Characterization of surface sulfate species on mixed metal oxide catalysts

Shreyas Acharya
Solid acid and super acid catalysts are promising alternatives for very important reactions usually catalyzed industrially by homogeneous acid reactions. Sulfated metal oxides are among many examples of solid super acids which work well for acid catalyzed reactions. These catalysts have applications in isomerization, alkylation, acylation and oxidative dehydrogenation reaction. A characteristic example encompasses products from tert-butylation of phenol which have tremendous importance in
more » ... importance in chemical, petrochemical as well as pharmaceutical industry. In spite of significant amount of work devoted in this area, the catalysts being commercially used have low yields. Hence we channel our efforts in enhancing the productivity of the alkylation of phenol reaction by using sulfated metal oxides as it has shown in our preliminary work improved catalytic activity. In this work, we focus on the preparation and characterization of sulfated mixed metal oxides. Specifically, sulfated-Tin-Zirconium oxides (STZ) are produced by coprecipitation method using hydrated Zirconium Oxychloride(ZrOCl2.8H2O) and Tin Chloride(SnCl4.5H2O) as metal precursors and ammonia as the precipitating agent. Different proportions of hydrous tin and zirconium oxides (molar ratios of 1:10,1:1 and 10:1) are synthesized. Sulfation of the prepared hydrous oxides is performed using wet impregnation method with 1M and 0.5M sulfuric acid solution. Calcination of the prepared sulfate mixed hydroxides follows at 600oC. Our work focuses on the incorporation of vibrational spectroscopic teqniques at the individual steps of the synthesis procedure. To that end, first we utilize Raman spectroscopy to study the speciation of the metal salts precursors in water and at various pH range. The broad spectral envelope is assigned to specific vibational modes of the various species. XRD analysis is done to understand the crystalline phases of the catalyst. Additionally, we study the temperature evolution of the deposited sulfated species by means of in-situ Attenuated Tot [...]
doi:10.7282/t37m0c2x fatcat:57dbpatxrrbjrgkcpgaqbkngtq