Equilibrium and hysteresis formation of water vapor adsorption on microporous adsorbents: Effect of adsorbent properties and temperature

Differential Analysis of Various Moisture Phases on N2 Displacement of CH4 in Coal

The aim of the study was to elucidate the impact of different moisture phases during gas injection on coalbed methane displacement. The coal samples were treated with two methods: water vapor adsorption and liquid water stirring. The differences in the coal samples treated with various moisture phases during gas injection for coalbed methane displacement were investigated by using the isothermal adsorption curves of CH4, N2, and H2O in coal and N2 displacement of CH4 in coal. The results indicate that variations in the gas adsorption capacity of coal are treated with different moisture phases. The gas adsorption capacities and displacement capacities of the coal samples treated with the water vapor adsorption methods are better than those treated with the stirring methods. In the isothermal adsorption experiment, for the coal samples treated with different moisture phases, at a moisture content of 2.75%, the saturated adsorption capacities of CH4/N2 are 0.204/0.189 (cm3/g), and at a moisture content of 5.63%, the saturated adsorption capacities of CH4/N2 are 0.151/0.139 (cm3/g). In addition, in the displacement experiment, for the coal samples treated with different moisture phases, at a moisture content of 2.75%, the difference in the total gas adsorption capacities is 0.62 cm3/g and the difference in the CH4 adsorption capacities is 0.473 cm3/g, and at a moisture content of 5.63%, the difference in the total gas adsorption capacities is 0.3 cm3/g and the difference in CH4 adsorption capacities is 0.22 cm3/g. For the coal samples treated with various moisture phases, the differences in the CH4/N2 adsorption and displacement capacities are greater at a moisture content of 2.75% than at 5.63%. Notably, the moisture phase has only a marginal influence on the CH4 desorption capacity and desorption rate. The study is important to understand the interactions between coal and moisture.

Adsorption characteristics of dichloromethane-ethyl acetate/toluene vapor on a hypercrosslinked polystyrene adsorbent

Dichloromethane (DCM), a typical representative of chlorinated volatile organic compounds (CVOCs), is usually exhausted along with other volatile organic compounds (VOCs), such as toluene and ethyl acetate, in industrial factories. To address the complexity of the components, the large variation in concentration of each component and the water content of the exhaust gases emitted from the pharmaceutical and chemical industries, the adsorption characteristics of DCM, toluene (MB), and ethyl acetate (EAC) vapors on hypercrosslinked polymeric resins (NDA-88) were studied by dynamic adsorption experiments. Furthermore, the adsorption characteristics of NDA-88 for binary vapor systems of DCM-MB and DCM-EAC at different concentration ratios and the nature of the interaction force with the three VOCs were explored. NDA-88 was found to be suitable for treating binary vapor systems of DCM mixed with low concentrations of MB/EAC, and a small quantity of adsorbed MB or EAC would promote the adsorption of DCM by NDA-88, which is attributed to the microporous filling phenomenon. Finally, the influence of humidity on the adsorption performance of binary vapor systems for NDA-88 and the regeneration adsorption performance of NDA-88 were investigated. The presence of water steam shortened the penetration times of DCM, EAC, and MB, regardless of whether it was in the DCM-EAC or DCM-MB two-component systems. This study has identified a commercially available hypercrosslinked polymeric resin NDA-88, which has excellent adsorption performance and regeneration capacity for both single-component DCM gas and a binary mixture of DCM-low-concentration MB/EAC, providing experimental guidance for the treatment of emissions from pharmaceutical and chemical industries by adsorption.