Lactic acid production from glucose by using divalent transition metal oxide catalyst on magnesium oxide support without alkaline solution

Abstract

This research was studied the effects of the type of divalent metal oxide (Cu, Co, Ni, and Zn) supported on magnesium oxide catalyst using the hexadecyltrimethylammonium bromide (CTAB) as the capping agent with metal loading at 1.5, 5, and 10 mmol/gram-catalyst on lactic acid production from glucose. To achieve the lactic acid production of lower reactor corrosion rate and being environmentally friendly, the reaction was performed in an alkali additive-free environment. The catalysts were synthesized by hydrothermal method and characterized by various techniques. The XRD pattern of spent CuCTAB/MgO and CoCTAB/MgO catalyst showed the reduced metal species indicated the used of oxygen atom from metal oxide for the reaction. While the NiCTAB/MgO and ZnCTAB/MgO showed peak of metal hydroxide in spent catalyst which suggested that the chemisorption of water molecule at the catalyst surface has been occurred. The glucose conversion from various catalysts were related to the amount of metal leaching from the ICP result, which indicated that the metal ion and basicity from metal hydroxide in the solution has very effected to the glucose conversion. While, the selectivity of lactic acid was consistent with basicity from acid titration suggested that the basicity of catalyst surface has an important role to the selectivity of lactic acid.