Adsorption Characteristics And Dielectric Performances Of Zeolite Porous Materials Decorated By Insulating-Gas

In the privilege of superior arc-extinction and insulation performances,the SF₆gas has been comprehensively applied in high-voltage electrical transmission lines,in which the inevitable decomposition of SF₆ molecules in long-time operating switch-gears will degrade the insulation performance and even lead to dielectric failure.Employing zeolite porous material to uptake the insulating-gases of SF₆ and its decomposition products,it can not only to realize the recycle captures of the leakage SF₆ gas and the detection of SF₆ chemical decomposition,but also to inhibit electron avalanches for acquiring higher insulation performance.Whereas,the excessive greenhouse effect of SF₆ motivate the development of new insulating gas in substitute of SF₆ gas,so its research is also of far-reaching significance.In the present study,the first-principles calculations and molecular dynamics simulations are performed to investigate comparatively the adsorption characteristics of SF₆ decomposition gases and some new insulating gases being individually adsorbed on a diverse of zeolite porous materials diverse,especially analyzing the adsorbing selectivity for uptaking mixed gases.Accordingly,we study experimentally the dielectric performances of Na A/SF₆ adsorption system with the highest theoretical uptake and adsorption stability.Individually for the zeolite porous materials of MFI,Na ZSM-5 and Na A utilized as the adsorbents,Metropolis Monte Carlo method is employed to perform simulate the multiple-molecules adsorptions of SF₆ and new insulating gases,by which to calculate the adsorption configurations and adsorption isotherms at diverse temperatures.The adsorption binding energies of various adsorption configurations are accurately calculated through geometric optimizations of the first-principles energy-functional minimization.It is thus suggested that Na A has an excellent adsorption performance for SF₆,C₄F₇N,C₅F₁₀O and C₆F₁₂O molecules,while Na ZSM-5 represents a preferential adsorption of CF₃I with a substantial uptake.The self-diffusion coefficients of the adsorbed gas molecules are derived from the results of molecular dynamics simulations to evaluate the thermal stability of the adsorbed gases.In comparison to MFI and Na ZSM-5,the Na A porous structure represents a higher thermal stability of adsorbing insulating gases,as manifested by a lower thermal diffusion.Monte Carlo and molecular dynamics methods are combined to simulate the adsorption characteristics of MFI,Na ZSM-5 and Na A adsorbing gas molecules of SF₆decomposition products,specifically exploring their adsorbing selectivity to the mixed gas molecules.In comparison of the three zeolite porous materials,the calculated adsorption isotherm show the highest uptake of SF₆ decomposition gas by Na A adsorptions,while the highest adsorption energy arise in Na ZSM-5.The simulation results of adsorption selectivity,adsorption heat and adsorbate diffusion coefficient consistently show that Na A and Na ZSM-5 can effectively capture SO₂F₂ and SOF₂/SO₂ gases respectively,suggesting a prospective application to gas scavengers.In addition,the relatively highest adsorption heat of SF₆ decomposition gas can be acquired by Na ZSM-5,which means a hardest desorption.In particular for Na A/SF₆ adsorption,the calculation results of molecular simulations are verified by adsorption isothermal tests and infrared-spectrum molecular characterizations.The characteristic peaks in infrared absorption spectra identify a higher content of SF₆ molecules in Na A/SF₆ adsorption.Dielectric spectra tests and AC/DC electrical breakdown experiments demonstrate that the dielectric loss of Na A is significantly reduced by adsorbing SF₆ gas,and the breakdown field strength increases by 2.3-2.5 times.Therefore,after adsorbing SF₆,the nano-zeolite can be blended with dielectric polymers for preparing coating materials or nanocomposites with a higher dielectric performances to be applied in high-voltage insulation equipment.