Base-metal catalysis for the hydrogenation of acetic acid

Lynch, Ailsa S. (2014) Base-metal catalysis for the hydrogenation of acetic acid. PhD thesis, University of Glasgow.

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Increasing global ethanol consumption has revived research into a variety of route for the synthesis of ethanol. One such route is via the hydrogenation of acetic acid, for which a catalyst with significant acid tolerance is required. The objective of finding an active, acid tolerant base metal catalyst was central to this project.
In this study, a commercial methanol synthesis catalyst was initially investigated for its viability as an acid hydrogenation catalyst, following the production of ethanol when acetic acid was passed over it in a different study [1]. The methanol synthesis catalyst was not a viable option due to deactivation, but the use of a copper based system was shown to be active, in line with other studies [2].
Copper based catalysts were tested in both integral and differential reactor systems. The copper catalysts, with metal loadings of 5 wt.% and 10 wt.%, showed some activity towards the production of ethanol, but not in comparable quantities to those observed with the high copper content methanol synthesis catalyst.
The effect of higher acetic acid concentrations, up to 20 mol.%, within an atmospheric fixed bed system were investigated, and showed that copper based catalysts were physically compromised by the presence of acetic acid. Deactivation and degradation of this catalyst upon exposure to acetic acid, especially at higher concentrations, meant that it was not appropriate for this process.
The propensity of the copper catalysts to degrade in the presence of acetic acid led to other base metal systems being investigated, in the form of nickel and cobalt catalysts. All three base metal systems were investigated within a differential reactor to show direct comparisons of each catalyst at 10 wt.% and 20 wt.% metal loadings. This research showed that cobalt based systems were the most active of the metals tested at the two separate loadings.

A study into the effect of the catalyst support using an 10 wt.% cobalt loading, on a range of supports, showed that alumina was the superior support for the selective hydrogenation of acetic acid to ethanol. The other supports investigated were silica, titania and zinc oxide.

Comprehensive testing of the catalysts prepared with cobalt, copper and nickel, identified that the 20 wt.% cobalt on alumina was the most stable, in terms of activity and catalyst integrity, and active catalyst of those investigated at an optimal reaction temperature.

1. Blain, S., Ditzel, E., and Jackson, S. D., A mechanistic study into the effect of acetic acid on methanol synthesis. Catal. Sci., 2012. 2(4): p. 778-783.
2. Cressely, J., Farkhani, D., Deluzarche, A., and Kiennemann, A., The Evolution of Carboxylate Species in the Framework of CO-H2 Synthesis - Reduction of Acetic-Acid on the Co,Cu,Fe System. Mat. Chem. Phys., 1984. 11(5): p. 413-431.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Hydrogenation, acetic acid, heterogeneous catalysis, base metals, catalysts.
Subjects: Q Science > QD Chemistry
T Technology > TP Chemical technology
Colleges/Schools: College of Science and Engineering > School of Chemistry
Supervisor's Name: Jackson, Professor S. David
Date of Award: 2014
Depositing User: Miss Ailsa Lynch
Unique ID: glathesis:2014-5162
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 21 May 2014 14:15
Last Modified: 29 May 2017 12:27

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