Research On Preparation Of Vermiculite-based Carbon Dioxide Adsorption Materials And The Performance Enhancement Mechanism

The capture,storage and resource utilization of CO₂ is the most effective way to reduce the harm of greenhouse gases to nature and achieve the goal of“double carbon”.As an important technical means to achieve efficient and recyclable utilization of CO₂ resources,post-combustion CO₂ capture technology plays an important role in improving CO₂ capture performance and has good industrial application prospects.This paper aims to explore the functional modification technology of layered mineral vermiculite and enhance its CO₂capture performance as well as prepares modified vermiculite-based adsorption material.Through the in-depth study of its synthesis process,structural change,morphological characteristics,pore structure,CO₂ adsorption performance and cycle stability,the main results are as follows:The structural cations of the silica-based adsorbent are leached from the expanded vermiculite network to form hierarchical interlayer pores and mesopores（10～15 nm）,which provide a good active site for gas mass transfer and diffusion,and significantly improve the CO₂ adsorption performance（0.26 mmol/g）.The large number of hydroxyl groups within the silica-based adsorbent facilitates the bonding of specific functional groups of the adsorbent and modifier to form a strong adsorption layer,creating favourable conditions for further interlayer structural modulation and laying the structural basis for CO₂ adsorption and stability improvement.During the preparation of modified vermiculite/ionic liquid composite adsorbent by using wet impregnation method,the type of ionic liquid,ionic liquid loading,adsorption temperature,CO₂ partial pressure and gas concentration all affect the CO₂ adsorption performance.When20%（mass fraction）1-Butyl-3-methylimidazolium tetrafluoroborate（[Bmim][BF₄]）was loaded,the CO₂ adsorption capacity was 1.28 mmol/g at 35°C,40%CO₂ and 75 m L/min,and the cycle stability was 41.94%higher than that of the silica-based adsorbents.This is mainly due to the strong affinity and good solubility of ionic liquids for CO₂,and the interaction between ionic liquids and porous carriers enhances the mass transfer and diffusion of CO₂.The improvement of CO₂ performance of solid amine adsorbents is closely related to the structure and properties of the matrix.Good pore structure provides good support for the loading of organic amines and the capture of CO₂.The modified vermiculite/porous carbon/PEI solid amine adsorption material was obtained by in-situ carbonization of porous carbon implanted between the silica-based adsorbent layers and further loading PEI.The CO₂adsorption capacity was determined to be a ternary function of PEI molecular weight（Mw=600）,adsorption temperature（75°C）and CO₂ partial pressure（60%）.The optimal CO₂ adsorption capacity was 1.84 mmol/g.Through in-depth analysis of the structure and performance of the adsorbent,it is shown that the porous carbon network is a graphene-like material with thermal conductivity(0.289 W·m^-1·K^-1),which greatly enhances the CO₂ capture performance.In addition,a strong spatial confinement effect is formed after in-situ carbonization,which slows down the formation of urea bonds while obtaining good thermal conductivity,avoids continuous overheating during CO₂ adsorption and PEI deactivation/agglomeration,and obtains superior cycle stability（decreased by 7.6%）.The results of adsorption heat value,adsorption kinetics and thermodynamics show that the amino-functionalized adsorption process is a physical-chemical synergistic adsorption,which can greatly improve the CO₂ adsorption capacity and cycle stability.