Direct thermochemical liquefaction of microcrystalline cellulose by sub- and supercritical organic solvents

Direct thermochemical liquefaction of microcrystalline cellulose was carried out using sub- and supercritical solvents in a batch reactor. The decomposition efficiency of dodecane and m-xylene widely used in petrochemical industries was compared to that of methanol and 1,4-dioxane. At 400 °C, the conversion in methanol was the highest (92 wt% including gaseous products), but the operating pressure was too high. m-Xylene at the same temperature showed the conversion of 71.5 wt% with a lower number of products and milder pressure. Hydrogen contributed to the increase of the total conversion by 3-8% in m-xylene and methanol, compared with the results without adding any additional gas or with nitrogen pressurization. An acid-modified silica catalyst led to a significant increase of conversion in the supercritical methanol, but its effect was negligible in the aprotic solvents. The product compounds and property of solid residue depended on the supercritical solvents applied. The thermal-treated char after liquefaction in m-xylene, dodecane and 1,4-dioxane was an effective adsorbent for CO₂ adsorption, showing the level comparable with activated carbons.