Temperature Programmed Desorption Chromatogram of Oxygen Adsorbed on Nickel Oxide Catalyst

Abstract

The binding state of adsorbed oxygen on nickel oxide catalyst, whichhas been calcined at 600C for 5 hours in air, has been investigated by means oftemperature programed desorption technique. The desorbed oxygen gives two peaks with maxima at 14-46C (peak I) and 150-180 C (peak II) in the range from 0 to600Cas shown in Fig.2 and Table 1. From the slope in Fig.3 the activation energiesofdesorption are found to be 9.0 and 27.4 kcal/mol for the peak I and the peak II, respectively. The results agree well with the distribution of oxidation power ofthe surface excess oxygen (Fig.4) which was determined by Uchijima et al.Itwas also supposed from the comparison of surface area with desorbed amounts of oxygenthat the surface Ni2+ ions of nickel oxide acted as adsorption sites of oxygen.
The desorption chromatogram of oxygen from nickel oxide, which has beencooleddown in helium after the treatment at high temperature for 30-50 hours inhelium, was also examined. And it indicated the production of adsorbed state of oxygen during quenching in helium. The longer the period maintaing in helium at O C was the higher the oxygen peak I became. The oxygen peak II was approximately constant within the limit of this investigation. These results suggestedthat even at OC the excess oxygen in lattice (or strongly adsorbed surface oxygen) diffused and rearranged onto the sites as adsorbed surface oxygen.