Preparation of the Novel Mesoporous Solid Acid Catalyst UDCaT-4 via Synergism of Persulfated Alumina and Zirconia into Hexagonal Mesoporous Silica for Alkylation Reactions Ganapati D. Yadav,* Ambareesh D. Murkute University Institute of Chemical Technology (UICT), Department of Chemical Engineering, University of Mumbai, Matunga, Mumbai ± 400019, India Fax: (  91)-22-2410 2121, e-mail: gdyadav@yahoo.com Received: November 20, 2003; Accepted: March 5, 2004 Abstract: A novel mesoporous solid acid catalyst named UDCaT-4 was designed by loading persul- fated alumina and zirconia (PAZ) into highly oredered, hexagonal mesoporous silica (HMS). UD- CaT-4 was characterized by XRD, BET surface area and pore size analysis which revealed that neither pore blocking nor structure collapse of HMS had occurred. NH 3 -TPD and FTIR were used to deter- mine the acid strength and nature of the sulfate ion retainedonthesurfaceofUDCaT-4.Itisknownthat HCl and water have detrimental effects on the activity of the zirconia-based catalyst. Hence, the activity of UDCaT-4 was evaluated in comparsion with that of bulk PAZ in the liquid-phase alkylation of toluene with benzyl chloride and also in the vapour-phase alkylation of mesitylene with isopro- panol, where acid and water are generated in-situ, respectively, as co-products. The superior catalytic acivity of UDCaT-4 is atributed to the uniform dispersion of the superacidic centers of PAZ into HMS vis-a¡-vis bulk PAZ. Reusability and time on- stream studies reveal that UDCaT-4 is a robust and reusable catalyst even in the presence of HCl and H 2 O. Keywords: alkylation; alumina; mesoporous materi- al; persulfation; silica; zirconium Homogeneous catalysis is widely used in several indus- trieswhichproducewastestothetuneof10±100kg/kg product depending on the number of stages used and type of industry. Alkylation, acylation, nitration, ester- ification, hydration, dehydration, condensation, oligo- merization and polymerization are some of the impor- tantreactionswhichareacidcatalyzed.Useofhomoge- neous acid catalysts leads to several problems such as loss of conversion, yield and selectivity, presence of impurities,corrosionofequipment,hazardsofhandling corrosive acids and neutralization of the resulting reaction mass leading to the generation of large quantities of dilute dissolved salts. Since the prices of finechemicalsareveryhighandvolumeslow,noserious attempts were made until recently to recover the catalysts or change the processes. There are a large number of well studied solid acids available as replace- ments for liquid acids, amongst which zeolites have emerged as a promising alternative. Unfortunately, the slow diffusion of reactants through the zeolitic micro- porous structure makes them relatively poor catalysts and their stability is questionable in reactions where acids are generated (e.g., anhydrous HCl as a co- product), which may remove aluminum species from theframeworkofthezeolite.Furthermore,zeolitesare found to deactivate at high temperatures due to coke formation. [1±7] Mesoporousmaterialswithtailoredcata- lyticcenterswillbemostsuitableforreactionsofbulky molecules. Hexagonally ordered, mesoporous silicates such as FSM-16, HMS (hexagonal mesoporous silica) andMCM-41,possessinglargesurfaceareas( >800m 2 /g) and highly ordered mesopores (2±10 nm) can be functionalized to extend their applications to a variety ofareas. [8±13] Among many solid acid systems other than zeolites andclays,sulfatedzirconiahasreceivedmuchattention due to its superacidity. [14] A number of attempts have been made to improve the acidity of zirconia-based catalysts by incorporating different transition metals [15] but they suffer from deactivation at high temperatures. The stability of sulfated zirconia can be improved by incorporatingaluminainzirconiafollowedbytreatment with ammonium persulfate. [16] Persulfated alumina zir- conia (PAZ) exhibits excellent catalytic activity and better stability towards coke formation than sulfated zirconia but its low surface area and non-uniform pore sizelimitsitspotentialapplications.Thus,inthecurrent work,useofhexagonalmesoporoussilica(HMS) [8] was perceived as a catalyst support for persulfated alumina and zirconia (PAZ) in order to make a new catalyst called UDCaT-4 with enhanced catalytic activity and ordered mesoporosity to minimize the diffusion resist- anceforthereactionofbulkymolecules. The abbrevia- COMMUNICATIONS Adv. Synth. Catal. 2004, 346,389±394 DOI: 10.1002/adsc.200303212 ¹ 2004 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim 389