Spent coffee grounds as a renewable source for ecopolyols production

BACKGROUNDBased on the biorefinery concept, the main focus of this work was the increase in value of spent coffee grounds via an acid liquefaction process using polyhydric solvents in the presence of sulfuric acid, at moderate temperature. For that purpose the effect of temperature, sulfuric acid concentration and time on biomass conversion was studied using design of experiments combined with statistical analysis. RESULTSThe ANOVA results (95% confidence level) showed that temperature is the factor with most influence on biomass conversion, within the studied range, while reaction times above 40 min don't seem to bring significant advantages. The maximum conversion obtained in this study was 70 wt% which was achieved at 160 degrees C, 4 wt % of catalyst and 80 min. The polyol obtained using these conditions presented a hydroxyl number value of 199 mg (KOH)/g (polyol) and a viscosity of 390 cP, at 25 degrees C. CONCLUSIONThis work showed that it is possible to convert spent coffee grounds into liquid polyols via an acid liquefaction process at moderate temperature and autogeneous pressure. These polyols have similar properties to those of petroleum-based polyols typically used in the polyurethane foam industry. (c) 2014 Society of Chemical Industry