Synthesis And CO₂ Adsorption Properties Of Exfoliated Vermiculite Nanosheets Supporting Amine

Since the industrial revolution,the energy structure around the world has increasingly skewed towards the use of fossil fuels.As a result,the concentration of CO₂ in the atmosphere increase year by year,causing a sequence of hostile environmental problems such as global warming and sea level rise.The use of low carbon energy and renewable energy is the key to the transformation of the world energy pattern to the low-carbon in the future,but the dependence on fossil fuels cannot be solved overnight.In the present,the use of CO₂ capture,utilization and storage?CCUS?technology is one of the most efficient and feasible methods to reduce the concentration of CO₂ in the atmosphere on a large scale.The appropriate CO₂ capture technology is a critical process to reduce CO₂ emission into the atmosphere.Here we report a novel inexpensive composite adsorbent for capturing CO₂.The composite was prepared by supporting tetraethylenepentamine?TEPA?onto exfoliated vermiculite?E-VER?nanosheets using wet-impregnation and freeze-drying methods.Vermiculite,as a cheap and natural abundant clay,was delaminated into ultrathin nanosheets via liquid phase exfoliation.The negatively charged E-VER has exposed surfaces and a large surface area,which is ideal for supporting TEPA with desired loading.Six adsorbents of E-VER/TEPA composites with different TEPA loading were developed?The mass ratios of TEPA and E-VER are 0,0.2,1,2,10,and 50 wt%,respectively?.All the samples were analyzed by SEM,FT-IR,XRD,BET,Pore size distribution and TGA.Subsequently,the CO₂ adsorption performance of the 6 different samples were investigated.The experiment was carried out at25,50,and 75°C over a wide range of pressures?0-50 bar?by high pressure volumetric analyzer?HPVA-??.The exfoliation method used in this work can improve the CO₂ adsorption performance of the materials effectively.The CO₂ adsorption capacity of original vermiculite granules is only6.97 mmol/g at 25?,while the adsorption capacity of E-VER can reach 22.5 mmol/g at about45bar.It is found out that the TEPA loading has an important impact on the pore structures,surface areas and the CO₂ adsorption capacities.E-VER-TEPA-2%with a TEPA loading of 2%demonstrates the optimal performance for CO₂ capture,showing a CO₂ adsorption capacity of29.5 mmol/g at 45 bar and 25?,which corresponds to an increase of 31.11%compared to E-VER.As the adsorption temperature raising to 50?and 75?,the CO₂ adsorption capacity decreased to 25.9 and 22.4 mmol/g respectively.This can be explained that the increased adsorption temperature reduces the CO₂ uptake capacity of the modified samples by inhibiting the material physical and chemical adsorption.The E-VER/TEPA composites are compressible,a volumetric capacity of 29.93 mmol/cm³ was obtained for E-VER-TEPA-2%at 45 bar and25?after being compressed at 20 MPa.Furthermore,E-VER/TEPA composites exhibited good cyclic stability over 6 cycles and long-time heat-treatment.A CO₂ adsorption capacity can be obtained after 6 cycles at 25?,corresponding to a slight drop of 3.3%.As for the cycling at 50?,the drop is 3.6%after 6 cycles.This work provides a powerful method to make composites of inorganic and organics with the 2D supporting materials for high-efficiency CO₂capture under elevated pressure,which may also find other potential applications,such as gas separation.