Maya, G; Dr.Sugunan, S(Cochin University of Science and Technology, December , 2006)
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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.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
Binitha, N N; Dr.Sugunan, S(Cochin University of Science and Technology, October , 2006)
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Abstract:
Green chemistry boots eco-friendly,natural clays as catalysts in the chemical as well as in the pharmaceutical industry.Industry demands thermal stability,mechanical strength etc for the catalyst and there the modification methods becomes important.Pillaring tunes clays as efficient catalytic templates for shape selective organic synthesis.Here pillared clays are used as promising alternatives for the environmentally hazardous homogeneous catalysts in some industrially important Friedel-Crafts alkylation reactions of arenes with lower alchohols and higher olefins.The layer structure is enhanced upon pillaring and allows the nanocomposite formation with polyaniline to develop today’s nanoscale diameter devices.Present work gives an entry of pillared clays to the world of conducting composite nanofibers.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
Kochurani, George; Dr.Sugunan, S; Dr.Mohanan, P V(Cochin University of Science and Technology, December , 2006)
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Abstract:
The prime intension of the present work was a synthetic investigation of the
preparation, surface properties and catalytic activity of some transition metal
substituted copper chromite catalysts. Homogeneous co-precipitation method is
employed for the preparation of catalysts. Since the knowledge about the structure and
composition of the surface is critical in explaining the reactivity and selectivity of a
solid catalyst. a systematic investigation of the physico-chemical properties of the
prepared systems was carried out. The catalytic activity of these systems has also been
measured in several oxidation reactions of industrial as well as environmental
relevance. The thesis is dedicated to several aspects of chromite spinels giving
emphasis to its preparation, characterization and catalytic performance towards
oxidation reactions.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology