Selective valorization of lignin to phenol by direct transformation of Csp2-Csp3 and C-O bonds.

Phenol is an important commodity chemical in the industry, which is currently produced using fossil feedstocks. Here, we report a strategy to produce phenol from lignin by directly deconstructing Csp2-Csp3 and C-O bonds under mild conditions. It was found that zeolite catalyst could efficiently catalyze both the direct Csp2-Csp3 bond breakage to remove propyl structure and aliphatic β carbon-oxygen (Cβ-O) bond hydrolysis to form OH group on the aromatic ring. The yield of phenol could reach 10.9 weight % with a selectivity of 91.8%. In this unique route, water was the only reactant besides lignin. A scale-up experiment showed that 4.1 g of pure phenol could be obtained from 50.0 g of lignin. The reaction pathway was proposed by a combination of control experiments and density functional theory studies. This work opens the way for producing phenol from lignin by direct transformation of Csp2-Csp3 and C-O bonds in lignin.