Degradation on hydrogenolysis of soda lignin using CuO/SO42−/ZrO2 as catalyst

Abstract

Lignin was chemically modified with hydrogenolysis as a starting material for polymer and chemical synthesis or as an antioxidant. CuO/SO42−/ZrO2 catalyst was prepared through dipping and roasting method. Lignin degradation was conducted through hydrogenolysis routes with CuO/SO42−/ZrO2 as the catalyst. Structural characterization and antioxidant activity of lignin samples were investigated; the reaction mechanism of lignin degradation was also discussed. The total hydroxyl and phenolic hydroxyl group content of soda lignin were increased by 62.9% and 29.4%, oxygen content was decreased by 10.2%, and Mw was decreased from 7700g/mol to 5500g/mol. The EC50 of soda lignin on DPPH scavenging rate, ABTS+ scavenging rate, and reducing power were decreased by 22.1%, 30.4%, and 9.0%, respectively. The degradation of lignin was probably caused by the degradation of β-O-4 ether linkages and cracking of the methoxy. SO42−/ZrO2 mainly cleaved the β-O-4 linkages, whereas CuO cracked the methoxy group on the benzene ring.