One-pot upgrading of coconut coir lignin over high-efficiency Ni2P catalysts

Abstract

The utilization of lignin as a source of phenolic compounds requires highly efficient and selective depolymerization catalysts. Herein, lignin depolymerization was investigated over Ni2P catalysts supported on nitrogen-doped activated carbon (Ni2P/AC_N). The catalysts were prepared by an incipient wetness co-impregnation method followed by reduction with H2 gas. The presence of nitrogen-containing functional groups on the activated carbon surface resulted in the dispersion of Ni2P particles. The good distribution and small crystal size of Ni2P significantly increased the active surface area, which enhanced both the catalytic activity and phenol selectivity. Investigations of the catalytic activity at different reaction temperatures and lignin-to-catalyst ratios using pyrolysis–gas chromatography/mass spectrometry revealed that the highest phenol selectivity of 80% was achieved using the Ni2P/AC_N25% catalyst. The proposed reaction mechanism involves lignin depolymerization via C–O and C–C cleavage with subsequent phenol formation by demethoxylation. Owing to its high phenol selectivity, the Ni2P/AC_N catalyst has good potential for the transformation of lignin to phenol.