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Studies in hydrocarboxylation of styrene and derivatives using palladium complex catalysts
Li, Yuanchun
Li, Yuanchun
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Abstract
Carbonylation of aryl olefins and alcohols using homogeneous Pd catalysts has gained considerable interest due to their important applications in the synthesis the non-steroidal anti-inflammatory drugs consisting of 2-arylpropionic acids (e.g. Ibuprofen®, Naproxen®). In this work, different homogeneous palladium catalysts were compared for their performances in the hydrocarboxylation of styrene to identify the best performing catalyst system using Pd(pyca)(PPh3)(OTs) as a precursor, which shows above 99% regio-selectivity to 2-phenylpropionic acid as well as high activity. Therefore, this work mainly investigated the kinetics of hydrocarboxylation of styrene using Pd(pyca)(PPh3)(OTs)/PPh3/TsOH/LiCl catalyst system. Particularly, parametric study was carried out to understand the effects of different reaction parameters on the rate of hydrocarboxylation in a batch reactor as well as the concentration-time profiles. For interpretation of the reaction kinetics, a molecular level description of the reaction mechanism (catalytic cycle) was proposed to explain the unique observation of induction period at lower pressures of CO. The experimental concentration-time data for styrene, water and acid products were used to simulate the intrinsic rate parameters using an optimization program. The proposed reaction mechanism based on a Pd-hydride complex as an intermediate active species well explains the experimental data at different temperatures. The approach of micro-kinetic modeling does not require assumption of a rate determining step and provides good description of the complex trends with respect to reaction and catalyst parameters over a wide range of conditions. The approach is also useful to discriminate different reaction mechanisms and obtain intrinsic kinetic parameters for design and scale-up of reactors.
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Date
2010-07-15
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University of Kansas
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Chemical engineering