Hydrothermal liquefaction of rice straw with NiO nanocatalyst for bio-oil production

In this study, rice straw as an abundant agricultural waste was subjected to hydrothermal liquefaction for production of bio oil . The series of batch experiments were conducted at different temperatures (200 °C, 230 °C, 260 °C, 280 °C and 300 °C) for reaction time of 120 min with and without NiO nanocatalyst. The resulting bio-oil was categorized into light and heavy oils (LO and HO). In presence of nanocatalyst, the yields of LO and HO were maximized up to 13.2% and 17.2% at 300 °C, respectively. The carbon recovery of bio oil was significantly improved to 52.8% with 46.6% energy recovery in catalyzed reaction. Typical H/C and O/C atomic ratio of catalyzed HO are 1.2 and 0.3 respectively. The highest calorific values of LO and HO are 24.9 MJkg −1 and 31.9 MJkg −1 respectively. The tested nanocatalyst increased the yield of bio oil, but could not incite the elemental compositions and heating values of bio oil. The valuable chemical compounds in bio-oil had been analyzed by GC-MS. The LO samples mainly contained phenols, alcohols and ketones while HO consisted alkanes and organic acids. Additionally, aldehydes and other organic compounds were also found in products.