CO2 hydrogenation to methanol and dimethyl ether
Abstract: Abstract in English
This thesis describes the synthesis, characterization and the test of new bifunctional catalysts for the one-step synthesis of DME from CO2 and H2. Besides investigations for efficiency enhancement by variation of synthesis parameters, also a new class of catalysts were developed, which show better productivities and selectivities than catalysts reported in literature.
Because of the law of Le Chatelier, the combination of methanol formation and dehydration shifts the equilibrium on the product side, which leads to an increase of the CO2 conversion. Starting from the successful examination of the suitability of the catalyst test station for the reaction of CO2 and H2 to DME with an industrial catalyst, a wide range of acid catalysts was investigated. Catalysts with only Lewis acid centers on the surface lead to low DME production. This points out that the acid strength is the key factor for effective and selective DME production. So the focus was on Brønsted acids, which are more acidic and hydrophobic than Lewis acids. First, Zeolite Beta was tested in the catalyst test station and showed better selectivities and CO2 conversion. But the DME yield was still low, probably because of the still too low acid strength of the acid centers. After this recognition, the choice fell on heteropoly acids, supported on a surface-rich carrier, as acidic compound in the catalyst mixture. With them, it is possible to adjust the strength of acidity by different amounts of HPA on an inorganic carrier. In a 2 to 1 physical mixture with the standard methanol catalyst Cu/ZnO/ZrO2 (CZZ), the best CO2 conversion and good selectivity were reached.
The catalysts were characterized with different analytic methods as FT-IR, pXRD, H2 TPR, N2O-RFC, NH3-TPD, BET, TGA, SEM and EDX.
Due to earlier investigations to methanol synthesis with fluorinated catalysts, the DME catalysts were fluorinated as well. In cooperation with the group of Kemnitz in Berlin, a high surface, partly fluorinated AlFO dehydration catalyst was developed, characterized and tested in DME synthesis. Under reaction conditions, the AlFO did not produce DME but the methanol productivity and CO2 conversion increased. The reason for this increase is not completely understood yet. It could be that some fluorine ions migrate to the methanol catalyst and lower the activation energy so the reaction speed increase. In addition, it’s possible that the AlFO leads to a decrease of the water partial pressure over the CZZ and supports its performance
- Location
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Deutsche Nationalbibliothek Frankfurt am Main
- Extent
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Online-Ressource
- Language
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Englisch
- Notes
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Universität Freiburg, Dissertation, 2019
- Keyword
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Methanol
Methyl ether
Hydrogenation
Carbon dioxide mitigation
Carbon dioxide capture and utilization
Methanol
Dimethylether
- Event
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Veröffentlichung
- (where)
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Freiburg
- (who)
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Universität
- (when)
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2019
- Creator
- DOI
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10.6094/UNIFR/149574
- URN
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urn:nbn:de:bsz:25-freidok-1495744
- Rights
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Der Zugriff auf das Objekt ist unbeschränkt möglich.
- Last update
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25.03.2025, 1:48 PM CET
Data provider
Deutsche Nationalbibliothek. If you have any questions about the object, please contact the data provider.
Associated
Time of origin
- 2019
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