Co-hydroprocessing and hydrocracking of alternative feed mixture (vacuum gas oil/waste lubricating oil/waste cooking oil) with the aim of producing high quality fuels

Abstract

Hydroprocessing of waste cooking oil (WCO), waste lubricating oil (WLO) and vacuum gas oil (VGO) and mixtures of them are studied for high quality fuels production. The results are compared to VGO hydroprocessing results to illustrate the value added by blending waste oils to VGO, which is one of the well-known conventional hydroprocessing feed. The effect of blending WCO and WLO with VGO has proven a better performance in a fixed bed hydroprocessing reactor, over commercial industrial catalysts manufactured especially to hydroprocess VGO. Blending of WCO and WLO with VGO will reduce environmental pollution resulting from spilling of these wastes in addition to provide an alternative lower-cost feed than pure VGO. A binary bed of hydrotreating catalyst (Ni-Mo oxides supported on Al2O3) and catalyst specified for hydrocracking (Ni–W oxides supported on SiO2/Al2O3) were used. Hydroprocessing experiments were executed at a temperature range 380–440 °C, pressure of 7.0 MPa, LHSV of 1.5 h−1, H2/(HC)feed ratio of 400 Nm3/m3, and different WLO and WCO percentage of (10, 20 wt%). At the specified operating conditions, a high degree of conversion was noticed especially for diesel yield that increases by increasing WLO percentage in the feed mixture. On the other hand, increasing WCO content in the feed mixtures led to higher kerosene and gasoline yields. Higher rates of hydrocracking reactions were achieved by increasing the reaction temperature that was confirmed by the lower percentages of total amount of n-paraffins in the product final mixture with a higher WCO and WLO percent in feed mixture. In conclusion, at all studied temperature ranges it was confirmed that, by increasing the reaction temperature, the gasoline and LPG yields will increase on the expense of kerosene and diesel yields. However, the highest diesel yield could be achieved at 400 °C.