Molecular sieves, with their uniform pore structure, large specific surface area, and tunable surface polarity, play a crucial role in gas and liquid purification, particularly in desulfurization technology. They not only efficiently adsorb polar hydrogen sulfide but can also be modified or structurally designed to remove sulfur dioxide and other organic sulfides. In desulfurization applications, depending on the target sulfide and process conditions, the following types of molecular sieves are mainly selected: 3A, 5A, and 13X molecular sieves.
Molecular sieves are used for the removal of hydrogen sulfide (H2S).
Molecular sieves are commonly used adsorbents for the deep removal of H2S in industry. Among them, 13X molecular sieves have the best H2S removal effect and are the most widely used; 5A molecular sieves can also be used to adsorb H2S, but their capacity and selectivity are slightly weaker than 13X zeolite.
Molecular sieves are polar aluminosilicate adsorbents with a uniform microporous structure. Their internal pore size allows small hydrogen sulfide molecules to enter, while the electrostatic attraction and van der Waals forces between surface cations and polar hydrogen sulfide molecules firmly adsorb the hydrogen sulfide molecules within the pores, thus removing hydrogen sulfide from the gas. After adsorption saturation, they can be regenerated by heating and purging, allowing for repeated use.
Molecular sieves are used to remove sulfur dioxide (SO2).
When the pore size of the molecular sieve is slightly larger than the diameter of SO₂ molecules, SO₂ molecules can diffuse into the pores, while gases larger than SO₂ molecules (such as some organic matter or large molecular sulfides) are blocked, achieving selective adsorption. The adsorption of sulfur dioxide by molecular sieves is generally greatly affected by moisture. Water molecules are more polar and have a smaller diameter, competing with sulfur dioxide for adsorption sites, leading to a significant decrease in desulfurization efficiency. Therefore, in industrial applications, pre-drying of flue gas or the use of hydrophobic molecular sieves to treat wet flue gas is often necessary.
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