Selective Conversion of Lignin Catalyzed by Palladium Supported on N-Doped Carbon

Abstract

Highly selective conversion of lignin is essential to enable high-value utilization of lignin. Herein, we have prepared a palladium supported on N-doped carbon catalyst modified by 1,3,5-trimethylbenzene (TMB). The Pd nanoparticles are better dispersed on the TMB-modified catalyst than on the original catalyst. Therefore, the catalyst modified by TMB is more effective than the original catalyst in selectively converting lignin. When the organosolv lignin is catalyzed by 3 wt % Pd/CBFS-26-TMB (1:2) at 280 °C for 5 h, the yield of phenolic acid is 25.71 wt % and the biochar yield is only 4.5 wt %. Significantly, 52.59% of the phenolic acid monomers are 4-hydroxy-3,5-dimethoxyphenylacetic acid with a yield of 13.52 wt %. Thus, the catalyst 3 wt % Pd/CBFS-26-TMB (1:2) can effectively break the C–C and C–O bonds in the β–O–4 structure to convert lignin into 4-hydroxy-3,5-dimethoxyphenylacetic acid. We have also discussed the possible mechanism of lignin conversion into main products. This provides an essential approach for the high-value utilization of lignin.