Improved Hydrodeoxygenation of Phenol to Cyclohexane on NiFe Alloy Catalysts Derived from Phyllosilicates

A phyllosilicate-derived NiFe/SiO2 catalyst (NiFe/SiO2-AE) was successfully prepared by the ammonia evaporation method and applied in the hydrodeoxygenation of phenol to cyclohexane. Another two catalysts were also prepared for a comparison by impregnation (NiFe/SiO2-IM) and deposition-precipitation (NiFe/SiO2-DP) methods, respectively. It was found that Ni-Fe alloy, the active sites for the hydrogenolysis of C-O bond, can be obtained by the reduction of NiFe2O4 (IM) or phyllosilicate (DP and AE) by H-2. The AE strategy can generate more phyllosilicate structure, which improves the dispersion of both Ni-Fe alloy and metallic Ni sites and allows the formation of more interface between these two kinds of sites as well. Therefore, the NiFe/SiO2-AE exhibits a significantly high catalytic performance in the HDO of phenol to cyclohexane. Moreover, the turnover frequency of Ni-Fe alloy sites over NiFe/SiO2-AE catalysts is much higher than those of other two catalysts. It is suggested that the enhanced synergy between the two kinds of active sites in the adsorption of C-O groups and hydrogen molecules ensures the superior intrinsic activity in HDO process.