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Characterization of surface sulfate species on mixed metal oxide catalysts
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Acharya, Shreyas. Characterization of surface sulfate species on mixed metal oxide catalysts. Retrieved from https://doi.org/doi:10.7282/T37M0C2X

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TitleCharacterization of surface sulfate species on mixed metal oxide catalysts
NameAcharya, Shreyas (author); Tsilomelekis, George (chair); Rutgers University; School of Graduate Studies
Date Created2017
Other Date2017-10 (degree)
SubjectChemical and Biochemical Engineering, Raman spectroscopy, Oxides
Extent1 online resource (x, 52 p. : ill.)
DescriptionSolid 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 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 Total Reflection (ATR-FTIR) and in-situ Raman spectroscopy using high temperature reaction chamber. The results show that the molecular structure of the surface sulfate species varies significantly with increasing temperature as underscored by the changes of S=O vibrational bands. It was found that the sulfated species getting attached to the catalyst support can majorly be present as bidentate, tridentate and polymeric species and are a function of the temperature as well as the Sn:Zr ratio. Tuning the molecular structure of the sulfated species could potentially alter the acidic properties of the catalysts as indicated by the Lewis/Bronsted acid sites. Lastly, it was found that the crystalline phases of the the regenerated catalyst remain unaffected along with the sulfated groups.
NoteM.S.
NoteIncludes bibliographical references
Noteby Shreyas Acharya
Genretheses, ETD graduate
Persistent URLhttps://doi.org/doi:10.7282/T37M0C2X
Languageeng
CollectionSchool of Graduate Studies Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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