Microwave pretreatment of Leucaena leucocephala using dilute sulphuric acid / Felicia Unda Anggat

Globally, the production of bioethanol from lignocellulosic biomass is in demand due to fossil fuels depletion and the effects of fossil fuels consumptions such as greenhouse gas emissions and climate change. As biomass sourced from natural forests is not favourable to avoid risks of deforestation, it is desirable to study the use of Leucaena Leucocephala, a fast-growing tropical tree and non-crop species to be a fuel supply for bioethanol production. However, it is necessary for lignocellulosic material, due to its recalcitrant structure to undergo pretreatment in order to increase the efficiency of its enzymatic hydrolysis of cellulose into simple sugars, before fermentation process to produce bioethanol. Therefore, the purpose of this study is to determine the effect of dilute sulphuric acid concentration and microwave pretreatment time on the functional groups, thermal degradation profiles and proximate analysis of Leucaena Leucocephala. The concentrations of dilute sulphuric acid used were 0.2M and 0.4M with microwave pretreatment time of 5 minutes and 10 minutes. Four types of pretreated samples (0.2M-5min, 0.2M-10min, 0.4M-5min, 0.4M-10min) were prepared with respective dilute sulphuric acid concentration and microwave pretreatment time. An untreated sample, which was not pretreated with dilute H2SO4 and microwave heating, was used as a basis of the pretreatment. FTIR results showed that O-H absorption peak for each sample increased after respective pretreatment conditions. Increasing microwave pretreatment time did not necessarily remove C-H functional group of lignin. The disappearance of peak for C-O stretching in hemicellulose and lignin showed removal of major hemicellulose. No significant differences were observed for C-O-C, C-O, C-OH functional groups after pretreatment though small increased in band assignment in the region might indicate cellulose enhancement. Thermogravimetric analysis (TGA) results showed that during pyrolysis, the maximum degradation temperature and maximum mass rate loss obtained were 363.69°C and 2.76 mg min-1, respectively. Increasing severity of microwave pretreatment time from 5 minutes to 10 minutes and dilute sulphuric acid concentration from 0.2M to 0.4M increased the biofuel properties of the sample as higher volatile matter were released with lower moisture and ash content were obtained.