scholarly journals The inhibition effect of water on the purification of natural gas with nanoporous graphene membranes

2018 ◽  
Vol 9 ◽  
pp. 1906-1916 ◽  
Author(s):  
Krzysztof Nieszporek ◽  
Tomasz Pańczyk ◽  
Jolanta Nieszporek
Keyword(s):  
Natural Gas ◽  
Hydrogen Bonds ◽  
Membrane Separation ◽  
Extreme Case ◽  
Gas Permeation ◽  
Effect Of Water ◽  
Nanoporous Graphene ◽  
Analysis Of Stability ◽  
Dynamics Simulations ◽  
Kinetics Of

Molecular dynamics simulations are used to investigate the inhibiting effect of water on the natural gas separation with nanoporous graphene. The membrane separation process involves CH4 + N2 mixtures with and without the addition of water. The results show that water is able to form hydrogen bonds with nitrogen atoms located in a nanopore rim. This effect causes a decrease of separation selectivity as well as a reduction of gas permeation. In the extreme case, when the nanopore rim contains only nitrogen atoms, water agglomerates at the center of the nanopore and effectively closes down the permeation path. The conclusions are confirmed by the analysis of stability and kinetics of hydrogen bonds.

scholarly journals The Impact of Various Natural Gas Contaminant Exposures on CO2/CH4 Separation by a Polyimide Membrane

Membranes ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 324
Author(s):  
Nándor Nemestóthy ◽  
Péter Bakonyi ◽  
Piroska Lajtai-Szabó ◽  
Katalin Bélafi-Bakó
Keyword(s):  
Natural Gas ◽  
Membrane Separation ◽  
Gas Permeation ◽  
Natural Gases ◽  
Gas Processing ◽  
Polyimide Membrane ◽  
Naturally Occurring ◽  
Benzene Toluene ◽  
And Performance ◽  
The Impact

In this study, hollow fibers of commercial polyimide were arranged into membrane modules to test their capacity and performance towards natural gas processing. Particularly, the membranes were characterized for CO2/CH4 separation with and without exposure to some naturally occurring contaminants of natural gases, namely hydrogen sulfide, dodecane, and the mixture of aromatic hydrocarbons (benzene, toluene, xylene), referred to as BTX. Gas permeation experiments were conducted to assess the changes in the permeability of CO2 and CH4 and related separation selectivity. Compared to the properties determined for the pristine polyimide membranes, all the above pollutants (depending on their concentrations and the ensured contact time with the membrane) affected the permeability of gases, while the impact of various exposures on CO2/CH4 selectivity seemed to be complex and case-specific. Overall, it was found that the minor impurities in the natural gas could have a notable influence and should therefore be considered from an operational stability viewpoint of the membrane separation process.

Effect of Water Vapor on the Kinetics of Combustion of Hydrogen and Natural Gas: Experimental and Detailed Modeling Study

2008 ◽  
Author(s):  
Tanh Le Cong ◽  
Philippe Dagaut
Keyword(s):  
Water Vapor ◽  
Natural Gas ◽  
Gas Turbines ◽  
Kinetic Scheme ◽  
Fused Silica ◽  
Pollutant Emissions ◽  
Kinetic Reaction ◽  
Effect Of Water ◽  
Oxidation Of Hydrogen ◽  
Kinetics Of

The dilution of fuels by exhausts gases (mainly CO, CO2 and H2O) affects the kinetics of combustion. This dilution is used in gas turbines and flameless combustor. It helps reducing pollutant emissions, particularly NOx. Therefore, it is useful to study the effect of such compounds on the kinetics of oxidation of fuels such as natural gas and hydrogen. The oxidation of hydrogen and that of methane were studied experimentally in a fused silica jet-stirred reactor (JSR) over the temperature range 800–1500 K, from fuel-lean to fuel-rich conditions. The experiments were repeated in presence of 10% in mole of water vapor. A detailed chemical kinetic modeling of the present experiments and of literature data (flame speed, ignition delays) was performed using a previously proposed kinetic reaction mechanism, showing good agreement between the data and this modeling. Sensitivity and reaction paths analyses were used to delineate the important reactions influencing the kinetic of oxidation of the fuels in presence of water vapor. The kinetic reaction scheme proposed helps understanding the inhibiting effect of water vapor on the oxidation of hydrogen and methane. The effect of water vapor on NOx formation under gas turbine conditions was also investigated numerically using the proposed kinetic scheme.

Application of the ceramic membrane with hydrophobic skin layer to separation of activated sludge

1997 ◽  
Vol 35 (8) ◽  
pp. 137-144 ◽  
Author(s):  
Tsuyoshi Nomura ◽  
Takao Fujii ◽  
Motoyuki Suzuki
Keyword(s):  
Activated Sludge ◽  
Pore Size ◽  
Ceramic Membrane ◽  
Membrane Separation ◽  
Porous Ceramic ◽  
Porous Membrane ◽  
Skin Layer ◽  
Gas Permeation ◽  
Wide Range ◽  
Cake Layer

Porous membrane of poly(tetrafluoroethylene) (PTFE) was formed on the surface of porous ceramic tubes by means of heat treatment of the PTFE particles deposit layer prepared by filtering PTFE microparticles emulsified in aqueous phase. By means of inert gas permeation, pore size was determined and compared with scanning electron micrograph observation. Also rejection measurement of aqueous dextran solutions of wide range of molecular weights showed consistent results regarding the pore size. Since the membrane prepared by this method is stable and has unique features derived from PTFE, it is expected that the membrane has interesting applications in the field of water treatment. Membrane separation of activated sludge by this composite membrane and original ceramics membrane showed that the PTFE membrane gives better detachability of the cake layer formed on the membrane. This might be due to the hydrophobic nature of the PTFE skin layer.

scholarly journals Morphology, energetics and growth kinetics of diphenylalanine fibres

2021 ◽  
Author(s):  
Phillip Mark Rodger ◽  
Caroline Montgomery ◽  
Giovanni Costantini ◽  
Alison Rodger
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Growth Kinetics ◽  
Dynamics Simulations ◽  
Kinetics Of

The formation and stability of diphenylalanine fibres are studied by combining molecular dynamics simulations with microscopy and spectroscopy experiments, quantitatively detailing their morphology, energetics and growth kinetics.

WHICH IS THE PROTON-SHUTTLE IN ISOXANTHOPTERIN DEAMINASE? QM/MM MD UNDERSTANDING

2013 ◽  
Vol 12 (08) ◽  
pp. 1341002 ◽  
Author(s):  
XIN ZHANG ◽  
MING LEI
Keyword(s):  
Crystal Structure ◽  
Molecular Dynamics ◽  
Hydrogen Bonds ◽  
Proton Transfer ◽  
Glutamic Acid ◽  
Active Site ◽  
Nucleophilic Attack ◽  
Zinc Ions ◽  
Initial Model ◽  
Dynamics Simulations

The deamination process of isoxanthopterin catalyzed by isoxanthopterin deaminase was determined using the combined QM(PM3)/MM molecular dynamics simulations. In this paper, the updated PM3 parameters were employed for zinc ions and the initial model was built up based on the crystal structure. Proton transfer and following steps have been investigated in two paths: Asp336 and His285 serve as the proton shuttle, respectively. Our simulations showed that His285 is more effective than Aap336 in proton transfer for deamination of isoxanthopterin. As hydrogen bonds between the substrate and surrounding residues play a key role in nucleophilic attack, we suggested mutating Thr195 to glutamic acid, which could enhance the hydrogen bonds and help isoxanthopterin get close to the active site. The simulations which change the substrate to pterin 6-carboxylate also performed for comparison. Our results provide reference for understanding of the mechanism of deaminase and for enhancing the deamination rate of isoxanthopterin deaminase.

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