Efficient and Product-Controlled Depolymerization of Lignin Oriented by Raney Ni Cooperated with Cs x H3 − x PW12O40.

A representative lignin was firstly prepared and characterized as well as an efficient lignin depolymerization process with highly controllable products was presented using Cs-substituted tungstophosphate (CsTP) cooperated with Raney Ni in the present study. The double enzymatic lignin (DEL) was depolymerized efficiently in the temperature range of 250–280 °C. The synergistic effects of Raney Ni with CsTP and temperature on the degradation of lignin were investigated by FT-IR, NMR, GPC, and GC-MS techniques. Under the optimal condition with tandem catalyst at 270 °C for 3 h, the yield of depolymerized DEL was over 70 wt% and phenolic monomers were over 20%. The weight average molecular weight of the lignin was reduced significantly from 15,770 to 1150 g/mol (for aqueous phase lignin) and about 420 g/mol (organic phase lignin). In addition, only a few syringols and cyclohexanols were obtained, indicating that this tandem catalyst facilitates the depolymerization and demethoxylation but prevents hydrogenation of benzene ring of lignin. More importantly, the formation of char was restrained effectively in this process.