ISSN:
1572-879X
Keywords:
Pt–Sn/Al2O3, coking of
;
Pt–Sn/Al2O2, regeneration of after coking
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Infrared spectra of adsorbed CO have been used as a probe to monitor changes in Pt site character induced by the coking of Pt/Al2O3 and Pt–Sn/Al2O3 catalysts by heat treatment in heptane/hydrogen. Four distinguishable types of Pt site for the linear adsorption of CO on Pt/Al2O3 were poisoned to different extents showing the heterogeneity of the exposed Pt atoms. The lowest coordination Pt atoms (ν(CO) 〈 2030 cm−1) were unpoisoned whereas the highest coordination sites in large ensembles of Pt atoms (2080 cm−1) were highly poisoned, as were sites of intermediate coordination (2030–2060 cm−1). Sites in smaller two‐dimensional ensembles of Pt atoms (2060–2065 cm−1) were partially poisoned, as were sites for the adsorption of CO in a bridging configuration. The addition of Sn blocked the lowest coordination sites and destroyed large ensembles of Pt by a geometric dilution effect. The poisoning of other sites by coke was impeded by Sn, this effect being magnified for Cl‐containing catalyst. Oxidation or oxychlorination of coked catalyst at 823 K followed by reduction completely removed coke from the catalyst surfaces.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1019023210896
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