Production of rice husk bio-oil and comprehensive characterization (qualitative and quantitative) by HPLC/PDA and GC GC/qMS
Pyrolysis of rice husk (RH) is an efficient process for the transformation of biomass to bio-oil (high-added value product). Bio-oil consists of two immiscible phases (organic and aqueous) both with potential for the generation of important chemicals for the industry. The aim of this study was to produce bio-oil by pyrolysis of RH and elucidate its chemical composition. Response surface methodology (RSM) was successfully used to determine the optimal pyrolysis conditions for the RH dry bio-oil production using central composite design (CCD). Temperature and flow rate significantly affected the bio-oil production and higher dry bio-oil yield was achieved at 650 °C and N2 flow rate of 100 mL min−1 (predicted values of 16.9%). High performance liquid chromatography with photodiode array detection (HPLC/PDA) and comprehensive two-dimensional gas chromatography with quadrupole mass spectrometry detection (GC × GC/qMS) were used to provide a comprehensive characterization (qualitative and quantitative) of both phases from RH bio-oil. Through GC × GC/qMS analysis a total number of 98 compounds were found in organic phase; from these, 62 were quantified using a developed quantitative method by relative response factors (RRFs). Phenols and ketones (cyclic ketones) were majority in the organic phase, 8.21 and 5.90 wt%, respectively, and the benzofuran (1.37 wt%) corresponds to the major identified compound. HPLC/PDA analysis evidenced a high concentration of benzenediols and furfurals in the aqueous phase. Catechol was the major compound (2063 mg L−1) followed by furfural (997 mg L−1) and hydroquinone (899 mg L−1). This is the first time that GC × GC/qMS and HPLC/PDA has been used to characterize (qualitatively and quantitatively) both phases from RH bio-oil which showed potential use as a source of high-added value chemicals.