Solvent-mediated selective hydroconversion of benzyloxybenzene over a Ni/β40 catalyst

Abstract

During biomass conversion, solvent types often play an important role in determining product selectivity and reaction mechanisms. Nevertheless, solvent function remains poorly understood. Herein, Ni/β40 was prepared by a slightly modified deposition-precipitation method and used for the catalytic hydroconversion (CHC) of benzyloxybenzene (BOB) to dicyclohexylmethane (DCHM) or toluene and phenol mediated by solvent types. The results show that solvent types, atmospheres, and Ni20/β40 synergistically control product regulation. In n-hexane (H), DCHM was first produced with the selectivity of 94.5% under the optimum conditions (180 °C, 2 MPa H2, and 4 h). In isopropanol (IP), toluene and phenol were unique products under the optimal conditions (180 °C, 0.5 MPa H2, and 4 h). The characterizations of Ni20/β40 and variation of product distributions from the CHC of BOB demonstrates that BOB conversion to DCHM in H via the >CH-O- bond cleavage induced by H+ addition, benzylium addition to ortho and para positions of phenol, H…H transfer to the resulting 2-benzylphenol and 4-benzylphenol, dehydroxylation of 2-benzylcyclohexanol and 4-benzylcyclohexanol produced, together with benzene rings hydrogenation. By contrast, conversion of BOB to toluene and phenol in IP only depends on the cleavage of >CH-O- bond induced by H+ addition. Furthermore, Ni20/β40 exhibites splendid reusability.