Catalytic Upgrading of Hemp (Cannabis Sativa) Pyrolysis Oil Over CoMo/Zeolite and In-Silico Toxicity Assessment

Abstract

In this study, hemp pulp, a by-product of cold press oil extraction, was selected as a pyrolysis feedstock owing to its high volatile matter (75.23%) and elevated calorific value (17.18 MJ kg-1). Pyrolysis of the pulp yielded a crude bio-oil with a higher heating value (HHV) of 32.4 MJ kg-1 and 19.63 wt% oxygen content. To upgrade the oil, a CoMo/zeolite catalyst was synthesized via wet impregnation and characterized (Brunauer-Emmet-Teller surface area, 92.8 m2 g-1; pore diameter, 8.8 nm). Catalytic treatment at 250 degrees C for 2 h led to significant deoxygenation, reducing the oxygen content to 11.27 wt% and increasing the HHV to 37.7 MJ kg-1. Fourier transform infrared and gas chromatography-mass spectrometry analysis confirmed structural changes and formation of valuable chemicals such as toluene and bis(2-ethylhexyl) phthalate. The toxicity results revealed that bis(2-ethylhexyl) phthalate exhibits the highest toxicity and bioaccumulation potential among various aquatic organisms, especially crustaceans, Daphnia magna, and fish species. Toluene showed moderate toxicity and biodegradability, whereas phenol, 3-ethyl- demonstrated lower toxicity and was not biodegradable. These findings highlight the environmental risks of pyrolysis liquids derived from hemp in aquatic ecosystems and emphasize the necessity for environmental monitoring and risk management when using such products. These results support the viability of hemp pulp as a renewable bio-oil source, although scale-up is required for fuel-grade application.