| The production of biodiesel was investigated using a lipase-catalyzed (Novozym 435) reaction involving methyl acetate and ionic liquid [BMIN4][PF 6] as a co-solvent to produce an environmentally-friendly, "green" process. 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 first conducted in a small-scale reactor to optimize various reaction parameters, including the use of ionic liquid. The results showed that biodiesel was successfully produced, with an 80% overall biodiesel yield achieved in the small-scale reactor. The yield occurred with ionic liquid added to the system, at a 1:1 ratio (v/v) to the amount of oil. This verified that the presence of an ionic liquid, at a specified amount, improved the activity of the lipase and the overall biodiesel yield. The reaction was then carried out in a jacketed conical reactor. The highest yield achieved was 54%, due to relatively poor mixing in the reactor due to two phases present in the mixture. Runs performed in shake flasks produced similar yields to the small-scale (83%), indicating that the reaction can achieve high yields provided sufficient mixing between the oil and ionic liquid phases occur. An additional benefit of using ionic liquids 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 by-product and any unreacted methyl acetate. The by-product was then separated by washing with water and the ionic liquid removed by decantation and reused. Biodiesel was also successfully produced from waste canola oil, with a 72% yield achieved in small-scale and 30% in the jacketed 500 mL conical reactor. The reaction mechanism was also examined through use of kinetic modelling and the effect of ionic liquid was studied for the first time. Studies indicated that the reaction followed a Ping-Pong Bi-Bi mechanism, and the overall reaction mechanism took into account mass transfer limitations due to the presence of the ionic liquid.;KEYWORDS: Biodiesel, lipase, enzyme, esterification, interesterification, kinetics, ionic liquids, methyl acetate, [BMIM][PF6], Novozym 435. |
