Studies to develop high activity MoS2: crystallography, thermal analysis and catalytic activity
Nowadays environmental restrictions set the organosulfur compounds content of transport fuel up to 10 ppm. Ultra low sulfur diesel is obtained by deep hydrodesulfurization process. The commercial catalysts are nickel or cobalt promoted Mo/WS2 supported over alumina. Several methods to produce the catalysts are known and it has been observed that carbon content influences over improved activity and selectivity. This work was devoted to determine the crystal structures and to study the thermal behavior of a serie of tetraalkylammonium thiomolybdates and tungstates as precursors of Mo/WS2. Also the promoter containing compounds of Co/Ni(diethylenetriamine)2MoS4 were studied. Thermal decomposition reactions of the compounds were determined by the DTA-TG-MS method. Several molar ratios of blends of tetrapropylammonium thiomolybdate and nickel containing precursors were decomposed to obtain promoted MoS2. The catalyst was tested by the HDS of DBT showing the double activity of a comercial catalyst and good selectivity for the direct desulfurization pathway.