Capture Of Trace Sulfur Gases From Binary Mixtures By Single-Walled Carbon Nanotube Arrays: A Molecular Simulation Study

With the growing energy consumption and the wide application of biogas technology, sulfur gases pollution is more and more serious, and the human living environment and health have suffered a great threat. Therefore, Many researchers have been paying more attention to the desulfurization technology. Carbon nanotubes as a typical porous carbon materials, has unique pore structure and large specific surface area, which has potential application in the purification of contaminated gases.Adsorption of H2S and SO2 pure gases and their selective capture from the H2S-CH4, H2S-CO2, SO2-N2 and SO2-CO2 binary mixtures by the single-walled carbon nanotubes (SWNTs) are investigated via using the grand canonical Monte Carlo (GCMC) method. It is found that the (20,20) SWNTs with larger diameter shows larger capacity for H2S and SO2 pure gases at T=303 K, in which the uptakes reach 16.31 and 16.03 mmol/g, respectively. However, the (6,6) SWNTs with small diameter exhibits the largest selectivity for binary mixtures containing trace sulfur gases at T= 303 K and P=100 kPa. By investigating the effect of pore size on the separation of gas mixtures, we found that the optimized pore size is 0.81 nm for separation of H2S-CH4, H2S-CO2 and SO2-N2 binary mixtures, while it is 1.09 nm for the SO2-CO2 mixture. The effects of concentration and temperature on the selectivity of sulfide are also studied at the optimal pore size. It is found that the concentration (ppm) of sulfur components has little effect on selectivity of SWNTs for these binary mixtures. However, the selectivity decreases obviously with the increase of temperature. Finally, to improve the adsorption capacities, we further modify the surface of SWNTs with the functional groups, and investigated the selectivities of sulfur gases on the modified SWNTs. It is found that the selectivities of H2S-CO2 and SO2-CO2 mixtures are basically uninfluenced by the site density, while the increase of site density can improve the selectivity of H2S-CH4 mixture doubly.