Conversion of ethanol fermentation stillage into aliphatic ketones by two-step process of hydrothermal treatment and catalytic reaction

Abstract

Many countries develop ethanol from biomass by fermentation because ethanol is one of the current alternative fuels in use. This process uses biomass such as corn, wheat, and irregular wheat as feedstock. Production of ethanol from cereal grains generates stillage as a fermentation residue. The stillage mainly contains proteins and unconverted carbohydrates. Both of these components have a potential to produce organic chemicals with lower molecular weight. The stillage derived from fermentation of irregular wheat for ethanol production was converted into aliphatic ketones by a two-step process of hydrothermal treatment followed by catalytic reaction over a ZrO2-FeOX catalyst. During hydrothermal treatment, the stillage was converted into oxygen-containing liquid tar that consisted of cyclic compounds containing nitrogen atoms, aromatics, ketones, ethers, esters, carboxylic acids, aldehydes, and some undetectable compounds. The ZrO2-FeOX has been considered as an appropriate catalyst to produce aliphatic ketones from oxygen-containing tar. Catalytic reaction of the liquid tar over the catalyst, cyclic compounds containing nitrogen atoms were converted into heavy components because of polymerization reaction. Meanwhile, esters and carboxylic acids were converted into aliphatic ketones via hydrolysis, oxidation, and ketonization reactions. As a result, aliphatic ketones were selectively produced from the fermentation stillage by the two-step process.