Title
Production of carboxylic acids from alkaline pretreatment byproduct of softwood
Authors
HASSAN RAJA MUDDASSAR KRISTIAN MELIN and JUKKA KOSKINEN

Published Volume 48 Issue 9-10 November-December
Keywords wet oxidation, sawdust, lignocellulosic biomass, waste biomass, partial wet oxidation, alkaline cooking, acid cooking

Abstract
To reduce greenhouse gas emissions more sustainable sources of energy, fuel and chemicals are needed. Lignocellulosic biomass such as wood sawdust could be used for this purpose. The present study is concerned with production of carboxylic acids from spruce sawdust in two stages: firstly, treating sawdust increasing with temperature from 80 °C up to 160 °C with 2 °C/min with alkali during 30 min, and subsequently, treating the liquid part from the first step by partial wet oxidation at 210 °C and oxygen partial pressure of 0.6MPa for 30 min. The carboxylic acids studied include formic, acetic and lactic acids. The objective of this work was to study production of carboxylic acids from a liquid byproduct obtained by pretreatment of sawdust with sodium carbonate or green liquor. The fiber part can be used for pulp or bioethanol production. The yield of acetic acid from spruce was the highest. However, the increase (wt%) in the formation of lactic acid was the highest after pretreatment in the wet oxidation step. The case with the highest addition of Na2CO3 resulted in the greatest yields of acids. For extraction using n-butanol as extraction medium, distribution coefficients ranging from 0.78 to 1.69 were measured for the acids.