Integrated catalytic and electrocatalytic conversion of substituted phenols and diaryl ethers

Electrocatalytic hydrogenation and catalytic thermal hydrogenation of substituted phenols and diary] ethers were studied on carbon-supported Rh. The rates of electrocatalytic hydrogenation increase with increasingly negative potentials, which have been related with the coverage of adsorbed hydrogen. For electrocatalytic and catalytic thermal hydrogen addition reactions, the dominant reaction pathway is hydrogenation to cyclic alcohols and cycloalkyl ethers. The presence of substituting methyl or methoxy groups led to lower rates compared to unsubstituted phenol or diphenyl ether. Methoxy or benzyloxy groups, however, undergo C-O bond cleavage via hydrogenolysis and hydrolysis (minor pathway). The surface chemical potential of hydrogen can be increased also by generating a H-2 atmosphere above the reaction media, supporting the conclusion that thermal and electrochemical routes share the same reaction pathways. (C) 2016 Elsevier Inc. All rights reserved.