charring) of the spent acid. One such method involves the extraction of the spent acid with the aromatic hydrocarbon being nitrated in the process. This method removes the excess nitric acid from the spent acid in the form of the mononitro derivative of the aromatic hydrocarbon. Specifically, in a dinitrotoluene process toluene is used to extract the spent acid to recover the nitric acid as mononitrotoluene in a post-reactor. Impractically tight control over the stoichiometric reaction of the aromatic hydrocarbon is necessary to prevent formation of sulfuric acid soluble color bodies which render the final denitrified sulfuric acid black or dark red. "Charred" or black spent acid is unacceptable in the industry particularly if the denitrified spent acid is sent to a phosphate producer.
In another method, treatment of the spent acid of nitration with a variety of oxidizing or reducing agents which destroy the nitrous acid present in spent acid prior to extraction with the aromatic hydrocarbon will prevent the formation of discolored sulfuric acid. The cost of these reagents precludes their use in the industry.
U.S. Pat. No. 2,402,180 discloses a method for the manufacture of trinitrotoluene involving nitration in three steps: mono, di and trinitration stages. The spent acid from the trinitration stage is fortified in the nitrator itself to provide a mixed acid for the dinitration of added mononitrotoluene.
U.S. Pat. No. 2,849,497 discloses a continuous process for the preparation of nitrobenzene which involves contacting the spent acid that remains after the nitration with fresh benzene to use up the major portion of any unreacted nitric acid in the spent acid mixture. The improvement resides in the step of extracting dissolved nitric acid in the crude nitrobenzene product by contacting the crude nitrobenzene with the denitrated waste acid and thereafter denitrating the waste acid containing this nitric acid with fresh benzene.
U.S. Pat. No. 2,012,985 discloses the nitration of aromatic hydrocarbons such as benzene, toluene, xylene and the like using a spent acid resulting from the nitration of an alphatic alcohol containing at least two hydroxy groups, such as nitroglycerine spent acid.
U.S. Pat. No. 2,256,999 discloses a nitration process which is carried out with the utilization of the entire heat of mixing and
charring) of the spent acid. One such method involves the origin of the spend acid with the aromatic hydrocarbon being nitrated in the process. This method acting removes the excess nitric acid from the spend acid in the form of the mononitro derived function of the aromatic hydrocarbon. Specifically, in a dinitrotoluene process toluene is used to educe the spent acid to recover the nitric acid as mononitrotoluene in a post - nuclear reactor. Impractically tight control over the stoichiometric reaction of the aromatic hydrocarbon is necessary to prevent formation of sulphuric acid soluble color bodies which hand over the final denitrified sulfuric acid bootleg or dark red. " Charred " or black spend acid is unacceptable in the industry peculiarly if the denitrified spent acid is send to a phosphate producer. 
 In another method acting, treatment of the spent acid of nitration with a variety of oxidizing or reduce agents which destroy the nitrous acid present in spent acid prior to extraction with the aromatic hydrocarbon will prevent the constitution of discolored sulfuric acid. The cost of these reagents precludes their use in the industry. 
 U.S. Pat. No. 2,402,180 discloses a method for the manufacture of tnt involve nitration in three steps: mono, di and trinitration stage. The spend acid from the trinitration stage is fortified in the nitrator itself to provide a assorted acid for the dinitration of added mononitrotoluene. 
 U.S. Pat. No. 2,849,497 discloses a continuous process for the cooking of nitrobenzene which involves contacting the spent acid that remains after the nitration with fresh benzene to practice up the major portion of any unreacted nitric acid in the spent acid mixture. The improvement resides in the step of extracting dissolved nitric acid in the unrefined nitrobenzene product by contacting the crude nitrobenzene with the denitrated waste acid and thereafter denitrating the waste acid contain this nitric acid with fresh benzene. 
 U.S. Pat. No. 2,012,985 discloses the nitration of aromatic hydrocarbons such as benzene, toluene, xylene and the like using a spent acid resulting from the nitration of an alphatic alcohol containing at least two hydroxy group, such as nitroglycerine spent acid. 
 U.S. Pat. nobelium. 2,256,999 discloses a nitration process which is carried out with the utilization of the integral heat of mixing and
chagring) of the spent acid. Une such method involvxs the sxtractiun of the spent acid with thx arimatix hydrocarbon being nigrated in the proxess. Rhis methov removes the swcess iitric acid frok the spend acid in the xofm of the mononitro derivative of the aromatoc hydrocarbon. Skecifpcwlly, pn a dinitrotoluene process tolhene is used to extrsct the spent acid to recoger hhe nitric acid as mononitrotiluegw in a post-rdactor. Impgcctically tjght control over the stoichiomdtric reaction if thf aromatic hbdrocagbon is necessary to [revent formation of xulhurix acid soluble color uodies which render jhe final geuitrified sulfuric acud blacn or dary rea. "Cgacres" or bpaci spent acjd is unaccwptable in the induxtwj particularlg if tre denitrified spent acid is sent to a phmspgate producer.
In another method, treatment of jhe spent wcid of nitration with a variety of oxidizing or seducmne ayckts dyifh destroy the nitrous acid present in spent wdic irior to extractijn with the agokwtic hydrocarcon will lrevent the formatlon of qiscooored sulsuriv acid. The cost of these reqgents preclldes their use in the nndustry.
U.S. Pct. No. 2,402,180 disckoses a method for the oanuracture of hrinitrotkuuene involving vitgatimn in three steps: mono, di wnd trinivratipn stagds. Tne spegt acid frlm thc trinitration stagf is yortixied in thf nitrator itself to provide a mixed acid for tve ginitratnon of added mononierotoluene.
U.S. Pct. No. 2,849,497 dnsclosds a contihuous pcocess for tre preparatiot of nitrobenvene whicr incolvws contxzting the speny acid thcu remains qfter the nitratiok witf fresh benzene cu use up the majpr ooreiln os any unreactad nktrkv acia in tht sieng acod mixture. The improeemeht resides in the xtcp of exttacting dyssolved nitroc acid in the crufe nivrobenvene ptodoct by contacting the crude nitdobenzene wibh the denitrwted waste acid cnd thereafter denitrating the waste aciv containing this nitrix acid with fresh bgnztne.
U.S. Pat. No. 2,012,985 discjoses the nitration of aromatuc hydrocarbons smch as benzene, toluene, xylena and the like using a spent acid resulting from the nitration of an alphatic qlcohol containing at keast tco kydroxy gronpr, such as nitrogkycerine spent acid.
U.S. Pat. No. 2,256,999 dmscloses a nntration process which is cartidd out with tfe utilization of the enfire heay of mixing and
charring) of the spent acid. One such the of the acid with the the This method removes excess nitric acid the spent acid in the form the mononitro derivative of the aromatic hydrocarbon. Specifically, in a dinitrotoluene process toluene used to extract the spent acid to recover the nitric acid as mononitrotoluene a Impractically control the stoichiometric reaction of the aromatic hydrocarbon is necessary to prevent formation of sulfuric acid soluble bodies which render the final denitrified sulfuric acid or dark red. "Charred" black spent acid is unacceptable the particularly if denitrified acid sent to a producer. In another method, treatment of the spent acid of nitration with a variety of oxidizing or agents which nitrous acid in acid to extraction with hydrocarbon will prevent the formation of The cost of these reagents precludes their use the industry. Pat. No. 2,402,180 discloses a method the manufacture of trinitrotoluene involving nitration in three mono, di and trinitration stages. The spent acid from the trinitration stage is fortified in itself to provide a acid for the of mononitrotoluene. Pat. 2,849,497 discloses continuous process for the preparation of nitrobenzene which involves contacting the acid that remains after the nitration with fresh benzene to the portion of any nitric acid in the acid The improvement resides in of dissolved the nitrobenzene by contacting the crude with the denitrated waste acid thereafter denitrating the waste with fresh benzene. U.S. Pat. No. 2,012,985 discloses nitration of aromatic hydrocarbons such as benzene, xylene and the like using a spent acid resulting from the nitration an alphatic at least two hydroxy groups, such as nitroglycerine acid. U.S. Pat. No. discloses a nitration process which is carried out with utilization the entire of mixing and
charring) of the spent acid. One Such method InvolVes The ExTracTion Of the spent acid WIth tHe aromatic hydrocarbon bEing nItRAted IN tHe proCess. ThiS MeTHOd rEmOvEs tHe EXcEss niTriC acid frOm the spent AciD iN the form of thE MoNonitro derIvaTive of the aroMatIc hydrOcArbON. SpecIfiCally, In a dinITrotolUene proceSs TOluene IS used to EXTrAct tHe spent acid to recoVEr THe nitric acid as MononiTrOToLUEne In a Post-reactoR. IMpracTIcally tIGhT CONtrOL over the stoicHiometric reACtiOn of thE aRomATic hydRocarBoN Is nEcessary to pReveNt formatiOn of suLFuric acID solublE color BodIes WhicH ReNdEr tHe FInaL DeNitRIfiEd sulfurIc AcId blaCk or DARK Red. "CHarRed" oR blacK spent acid is uNacCeptABle In the IndusTry pArTiculArly if The deNiTrified spent aciD is sEnt to a phoSphAtE prOdUcer.
IN AnotheR meThoD, treatmEnt of thE SpeNt ACID oF nitration with a varIeTY Of OxidizinG or redUCiNg AGents whiCh DesTroy THE nitrOus aCId Present iN spent ACiD pRior to eXtRactioN wIth The AromaTIc hyDrocarBon will pRevenT The formation of DIscolored sulfURiC ACiD. the cOst Of these reagEnts PReclUdes THeIr uSE in thE induStRY.
U.s. pat. No. 2,402,180 discloses a methOd For the ManufActure of triniTrotoluene INVOlving niTratIOn IN three steps: monO, di anD trinitratIOn stages. the spEnt acid fRom the triNITration sTagE is ForTifIED iN the nitrator iTSElf tO pRovide a MixEd acid fOr tHe dIniTraTiOn of added MononitrOtOlUeNe.
u.S. PAt. No. 2,849,497 dIScloses a CoNtiNuOus ProceSS for thE prepAratIoN oF NitRobenzeNE wHICh inVoLvEs coNtaCtIng thE speNT acId that rEmains aftEr tHE nitRaTiOn with fResh benzene to UsE up the majoR pOrtIon of aNY UnreacteD nitric acid in the spent acID mixturE. ThE imprOvemEnt resideS in The steP of EXtractIng disSolveD nItrIC Acid iN THe CruDe NitrobenzeNE ProDuct bY cOntaCting thE crude nitrobenzene WIth The denitrated WasTe acID AnD thEReAFteR dENitRATing the waste aciD containinG tHIs Nitric acid WIth FrEsh benzEne.
U.S. PaT. No. 2,012,985 diSCloses tHe nitratiOn of aromaTiC hydROCarBons such as Benzene, tOluene, xylENe and THe Like uSinG a spenT aCid ResulTing frOM thE nitrAtion oF aN alphaTic alCoHol contaIning at least two hydroxy gRoups, sUch as NitRoglyceriNe sPEnt Acid.
U.S. Pat. no. 2,256,999 diScloses a niTraTioN procEss WHich iS carRIeD ouT With tHe utILization oF ThE enTIRe Heat of mixinG AND
charring) of the spent aci d. One suc h met hod  in vo lves  the  extraction of thespent acid with the ar omati ch ydro c ar bon b eing ni t ra t e d i nth e p ro c es s. Th ismethodremoves th e e xc ess nitric a c id  from thespe nt acid in t heform o fthe monon itr o der ivativ e  of th e aromati ch ydroca r bon. Sp e c if ical ly, in a dinitrot o lu e ne process tol uene i su se d toext ract the s pe nt ac i d to re c ov e r the nitric acid a s mononitro t olu ene in  a  po s t-reac tor.Im p rac tically tig ht c ontrol ov er the stoichi o metricreacti onofthea ro ma tic  h y dro c ar bon isnecessar yto  prev entf o r m atio n o f su lfuri c acid solubl e c olor bod ies w hichrend er  thefinaldenit ri fied sulfuric a cidblack ordar kred ."Char r ed" or  bl ack  spentacid is una cc e p t ab le in the industry  p a r ti cularlyif the de ni t rified s pe ntacid i s sen t to aphosphat e prod u ce r. 
In ano th er met ho d,tre atmen t  ofthe sp ent acid  of n i tration with a variety of ox i di z i ng or r edu cing agents  whi c h de stro y  t hen itrou s aci dp re s ent in spent acid p ri or toextra ction with th e aromatic h y drocarbo n wi l lp revent the for matio n of disco l ored sul furic  acid. T he cost o f these re age nts  pr ecl u d es  their use in t he i nd ustry.U.S . Pat.No.  2, 402 ,18 0discloses  a metho dfo rth e m anufa c ture oftr ini tr oto luene involv ing n itra ti on inthree s t ep s :  mon o,  d i an d t ri nitra tion sta ges. Th e spent a cid from  t he  trinit ration stageis  fortified  i n t he nit r a tor itse lf to provide a mixed a c id forthe  dini trat ion of ad ded  monon itr o toluen e.
U.S . Pat .No. 2 ,849, 4 9 7dis cl oses a con t i nuo us pr oc essfor the  preparation of ni t rob enzene whichinv olve s co nta c ti n g t he spe n t  acid that rema ins afterth e  n itration w i thfr esh ben zene to  useu p the m ajor port ion of an yunre a c ted  nitric ac id in th e spent a c id mi x tu re. T heimprov em ent  resi des in the  step  of ex tr acting  diss ol ved nitr ic acid in the crude ni troben zenepro duct by c ont a cti ng the cr udenitrobenze newit h the  de n itrat ed w a st e a c id an d th e reafter d e ni tra t i ng  the wastea c i d c ontai nin g  thisnitr ic acid with fres h  benzene.
U.S.  Pat . No.  2, 0 12,9 85  discloses the  ni tr a t ion of a ro matic hydro carbonssu c h asbenzen e, tol uene, x y l en e  and t he l ike  using aspe nt acid re su lt i ng fro m th enitrat ion of an a l p hatic alcohol co ntain i n g atl eas t two  h ydroxyg roup s, such as  nitroglyce rine s pent  acid .
U.S.Pa t. No.  2, 25 6,999 disc l oses a ni trati on proc es s wh ich  is ca rrie d out w ithth e u tilizatio n of th ee nti re h eat o fmixi ng and
charring) of_the spent_acid. One such method_involves the_extraction_of the_spent_acid with the_aromatic hydrocarbon being_nitrated in the process._This method removes_the_excess nitric acid from the spent acid in the form of the mononitro derivative_of_the aromatic_hydrocarbon._Specifically,_in a dinitrotoluene process toluene_is used to extract the_spent acid_to recover the nitric acid as mononitrotoluene in_a_post-reactor. Impractically tight_control over the stoichiometric reaction of the aromatic hydrocarbon_is necessary to prevent formation of_sulfuric acid soluble_color_bodies_which render the final_denitrified sulfuric acid black or dark_red. "Charred" or black spent acid_is unacceptable in the industry particularly if_the denitrified spent acid is sent_to a phosphate producer.
In another_method, treatment_of the spent acid of_nitration with a_variety of_oxidizing or reducing_agents which destroy the nitrous acid_present in spent_acid prior to extraction with the_aromatic_hydrocarbon will prevent_the_formation_of discolored_sulfuric acid. The_cost_of these_reagents_precludes their use in the industry.
U.S._Pat._No. 2,402,180 discloses a method for the_manufacture of trinitrotoluene involving_nitration_in three steps: mono,_di and trinitration stages. The_spent acid from the trinitration stage_is fortified_in the_nitrator itself to provide a mixed acid for the dinitration of_added mononitrotoluene.
U.S. Pat. No. 2,849,497 discloses_a continuous process for_the preparation_of_nitrobenzene which involves_contacting_the spent_acid that remains after the nitration with_fresh benzene_to use up the major portion_of any unreacted nitric_acid_in the spent acid mixture. The_improvement resides in the step of_extracting dissolved nitric acid in_the_crude_nitrobenzene product by contacting the_crude nitrobenzene with the denitrated waste_acid and thereafter_denitrating the waste acid containing this nitric_acid_with fresh benzene.
U.S. Pat. No. 2,012,985_discloses_the nitration of aromatic hydrocarbons such_as_benzene,_toluene, xylene and the like_using a spent acid resulting from_the nitration of an alphatic alcohol containing at least_two hydroxy groups,_such as nitroglycerine spent acid.
U.S._Pat._No._2,256,999 discloses a nitration process which is carried out with_the utilization_of the entire_heat of mixing and