Carbon dioxide permselective

Table 4.4 Carbon dioxide (A)/nitrogen (B) permselectivity characterization for polyimide, polyurethane and polyamide block-copolymers containing polyether segments.

Since IBM s offer greater stability than ILM s and greater selectivity and permeability than PM s, it would be useful to be able to model transport processes in these materials and to predict the effectiveness of facilitated transport based on relevant physical properties (RPP). Although it may be necessary to modify the model developed for ILM s in order to completely describe transport processes in IBM s, it is likely that moat of the same RPP s of the system will be Important. The purpose of this section is to point out that measurement of RPP s in IBM s, especially permselective IBM s, may be difficult. Although problems with model development and property measurement exist, carrier Impregnated IBM s can produce rapid and selective separations of gas mixtures. Way and co-workers have incorporated the monoprotonated ethylenediamlne cation into Nafion membranes to achieve the separation of carbon dioxide from methane (25). 

Permselective membrane n. A thin film that will preferentially permit gases of different kinds to pass through the film at different rates. For common gases such as hydrogen, oxygen nitrogen, and carbon dioxide, silicon rubber is the most permeable polymer. 

Fujiwara et al. (2011) showed the possibility of preparing reversible air electrodes that can be used in metal-air storage batteries or unitized regenerative fuel cells. To reduce the impact of atmospheric carbon dioxide the reversible air electrodes were integrated with a polymer anion-exchange membrane which was placed between the cathode s catalytic layer (with Pt and Pt-Ir catalysts) and the alkaline solution. The membrane with anion permselectivity presumably inhibited the permeation of COj cations to the air electrode and thus suppressed precipitation of carbonates in pores of the air electrode. 

The journal and patent literature was searched to identify the 87 polymers used in this work. They include members from the polymers, their structure, and gas transport properties are provided in the Appendix. Carbon dioxide is reported to permeate many polymers by a dual mode transport mechanism (13). It has also been noted that COj has a plasticizing effect on some polymers leading to decreased permselectivity at high pressure (14). For these reasons we have preferentially used pure gas permeability data obtained at 10 atm CO2 and 35°C. 

A novel nanocomposite membrane, poly dimethyl siloxane (PDMS)/Au was prepared for carbon dioxide/methane separation. Synthesis of stabilized nano particles is also reported. The nanoparticles were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM). The hybrid membrane was characterized morphologically by scanning electron microscope (SEM) and the change in inter-segmental distance due to filler loading by wide angle X-ray diffraction patterns (WAXD). The gas transport properties were measured at different pressures and temperatures. The effects of filler loading on permselectivity, diffiisivity selectivity and solubility selectivity are reported for CO2/CH4 separation. Reverse selective phenomena of PDMS/Au nanocomposite membrane over the conventional PDMS membrane is explained based on sorption kinetics of CO2. 

The analytical application of particle-dispersed-modified electrodes to the selective detection of a single analyte is limited because of broad catalytic activities thus their use as electrochemical detectors following chromatographic separation of carbohydrates is often suggested. Similar nonspecific catalytic PMEs consisting of electrocatalytic RUO2 particles and Ru(OH2)6 in Nafion have been shown to catalyze the oxidation of catechol and of alcohols, respectively these could presumably be used in place of the carbon paste Ru02-modified electrode developed for postseparation detection of carbohydrates and alcohols. Other electrocatalytic particle electrodes were prepared from lead dioxide in polypyrrole and CoPc entrapped behind a permselective cellulose acetate film. ... 

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