Role of ZnO in Ni/ZnO/Al2O3 as catalytic materials for hydrogenation of vegetable oil

Abstract

The potential of porous Ni/ZnO/Al2O3 as a better material for hydrogenation of vegetable oil was studied and compared to Ni/Al2O3 catalyst. Ni/ZnO/Al2O3 and Ni/Al2O3 catalysts were synthesized with co-precipitation method and characterized with ICP-OES, EDXS, XPS, XRD and N2 adsorption-desorption analyses. Performance of the catalysts was assessed in partial hydrogenation of sunflower oil. The formation of crystalline Ni, NiO and ZnO phases from a uniform hydrotalcite phase was clearly detected in the XRD spectra which supports the change in chemistry involved during catalyst synthesis. Albeit having Ni content that is only half of Ni/Al2O3 catalyst, Ni/ZnO/Al2O3 achieved 23 % higher hydrogenation activity. This is attributed to the availability of larger pores (32.9 nm) in Ni/ZnO/Al2O3 which facilitates diffusion of bulky triglyceride molecules during hydrogenation. The incorporation of ZnO in conventional Ni/Al2O3 catalyst was shown to alter the material characteristics by increasing availability of large pores in the material due to ZnO migration, making it a potential alternative material to synthesize catalyst for partial hydrogenation of vegetable oil.