Effect of Ultrasonic-Assisted Acid Pretreatment on Production of Levulinic Acid Through Acid Hydrolysis

Abstract

Acid hydrolysis is one of the most important processes for biomass conversion into value-added chemicals. However, hydrolysis of biomass requires an effective pretreatment to make this reaction more efficient. Ultrasonic technology, is one of the pretreatment used in biomass conversion before being subjected to hydrolysis reaction. In this study, the effect of ultrasonic on the conversion of oil palm mesocarp fibre into levulinic acid (LA) was investigated. Levulinic acid, can be used as a chemical intermediate for many applications. Two different pretreatments were explored. For acid pretreatment, samples were pretreated at different sulfuric acid concentration and temperatures (60 °C, 80 °C and 100 °C). For ultrasonic-assisted acid pretreatment, the samples were pretreated at different sonication power (40%, 60% and 80%). The highest yield of LA was obtained during hydrolysis from the sample acid pretreated at temperature at 100 ⁰C using 6 % acid solution (3.93%). While using ultrasonication, the highest yield of LA was around (3.11%) obtained at 80% power and 6% acid solution. Hydrolysis was also conducted without removing liquor (liquid solution) from the biomass after each pretreatment. The results after hydrolysis showed a remarkable improvement of LA yield at 20.54% obtained from sample pretreated with H2SO4 acid at 100 ⁰C and 6% (v/v). These results suggest that acid pretreatment at high temperature is effective in improving the yield of LA from the biomass. The use of ultrasonication did not improve the hydrolysis as expected.