The reduction behavior of Y-Al2O3 supported iron and platinum-iron catalysts was studied by TPR combined in situ 57Fe MBS. The results indicated that Fe3+ is highly dis-persed on the Y-Al2O3 surface for all the sample...The reduction behavior of Y-Al2O3 supported iron and platinum-iron catalysts was studied by TPR combined in situ 57Fe MBS. The results indicated that Fe3+ is highly dis-persed on the Y-Al2O3 surface for all the samples containing iron before the reduction. No Fe was found in the reduction process. The Fe3+ was reduced to Fe2+ in tetrahedral vacancy first in Pt-Fe/Y-Al2O3 sample in TPR process. The TPR processes of all supported iron samples are very different from those of α-Fe2O3.展开更多
CO adsorption microcalorimetry was employed in the study of γ-Al-2O-3-supported Pt, Pt-Sn and Pt-Fe catalysts. The results indicated that the initial differential heat of CO adsorption of the Pt/γ-Al-2O-3 catalyst w...CO adsorption microcalorimetry was employed in the study of γ-Al-2O-3-supported Pt, Pt-Sn and Pt-Fe catalysts. The results indicated that the initial differential heat of CO adsorption of the Pt/γ-Al-2O-3 catalyst was 125 kJ/mol. As CO coverage increased, the differential heat of adsorption decreased. At higher coverages, the differential heat of adsorption decreased significantly. 60% of the differential heat of CO adsorption on the Pt/γ-Al-2O-3 catalyst was higher than 100 kJ/mol. No significant effect on the initial differential heat was found after adding Sn and Fe to the Pt/γ-Al-2O-3 catalyst. The amount of strong CO adsorption sites decreased, while the portion of CO adsorption sites with differential heat of 60110 kJ/mol increased after increasing the Sn or Fe content. This indicates that the surface adsorption energy was changed by adding Sn or Fe to Pt/γ-Al-2O-3. The distribution of differential heat of CO adsorption on the Pt-Sn（C）/γ-Al-2O-3 catalyst was broad and homogeneous. Comparison of the dehydrogenation performance of C-4 alkanes with the number of CO adsorption sites with differential heat of 60110 kJ/mol showed a good correlation. These results indicate that the surface Pt centers with differential heats of 60110 kJ/mol for CO adsorption possess superior activity for the dehydrogenation of alkanes.展开更多
Surface structures of Pt-Sn and Pt-Fe bimetallic catalysts have been investigated by means of Mssbauer spectroscopy, Pt-L<sub>Ⅲ</sub>-edge EXAFS and H<sub>2</sub>-adsorption. The results sho...Surface structures of Pt-Sn and Pt-Fe bimetallic catalysts have been investigated by means of Mssbauer spectroscopy, Pt-L<sub>Ⅲ</sub>-edge EXAFS and H<sub>2</sub>-adsorption. The results showed that the second component, such as Sn or Fe, remained in the oxidative state and dispersed on the γ-Al<sub>2</sub>O<sub>3</sub> surface after reduction, while Pt was completely reduced to the metallic state and dispersed on either the metal oxide surface or the γ-Al<sub>2</sub>O<sub>3</sub> surface. By correlating the distribution of Pt species on different surfaces with the reaction and adsorption performances, it is proposed that two kinds of active Pt species existed on the surfaces of both catalysts, named M<sub>1</sub> sites and M<sub>2</sub> sites. M<sub>1</sub> sites are the sites in which Pt directly anchored on the γ-Al<sub>2</sub>O<sub>3</sub> surface, while M<sub>2</sub> sites are those in which Pt anchored on the metal oxide surface. M<sub>1</sub> sites are favorable for low temperature H<sub>2</sub> adsorption, and responsible for the hydrogenolysis reaction and carbon deposition, while M<sub>2</sub> sites which adsorb more H<sub>2</sub> at higher展开更多
文摘The reduction behavior of Y-Al2O3 supported iron and platinum-iron catalysts was studied by TPR combined in situ 57Fe MBS. The results indicated that Fe3+ is highly dis-persed on the Y-Al2O3 surface for all the samples containing iron before the reduction. No Fe was found in the reduction process. The Fe3+ was reduced to Fe2+ in tetrahedral vacancy first in Pt-Fe/Y-Al2O3 sample in TPR process. The TPR processes of all supported iron samples are very different from those of α-Fe2O3.
文摘CO adsorption microcalorimetry was employed in the study of γ-Al-2O-3-supported Pt, Pt-Sn and Pt-Fe catalysts. The results indicated that the initial differential heat of CO adsorption of the Pt/γ-Al-2O-3 catalyst was 125 kJ/mol. As CO coverage increased, the differential heat of adsorption decreased. At higher coverages, the differential heat of adsorption decreased significantly. 60% of the differential heat of CO adsorption on the Pt/γ-Al-2O-3 catalyst was higher than 100 kJ/mol. No significant effect on the initial differential heat was found after adding Sn and Fe to the Pt/γ-Al-2O-3 catalyst. The amount of strong CO adsorption sites decreased, while the portion of CO adsorption sites with differential heat of 60110 kJ/mol increased after increasing the Sn or Fe content. This indicates that the surface adsorption energy was changed by adding Sn or Fe to Pt/γ-Al-2O-3. The distribution of differential heat of CO adsorption on the Pt-Sn（C）/γ-Al-2O-3 catalyst was broad and homogeneous. Comparison of the dehydrogenation performance of C-4 alkanes with the number of CO adsorption sites with differential heat of 60110 kJ/mol showed a good correlation. These results indicate that the surface Pt centers with differential heats of 60110 kJ/mol for CO adsorption possess superior activity for the dehydrogenation of alkanes.
文摘Surface structures of Pt-Sn and Pt-Fe bimetallic catalysts have been investigated by means of Mssbauer spectroscopy, Pt-L<sub>Ⅲ</sub>-edge EXAFS and H<sub>2</sub>-adsorption. The results showed that the second component, such as Sn or Fe, remained in the oxidative state and dispersed on the γ-Al<sub>2</sub>O<sub>3</sub> surface after reduction, while Pt was completely reduced to the metallic state and dispersed on either the metal oxide surface or the γ-Al<sub>2</sub>O<sub>3</sub> surface. By correlating the distribution of Pt species on different surfaces with the reaction and adsorption performances, it is proposed that two kinds of active Pt species existed on the surfaces of both catalysts, named M<sub>1</sub> sites and M<sub>2</sub> sites. M<sub>1</sub> sites are the sites in which Pt directly anchored on the γ-Al<sub>2</sub>O<sub>3</sub> surface, while M<sub>2</sub> sites are those in which Pt anchored on the metal oxide surface. M<sub>1</sub> sites are favorable for low temperature H<sub>2</sub> adsorption, and responsible for the hydrogenolysis reaction and carbon deposition, while M<sub>2</sub> sites which adsorb more H<sub>2</sub> at higher
