Doctor of Philosophy
Chemical and Biochemical Engineering
Due to the depletion of fossil fuel reserves, renewable resources are required to produce tomorrow’s fuel range hydrocarbons. This thesis focuses on the hydrothermal decarboxylation of fatty acids and their derivatives derived from renewable sources. These are required for liquid transportation fuels which have similar properties to conventional fuels. Detailed catalytic studies were performed for the decarboxylation of oleic acid as a model compound and corn distiller’s oil (CDO) as a real feedstock. Commercial activated carbon and laboratory prepared Ni-Al2O3, MgO-Al2O3, Mo-Al2O3 catalysts were also examined as catalysts. Fatty acid derivatives such as castor oil, waste cooking oil, and palm oil were explored as potential feedstocks.
Activated carbon was found to be an efficient catalyst for oleic acid decarboxylation in both batch and continuous reactor systems. The results showed that up to 97% degree of decarboxylation was achieved using a batch reactor system under optimized experimental conditions, while up to 91% was obtained in a continuous fixed bed reactor system at comparatively low pressure. Liquid yields in both cases were ~ 62 and 63.5 wt% whereas the selectivity of heptadecane was found to be 81 and 89.3%, respectively. This result is attributed to the difference in the process and reaction dynamics of this experimental system. Although the Mo-Al2O3 catalyst exhibited 91% decarboxylation and 71wt% liquid yield using the continuous reactor system, the selectivity of heptadecane was comparatively lower compared to that of activated carbon. This indicates that the Mo-Al2O3 catalyst led to some cracking of the oleic acid feed into lower hydrocarbons instead of heptadecane. On the other hand, decarboxylation of CDO in the batch reactor system provided almost 100% degree of decarboxylation with 65% liquid yield using activated carbon as catalyst under the optimized reaction conditions. It was also found that the fuel properties of the decarboxylated liquid products using activated carbon and Mo-Al2O3 catalyst had a similar density and high heating value (HHV) compared to commercial fuels such as kerosene, jet fuel and diesel.
Decarboxylation of Castor oil, palm oil and waste cooking oil were examined using the Mo-Al2O3 catalyst in the continuous reactor system. The results showed that the decarboxylation activities of this feedstocks followed the trend of oleic acid and CDO, indicating high potential for these feedstocks. This thesis shows that hydrothermal decarboxylation of fatty acids or their derivatives provides an excellent opportunity to produce renewable hydrocarbons which can potentially significantly reduce our dependency on fossil fuels.
Hossain, Md Zakir, "Hydrothermal decarboxylation of fatty acids and their derivatives for liquid transportation fuels" (2017). Electronic Thesis and Dissertation Repository. 5021.