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Effect of the structural and morphological properties of Cu/ZnO catalysts prepared by citrate method on their activity toward methanol synthesis from CO2 and H2 under mild reaction conditions

Paper ID Volume ID Publish Year Pages File Format Full-Text
55314 47047 2012 10 PDF Available
Title
Effect of the structural and morphological properties of Cu/ZnO catalysts prepared by citrate method on their activity toward methanol synthesis from CO2 and H2 under mild reaction conditions
Abstract

Methanol synthesis from CO2 + H2 was studied at mild reaction conditions (140–250 °C and 7 bar) over Cu/ZnO catalysts prepared by citrate method. The copper content and calcination temperatures were varied so as to obtain a wide range in copper particle size (2–12 nm). Methanol formation rates vary between 0.84 and 2.98 × 10−3 s−1 at 180 °C. Methanol selectivity can attain 100% at temperatures lower than 160 °C. At higher temperatures, CO formation by reverse water gas shift reaction is highly favored. The apparent activation energy for methanol formation is in the range 8–10 kcal/mol, whereas that of CO formation is much higher (29–32 kcal/mol). The methanol formation rates depend linearly on the amount of exposed copper atoms, whereas for CO formation there is no clear correlation, showing that special surface sites are responsible for CO formation. The size of copper particles greatly influences the selectivity to methanol at constant CO2 conversion. Larger particles (10–12 nm) are much more selective than smaller ones (2–3 nm), this effect is enhanced when CO2 conversion is low. Catalysts prepared by citrate method are much more active than a reference catalyst prepared by coprecipitation. The activity of CuO + ZnO catalysts prepared by mechanically mixing of CuO and ZnO present activity comparable with that of Cu/ZnO catalysts prepared by citrate method, whereas pure copper and ZnO are not active at these conditions. That strongly suggests that activity is defined by a good contact between Cu0 and ZnO, whereas the selectivity depends on the morphology of copper nanoparticles.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (108 K)Download as PowerPoint slideHighlights► Methanol synthesis at mild conditions from CO2 + H2 on Cu/ZnO catalysts prepared by citrate method. ► Methanol formation rates increase with the amount of copper surface atoms. ► Selectivity to methanol is enhanced over large copper clusters. ► Selectivity to CO is favored over small copper particles. ► The contact between Cu0 and ZnO phases is crucial to have active catalysts.

Keywords
CO2 hydrogenation; Methanol synthesis; Low temperature; Cu/ZnO catalysts; Citrate method; Structure-sensitivity; Phases cooperation
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Effect of the structural and morphological properties of Cu/ZnO catalysts prepared by citrate method on their activity toward methanol synthesis from CO2 and H2 under mild reaction conditions
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 197, Issue 1, 15 December 2012, Pages 109–118
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