Oxidative stability of waste cooking oil and white diesel upon storage at room temperature

Renewable diesel fuels are alternative fuels produced from vegetable oils or animal fats. Catalytic hydrotreating of waste cooking oil (WCO) was carried out at pilot-plant scale and a paraffinic diesel, called “white” diesel was obtained. The white diesel and WCO samples were stored for one year at room temperature under normal atmospheric conditions, but not exposed to sunlight. Viscosity, total acid number (TAN), induction period (IP), carbonaceous deposits, density, cold flow properties, distillation and water content were monitored. TAN and density of the white diesel stored in conventional bottles changed from 0 to 0.221 mg KOH/g and from 787 to 838 kg/m3, respectively. The remaining parameters did not vary significantly. Water content of WCO increased from 482 to 2491 mg/kg, TAN from 0.744 to 0.931 mg KOH/g, whereas viscosity, IP and carbon residues fluctuated mildly. The results are indicative of the white diesel’s stability, rendering it suitable for prolonged storage.

► “White diesel” maintains high oxidation stability after extended storage time (1 year). ► Increased oxidation stability of “white diesel” can be attributed to a high paraffinic content and absence of unsaturated bonds. ► Waste Cooking Oil is susceptible to oxidative degradation after extended storage.