Optimization of oil palm fronds pretreatment using ionic liquid for levulinic acid production

Abstract

The pretreatment of oil palm frond (OPF) has been carried out using 1-butyl-3-methylimidazolium bromide ([BMIM]Br) in the presence of aqueous sulphuric acid (H2SO4). The effects of reaction temperature, reaction time and [BMIM]Br loading on lignin degradation were investigated by applying Box Behnken Design of Response Surface Methodology (RSM). The optimized process condition for OPF pretreatment were 123°C, 175 min and 9.9 g of [BMIM]Br loading with an optimum lignin degradation of 88.2%. The experimental results fitted-well with the predicted value with less than 5% error. It was also demonstrated that lignin degradation using recycled [BMIM]Br gave sufficient performance for five successive runs. It was revealed from SEM and XRD analyses, that the pretreated OPF was porous and less crystalline after pretreatment. Consequently, the pretreated OPF renders 25.3% levulinic acid yield in acid hydrolysis compared to 18.2% yield for untreated OPF.