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Keywords:

  • biomass;
  • carbides;
  • heterogeneous catalysis;
  • reaction mechanisms;
  • tungsten

Abstract

A series of Ni-promoted W2C/activated carbon (AC) catalysts were investigated for the catalytic conversion of Jerusalem artichoke tuber (JAT) under hydrothermal conditions and hydrogen pressure. Even a small amount of Ni could greatly promote the conversion of JAT to 1,2-propylene glycol (1,2-PG), whereas the pure W2C/AC catalyst resulted in the selective formation of acetol. The product distribution profiles involving the reaction temperature, time, and H2 pressure indicated that 1,2-PG formed as a result of acetol hydrogenation, which was catalyzed by Ni. Thus, there was a synergy between W2C and Ni, and the best performance yielded 38.5 % of 1,2-PG over a 4 % Ni–20 % W2C/AC catalyst at 245 °C, 6 MPa H2, and 80 min. To understand the reaction process, some important intermediates, such as inulin, fructose, acetol, glyceraldehyde, and 1,3-dihydroxyacetone, were used as the feedstock. Based on the product distributions derived from these intermediates, a reaction pathway was proposed, where JAT was first hydrolyzed into a mixture of fructose and glucose under the catalysis of H+, then the sugars underwent a retro-aldol reaction followed by hydrogenation catalyzed by Ni–W2C.