Evaluation of cottonseed oil as co-feedstock for the hydroprocessing of petroleum middle distillates for diesel fuel production

Mandatory blending of biodiesel into petroleum diesel came to effect in 2015 in South Africa. The availability of biodiesel to implement this mandate however poses a challenge for local biodiesel producers and petroleum refineries. One alternative that could contribute to the solution of this problem is upstream blending of triglyceride oil into the hydrotreater feed of existing refining facilities. Cottonseed oil, a by-product from the cotton wool industry could be considered a co-feed candidate for diesel fuel production. In this study, the effect of catalysts and reaction conditions on the composition and yield of renewable bio-hydrocarbon fuels from cottonseed oil and hybrid diesel fuel from atmospheric gas oil/ cottonseed oil blends were evaluated .Experiments were conducted using a cylindrical bench-scale batch reactor with a volume of 350 cm3 and a maximum pressure rating of 20 MPa. For cottonseed oil the conversion performance order was found to be NiMo-Al2O3 (99.86%)> sulphided CoMo-Al2O3 (98.9%)> reduced Ni/SiO2-Al2O3 (96.8%). The highest diesel yield obtained at 390°C reaction temperature and initial hydrogen pressure of 9 MPa were 493g.kg-1 for the CoMo-Al2O3 catalyst, 492g.kg-1 for the NiMo-Al2O3 catalyst and 444g.kg-1for the NiSiO2-Al2O3 catalyst. For cottonseed oil/gas oil blends up to 20% cottonseed oil, no negative effect was observed on the hydrodesulphurisation of gas oil. Simulated distillation data showed that cracking is promoted with the addition of cottonseed oil and the diesel yield increases with an increase in cottonseed oil concentratio