Carbon dioxide permeation studies

Bassi and Davies [7] have described a method for testing carbon-dioxide permeation through a ceramic tile coated with the material under study. The carbon-dioxide resistance may be expressed in various units, of which the equivalent air thickness is most commonly used. An empirical criterion is that a coating should have the same resistance to COj transport as 50 m of still air. A wide range of organic coatings (plus a silicate and a polymer-modified cementitious coating) was tested. 

The permeation properties of substituted PPO to a carbon dioxide, methane, nitrogen mixture were studied for several systems. The results are presented in Table VI. 

Polymers Mixed by Milling. The effect of EVA concentration in the blends on gas permeation and light transmission through the film was studied. The permeability and the diffusion coefficients at 50 °C for the penetrants helium, argon, and carbon dioxide are shown in Figures 1, 2,... 

The use of membrane introduction mass spectrometry (MIMS) was first reported in 1963 by Hoch and Kok for measuring oxygen and carbon dioxide in the kinetic studies of photosynthesis [46], The membrane module used in this work was a flat membrane fitted on the tip of a probe and was operated in the MIS mode. The permeated anaytes were drawn by the vacuum in the MS through a long transfer line. Similar devices were later used for the analysis of organic compounds in blood [47], Memory effects and poor reproducibility plagued these earlier systems. In 1974, the use of hollow-fiber membranes in MIMS was reported, which was also operated in the MIS mode [48], Lower detection limits were achieved thanks to the larger surface area provided by hollow fibers. However, memory effects caused by analyte condensation on the wall of the vacuum transfer line remained a problem. 

Many computational studies of the permeation of small gas molecules through polymers have appeared, which were designed to analyze, on an atomic scale, diffusion mechanisms or to calculate the diffusion coefficient and the solubility parameters. Most of these studies have dealt with flexible polymer chains of relatively simple structure such as polyethylene, polypropylene, and poly-(isobutylene) [49,50,51,52,53], There are, however, a few reports on polymers consisting of stiff chains. For example, Mooney and MacElroy [54] studied the diffusion of small molecules in semicrystalline aromatic polymers and Cuthbert et al. [55] have calculated the Henry s law constant for a number of small molecules in polystyrene and studied the effect of box size on the calculated Henry s law constants. Most of these reports are limited to the calculation of solubility coefficients at a single temperature and in the zero-pressure limit. However, there are few reports on the calculation of solubilities at higher pressures, for example the reports by de Pablo et al. [56] on the calculation of solubilities of alkanes in polyethylene, by Abu-Shargh [53] on the calculation of solubility of propene in polypropylene, and by Lim et al. [47] on the sorption of methane and carbon dioxide in amorphous polyetherimide. In the former two cases, the authors have used Gibbs ensemble Monte Carlo method [41,57] to do the calculations, and in the latter case, the authors have used an equation-of-state method to describe the gas phase. 

Carbon dioxide is the major compound of greenhouse gases the emission of which should be reduced. Membrane technology is one of the most promising methods for this purpose since it may be able to recover CO2 at elevated temperatures without losing sensible heat [1-4]. In this study, Y-type zeolite membranes were developed, and their C02-selective permeation was evaluated. 

The regeneration of supercritical carbon dioxide from a mixture containing caffeine by microporous MFI zeolite and mesoporous silica membranes supported on alumina was studied. The experimental data show that a caffeine rejection higher than 90% or 70% and a permeation flux of supercritical carbon dioxide more than 0.05 or 0.07 mol/m /s could be obtained at 10.5 MPa. 

Defect free DD3R supported membranes have been newly prepared by NGK insulators (Japan).The great advantage of this zeolite type with respect to the SAPO-34 and T zeolites, should be the chemical and thermal stability because of its all silica structure. Kapteijn and co-workers studied the permeation of various gases (carbon dioxide, nitrous oxide, methane, nitrogen, oxygen. 

Permeation studies of carbon dioxide and oxygen were performed using a sample holder which, has its sides sealed off one from another. The permeate gas being studied was introduced on one side and kept at a constant pressure of 0.10 MPa. On the other side the concentration of the gas was measured using photoacoustic gas analyser. The gas concentration (C), in these conditions, is given by [62] ... 

This system was studied using an aluminum ceramic tube with two Ru layers deposited in the internal surface. The membrane was put in a stainless steel module and fed with an equimolar stream of methane and carbon dioxide. The permeation tests allowed the statement that the transport phenomenon was a kind of combination of Knudsen and Pouiselle mechanisms (Paturzo et al., 2003). The results obtained are shown in Figure 4.9. 

The influence of carbon dioxide on the oxygen permeation of MIEC membranes has been extensively studied compared with the effect of other gases, such as SO2, which can also be present in the gas streams. Of course, CO2 will be the major component of a hypothetical gas mixture where the MIEC membrane should work (e.g., oxy-fuel process). Nevertheless, the influence of SO2 must be mandatorily evaluated and represents one of the biggest concerns in this area. For example, the SO2 concentration in the flux gas can be around 400 ppm or even higher than 1000 ppm, as reported before the scrubber system in some power plants in China [82]. Up to 2011, few reports can be found dealing with membrane operation in SO2 environments. However, on related topics, for example, catalysis, several studies revealed the formation of sulfetes and sulfldes... 

In this work, a series of porous carbon powders is studied using Nitrogen and Carbon Dioxide isotherms at 77 K and 194.5 K, respectively. The pore structure characteristics are deduced and a mechanism of the activation process is proposed. Composite carbon membranes analogues are also studied using both adsorption and permeation techniques. Structural and diffusion characteristics are derived as well as the activation process mechanism of these composite membranes. Finally, the optimum conditions of activation of the membranes are determined. 

For moderate natural gas flows (lower than 25000-30 000 N m containing high carbon dioxide concentrations it appears that membranes are more profitable than absorption processes. In 1995, it was shown that commercial permeation membranes were more competitive than DEA/MDEA-based absorption when the carbon dioxide content was higher than 20%. Another study realized by Kellogs Co. sets this limit at approximately 16% for a gas price of 1.5 USD per MMBtu. 

In fermentation no oxygen is used, so that there is no question as to permeability to oxygen. Glucose, provided in the medium, must permeate the yeast cell before metabolism starts. Metabolism, probably by means of several steps leads to the liberation of carbon dioxide presumably by decarboxylation. To be measured, this carbon dioxide must pass out through the plasma membrane and be freed as a gas from the medium (see Nord and Weichherz, 64). The very great permeability to carbon dioxide of all or most of all the studied types of plasma membrane leads to the conclusion that this step has no measurable influence. The liberation of carbon dioxide from even saturated solutions has been thought to require the use of special methods, such as the addition of large amounts of citric acid as Meyerhof advocates (53). Further study of this step is desirable. 

From the one factor at a time study, both the carbon dioxide and methane permeate flux were found to increase with ... 

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