move when the lever is placed in said locked position, whereas it is distant from the drum when the lever is pivoted into said intermediate unlocked position;
the mount of the device comprises a cam surface against which said second cylindrical part bears as the lever is pivoted into the intermediate unlocked position; this cam surface has a curved shape and said second cylindrical part collaborates with it in such a way as to cause the second gripping member to pivot about the first cylindrical part while keeping this first cylindrical part in engagement with the corresponding tooth of the drum; and
the lever comprises a stud which bears against the second gripping member when this lever is moved into said fully unlocked position, so as to disengage said first cylindrical part from the corresponding tooth of the drum.
When the lever is in the locked position, the slot allows the second gripping member to move automatically as indicated hereinabove. The pivoting of the lever into said intermediate unlocked position allows this same slot to be moved away from the drum and therefore allows the second gripping member to be moved into its unlocked position; however, this movement occurs without the ratchet that said first cylindrical part forms disengaging from the corresponding tooth of the drum, because of the collaboration between said second cylindrical part and said cam surface. Pivoting the lever into the fully unlocked position disengages the ratchet from the tooth of the drum.
Advantageously, the first gripping member comprises ribs which project, radially outward, from its exterior peripheral face, these ribs making it possible to increase the friction between the line and this first gripping member.
The possibilities of the line slipping with respect to this first gripping member are thus reduced, which encourages control over the release of said line.
Advantageously, the second gripping member is formed of the assembly of two parts, one of which comprises said first and second cylindrical parts, and the other of which comprises said line gripping zone, means being provided for allowing one of these parts to be placed relative to the other in a number of longitudinal positions and for keeping these parts in a predetermined position.
The movement of one of these parts with respect to the other allows the position of said gripping zone to be adjusted along this second gripping member, and therefore allows this position to be adapted to suit the diameter of the line that is to be jammed, to obtain optimum gripping of this line.
As a preference, the hub of the drum comprises an axial cavity which has a non-circular profile and opens to the outside of the device, this cavity being able to accommodate means for allowing this drum to be rotated by hand so that the line can be fully or partially tensioned. These means may, in particular, comprise a ratchet system, such as a needle ratchet system and a winding handle, particularly a capstan handle.


The present disclosure provides methods for producing a vaccine composition containing a pathogen that is rendered noninfectious by exposure to hydrogen peroxide. The methods disclosed herein are suitable for the preparation of vaccines for a wide variety of pathogens, including viruses, bacteria and parasites. The disclosure also provides vaccine compositions (medicaments) containing a pathogen inactivated by exposure to hydrogen peroxide. Methods for eliciting an immune response in a subject by administering vaccine compositions containing a hydrogen peroxide inactivated pathogen are also provided.

Current methods used to inactivate living pathogens in vaccine production involve the use of chemical agents such as formaldehyde or betapropiolactone to chemically modify the genetic material of the pathogen. However, there is substantial evidence that both of these agents are human and animal carcinogens. For example, studies in rats exposed to formaldehyde by inhalation have shown that formaldehyde induces squamous-cell carcinoma of the nasal cavity. Additionally, formaldehyde has been shown to be genotoxic in vitro and in vivo. Both genotoxicity and cytotoxicity play an important role in the carcinogenicity of formaldehyde.
Although the concentration of formaldehyde in vaccines is typically low (below 0.02%), this represents up to 50-100 micrograms of formaldehyde per injected dose in many vaccines (for example, Anthrax vaccine produced by Bioport Corp. contains 100 microgram/ml formaldehyde as a preservative) and poses a potential hazard due to the number of vaccinations a person receives over the course of a lifetime. Particularly dangerous is the amount of formaldehyde that is injected into infants and small children during the course of multiple routine childhood vaccinations. While the amount of formaldehyde in each vaccine dose is low, the combined amount can become substantial.
Similarly, betapropiolactone, which is used in the inactivation of rabies virus, can produce an immune complex-reaction when combined with other components of the rabies vaccine. Additionally, it has been shown to produce squamous cell carcinomas, lymphomas and hepatomas in mice.
Thus, there is a need to develop a low cost, nontoxic alternative to formaldehyde and betapropiolactone for the inactivation of live pathogens, such as viruses, bacteria and parasites. The methods disclosed herein address this need, and provide substantial benefits not previously described in the art.

Inactivating pathogens with oxidizing agents for vaccine production