| 1. |
- Sauer, Christopher, 1993, et al.
(author)
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Continuous isomerisation of 2,5-dimethylfuran to 2,4-dimethylfuran over Ga-silicate
- 2024
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In: Chemistry - A European Journal. - 1521-3765 .- 0947-6539. ; 30:20
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Journal article (peer-reviewed)abstract
- 2,4-dimethylfuran has a rare disubstitution pattern in the five-membered heterocyclic furan ring that is highly interesting chemically but challenging to access synthetically. We present a heterogeneously catalysed route to synthesise 2,4-dimethylfuran from commonly available 2,5-dimethylfuran using a zeolite packed-bed flow reactor. As supported by DFT calculations, the reaction occurs inside the zeolite channels, where the acid sites catalyse proton transfer followed by migration of a methyl group. The zeotype Ga-silicate (MFI type) appears superior to an aluminium-containing ZSM-5 by demonstrating higher selectivities and slower catalyst deactivation. This work provides new opportunities for the continuous valorisation of bio-feedstock molecules in the perspective of the emerging biorefinery era.
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| 2. |
- Sauer, Christopher, 1993
(author)
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Green Aromatics: Catalytic Valorisation of bio-derived 2,5-dimethylfuran over Zeolites and Zeotypes
- 2022
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Doctoral thesis (other academic/artistic)abstract
- This thesis discusses the use of biomass as a potentially green feedstock for the chemical industry in the urgent shift away from fossil resources. I elaborate on reasons why we cannot afford to burn virgin biomass for energy production, among them a variety of ecosystem services that forests and other lands provide. In addition, the utilisation of biomass should be focused on products that sequester and lock away carbon for more extended periods, e.g. timber, materials and chemicals. In particular, biomass can be used as an alternative "carbon neutral" feedstock for the chemical industry, where we can preserve the already existing chemical complexity in the bio-based molecules. One example is the upgrading of furans to benzene, toluene and xylene (BTX) aromatics with the help of zeolite catalysis. These aromatics are important commodity chemicals, where the shift to a bio-based resource could make use of already existing knowledge, catalyst and production infrastructure. However, research is necessary to understand these new feedstock molecules and their interaction with the catalysts and to enable the design of applicable catalysts. In order to study the interaction of the furans, in particular 2,5-dimethylfuran (2,5-dmf), I describe and discuss the development of an analytical methodology that utilises infrared spectroscopy and mass spectrometry for the on-line identification and quantification of product molecules during catalytic reactions. This on-line analysis method is then applied to the catalytic conversion of 2,5-dmf to aromatics over a range of zeolite and zeotype catalysts. In-depth studies with ammonia as a probe molecule of the catalytic active acid sites, as well as temperature programmed experiments with ammonia and 2,5-dmf give insights into product distribution, selectivity changes and deactivation of the catalyst. For example, olefins and aromatics are initially preferred products, while with increasing time on stream, the isomerisation of 2,5-dmf becomes dominant. The incorporation of Ga into the zeotype framework, resulting in a Ga-Silicate, shows how targeted catalyst design can increase overall aromatics production. This catalyst is also suitable for selective isomerisation of 2,5-dmf to 2,4-dimethylfuran, which has a rare substitution pattern. Finally, itwas found that the most valuable of BTX, p -xylene, can be produced more selectively when 2,5-dmf is pre-adsorbed onto zeolite ZSM-5 and then released during a temperature programmed product desorption.
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| 3. |
- Sauer, Christopher, 1993
(author)
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Green aromatics for a bio-based economy - Valorization of biomass derived model compounds over zeolites studied by online analysis
- 2021
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Licentiate thesis (other academic/artistic)abstract
- In the strive towards sustainable chemical production, its carbon-based products can no longer be produced from fossil resources but need to be manufactured from a renewable feedstock. Simple aromatic building blocks like benzene, toluene and xylenes (BTX) can be obtained by catalytic valorization of biomass derived platform molecules such as furans provided efficient catalysts can be formulated. To evaluate catalysts for the conversion of furans to BTX and study the involved catalytic reactions, advanced analytical methods are needed. The observation of dynamic responses in catalytic activity and selectivity necessitates time-resolved analysis of rather complex hydrocarbon (HC) streams. In this work, an online analysis method combining Fourier transform infrared spectroscopy and ion molecule reaction mass spectrometry has been developed for the direct monitoring of the effluent stream during conversion of furans over zeolite catalysts. The sampling frequency is shown to be at least 4 per minute, which is considerably higher compared to that of separation-based methods operating on time scales of several minutes. A wide range of HCs and other smaller molecules is identified and individual species quantified simultaneously. The carbon balance of around 90% shows that the vast majority of the complex HC stream is indeed analysed. The developed online analysis has been applied to catalytic step-response experiments, where different zeolites were exposed to concentration steps of 2,5-dimethylfuran at steady temperatures. It is found that the HC stream consists of a range of olefins and aromatics, including BTX. Most interestingly, 2,5-dimethylfuran is isomerized to 2,4-dimethylfuran as well as 2- and 3-methyl-2-cyclopenten-1-one. The formation of BTX is linked to the availability of olefins, which is supported by temperature programmed desorption experiments. Furthermore, to build understanding of the catalytic mechanisms, surface species were characterised in situ by use of diffuse reflectance infrared Fourier transform spectroscopy. It is clear that upon adsorption, 2,5-dimethylfuran interacts with the zeolite structure and undergoes transforming reactions to olefins and aromatics upon temperature increase, but further studies are necessary to comprehend how the rather low selectivity towards BTX can be increased by catalyst design.
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| 4. |
- Sauer, Christopher, 1993, et al.
(author)
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Isomorphous Substitution of Gallium into MFI-Framework Zeolite Increases 2,5-Dimethylfuran to Aromatics Selectivity and Suppresses Catalyst Deactivation
- 2023
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In: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 66, s. 1329-1340
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Journal article (peer-reviewed)abstract
- The valorization of biomass-derived molecules into commodity chemicals is important for the transition to renewable feedstocks. The model platform molecule 2,5-dimethylfuran (2,5-dmf) can be converted into value-added aromatics such as benzene, toluene, and xylenes (BTX) over zeolite catalysts. To explore the role of the zeolite acid site(s) in BTX selectivity, gallium has been isomorphously substituted into the framework, resulting in a Ga-silicate. Compared to the ZSM-5 counterpart, this modification shows enhanced benzene selectivity as well as resistance to deactivation by coke in continuous catalytic performance tests. Guido J. L. de Reijer and Christopher Sauer have contributed equally to this work.
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| 5. |
- Sauer, Christopher, 1993, et al.
(author)
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On-Line Composition Analysis of Complex Hydrocarbon Streams by Time-Resolved Fourier Transform Infrared Spectroscopy and Ion-Molecule Reaction Mass Spectrometry
- 2021
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In: Analytical Chemistry. - : American Chemical Society. - 0003-2700 .- 1520-6882. ; 93:39, s. 13187-13195
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Journal article (peer-reviewed)abstract
- On-line composition analysis of complex hydrocarbon mixtures is highly desirable to determine the composition of process streams and to study chemical reactions in heterogeneous catalysis. Here, we show how the combination of time-resolved Fourier transform infrared spectroscopy and ion-molecule-reaction mass spectrometry (IMR-MS) can be used for compositional analysis of processed plant biomass streams. The method is based on the biomass-derived model compound 2,5-dimethylfuran and its potential catalytic conversion to valuable green aromatics, for example, benzene, toluene, and xylenes (BTX) over zeolite β. Numerous conversion products can be determined and quantified simultaneously in a temporal resolution of 4 min-1without separation of individual compounds. The realization of this method enables us to study activity, selectivity, and changes in composition under transient reaction conditions. For example, increasing isomerization of 2,5-dimethylfuran to 2,4-dimethylfuran, 2-methyl-2-cyclopenten-1-one, and 2-methyl-2-cyclopenten-1-one is observed as the catalyst is exposed to the reactant, while BTX and olefin formation is decreasing. © 2021 The Authors.
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| 6. |
- Sauer, Christopher, 1993, et al.
(author)
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Valorisation of 2,5-dimethylfuran over zeolite catalysts studied by on-line FTIR-MS gas phase analysis
- 2022
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In: Catalysis Science & Technology. - : Royal Society of Chemistry. - 2044-4753 .- 2044-4761. ; 12:3, s. 750-761
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Journal article (peer-reviewed)abstract
- The valorisation of 2,5-dimethylfuran (2,5-dmf) by catalytic fast pyrolysis (CFP) was studied by on-line FTIR-MS gas phase analysis. Zeolite beta, H-ZSM-5 and Cu-ZSM-5 were characterised and used as catalysts. The on-line analysis enables sufficient time resolution to follow subminute transient phenomena, e.g., the impact of catalyst pretreatment and time on stream (TOS) on the reaction selectivity. The results show, that the initial selectivity towards benzene, toluene and xylene (BTX) aromatics is high but decreases with TOS while the isomerisation rates of 2,5-dmf towards 2,4-dimethylfuran and cyclic ketones increase. This indicates the involvement of specific active sites for the different conversion processes. The formation of BTX compounds is linked to the availability of specific olefins, as supported by temperature programmed desorption experiments, which is indicative of aromatisation stemming directly from the olefin pool rather than via Diels-Alder reactions.
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