Acid Gas Removal by Superhigh Silica ZSM-5: Adsorption Isotherms of Hydrogen Sulfide, Carbon Dioxide, Methane, and Nitrogen

Abstract

The adsorption of acid gas, including hydrogen sulfide and carbon dioxide, by superhigh silica ZSM-5 was investigated. Equilibrium adsorption isotherms of high-purity hydrogen sulfide and carbon dioxide were measured experimentally using this new sorbent. In addition, methane and nitrogen adsorption isotherms on this MFI-type zeolite were also measured as representative of other natural gas components. To enhance the reliability of the results, the adsorption pressure has been selected up to 20 bar at three different temperatures. Superhigh silica ZSM-5 for the adsorption of hydrogen sulfide shows an impressive result of 3.04 mmol•g −1 at 12 bar and 283 K. This value was 2.69 mmol•g −1 for carbon dioxide at 21 bar and 283 K. The adsorption capacity of H 2 S on the ZSM-5 is the highest, and N 2 is the lowest; the order of the adsorption capacities of components is H 2 S > CO 2 > CH 4 > N 2 . The adsorption heat of different adsorbates is calculated: 13.7 and 29.5 kJ•mol −1 for H 2 S and CO 2 , respectively. Physical adsorption has occurred on high-silica ZSM-5, especially for hydrogen sulfide, and this is a great advantage. By increasing the temperature, the adsorption capacity of components on the ZSM-5 decreases, but due to differences in the adsorption heat of the adsorbate, the ideal selectivity for hydrogen sulfide increases. There is a challenge in the choice of the best condition for H 2 S removal, as, by increasing the temperature, the adsorption capacity of hydrogen sulfide reduces, but the selectivity of the hydrogen sulfide increases as compared to other gases. This phenomenon is not true for the selectivity of other components.

Unravelling the kinetics, isotherms, thermodynamics, and mass transfer behaviours of Zeolite Socony Mobil - 5 in removing hydrogen sulphide resulting from a dark fermentative biohydrogen production process

“…21,22 Therefore, MFI is one of the best options to remove H 2 S. Zeolite Socony Mobil -5 (ZSM-5) is a crystalline substance, which belongs to the MFI category that has a porous structure, and has been reported to be commonly employed to trap molecules. 23 Zeolites are known to be molecular sieves since they have high porosity. 24 In both gaseous and aqueous settings, ZSM-5 has the ability to adsorb and eliminate hydrogen sulphide (H 2 S).…”

CH4/N2Adsorptive Separation by a ZSM-5 Zeolite Packed Multicolumn VPSA Process with the SMB Operation Mode for High-Purity Methane Production

“…In the actual situation, the mixed gases entering the adsorption separation step will contain a certain amount of water vapor. Hydrophobic sorbents, such as high-silicon zeolites, have been investigated in detail. − Rahmani et al measured the equilibrium adsorption isotherms of acid gases (H 2 S, CO 2 , CH 4 , and N 2 ) on superhigh-silica ZSM-5 zeolite with Si/Al = 3000. Li’s group tested the homemade zeolite silicalite-1 to separate CH 4 and N 2 by the PSA process and confirmed that the effect of water vapor could be negligible.…”