Selective depolymerization of lignin catalyzed by nickel supported on zirconium phosphate

Abstract

Lignin selective depolymerization is a crucial step in high-value utilization of this natural aromatic polymer. In this study, we provide a novel and efficient hydrogenolysis process for organosolv lignin selective decomposition and char elimination over non-noble metallic nickel supported on zirconium phosphate (Ni/ZrP). With the optimized catalyst of 15%Ni/ZrP-2.0, 87.3% lignin conversion could be obtained with less than 5.2% char formation under mild condition of 260 °C for 4 h. Product analysis demonstrates that 15.1 wt% phenolic monomer yield is given at the relatively low hydrogen pressure of 2.0 MPa. In particular, 40.4% of these volatile products were identified to be para ethyl phenol (a yield of 6.1 wt%), a versatile compound which is currently originating from the petrochemical industry. Further comparative structure characterization of the original and regenerated lignin shows that the efficient cleavage of carbon bonds between C8 and C9 in the p-coumarate moiety of H-lignin (pCA8 unit) is mainly responsible for this excellent yield of para ethyl phenol. In addition, this process yields 48 wt% nonvolatile products, which mainly consist of phenolic dimers and trimers, indicating its great potential to be a good starting material for high quality aromatic fuel production via simple upgradation techniques.