Study On Adsorption Desulfurization Behavier And Mechanism Of Zeolite For COS And H₂S In Coke Oven Gas

The sulfur content in coke oven gas（COG）needs to be controlled at a low level due to environmental standards and sustainable development requirements.Therefore,deep purification of COS and H₂S in COG is required.Among the current desulfurization technologies,zeolite desulfurization has many advantages such as high sulfur capacity,simple operation,low cost,and excellent recyclable regeneration.MFI and FAU zeolites were used in this thesis for studying desulfurization performance of COS and H₂S in COG.The effects of the skeleton structure properties,acid-base properties,and pore structure properties of the zeolite on the desulfurization performance were studied by N₂-adsorption,NH₃-TPD,CO₂-TPD,FTIR,py-FTIR.The adsorption mechanism of COS and H₂S on the surface of the zeolite and the competitive adsorption between H₂O and H₂S were studied by in-situ infrared experiments.The conclusions are as follows:（1）When dealing with high concentrations of COS and H₂S,the desulfurization activity of FAU-type zeolite is significantly higher than that of MFI-type zeolite;and the adsorption capacity of zeolite for H₂S is significantly higher than that of COS.It can be seen that the larger special surface area and the high micropore ratio of the zeolite are beneficial to the adsorption of COS and H₂S.The weak basicity site on the surface of the zeolite is the adsorption active site of COS and H₂S.The weak basicity site on the zeolite surface is the adsorption active site of COS and H₂S.FTIR analysis shows that the distribution of the weak basicity site is related to the distribution of the hydroxyl groups on the surface of the zeolite,and the stronger the polarity of the adsorbent,the better its adsorption ability.（2）In the presence of steam,the desulfurization activity of FAU zeolite is reduced dramatically,but its breakthrough sulfur capacity is still higher than that of MFI zeolite.The impact of steam on H₂S is much stronger than COS due to the similar zeolite of H₂O and H₂S.From the results of ICP and NH₃-TPD,it is found that the difference in the hydrophobicity of zeolite is related to its Si/Al atomic ratio.The higher the Si/Al atomic ratio,the stronger acidic sites on zeolite surface.The weaker polarity of zeolite,the stronger of its hydrophobicity.The desulfurization performance is reduced with the increase of Si/Al atomic ratio.The F_II zeolite has good desulfurization performance in four different atmospheres.（3）When studying the adsorption mechanism of COS and H₂S on the surface of the zeolite,it is found that there are two types of adsorption mechanisms on the surface of zeolite:The first type is the dissociation of COS or H₂S with the hydroxyl groups on zeolite surface,and the main adsorption site is the surface bridging hydroxyl（Si-OH-Al）and silicic hydroxyl（Si-OH）.The second type is the M-S interaction between the S atom and the metal cation on the zeolite by breaking the C-S bond or H-S bond.The first type of adsorption mechanism is dominant.（4）When steam exists in coke oven gas,the hydroxyl groups on the zeolite preferentially adsorb H₂O due to the strong polarity,which prevents H₂S interacting with hydroxyl groups.Therefore H₂S is adsorbed on the surface of the zeolite mainly in M-S mode,and the sulfur capacity of the zeolite is reduced.