Preparation Of Modified Polyether Ether Ketone And Application For CO₂ Capture

As one of the main greenhouse gases and an important “potential carbon resource”, the separation and purification of CO2 obtained widely attention. Compared with the previous CO2 separation methods, membrane separation technology has incomparable advantages. A series of modification based on the basic material polyether ether ketone(PEEK) were conducted to prepare polymer membranes for CO2/CH4 separation. The major studies were as below:Polyether ether ketone was sulfonated by concentrated sulfuric acid to fabricate SPEEK with different sulfonation degree(DS), it was a polymer electrolyte material with high water absorption and swelling properties. SPEEK membranes were prepared by casting method and used for CO2/CH4 separation. The effects of SPEEK membrane with different DS, feed gas pressure and operating temperature acted on the physical and chemical properties and separation performance of the membranes were investigated. The results showed that the increased DS of membrane increase the water content in the membrane and led to an improvement in gas separation performance. Considering the separation performance and mechanical strength of the membrane, SPEEK with DS of 65% was used in the further study. CO2 permeability of SPEEK-65 was 25.4 Barrer, and CO2/CH4 selectivity was 37.Three phosphate salts(Na H2PO4、Na2HPO4、Na3PO4) with different acid base properties were selected and doped in SPEEK membranes in order to separation CO2/CH4 mixtures. The effects of salt types, salt contents and different operating conditions(temperature, pressure) on the physical and chemical properties and separation performance of the membranes were investigated. The results were as follows: SPEEK/phosphate salts membranes exhibited higher CO2 separation performance than pure SPEEK membrane, and the CO2 separation performance of three SPEEK/phosphate salt membranes at the same salt loading was: SPEEK/Na3PO4 > SPEEK/Na2HPO4 > SPEEK/Na H2PO4. The doped of salts and the increase basicity of the salts were beneficial for the transport of CO2. The CO2 permeability and CO2/CH4 selectivity of SPEEK/Na3PO4-10 membrane were 62.0 Barrer and 61.0, respectively.SPEEK/lysine salt membranes were prepared and utilized for CO2/CH4 separation. Solutions of lysine and sodium hydroxide were prepared and mixed at equimolar ratio. The effects of salt contents and different operating conditions(temperature, pressure) on the physical and chemical properties and separation performance of the membranes were investigated. The results were as follows: CO2 permeability and CO2/CH4 selectivity simultaneously increased as the lysine salt content in the membrane increased. The existed of lysine salt contributing to the increase of water content, the polar –COOH enhanced the solubility mechanism, and the amine groups will increase reactivity-selectivity. All of these coordination functions lead to the facilitated transport of CO2 in the membrane. At a lysine salt content of 20 wt%, the membrane showed CO2 permeability of 295.6 Barrer, with CO2/CH4 selectivity of 71.8.