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The role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalysts for 2-ethyl-9,10-anthraquione hydrogenation

Paper ID Volume ID Publish Year Pages File Format Full-Text
41247 45882 2011 11 PDF Available
Title
The role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalysts for 2-ethyl-9,10-anthraquione hydrogenation
Abstract

Present research concentrates on the role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalyst for 2-ethyl-9,10-anthraquinone (eAQ) hydrogenation. The catalysts with various content of alkali modifier (Me/Pd molar ratio ranges from 0.5 up to 4, Me-alkali metal) were prepared by impregnation of pre-reduced 2%Pd/Al2O3 catalyst with appropriate alkali metal carbonates. The XPS, EDS and TEM measurements show that alkali promoters are introduced into alumina matrix. The microcalorimertic experiments of CO adsorption prove the interaction of CO with catalysts leading to stronger bonding of carbon monoxide by alkali doped catalysts. The presence of alkali promoters in Pd/Al2O3 catalyst plays an essential role in the whole eAQ hydrogenation process. The nature of alkali promoter and its content (Me/Pd atomic ratio) in catalyst are of importance. As the alkalinity of promoter increases going from Li to Cs all the effects caused by their presence become stronger. In the presence of alkali doped catalysts the content of 2-ethyloxoanthrone (OXO, isomer of 2-ethyl-9,10-anthrahydroquinone) formed is higher than that on un-doped 2%Pd/Al2O3. On the other hand, reactions in the “deep hydrogenation” stage comprising the formation of 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone (H4eAQ) and the transformation of OXO to 2-ethylanthrone and other degradation products are remarkably inhibited. In particular, the formation of 2-ethylanthrone via hydrogenolysis of OXO isomer is strongly suppressed. The Cs-doped catalyst exhibits the highest activity to OXO among all the catalysts tested whereas the ability of Cs-doped catalysts to the formation of anthrone is most effectively inhibited. The role of alkali modifiers is considered to be associated with stronger interactions between the catalyst and quinone reagents, and in particular OXO isomer. Moreover, in the reagent adsorption the centres of support nearby the palladium particles may also participate by affecting the mode of reagents adsorption.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (99 K)Download as PowerPoint slideHighlights► Hydrogenation of 2-ethylanthraquinone on alkali-doped Pd/Al2O3 catalyst. ► A role of alkali promoters in activity and selectivity. ► Keto–enol (hydroquinone–oxoanthrone) tautomerization.

Keywords
eAQ, 2-ethyl-9,10-anthraquinone; eAQH2, 2-ethyl-9,10-anthrahydroquinone; OXO, 2-ethyl-10-hydroxy-9-anthrone (2-ethyloxanthrone); H4eAQ, 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone; H4eAQH2, 2-ethyl-5,6,7,8-tetrahydro-9,10-anthrahydroquinone; H8eAQ, 2-et
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The role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalysts for 2-ethyl-9,10-anthraquione hydrogenation
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 402, Issues 1–2, 31 July 2011, Pages 121–131
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us