Liquefaction of kraft lignin by hydrocracking with simultaneous use of a novel dual acid-base catalyst and a hydrogenation catalyst.

In this study, a novel catalyst, S2O82--KNO3/TiO2, which has active acidic and basic sites, was prepared and used in lignin hydrocracking with a co-catalyst, Ru/C. Ru/C is an efficient hydrogenation catalyst and S2O82--KNO3/TiO2 is a dual catalyst, which could efficiently degrade lignin. This catalytic hydrogenation system can reduce solid products to less than 1%, while giving a high liquid product yield of 93%. Catalytic hydrocracking of kraft lignin at 320°C for 6h gave 93% liquid product with 0.5% solid product. Most of this liquid product was soluble in petroleum ether (60% of 93%), which is a clear liquid and comprises mainly of monomeric and dimeric degradation products. These results demonstrated that the combination of the two catalysts is an efficient catalyst for liquefaction of lignin, with little char formation (∼1%). This concept has the potential to produce valuable chemicals and fuels from lignin under moderate conditions.