Transesterification of Waste Cooking Oil

The depletion of fossil fuel forces the world to look for alternative ways for energy production. The most common way is the production of biodiesel from waste cooking oil. This paper presents a detailed cost analysis for a biodiesel plant with capacity 100,000 ton/year. The cost analysis basis depends on the optimum conditions obtained from the experimental work that achieves biodiesel conversion of ≈ 99%. The study concludes that the project will achieve a good income that around four million US $ every year and the total net income during the life cycle of project is 72.5 million US $. The production cost of one liter biodiesel from used cooking oil is 0.515 $ while the global price of petro-diesel is 0.678 $/ liter and global biodiesel current price is 1 $/liter.

Abstract: Rotatable central composite design of experiments was employed to investigate the
significance and interactive effects of methanol:oil molar ratio, catalyst concentration,
operating temperature, reaction time and mixing rate ona base catalyzed transesterification
reaction of waste cooking oil to maximize the biodiesel yield. Based on a multiple regression
analysis, a second order polynomial equation for biodiesel yield was obtained and its validity
wasconfirmed.The optimum conditions for maximum biodiesel conversion of ≈ 99% was
depicted to be 7.54:1 M:O, 0.875 KOH wt%, 52.7oC, 1.17 h and 266 rpm.The overall
physico-chemical properties of the produced biodieselwere acceptable.

Biodiesel can easily be used as an alternative fuel in diesel engines. It is environmentally friendly and can be produced from low-cost feedstocks such as waste cooking oil (WCO). WCO contains a significant amount of free fatty acid, which is extracted by a two-step process of converting the free fatty acid by acid catalysis (H2S04) and converting the triglycerides using an NaOH catalyst. Currently, the major challenge for the industrial production of biodiesel is optimizing the yield while meeting American Society for Testing and Materials (ASTM) standards. In this study, experiments were performed to optimize the reaction conditions. The studied experimental parameters were the alcohol types (methanol, ethanol), the alcohol-to-oil molar ratio (AOMR; 3:1, 6:1, 9:1), the amount of catalyst (0.5, 1.0, 1.5 wt% of the oil), the temperature of the reaction (50, 60, 70, 80°C), the mixing intensity (300, 600, 900 rpm), and the reaction time (30, 60, 90 min). The biodiesel production yield (BPY) was optimized based on the experimental data. The optimum value of the BPY based on methanol is 95.92%, which is obtained at 73.80°C, with a reaction time of 74.02 min, an AOMR of 6.58:1, a catalyst concentration of 1.13 and a mixing intensity of 824.45 rpm. In the case of ethanol, the optimum BPY is 95.53%. which is obtained at 64.96°C, with a reaction time of 88.02 min, an AOMR of 7.005:1, a catalyst concentration of 1.25 and a mixing intensity of 592.18 rpm. These results of biodiesel production were confirmed by the experimental data.

Catalytic transesterification of triglycerides and esterification of free fatty acids underpins sustainable biodiesel production, wherein efficient heterogeneous catalysts are sought to replace mineral acids. A robust, magnetic core-shell SO 4 /Mg-Al-Fe 3 O 4 catalyst was synthesised by stepwise co-precipitation, encapsulation, and surface functionalisation. The resulting magnetically-separable catalyst has a surface area of 123 m 2 g −1 , uniform 6.5 nm mesopores, and a high total acid site loading of 2.35 mmol g-1. Optimum conditions for the (trans) esterification of waste cooking oil (WCO) over the sulfated solid acid catalyst were 95 °C, a methanol:WCO molar ratio of 9:1, and 300 min reaction to achieve 98.5% FAME yield. Esterification of oleic acid to methyl oleate resulted in an 88% yield after 150 min under the same reaction conditions. The magnetic solid acid catalyst exhibited good thermal and chemical stability and enabled facile catalyst separation post-reaction and the production of high quality biodiesel.