Theoretical Investigation Into The Reaction Mechanisms Of Benzyl Alcohol With Dimethyl Carbonate Over A Faujasite Zeolite Catalyst
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Date
2012-03
Authors
Chong, Shu Xian
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Benzyl methyl ether (BME) compounds are largely synthesized by the chemical
industry for use as a starting material for the synthesis of other organic compounds.
In order to achieve the target of green chemistry, BME can be synthesized from
benzyl alcohol and dimethyl carbonate (DMC) using a zeolite catalyst. DMC is a
good methylating and carboxymethylating agents that is, in contrast to other such
agents, a relatively non-toxic compound. The target of this study is to investigate the
possible reaction mechanisms for the reaction of benzyl alcohol and DMC over the
zeolite catalyst. In this study, the methylation and carboxymethylation reactions of
benzyl alcohol over a 3T quantum cluster of zeolite was investigated by density
functional theory (DFT). A 36T extended framework was investigated by the
ONIOM approach, with Hartree-Fock (HF), DFT, and embedded with the UFF
molecular mechanic and PM3 semiemperical approach. Both frameworks revealed
two pathways for the methylation reaction, the first involving two transition states
(TSs) and the second only a single TS. Methylation via the two-TS pathway was
found to be kinetically more stable than the single-TS pathway whilst the
methylation reaction was kinetically favored over the carboxymethylation reaction.
The ONIOM(DFT:UFF) and ONIOM(DFT:PM3) have shown similar results, while
the ONIOM(HF:UFF) has shown similar optimized structures and overestimated
energies. The rate constant for the studied reactions were calculated by using the
transition state theory and the rate determining step was determined.
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Keywords
The reaction mechanisms Of benzyl alcohol , with dimethyl carbonate over a Faujasite zeolite catalyst