Conversion of delignified stem sorghum bicolor into levulinic acid using micro and mesoporous ZSM-5 catalysts

Abstract

Sorghum bicolor stem is one of the biomass wastes that can be used as raw material for synthesizing platform chemicals. Levulinic acid is one of the chemicals that is currently a substance often synthesized or isolated. Levulinic acid can be catalytically synthesized from sorghum stem waste which is rich in cellulose. Cellulose in the sorghum stem is still bound to lignin and hemicellulose, therefore pretreatment is needed to reduce lignin. The method consists of pretreatment of biomass by delignification, manufacturing of micro and mesoporous ZSM-5 catalysts (double template method) and the reaction of the conversion of stem sorghum to levulinic acid is carried out in a mini reactor. Catalyst characterizations were conducted using FTIR, XRD, SEM EDX and product analysis by HPLC. The result of delignification is the cellulose content increased from 45.10 % to 76.66 %. The result of as-synthesized ZSM-5 showed the diffractogram patterns similar to the standard ZSM-5. SEM image showed a hexagonal coffin-like shape which is the characteristic of ZSM-5. The levulinic acid produced using meso-porous ZSM-5 catalyst was observed at the reaction time of 2-6 h, while the yield of levulinic acid using micro-porous ZSM-5 catalyst was observed at the end of the reaction time, i.e. 6-10 h. It can be concluded that the pore size of the catalyst and the duration of the conversion time influenced the yield of levulinic acid.