Green process for hydrogenation of methyl ricinoleate to methyl 12-hydroxystearate over diatomite supported Cu/Ni bimetallic catalyst

Abstract

A series of diatomite supported Cu/Ni bimetallic catalysts were prepared using the co-impregnation method to improve the efficiency and selectivity toward methyl 12-hydroxystearate in the hydrogenation of methyl ricinoleate. The catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (H2-TPR). All the characterization results verified the formation of highly dispersed Cu/Ni alloy on support. Moreover, by subtly regulating the Ni/Cu molar ratio as well as the reaction parameters, the hydrogenation of methyl ricinoleate to methyl 12-hydroxystearate proceeded efficiently and selectively, affording 97% yield of methyl 12-hydroxystearate and nearly equivalent conversion of methyl ricinoleate under 2 MPa H2 pressure and at 130 °C in 4 h with only 1 wt% of the catalyst Ni7Cu1/diatomite (based on methyl ricinoleate). Besides, the supported Cu–Ni bimetallic catalyst is stable during recycle and reuse. After five cycles of reuse, much catalytic activity is still preserved. Therefore, this low-cost and stable bimetallic catalyst would be promising for the hydrogenation of methyl ricinoleate to methyl 12-hydroxystearate, representing an example of green catalysis for efficiently conversion of biomass to value-added chemicals and materials.