Comprehensive investigation of co-pyrolysis of rubber seed oil and industrial hemp stems: thermogravimetric analysis based on artificial neural networks; synergistic effect and pyrolysis product

The effects of different mass ratios and pyrolysis temperatures on pyrolysis oils during the RSO and IHS co-pyrolysis process are investigated. The addition of IHS leads to favorable changes in thermogravimetric parameters (Ti, Tmax, Tf, DTGmax). An artificial neural network based on BP algorithm can accurately predict the thermogravimetric data of RSO and IHS co-pyrolysis under unknown conditions. Pyrolysis oil from 10 %IHS +90 %RSO have the best quality with the highest content (52.02 %) of monocyclic aromatic hydrocarbons (MAHs) when the temperature is 600 °C. Compared to the IHS and RSO pyrolysis oil at the same temperature, the content of oxygenated substance in the pyrolysis oil under the optimal co-pyrolysis conditions decrease by 29.09 % and 13.65 %, respectively. Chemical structure of biochar under optimal conditions for the preparation of pyrolysis oil is analyzed. According to XPS and Raman of biochar, the structure of the biochar becomes more compact due to complex condensation reactions when the temperature is 800 °C. Stabilized oxygen-containing functional groups are the key factors leading to the formation of biochar. The content of C-C groups on biochar surface decrease from 89.95 % at 400 °C to 70.60 % at 800 °C. The C-O (aliphatic) groups content decreases from 62.86 % at 400 °C to 33.61 % at 800 °C and the C-O (aromatic) groups content increases from 23.63 % at 400 °C to 52.37 % at 800 °C. This study provides new insights into the potential application of co-pyrolysis in the efficient utilization of RSO and IHS.