Preparation Of Hierarchical SAPO Molecular Sieve And It’s N₂-CO₂ Separation Performance

SAPO molecular sieve has a special crystal structure,and many types,with a certain size,unique pore structure and large surface area,strong coulomb field and polarity in the crystal,so that the molecular sieve has a strong adsorption and separation performance.The multi-porous SAPO molecular sieve has introduced mesoporous or macroporous into the original microporous structure,which can enhance mass transfer efficiency and improve adsorption and separation performance.In this paper,TEAOH and TEA were used as templates to synthesize different SAPO molecular sieves by two stages of hydrothermal crystallization at high and low temperature.The molecular sieves were characterized by XRD,SEM and N2 adsorption and desorption,and the effects of crystallization temperature and time on the structure and morphology of the products were studied.N2-CO2 adsorption separation performance of molecular sieve was studied in a fixed bed separation unit.The main results are as follows:(1)SAPO-34 molecular sieve was synthesized using TEAOH as template.The main morphology of SAPO-34 molecular sieve is cube and sphere,and the second phase crystallization time affects particle size.The synthesized molecular sieves have a large number of micropore structures.With the extension of crystallization time,the surface area and micropore volume of samples decrease at low temperature and increase at high temperature.All samples have multistage pore structures.Under the condition of 15 ℃,the adsorption capacity of CO2 in CO2-N2 mixture by molecular sieve increased significantly,and the adsorption capacity reached up to 3.75 mmol/g.The adsorption equilibrium takes longer.At low pressure,the temperature change had little effect on adsorption capacity.(2)SAPO-5 molecular sieve was synthesized using TEA as template.Molecular sieve with cube and prism morphology mainly,with the change of two-stage crystallization time will occur agglomeration phenomenon,crystallization time affects the change of cube and spherical particle size,increasing temperature will promote dissolution,promote the formation of pore structure.Samples of SAPO-5 molecular sieve samples have a large number of microporous mesoporous structures.The crystallization time affects dissolution and dissolution,and then affects the specific surface area and pore volume of the samples.All samples have multistage pore structures.The adsorption of CO2 by molecular sieve in CO2-N2 mixture was 200 KPa,and the adsorption capacity increased significantly at 15 ℃,with the maximum adsorption capacity reaching 3.30 mmol/g.