Aerobic Oxidation of Benzyl Alcohol in a Continuous Catalytic Membrane Reactor

Abstract

A catalytic membrane reactor with a Au-Pd catalyst, impregnated at the inner side of the membrane, was studied in the catalytic oxidation of benzyl alcohol in flow. The reactor comprised of four concentric sections. The liquid substrate flowed in the annulus created by an inner tube and the membrane. The membrane consisted of 3 layers of α-alumina and a titania top layer with 5 nm average pore size. Oxygen was fed on the outer side of the membrane, and its use allowed the controlled contact of the liquid and the gas phase. Experiments revealed excellent stability of the impregnated membrane and selectivities to benzaldehyde were on average > 95%. Increasing the pressure of the gas phase and decreasing liquid flowrates and benzyl alcohol concentration resulted in an increased conversion, while selectivities to benzaldehyde remained constant and in excess of 95%.

Slurry loop tubular membrane reactor for the catalysed aerobic oxidation of benzyl alcohol

“…In this regard, various research groups have tried to address this issue by using either diluted oxygen [28,29], or micro-channel reactors which have been shown to be safe to operate [9,15,[30][31][32]. Keeping the gaseous phase oxidant separate from the organic substrate by using membrane contactors represents an alter-native solution [7,13,33,34]. A membrane that has been used for this purpose is the Teflon AF-2400, first introduced by Ley and co-workers [35] for continuous dissolution of CO2 to synthesise carboxylic acids.…”

Porous Membrane Reactors for Liquid-Phase Heterogeneous Catalysis

“…The membrane configuration affects the membrane area per unit volume and is a key factor in determining the loading of the active components in the catalytic membrane. , The existing membrane configurations are mainly divided into flat-sheet membranes, , tubular membranes, , hollow-fiber membranes, , and nanofiber membranes. − Compared with flat-sheet and tubular membranes, hollow-fiber membranes of the same volume have higher surface areas, which can increase the loading of metal particles. Chen et al prepared Pd/hollow-fiber ceramic catalytic membranes using hollow-fiber ceramic membranes as the carrier.…”

Flow-Through Catalytic Reactors Based on Metal Nanoparticles Immobilized within Porous Polymeric Gels and Surfaces/Hollows of Polymeric Membranes

“…Aerobic oxidation of benzyl alcohol in flow conditions was performed with the help of continuous ceramic membrane reactor inner part of which was impregnated with bimetallic Au-Pd catalyst [55]. The high catalytic activity (operation time is over 670 h), conversion degree (~25%) and selectivity to benzaldehyde (~97%) is probably due to improved oxygen mass transfer to the catalytic sites in contrast to a previously studied [56] packed-bed reactor with an Au-Pd/TiO 2 catalyst.…”