Optimization and Residence Time Distribution Study of Waste Cooking Oil Transesterification in a Continuous Stirred Tank Reactor

Abstract

Waste cooking oil (WCO) transesterification using a catalyst of Dodecylbenzenesulfonic acid was investigated using a continuous stirred tank reactor. A techniques of surface response plus the design of centered composite were used for the optimizing the factors effecting on the process. The optimum conditions in this research were concluded as (catalyst amount: 1 wt. %; reaction time: 20 min; methanol/oil flow ratio: 4; reactor temperature: 60°C). The biodiesel obtained at the optimum conditions in the process was obtained at yield of 98.5%. The distribution of residence time was found experimentally and a dead zone of (110 cm3) was estimated in the CSTR using the compartment model. The physic-chemical properties for the biodiesel were found in agreement with the ASTM standard (D-6751-2) and the conventional diesel properties. The specific gravity value of biodiesel (0.87) was greater than that one of the diesel fuel (0.834). The calorific value was slightly lower than that one prescribed in the ASTM D-6751 specifications. The kinematic viscosity proved to be within the accepted limits of the. The flash point was found greater than the value specified in the ASTM and that for mineral diesel, which means safer. Acid value of 0.4 mg KOH/g was found accepted according to the biodiesel standard ASTM D-6751-2. Cetane value was found greater than that for mineral diesel.