Lignin isolation and characterization as co-products from pilot plants of second generations bioethanol

Abstract

Dependency on fossil fuels has provoked the decreasing air quality and rising global temperature. Bioethanol is now understudy for gasoline-blending purposes. However, because of limited resources and food competitiveness issues of the first generation, second generations ethanol (G2) that uses lignocellulosic biomass as raw material has been chosen. Lignin can be produced during the pretreatment of this material. The pretreatment process of 50 kg of oil palm empty fruit bunch (OPEB) with 250 liters NaOH 10% at 150°C and 6-8 bars for bioethanol production has been carried out in the 450-liter reactor of bioethanol pilot plant. Furthermore, the black liquor that rich in lignin was isolated by the precipitation method at pH 2 by using two different acids, HCl and CH3COOH. Both different lignins originated were then analyzed by using integrated pyrolysis and gas chromatography mass spectrometry (Py-GC MS). The HCl-lignin was rich in oxazolidine, 2,2-diethyl-3-methyl- and phenol, 2,6-dimethoxy. Meanwhile, CH3COOH-lignin rich in 2,6-dimethoxy-phenol and phenol. Furthermore, thermal gravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) have been used to analyze stability thermal properties and the functional groups of both lignin, respectively. HCl lignin was showed more thermal stability compared to CH3COOH lignin. However, phenol compounds were available abundantly in CH3COOH lignin. Lignin as a co-product of second generations of bioethanol is a very promising biomaterial. This study showed that the chemical composition and properties of lignin were dependent on their isolation method. The properties are very important to determine further utilization of the lignin.