Carbon monoxide equilibrium concentration

Such burner units with a closed 3D matrix make it possible to significantly extend the limits of stable combustion of rich mixtures (Fig. 12.12). The possibility of stable conversion in a 3D porous matrix of very rich methane—air mixtures at values a < 0.4 and a temperature of 1000 °C to hydrogen and carbon monoxide in concentrations close to the thermodynamically equilibrium values was demonstrated in [331—332]. 

The carbon monoxide concentration contours for 50 atm and 700 °K (Figure 9) indicate that the equilibrium CO leakage will not be high if equilibrium is reached when the initial composition is near the stoichiometric line. 

The space velocity was varied from 2539 to 9130 scf/hr ft3 catalyst. Carbon monoxide and ethane were at equilibrium conversion at all space velocities however, some carbon dioxide breakthrough was noticed at the higher space velocities. A bed of activated carbon and zinc oxide at 149 °C reduced the sulfur content of the feed gas from about 2 ppm to less than 0.1 ppm in order to avoid catalyst deactivation by sulfur poisoning. Subsequent tests have indicated that the catalyst is equally effective for feed gases containing up to 1 mole % benzene and 0.5 ppm sulfur (5). These are the maximum concentrations of impurities that can be present in methanation section feed gases. 

A catalyst used for the u-regioselective hydroformylation of internal olefins has to combine a set of properties, which include high olefin isomerization activity, see reaction b in Scheme 1 outlined for 4-octene. Thus the olefin migratory insertion step into the rhodium hydride bond must be highly reversible, a feature which is undesired in the hydroformylation of 1-alkenes. Additionally, p-hydride elimination should be favoured over migratory insertion of carbon monoxide of the secondary alkyl rhodium, otherwise Ao-aldehydes are formed (reactions a, c). Then, the fast regioselective terminal hydroformylation of the 1-olefin present in a low equilibrium concentration only, will lead to enhanced formation of n-aldehyde (reaction d) as result of a dynamic kinetic control. 

Ca2 is given by the equilibrium A2/A1, with the equilibrium constant K 2ai = Ca2/(Cai Cco). Substituting the carbon monoxide concentration by the partial pressure and applying Eq. 1 yields... 

The high yields on the lean side of stoichiometric pose a dilemma. It is desirable to operate lean to reduce hydrocarbon and carbon monoxide emissions but with fuel containing bound nitrogen, high NO yields would be obtained. The reason for the superequilibrium yields is that the reactions leading to the reduction of NO to its equilibrium concentration, namely,... 

If the three gases in the reaction were at equilibrium and you then increased the carbon monoxide concentration, some Bt2 would combine with added CO to produce COBr2 and thereby minimize the increase in CO. Alternatively, if you decrease the CO concentration, some COBtj would decompose to produce CO and Br2 and thereby minimize any decrease in CO. Notice how the concentrations of all constituents shift to counteract the imposed change in a single substance. Of course, this shift does not affect the value of the equilibrium constant. Only a change in temperature can do that. 

Equilibrium constants for the gas-carbon and associated reactions (1) to (7), listed in the previous section, are presented in Table I. The individual concentrations of the species in the equilibrium constants are expressed as partial pressures in atmospheres. From the data (see ref. 2), it is evident that the oxidation of carbon to carbon monoxide and carbon dioxide is not restricted significantly by equilibrium considerations at temperatures even up to 4000 K. 

The number of receptor sites and the position of the equilibrium (Eq. 1) as reflected in KT, will clearly influence the nature of the dose response, although the curve will always be of the familiar sigmoid type (Fig. 2.4). If the equilibrium lies far to the right (Eq. 1), the initial part of the curve may be short and steep. Thus, the shape of the dose-response curve depends on the type of toxic effect measured and the mechanism underlying it. For example, as already mentioned, cyanide binds very strongly to cytochrome a3 and curtails the function of the electron transport chain in the mitochondria and hence stops cellular respiration. As this is a function vital to the life of the cell, the dose-response curve for lethality is very steep for cyanide. The intensity of the response may also depend on the number of receptors available. In some cases, a proportion of receptors may have to be occupied before a response occurs. Thus, there is a threshold for toxicity. With carbon monoxide, for example, there are no toxic effects below a carboxyhemoglobin concentration of about 20%, although there may be... 

Therefore, when Pco = 1/220 XP02 the hemoglobin in the blood will be 50% saturated with carbon monoxide. Since air contains 21% oxygen, approximately 0.1% carbon monoxide will give this level of saturation. Hence, carbon monoxide is potentially very poisonous at low concentrations. The rate at which the arterial blood concentration of carbon monoxide reaches an equilibrium with the alveolar concentration will depend on other factors such as exercise and the efficiency of the lungs. Other factors will also affect the course of the poisoning. 

An industrial process to produce methanol from carbon monoxide and hydrogen was developed by BASF in 1923 using a zinc oxide-chromia catalyst.361 362 Since this catalyst exhibited relatively low specific activity, high temperature was required. The low equilibrium methanol concentration at this high temperature was compensated by using high pressures. This so-called high-pressure process was operated typically at 200 atm and 350°C. The development of the process and early results on methanol synthesis were reviewed by Natta 363... 

The values predicted by the equilibrium calculations can be compared with exhaust concentrations observed in practical combustion systems. The major species (i.e., CO2, H2O, and O2) are well predicted by thermal equilibrium. In most of the temperature range covered in the figure, the fuel is fully oxidized. The fast chemistry assumption would also be sufficient to predict the exhaust concentrations of these species. The problem arises if the chemical equilibrium assumption is also used to estimate the concentration level of minor species, such as carbon monoxide, nitrogen oxides, and sulfur oxides. 

According to equilibrium calculations, CO and NO are only important at high temperatures. As the temperature decreases, CO and NO are converted to CO2 and N2, respectively, and the exhaust concentrations are estimated to be below 1 ppm. Furthermore equilibrium calculations indicate that any NO in the exhaust will be present as NO2, and not NO. Comparison with values observed in combustion exhaust shows that neither CO nor NO is in equilibrium. Carbon monoxide emissions range from 10 ppm to 1%, depending on the fuel and the combustion technique. For nitrogen oxides, emissions can be significant from combustion systems and most (about 95%) of the NO emitted is in the form of NO, not N02. 

Finally, palladium dispersion was found to decrease asymptotically from 9% (1 wt.% palladium content) to 0.5% (20 wt.% palladium content). The effect of carbon monoxide concentrations exceeding the equilibrium values of the water-gas shift reaction was studied in depth. With increasing time on-stream and deactivation of the catalyst (containing 1% palladium), the carbon monoxide concentration exceeded the equilibrium up to 18-fold. Even higher values were found for lower reaction temperatures. 

One treatment for carbon monoxide poisoning is administration of oxygen. The high concentration of oxygen binds to free hemoglobin, including the Hb from the equilibrium between Hb and CO. This is an application of ... 

Finally, the presence of the solid-phase sorbent material improves the equilibrium of Reactions (7) and (8). By removing carbon dioxide from the products of the steam reforming process, equilibrium is shifted toward greater hydrogen production, reduced carbon monoxide and carbon dioxide concentrations, and increased fuel conversion. 

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