Large-scale Synthesis Of ZIF-8 And ZIF-67 And Their Application In The Separation Of Gas/liquid Mixtures

This dissertation focuses on how to effectively capture CO₂ gas mixtures from flue gas,biogas,IGCC and recover high economic value ethylene from cracking dry gas in ethylene group.The aim is to capture CO₂ and C₂H₄ using slurry method and resolve the bottleneck problem of its industrialization,and expand the application of ZIFs in the treatment of wastewater containing phenol.The main contents of this work are as follows:（1）Based on the mixing solution reaction,the method of synthesizing ZIF-8 and ZIF-67 on a large scale was explored.By investigating order of charging,time of reaction,temperature of reaction,and molar ratio of raw materials measured by amount of substance,the optimized synthetic conditions were obtained.It was founded that the optimized synthetic conditions were charging 2-methylimidazole first,then adding Co（NO3）2·6H2O（the molar ratio for Co（NO3）2·6H2O,2-methylimidazole and Deionized water is 1 : 8: 1617）,and making reacting at 20 centigrade for 20 mins.In addition,a scale production platform was built,and the trial production process for ZIFs materials was developed.ZIF-8 and ZIF-67 were synthesised successfully at room temperature and the large-scale production amount reached 1-2 kg per day.（2）The CO₂ capture ability of dry material ZIF-67,ZIF-67/ glycol,and ZIF-67/ethylene glycol-2-methylimidazole slurry were compared.The different separation conditions（temperature,solid holdup,gas-liquid ratio,and pressure）of slurry system to capture CO₂（CO₂/N2,CO₂/CH4,and CO₂/H2）gas mixture were investigated.It was founded ZIF-67/glycol-m Im slurry exhibits the highest separation selectivity.The highest separation factors using ZIF-67/glycol-m Im slurry for H2/CO₂,N2/CO₂,and CH4/ CO₂ are 1409,723,and 222,respectively.In addition,the apparent solubility of CO₂ in the slurry reaches 1.3 mol L-1at 1 bar and 303.2 K,which is slightly higher than the previous reported value of 1.25 mol L-1for the ZIF-8/glycol-m Im slurry.（3）A carbon dioxide capture evaluation device of slurry was built and the gas breakthrough experiment using ZIF-67 slurry on the bubble column was carried out.By comparing the CO₂ capture abilities of liquid glycol,ZIF-67/glycol slurry,glycol-m Im solution with 40 wt% m Im,ZIF-8/glycol-m Im slurry,and ZIF-67/glycol-m Im slurry,the CO₂ capture amounts are increased in turn.In addition,the result show that when the ZIF-67 mass fraction is 0.15,slow flow rate of gas mixture,low absorption temperature,and high pressure are favorable for slurry to capture carbon dioxide.（4）The application of ZIFs in liquid phase adsorption was expanded.By carrying out adsorptive removal of phenol from aqueous solution with zeolitic imidazolate framework-67,the effects of p H,contact time,and temperature on the adsorption behavior were evaluated.It was founded that the best adsorption conditions are p H of 9,the reaction time of 12 hours,and temperature of 25 ℃.The suitability of the Langmuir adsorption model to the equilibrium data was investigated for each phenol-adsorbent system.The results show that the equilibrium data for all the phenol-sorbent systems fitted the Langmuir model.In addition,the adsorbent could be perfectly regenerated at120 °C with little loss of the adsorption ability.（5）By using ZIF-67/water-ethylene glycol slurry,methane/ethylene gas mixtures were separated with the absorption-adsorption method.The influences of temperature,mass fraction of ZIF-67 in ZIF-67/water-ethylene glycol slurry,pressure,and gas-slurry ratio on the separation performance were studied systematically.It was founded that lower temperature,mass fraction of ZIF-67 of 0.15,higher gas-liquid ratio,and higher operation pressure are suitable for separation of methane/ethylene mixture.The experimental results show by using the slurry,the mole fraction of ethylene in gas phase decreases from 74.8 to 53.0%,the selectivity coefficient reaches 10（much higher than that of solid ZIF-67）,and more than 68% of C₂H₄ can be recovered after one stage of the absorption-adsorption process.In addition,the crystal structure of ZIF-67 remains intact after 20 adsorption/desorption cycles.（6）A continuous gas separation experiment device with slurry was built and the corresponding evaluation experiment were carried out.The effects of absorption and adsorption temperature and flow rate of inlet on CO₂/CH4 continuous separation using ZIF-8 slurry were studied.It is found that the lower temperature and air flow rate,the better separation ability and the higher CO₂ capture capacity.In addition,the results show the higher desorption temperature,the higher utilization rate of the slurry.The influence of pressure on ZIF-8 slurry was also studied and the high sorption pressure is favorable for slurry to capture carbon dioxide in the gas mixtures.