Production of Benzene Carboxylic Acids and Small-Molecule Fatty Acids from Lignite by Two-Stage Alkali-Oxygen Oxidation

Abstract

Carboxylic acids are widely used in industry as a kind of important chemical materials, and it is very promising to produce carboxylic acids from lignite. The traditional alkali-oxygen oxidation of lignite does not consider the complex structure of lignite, and the structures with different reactivities are treated under identical and harsh reaction conditions, resulting in a low yield of carboxylic acids. We propose a two-stage oxidation process of lignite to increase the yield and mitigate the harsh reaction conditions. First, lignite was extracted using a NaOH aqueous solution to yield two parts (extract and residue) with different reactivities. The extract and residue then were oxidized separately with alkali-oxygen oxidation under different conditions. In this way, high yields of benzene carboxylic acids (BCAs, 12 types) and small-molecule fatty acids (SMFAs) could be obtained. The extraction conditions and the alkali-oxygen oxidation conditions of the extract and the residue were investigated. Compa...