Jf. Jia et al., Studies of the roles of Sn or Fe on gamma-Al2O3-supported Pt catalysts by CO adsorption microcalorimetry and dehydrogenation reaction of C-4 alkanes, SCI CHINA B, 41(6), 1998, pp. 606-615
CO adsorption microcalorimetry was employed in the study of gamma-Al2O3-sup
ported Pt, Pt-Sn and Pt-Fe catalysts. The results indicated that the initia
l differential heat of CO adsorption of the Pt/gamma-Al2O3 catalyst was 125
kJ/mol. As CO coverage increased, the differential heat of adsorption decr
eased. At higher coverages, the differential heat of adsorption decreased s
ignificantly. 60% of the differential heat of CO adsorption on the Pt/gamma
-Al2O3 catalyst was higher than 100 kJ/mol. No significant effect on the in
itial differential heat was found after adding Sn and Fe to the Pt/gamma-Al
2O3 catalyst. The amount of strong CO adsorption sites decreased, while the
portion of CO adsorption sites with differential heat of 60-110 kJ/mol inc
reased after increasing the Sn or Fe content. This indicates that the surfa
ce adsorption energy was changed by adding Sn or Fe to Pt/gamma-Al2O3. The
distribution of differential heat of CO adsorption on the PI-Sn(C)/gamma-Al
2O3 catalyst was broad and homogeneous. Comparison of the dehydrogenation p
erformance of C-4 alkanes with the number of CO adsorption sites with diffe
rential heat of 60-110 kJ/mol showed a good correlation. These results indi
cate that the surface Pt centers with differential heats of 60-110 kJ/mol f
or CO adsorption possess superior activity for the dehydrogenation of alkan
es.