Co-hydroprocessing of straight-run gasoil – Rapeseed oil mixture over stacked bed Mo/Al2O3 + NiMo/Al2O3-SAPO-11 catalysts

Abstract

Co-hydroprocessing of straight-run gasoil (SRGO) – rapeseed oil (RSO) mixture over stacked bed sulfide catalytic system (Mo/Al2O3 + NiMo/Al2O3-SAPO-11) was investigated at temperature 350–380 °C, pressure 4.0–7.0 MPa, H2/feed – 1000 Nm3/m3 and liquid hour space velocity 1.0–1.5 h−1. Mo/Al2O3 catalyst was used in the first layer to provide selective conversion of RSO preferably through “direct hydrodeoxygenation” route, excluding COx formation. The influence of temperature and pressure on the product quality and on the conversion of n-octadecane (n-C18H38) produced in hydrodeoxygenation of RSO were studied. The co-processing of 30%RSO/70%SRGO mixture at 350 °C, 5.0 MPa, 1000 Nm3/m3 and 1.5 h−1 gives the product with the acceptable density, sulfur and aromatics contents, but increased cloud point (-1°C). It was shown that a temperature increase from 350 °C to 380 °C resulted in a decrease of cloud point for 12° due to higher n-C18H38 conversion at 380 °C. On the contrary, a pressure increase from 4.0 to 7.0 MPa led to a decrease of n-C18H38 conversion over sulfide Mo/Al2O3 + NiMo/Al2O3-SAPO-11 catalysts. This observation could be explained by higher concentration of NH3 and H2S, by-products of SRGO hydrotreatment, in liquid phase at higher pressure. To prove this hypothesis the effects of NH3 and H2S were investigated on co-processing of 30 wt% RSO in hydrotreated SRGO. It was found that the presence of NH3 was the main reason of inhibiting effect on hydrocracking/ hydroisomerization reactions in co-processing of RSO-SRGO mixtures.