| The adsorption and separation properties of CH4 and H2S molecules in two metal-organic frameworks?MOFs?including Cu6?BTTC?4?H2O?6·xS?1?and[?CH3?2NH2]3[?Cu4Cl?3?BTTC?8]·yS?2?were studied using the grand canonical Monte Carlo?GCMC?simulation method with the optimized parameters obtained using the DREIDING force field.Effects of pressure,temperature of adsorbent on adsorption and separation were discussed.And analyzes the single component and mixture gas in the adsorbent adsorption curve,and Density Functional Theory?DFT?simulation were employed to study one component and mixture gas in the adsorbent adsorption curve.The main results are as follows:Firstly,The molecular simulation method systematically studied under 298 K and273 K,the two kinds of adsorbate on the adsorption of metal material performance and enthalpy of adsorption heat analysis.Results indicate that the adsorption capacity and separation performance of Complex 1 were higher than Complex 2,And to the same materials,the lower the temperature,the higher the adsorption heat;In the case of equimolar mixture,the selectivity of H2S/CH4 Complex 1 is the largest,and the difference of adsorption heat is Complex 1> Complex 2.Secondly,adsorption and separation behaviors of H2S and CH4 single component and H2S/CH4 binary mixture in Complex 1 and Complex 2 are investigated by GCMC combined with DFT simulations.The results showed that the adsorption energy of Complex 1 at low temperature and the energy density of CH4 was different at different temperatures.The adsorption energy of CH4 was higher than that of H2S;however in273 K,the adsorption energy of H2S has only one peak,with the increase of pressure,the peak value of H2S is higher than that of CH4,At the same pressure,the energy density of CH4 and H2S is slightly higher than that of 298 K at the temperature of 273 K.The adsorption of H2S/CH4 molar ratio of the mixed condition,there are competitive relations between them,by two when the low pressure adsorption into a high pressure when the adsorption,and the adsorption of CH4 gradually replaced by H2S.Finally,study on the mass density distribution of a single component and in H2S/CH4 binary mixture.The results showed that two main adsorption sites were found in the adsorption of CH4 on Complex 1 in 298 K,and the position of the metal cluster Cu-phenyl group region near the metal was the first adsorption site,and compared with the density map of H2S,at low pressure,H2S is also mainly adsorbed on the metal cluster Cu and phenyl group,with the increase of pressure,the A regionhas reached saturation state,and then all of the adsorption in the large pore?B region?;At 273 K,the difference of the mass density distribution of Complex 1 and Complex2 is obvious,and the adsorption in the A region is consistent with the previous one,and the mass distribution of H2S in the whole pressure range,the amount of adsorption gradually increased,the adsorption amount of CH4 remained unchanged.The results of the comprehensive analysis of the above,in the future,we should take into account these aspects of MOF materials in the actual adsorption and separation of H2S. |
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