Hydrogen chemisorption/pulse reoxidation measurements

Results of Hydrogen Chemisorption/Pulse Reoxidation Measurements over Activated Silica-Supported Cobalt Catalysts Calcined at 350°C Using either Flowing Air or 5% Nitric Oxide in Nitrogen... 

In agreement with the TPR results, the hydrogen chemisorption/pulse reoxidation data provided in Table 8.3 indicate that, indeed, the extents of reduction for the air calcined samples are -20% higher upon standard reduction at 350°C (compare 02 uptake values). Yet in spite of the higher extent of reduction, the H2 desorption amounts, which probe the active site densities (assume H Co = 1 1), indicate that the activated nitric oxide calcined samples have higher site densities on a per gram of catalyst basis. This is due to the much smaller crystallite that is formed. The estimated diameters of the activated air calcined samples are between 27 and 40 nm, while the H2-reduced nitric oxide calcined catalysts result in clusters between 10 and 20 nm, as measured by chemisorption/pulse reoxidation. 

The results confirm that the novel metal nitrate conversion method using nitric oxide in place of air advocated by Sietsma et al. in patent applications WO 2008029177 and WO 2007071899 leads to, after activation in H2, catalysts with smaller cobalt crystallites, as measured by EXAFS and hydrogen chemisorption/ pulse reoxidation. In spite of the lower extent of cobalt reduction for H2-activated nitric oxide calcined catalysts, which was recorded by TPR, XANES, EXAFS,... 

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