Synthesis-Controlled α- and β-Molybdenum Carbide for Base-Promoted Transfer Hydrogenation of Lignin to Aromatic Monomers in Ethanol

Molybdenum carbide catalysts over activated carbon with different crystal phases were synthesized under controllable carburization atmospheres and temperatures for transfer hydrogenation of Kraft lignin in ethanol to aromatic monomers. Single alpha-MoC1-x and crystal transformation of alpha-MoC1-x to beta-Mo2C are observed under a CH4/H-2 mixture and H-2 carburization atmospheres, respectively. The mixed crystal phases of alpha-MoC1-x and beta-Mo2C with different crystallinities under a N-2 carburization atmosphere exhibit higher activity with a maximum aromatic yield of 0.5163 g/g Kraft lignin when carburized at 700 degrees C. The dehydrogenation reaction and Kraft lignin hydrogenation are proposed to explain the synergistic effect of beta-Mo2C, base, and alpha-MoC1-x for the base-promoted transfer hydrogenation process in ethanol, which is confirmed by in situ Fourier transform infrared analysis. This highly efficient process is suitable for the conversion of different lignin feedstock.