Improvement of waste frying oil/cottonseed oil-based biodiesel properties by adjusting unsaturation and its effect on engine emission characteristics

Waste frying oil is a highly promising feedstock for biodiesel production due to its lower cost compared to refined vegetable oils. In this study, biodiesel was prepared by transesterification of mixed waste frying oil with dimethyl carbonate, utilizing immobilized recombinant lipase in tert-butanol as the medium. The activation energy (Ea) and pre-exponential factor (k0) were determined to be 73.8kJ/mol and 1.62×106, respectively. Under optimal reaction conditions, the biodiesel yield can reach 88.5%. Subsequently, cottonseed oil was introduced into the feedstock to enhance the crystallization temperature of the product, which enables biodiesel production to meet the fuel property standards. The cold filter plugging point of biodiesel was reduced to 4.3 ℃. Ultimately, blending biodiesel with diesel significantly reduces smoke emissions from diesel engines, with the B80 blend demonstrating superior effectiveness. This study presents an efficient and cost-effective method for biodiesel production.