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Gas-phase hydrogenation of hexanoic acid over P–Mo–V heteropoly compounds in comparison with the constituent Mo and V oxides

Paper ID Volume ID Publish Year Pages File Format Full-Text
42633 45934 2008 5 PDF Available
Title
Gas-phase hydrogenation of hexanoic acid over P–Mo–V heteropoly compounds in comparison with the constituent Mo and V oxides
Abstract

Bulk Keggin heteropoly acids (HPAs) H3+n[PMo12−nVnO40] (n = 0–2) and their Cs+ salts catalyse the gas-phase hydrogenation of hexanoic acid at 350 °C and 1 bar H2 pressure, yielding hexanal together with 6-undecanone and C4–C7 hydrocarbons as the main products. Catalyst acidity (controlled by Cs substitution) has crucial effect on reaction selectivity. Partially substituted Cs salts exhibit high aldehyde selectivity (up to 76% at 70% conversion). Further increasing Cs substitution in HPAs, increases the selectivity to 6-undecanone up to 71–76% at the expense of hexanal and hydrocarbons. Initially crystalline, the post-reaction catalysts become amorphous, with their surface area significantly reduced. This shows that the as-made heteropoly compounds are catalyst precursors rather than the true catalysts. The constituent V2O5 and MoO3 oxides make more active catalysts for hexanoic acid hydrogenation than the P–Mo–V heteropoly compounds. Under reaction conditions, the bulk MoO3 reduces to MoO2, which performs steadily to give 75% hexanal selectivity at 95% conversion. The bulk V2O5, inactive itself, slowly, over 26 h, reduces to the active V2O3 oxide, which shows excellent hydrogenation performance: >97% hexanal selectivity at 80–83% conversion over 72 h on stream.

Graphical abstractP–Mo–V heteropoly compounds (HPCs) catalyse gas-phase hydrogenation of hexanoic acid, yielding hexanal together with 6-undecanone and hydrocarbons. Catalyst acidity (controlled by Cs substitution) has crucial effect on reaction selectivity. The HPCs are catalyst precursors rather than the true catalysts in this reaction. The constituents MoO3 and V2O5 oxides make more active catalysts than the HPCs, providing respectively 75% and 97% hexanal selectivity at 95% and 83% conversion. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Heteropoly compounds; Molybdenum trioxide; Vanadium pentoxide; Hydrogenation; Hexanoic acid; Hexanal; Catalysis
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Gas-phase hydrogenation of hexanoic acid over P–Mo–V heteropoly compounds in comparison with the constituent Mo and V oxides
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 351, Issue 1, 15 December 2008, Pages 88–92
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
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Full-text PDF Download
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