Effect of W Modification on MoS Surface Edge in the Ethanolysis of Lignin into Platform Chemicals.

A series of metal-doped MoS, including W-, V-, and Re-doped MoS, are prepared via a two-step hydrothermal method, which presents higher activity on the depolymerization of enzymatic hydrolysis lignin (EHL) in ethanol as compared to undoped MoS. At 320 °C for 6 h, the highest overall aromatic monomer yield of 231 mg/g EHL, including alkylphenols (A-Ps) as the main products with a yield of 126.5 mg/g EHL, is obtained over two-step hydrothermally prepared W-doped MoS with the W/Mo molar ratio of 0.1 (Ts-W@MoS). The W-doped MoS sample gives higher enhancement of EHL bio-oils' heating value to 37.1 MJ/kg as compared to Re and V modified MoS. Large distribution of W atoms on the MoS surface in two-step hydrothermally synthesized samples leads to the higher activity of EHL depolymerization than one-step prepared samples. The reduction of W precursors on the MoS surface in the preparation process promotes the generation of more Mo and Mo, which plays important roles in the improvement of EHL depolymerization activity. The effect of the W-doping modification and the stability of W-doped MoS are discussed. The anti-sulfur loss and antioxidant abilities are significantly enhanced after W-doping modification. In the recyclability test, the good incorporation of W atoms with MoS surface and the gradual oxidation of W-based sites improve the balance of catalytic cycles among different Mo-based sites, which results in the increase of catalyst stability.