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Development of Homogeneous and Heterogeneous Catalysts for the Production of Biodiesel and Aviation Fuel
Chemical and Materials Engineering
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Biodiesel is a renewable fuel that consists of fatty acid esters synthesized from oils or fats and is non-toxic, biodegradable, and has lower carbon/sulfur emissions than petroleum diesel. Biodiesel can be produced from waste vegetable oil, animal fats, and oil extracted from organisms such as algae or cyanobacteria. Since waste vegetable oils and algae oils are the major source for current commercial biodiesel and bio-jet fuel, they are the major feedstocks utilized in this dissertation. The focus of this research is to study biodiesel and jet fuel production using mesoporous and zeolitic heterogeneous catalysts. Heterogeneous catalysts such as KIT-5, KIT-6 and zeolite beta were prepared and tested for their catalytic ability to esterify high free fatty acid feedstocks. KIT-5 and KIT-6 mesoporous catalyst systems were found to be more efficient and recyclable for biodiesel synthesis when compared to other established mesoporous catalyst systems. Heteropoly acids, supported on KIT-5 and KIT-6, were used in single step esterification of algae oil, used cooking oil and palmitic acid. High yields, and conversions greater than 80% were observed. Slight deactivation of the catalyst was observed upon recycling. Silicotungstic acid (26 wt%) loaded KIT-6 reacted at 70 °C with an alcohol to acid volume ratio of 2 and 1.5 wt% catalyst for 3 h to yield maximum conversion. Similarly, phosphotungstic acid (26.5 wt%) loaded KIT-5 catalyzed maximum conversion of free fatty acids under identical reaction conditions maintained for 4 h. Kinetics and reaction mechanism for heterogeneous esterification of used cooking oil was also established by using KIT-5 catalyst. A first order kinetic model was developed based on the experimental data obtained. Currently, most of the commercial biodiesel production facilities employ traditional alkali-catalyzed transesterification that involves high processing costs. So, a morpholine co-catalyst employed transesterification process was developed to replace the time-consuming traditional process. An improvement in the kinetics of the transesterification reaction was observed with three different feedstocks, namely corn, canola and coffee oils. The development and commercial production of sustainable alternative fuels to minimize effects of fossil fuel combustion also applies to jet fuels. Jet fuel is a highly specialized form of petroleum fuel comprised of primarily hydrocarbons such as paraffins, olefins, naphthenes, and aromatics. So finally, production of renewable jet fuels from algae oils by hydrodeoxygenation using transition metal loaded zeolite beta was investigated and is discussed in detail. This process adds hydrogen in order to remove the oxygen from the feedstock and then further cracks the remaining product to meet the specifications for bio-jet fuel. Algae oil was deoxygenized and hydrocracked at 400 °C and 400 psi, using 1 wt% catalyst to obtain a maximum mass conversion of 98%. Overall this dissertation presents a detailed insight into biodiesel production using KIT-5 and KIT-6 catalysts, jet fuel production using zeolite beta catalyst and improving reaction kinetics of traditional biodiesel production using morpholine co-catalyst. The outcomes of this research have been published in several scientific journals and presented at national conferences. The published articles and conference presentations are listed at the beginning of this dissertation.