Time filter

Source Type

Friedrich-Wilhelm-Lübke-Koog, Germany

Schuth F.,MPI fur Kohlenforschung
Physica Status Solidi (B) Basic Research | Year: 2013

The strong influence of the support properties on the activity of gold catalysts has been observed in many publications. The most studied reaction in this respect seems to be CO-oxidation, for which gold catalysts have outstanding activity. However, since in most studies the support properties are also important in influencing the nature of the gold particles deposited on them by co-precipitation or deposition-precipitation, it is difficult to study the support effect alone. We have in a series of studies used colloidal impregnation of preformed gold particles approximately 3nm in size on different supports in order to decouple the gold particle formation from the deposition process, in order to isolate the support effect. Even for such similarly prepared catalysts very strong differences between different supports were observed. The analysis of the data, also in the light of literature data, suggests that there is no unique factor explaining the high activity of gold catalysts, but rather a combination of effects, which act in different proportion for different catalysts. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Schuth F.,MPI fur Kohlenforschung
Angewandte Chemie - International Edition | Year: 2014

Down to the last detail: Nanostructured solid catalysts were already known in the early 20th century, but their exact structure was unclear. Nowadays, the arrangement of atoms and particles in solids can be manipulated and analyzed down to the atomic scale (see image). The use of specific highly active catalysts enables industrially relevant reactions to be performed at room temperature. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metzelthin A.,Ruhr University Bochum | Sanchez-Garcia E.,MPI fur Kohlenforschung | Sanchez-Garcia E.,Koc University | Birer A.O.,Ruhr University Bochum | And 4 more authors.
ChemPhysChem | Year: 2011

We have studied the aggregation process of (C 2H 2)⋯furan trimers at ultracold temperatures (0.37 K) in helium nanodroplets. Computational sampling of the potential energy surface using the multiple-minima-hypersurface (MMH) approach yielded seven possible minimum structures, optimized at the MP2 level of theory with the cc-pVTZ and 6-311++G(d,p) basis sets. Experimentally, we could assign five transitions in the IR spectrum of acetylene-furan aggregates in the acetylene C-H asym stretch region between 3240 and 3300 cm -1 to vibrational bands of the 2:1 acetylene-furan trimer. The transitions were assigned to three ring structures that all contain the T-shaped acetylene dimer as structural sub-motif. Two of the structures form a nonplanar ring involving a C-H Ac⋯π Fu bond, the third is a nearly planar ring containing a C-H Ac⋯O Fu bond. This assignment was corroborated by quantum mechanical/molecular dynamics (QM/MD) simulations mimicking in detail the aggregation process of precooled monomers. The simulations provided evidence for a transition from a higher level local minimum to the global minimum state over a small barrier during the aggregation process. The experimentally observed structures can be explained by a step-by-step aggregation of moieties pre-cooled to 0.37 K that are steered by intermediate and short-range electrostatic interactions. Thus, we are able to unravel a special aggregation mechanism which differs from aggregation of molecules with large dipole moments where this aggregation process is dominated by long range 1/r 3 dipole-dipole interaction ("electrostatic steering"). This mechanism is expected to be a general mechanism in ultracold chemistry. Brrrr-cold! The aggregation process of (C 2H 2)⋯furan trimers at ultracold temperatures (0.37 K) in helium nanodroplets is studied by a combination of computational and spectroscopic techniques. The results unravel a special aggregation mechanism for non- and weakly polar molecules, which is expected to be generally applicable in ultracold chemistry. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gu D.,Fudan University | Bongard H.,MPI fur Kohlenforschung | Deng Y.,Fudan University | Feng D.,Fudan University | And 6 more authors.
Advanced Materials | Year: 2010

Onionlike mesoporous carbon and carbonsilica nanocomposites with multilayer vesicle structures can be synthesized by an organic-inorganic co-assembly method under hydrothermal conditions in an aqueous emulsion solution (see figure). The nanocomposite vesicles have ordered lamellar mesostructures with about 3-9 layers and carbon pillars are located between the neighboring shells. (Chemical Equation Persentation). © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.

Schuth F.,MPI fur Kohlenforschung | Palkovits R.,MPI fur Kohlenforschung | Schlogl R.,Fritz Haber Institute | Su D.S.,Fritz Haber Institute
Energy and Environmental Science | Year: 2012

The possible role of ammonia in a future energy infrastructure is discussed. The review is focused on the catalytic decomposition of ammonia as a key step. Other aspects, such as the catalytic removal of ammonia from gasification product gas or direct ammonia fuel cells, are highlighted as well. The more general question of the integration of ammonia in an infrastructure is also covered. This journal is © 2012 The Royal Society of Chemistry.

Discover hidden collaborations