A5078062167- Zeolite Catalysis and Synthesis
- Catalytic Processes in Materials Science
- Mesoporous Materials and Catalysis
- Advanced NMR Techniques and Applications
- Metal-Organic Frameworks: Synthesis and Applications
- Catalysis and Oxidation Reactions
- Chemical Synthesis and Characterization
- Catalysts for Methane Reforming
- Catalysis and Hydrodesulfurization Studies
- X-ray Diffraction in Crystallography
- Catalysis for Biomass Conversion
- Synthetic Organic Chemistry Methods
- Carbon dioxide utilization in catalysis
- Asymmetric Hydrogenation and Catalysis
- Polyoxometalates: Synthesis and Applications
- Crystallization and Solubility Studies
- Advancements in Battery Materials
- Organometallic Complex Synthesis and Catalysis
- biodegradable polymer synthesis and properties
- CO2 Reduction Techniques and Catalysts
- Nanocomposite Films for Food Packaging
- NMR spectroscopy and applications
- Surface Chemistry and Catalysis
- Muon and positron interactions and applications
- Radical Photochemical Reactions
University of Stuttgart
2016-2025
Institute of Technical Chemistry
2023-2025
Stuttgart Observatory
2018-2021
University of Oslo
2017-2020
SINTEF
2018-2019
SINTEF Industry
2018-2019
Cu-exchanged zeolites possess active sites that are able to cleave the C–H bond of methane at temperatures ≤200 °C, enabling its selective partial oxidation methanol. Herein we explore this process over Cu-SSZ-13 materials. We combine activity tests and X-ray absorption spectroscopy (XAS) thoroughly investigate influence reaction parameters material elemental composition on productivity Cu speciation during key steps. find CuII moieties responsible for conversion formed in presence O2 high...
The direct conversion of methane to methanol (MTM) is a reaction that has the potential disrupt great part synthesis gas-derived chemical industry. However, despite many decades research, active enough catalysts and suitable processes for industrial application are still not available. Recently, several copper-exchanged zeolites have shown considerable activity selectivity in MTM reaction. Understanding nature site these materials essential any further development field. Herein, we apply...
Little is known on the early stages of methanol-to-olefin (MTO) conversion over H-SAPO-34, before steady-state with highly active polymethylbenzenium cations as most important intermediates reached. In this work, formation and evolution carbenium ions during MTO a H-SAPO-34 model catalyst were clarified via 1H MAS NMR 13C NMR. Several initial species (i.e., three-ring compounds, dienes, polymethylcyclopentenyl, polymethylcyclohexenyl cations) were, for first time, directly verified...
Ru/Al2O3 is a highly stable, but less active catalyst for methanation reactions. Herein we report an effective approach to significantly improve its performance in the of CO2/H2 mixtures. Highly and stable Ru/γ-Al2O3 catalysts were prepared by high-temperature treatment reductive reaction gas. Operando/in situ spectroscopy STEM imaging reveals that strongly improved activity, factors 5 14 CO CO2 methanation, accompanied flattening Ru nanoparticles formation basic hydroxylated alumina sites....
ZSM-5 is a widely used zeolite catalyst and employed industrially for the methanol to gasoline (MTG) process. Even so, deactivation of by coke formation constitutes major technical also fundamental challenge. We investigate range catalysts through catalytic testing, physicochemical characterization, powder X-ray diffraction (XRD). It demonstrated that unit cell changes upon deactivation. Periodic density functional theory show change induced certain methyl substituted benzenes in channel...
Abstract As a commercial MTO catalyst, SAPO-34 zeolite exhibits excellent recyclability probably due to its intrinsic good hydrothermal stability. However, the structural dynamic changes of catalyst induced by hydrocarbon pool (HP) species and water formed during conversion as well long-term stability after continuous regenerations are rarely investigated poorly understood. Herein, framework were identified 1D 27 Al, 31 P MAS NMR, 2D P- Al HETCOR NMR spectroscopy. The breakage T-O-T bonds in...
The cationic molybdenum alkylidyne N-heterocyclic carbene (NHC) complex [Mo(C-p-OMeC6H4)(OCMe(CF3)2)2 (IMes)][B(ArF4] (IMes = 1,3-dimesitylimidazol-2-ylidene) was selectively immobilized inside the pores of ordered mesoporous silica (OMS) with pore diameters 66, 56, and 28 Å used in ring-expansion metathesis polymerization (REMP) cyclic olefins to yield polymers. A strong confinement effect observed for cis-cyclooctene (cCOE), 1,5-cyclooctadiene (COD),...
The synthesis of macrocycles is severely impeded by concomitant oligomer formation. Here, we present a biomimetic approach that utilizes spatial confinement to increase macrocyclization selectivity in the ring-closing metathesis various dienes at elevated substrate concentration up 25 mM using an olefin catalyst selectively immobilized inside ordered mesoporous silicas with defined pore diameters. By this approach, ratio between macro(mono)cyclization (MMC) product and all undesired...
Experimental evidence for the presence of tert-butyl cations, which are important intermediates in acid-catalyzed heterogeneous reactions, on solid acids has still not been provided to date. By combining density functional theory (DFT) calculations with (1)H/(13)C magic-angle-spinning NMR spectroscopy, cation was successfully identified zeolite H-ZSM-5 upon conversion isobutene by capturing this intermediate ammonia.
The catalytic cycle and activity of methanol-to-olefin conversion over low-silica AlPO-34 zeolites can be effectively altered by changing the Brønsted acid density.
The active site in ethene oligomerization catalyzed by Ni-zeolites is proposed to be a mobile Ni(II) complex, based on density functional theory-based molecular dynamics (DFT-MD) simulations corroborated continuous-flow experiments Ni-SSZ-24 zeolite. results of the at operating conditions show that molecules reversibly mobilize as they exchange with zeolite ligands Ni during reaction. Microkinetic modeling was conducted basis free-energy profiles derived DFT-MD for these...
1H and 27Al MAS NMR spectroscopies have been applied for studying the effect of water molecules, nitrogen bases, o-xylene on hydroxyl protons bridging AlOH groups framework aluminum atoms in metal−organic (MOF) MIL-53. For molecules adsorbed low-temperature form MIL-53lt, two signals were found indicating formation different O−H···O hydrogen bonds to neighboring oxygen atoms, such as carboxylic oxygens. Upon adsorption bases acetonitrile, ammonia, pyridine, a linear increase quadrupole...
Herein we investigated the activity of copper mordenites in methane-to-methanol conversion and material de- realumination. From four parent materials, a library was synthesized by liquid- solid-state ion-exchange techniques. Two key properties govern these materials methane conversion: counterion procedure. H-form parents result more active materials. The optimum stoichiometry between silicon, aluminum, leads to methanol productivity up 169 μmol/g. This equals 0.47 molecules formed per atom....
Abstract This contribution clarifies the overoxidation‐preventing key step in methane‐to‐methanol (MTM) conversion over copper mordenite zeolites. We followed zeolites by NMR spectroscopy supported DRIFTS to show that surface methoxy groups (SMGs) located at zeolite Brønsted sites are intermediates. The SMGs with chemical shift of 59 ppm identical those formed on a copper‐free reference after reaction methanol and react water, methanol, or carbon monoxide yield dimethyl ether, acetate....
Abstract The chitosan production process from fishery waste is already established in industrial scale, whereby fungal produced lower amounts. Since could be isolated under-valorized vegan streams while exhibiting slightly different characteristics, it has also potential for other applications. Within this publication, we focus on the Aspergillus niger . This study provides a detailed determination of biomass composition, adapting and comparing analytical tools, with special chitin content....
The acid site density and counter ion nature impact the proportion of alkene- aromatic-based MTO reaction cycles.
Abstract Phosphate‐modified ZSM‐5 zeolites were studied by standard characterization techniques and solid‐state nuclear magnetic resonance spectroscopy, in the methanol‐to‐olefin (MTO) conversion. Considering physicochemical properties of zeolites, most important effects phosphate modification are a deposition polyphosphates pore system decrease acid site density, but not strength. The significant increase selectivity to C 2 – 4 alkenes 5+ formation MTO reaction for coverage about 5 wt %...
The formation and evolution of initial reaction intermediates as well the mechanism during early period methanol conversion on silicoaluminophosphate SAPO-41 with one-dimensional 10-numbered ring pore system was elucidated. According to in situ UV–vis spectroscopy, nature formed catalysts process were monitored. remaining after quenching determined by ex UV–vis, 1H MAS NMR, 13C NMR reactivity these species investigated adsorption ammonia subsequent solid-state spectroscopy. above-mentioned...
Abstract Cu‐exchanged zeolites with the Ferrierite topology were investigated in direct CH 4 to 3 OH conversion. Samples a systematic compositional variation terms of Na/Al and Cu/Al ratios where synthesized by liquid ion exchange. The presence Na is observed be beneficial for Cu exchange thereby higher loadings achieved. overall performance Cu‐FER samples depends on loading as well conditions reaction. Elevated O 2 activation temperature long times are proven enhance yield sample Cu/Al=0.2....