New Developments in Hydrotreating Catalysis : Characterization and Optimization of Niw/A12O3 Catalysts

Alumina supported NiW catalysts with components concentrations varying in a wide range were systematically studied in order to optimize a catalyst for further industrial uses. The genesis of the active phase was examined by using several physicochemical techniques and the catalytic properties were determined in different reactions characteristic of the hydrotreating process i. e. dibenzothiophene and thiophene HDS, biphenyl and pyridine hydrogenation as well as piperidine HDN. The promoting effect of Ni is always observed but the synergy is greatly dependent on the nature of the molecule to be treated. In addition to these activity determinations, the differences in behaviour towards sulfiding conditions and relationships with probe molecules adsorptions suggest that hydrogenation and hydrogenolysis reactions take place on different catalytic sites. The nature of these sites is discussed in terms of the mixed phase model. The selected most active catalyst for performing HDN reactions was studied for real feedstock conversion. Its activity is compared to the properties of conventional nickel molybdenum and nickel tungsten catalysts.