Selective production of 1,2-propylene glycol from Jerusalem artichoke tuber using Ni-W(2) C/AC catalysts.

A series of Ni-promoted W(2) C/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 W(2) C/AC catalyst resulted in the selective formation of acetol. The product distribution profiles involving the reaction temperature, time, and H(2) pressure indicated that 1,2-PG formed as a result of acetol hydrogenation, which was catalyzed by Ni. Thus, there was a synergy between W(2) C and Ni, and the best performance yielded 38.5% of 1,2-PG over a 4%Ni-20%W(2) C/AC catalyst at 245°C, 6 MPa H(2) , 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-W(2) C.