Denitrogenation-selective hydrotreating catalyst

This paper describes the development of a catalyst which gives an unusual combination of high HDN and low HDS activity. The significance of this finding is that HDN and HDS can be substantially uncoupled. In other words, enhancing HDS activity is not necessarily a prerequisite to enhancing HDN activity. This result also suggests that nitrogen is not necessarily more difficult to remove than sulfur, although this is expected to be the case based on the carbon-heteroatom bond strength in aromatic systems. The catalysts we report here are unsupported, low surface area iron-promoted molybdenum and tungsten sulfides generated by thermal decomposition of bis-(diethylenetriamine) iron thiomolybdate and its tungsten analog. A heterometallic metal sulfur complex of this kind may be called self-promoted, since the primary and promoter metals are molecularly associated with each other in a single complex. Unlike commercial catalysts, the catalyst precursor is already in a sulfide form. The layout of the paper consists of catalyst preparation and characterization, followed by activity/selectivity tests, and finally some concluding remarks.