Annu Anna, Varghese; Dr.Mohammed Yusuff,K K(Cochin University of Science & Technology, December , 2008)
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Abstract:
The work presented in this thesis is mainly centered on the
synthesis and characterization of some encapsulated transition metal complexes and the
catalytic activity of the synthesized complexes in certain organic reactions.thesis deals with the catalytic activity of ruthenium-exchanged
zeolite and the zeolite encapsulated complexes of SSC, SOD, SPD, AA, ABA, DMG,
PCO, PCP, CPO and CPP in the hydroxylation of phenol using hydrogen peroxide. The
products were analyzed with a GC to determine the percentage conversion and the
chromatograms indicate the presence of different products like hydroquinone, catechol,benzoquinone, benzophenone etc. The major product formed is hydroquinone. From
the screening studies, RuYSSC was found to be the most effective catalyst for phenol
hydroxylation with 94.4% conversion and 76% hydroquinone selectivity. The influence
of different factors like reaction time, temperature, amount of catalyst, effect of various
solvents and oxidant to substrate ratio in the catalytic activity were studied in order to
find out the optimum conditions for the hydroxylation reaction. The influence of time
on the percentage conversion of phenol was studied by conducting the reactions for
different durations varying from one hour to four hours. There is an induction period
for all the complexes and the length of the induction period depends on the nature of the
active components. Though the conversion of phenol and selectivity for hydroquinone.
increases with time, the amount of benzoquinone formed decreases with time. This is
probably due to the decomposition of benzoquinone formed during the initial stages of
the reaction into other degradation products like benzophenones. The effect of
temperature was studied by carrying out the reaction at three different temperatures,
30°C, 50°C and 70°C. Reactions carried at temperatures higher than 70°C result either in
the decomposition of the products or in the formation of tarry products. Activity
increased with increase in the amount of the catalyst up to a certain level. However
further increase in the weight of the catalyst did not have any noticeable effect on the
percentage conversion. The catalytic studies indicate that the oxidation reaction
increases with increase in the volume of hydrogen peroxide till a certain volume. But
further increase in the volume of H202 is detrimental as some dark mass is obtained
after four hours of reaction. The catalytic activity is largely dependent on the nature of
the solvent and maximum percentage conversion occurred when the solvent used is
water. The intactness of the complexes within the zeolite cages enhances their
possibility of recycling and the activities of the recycled catalysts show only a slight
decrease when compared to the fresh samples .
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology