Carbon dioxide behavior

Hydrophobic properties are important for gas transport in the electrode. The decreased hydrophobicity allows the electrolyte to flood more pores, thus hindering the gas transport. 

For the electrochemical characterization, V(i) curves were recorded and an IR correction was used to compensate for the ohmic losses in the measured potential (the ohmic resistance was measured by current interruption). The slope of the V(i) curve (the surface-specific conductivity) was calculated as a characteristic parameter for the electrochemical performance of the anodes and the cathodes. 

Additionally, the CO2 contents of the reaction gases were quantitated by gas chromatography, and the carbonate concentration in the electrolyte was measured after various operating times. 

The carbonate in the alkaline electrolyte forms COj ions that should migrate with the electrical field towards the anode. Therefore, the anodes also need to be investigated to assess the influence of CO2 on AFCs. If carbonates are deposited on the anode, they could block the electrode pores. Hence the pore system and the specific surface area of the nickel anodes were investigated by nitrogen adsorption 

In addition, anodes were investigated by XPS after operation for over 2600 h in the presence of pure hydrogen and in the presence of C02-containing hydrogen. No carbonate deposition could be observed. In addition, SEM measurements were also performed with electrodes operated in the presence of either pure gases or CO2-containing gases. Consistent with the porosimetry and XPS measurements, no eSects of the CO2 were observed by SEM. 

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ME Sigman, SM Lindley, JE Leffler. Supercritical carbon dioxide behavior of Pi and beta solvatochromic indicators in media of different densities. J Am Chem Soc 107 1471, 1985. 

Protonated and diprotonated carbonic acid and carbon dioxide may also have implications in biological carboxylation processes. Although behavior in highly acidic solvent systems cannot be extrapolated to in vivo conditions, related multidentate interactions at enzymatic sites are possible. 

These equations tell us that the reverse process proton transfer from acids to bicarbon ate to form carbon dioxide will be favorable when of the acid exceeds 4 3 X 10 (pK, < 6 4) Among compounds containing carbon hydrogen and oxygen only car boxylic acids are acidic enough to meet this requirement They dissolve m aqueous sodium bicarbonate with the evolution of carbon dioxide This behavior is the basis of a qualitative test for carboxylic acids... 

Phase Behavior. One of the pioneering works detailing the phase behavior of ternary systems of carbon dioxide was presented ia the early 1950s (12) and consists of a compendium of the solubiHties of over 260 compounds ia Hquid (21—26°C) carbon dioxide. This work contains 268 phase diagrams for ternary systems. Although the data reported are for Hquid CO2 at its vapor pressure, they yield a first approximation to solubiHties that may be encountered ia the supercritical region. Various additional sources of data are also available (1,4,7,13). 

Catchpole-Kinp examined binaiy diffusion data of near-critical fluids in the reduced density range of 1 to 2.5 and found that their data correlated with average deviations of 10 percent and a maximum deviation of 60 percent. They observed two classes of behavior. For the first, no correction fac tor was required R = 1). That class was comprised of alcohols as solvents with aromatic or ahphatic solutes, or carbon dioxide as a solvent with ahphatics except ketones as solutes, or... 

Fire Hazards - Flash Point (deg. F) 113 OC Flammable Limits in Air (%) Not pertinent Fire Extinguishing Agents Water, dry chemical, carbon dioxide Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Not pertinent Behavior in Fire May explode. Bums with accelerating intensity Ignition Temperature (deg. F) Explodes Electrical Hazard Data... 

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