Production of phenols from catalytic conversion of lignin over a tungsten phosphide catalyst

Abstract

Production of phenols from alkaline lignin over a tungsten phosphide catalyst in a hot compressed water–ethanol mixed solvent is examined. The small molecular products mainly consist of five phenols, i.e. 2-methoxy-phenol (guaiacol), 2-methoxy-4-methyl-phenol, 2-methoxy-4-ethyl-phenol, 2-methoxy-4-acetyl-phenol and 2-methoxy-4-propyl-phenol. The activated carbon supported catalyst gives the highest overall phenols yield, 67.0mg/g lignin, while the catalysts with other supports exhibit much lower overall yield. Ni and Fe doping of the tungsten phosphide improve phenols selectivity but lower the overall phenols yield. In addition, the result of MALDI-TOF analysis indicates that a longer reaction time leads to the formation of polymers with molecular weights of m/z 701–1040 due to the re-polymerization reactions. Therefore, the yield of the monophenols decreases with the increase of the reaction time.