Liquefaction of Softwood Bark towards Biochemicals and Biofuels

Abstract: The energy consumption in the world is increasing at the same time as the fossil fuel resources are limited. This is causing a rising interest in renewable energy sources over the world. To reduce dependency on fossil fuel sources biomass is an excellent alternative.SCA Östrand pulp mill in Timrå is having one of the largest industrial investments made in Sweden. The production capacity will double, resulting in the largest production line for bleached softwood kraft pulp in the world. This level will be reached in 2020. The large expansion has given an interest for a possible localization of a biorefinery in connection with the existing pulp mill. This project was one of the first investigations towards building a biorefinery at SCA Östrand pulp mill.The aim of this project was to investigate liquefaction of bark from spruce from SCA Ortviken paper mill by solvent solubilization of lignin. It was desirable to hydrolyze all cellulose in the media used, with or without the use of solid catalyst. Many different catalysts together with solvents were investigated with the goal to find the best suitable combination to be used in a biorefinery of softwood bark. The investigated solvents were para-toluenesulfonic acid and methanol. Today bark is usually burned for heat recovery at the pulp and paper mill.Analysis of extractives, ash metals and carbohydrates of the bark were performed before any trials. Reactions took place in a 0.3 L stainless steel Parr reactor with high temperature and pressure. Several trials (21 in total) were made with or without catalyst and most of them with methanol as solvent. Two catalysts were studied in more detail, zeolite ZSM-5 and zeolite Beta_250. For ZSM-5 mainly methyl esters and steroid hydrocarbons were formed. Reactions with Beta_250 resulted in monolignols, shorter methyl esters and shorter organic acids compared with ZSM-5.The result showed most liquid product and lowest bark and coke residue from zeolite ZSM-5 and Ni/C-catalyst with 0.16 g respectively 0.21 g bio-oil, both from 1 g of softwood bark.