Synthesis And Properties Of Porous Material For CO₂ Adsorption

The CO2 emissions in the atmosphere mainly come from the combustion of fossil fuels in power plants.In the near and medium term,China’s energy structure dominated by fossil energy is difficult to change.Therefore,the development of large-scale CO2 capture technology is the main way to reduce greenhouse gas emissions.Solid amine-based adsorbents have become one of the most potential research directions for CO2 capture due to their simple operation,no equipment corrosion and low energy consumption.Although a large number of literatures have reported various solid adsorbents,they still have many shortcomings.In order to prepare solid adsorbents with the advantages of fast adsorption/desorption,high mechanical strength,anti-ureaization,low energy consumption and long life,this paper proposes the idea of using acrylamide and glycidyl methacrylate as composite monomers to prepare adsorbents.The core-shell structure of the material is formed after synthesis.The wear resistance of the adsorbent can be effectively increased by using acrylamide with higher hardness as shell layer.Oil-soluble glycidyl methacrylate as core layer can improve the hydrophobicity of the material,thereby reducing the water adsorption of the material and the energy consumption of water evaporation in the process of regeneration.In addition,due to the presence of epoxy group in glycidyl methacrylate,polyethyleneimine can be firmly loaded by ring-opening reaction to avoid volatilization and abscission of amine molecules during the cycle,thus realizing long life cycle operation of adsorption materials.On this basis,this paper studies:(1)Inverse Phase suspension polymerization method was used to prepare porous material with acrylamide and glycidyl methacrylate as monomers.According to the microscopic mechanism of emulsion interface regulation,the effects of initiator,emulsifier and dispersed phase volume fraction on the size of microemulsion droplet were analyzed,and the optimum dosage of each component was determined,so that the pore size of the material was in the nanoscale range,in order to meet the requirements of high adsorption performance of CO2 in practical process.(2)Carbon dioxide adsorbent was prepared by loading polyethyleneimine onto the surface of core-shell structure material by chemical grafting method,and its structure morphology and adsorption performance were characterized and analyzed.The surface morphology of the adsorbent was determined by scanning electron microscopy,and the macropore size was 1-2 um.The contact angle of the material surface is 95.1°,which confirms that the material has certain hydrophobicity.The core-shell structure adsorbent was loaded with 50 wt.%PEI solution at 60℃,and the maximum adsorption capacity was 0.97 mmol/g.Thermogravimetric analysis showed that the adsorbent had good thermal stability below 200℃.In pure CO2 flow,the adsorption capacity decreased by only 2.7%after 50 cycles of adsorption at 85℃ and desorption at 135℃,indicating that the adsorbent has good urea resistance.(3)By optimizing the synthesis conditions of core-shell structure materials and CO2 adsorbent materials prepared by grafting polyethyleneimine the adsorption performance was improved.The surface contact angle of the optimized material is 97.5°,and the hydrophobicity is improved.In pure CO2 flow,the adsorption capacity of 50 wt.%polyethyleneimine was the highest at 85℃,which was 1.26 mmol/g.It took 8 minutes for the adsorbent to absorb completely and 12 minutes for the desorption completely,which indicated that the adsorption/desorption kinetics of the adsorbent was good.The adsorption material can be desorbed and regenerated by heating up to about 135℃.The regeneration conditions are mild,which is conducive to reducing costs.The isothermal adsorption line of the adsorbent material in pure CO2 gas stream is much higher than that in pure N2 gas stream,which proves that the adsorbent has good adsorption selectivity and is conducive to cost savings.After 50 cycles of adsorption/desorption in pure CO2 gas flow,the adsorption capacity decreased by 2.6%,indicating that the material has good stability in the cycle of adsorption/desorption.