Liquid fuel production via catalytic hydropyrolysis and cohydropyrolysis of agricultural residues and used engine oil

Abstract

Catalytic hydropyrolysis (HP) of crop straw and used engine oil (UEO) alone and co-HP of crop straw and UEO were conducted. Crop straws with higher cellulose contents and cellulose-to-hemicellulose mass ratios produced higher oil yield in the HP process. Positive synergistic effect between crop straw and UEO was observed for improving the pyrolysis oil yield and reducing coke formation and N and S content during their co-HP process. Compared with the oils produced from the HP of crop straw alone, the oils obtained from the co-HP of crop straw and UEO possessed higher H content, HHVs, and effective hydrogen (H/Ceff) value, and significantly lower N and S contents (12−887 mg L−1 and 16−112 mg L−1, respectively). Strong synergistic effect between crop straw and UEO for the removal of S rather than N was observed during co-HP. Co-HP was found to slightly increase the abundances of lighter compounds in the oils compared with that of HP of crop straw alone. Co-HP of crop straw and UEO also resulted in a clearly higher energy recovery (73.26–83.45 %) than the HP of crop straw alone (30.95–67.95 %). The pyrolysis oil produced from the co-HP process was divided into centrifugal oil (C-oil) and extraction oil (E-oil), and the C-oils had much lower N and S contents (12−57 mg L−1 and 16−24 mg L−1, respectively) than the E-oils (445−887 mg L−1 and 71−112 mg L−1, respectively). Moreover, the C-oils also exhibited slightly higher saturated hydrocarbons content and lower aromatic compounds content than the E-oils.