The Effect of Preparation Method on Pt/Nb2O5 Catalysts
The use of the ion-exchange method and the addition of lithium to Pt/Nb2O5 catalysts were investigated in this work, using techniques of temperature-programmed reduction, H2 and CO chemisorption, UV-Vis diffuse reflectance spectroscopy and the conversion of n-heptane as a catalytic test. The superficial precursor present after the calcination step is platinum oxide, as previously observed for Pt/Nb2O5 catalysts prepared by the incipient wetness method. For some of the samples, autoreduction was observed during the calcination step, with the formation of low dispersion metallic platinum. The Pt/Nb2O5 catalysts prepared by ion exchange showed a high yield of olefins, as compared to aromatics, in the conversion of n-heptane. However, a high yield of hydrogenolysis products was also observed. For some of the lithium-containing samples, there was a suppression of dehydrogenation and aromatization reactions, with an increase in central C-C bond hydrogenolysis.
| Main Authors: | , , , , |
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| Format: | Digital revista |
| Language: | English |
| Published: |
Brazilian Society of Chemical Engineering
1998
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| Online Access: | http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66321998000200014 |
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| Summary: | The use of the ion-exchange method and the addition of lithium to Pt/Nb2O5 catalysts were investigated in this work, using techniques of temperature-programmed reduction, H2 and CO chemisorption, UV-Vis diffuse reflectance spectroscopy and the conversion of n-heptane as a catalytic test. The superficial precursor present after the calcination step is platinum oxide, as previously observed for Pt/Nb2O5 catalysts prepared by the incipient wetness method. For some of the samples, autoreduction was observed during the calcination step, with the formation of low dispersion metallic platinum. The Pt/Nb2O5 catalysts prepared by ion exchange showed a high yield of olefins, as compared to aromatics, in the conversion of n-heptane. However, a high yield of hydrogenolysis products was also observed. For some of the lithium-containing samples, there was a suppression of dehydrogenation and aromatization reactions, with an increase in central C-C bond hydrogenolysis. |
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