Strain-controlled graphdiyne membrane for CO2/CH4 separation:First-principle and molecular dynamic simulation

Tensile strain of porous membrane materials can broaden their capacity in gas separation.In this work,using van der Waals corrected density functional theory(DFT)and molecular dynamics(MD)simulations,the performance and mechanism of CO2/CH4 separation through strain-oriented graphdiyne(GDY)monolayer were studied by applying lateral strain.It is demonstrated that the CO2 permeance peaks at 1.29×10^6 gas permeation units(GPU)accompanied with CO2/CH4 selectivity of 5.27×10^3 under ultimate strain,both of which are far beyond the Robeson’s limit.Furthermore,the GDY membrane exhibited a decreasing gas diffusion energy barrier and increasing permeance with the increase of applied tensile strain.CO2 molecule tends to reoriented itself vertically to permeate the membrane.Finally,the CO2 permeability decreases with the increase of the temperature from300 K to 500 K due to conserving of rotational freedom,suggesting an abnormal permeance of CO2 in relation to temperature.Our theoretical results suggest that the stretchable GDY monolayer holds great promise to be an excellent candidate for CO2/CH4 separation,owing to its extremely high selectivity and permeability of CO2.

High efficient development of green kinetic hydrate inhibitors via combined molecular dynamic simulation and experimental test approach

The development of environmental friendly low dose hydrate inhibitors like kinetic hydrate inhibitors(KHIs)is of great significance for the flow assurance in oil&gas production and transportation.In this work,a combined molecular dynamic simulation and experimental verification approach was adopted to increase the efficiency of KHIs development.The inhibition effect of a series of copolymers(N-vinylpyrrolidone and N-acrylate)on hydrate growth was studied by using both molecular dynamics simulation and experimental approaches.The simulation results demonstrated that introduction of hydrophobic ester and butyl group in PVP is beneficial for the inhibition.The length of the alkyl chain of ester group played an important role in improving inhibition performance.PVP-A,the one being introduced butyl ester group into PVP gets the best inhibition effect.In addition,inhibitors can restrict methane bubbles to re-dissolve into the liquid phase,thereby inhibiting the growth of methane hydrate.Increasing the interaction between KHIs and methane can also improve the inhibitory effect of KHIs.The experimental results confirm the reliability of the molecular dynamics simulation.