Thermo-catalytic Decarboxylation of Fatty Acids and Real-World Derivatives Towards Liquid Fuels
Abstract
The production of green diesel through waste fats and oils is a promising route to producing renewable transportation fuels that are energy dense, have low oxygen content, low nitrogen content, and possess excellent cold flow properties. However, producing green diesel can be expensive, as most methods use expensive noble metals catalysts such as platinum or palladium, use expensive hydrogen gas, and/or use pyrolysis and thermal cracking to reduce hydrocarbon chain length and lose energetic carbon-hydrogen bonds. This thesis studies the continuous thermo-catalytic decarboxylation of fatty acids and their derivatives to create liquid transportation fuels using an inexpensive MoOx/Al2O3 catalyst with no addition of hydrogen gas to produce hydrocarbons with minimal cracking. MoOx/Al2O3 catalyst was found to decarboxylate oleic acid up to 99% at 375 ºC and decarboxylate stearic acid up to 99% at 390 ºC. A feedstock of 50:50 oleic:stearic acid processed at 375ºC and 3.5 h residence time had a minimum decarboxylation of 90 %, heptadecane selectivity of 55 %, and a liquid yield of 86 %. The addition of glycerol and ethanol to the reaction, which is thought to undergo reforming, lowered the necessary reaction temperature for stearic acid from 375 ºC to 390 ºC. Changing the reaction solvent from steam to toluene, without added glycerol/ethanol, lowered the necessary reaction temperature for stearic acid from 390 ºC to 375 ºC. A third-party fuel analysis confirmed that product from the process was suitable as a commercial diesel fuel, which makes this a possible route for green diesel production.