| Propylene is an extremely important raw material for energy and industrial chemical.Data in recent years shows that China has been in a short supply state of propylene for a long time.At present,the production process of propylene mainly includes crude oil route and non-crude oil route,but no matter which route is adopted,the obtained product needs to be further separated and purified before it can reach the standard of commercial production.Separation of propylene/propane gas is particularly important in the petrochemical industry due to the similar properties of the two gases.The separation of propylene/propane is currently realized by the relatively expensive intensive chemical distillation method,which requires large investment and high energy consumption,which is not economical.Membrane separation technology has gradually replaced traditional distillation-based separation methods and has become an attractive method due to its low cost and high energy efficiency.Among membrane separation materials,mixed matrix membrane is a new type of membrane material with polymer matrix as continuous phase and inorganic particles as dispersed phase.It combines the unique advantages of inorganic particles in gas adsorption and separation and the good processing performance of polymer materials,which holds great promise for industrial applications in gas separation.The biggest challenge in the preparation of mixed matrix membranes is how to improve the poor interfacial compatibility between filler and matrix.In this thesis,the effective separation of propylene/propane was taken as the research goal,for the preparation of mixed matrix membranes,metal-organic frameworks with excellent gas adsorption and separation performance were selected as the dispersed phase,and polyimide was used as the matrix.The specific work is as follows:(1)According to the sizes of propylene and propane(4.0 ? and 4.3 ?),metal-organic framework ZnF(daTZ)with a pore size of 4.2 ? was selected as the filler.In order to reduce the effect of interfacial compatibility of fillers and polymer materials on the properties of mixed matrix membranes,we first synthesized nano-sized ZnF(daTZ)particles by adjusting the solvothermal reaction conditions.The structure,morphology,stability and adsorption properties of the obtained materials were characterized and analyzed by X-ray powder diffraction,scanning electron microscopy,thermogravimetric analysis and gas adsorption tests.The experimental results show that the synthesized nano-sized ZnF(daTZ)material has good hydrothermal stability and gas separation potential,which lays a solid foundation for the preparation of mixed matrix membranes.(2)Using nano-sized ZnF(daTZ)as filler and polyimide 6FDA-DAM as matrix,ZnF(daTZ)/6FDA-DAM mixed matrix membranes with different MOF loadings were prepared by solution casting method.The characterization results showed that the ZnF(daTZ)particles were successfully combined with 6FDA-DAM matrix.Subsequently,we carried out two-component gas permeation test,single-component gas permeation test and cycle test respectively.The optimum pressure for the mixed matrix membrane test was determined to be 0.1 MPa and the optimum temperature was 35 ℃ by the two-component gas permeation test.Under the optimal test conditions,the mixed matrix membrane with a loading of 11.6% has the highest separation effect,and the separation ratio can reach 11.5 while maintain a high permeability(42.8 Barrer).Permeability of propylene in the single component test was up to 78.85 Barrer with a separation ratio of 17.6.In addition,ZnF(daTZ)/6FDA-DAM membrane exhibited excellent stability in the cycle test,and the permeation of propylene could be maintained at around 35 Barrer under the two-component test cycle of up to 12 hours with selectivity remaining largely unchanged. |
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