Abstract
ABSTRACTThree soluble hyperbranched polyazomethines containing oligosiloxane end group HBP-PAZ-SiOn were successfully synthesized. HBP-PAZ-SiOns were used as modifiers of ethyl cellulose (EC) and polysulfone (PS) membranes. Blend membranes, HBP-PAZ-SiOn/EC and HBP-PAZ-SiOn/PS were prepared by blending the THF solution of HBP-PAZ-SiOn with ethanol solution of EC and dichloromethane solution of PS, respectively. Surprisingly, the permeabilities for CO2 of the blend membranes were more than 15–16 times higher than those of pure EC and PS membranes without any drop of pemselectivity to N2. This unusual improvement has been achieved by both enhancement of diffusivity for carbon dioxide and nitrogen by the oligosiloxane groups and enhancement of affinity of the amino groups with carbon dioxide at the end groups of HBP-PAZ-SiOn.
Highlights
Many gas permselective membranes have been reported in the past three decades as energy saving separation process because they can solve recent environmental problems [1–12]
Hyperbranched polymers (HBP) have been reported, and they have high solubility compared with the corresponding linear ones. [24–34] Since insoluble polymers are not suitable for permselective membranes materials, we selected HBP of PAZ (= HBP-PAZ)
In order to enhance solubility of HBP-PAZ, we introduced oligosiloxane chains with a different length by reaction with an oligosiloxane end capping reagent to the end of HBP-PAZ to give HBPPAZ-SiOn
Summary
Many gas permselective membranes have been reported in the past three decades as energy saving separation process because they can solve recent environmental problems [1–12]. Membranes permeating carbon dioxide selectively are very important in view of solving the global warming problem. They can eventually remove CO2 from flue gas [3,13–17]. Polymers which may have high permeability and pemselectivity tend to have low membrane forming ability. To overcome these problems, more precise design of chemical structures of polymers used for permselective membranes is needed. Their performances as CO2 permeation membrane materials were estimated by using blend membranes of HBP-PAZ-SiOn with substrate polymers, ethyl cellulose (EC) and polysulfone (PS)
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