Vapor‐phase selective hydrogenation of citral over Pd/bentonite: effect of reduction method

Abstract

AbstractBACKGROUND: Well‐dispersed nanoparticles of palladium were synthesized by wet impregnation technique over bentonite followed by three different reduction methods (H2 or NaBH4 or ethanol) and characterized by transmission electron microscopy, X‐ray diffraction, temperature‐programmed reduction and atomic absorption spectroscopy. Hydrogenation of citral over Pd‐supported bentonite catalysts was studied in vapor phase using a micro‐reactor. The effect of reduction method and metal loading on the conversion of citral and selectivity towards nerol and geraniol were examined.RESULTS: Among the catalysts evaluated in the vapor phase, Pd/bentonite reduced by ethanol was found to give the highest conversion and Pd/bentonite reduced by NaBH4 was found to give the highest selectivity towards nerol and geraniol. This may be attributed to the smallest particle size of Pd in the former catalyst and presence of boron species on the latter catalyst, respectively.CONCLUSION: The presence of boron in proximity to palladium particles polarized CO bond and helped CO adsorption, thereby yielding nerol and geraniol (the unsaturated alcohols). Copyright © 2008 Society of Chemical Industry