Carbon Coating Modification Of Zeolite Particle Surface And Its Gas Adsorption Performance

Zeolite（also known as molecular sieve）is a microporous aluminosilicate,with large specific surface area,narrow pore size distribution and good tunability etc.It is widely used in gas separation and storage,gas sensor,supercapacitor,lithium ion battery,photocatalysis,polyphase catalysis,and other fields.However,zeolites generally contain a large number of polar groups,which tend to adsorb water molecules,resulting in blockage of their pore channels and loss of adsorption activity.In this paper,we propose to encapsulate zeolite particles with fluorine-containing polymers and obtain microporous carbon encapsulated zeolite particles with core-shell structure after controlled carbonization（13X@MPC）,Achieve hydrophobic modification of zeolite particles to reduce water molecule adsorption.Further,the CO₂,H₂O and VOC molecules adsorption properties of 13X@MPC were evaluated.Explored the potential of 13X@MPC for flue gas capture and air cleaning applications.Validated the concept of 13X@MPC for direct in-situ air purification during Li-air battery operation.Specifically divided into the following three aspects:（1）Study on the water absorption property and VOCs adsorption performance of zeolite particles,three commercial zeolite particles were characterized to determine that they belong to X type and ZSM-5 type molecular sieves,respectively.The hydrophobicity and adsorption performance of three molecular sieves in the field of VOCs were investigated.Among them,the equilibrium adsorption capacity of 13X for VOCs and H₂O was 296 mg g^-1（B）,112 mg g^-1（T）,140 mg g^-1（CB）,101 mg g^-1（p X）,230 mg g^-1（o X）,215 mg g^-1（m X）,144 mg g^-1（H₂O）.13X exhibited high hydrophobicity as well as adsorption ability.Select the best sample and proceed to the next cladding modification.（2）Preparation of microporous carbon-coated zeolite particles and their performance for carbon capture in wet flue gas,13X@MPC covered with hydrophobic carbon layer was prepared by high temperature carbonization of polyvinylidene fluoride（PVDF）as precursor,and the thickness of the hydrophobic carbon layer was about 4μm.The adsorption performance of 13X and 13X@MPC on CO₂ and H₂O was systematically evaluated.13X@MPC（25,550）shows a high CO₂ uptake(76.2 cm³ g^-1)as the same as zeolite 13X.Especially,the H₂O uptake of 13X@MPC（25,550）is only157.1 cm³g^-1 which is almost half to zeolite 13X(315.2 cm³ g^-1).It is shown that the carbon layer can effectively reduce water adsorption.Separation experiments further verified that 13X@MPC has good carbon uptake in wet flue gas,and the CO₂ retention time of 13X@MPC（25,550）was almost 5 times longer than that of 13X under the same conditions.（3）Microporous carbon-coated zeolite composite film for Li-air battery research,the good water-repellent property of modified molecular sieve material is expected to be used as solid ion-conducting membrane in Li-air batteries working in ambient air.Therefore,the optimal modification conditions in the modified samples were selected to prepare solid molecular sieve membranes for application in Li-air batteries.Experimental results show that the cycle performance of 13X@MPC（25,550）air battery is improved to more than 38 h compared to the air battery assembled with 13X（18 h）,optimization of related results is further in progress.