The influence of Fe on the dispersion, electronic state, sulfur-resistance and catalysis of platinum supported on KL zeolite

The influence of Fe as a second metal component on the decomposition, dispersion and catalysis of the platinum amine complex in KL zeolite has been investigated. TG-DTA was used to measure the decomposition of the complex in KL and Fe/KL, zeolites. XPS showed that Pt2+ and in particular Fe3+ ions show strong surface enrichment after calcination. Partial reduction of Fe3+ was found to occur both under calcination (autoreduction) and reduction (in a hydrogen atmosphere) treatments, as evidenced by an increase of the ESR signal at g = 2.3. Both, ESR and TPR results revealed that platinum catalyzes the reduction of Fe3+, leading to a nearly 100 K decrease of the reduction temperature. Bimetallic Pt-Fe particles were thus produced, exhibiting better dispersion than mono-metallic Pt/KL zeolite, as determined by TEM. The catalytic properties of Pt-Fe/KL zeolite Varied with the amount of Fe. At 0.3 wt.% Fe, the catalyst was found to show both excellent n-hexane aromatization reactivity and higher sulfur-resistance. An interpretation of the differences in the catalytic performance based on the particle size and electronic state of active platinum by Pt-Fe interaction is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.