Hydrotreating NiMo/Sepiolite Catalysts: Influence of Catalyst Prepa Ration on Activity for HDS, Hydrogenation and Chain Isomerization Reactions

A series of NiMo catalysts supported on a sepiolite: a) in its natural state, b) modified by acid leaching, and c) modified by cation exchange, have been prepared. The preparation variables studied were: Method of metal deposition, amount of active phase, sepiolite pretreatment, and temperature and time of sulfurization. The cataly tic activity for HDS, hydrogenation, and cracking-isomerization has been studied by feeding a thiophene-cyclohexene-cyclohexane mixture and carrying out the reaction in the following conditions: 300° and 400°C reaction temperature, 20 Kg. cm-2 total pressure, and 3 to 1 molar ratio of H2 to hydrocarbons. (change-para-here) An optimum for HDS and hydrogenation activity was found for a 12% wt MoO3, and 5% wt NiO, prepared by simultaneous impregnation by the pore volume method at Ph = 5.0. The optimum conditions with these catalysts are 400°C and 3 hours of sulfurization. An increase in the acidity of the support produces a decrease of HDS and hydrogenation and an increase of the cracking-isomerization activities. (change-para-here) A good correlation between HDS and the concentration of an XNiO. MoO3 phase is found. The XNiO. MoO3 phase is completely sulfurized to a modified MoS2, while NiMoO4 and MoO3 are only slightly sulfurized.