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Investigation of K-promoted Cu-Zn-Al, Cu-X-Al and Cu-Zn-X (X = Cr, Mn) catalysts for carbon monoxide hydrogenation to higher alcohols

Paper ID Volume ID Publish Year Pages File Format Full-Text
40358 45851 2013 10 PDF Available
Title
Investigation of K-promoted Cu-Zn-Al, Cu-X-Al and Cu-Zn-X (X = Cr, Mn) catalysts for carbon monoxide hydrogenation to higher alcohols
Abstract

In this study, we report the effect of Cu/Zn/Al chemical composition and Zn and/or Al substitution by Mn and/or Cr in K-promoted Cu-Zn-Al catalysts for the hydrogenation of CO to higher alcohols. In terms of higher alcohols, the synthesis yielded preferentially primary 2-methyl branched alcohols with up to five carbon atoms, namely 2-methyl-1-propanol and 2-methyl-1-butanol, together with ethanol and propanol. Variation of the Cu/Zn/Al chemical composition showed that the catalyst with a Cu/Zn atomic ratio of 1 and low Al content (K-Cu45Zn45Al10) exhibits the optimum performance in terms of both activity and selectivity to higher alcohols. High Al contents on the other hand favor methanol production at the expense of higher alcohols. It is postulated that due to its acidic nature, alumina reduces the basic sites on the catalyst, thereby retarding the C1→C2 step. Substitution of Zn and/or Al by Mn and/or Cr was found to reduce activity by ∼50%, probably due to the lower exposed copper surface area as indicated by the formation of larger CuO crystals. In terms of selectivity, the most appreciable changes were recorded for the K-Cu45Mn45Al10 catalyst, where a 50% increase in higher alcohol formation was measured, rendering the catalyst the most selective among the investigated materials. Characterization of the catalysts provided some insight on the beneficial influence of Zn substitution by Mn in the K-Cu45Mn45Al10 sample. Inverse correlation between acidity and higher alcohols selectivity was evidenced, in accordance with the general notion that higher alcohol formation requires basic sites and indicates that reduced acidity is needed for the aldol-type condensation reactions. The replacement of Mn by Zn in K-Cu-Mn-Al reduced acidity and thus promoted the production of the desired higher alcohol products.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (195 K)Download as PowerPoint slideHighlights► Higher alcohols were synthesized from syngas over modified K/Cu-Zn-Al catalysts. ► The synthesis yields primary 2-methyl branched alcohols with up to five carbons. ► Cr-substitution favors methanol formation and reduces alcohol chain homologation. ► Substitution of Zn by Mn leads to a 50% increase in HAS compared to the base case. ► Inverse correlation between acidity and higher alcohols selectivity was established.

Keywords
CO hydrogenation to higher alcohols; Cu-Zn-Al catalysts; Alkali promotion; Cr promoter; Mn promoter; Acidity
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Investigation of K-promoted Cu-Zn-Al, Cu-X-Al and Cu-Zn-X (X = Cr, Mn) catalysts for carbon monoxide hydrogenation to higher alcohols
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 455, 30 March 2013, Pages 145–154
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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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