The effect of potassium on Ni/Al2O3 catalyst in relation to CO/H2 reaction was studied. XRD examinations and extensive adsorption measurements (H2, O2 and CO) have shown a small effect on nickel dispersion. At the same time the measurements of thermal effect revealed that potassium decreases heat of O2 adsorption and increase heat of CO adsorption, which proves that the promoter is located on nickel surface. Temperature-programmed studies showed that potassium significantly retards hydrogenation of pre-adsorbed CO and this result was confirmed by steady state examination of CO/H2 reaction.
A series of carbon supported nickel catalysts of various metal dispersion was characterized by temperature-programmed reduction and adsorption of hydrogen, carbon monoxide and oxygen. The examinations showed that some carbon species appear on nickel surface in the course of routine purging of the catalysts from hydrogen. The species weaken the adsorption of hydrogen but does not affect the adsorption of carbon monoxide. Dispersion of nickel determined from hydrogen, carbon monoxide and oxygen adsorption was the same, which indicates the usefulness of these adsorbates for characterizing of carbon supported nickel catalysts.
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