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| 2. |
- Maurina Morais, Eduardo, 1989, et al.
(författare)
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Solvent-free synthesis of protic ionic liquids. Synthesis, characterization and computational studies of triazolium based ionic liquids
- 2022
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Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322. ; 360
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Tidskriftsartikel (refereegranskat)abstract
- A series of triazolium and imidazolium based protic ionic liquids were synthesized using a solvent-free method designed to address several limitations encountered with other commonly used methods. Using this method, pure (98–99% m/m) and dry (128–553 ppm of water) protic ionic liquids were synthesized (in a laboratory scale) without the need for purification methods that require heating the ionic liquid, hence avoiding the common issue of thermal decomposition. This method was also designed to allow for the accurate measurement of acid and base, and for the controlled mixing of both compounds, which is essential to avoid producing impure protic ionic liquids with excess of either acid or base. The system is constructed of only glass and chemically resistant polymer (PTFE and PVDF) parts, which avoid other contaminants that can result from unwanted reactions involving the reagents with common laboratory tools (metallic objects, paper, plastic, etc.). This process is described in detail in the paper as well as in a video. The resulting ionic liquids were carefully analyzed by spectroscopic and thermal methods designed to avoid water absorption, which is known to affect their properties. To complement this experimental characterization, computational chemistry tools were used to assess the ionic liquids’ properties, as well as to assign vibrational modes.
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| 3. |
- Sauer, Christopher, 1993
(författare)
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Green Aromatics: Catalytic Valorisation of bio-derived 2,5-dimethylfuran over Zeolites and Zeotypes
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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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| 4. |
- Maurina Morais, Eduardo, 1989
(författare)
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Synthesis of protic ionic liquids. Challenges and solutions for the synthesis of pure compounds.
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The urgent need to diversify our energy matrix is responsible for a renewed interest in fuel cell technology, which can use hydrogen gas, a renewable green fuel, as an energy source. This technology is currently a commercially available option, however, it still requires technological improvements before it can be widely used for different applications. One way this technology could potentially be improved is by increasing its temperature range of operation by developing new, anhydrous proton conducting materials. Protic ionic liquids, which are organic salts with low melting temperatures, are interesting candidates for this application, since they can conduct protons in the operational conditions of fuel cells and without the need of water. These compounds can be synthesized by a simple acid-base neutralization reaction, but certain considerations must be taken in order to obtain high quality (dry and pure) protic ionic liquids. In this thesis, a series of triazolium and imidazolium based protic ionic liquids were synthesized using a solvent-free method designed to address several limitations encountered with other commonly used methods. Using this method, pure (98-99% m/m) and dry (128-553 ppm of water) protic ionic liquids were synthesized (in a laboratory scale) without the need for purification methods that require heating the ionic liquid, hence avoiding the common issue of thermal decomposition. This method was also designed to allow for the accurate measurement of acid and base, and for the controlled mixing of both compounds, which is essential to avoid producing impure protic ionic liquids with excess of either acid or base. The system is consists of only glass and chemically resistant polymer(PTFE and PVDF) parts, which avoids other contaminants that can result from unwanted reactions involving the reagents with common laboratory tools (metallic objects, paper, plastic, etc.). The resulting ionic liquids were carefully analyzed by spectroscopic and thermal analysis methods designed to avoid water absorption, which is known to affect their properties. To complement this experimental characterization, computational chemistry tools were used to assess the ionic liquids’ properties, as well as to assign vibrational modes.
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| 5. |
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| 6. |
- Börjesson, Karl, 1982, et al.
(författare)
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Conjugated anthracene dendrimers with monomer-like fluorescence
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:38, s. 19846-19850
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Tidskriftsartikel (refereegranskat)abstract
- Two generations of highly emissive conjugated anthracene dendrimers containing up to 9 anthracene units are presented. In these dendrimers, anthracene-like absorption and emission properties are preserved due to the relatively weak electronic coupling between the anthracene units, while evidence of fast crosstalk within the molecular framework is still observed.
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| 7. |
- Halldin Stenlid, Joakim, 1987-
(författare)
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Computational Studies of Chemical Interactions: Molecules, Surfaces and Copper Corrosion
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The chemical bond – a corner stone in science and a prerequisite for life – is the focus of this thesis. Fundamental and applied aspects of chemical bonding are covered including the development of new computational methods for the characterization and rationalization of chemical interactions. The thesis also covers the study of corrosion of copper-based materials. The latter is motivated by the proposed use of copper as encapsulating material for spent nuclear fuel in Sweden.In close collaboration with experimental groups, state-of-the-art computational methods were employed for the study of chemistry at the atomic scale. First, oxidation of nanoparticulate copper was examined in anoxic aqueous media in order to better understand the copper-water thermodynamics in relation to the corrosion of copper material under oxygen free conditions. With a similar ambition, the water-cuprite interface was investigated with regards to its chemical composition and reactivity. This was compared to the behavior of methanol and hydrogen sulfide at the cuprite surface.An overall ambition during the development of computational methods for the analysis of chemical bonding was to bridge the gap between molecular and materials chemistry. Theory and results are thus presented and applied in both a molecular and a solid-state framework. A new property, the local electron attachment energy, for the characterization of a compound’s local electrophilicity was introduced. Together with the surface electrostatic potential, the new property predicts and rationalizes regioselectivity and trends of molecular reactions, and interactions on metal and oxide nanoparticles and extended surfaces.Detailed atomistic understanding of chemical processes is a prerequisite for the efficient development of chemistry. We therefore envisage that the results of this thesis will find widespread use in areas such as heterogeneous catalysis, drug discovery, and nanotechnology.
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| 8. |
- Moth-Poulsen, Kasper, 1978
(författare)
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Molecular Systems for Solar Thermal Energy Storage and Conversion
- 2013
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Ingår i: Organic Synthesis and Molecular Engineering. - Hoboken, NJ, USA : John Wiley & Sons, Inc.. ; , s. 179-196
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Using a synthetic approach to organic materials chemistry, this book sets forth tested and proven methods and practices that make it possible to engineer organic molecules offering special properties and functions. Throughout the book, plenty of real-world examples demonstrate the countless possibilities of creating one-of-a-kind molecules and supramolecular systems to support a broad range of applications. The book explores applications in both materials and bioorganic chemistry, including molecular electronics, energy storage, sensors, nanomedicine, and enzyme engineering.Organic Synthesis and Molecular Engineering consists of fourteen chapters, each one contributed by one or more leading international experts in the field. The contributions are based on a thorough review and analysis of the current literature as well as the authors' firsthand experience in the lab engineering new organic molecules. Designed as a practical lab reference, the book offers:Tested and proven synthetic approaches to organic materials chemistryMethods and practices to successfully engineer functionality into organic moleculesExplanations of the principles and concepts underlying self-assembly and supramolecular chemistryGuidance in selecting appropriate structural units used in the design and synthesis of functional molecules and materialsCoverage of the full range of applications in materials and bioorganic chemistryA full chapter on graphene, a new topic generating intense researchOrganic Synthesis and Molecular Engineering begins with core concepts, molecular building blocks, and synthetic tools. Next, it explores molecular electronics, supramolecular chemistry and self-assembly, graphene, and photoresponsive materials engineering. In short, it offers everything researchers need to fully grasp the underlying theory and then build new molecules and supramolecular systems.
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| 9. |
- Rahm, Martin, et al.
(författare)
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The Molecular Surface Structure of Ammonium and Potassium Dinitramide : A Vibrational Sum Frequency Spectroscopy and Quantum Chemical Study
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:21, s. 10588-10596
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Tidskriftsartikel (refereegranskat)abstract
- Vibrational sum frequency spectroscopy (VSFS) and quantum chemical modeling have been employed to investigate the molecular surface structure of ammonium and potassium dinitramide (ADN and KDN) crystals. Identification of key vibrational modes was made possible by performing density functional theory calculations of molecular clusters. The surface of KDN was found to be partly covered with a thin layer of the decomposition product KNO3, which due to its low thickness was not detectable by infrared and Raman spectroscopy. In contrast, ADN exhibited an extremely inhomogeneous surface, on which polarized dinitramide anions were present, possibly together with a thin layer of NH4NO3. The intertwined use of theoretical and experimental tools proved indispensable in the analysis of these complex surfaces. The experimental verification of polarized and destabilized dinitramide anions stresses the importance of designing surface-active polymer support, stabilizers, and/or coating agents, in order to enable environmentally friendly ADN-based solid-rocket propulsion.
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| 10. |
- Singh, Shivangi, 1996
(författare)
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Investigating hydrothermal stability and influence of water on the activity of Cu-CHA catalysts for NH3-SCR
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Selective catalytic reduction of nitrogen oxides (NOx) with NH3 as a reducing agent (NH3- SCR) is a leading technology for diesel exhaust emission control. Cu-exchanged zeolites with the chabazite structure (Cu-CHA) have emerged as the preferred catalysts thanks to its high activity and hydrothermal stability. Hydrothermal stability is related to dealumination, i.e. removal of aluminum from the zeolite framework to form extraframework aluminum, at high temperatures in the presence of water vapor. Copperexchanged chabazite (Cu-CHA) zeolites have higher hydrothermal stability compared to H-chabazite (H-CHA). To understand the delayed dealumination of Cu-CHA catalysts, we have investigated the reaction paths for dealumination in H-CHA and Cu-CHA using density functional theory (DFT) calculations combined with microkinetic modeling. We find that Cu-CHA and H-CHA follow similar four-step hydrolysis processes, yet the dealumination of Cu-CHA has higher energy barriers, suggesting stabilization of the CHA structure by Cu ions. Furthermore, the preferred reaction product upon complete dealumination of Cu-CHA is a copper-aluminate like species bound to the zeolite framework. The microkinetic analysis quantifies the increased stability of Cu-CHA as compared to H-CHA. In addition to the high-temperature dealumination, we investigated the role of water on low-temperature SCR by experimentally measuring the activity and reaction order of water. The reaction order of water is found to be increasingly negative with increasing water pressure. DFT calculations reveal that water blocks the active Cu-sites and a DFT-based microkinetic model reproduces the measured change of reaction order with water pressure.
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