Catalytic performance of platinum doped tungsten carbide in simultaneous hydrodenitrogenation and hydrodesulphurization

The simultaneous hydrodesulphurization (HDS) and hydrodenitrogenation (HDN) reactions of refractory model compounds were performed for the first time over tungsten carbide doped with platinum before and after preparation (0.3 wt%). It was then compared to that of a pure non-modified W2C. The model compounds were 4,6-dimethyldibenzothiophene (4,6-DMDBT) and carbazole. The catalysts were characterized by X-ray diffraction (XRD). The surface properties were determined by N2 BET specific surface area and chemisorption of CO. Addition of platinum before synthesis of carbide decreased the uptake of CO chemisorption, but did not change significantly the specific surface area and the crystallographic structure of tungsten carbide—β-W2C. Addition of platinum after preparation of carbide did not decreased significantly the specific surface area of W2C but extremely increased the uptake of chemisorption of CO. No influence of platinum on the HDS activity was observed for contact times between 0.08 and 0.31 s. At longer contact time (tc > 0.31 s) the highest activity was observed over W2C–Pt catalyst (platinum doped after preparation) for the HDS of 4,6-DMDBT. The main products were 3,3-DMBPh (along DDS route) and MCHT (along HYD route).A strong influence of platinum, added after preparation (W2C–Pt), was observed for the HDN of carbazole. Indeed, this catalyst was found to be more active in the whole range of applied contact times than W2C and Pt–W2C. It was also more active in the consecutive reaction of isomerization of the main product of the HDN reaction, i.e. bicyclohexyl (BCH) transformed into methylcyclopenthylcyclohexane (MCPCH). Furthermore the activity in HDN over the W2C–Pt catalyst was shown to be highly dependent on the amount of metallic sites introduced by platinum.