Binder Effects in SiO 2 - and Al 2 O 3 -Bound Zeolite ZSM-5-Based Extrudates as Studied by Microspectroscopy

• Published in: ChemCatChem 2015-04, Vol.7 (8), p.1312-1321
• Main Authors: Whiting, Gareth T, Meirer, Florian, Mertens, Machteld M, Bons, Anton-Jan, Weiss, Brian M, Stevens, Paul A, de Smit, Emiel, Weckhuysen, Bert M
• Format: Article
• Language: English
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201402897

Microspectroscopic methods were explored to investigate binder effects occurring in ZSM-5-containing SiO - and Al O -bound millimetre-sized extrudates. Using thiophene as a selective probe for Brønsted acidity, coupled with time-resolved 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 ZSM-5-containing Al O -bound extrudates, forming additional Brønsted acid sites. These sites strongly influence the oligomer selectivity, favouring the formation of thiol-like species (i.e., ring-opened species) in contrast to higher oligomers, predominantly formed on SiO -bound ZSM-5-containing 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 ZSM-5 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 Brønsted acid site.