Hydrotreating of Atmospheric Gas Oil and Co-Processing with Rapeseed Oil Using Sulfur-Free PMoCx/Al₂O₃ Catalysts

Sulfur-free molybdenum carbides have the potential to replace the conventional sulfided catalysts used for hydrotreating. For these catalysts, it is not necessary to add sulfur to maintain their activity. This fact makes it worthwhile to continue working on improving their hydrotreating efficiency. According to our previous studies, the addition of Co or Ni promotes the hydrotreating activity, but only significant in the case of hydrodesulfurization efficiency (up to 30%). To increase the hydrodenitrogenation efficiency, other promoters, such as phosphorus, can be added. However, most of the published studies do not focus on co-processing or only on hydrotreating of gas oil model molecules at a laboratory scale. In this paper, we build on our previous research by studying five sulfur-free phosphorus-modified MoCx/Al₂O₃ catalysts (0.5, 1.5, 2.5, 3.5, and 4.5 wt %) for the hydrotreating of atmospheric gas oil and co-processing with rapeseed oil (5, 10, and 25 wt %) under industrial conditions (330-350 °C, 5.5 MPa, WHSV 1-2 h^-1). A phosphorus content up to 1.5 wt % promoted the hydrodesulfurization (5-10%) and the hydrodenitrogenation (10-25%) efficiencies of catalysts. Moreover, the triglycerides addition did not significantly decrease the catalyst activity during co-processing. Therefore, our results enable us to define the range of phosphorus addition that enhances MoCx activity using industrial conditions and commercial feedstocks, pointing the way to develop a suitable and sulfur-free alternative to conventional hydrotreating catalysts.