International Journal of Advanced Research in Chemical Science (IJARCS) Volume 2, Issue 6, June 2015, PP 34-39 ISSN 2349-039X (Print) & ISSN 2349-0403 (Online) www.arcjournals.org ©ARC Page | 34 The Evaluation of Microwave-Assisted and Conventional Heating in the Acid-Catalyzed Synthesis of Biodiesel from Vegetable Oil Lukasz Gauza, Sasha Blair, Kyle McElhoney, Kevin W. Kittredge* Department of Chemistry, Virginia Wesleyan College, 1584 Wesleyan Dr, Norfolk, VA, USA *kkittredge@vwc.edu Abstract: Microwave-assisted and conventional heating methods were evaluated in the transesterification acid-catalyzed reaction of vegetable oil with methanol into the methyl ester using a variety of solid acid catalysts, p-toluenesulfonic acid and Nafion NR 50 and the liquid catalyst sulfuric acid. Both heating methods gave excellent yields of product (<85%); however the microwave-assisted synthesis was completed in shorter reaction times, 1 h compared to more than 24 h. The heats of combustion for the biodiesel product were found to be between 38.75 and 42.05kJ/g, similar to literature values; however they are lower than the heat of combustion value for commercial petroleum diesel of 45.52kJ/g. Keywords: Biodiesel, microwave-assisted, solid catalysis 1. INTRODUCTION The rapid consumption of petroleum fuels and their increasing prices have come to worldwide attention due to their future environmental and economic.[1] This worldwide ecological and economical movement resulted in the search for alternative fuel sources.[2]Biodiesel is one of the fuels aimed at reducing the usage of petroleum fuels.[3]Unlike petroleum fuels, biodiesel fuels can be nontoxic and biodegradable.[2] Thus they offer lower potential environmental hazards in form of spills during transport compared to the petroleum fuels. Their production and consumption is a closed carbon cycle andCO 2 emissions may be reduced by as much as 78%.[4-5] Biodiesel is readily produced from waste vegetable oil and consists of fatty acids esters of various lengths (Figure 1).[6- 8] Figure1. Structure of a fatty acid methyl ester (FAME) in biodiesel where n = 13-17 and 0-3 double bonds. The esters are obtained by the transesterification of various glycerides with alcohols such as methanol or ethanol. The product esters are fatty acids methyl ester (FAME) or fatty acids ethyl esters (FAEE), depending on which alcohol was used in their synthesis.[2] Their synthesis is controlled by the acid and base catalyzed equilibrium shown in Figure 2. To increase the formation of the fatty acid ester an excess of the alcohol is used.[9] In the commercial production of biodiesel two catalytic approaches are used; acid catalysts such as sulfuric acid (H 2 SO 4 ) or p-toluenesulfonic acid (PTSA) and base catalysts such as sodium/potassium hydroxide (NaOH/KOH). One of the shortcomings from using alkali base catalysts is these tend to cause equipment deterioration and undesired side reactions whereas acidic reaction conditions do not cause similar equipment deterioration.[2] Also, by using acid catalysts oils with high free-acid and water content can be more easily processed. Waste vegetable oil tends to have higher free-acid content and more water than its virgin counterpart, and therefore acid-catalyzed transesterification is better suited for these reaction conditions.[1]There are several well-known solid-state supported acid catalysts: sulfated zirconia, sulfated Mn/Fe zirconia, Amberlsyt-15 (macroreticular resin with sulfonic acid functionality), SZ, Nafion NR 50 (perfluorinated resin) and WZ.[7,8,10]Biodiesel has also been synthesized using a non-catalytic approach from supercritical methanol.[11] These reactions were