Catalytic Oxidation of Lignite to Carboxylic Acids in Aqueous H5PV2Mo10O40/H2SO4 Solution with Molecular Oxygen

Abstract

Carboxylic acids (CAs) are considered as an important group of chemicals and are widely used in the chemical industry. The production of CAs via oxidation of lignite is a promising industrial process. In the present work, we found that H5PV2Mo10O40 (HPA) was beneficial to catalytic oxidation of lignite by O2 in aqueous H2SO4 solutions to produce CAs. The effects of HPA concentration, H2SO4 concentration, reaction temperature, initial O2 pressure, and reaction time on lignite conversion and CA yield were studied. The catalytic oxidation of lignite in aqueous HPA/H2SO4 solutions with O2 can yield 56.9 wt % CAs, including 33.5 wt % formic acid, 14.4 wt % acetic acid, 1.5 wt % succinic acid, 1.1 wt % oxalic acid, and 6.4 wt % benzene carboxylic acids (BCAs, including 12 types) at 170 °C and 3 MPa for 60 min. In this catalyst system, the existence of H2SO4 can change the catalytic activity of HPA, and the synergistic effect of HPA and H2SO4 can significantly promote the production of CAs. VV can oxidize lignit...