Hydrothermal liquefaction of cypress: Effects of reaction conditions on 5-lump distribution and composition

Effects of reaction temperature, reaction time and water amount on the hydrothermal liquefaction of cypress, were studied in this paper. The reaction system was divided into gas lump, water-soluble oil lump, heavy oil lump, volatile organic compounds lump, and solid residue lump. Results showed that temperature was the critical parameter for 5-lump distribution in the cypress hydrothermal conversion process. The higher temperature and longer reaction time were not usually suitable for the production of bio-oil (water-soluble oil and heavy oil). The increase in the yields of gas and volatile organic compounds was also observed as temperature was increased. However, the yield of the volatile organic compounds increased first, and then decreased with the reaction time and the water amount. High amount of water led to high conversion and bio-oil yield. The FT-IR analysis of the solid residues showed that the major peaks of cypress diminished after 280 °C. The GC–MS analysis showed that the volatile organic compounds, water-soluble oil and heavy oil comprised a mixture of organic compounds of 5–7, 5–10 and 7–26 carbons, respectively, which mainly included furfural, phenol, acids, furans and their derivatives. The WSO had similar elemental compositions but the HO had a higher content of carbon and a lower concentration of oxygen as compared to cypress.

► The reaction system was divided into gas lump, water-soluble oil lump, heavy oil lump, volatile organic compounds lump, and solid residue lump. ► The volatile organic compounds product was identified to be mainly composed of a mixture of furfural, 2-methoxy-phenol, 5-methyl-2-furancarboxaldehyde, and 2-methyl-2-cyclopenten-1-one. ► The yield of the volatile organic compounds increased fist, and then decreased with the resistance time and water amount.