Optimization of biodiesel production process from waste cooking oil using response surface methodology

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Biodiesel as a safe alternative fuel for internal combustion engines points to the mixture of mono alkyl esters of fatty acids (average chain length: C14-C22) that derived from triglyceride sources like vegetable oils [1]. The vegetable oils are the renewable and sustainable energy sources that have calorific value close to traditional diesel [2]. Conversion of triglycerides into methyl or ethyl esters is performed by transesterification reaction. Transesterification is an equilibrium and reversible reaction that converts the oil into biodiesel and glycerol. Employing the catalyst is essential due to insolubility of two main reagents, oil and alcohol. Catalyst improves the solubility and accelerates the reaction rate [3]. Alkaline catalysts typically used are NaOH, KOH, NaOCH3, and KOCH3 [8]. For using the alkaline catalyst properly, oils must have low level of free fatty acid (FFA) (a range between 0.5-3%). Above this limit transesterification does not occur and products formed are soap and water, resulting in lower ester yield [4]. High cost of biodiesel is a major issue for its commercialization. The low-cost production can be achieved by using low cost feedstock like waste cooking oil. Waste cooking oils as biodiesel feedstocks are available around the world. Annual quantity of WCO depends on the consumption of fresh vegetable oil. EU countries are generated 0.7 to 1 million tons waste cooking oil per year [5]. UK and Canada produce 0.2 and 0.135 Mt of WCO annually, respectively. WCO generation of China and Japan is approximated about 4.5 and 0.6 Mt/year, respectively. Therefore, production of biodiesel from waste oils is not only a solution for the environmental problems of disposing it, but also improved the economics of the... ... middle of paper ... ...8 wt.%. It can be concluded that biodiesel yield strongly influences from all studied operating parameters. The predicted mathematical model was confirmed by both statistical and empirical assessments. Optimum condition for WCO transesterification was found as temperature of 65 °C, catalyst loading of 1.4 wt.% and MeOH/oil molar ratio of 7.5:1. From the ANOVA results, alkali catalyst concentration was the most important parameter that affects the biodiesel productivity. Additionally, TGA technique applied for conversion determining was compared by GC analysis in the viewpoint of transesterification monitoring. As a result, this method can be utilized instead of other characterization methods as qualitative analysis. The fuel characteristics of the biodiesel produced under optimum condition were consistent with international standards. Further work is suggested for

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