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Cs-doped H4SiW12O40 catalysts for biodiesel applications

Paper ID Volume ID Publish Year Pages File Format Full-Text
42741 45939 2009 9 PDF Available
Title
Cs-doped H4SiW12O40 catalysts for biodiesel applications
Abstract

Cs exchanged silicotungstic acid catalysts of general formula CsxH4−xSiW12O40 (x = 0.8–4) have been synthesised and characterised by a range of techniques including elemental analysis, N2 gas adsorption, XRD, XPS and NH3 flow calorimetry. Cs substitution promotes recrystallisation of the parent H4SiW12O40 polyoxometallate to the Cs4 salt, via a stable intermediate phase formed at compositions between Cs0.8–2.8. This recrystallisation is accompanied by a pronounced rise and subsequent fall in porosity, with a maximum mesopore volume obtained for materials containing 2.8 Cs atoms per Keggin unit. Calorimetry reveals all CsxH4−xSiW12O40 are strong acids, with ΔHθads(NH3) ranging from −142 to 116 kJ mol−1 with increasing Cs content, consistently weaker than their phosphotungstic analogues. CsxH4−xSiW12O40 materials are active catalysts for both C4 and C8 triglyceride transesterification, and palmitic acid esterification with methanol. For loadings ≤0.8 Cs per Keggin, (trans)esterification activity arises from homogeneous contributions. However, higher degrees of substitution result in entirely heterogeneous catalysis, with rates proportional to the density of accessible acid sites present within mesopores.

Graphical abstractCs doped H4SiW12O40 is an effective heterogenous catalyst for the transesterification of C4 and C8 triglycerides (TAG) and the esterification of free fatty acids (FFA). Reactivity correlates with the accessible mesopore acid site density, with optimal performance obtained for Cs1.9–3.4 per Keggin.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Solid acid; Biodiesel; Heterogeneous catalysis; Green Chemsitry; Heteropolyacid
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Cs-doped H4SiW12O40 catalysts for biodiesel applications
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 360, Issue 1, 31 May 2009, Pages 50–58
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