Oxidation of Xiaolongtan lignite to oxygen-containing chemicals over NaVO3-H2SO4 by introducing methanol to suppress the formation of CO2

The production of oxygen-containing chemicals (OCCs) from lignite via catalytic oxidation with O2 is an effective method. However, in the process, a significant amount of CO2 is generated, reducing the utilization of carbon. To suppress CO2 production, we introduced methanol into the NaVO3-H2SO4 aqueous solution to produce OCCs from lignite. The yields of OCCs (mainly including carboxylic acids, methyl formate, and methylal) and CO2 are 42.5% and 26.8%, respectively, at a methanol content of 30 vol.%, while these in NaVO3-H2SO4 aqueous solution are 24.2% and 56.3%, respectively. We also found that methylal is produced via the acetalization between methanol and aldehyde, and the reaction changes the pathway of aldehyde conversion into carboxyl. Meanwhile, ester is generated via esterification between methanol and carboxyl group, protected against decarboxylation to CO2. These acetalization and esterification suppress CO2 generation. Introducing methanol into NaVO3-H2SO4 aqueous solution improves the utilization of carbon in lignite significantly.