Abstract
H3PO4-treated titania was found to be effective solid acid catalyst for converting 1,3-dihydroxyacetone (triose sugar) into lactic acid in water. The reaction consists of dehydration of 1,3-dihydroxyacetone into pyruvaldehyde, followed by hydride shift of pyruvaldehyde into lactic acid. Homogeneous and Heterogeneous Brønsted acids including H3PO4 mainly produced pyruvaldehyde, indicating that Brønsted acids are not active for hydride shift of pyruvaldehyde into lactic acid. FT-IR measurement using pyridine as a basic molecular probe revealed that H3PO4-treated titania has not Brønsted acid sites but water-tolerant Lewis acid sites on the surface. High catalytic performance of titania catalyst is therefore attributed to water tolerant Lewis acid sites that proceed effectively on both dehydration and hydride shift reactions.
