This study compares the hydrotreating of the mixture of petroleum middle distillates and the same mixture containing 20 wt % of rapeseed oil. We also study the effect of the temperature and the weight hourly space velocity (WHSV) on the co-hydrotreating of gas oil and rapeseed oil mixture. The hydrotreating is performed over a commercial hydrotreating Ni-Mo/Al2O3 catalyst at temperatures of ca. 320, 330, 340, and 350 °C with a WHSV of 0.5, 1.0, 1.5, and 2.0 h−1 under a pressure of 4 MPa and at a constant hydrogen flow of 28 dm3·h−1. The total conversion of the rapeseed oil is achieved under all the tested reaction conditions. The content of the aromatic hydrocarbons in the products reached a minimum at the lowest reaction temperature and WHSV. The content of sulphur in the products did not exceed 10 mg∙kg−1 at the reaction temperature of 350 °C and a WHSV of 1.0 h−1 and WHSV of 0.5 h−1 regardless of the reaction temperature. Our results show that in the hydrotreating of the feedstock containing rapeseed oil, a large amount of hydrogen is consumed for the dearomatisation of the fossil part and the saturation of the double bonds in the rapeseed oil and its hydrodeoxygenation.

Currently, there is an effort to achieve a more widespread use of biofuels, which are an alternative to conventional, petroleum-based fuels in mobile and stationary applications. The conversion of vegetable oils via catalytic hydrotreating to hydrotreated vegetable oil (HVO) is one of the most promising alternatives to produce high-quality biofuels. In this work, the composition and properties of rapeseed oil hydrotreating products gained over sulfided CoMo/γ-Al2O3 and NiMo/γ-Al2O3 catalysts were studied. The experiments were carried out in a laboratory trickle bed reactor in a temperature range of 320–380 °C and pressures of 4 and 8 MPa. The mixture of a rapeseed oil and isooctane was hydrotreated to simulate the coprocessing of rapeseed oil and petroleum fractions. Small amounts of aromatic hydrocarbons and, at higher reaction temperatures, considerably high contents of cycloalkanes and isoalkanes were found in the obtained liquid products. These were specifically alkylated cyclopentanes, cyclohexanes, decalines, benzenes, indanes, tetralines, and naphthalenes. The content of isoalkanes and aromatics in the liquid hydrotreating products gained over both catalysts increased with an increasing reaction temperature. A higher total amount of aromatics was found in the products of the NiMo catalyst because of its higher dehydrogenation activity compared with the CoMo catalyst. The liquid products with a high content of n-alkanes had a very high cetane index and cold filter plugging point, which decreased with an increasing reaction temperature due to the increasing content of isoalkanes and aromatics.

This study describes the co-hydrotreating of mixtures of rapeseed oil (0–20 wt%) with a petroleum feedstock consisting of 90 wt% of straight run gas oil and 10 wt% of light cycle oil. The hydrotreating was carried out in a laboratory flow reactor using a sulfided NiMo/Al2O3 catalyst at a temperature of 345 °C, the pressure of 4.0 and 8.0 MPa, a weight hourly space velocity of 1.0 h−1 and hydrogen to feedstock ratio of 230 m3∙m−3. All the liquid products met the EU diesel fuel specifications for the sulfur content (<10 mg∙kg−1). The content of aromatics in the products was very low due to the high hydrogenation activity of the catalyst and the total conversion of the rapeseed oil into saturated hydrocarbons. The addition of a depressant did not affect the cold filter plugging point of the products. The larger content of n-C17 than n-C18 alkanes suggested that the hydrodecarboxylation and hydrodecarbonylation reactions were preferred over the hydrodeoxygenation of the rapeseed oil. The hydrogen consumption increased with increasing pressure and the hydrogen consumption for the rapeseed oil conversion was higher when compared to the hydrotreating of the petroleum feedstock.