zeolitebased catalyst bodies are employed on a global scale in important chemical processes , such as the synthesis of many bulk chemicals1 ,  2 as well as crudeoil refining.3 ,  4 particular examples include xylene isomerisation,5 ,  6 benzene alkylation7 ,  8 and methanol conversion to hydrocarbons.9 ,  10 catalyst bodies , such as extrudates , have millimetresized dimensions consisting of active phase most often nonhomogeneously dispersed in binder(s).11 the overall aim is to obtain the required mechanical strength to resist attrition loss , maintain chemical stability for prolonged use and limit expenditure ( among many others ) , whilst achieving high catalytic activity and selectivity . limited academic knowledge exists in the details of these commercial catalysts . unlike bulk or supported activephase catalysts predominately used in academic research , the choice of binder(s ) , combined with the formulation method , can severely impact the material s catalytic properties.12 the role of the selected binder is particularly lacking in understanding and is often incorrectly labelled  inert  . zeolite  binder interactions induced upon the formulation process have a substantial impact on the activity , selectivity and stability of the working catalyst . a recent perspective by hargreaves and munnoch highlights the importance of binder effects that occur in such zeolitebased materials , including modification of coking characteristics , poison entrapment , transfer of chemical species , as well as physical property enhancements.13 silica and alumina are inexpensive inorganic binders commonly employed in catalyst bodies.1419 although sio2 lacks acid sites able to partake in acidcatalyzed processes , its intimate contact with impregnated zeolite can induce solidstate ion exchange , with michels et  al . and lee et  al . reporting loss of brnsted acidity as a result of dealumination from the zeolite framework.17 ,  18 although the determination of acid sites present in al2o3 binder is less obvious , effects such as aluminium migration from the binder material to the zeolite framework is reported , creating an increase in inter and/or intracrystalline acidity , which affects the overall catalytic activity and selectivity.14 
  one of the main contributions to the lack of academic interest in zeolitebased catalyst bodies is the inability to study in detail these largescale materials with high enough spatiotemporal resolution , owing to the reduced fieldofview required and the lack of suitable characterisation techniques available.12 ,  20 ,  21 given the recent enhancements in chemical imaging methods,22 ,  23 such as singlemolecule and confocal fluorescence microscopy,21 ,  2427 uv / vis microspectroscopy,28 ,  29 ir and raman microscopy,3032 transmission soft and hard xray microscopy,3336 xray diffraction computed tomography37 and focusedionbeam scanning electron microscopy,38 coupled with the improved control of these commercial catalysts for modernday processes,39 the time is ripe for a shift in academic focus towards understanding these more complex multicomponent and hierarchically structured catalyst materials . the combination of uv / vis microspectroscopy and confocal fluorescence microspectroscopy ( cfm ) have been used recently with remarkable spatiotemporal resolution to investigate brnsted acid properties in micrometresized fluid catalytic cracking ( fcc ) particles29 ,  4043 and more recently millimetresized zsm5containing binderbound extrudates.44 ,  45 by staining these materials with a probe molecule such as thiophene and following the formation of fluorescent oligomer species in  situ , their location , distribution and selectivity provide valuable information on the strength and density of acid sites present . owing to the specific absorption wavelengths of each lightabsorbing oligomer species , laserline wavelengths in close proximity can be used to selectively excite one or more fluorescent species , which creates a 2  d/3  d chemical map . in the work herein , two series of zsm5containing sio2 and al2o3bound millimetresized extrudates ( with varying activephase content ) were investigated with uv / vis microspectroscopy and cfm . furthermore , microcrystalline silicalitebased al2o3bound samples were studied to confirm possible aluminium migration . by employing thiophene oligomerisation as a selective probe reaction for brnsted acidity , catalytic activity and selectivity were determined for each sample and related to their physicochemical properties . the variations in selectivity , location and distribution of fluorescent oligomer species ( originating on brnsted acid sites ) between sio2 and al2o3bound samples were visualised noninvasively in three dimensions , with a view to establishing binder effects that occur with high spatiotemporal resolution . elemental analysis was used to determine the extent of partial proton exchange in both sio2 and al2o3bound na  zsm5containing extrudates . as shown in table  1 , the na content remaining in each extrudate was similar for both binder types ( i.e. , a linear increase with zsm5 content ) , therefore , the number of brnsted acid sites present is comparable between each series . the publisher did not receive permission from the copyright owner to include this object in this version of this product . please refer either to the publisher 's own online version of this product or the printed product where one exists . to measure the bet surface area and porevolume distribution of both series of extrudates , an increase in binder content corresponded with a decrease in bet surface area , typically associated with a dilution of the zeolite content ( table  1 ) . furthermore , micropore area and volume also suffer a decline as the activephase content is reduced . the results of the porevolume measurements of pure zeolite , pure binder and the mixedphase extrudates highlight the impact on combining both components during the preparation procedure . evidently , the increase in content of both binder types corresponds with an increase in overall pore volume ( i.e. , the pore volume of z80si , 0.35  cm  g , is smaller than that of z20si , 0.70  cm  g , table  1 ) . however , the predicted pore volumes ( calculation based on those of the pure components ) of the zsm5:binderbound extrudates are significantly higher than the experimentally determined ones . particularly in the case of the sio2bound samples , as much as a 21  % decrease was measured for z20si , with the al2o3bound samples observing the same trend but to a lower extent ( z20al , 11  % decrease ) . this exemplifies the changes induced upon combining both the active zeolite phase and the binder material in extrudates , with the decrease in pore volume attributed to blockage / coverage of the binder pores with zsm5 crystals / agglomerates and/or morphological changes in the binder . noticeably , the zsm5based sio2bound extrudates express a far wider poresize distribution than their al2o3bound counterparts . an increase in activephase content creates a narrower poresize distribution in both cases , owing to the lower contribution of mesopores from the decreased binder content . halenda adsorption method with n2 , for : a )  a series of zsm5containing sio2bound extrudates and b )  a series of zsm5containing al2o3bound extrudates . concerning the difference in poresize distribution and pore volume of the sio2 and al2o3bound extrudates , their adsorption capacities were determined by using nhexane adsorption . in table  s1 in the supporting information , the experimental values are presented , which clearly display the higher capacity of al2o3bound zsm5containing extrudates in comparison to that of their corresponding sio2bound extrudates . measured values correspond well with predicted values ( based on pure component measurements ) , with the zsm5 crystals completely accessible . in figure  2 the nh3temperature programmed desorption ( tpd ) profiles of both series of zsm5based binderbound extrudates are shown , with table  s1 presenting the amounts of nh3 desorbed for each sample . as expected , zsm5 crystals produce a broad band centred at 430  c , attributed with nh3 desorbing from strong acid sites.46 a small peak at 270  c is associated with physisorbed nh3 . owing to the lack of acid sites in sio2 , z80si experiences no significant change relative to that of zsm5 ( figure  2  a ) , however , the large dilution of the active phase in z20si substantially decreases the amount of nh3 desorbed on the limited strong acid sites present . the nh3tpd profile of z80al ( figure  2  b ) is similar to that of z80si , however , the peak maximum , associated with strong acid sites is shifted slightly to higher temperatures . the dilution of the active phase in z20al produces a dramatic decrease in strong acid sites , with the peak maximum now shifted significantly to the left ( 340  c ) . this behaviour corresponds well with the nh3tpd profile of pure al2o3 , which produces a broad band centred at 346  c , showing that al2o3 , unlike sio2 , can not be considered an  inert tpd profiles of nh3 for : a )  a series of zsm5containing sio2bound extrudates and b )  a series of zsm5containing al2o3bound extrudates . the morphology and distribution of zsm5 crystals in sio2 and al2o3bound extrudates as assessed with sem is illustrated in figure  s1 in the supporting information . the crystal / agglomerate size of zsm5 is in the range of 26  m ( figure  s1  a ) . if viewing such small sections of the extrudates , conclusions on the distribution of the active phase in the binder should be drawn with care . however , it can be seen , particularly for z50si and z50al ( figure  s1  d and e ) , that al2o3 covers the crystals more homogeneously than sio2 , creating a  blanket  between crystals . the selective staining of brnsted acid sites in a noninvasive manner has recently been used to study catalyst bodies , such as fcc particles40 ,  47 and zsm5containing sio2bound extrudates.44 herein we employed thiophene oligomerisation as a probe molecule reaction to study brnsted acidity variations and binder effects between both zsm5containing sio2 and al2o3bound extrudates . as seen in scheme  1 , several carbocations are formed and evidently two reaction pathways take place upon the adsorption and protonation of thiophene monomers : either progressive oligomerisation to form larger more conjugated / extended oligomers ( compounds c , d , e ) or ring opening to form thiollike species ( f compounds ) . in figure  3  a , the in  situ optical absorption spectra ( 400700  nm ) of a pure zsm5 pellet reacted with thiophene are shown . owing to the complex nature of the raw absorption spectra obtained ( figure  s2 ) , multivariate analysis and timedependent density functional theory calculations ( on nonconfined molecules ) were performed . these were used to fit and tentatively assign the bands formed for each sample s optical spectra , with the background selectively removed . this procedure and more details can be found in our previous work.44 
  proposed reaction pathway of thiophene oligomerisation on zeolite acid sites . two different reaction pathways are possible at this stage : opening of the thiophene ring and subsequent reaction with a second monomer to form a thiollike carbocation ( f1/f1t / f2/f2t ) . alternatively , dimerisation ( to c ) can occur followed by further oligomerisation ( to d ) or opening of the thiophene ring , forming a thiollike carbocation ( f1/f1t / f2/f2t ) . the trimeric carbocationic species ( d ) can undergo further oligomerisation to form more extended / conjugated species ( e1/e2 ) . filtered in  situ optical absorption time series spectra ( using peak fitting and multivariate analysis ) during thiophene oligomerisation over : a )  zsm5 pellet , b )  z80si , c )  z80al , d )  z50si , e )  z50al , f )  z20si and g )  z20al . samples were impregnated at 30  c before applying a temperature ramp ( at 30  c  min ) to 120  c and spectra were recorded every 10  s for a total of 1000  s. clearly , four bands at 410 , 485 , 550 and 650  nm are formed over the reaction time . the formation of each band over time is observed with more clarity in figure  s3  a. the initial oligomer species formed at 410  nm was assigned to a dimeric and/or trimeric intermediate species . both the bands at 410 and 650  nm appear to rise and fall at a similar rate , followed in quick succession by the formation of bands at 485 and 550  nm . according to scheme  1 , this is caused by competing reaction pathways , by which the dimeric / trimeric intermediate species undergo both ring opening to form thiollike species ( f1t ) and progressive molecular growth ( e1 ) . the introduction of sio2 binder ( z80si ) correlates with an initial formation of a fourthiophene ring oligomer ( e1 ) ( absorption at 550  nm , figure  3  b ) . most likely , it is not the first intermediate / product species formed , however , owing to the limitations of the instrument spectral detection range , oligomers absorbing in the uv light region ( i.e. , c ) are not detected . the development of both the 410 and 485  nm bands is similar to that of the pure zsm5 pellet , for which a decrease in the intensity of the former band is accompanied by an increase in the latter . the timeevolved optical spectra of z80al are shown in figure  3  c. differing from its corresponding sio2 counterpart , three absorption bands at 410 , 485 and 550  nm are formed simultaneously at approximately 110  s. competing reaction pathways ( scheme  1 ) provide an explanation for this phenomenon , with the progressive molecular growth mechanism becoming dominant as the reaction proceeds . both z50si and z50al exhibit significantly increased initial reactivity compared with extrudates containing higher zsm5 content . in figure  3 d and e , the optical absorption spectra produced by both z50si and z50al are presented , respectively , with corresponding band formation over time shown in figure  s3  d and s3  e. the simultaneous formation of 410 , 485 and 560  nm bands for the sio2based extrudate is not dissimilar to that of the al2o3based extrudate , however , noticeably there are slight shifts in both the 485 and 550  nm bands in each sample . the absorption band at 550  nm associated with the fourthiophene ring species ( e1 ) is now present at 560  nm for z50si , and the thiollike species ( f1t ) , which absorbs light at 485  nm in both pure zsm5 and z80al , now present at 480  nm for z50al . these results suggest that the particular carbocationic species are present in an alternate chemical environment in z50si and z50al . however , owing to the complex nature of the thiophene oligomerisation mechanism and the corresponding band assignments of species formed , the formation of other oligomers that absorb light at this wavelength can not be ruled out . in terms of oligomer selectivity , z50si exhibits a far higher ratio of more conjugated species ( band at 560  nm ) versus less conjugated species ( 410  nm ) compared to the ratios displayed by both pure zsm5 and z80si ( compare figure  3  d with figure  3  a , b ) . the al2o3based extrudate on the other hand exhibits higher selectivity towards thiollike species ( absorbing at 480  nm ) than z80al ( compare figure  3  e with figure  3  c ) . this trend , that is , increasing binder content correlates with increasing selectivity towards more extended / conjugated carbocationic species , continues in both z20si and z20al samples . in figure  3 the absence of the 410  nm band and the higher intensity of the 560  nm band suggests the further reactivity of the dimeric / trimeric species ( 410  nm band ) towards higher oligomers . the optical absorption spectra produced by z20al ( figure  3  g ) present a substantially higher selectivity towards ringopened species ( 485  nm band ) than towards higher oligomers ( 550  nm band ) , which differs substantially from the results for the z20si extrudate ( figure  3  f ) . moreover , the band at 470  nm represents a hypsochromic shift from the band at 480  nm in z50al , indicating the presence of this oligomer species in the binder to a further extent . upon termination of thiophene oligomerisation performed on zsm5containing sio2 and al2o3bound extrudates , cfm was employed to visualise the distribution of various fluorescent carbocationic species present in two and three dimensions . excitation of species that absorb light at approximately 485 and approximately 550  nm is possible by using 488 and 561  nm lasers simultaneously . the 3  d visualisation of pure zsm5 crystals postreaction is given in figure  s4 . all crystals / agglomerates within the field of view are fluorescent ( green / yellow ) , with a select few intensely fluorescent ( yellow ) . this heterogeneous distribution is attributed to the lower amount of na present in these specific crystals / agglomerates , leading to a higher number of brnsted acid sites ( hence intensely fluorescent crystals).44 in figure  4 , the 3  d topview volumes of : z80al , z80si ; z50al , z50si , z20al , and z20si extrudates are presented . the same heterogeneous distribution of fluorescent intensity can be observed for z80si ( figure  4  a ) as for pure zsm5 . as observed in their optical spectra , both pure zsm5 crystals ( figure  3  a ) and z80si ( figure  3  b ) exhibit a similar intensity of the 485 and 550  nm bands , which correlates with the similar fluorescent intensity / colour . in accordance with the optical spectra of the z80al extrudate ( figure  3  c ) , the orange fluorescence in the cfm image in figure  4  b indicates a higher concentration of more conjugated species ( which absorb light at 550  nm ) than in the corresponding z80si sample ( figure  4  a ) . 3  d topview cfm images of a )  z80si , b )  z80al , c )  z50si , d )  z50al , e )  z20si and f )  z20al after thiophene oligomerisation and excited with 488 and 561  nm lasers simultaneously . a similar trend is observed for both z50si and z50al extrudates ( figure  4  c and d , respectively ) . again , a heterogeneous distribution exists for both samples , with several crystals / agglomerates more fluorescent than the majority . the higher ratio of the 550560  nm band versus the 480485  nm band in the z50si sample ( see figure 3  d ) can be visualised by its yellow fluorescence produced ( figure  4  c ) . the opposite band intensity ratio was obtained for z50al ( see figure  3  e ) , and this is also displayed by zsm5 crystals emitting green / yellow fluorescence ( figure  4  d ) . the 3  d topview fluorescence images of both z20si and z20al exhibit only a few fluorescent zsm5 crystals / agglomerates in the field of view , owing to the limited amount of zsm5 present ( figure  4  e and f , respectively ) . however , the higher concentration of more conjugated species present in z20si ( see figure  3  f ) is displayed by an orange fluorescence . the yellow fluorescence in z20al correlates well with the higher ratio of less conjugated species , observed in the absorption spectra ( see figure  3  g ) . to understand the differences in activity and selectivity during thiophene oligomerisation between sio2 and al2o3bound zsm5containing extrudates , the physicochemical properties of each material must be taken into consideration . one of the most prominent features in the optical spectra of binderbound extrudates , in contrast to the spectra of a pure zsm5 pellet , is the higher ratio of more conjugated species ( compounds f / e ) versus less conjugated species ( compounds c / d ) . in particular , the 410  nm absorption band associated with dimeric / trimeric species decreases significantly in intensity from z80si z20si ( also with z80al , z20al ) , with a higher ratio of 480  nm and 550  nm bands , attributed to thiollike ( f1t ) and fourthiophene ring ( e ) oligomers , respectively . taking into account the larger pore volume of both zsm5containing sio2 and al2o3bound extrudates in comparison to a pure zsm5 pellet ( see table  1 ) , a correlation between the higher number of stored thiophene monomers available per active site and higher reactivity can be made . retaining the interest in selectivity variations , it is clear that whether sio2 or al2o3 binder is chosen , oligomer selectivity is influenced . it was previously reported that a higher number of brnsted acid sites present in fully protonexchanged nazsm5 sio2bound extrudates favoured the formation of thiollike species , in contrast to the formation of higher oligomers preferred by corresponding partially protonexchanged extrudates.44 therefore , the acidsite characteristics of samples play a large role in determining the reaction pathway during thiophene oligomerisation . from the optical absorption spectra of z50si and z50al ( figure  3  d and e , respectively ) , these bands are assigned to oligomer species formed through alternate routes during thiophene oligomerisation . for z50si , the higher ratio of the band ( 550560  nm ) attributed to fourthiophene ring oligomers ( e ) versus the band ( 480485  nm ) associated with thiollike species ( f1t ) is clearly visible . in contrast , z50al has a higher ratio of the thiollike species ( formed via a ringopening mechanism ) versus the higher oligomer species . s5 , no reactivity for pure sio2 extrudates is revealed , with only a limited reactivity of pure al2o3 extrudates . therefore , the noticeable change in selectivity between both binder types in extrudates containing zsm5 must be caused by physicochemical characteristics induced upon extruding both components . the larger degree of weaker acid sites in al2o3bound samples in contrast to sio2bound samples ( figure  2 , table  s2 ) might alter the reaction pathway . however , given the limited reactivity of pure al2o3 extrudates , other avenues should be explored . it is known that the use of al2o3 as a binder if combined with zeolites can lead to aluminium migration from the binder to the surface of the zeolite crystals / zeolitebinder interface , creating additional acid sites.1416 ,  47 therefore , to observe possible aluminium migration and its influence on reactivity , microporous silicalitebased al2o3bound extrudates sil80al and sil20al ( two selected ratios comparable to z80al and z20al ) were studied for thiophene oligomerisation . although silicalite has a nearidentical structure to zeolite zsm5 , its lack of acidity ( table  s2 ) is ideal to study aluminium migration . nh3tpd on both sil80al and sil20al revealed the presence of weak acid sites in both extrudates ( table  s2 , figure  s6 ) . however , with a larger amount of nh3 adsorbed ( 0.27  mg  g ) and the higher maximum temperature of desorption ( 318  c ) in sil20al , a larger number of acid sites are present , with a stronger acidity than in sil80al ( 0.1  mg  g , 286  c ) . the optical absorption spectra of sil80al are illustrated in figure  5  a. strikingly , a relatively high reactivity is obtained , clearly demonstrating that brnsted acid sites have been formed during preparation . as with the zsm5based extrudates , bands at 410 and 485 however , the absence of a band at 550  nm ( compound e ) , coupled with the appearance of a band at 440  nm ( f2 ) , suggests the favouring of the ringopening reaction pathway to the further oligomerisation route . in figure  5  b and c , the location of such fluorescent oligomer species formed on acid sites in the silicalite structure in 3  d is visualised by using cfm ( employing 488 and 561  nm lasers , respectively ) . a ,  d )  filtered in  situ optical absorption time series spectra during thiophene oligomerisation over sil80al and sil20al , respectively . corresponding 3  d topview cfm images of b ,  c )  sil80al and e ,  f )  sil20al , excited with b ,  e )  488  nm laser and c ,  f )  561  nm laser . further investigation of an extrudate containing a higher ratio of al2o3 than silicalite ( sil20al ) , enforces the suspected aluminium migration , with the optical absorption spectra illustrated in figure  5  d. here , as expected , aluminium migration is observed to a higher extent , with an additional band present at 550  nm displaying the higher reactivity of sil20al compared to sil80al . this higher reactivity is also supported by the higher fluorescence intensity observed if exciting the sample with a 561  nm laser ( figure  5  f ) compared to that of sil80al ( figure  5  c ) . for both sil80al and sil20al , the higher intensity ratio of thiollike species bands ( 440 , 485  nm ) versus the fourthiophene ring oligomer bands ( 550  nm ) confirms that aluminium migration favours the ringopening pathway . this binder material effect can explain the higher ratio of thiollike species formed in zsm5containing al2o3bound extrudates compared to the one in their corresponding sio2bound extrudates . another significant feature of the uv / vis absorption spectra of binderbound zsm5containing extrudates , in contrast to the spectra of the pure zsm5 pellet , is the absorptionband shifts observed upon thiophene oligomerisation . hypsochromic ( blue shift ) or bathochromic ( red shift ) shifting of bands in the absorption spectra could be caused by the molecules absorbing light at a specific wavelength , interacting with neighbouring molecules different to those present in zsm5 pores ( i.e. , change in chemical environment ) . in the case of both sio2 and al2o3bound zsm5containing extrudates , hypsochromic / bathochromic band shifts occur and become more apparent with increasing binder content . whether sio2 or al2o3 binder is present determines which absorption bands in the optical spectra shift , which reinforces the postulation that a change of chemical environment occurs for the molecules in question . for both z50al and z20al , the band originally at 485  nm in z8020 hypsochromically shifts to 480 and 470  nm , respectively . this could be the result of the formation of this thiollike species ( f1t ) on acid sites created by al migration , in line with its predominant formation in both z50al and z20al . in contrast , for z50si and z20si the band attributed to fourthiophene ring oligomers ( e ) bathochromically shifts from 550 to 560  nm . it is highly plausible that these larger molecules grow off the surface of zsm5 crystals / agglomerates into the surrounding binder . evidence of this is visualised by 3  d images obtained by cfm and thiophene oligomerisation reaction . in figure  6 a , the 26  m fluorescent green domains are displayed , the locations of which are consistent with the morphology of zsm5 crystals / agglomerates ( figure  s1  a ) , containing oligomer species ( compounds f ) that absorb light at 488  nm . the additional use of a 561  nm laser ( whilst simultaneously employing a 488  nm laser ) demonstrates that these larger red fluorescent conjugated / extended species ( e ) appear to grow off the surface of zsm5 crystals / agglomerates into the sio2 binder ( figure  6  b ) . 3  d cfm images of a )  volume of z80si excited with 488  nm laser , showing fluorescent green oligomers present in zsm5 crystals / agglomerates ; b )  same volume as in ( a ) , excited simultaneously with 488 and 561  nm laser , showing the growth of larger oligomers off the surface of zsm5 crystals / agglomerates . to confirm that the surrounding area of zsm5 crystals / agglomerates is indeed binder material , a separate experiment using both thiophene and nile blue chloride43 on z80si was performed . owing to the large molecular dimensions of nile blue chloride , it is unable to fit inside the zeolite pores and therefore only occupies the binder . by exciting z80si with both 488 and 642  nm lasers , both these compounds can be excited to determine the distribution of active phase and binder . in figure  7 , the location of fluorescent green zsm5 domains is illustrated , which are closely surrounded by sio2 , which emits a red fluorescence . this result confirms the close proximity of the binder material to the zsm5 domains , which can allow the growth of oligomer species off the surface of the zsm5 crystals into the binder , leading to optical absorption band shifts . 2  d cfm images of z80si reacted with thiophene and impregnated with nile blue chloride . simultaneous excitation with 488 and 642  nm lasers produced a green fluorescence attributed to zsm5 domains with surrounding binder producing a red fluorescence . until recently , establishing binder effects in industrialscale catalysts such as millimetresized extrudates has been based on bulk characterisation techniques because of lack of academic research and available techniques able to investigate these complex materials . herein , advanced noninvasive uv / vis and confocal fluorescence microspectroscopy , coupled with thiophene as a selective probe for brnsted acidity , were applied to investigate the binder effects occurring in zeolite zsm5containing sio2 and al2o3bound millimetresized extrudates . the selectivity of fluorescent oligomer species located on brnsted acid sites was found to be dependent on the binder type present . thiollike species , obtained through a ringopening mechanism were predominantly formed on zsm5containing al2o3bound samples , with corresponding sio2bound samples favouring higher oligomer species . further studies on microporous silicalitebased al2o3bound samples confirmed that aluminium migration occurs in al2o3bound samples , creating brnsted acid sites that favour the formation of thiollike species . moreover , it was found that more conjugated oligomer species appeared to grow off the outer surface of zsm5 crystals into the surrounding binder material , which is clearly positioned close by . evidently , the explored microspectroscopic techniques , in combination with ( other ) selective probes for , for example , lewis acid sites , are able to enhance our knowledge of processes occurring in these globally used catalysts , with a view to enhancing process efficiency . two series of sio2 and al2o3bound ( h)na  zsm5 containing extrudates were prepared according to patent us6,039,864 ( example 1 ) . for the sio2bound extrudates : the required amounts of zsm5 crystals , h2o , sio2 gel ( aerosil 300 ) , silica sol ( nalcoag 1034a ) and extrusion aid were mixed prior to extrusion into 2  mm diameter extrudates ( al2o3bound extrudates were prepared by a similar procedure , using versal  300 ) . partial ionexchange was performed after a first calcination ( 500  c for 18  h ) of the extrudates , by suspending in a 1  m solution of ammonium nitrate for 4  h , followed by washing and drying and a final calcination ( 500  c for 18  h ) . zsm5 crystals with a si / al ratio of 32 and an average crystal size of 3  m were used to make silica and aluminabound extrudates containing 20 and 80  wt . silicalitebased al2o3bound extrudates were also prepared by a similar method , with the exclusion of al during silicalite crystal preparation . extrudate sample notations are as follows : abc , in which  a  corresponds to either zsm5 (  z  ) or silicalite (  sil  ) and  b  corresponds to the zsm5 or silicalite content ( wt .  % ) . finally , c  corresponds to sio2 bound series (  si  ) or the al2o3 bound series (  al  ) . as an example : the samples ( 200  mg ) were digested in a mixture of acids ( 30  % hcl , 3  ml ; 65  % hno3 , 1  ml ; 40  % hf , 2  ml ) for 45  h ( the first hour with sonication ) and then further diluted to 100  ml with purified water from a merck milliq water system . further dilution with purified water containing 1  % 65  % hno3 was necessary depending on the expected concentration of the elements to be analysed . elemental analysis was done with a varian vista mpx inductively coupled plasma optical emission spectrometer using multielement standards provided by merck and alfa aesar . n2 physisorption on all samples was performed with an automated gas sorption system micromeritics tristar 3000 . prior to measurements , all samples were degassed at 250  c for 12  h. surface areas were calculated using by the bet model , whilst external surface area , micropore surface area and micropore volume were determined by using the tplot method . extrudates were broken in two , attached to a sem stub using conductive carbon cement and coated with pd / pt in a cressington 208hr sputter coater . the fracture surface was imaged in a jeol jsm6340f field emission gun scanning electron microscope ( fegsem ) operated at 2  kv using secondary electrons . a mettler toledo tga / sdta 851 was used to measure adsorption of ammonia at 250  c followed by desorption under adsorption equilibrium in the temperature range of 250 to 700  c . after a pretreatment in air at 500  c , the samples were exposed to a series of pulses of 1  % ammonia in he at 250  c from which the ammonia adsorption data were generated . desorption was completed by applying a temperature ramp to 700  c at 5  c  min under 1  % ammonia in he flow . the nhexane capacity of the materials was determined by thermogravimetric analysis on a ta q5000 instrument . the nhexane was delivered with a sparger at a partial pressure of 74  torr in he . after the samples were pretreated at 500  c for 30  min , the nhexane adsorption capacity was measured at 90  c . optical microspectroscopy studies were performed in reflectance mode by using an olympus bx41 m upright research microscope , equipped with a 500.5  na objective lens . the microscopy setup was equipped with a 50/50 doubleviewport tube , which accommodated a ccd video camera ( colorview iiiu , soft imaging system gmbh ) and an optical fiber mount . the microscope was connected to a ccd visible spectrometer ( avaspec2048tec , avantes ) by a 200  m core fiber . uv / vis spectroscopy measurements were performed by using an open in  situ cell ( linkam scientific instruments , ftir 600 ) equipped with a temperature controller ( linkam scientific instruments tms 94 ) . all extrudate samples used in the experiment were of similar dimensions ( 51.5  mm ) , with spectra collected from approximately 55  m areas of each extrudate . each sample was impregnated with the desired probe molecule solution ( 5  l ) at 30  c , before applying a temperature ramp ( at 30  c  min ) to 120  c . optical absorption spectra were recorded every 10  s for a total of 1000  s. a nikon eclipse 90i confocal microscope with a 1000.73  na dry objective was used for the fluorescence microscopy investigations . excitation light was provided by focusing four specific laser lines ; 404 , 488 , 561 and 642  nm on the desired sample , located in an open in  situ cell ( linkam instruments , ftir 600 ) . the microscope was equipped with a nikon a1 scan head , accommodating the optics , which couple fibre optics for excitation and emission light with the microscope . a spectral analyser in the nikon a1 system was equipped with 32  photomultiplier tubes ( pmts ) set to collect emission light in the three specific regions depending on the laser line chosen , with a resolution of 6  nm , which were 427614  nm , 508697  nm , 581743  nm , 662743  nm , corresponding with excitation wavelengths of 404 , 488 , 561 and 642  nm , respectively . 3  d images were recorded at a similar focal depth in each sample by using identical laser power . prior to microscopic analysis , each sample was impregnated with the desired probe molecule solution ( 5  l ) , before applying a temperature ramp ( at 30  c  min ) to 120  c , at which temperature the samples were held for 15  min and cooled to 30  c . generally , for each optical absorption data set ( 100  spectra ) , principal component analysis was used to determine the number of clusters needed to perform nonnegative matrix factorisation ( 500  000 iterations used ) . the obtained eigen spectra were fitted with the minimum number of gaussians to achieve a good fit ( r 
 > 0.99 ) . these gaussians were then used as a model , to fit each spectra in the time series . gaussians determined as the background signal were removed , leaving freestanding gaussians , which provided filtered timeevolved optical absorption spectra .
abstractmicrospectroscopic methods were explored to investigate binder effects occurring in zsm5containing sio2 and al2o3bound millimetresized extrudates . using thiophene as a selective probe for brnsted acidity , coupled with timeresolved in situ uv / vis and confocal fluorescence microspectroscopy , variations in reactivity and selectivity between the two distinct binder types were established . 
 it was found that aluminium migration occurs in zsm5containing al2o3bound extrudates , forming additional brnsted acid sites . 
 these sites strongly influence the oligomer selectivity , favouring the formation of thiollike species ( i.e. , ringopened species ) in contrast to higher oligomers , predominantly formed on sio2bound zsm5containing extrudates . not only were the location and distribution of these oligomers visualised by 3  d analysis 
 , it was also observed that more conjugated species appeared to grow off the surface of the zeolite zsm5 crystals ( containing less conjugated species ) into the surrounding binder material . 
 furthermore , a higher binder content resulted in an increasing overall reactivity owing to the greater number of stored thiophene monomers available per brnsted acid site .