Study On Competitive Adsorption Mechanism And Process Of Adsorption Separation For CHCIF₂/CHF₃

Organic fluorine chemical industry is an indispensable industry for developing advanced science and technology,developing modern national defense,and improving the modern material and spiritual life of the world.CHClF₂ is the basic raw material as the largest amount of refrigerant and widely used in fluorine-containing polymer materials and fluorine fine chemicals.Its technical level is of great significance for improving the overall development of China's organic fluorine chemical industry.The key point of the development of CHClF₂ technology is the efficient separation of CHClF₂/CHF₃.The pressure swing adsorption separation technology with low energy consumption and flexible operation has attracted much attention.However,there is no systematic and in-depth study on the mechanism and process of adsorption and separation of CHClF₂/CHF₃.The thermodynamic and dynamic properties of the host-guest system in the adsorption process are vital to grasping the nature of the adsorption process.Understanding the thermodynamics and kinetics of the host-guest system can provide qualitative and quantitative basis for the application of porous materialsand process design.Based on the adsorption separation process,the competitive equilibrium adsorption mechanism and diffusion coefficient of CHClF₂/CHF₃ on microporous carbon and FAU molecular sieve were studied respectively.The two-stage adsorption separation of CHClF₂/CHF₃ mixture was designed based on the equilibrium adsorption mechanism and diffusion study.And the rectification-pressure swing adsorption coupling separation process realizes the effective separation of CHClF₂and CHF₃ products.Firstly,the adsorption behavior of CHF₃/CHClF₂ mixture on different activated carbon was investigated using GCMC simulation in combination with breakthrough curve experiments technology.The effects of microporous carbon pore size and surface functional groups on the separation of CHF₃ and CHClF₂ were investigated.The influence of conditions was analyzed on the adsorption and separation of CHClF₂/CHF₃,such as cations position,Si/Al ratio and adsorption temperature of FAU zeolite using GCMC simulation in combination with in-situ FTIR and MAS NMR spectra menthod.The main influence factors affecting the adsorption separation of CHClF₂/CHF₃ and the suitable microporous carbon and FAU zeolite for the separation of CHClF₂/CHF₃ mixture are theoretically discussed.The results show that the simulated results of equilibrium adsorption and separation selectivity are in good agreement with the experimental results.The established model and molecular simulation method can accurately predict the competitive equilibrium adsorption process of CHClF₂/CHF₃ on microporous carbon and FAU molecular sieves.The establishment of this calculation model greatly simplifies the experimental process of screening adsorbent.From the perspective of separation effect,the microporous carbon adsorbent with high selectivity of CHClF₂/CHF₃ was mainly distributed at 5.67?,and the FAU molecular sieve adsorbent 88Al FAU with high selectivity was elected.The adsorption isotherm of CHF₃/CHClF₂ on microporous carbon conforms to typical Langmuir type,while the adsorption isotherm on FAU molecular sieve conforms to typical Langmuir-Freundlich type.Then,the effects of various resistances on the total mass transfer coefficient of CHF₃/CHClF₂ mixture in the mass transfer of microporous carbon and molecular sieve were investigated by MD simulation and fixed bed dynamic breakthrough experiment combined method.The macropore diffusion resistance plays a crucial role in the total effective diffusion,and the microporous diffusion resistance has less influence when CHF₃/CHClF₂ diffuses on the microporous carbon PK1 and 88Al FAU zeolite.Finally,based on the competitive equilibrium adsorption mechanism and diffusion coefficient of CHClF₂/CHF₃,we designed two-stage pressure swing adsorption separation and rectification-pressure swing adsorption coupling separation using homemade microporous carbon PK1 and 88Al FAU zeolite as adsorbents.The effects of the main operating variables on the purity and recovery of the product gas were investigated by using dynamic numerical model simulation in Aspen Adsorption software.Under the optimal process parameters of two-stage pressure swing adsorption separation process,CHF₃ purity,CHF₃ recovery rate,CHClF₂ purity and CHClF₂ recovery rate were 99%,77.71%,99.5%,and 72.13%,respectively.CHF₃/CHClF₂ rectification-pressure swing adsorption coupling separation process,under the optimal process conditions,CHF₃ purity,recovery,system energy consumption were 99.999%,69.52%,kJ?kg^-1 CHF₃,respectively.