A5090635712- Zeolite Catalysis and Synthesis
- Advanced NMR Techniques and Applications
- Chemical Synthesis and Characterization
- Solid-state spectroscopy and crystallography
- Mesoporous Materials and Catalysis
- NMR spectroscopy and applications
- Crystal Structures and Properties
- Metal-Organic Frameworks: Synthesis and Applications
- Catalytic Processes in Materials Science
- Inorganic Fluorides and Related Compounds
- Glass properties and applications
- Advanced Battery Materials and Technologies
- Analytical Chemistry and Chromatography
- Radioactive element chemistry and processing
- Luminescence Properties of Advanced Materials
- Nanoporous metals and alloys
- Catalysis and Oxidation Reactions
- Muon and positron interactions and applications
- Ionic liquids properties and applications
- Marriage and Sexual Relationships
- Covalent Organic Framework Applications
- Molecular spectroscopy and chirality
- Analytical chemistry methods development
- Clay minerals and soil interactions
- Building materials and conservation
University of Münster
2015-2025
Wiener Krankenanstaltenverbund
2021
FH Münster
2009
Monash University
2006
CSIRO Manufacturing
2006
Royal Institution of Great Britain
2005
Instituto de Tecnología Química
1999-2001
Universitat Politècnica de València
2000-2001
University of Delaware
1999-2000
Hanyang University
2000
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXT23Na NMR Spectroscopy of Solids: Interpretation Quadrupole Interaction Parameters and Chemical ShiftsHubert Koller, Guenter Engelhardt, Arno P. M. Kentgens, Joachim SauerCite this: J. Phys. Chem. 1994, 98, 6, 1544–1551Publication Date (Print):February 1, 1994Publication History Published online1 May 2002Published inissue 1 February 1994https://pubs.acs.org/doi/10.1021/j100057a004https://doi.org/10.1021/j100057a004research-articleACS...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSiO-.cntdot. .cntdot. .cntdot.HOSi Hydrogen Bonds in As-Synthesized High-Silica ZeolitesHubert Koller, Raul F. Lobo, Sandra L. Burkett, and Mark E. DavisCite this: J. Phys. Chem. 1995, 99, 33, 12588–12596Publication Date (Print):August 1, 1995Publication History Published online1 May 2002Published inissue 1 August 1995https://pubs.acs.org/doi/10.1021/j100033a036https://doi.org/10.1021/j100033a036research-articleACS PublicationsRequest reuse...
Pentacoordinated silicon units, SiO4/2F-, were found by solid-state NMR experiments in various as-made high-silica zeolites (Beta, SSZ-23, ITQ-3, ITQ-4, ZSM-12, Silicalite-1) that are prepared the presence of fluoride ions as mineralizing agents. The SiO4/2F- units part framework, being connected, through sharing four O atoms, with neighboring tetracoordinated SiO4/2 units. These five-coordinate balance charge cationic organic structure-directing agent. 29Si chemical shift these sites is...
The effect of outer-sphere environment on alkene epoxidation catalysis using an organic hydroperoxide oxidant is demonstrated for calix[4]arene-TiIV single-sites grafted amorphous vs crystalline delaminated zeotype (UCB-4) silicates as supports. A chelating calix[4]arene macrocyclic ligand helps enforce a constant TiIV inner-sphere, characterized by UV-visible and X-ray absorption spectroscopies, thus enabling the rigorous comparison environments across different siliceous These are...
Hydrogen-bonded SiOH defects and Brønsted acidic bridging OH groups, defined as acid sites (BAS), yield overlapping signals in 1H MAS NMR FTIR spectroscopies. Here, a clear distinction the distribution of defect between industrial ZSM-5 zeolites with Si/Al ratios 14 20 well 60 is reported. At high = ratio, hydrogen-bonded groups appear spectrum H-ZSM-5 3 8 pm, thus severely caused by unperturbed BAS. spectra are similarly affected. The paired, they clearly identified double-quantum...
The new synthetic form of microporous crystalline silica, denoted as ITQ-12, shows a high potential for the separation propane and propene from its mixtures.
Multiple-quantum 1H MAS NMR spectroscopy has been used to study defect sites in siliceous as-made ZSM-12 zeolite synthesized with perdeuterated benzyltrimethylammonium cations. The results of two-dimensional double-quantum and triple-quantum experiments show that three silanol (SiOH) protons the site engage hydrogen bonding charge-compensating siloxy (SiO-) group. Simulations sideband pattern were determine an average dipolar coupling between 4.0 (±0.5) kHz (an equilateral triangular...
Two pairs of Brønsted acid sites have been identified in H,Na-Y zeolite, located the supercage and sodalite cage, which upon ultrastabilization (dealumination) are transformed into Lewis sites. This mild postsynthetic modification step is an important process for converting this material active catalyst large-scale commercial reactions. Pairing structures their transformations investigated using 1 H double-quantum NMR spectroscopy experiments dehydrated H,Na-Y, its ultrastabilized form,...
Brønsted acid sites (BAS) in dry aluminosilicate zeolites, also known as bridging OH–H groups, may form hydrogen bonds with other framework oxygen atoms, O, addition to BAS that are free of such interactions. These referred perturbed and unperturbed BAS, respectively. However, bonding occur only for specific geometric orientations between two allowing an OH–H···O interaction. To evaluate the possibility bonding, we introduce alignment angle κ describes Si–OH–Al bisector OH–O direction a...
Nests of three silanol groups are located on the internal pore surface calcined zeolite SSZ-70. 2D 1 H double/triple-quantum single-quantum correlation NMR experiments enable a rigorous identification these triad nests. They reveal close proximity to structure directing agent (SDA), that is, N,N'-diisobutyl imidazolium cations, in as-synthesized material, which defects negatively charged (silanol dyad plus one SiO- siloxy group) for charge balance. It is inferred ring strain prevents...
The coordination of boron atoms and their association with counterions in dehydrated zeolites B-ZSM-5, B-Beta, B-SSZ-24 have been studied by solid state NMR methods. 11B MAS spectra show that occurs both trigonal (B[3]) tetrahedral (B[4]) the zeolite framework. isotropic chemical shift (δcs) allows one to distinguish between extra-framework species (δcs=18–19 ppm), Bnf[3], framework (δcs=9.8–10.7 Bf[3]. Extra-framework can be avoided if are completely care. Large such as sodium, lithium...
With fluoride as a mineralizing agent, the high-silica zeolites nonasil and ZSM-5 were obtained by hydrothermal syntheses. 29Si NMR spectroscopy showed that five-coordinate silicon exists in form of SiO4/2F− zeolite frameworks (see 29Si{19F} CPMAS spectrum on right). In at room temperature ion undergoes dynamic exchange between different atoms, which is frozen out 140 K.
Internal defect SiOH and SiO- groups evolve during the structure formation of high-Si zeolites in presence a cationic organic structure-directing agent (SDA). These negatively charged defects do not completely disappear upon calcination. Herein we investigate clustering their location within pore walls four zeolites. ZSM-12, ZSM-5, SSZ-74 have three clustered which are hydrogen-bonded to , whereas SSZ-24 has only two. interact with quaternary ammonium ions preferably close charge center,...
Gold and silver metal salts were reduced in the presence of phenylethylthiol as capping agent to form nanoparticles 2.1–2.4 nm diameter. These clusters then added a sol–gel process using phenyltriethoxysilane hybrid component optimize dispersion particles matrix. The encapsulated grow an average diameter 6 nm. This method permits controlled variation materials' porosity by simply regulating synthesis pH values. Optimized mixed micro-/mesoporous materials are obtained at = 6. matrix thermally...