Adsorption Performance Of Porous Materials Modified By Organic Amine On Adsorbing CO₂ In Simulated Biogas

Biogas technology can not only solve the pollution problem caused by the random stacking of solid waste but also can solve the environmental problems caused by the use of traditional fossil fuels（coal,oil,etc）.CO₂ in biogas will reduce the calorific value of biogas and limit the application of biogas,so it is particularly important to separate carbon dioxide from biogas in the early stage.To solve the above problems,we prepared novel solid-state amines and tested the adsorption properties of adsorbents for CO₂ in simulated biogas.It provides a new research idea for preparing solid amine adsorbent with high adsorption capacity and hig h selectivity.In this paper,based on the current research status of solid amine adsorbents,a variety of porous materials were used as the adsorbent skeleton,amino-functional adsorbents were designed and prepared by the physical impregnation method that organic amine was loaded on the carrier material.The carrier and the prepared solid-state amine adsorbent were characterized by Fourier transform infrared spectroscopy（FT-IR）,N₂ absorption-desorption,scanning electron microscopy（SEM）,and thermogravimetric analysis（TGA）.At 25℃,0.2 MPa,100 ml/min,the dynamic separation method was used to test the prepared solid amine adsorbent for CO ₂ adsorption performance in simulated biogas.We analyzed the structure-activity relationship between the structure of the carrier and the organic amine on the performance of the solid amine.And by changing the temperature,gas flow rate,and other factors,we explored the effect of adsorption process conditions on the performance of the adsorbent.The conclusions of the study are as follows:（1）The macroporous resin（D101,ADS-17）was used as the carrier,and tetraethylenepentamine（TEPA）and polyethyleneimine（PEI）were used as organic amine modifiers.As the organic amine loading reached 40%,the adsorption capaci ty of both resin-based solid amines to CO₂ reached the maximum.For the same carrier,the small molecules TEPA obtain more uniform dispersion within the carrier pore unde r different loading amounts,so the adsorption of carbon dioxide by this kind of adsorbent is higher than that of resin carrier using PEI impregnation.It is worth mentioning,however,that resin carrier impregnated with organic amines PEI the same conditions have better thermal stability.Moreover,under specific conditions,when we used the same organic amine impregnated resin carrier,ADS-17 series of solid amines with carbonyl functional groups adsorbed more carbon dioxide than D101 series of solid amin es with larger surface area and pore volume.（2）The resin-based solid amine ADS-17-40%TEPA with the highest CO₂ adsorption amount was selected for temperature and flow rate testing.At 0.2 MPa,100 ml/min,the adsorption capacity of solid amine adsorbent for carbon dioxide gradually decreases as the adsorption temperature increases from 25℃-90℃.At 0.2 MPa and 25℃,when the intake air flow rate increases from 100 ml/min to 200 ml/min,the change of flow rate has little effect on the performance of adsorbent.（3）FNG-II type silica（FS）was selected as the carrier,and organic amine ethanolamine（MEA）and PEI were used as organic amine modifiers.The silica with MEA/PEI mixed impregnation has higher CO₂ adsorption performance and higher thermal stability compa red with the pure use of a certain organic amine impregnated FS carrier.With a simula ted biogas flow rate of 100 m L/min at 0.2 MPa and 25℃,FS-10%MEA-10%PEI exhibited a CO₂ adsorption capacity of ca.64.68 mg/g which increased by 81%in comparison to FS-20%PEI.The thermal stability of FS-10%MEA-10%PEI was higher than that of FS-20%MEA,and a further improvement of thermal stability was achieved with the increasing value of PEI/MEA weight ratio.As a result,the use of mixed amine impregnation carrier can improve the adsorption capacity of solid amine to CO ₂ and the thermal stability of solid amine adsorbent.Additionally,if the total percentage of amine was the same,FS impregnated by different ratios of PEI to MEA did not exhibit an obvious difference in CO₂ adsorption performance.FS-15%PEI-5%MEA can regenerate under mild conditions and it can keep high CO₂ adsorption activity after six absorption-desorption cycles.