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Accelerated study of the citral–acetone condensation kinetics over activated Mg–Al hydrotalcite

Paper ID Volume ID Publish Year Pages File Format Full-Text
43593 45978 2007 9 PDF Available
Title
Accelerated study of the citral–acetone condensation kinetics over activated Mg–Al hydrotalcite
Abstract

The kinetics of the citral–acetone condensation to pseudoionone (PS) over activated Mg–Al hydrotalcite (meixnerite) was studied in a 16 parallel-batch reactor set-up varying the temperature, catalyst amount, and molar acetone-to-citral (A/C) ratio. Tests with different stirring speeds and particle sizes were conducted in order to exclude the presence of mass transport limitations. The A/C ratio is a key reaction descriptor. The initial rate of pseudoionone formation exhibits a maximum at A/C = 3, leading to a PS selectivity of 100%. At higher or lower A/C ratios, diacetone alcohol is the main by-product and at A/C < 2 the product of citral self-condensation is additionally formed. Due to this, the pseudoionone selectivity at extreme A/C ratios decreases to 70–80%. The amount of carbonaceous deposits was determined by thermogravimetry and increased as the A/C ratio decreased. A Langmuir–Hinshelwood model involving acidic Al3+ and basic OH− sites and the surface reaction as rate-determining step described well the experimental data. The position of the optimal A/C ratio is determined by the relative ratio of adsorption constants of the reactants on the catalyst, being one order of magnitude larger in citral than in acetone. This feature can be generalized to aldol reactions involving other substrates.

Graphical abstractThe kinetics of the citral–acetone condensation over activated Mg–Al hydrotalcite has been systematically studied in an automated 16 parallel-batch reactor. Three days of experimentation generated 150 data points with high accuracy and reproducibility in a broad range of conditions. The acetone-to-citral ratio is a key reaction descriptor. The experiments have been adequately described by means of a Langmuir–Hinshelwood scheme. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Solid-base catalysis; Aldol condensation; Citral; Acetone; Activated hydrotalcite; High-throughput testing; Kinetics
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Accelerated study of the citral–acetone condensation kinetics over activated Mg–Al hydrotalcite
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 325, Issue 1, 30 May 2007, Pages 121–129
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