Ni nanoparticles entrapped in nickel phyllosilicate for selective hydrogenation of guaiacol to 2-methoxycyclohexanol

Abstract

Selective hydrogenation of guaiacol to valuable chemicals is especially attractive for the upgrading of lignin-derived platform compounds. However, the synthesis of 2-methoxycyclohexanol over non-noble metal catalyst is a great challenge under mild condition. In this work, we have designed a confined nano Ni-based catalyst by ammonia evaporation hydrothermal method (AEH) with Ni nanoparticles tightly entrapped in fibrous nickel phyllosilicate (Ni-PS) box. This special structure results in highly dispersed Ni nanoparticles with stable state, and facilitates the activation of H2. Meanwhile the remaining Ni-PS contains large numbers of Lewis acid sites, enhances the adsorption capacity of guaiacol, and greatly promotes its catalytic performance. Ni/SiO2-AEH shows much higher intrinsic activity (TOF, 87.4 molguaiacol/(molNi.h)) than Ni/SiO2 prepared by conventional impregnation (IMP) (49.7 molguaiacol/(molNi.h)) and deposition-precipitation (DP) methods (69.9 molguaiacol/(molNi.h)). Moreover, Ni/SiO2-AEH gave an excellent yield of 2-methoxycyclohexanol (95.5%), which is the highest yield ever reported. Based on experimental results, reaction pathway of guaiacol hydrogenation on Ni/SiO2-AEH is put forward.