Catalytic hydropyrolysis of lignin using NiMo-doped catalysts: Catalyst evaluation and mechanism analysis

NiMo-doped catalysts were investigated for the conversion of lignin to drop-in fuel through catalytic hydropyrolysis. The influence of NiMo-doped catalysts with different carriers and Ni/Mo molar ratios on the hydropyrolysis product distribution were studied using both lignin and lignin model compounds. Two coefficients were proposed to qualitatively evaluate the catalytic performance of NiMo-doped catalysts. Low yield of methane (13.04c%) and high yield of condensable hydrocarbons products (25.82c%) with low selectivity of polyaromatics (4.37%) were obtained at 1.0 MPa H2 and 400 °C catalytic temperature during lignin catalytic hydropyrolysis over Ni1Mo/ZrO2. The hydrodeoxygenation activity of NixMo/ZrO2 depends on Ni0, Mo4+, and Mo3+. The synergistic effect of Ni and Mo promotes the removal of the phenolic methoxy group. The increase in hydrogen pressure tends to make hydrogen to be consumed through hydrocracking and hydrogenation reactions. The influence of Ni1Mo/ZrO2 on evolution of lignin hydropyrolysis volatiles was revealed. Ni shows strong activity in the removal of phenolic hydroxyl groups and benzene ring hydrogenation, while Mo tends to remove phenolic methoxy groups.