Mechanism of Preferential Hydrogenation of Hydroxymethyl Group to Aldehyde Group in 5-Hydroxymethylfurfural over W2
Wei Tai1, Shuai Fu1, Ting-Hao Liu1
1College of Chemical Engineering, Sichuan University, No.24 South Section 1, Yihuan Road, Chengdu, Sichuan, 610065, P.R. China.
Abstract:
A W4 C2 cluster was used to model a W2 C catalyst with the armchair model of activated carbon support, noted as W4 C2 /AC. Over W4 C2 /AC, the mechanism for the hydrogenation of both -H2 OH and -CHO groups in 5-hydroxymethylfurfural (HMF) was theoretically studied in tetrahydrofuran at GGA-PBE/DNP level. 5-Methylfurfural was the major product from only hydrodehydration of the -CH2 OH group, whereas 2,5-dihydroxymethylfuran was the minor product from the hydrogenation of both -CH2 OH and -CHO groups. The rate-determining steps were concerned with the -C(H)2 -H bond formation for the hydrodehydration of -CH2 OH group, and the -(OH)(H)-H bond formation for the hydrogenation of -CHO group. Kinetically, W-sites promoted the hydrodehydration of -CH2 OH group and inhibited the hydrogenation of -CHO group. This stemmed from the strong Lewis acidity of W-sites, which easily accepted the lone-pair electrons of the oxygen atom in the -C(OH)(H)- group, making -C(OH)(H)-H bond formation hard, and hampering the hydrogenation of the -CHO group.
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