Preparation of Supported Nanosized Sulfated Zirconia by Strontia and Assessment of Its Activities in the Esterification of Oleic Acid

In recent years, governmental health agencies are highly concerned about the toxic emissions from diesel engines. Among fuel alternatives, biodiesel has the highest potential. Biodiesel has similar properties as diesel and could be directly utilized for diesel engines. The main advantages of biodiesel are that it could be used without modification, it is renewable, non-toxic, environment-friendly, and generates less harmful emissions such as sulfur oxide, aromatics and CO.1 Biodiesel is generally produced from transesterification of fats and vegetable oils with a short-chain alcohol in the presence of a catalyst.2 Recently, non-edible oil as a feedstock (e.g., Jatropha, algae and waste cooking oil) was of prime concern for the reduction of biodiesel production costs.3 However, these feedstocks have a high percentage of free fatty acids (FFA) that could not be converted to biodiesel with homogeneous catalysts due to the production of soap as a by-product from the reaction of FFA and homogeneous catalyst. It must be noted that biodiesel purification and separation produces huge amounts of wastewater. Therefore, the heterogeneous catalysts have been utilized for the conversion of FFAs to bio diesel.4,5 Amongst different heterogeneous catalysts, sulfated zirconia exhibits a high ability of carrying out both esterification and transesterification reaction.6,7 Furthermore, sulfated zirconia has a towering catalytic activity of isomerizing alkanes at relatively low temperature.8 However, its main drawbacks are its deactivation after one reaction, and the ability to be easily regenerated by simple re-calcinations in air.9 Therefore, many researchers have attempted to improve the properties of the catalyst by supporting it with another metal oxide. In previous works conducted by the authors, it was reported that sulfated zirconia modified with strontia (SrO/S-ZrO2) and alumina by free solvent method has higher catalytic activity than pure sulfated zirconia.10,11 The authors also demonstrated that there is a good agreement between their findings and those conducted by Yee et al.12 Nonetheless, more work is needed to evaluate the properties of the catalyst, such as optimum amount of support loading and reusability of the catalyst. Therefore, the aim of this study was to optimize strontia loading percentage on sulfated zirconia and enhance its reusability. To obtain these objectives, the catalysts were characterized by XRD, BET, FT-IR and TEM. Acidity and catalytic activity were also examined by NaOH titration and esterification of oleic acid, respectively. Furthermore, the influence of different parameters for the best conversion percentage of the oleic acid as FFA to its methyl ester has also been examined. Preparation of Supported Nanosized Sulfated Zirconia by Strontia and Assessment of Its Activities in the Esterification of Oleic Acid