Highly efficient catalytic hydrogenolysis of lignin model compounds over hydrotalcite-derived Ni/Al2O3 catalysts

Catalytic hydrogenolysis of CO bonds in lignin provides a promising route to produce high value-added biofuels and chemicals. However, designing highly active and stable catalysts for this process is still a challenge. Herein, a series of Ni/Al2O3 catalysts were synthesized by calcination and reduction of layered double hydroxide precursors, and their activities were evaluated in the catalytic conversion of lignin-derived compounds. Diphenyl ether was completely converted with a 100% monomeric selectivity (cyclohexane and cyclohexanol) over the optimized Ni/Al2O3-500 under the optimal conditions of 200 ℃, 0.5 MPa H2 and 1.5 h, indicating the excellent catalytic activity in the cleavage of CO bonds of the catalyst. The excellent catalytic performances of Ni/Al2O3-500 were originated from its relatively large specific surface area, well-developed porosity, small crystallite size, high Ni0 concentration and strong interaction between the active metal and support. The reusability experiments show that Ni/Al2O3-500 possesses a relatively high stability for six reuses. Moreover, various lignin model compounds can be completely converted to corresponding monomeric products over Ni/Al2O3-500, indicating the applicability of this ingenious catalyst. The application of the hydrotalcite-derived Ni-based catalysts with high activity and stability provides a promising approach for the efficient hydrogenolysis of lignin derivatives.