Catalysis by Transition Metal Modified Ceria and Ceria-Zirconia Mixed Oxides Prepared via Sol-Gel Route

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Catalysis by Transition Metal Modified Ceria and Ceria-Zirconia Mixed Oxides Prepared via Sol-Gel Route

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dc.contributor.author Maya, G
dc.contributor.author Dr. Sugunan, S
dc.date.accessioned 2012-02-14T10:02:45Z
dc.date.available 2012-02-14T10:02:45Z
dc.date.issued 2006-12
dc.identifier.uri http://dyuthi.cusat.ac.in/purl/2748
dc.description Department of Applied Chemistry, Cochin University of Science and Technology en_US
dc.description.abstract The aim of catalysis research is to apply the catalyst successfully in economically important reactions in an environmentally friendly way. The present work focuses on the modification of structural and surface properties of ceria and ceria-zirconia catalysts by the incorporation of transition metals. The applications of these catalysts in industrially important reactions like ethylbenzene oxidation, alkylation of aromatics are also investigated.Sol-gel method is effective for the preparation of transition metal modified ceria and ceria-zirconia mixed oxide since it produces catalyst with highly dispersed incorporated metal. Unlike that of impregnation method plugging of pores is not prominent for sol-gel derived catalyst materials. This prevents loss of surface area on metal modification as evident for BET surface area measurements.The powder X-ray diffraction analysis confirms the cubic structure of transition metal modified ceria and ceria-zirconia catalysts. The thermal stability is evident from TGA/DTA analysis. DR UV-vis spectra provide information on the coordination environment of the incorporated metal. EPR analysis ofCr, Mn and Cu modified ceria and a ceria-zirconia catalyst reveals the presence of different oxidation states of incorporated metal.Temperature programmed desorption of ammonia and thermogravimetric desorption of 2,6-dimethyl pyridine confirms the enhancement of acidity on metal incorporation. High a-methyl styrene selectivity in cumene cracking reaction implies the presence of comparatively more number of Lewis acid sites with some amount of Bronsted acid sites. The formation of cyclohexanone during cyclohexanol decomposition confirms the presence of basic sites on the catalyst surface.Mn and Cr modified catalysts show better activity towards ethylbenzene oxidation. A redox mechanism through oxometal pathway is suggested.All the catalysts were found to be active towards benzylation of toluene and a-xylene. The selectivity towards monoalkylated products remains almost 100%. The catalytic activity is correlated with the Lewis acidity of the prepared systems.The activity of the catalysts towards methylation of phenols depends on the strength acid sites as well as the redox properties of the catalysts. A strong dependence of methylation activity on the total acidity is illustrated. en_US
dc.language.iso en en_US
dc.publisher Cochin University of Science and Technology en_US
dc.subject Ceria en_US
dc.subject Ceria-Zirconia en_US
dc.subject Catalysis en_US
dc.subject Sol-gel Route en_US
dc.subject Oxidation en_US
dc.subject Friedel Crafts Benzylation en_US
dc.subject Toluene en_US
dc.subject Methylation en_US
dc.subject Phenol en_US
dc.subject Ethylbenzene en_US
dc.subject Applied Chemistry en_US
dc.title Catalysis by Transition Metal Modified Ceria and Ceria-Zirconia Mixed Oxides Prepared via Sol-Gel Route en_US
dc.type Thesis en_US


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