Catalytic cracking of waste cooking oil followed with hydro-isomerization for high-quality biofuel production

Desulfurization and molecular structural modification are critical steps for producing high-quality biofuel. Here, we demonstrated an efficient and environmentally desulfurization process for converting waste cooking oil containing many impurities to low-sulfur biofuel, and this production process could be adopted on a large scale. This study found that composite catalysts (10 wt% base catalyst and 1 wt% cupric nitrate) could effectively remove the impurities (sulfur, chlorine and metal ions) in waste cooking oil during the deoxygenation process. The desulfurization rate was achieved at 94% over Cu(NO3)3 and K2CO3 (1 wt%:10 wt%). The copper nitrate catalyst converted sulfur species into water and H2S. In addition, to further obtain high-quality biofuel with low cold flow property, the above generated biofuel with low sulfur content was hydro-isomerized over the Ce–Pt/SAPO-11 catalyst. Under the action of the bimetallic catalyst, the isomerization reaction could be carried out at low reaction temperature (300 °C) due to the high olefin content (approximately 43%) in pyrolytic oils. A high-quality biofuel production with low sulfur content (lower 10 ppm) and low cold filter plugging point (−20 °C) could be obtained through the above two processes, which all met the ASTM and EN specifications. Overall, a novel method was reported to convert low-quality waste cooking oil to high valuable biofuel.