Controlling Hydrothermal Reaction Pathways To Improve Acetic Acid Production from Carbohydrate Biomass

TLDR

Conventional wet oxidation of carbohydrates yields little acetic acid because formic acid is the primary product and acetic acid arises only from oxidation of aldose dehydration products, whereas a two‑step process can enhance yield. The study proposes a two‑step hydrothermal process to improve acetic acid production from carbohydrate biomass. The process first accelerates formation of HMF, 2‑FA, and lactic acid, then oxidizes these intermediates with added oxygen to produce acetic acid. The two‑step method achieved high‑yield, high‑purity acetic acid, with furans and lactic acid accounting for roughly 85‑90 % of the conversion and contributing to the yield in a 2:1 ratio.

Abstract

A two-step hydrothermal process to improve the production of acetic acid was discussed. The first step was to accelerate the formation of 5-hydroxymethyl-2-furaldehyde (HMF), 2-furaldehyde (2-FA), and lactic acid (LA), and the second step was to further convert the furans (HMF, 2-FA) and LA produced in the first step to acetic acid by oxidation with newly supplied oxygen. The acetic acid obtained by the two-step process had not only a high yield but also better purity. The contribution of two pathways via furans and LA in the two-step process to convert carbohydrates into acetic acid was roughly estimated as 85-90%, and the ratio of the contributions of furans and LA to yield acetic acid was estimated as 2:1. The fact that WO of carbohydrates is not capable of producing a large amount of acetic acid, while the two-step process can enhance the acetic acid yield, can be explained because formic acid is a basic product of direct oxidation of carbohydrate, and acetic acid in WO of carbohydrates may come from the oxidation of dehydration products of aldose.