Energy Fuels 2010, 24, 3214–3222 Published on Web 04/01/2010
: DOI:10.1021/ef901428k
Investigation of Lipase-Catalyzed Biodiesel Production Using Ionic Liquid [BMIM][PF6] as a Co-solvent in 500 mL Jacketed Conical and Shake Flask Reactors Using Triolein or Waste Canola Oil as Substrates Nicholas Ivan Ruzich* and Amarjeet S. Bassi Department of Chemical and Biochemical Engineering, Faculty of Engineering, University of Western Ontario, London, Ontario N6A 5B9, Canada Received November 23, 2009. Revised Manuscript Received February 7, 2010
The production of biodiesel was investigated using a lipase-catalyzed (Novozym 435) reaction involving methyl acetate and ionic liquid [BMIM][PF6] as a co-solvent. The use of a lipase catalyst removed the need for alkali wastewater removal and treatment, and the methyl acetate and ionic liquid helped prevent deactivation and improve activity and stability of the lipase, respectively. Experiments were carried out in shake flask and jacketed conical reactors. Runs performed in shake flask reactor produced similar fatty acid methyl ester (FAME) yields to previous work using a small-scale reactor (83%), indicating that the reaction can achieve high yields provided that sufficient mixing between the oil and ionic liquid phases occur. The highest yield achieved in the conical reactor was 54% because of the relatively poor mixing in the reactor as a result of two phases present in the mixture. An additional benefit of using ionic liquid as a co-solvent in the process was for its ease of separation of products. Two distinct phases were present at the end of the reaction, with the ionic liquid phase containing the triacetylglycerol byproduct and any unreacted methyl acetate. The byproduct was then separated by washing with water, and the ionic liquid was removed by decantation and reused. FAMEs were also successfully produced from waste canola oil, with a 72% yield achieved in a small-scale reactor and a 30% yield in a 500 mL jacketed conical reactor.
of water would lead to a saponification side reaction, which results in the formation of soap.1 The oil or fat also requires a low free fatty acid content, and the alkali wastewater in the product has to be removed in an additional separation stage because of potential environmental concerns.1,5 Lipase catalysts have become a more viable alternative as a catalyst in the esterification reaction. Lipases can be either immobilized on a support or in free form. There are several commercially available immobilized lipases, including lipases from Candida antarctica and Rhizomucor miehei. As mentioned, when using an alkali catalyst, the separation from the product and treatment of the alkaline wastewater are additional steps in the process. The overall process is also energy-intensive because of high stirring speeds and temperatures required for high conversions.6 These additional steps would be eliminated with the use of a lipase catalyst. While alkali catalysts require the oil or fat and alcohol to have a low free fatty acid content, waste oils or fats with high free fatty acid contents can be converted to fatty acid methyl esters (FAMEs) using lipase as a catalyst without any unwanted side reactions.7 Lipase-based biodiesel production has not achieved commercial potential because of the expense and instability of the lipase. There is therefore a need for the lipase to be recyclable for the reaction to be cost-effective. Two other potential problems arise for the use of lipases. If alcohol is used as the acyl acceptor, it can strongly inhibit or denature the lipase and
Introduction Large amounts of vegetable oil and animal fats are produced worldwide, with a certain amount used as starting materials for potentially valuable products. One of these valuable products is biodiesel, an alternative fuel to regular petroleum-based diesel. Biodiesel is produced from an esterification reaction involving the oil or fat with an acyl acceptor, either an alcohol or an ester. There are many environmental advantages to using biodiesel versus petroleum diesel. It is biodegradable and nontoxic and has low-emission profiles.1 Biodiesel degrades up to 4 times faster than petroleum diesel. The exhaust has decreased smoke and particulate levels when compared to diesel, as well as having a less offensive odor. The use of biodiesel will also contribute to decreases in greenhouse gases and global warming.2,3 The esterification reaction is a three-step process that begins with the presence of a catalyst. Alkali catalysts have been the most commonly used catalyst in practice. Typical examples are hydroxides, carbonates, methoxides, and amides. Reactions can be run at temperatures as low as room temperature, and the reaction rates for alkali catalysts are much higher when compared to acid catalysts. One disadvantage to using an alkali catalyst is that the oils or fats and alcohol used have to be anhydrous (
