EFFECT OF CARBON PROPERTIES ON THE PREPARATION AND ACTIVITY OF CARBON-SUPPORTED MOLYBDENUM SULFIDE CATALYSTS

Several sulfided Mo catalysts supported on activated carbons were prepared in order to show the effect of the porosity, ash content, and oxygen surface groups of the carbon supports on the preparation and thiophene hydrodesulfuration activity of the catalysts. The five original activated carbons were washed with HCl to eliminate the ash content, reduced in hydrogen at high temperature to eliminate oxygen surface groups, and oxidized with hydrogen peroxide to introduce new oxygen surface groups, the porosity remaining constant after these treatments. In this way the effect of the surface properties of the support in both the preparation and activity of the catalysts could be evaluated separately. The effect of these properties on the preparation (adsorption from ammonium heptamolybdate) of the catalysts is as follows: (a) increasing surface area and porosity of the carbon facilitates the loading of Mo; (b) ash content has a relatively small (but significant) negative effect in the adsorption of the metal precursor; and (c) oxygen surface groups of the carbon support increase the adsorption of the metal precursor. The effect on HDS activity is: (a) specific activity increases with surface area of the support up to about 1000 m(2)/g, remaining almost constant thereafter; (b) ash content has a negative effect on the catalytic activity; and (c) the oxygen surface groups of the carbon support have a negative effect on the catalytic activity.