Green Diesel Production from Oleic Acid Deoxygenation Using Subcritical Water under Hydrogen-Free Condition

Abstract

Green diesel or bio-hydrogenated diesel (BHD) is a second generation renewable liquid fuel that can be produced from several types of renewable sources such as triglyceride in vegetable oils or animal fats, free fatty acid in waste from refining palm oil industry, and their derivatives via a catalytic reaction involving hydrogenation and deoxygenation provided n-alkanes as a main product. In this work, the aim was to investigate the effect of reaction time and catalyst type on green diesel production in a batch mode without H2 feed. The green diesel was produced from oleic acid using activated carbon and commercial catalyst at reaction temperature of 250 °C and total pressure of 40 bars under DI water as a hydrogen source. The results showed that 100% oleic acid conversion was obtained by using both type of catalysts. Pentadecane was the main product with 96% percentage at 3 h reaction time for commercial catalyst and 100% percentage at 5 h reaction time for activated carbon. In addition, the products in gas phase were CO2 and CO for both types of catalyst and CH4 only appeared when commercial catalysts were used.