Hydrogenolysis of lignin-derived aryl ethers to monomers over a MOF-derived Ni/N-C catalyst
A highly efficient Ni/N-C catalyst was synthesized by a facile pyrolysis of Ni-containing metal-organic framework (Ni-MOF), and its catalytic hydrogenolysis performance towards C-O bonds in lignin was evaluated using diphenyl ether (DPE) as a model compound in detail. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses show that the flowerlike nanosheets of Ni-MOF shrink forming a loose and ordered spherical structure during pyrolysis. Under the optimal conditions, DPE was completely converted and the selectivity of monomers (benzene, cyclohexanol and cyclohexane) reached to 99.1%. During the catalytic hydrogenolysis conversion (CHC) of DPE, the direct cleavage of Caromatic-O bond affording benzene and phenol is the major reaction pathway, and low H2 pressure is crucial to increase monomers selectivity. Furthermore, the Ni/N-C-450 shows high hydrogenolysis activity to other lignin-derived aryl ethers, such as benzyl phenyl ether, dibenzyl ether, dinaphthalene ether, benzyl 2-naphthyl ether and 3-methoxyphenol.