Free-radical conversion of a lignin model compound catalyzed by Pd/C

Abstract

Efficient cleavage of a C–O bond in lignin and its model compounds is of great importance for transformation of lignin into fuel and value-added chemicals. In this work, we explored the transformation of a lignin model compound benzyl phenyl ether (BPE) at 150 °C by using Pd/C as the catalyst under an argon atmosphere in the presence of Na₂CO₃ and N-methyl-2-pyrrolidone (NMP). The effects of different reaction parameters such as the amounts of Pd/C, Na₂CO₃ and NMP as well as reaction times were investigated. It was found that Pd/C played a key role in the conversion of BPE. At the same time, Na₂CO₃ and NMP also promote the transformation effectively. The yields of phenol and toluene reached 71.6% and 50.4%, respectively. Analytical results of electron paramagnetic resonance (EPR) indicated that the reaction proceeded through a free-radical reaction mechanism. Control experiments indicated that direct pyrolysis of BPE was the main route to generate the target products.