Synthesis And Performace Research Of Micropore MOFs For Inverse Selective Ethane/Ethylene Separation

As the largest raw material in organic chemicals,ethylene is deep in the petrochemical neighborhood and has a huge downstream industrial chain.Efficient removal of impurities such as ethane from pyrolysis gas is the key to ethylene purification and deep processing.At present,the industry mainly uses multi-stage cryogenic distillation separation technology,using the subtle difference in the boiling point of ethane ethylene to separate it.The process infrastructure investment is large,the energy consumption is high,and it does not meet the requirements of green,low-carbon,and sustainable development.Pressure swing adsorption separation technology is environmentally friendly and energy-efficient,and is considered to be the most promising alternative for the separation of light hydrocarbons.Metal-organic framework materials have become the most promising adsorption materials in pressure swing adsorption separation due to their diverse composition and customizable pore structure.Compared with the adsorbent that preferentially adsorbs ethylene,MOFs materials that can preferentially capture ethane in binary mixtures can greatly reduce the amount of adsorbent and the cost of the treatment process,and the separation process is further simplified.Therefore,the design and construction of high-efficiency ethane-selective MOFs materials have important academic value and application prospects.From the perspective of adsorption material selection and adsorption performance regulation,this thesis conducts a series of studies on ethane selective adsorbents,and the main research content and conclusions are as follows:1.Inspired by relevant work,a series of ultra microporous formate MOFs[M₃（HCOO）₆]（M=Co,Mn,Ni,Mg,Zn）without open metal sites were synthesized according to literature methods,and the materials were characterized and tested for adsorption performance.The experimental results show that this type of material has good thermal stability,and the atmospheric ethane adsorption capacity of MOFs is greater than that of ethylene at 298 K or303 K.Thanks to the abundant metal oxygen bonds and pore size and structural characteristics in the skeleton,they all exhibit a greater affinity for ethane.2.Considering that[Cu In（ina）₄]·2DMF,[Ag In（na）₄]·2DMF and[Cu In（na）₄]·1.5DMF three bimetallic ultra microporous MOFs have no open metal sites and good solvent stability.They were synthesized using short ligand pyridinic acid and two transition metals according to literature.The basic characterization and C₂H₆/C₂H₄ adsorption performance testing of the materials showed that the bimetallic series materials can achieve C₂H₆/C₂H₄ adsorption separation inversion,and[Cu In（ina）₄]·2DMF has the best separation performance in this chapter.The adsorption heat and C₂H₆ adsorption selectivity of the material were calculated.Finally,Monte Carlo（GCMC）simulations were used to reveal the selective adsorption mechanism of ethane on[Cu In（ina）₄]·2DMF materials.3.Through the investigation and screening of numerous MOFs structures,we investigated the adsorption and separation of C₂H₆/C₂H₄ by the framework using the reported porous material NOF-2 with cage shaped pores,no open metal sites,and abundant nitro oxygen in the pores.The adsorption performance of C₂H₆/C₂H₄ was compared through the single component gas adsorption isotherm.Whether at 298 K or 303 K,the atmospheric ethane adsorption capacity of MOFs is greater than that of ethylene.Inspired by reports that the adsorption and separation performance of modified MOFs modified after synthesis has been improved,18-crown ether-6 loaded with oxygen atoms was used in the larger pores of NOF-2 for the adsorption and separation of C₂H₆/C₂H₄.This not only increased the contact area between ethane and the pore wall,but also utilized the bonding advantage of ethane,significantly enhancing the selectivity of ethane adsorption.