Acidic gases such as carbon dioxide(CO2),carbonyl sulfide(COS),hydrogen sulfide(H2S),methyl mercaptan(CH3SH),etc.in feed natural gas need to be removed through alkaline solvent treatment.During the absorption process,the removal rate of H2S through instantaneous proton mechanism reaction is much faster than that of COS and CO2.Therefore,although COS content is usually less abundant than H2S content in the feed gas,conventional techniques for removing H2S cannot completely and effectively remove COS.Because the chemical structure of COS is similar to that of CO2,but the absorption rate of CO2 is much higher than that of COS,it is difficult to retain part of CO2 and deeply remove COS.At Present,there is a lack of research on the differences between COS and CO2 absorption mechanisms,which leads to the lack of a theoretical basis for the design of COS selective absorption solvent under the coexistence of a large amount of CO2.Therefore,the absorption mechanism of COS needs to be further studied.The research progress on the mechanism of CO2 and COS absorption in organic amine solutions was summarized,and the following understandings are put forward.Firstly,in the aspect of mechanism research,it is generally believed that the absorption mechanism of COS in primary and secondary alkanolamines is the same as that of CO2 absorption.Secondly,the mechanism of CO2 absorption by alkanolamine is generally considered to be the removal of CO2 by the formation of carbaminate,and further thermal decomposition is the release of CO2 and the recycling of the absorption solution.Thirdly,both COS and CO2 are linear molecules with very similar physical and chemical properties,making it difficult to selectively absorb COS under the coexistence of COS and CO2.
carbonyl sulfidecarbon dioxidenatural gas purificationabsorption mechanismalkanolamine
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