Abstract
Microwave assisted synthesis of 5-hydroxymethylfurfural (HMF) using hydrolysate produced from dilute acid hydrolysis of bamboo with low transition temperature mixture (LTTM) as a green solvent was performed. Bamboo was a fast-growing plant with high cellulose content in the biomass, which made it suitable as the raw material for HMF production. LTTM was produced from hydrogen bond acceptor and donor, which in this study were choline chloride and malic acid, respectively. Microwave irradiation was used as it is faster and energy saving than conventional heating methods. A two-factors three-levels full factorial design with temperature and reaction time as the manipulating variables was employed and a linear model was constructed with R2 of 0.9640 and p-value of 0.0115, indicating good reliability and significant. ANOVA analysis informed that only the temperature was significant, where the optimum point was 120 °C and 10 min with HMF yield of 10.7951 %. A follow up study was conducted at 140 °C and 5 min and had found that the system established an equilibrium of temperature at 120 °C between the heat loss by evaporation of water and heat gained by microwave irradiation. The shorter reaction time also resulted in higher HMF yield of 10.9410 %, possibly due to lower degree of unwanted side reaction (i.e., rehydration of HMF into levulinic acid). This study shows that it is possible to directly utilise the hydrolysate of bamboo without further separation of glucose in conversion into HMF, a valuable green and sustainable platform chemical.
