Loading of Metals on Carbon Supports

There are reports indicating that metal adsorption and dispersion can be enhanced by applying ultrasound during impregnation. For example, a slurry of the fine carbon particles prepared by ultrasonic radiation was mixed with the aqueous solution of the active metal precursors.The resultant catalyst was dried at 383 K. This was followed by reduction at 473 K before the catalyst was used for coal liquefaction. 

The study of Charry et al is another example of the effect of the impregnation method on catalyst activity. These authors prepared two series of Mo/AC catalysts, i.e. one involving the incipient-wetness impregnation using the aqueous solution of ammonium molybdate and the other using the etha-nolic solution of the Mo-acetylacetonate. The Mo/AC catalysts prepared by the latter method exhibited much higher HDS activity (thiophene, 673 K and atm. H2) for all Mo loadings. 

Rondon et reported that the pH of the solution of Mo precursor such as (NH4)eMo7024.4H20 had a pronounced effect on the amount of Mo adsorbed by AC. Decreasing pH from 9 to 2 increased the amount of adsorbed 

Mo from about 0.2 to almost 14wt.%. This was attributed to an electrostatic interaction of Mo ions with protonated OH groups on the AC support. 

It has been established that catalyst performance depends on the amount of active metal loaded on carbon. Apparently, there may be an optimum amount 

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