Development of catalytic process for producing diesel and jet fuel from triglyceride

Abstract

Catalytic processes to produce transportation fuels (e.g., diesel, and jet fuel) from biomass have beenextensively investigated by the requirement to replace petroleum-based fuels with sustainable carbon source and thus to decrease $CO_2$ emission. Especially, vegetable oils and microalgal oils were regarded as a promising feedstock for producing fuels because they consist of triglycerides containing fatty acid units (generally $C_{12}-C_{22}$) which can be converted to transportation fuels. Most representative commercialized conversion technology is the transesterification of triglycerides with alcohols to produce alkyl esters. Ester-types biodiesel, however, still has a relatively high oxygen content, poor cold flow property, and low thermal stability, limiting its direct application as fuels. With this regard, extensive scientific efforts have recently been paid for the hydroconversion of triglycerides into oxygen-free hydrocarbons. The reaction involves (i) hydrogenation of unsaturated bond in triglycerides, (ii) hydrogenolysis of triglycerides into fatty acids, and (iii) decarboxylation, decarbonylation andhydrodeoxygenation of fatty acids to hydrocarbon. From above reaction pathway, normal paraffins can beobtained, and these products are further converted into paraffinic diesel or jet fuel by hydroisomerization or hydrocracking reaction. In the present work, we investigated hydroconverison of triglyceride (palm oil and Aurantiochytrium microalgae species) into high quality paraffinic diesel and jet fuel. The results showed that hydroconversion of triglyceride using Pt supported $\gamma-Al_2O_3$ catalyst selectively produce the $C_{n-1}$ n-paraffins by decarbonylation/decarboxylation routes and almost theoretical yield can be obtained. These n-paraffins have poor flow properties, hence, hydroisomerization reaction was carried out to obtain high quality paraffinic diesel fuels, and adequate reaction condition is important to meet the international standard specification such as cetane number and flow properties. Also, n-paraffins are converted into jet fuel by hydrocracking reaction. In the hydrocracking reaction, chain length of fatty acids, reaction gas atmosphere, type of zeolite and mesoporosity have a huge effect to produce high quality jet fuel with high yield.