Catalytic hydrocracking of waste vegetable oil using high pressure flow apparatus to obtain jet fuel range alkanes

Abstract

The hydrocracking of waste vegetable (cooking) oil was studied over two different catalysts as an alternative way to produce jet fuel range alkanes (C9 – C15). Experiments were carried out in a packed bed reactor at temperatures of 400, 425 and 450°C and with a hydrogen pressure of 120 bar. Two types of fresh and regenerated catalyst were used: ruthenium/alumina (Ru-γ- Al2O3) and nickel oxide/alumina (NiO-γ- Al2O3), both subject to a sulphidation pre-treatment prior to the experimental run. At the conditions studied, the hydrocracking on fresh NiO-γ- Al2O3 catalyst at the highest temperature gave the highest concentration on a mass basis (7.14 wt. %) of C9-C15 hydrocarbons in the liquid product. The liquid product yield ranged from 29.83 to 92.06 wt. %. The higher yields were obtained at the higher reaction temperatures using fresh catalyst. Within the liquid product, the higher percentages of C9 – C15 alkanes were achieved at the higher temperatures using fresh catalyst, indicating that an increase in reaction temperature favours hydrocracking. Furthermore, fresh catalyst proved to have a greater effect on the degree of hydrocracking when compared to its regenerated counterpart. Fresh untreated catalyst proved less effective than regenerated treated catalyst indicating the importance of the pre-treating stage in order to activate the catalyst for hydrocracking of triglycerides. The balance of the product was made up of gas and a waxy residue. This waxy residue was found to contain a small portion of similar alkanes to those in the liquid product but would require further processing to separate out the target compounds from the high molecular weight hydrocarbons.