Effects of Phosphorus Content on Simultaneous Ultradeep HDS and HDN Reactions over NiMoP/Alumina Catalysts

The effects of phosphorus content on competitive hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and hydrodenitrogenation (HDN) of quinoline (Q) over NiMo catalysts were evaluated. Reactions were carried out in a trickle-bed high-pressure flow microreactor. HDS of 4,6-DMDBT was strongly inhibited at Q concentrations of 90 ppmw N, mostly hydrogenation (HYD) route in HDS, suggesting that 4,6-DMDBT and Q compete for the same hydrogenation active sites, which was confirmed by the products' distribution in HDN reactions. Morphology and nature of active sites promoted by phosphorus addition led to different activity performance on competitive HDS and HDN reactions, as evidenced by TOF values. At low concentrations of Q, promoted catalysts maintained activity for both HDS and HDN. High Q levels (above 90 ppmw N) decreased HDS and HDN activity due to stronger inhibition of catalysts. The addition of 1 wt % of phosphorus showed superior activity, attributed to a combination of better dispersed NiMoS active sites and Brønsted acidity.