KINETICS OF LIQUID-PHASE HYDROGENATION OF CINNAMALDEHYDE OVER A PT-SN/NYLON CATALYST

The kinetics of liquid-phase hydrogenation of cinnamyl alcohol and cinnamaldehyde over Pt/nylon and Sn-Pt/nylon catalysts are investigated. Over both catalysts, hydrogenation of cinnamyl alcohol to hydrocinnamyl alcohol, methylstyrene, and propylbenzene is best described by a network of four parallel consecutive reactions with rate expressions assuming a single active site and saturation of cinnamyl alcohol. The kinetics of cinnamaldehyde hydrogenation over Sn-Pt/nylon in the range 10-60°C are interpreted on the basis of a two-site model, where B sites, associated with Sn, are involved in hydrogenation of cinnamaldehyde and hydrocinnamaldehyde, whereas A sites, associated with Pt, catalyze cinnamyl alcohol hydrogenations. In line with independent chemical evidence, the results indicate strong adsorption of cinnamyl alcohol on Pt sites, which also explains the apparent negative activation energies of some rate constants. © 1990, American Chemical Society. All rights reserved.