Ecopolyols from Spent Coffee Grounds Through Acid Liquefaction Using Polyol: Synthesis and its Optimization

Abstract

Recently, colossal research interests have been paid in the scientific community to synthesize biomass-based polyols due to their availability, sustainability, and low toxicity. Here, in this work, the main objective involves an effective synthesis of eco-polyol from different types of spent coffee grounds biomass (Colombia Narino Supremo, Ethiopia Koke Honey Yirgacheffe G1 and mixed) through an acid-catalyzed liquefaction reaction by employing sulfuric acid and a mixed solvent of different types of polyether polyol and glycerol at a reasonable reaction temperature. Interestingly, Colombia Narino Supremo produced bio-polyol more qualitatively (1 phase) and quantitatively than the other types with the solvent mixture of GPX-600/glycerol. Consequently, the effect of experimental liquefaction conditions on the extent of biomass conversion was optimized by the design of experiments and statistical analysis using a 23-full-factorial design with temperature, time, and acid concentration as the process parameters. Also, the analysis of variance results with a 95% confidence level reveals that acid concentration (catalyst) is the most influencing factor on biomass conversion. However, the achieved maximum conversion was 65.3 wt% at 170 degrees C, 120 min, and 4 wt% of catalyst. The prepared polyol at the optimized condition showed an acid value of 18.6 mg KOH/g polyol, a hydroxyl value of 77.9 mg KOH/g polyol, and a viscosity of 348.2 cPs at 25 degrees C. Thus, this work demonstrates a substrate-specific promising approach to synthesize qualitatively and quantitatively bio-based liquid polyols using acid liquefaction at a reasonable temperature.