Microwave Energy Pre-treated Ethanolysis of Waste Cooking Oil & Parametric Optimization

Exploration for environmental friendly alternative energy is essential to complement depleting and environmentally unfriendly fossil fuels. Renewables energy such as biodiesel is gaining increased attention at global level. One other hand, edible oil as a raw material and processing costs are adversely affecting the economic viability of biodiesel technology. Currently, more than 95 % of biodiesel raw material feedstock sources are from edible oil sources which competes with food processing industries affecting both the economics of biodiesel and food industries. Transesterification reaction is a very slow reaction due to limited solubility of low molecular weight alcohol in vegetable oil. The slow reaction rate of transesterification increases the processing cost of biodiesel which ultimately increase the cost of biodiesel as a fuel. Use of non-edible oil such as used cooking oil (WCO) can reduce the high cost of edible oil sources. The slow transesterification rate can also be increased by using reaction rate increasing techniques such as microwave heat pretreatment of oil and use of rate enhancement agent such as phase transfer catalysis along with the conventional catalyst. In the present research work, the concept of microwave pre-treatment of oil for transesterification of waste cooking oil were utilized. To design appropriate transesterification reaction conditions, physical and chemical properties of WCO were investigated. The Individual and interaction effects of transesterification reaction parameters were studied using design of experiment (DOE) software’s such as central composite design (CCD) of response surface methodology (RSM). After Investigation of the parametric effect, optimum reaction condition for maximum yield was established experimentally using CCD of RSM. At optimal conditions of 7.5 ethanol: oil molar ratio, 1.5 wt% NaOH concentration, 3 minutes pre-treatment of oil with microwave energy, 45℃ reaction temperature & 22.5 minutes of reaction time, it was determined that about 98.72 wt% FAEE yield was obtained as compared to 86.24wt% FAEE yield obtained with oil untreated with microwave energy at optimal concentration of 7.5 ethanol: oil molar ratio, 1.5 wt% catalyst concentration, 45℃ and 60 minutes of reaction time. This resulted in about 12.48 wt% gain in FAEE yield while reducing the reaction time.