Study Of Carbon Capture And Separation In Flue Gas By Antioxidant Solid Amine Adsorbent

In recent years,the massive consumption of fossil fuels has led to excessive emissions of carbon dioxide(CO2),causing various environmental problems.Therefore,reducing CO2 emissions is one of the major challenges of this century.Carbon capture and storage(CCUS)is one of the main ways to reduce CO2 emissions from large stationary sites,such as the electricity and industrial sectors.Solid amine adsorbents have the advantages of porous materials and organic amines,and can efficiently adsorb CO2.However,the flue gas contains 3-10 vol.%O2,which is easy to cause oxidative degradation of amino groups in the adsorbent.Therefore,tetraethylenepentamine-loaded molecular sieve(50%TEPA-MCM-41)was used as the research object,and it was functionalized by antioxidants.The oxidative degradation behavior of solid amine adsorbents,the antioxidant properties and antioxidant mechanism of amine functionalized adsorbents were systematically studied.(1)The adsorption performance and cycle stability of solid amine adsorbents loaded with 8%antioxidant 2-mercaptobenzimidazole(MB)in simulated flue gas containing oxygen were studied.The adsorption performance of 8%MB-50%TEPA-MCM-41 was twice that of 50%TEPA-MCM-41 after oxidation at 100℃ for 42 h in 95 vol.%N2/5 vol.%O2 atmosphere.In addition,under the condition of 5 vol.%O2/15 vol.%CO2/80 vol.%N2,after 30 cycles of adsorption tests,the adsorption capacity of 8%MB-50%TEPA-MCM-41 decreased by 6.45%,while that of 50%TEPA-MCM-41 decreased by 63.2%.This indicates that 8%MB-50%TEPA-MCM-41 has obvious antioxidant advantages.(2)The oxidative degradation mechanism of TEPA loaded MCM-41 adsorbent in simulated flue gas containing oxygen was studied.Through in-situ infrared spectroscopy analysis,it was found that with the increase of oxidation time,the peak intensity was positively correlated with the degree of amino oxidation,and the band C=O intensity increased sharply.The change of peak intensity from 1660 to 1680 cm-1 is consistent with the formation of amides,imines and carboxylic acids,which can interact with impregnated TEPA in the adsorbent through O2.The adsorption performance of solid amine adsorbent decreases under oxygen-containing flue gas.(3)The antioxidant degradation mechanism of antioxidant-loaded solid amine adsorbent under oxygen-containing simulated flue gas was studied.The antioxidant 2-mercaptobenzimidazole(MB)scavenges the free radicals generated by amino oxidation and decomposes the hydroperoxides generated by the free radical reaction.The hydroperoxides are decomposed into alcohols(non-radical products),which are eventually oxidized to sulfonic acid compounds,reducing the oxidation rate of the adsorbent.The modification of MB solved the problem of oxidative degradation and pointed out the direction for the preparation of antioxidant efficient adsorbents.