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Ethylbenzene dehydrogenation over Mg3Fe0.5−xCoxAl0.5 catalysts derived from hydrotalcites: Comparison with Mg3Fe0.5−yNiyAl0.5 catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
41686 45896 2011 9 PDF Available
Title
Ethylbenzene dehydrogenation over Mg3Fe0.5−xCoxAl0.5 catalysts derived from hydrotalcites: Comparison with Mg3Fe0.5−yNiyAl0.5 catalysts
Abstract

A series of Mg3Fe0.5−xCoxAl0.5 (x = 0–0.5) catalysts were prepared from hydrotalcite precursors and their activities in the dehydrogenation of ethylbenzene were compared with those of a series of Mg3Fe0.5−yNiyAl0.5 (y = 0–0.5) catalysts also derived from hydrotalcite. The hydrotalcites prepared by co-precipitation were calcined at 550 °C to the mixed oxides with a high surface area of 150–240 m2 gcat−1; they were composed of Mg(Fe,Me,Al)O periclase and Mg(Me)(Fe,Al)2O4 spinel (Me = Co or Ni). Bimetallic Fe3+–Co2+ system showed a synergy, i.e., an increase in the activity, whereas Fe3+–Ni2+ bimetallic system showed no synergy. The high styrene yield was obtained on Mg3Fe0.1Co0.4Al0.5; however, a large substitution of Fe3+ with Co2+ caused a decrease in styrene selectivity along with coking on the catalysts, due to an isolation of CoOx on the catalyst surface. The highest yield as well as the highest selectivity for styrene production was obtained at x = 0.25 at time on stream of 30 min. The coprecipitation at pH = 10.0 and the composition of Mg3Fe0.25Co0.25Al0.5 were the best for preparing the active catalyst. This is partly due to the formation of a good hydrotalcite structure. On this catalyst, the active Fe3+ species was reduced at a low temperature by the Fe3+–Co2+ bimetal formation, leading to a high activity. Simultaneously, the amount of reducible Fe3+ was the smallest, resulting in a high stability of the active Fe3+ species. It is likely that the dehydrogenation was catalyzed by the reduction–oxidation between Fe3+ and Fe2+ and that Co2+ assisted the reduction–oxidation by forming Fe3+–Co2+ (1/1) bimetallic active species.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (18 K)Download as PowerPoint slideResearch highlights► Styrene production by ethylbenzene dehydrogenation. ► Mg3Fe0.25Co0.25Al0.5 catalyst derived from hydrotalcites. ► Fe3+–Co2+ (1/1) active species.► Comparison with Mg3Fe0.25Ni0.25Al0.5 catalyst. ► Synergy observed on Mg3Fe0.25Co0.25Al0.5 catalyst.

Keywords
Ethylbenzene dehydrogenation; Styrene; Mg3Fe0.25Co0.25Al0.5 catalyst; Fe3+–Co2+ active species; Hydrotalcite
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Ethylbenzene dehydrogenation over Mg3Fe0.5−xCoxAl0.5 catalysts derived from hydrotalcites: Comparison with Mg3Fe0.5−yNiyAl0.5 catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 396, Issues 1–2, 15 April 2011, Pages 107–115
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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