Temperature programmed oxidation of deactivated Pt/Nb2O5 catalysts

doi:10.1016/S0167-2991(97)80172-3

Studies in Surface Science and Catalysis

Volume 111, 1997, Pages 335-342

https://doi.org/10.1016/S0167-2991(97)80172-3 Get rights and content

This work presents a detailed study of coke deposition on deactivated Pt/Nb₂O₅, Pt/Al₂O₃ and Pt-Sn/Nb₂O₅ catalysts during n-heptane dehydrogenation. The spent catalysts were characterized by means of temperature-programmed oxidation analyzed by mass spectrometry (TPO/MS) and by differential scanning calorimetry (TPO/DSC). The low density of acidic sites and the SMSI effect yielded a more hydrogenated coke on Pt/Nb₂O₅ catalyst than on Pt/Al₂O₃. Addition of tin promotes a decrease of the total coke which is more hydrogenated than the coke on Pt/Nb₂O₅ samples. Analysis of soluble coke suggests a relationship between coke precursors and metallic surface structure.

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Cited by (2)

A study of the promoting effect of noble metal addition on niobia and niobia alumina catalysts
2000, Catalysis Today
The catalytic activity of Nb₂O₅ and Nb₂O₅/Al₂O₃-supported metal catalysts was evaluated in the n-heptane conversion, CO hydrogenation and butadiene hydrogenation. After high temperature of reduction (HTR), the metal adsorption capacity decreases on all the samples, due to the reduction of Nb₂O₅ with subsequent blocking of metal atoms and bimetallic effect.
It was also observed that the activity decay caused by metal-support interaction was remarkably inhibited on the bimetallics with respect to the monometallics by comparing reaction rates after HTR. Thus, the addition of Rh to Co, Cu to Pd and Sn to Pt on niobia catalysts significantly altered the product distribution in Fischer–Tropsch synthesis (FTS) and in the hydrogenation and dehydrogenation of hydrocarbons, respectively. In addition, an unusual bifunctional effect was obtained in Pt/Nb₂O₅/Al₂O₃ catalyst.
Effect of preparation method on the properties of Nb<inf>2</inf>O<inf>5</inf> promoted platinum catalysts
1998, Catalysis Today
Pt/Nb₂O₅ catalysts were prepared on a reducible support by ion exchange and incipient wetness of different platinum salts. The Pt/Nb₂O₅/Al₂O₃ catalysts were prepared with several loading of niobium oxide over alumina, aiming different surface coverages and platinum dispersions. These catalysts were characterized by using different techniques: TPR, DRS, chemisorption of H₂, CO, CO₂ and pyridine. The catalytic activity was evaluated in the n-heptane conversion. Platinum oxide was the main surface precursor on the Nb₂O₅ supported catalysts, while a oxychloroplatinum surface complex was the precursor for Pt/Nb₂O₅/Al₂O₃ catalysts. These different precursors promote the formation of different platinum particle sizes, being the Pt/Nb₂O₅/Al₂O₃ samples more disperse. After high temperature of reduction, the platinum adsorption capacity decrease on all the samples, due to the reduction of Nb₂O₅, and subsequent blocking of surface platinum atoms. Nb₂O₅ and Nb₂O₅/Al₂O₃ supported catalysts are very selective to olefins in the n-heptane conversion. Furthermore, Brönsted acidic sites are formed on Pt/Nb₂O₅/Al₂O₃ catalysts with higher Nb₂O₅ loading, leading to a better stability of the catalysts.

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Temperature programmed oxidation of deactivated Pt/Nb2O5 catalysts

J. Catal.

J. Catal.

Appl. Catal.

Appl. Cat.

Cat. Today

Cat. Today

Catal. Deactiv.

Appl. Catal.

J. Catal.

Appl. Catal.

Temperature programmed oxidation of deactivated Pt/Nb₂O₅ catalysts