scholarly journals Comparing ammonia diffusion in NH3-SCR zeolite catalysts: a quasielastic neutron scattering and molecular dynamics simulation study

2018 ◽  
Vol 20 (17) ◽  
pp. 11976-11986 ◽  
Author(s):  
A. J. O'Malley ◽  
M. Sarwar ◽  
J. Armstrong ◽  
C. R. A. Catlow ◽  
I. P. Silverwood ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Neutron Scattering ◽  
Zeolite Catalysts ◽  
Dynamics Simulation ◽  
Simulation Studies ◽  
Nh3 Scr ◽  
Small Pore ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering

Neutron scattering and simulation studies reveal important consistencies and differences in ammonia mobility in small pore NH3-SCR zeolite catalysts.

scholarly journals Methanol diffusion in zeolite HY: a combined quasielastic neutron scattering and molecular dynamics simulation study

2016 ◽  
Vol 18 (26) ◽  
pp. 17294-17302 ◽  
Author(s):  
Alexander J. O'Malley ◽  
Victoria García Sakai ◽  
Ian P. Silverwood ◽  
Nikolaos Dimitratos ◽  
Stewart F. Parker ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Neutron Scattering ◽  
Simulation Study ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering

The diffusion of methanol in zeolite HY is studied using tandem quasielastic neutron scattering (QENS) experiments and molecular dynamics (MD) simulations at 300–400 K.

scholarly journals Molecular behaviour of phenol in zeolite Beta catalysts as a function of acid site presence: a quasielastic neutron scattering and molecular dynamics simulation study

2019 ◽  
Vol 9 (23) ◽  
pp. 6700-6713 ◽  
Author(s):  
Carlos Hernandez-Tamargo ◽  
Alexander O'Malley ◽  
Ian P. Silverwood ◽  
Nora H. de Leeuw
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Simulation Study ◽  
Acid Site ◽  
Dynamic Behaviour ◽  
Acid Sites ◽  
Zeolite Beta ◽  
Dynamics Simulation ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering

The dynamic behaviour of phenol in zeolite Beta is strongly influenced by the presence of Brønsted acid sites.

Self Diffusion in Liquid Titanium: Quasielastic Neutron Scattering and Molecular Dynamics Simulation

2009 ◽  
Vol 289-292 ◽  
pp. 609-614 ◽  
Author(s):  
Andreas Meyer ◽  
Jürgen Horbach ◽  
O. Heinen ◽  
Dirk Holland-Moritz ◽  
T. Unruh
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Neutron Scattering ◽  
The Self ◽  
Dynamics Simulation ◽  
Self Diffusion ◽  
Quasielastic Neutron ◽  
Liquid Titanium ◽  
Quasielastic Neutron Scattering ◽  
Self Diffusion Coefficient

Self diffusion in liquid titanium was measured at 2000K by quasielastic neutron scattering (QNS) in combination with container less processing via electromagnetic levitation. At small wavenumbers q the quasielastic signal is dominated by incoherent scattering. Up to about 1.2 °A−1 the width of the quasielastic line exhibits a q2 dependence as expected for long range atomic transport, thus allowing to measure the self diffusion coefficient DTi. As a result the value DTi = (5.3± 0.2)× 10−9 m2s−1 was obtained.With a molecular dynamics (MD) computer simulation using an embedded atom model (EAM) for Ti, the self diffusion coefficient is determined from the mean square displacement as well as from the decay of the incoherent intermediate scattering function at different q. By comparing both methods, we show that the hydrodynamic prediction of a q2 dependence indeed extends up to about 1.2 °A−1. Since this result does not depend significantly on the details of the interatomic potential, our findings show that accurate values of self diffusion coefficients in liquid metals can be measured by QNS on an absolute scale.

Ammonia mobility in chabazite: insight into the diffusion component of the NH3-SCR process

2016 ◽  
Vol 18 (26) ◽  
pp. 17159-17168 ◽  
Author(s):  
Alexander J. O'Malley ◽  
Iain Hitchcock ◽  
Misbah Sarwar ◽  
Ian P. Silverwood ◽  
Sheena Hindocha ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Zeolite Catalysts ◽  
Scr Catalyst ◽  
Nh3 Scr ◽  
Diffusion Component ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering ◽  
Dynamics Simulations ◽  
Insight Into ◽  
Automotive Emission

To assess the effect of counterion presence on NH3 mobility in commercial automotive emission control zeolite catalysts, NH3 mobility in NH3-SCR catalyst Cu-CHA was compared with H-CHA using quasielastic neutron scattering and molecular dynamics simulations.

Water Mobility in Reverse Micelles Studied by Quasielastic Neutron Scattering and Molecular Dynamics Simulation

2005 ◽  
Vol 899 ◽  
Author(s):  
Branka Ladanyi ◽  
Nancy Levinger
Keyword(s):  
Molecular Dynamics ◽  
Neutron Scattering ◽  
Reverse Micelles ◽  
Continuous Phase ◽  
Dynamics Simulation ◽  
Rotational Relaxation ◽  
Interfacial Region ◽  
Water Mobility ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering

AbstractReverse micelles (RMs) are aggregates in which nanoscale droplets of a polar liquid, usually water, are surrounded by a surfactant layer in a nonpolar continuous phase. They are widely used as media for reactions in which the extent of confinement or the presence of a surfactant interface play a central role. We have used molecular dynamics (MD) computer simulation and quasielastic neutron scattering (QENS) and to investigate the mobility of water molecules in reverse micelles. The contribution of water to the QENS signal is enhanced by deuterating the surfactant and the nonpolar phase. Our studies of water mobility have focused on the effects of water pool size, determined by the water/surfactant mole ratios w0, as well as on the properties of the water-surfactant interface. Specifically, we have examined the effects of varying w0 and of substituting other alkali ions for the usual Na+ counterion of the anionic surfactant AOT (bis (2-ethylhexyl) sulfosuccinate)). We find good agreement between the QENS signal and its prediction from MD simulation. This allows us to obtain additional insight into water mobility by analyzing the MD self-intermediate scattering function (ISF) of water hydrogens in terms of contributions from molecular rotation and translation and from molecules in different interfacial layers. MD data indicate that the translational ISF decays nonexponentially due to lower water mobility close to the interface and to confinement-induced restrictions on the range of translational displacements. Rotational relaxation also exhibits nonexponential decay. However, rotational mobility of O-H bond vectors in the interfacial region remains fairly high due to the lower density of water-water hydrogen bonds in the vicinity of the interface.

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