Carbon dioxide, formation

Temperature, pH, and feed rate are often measured and controlled. Dissolved oxygen (DO) can be controlled using aeration, agitation, pressure, and/or feed rate. Oxygen consumption and carbon dioxide formation can be measured in the outgoing air to provide insight into the metaboHc status of the microorganism. No rehable on-line measurement exists for biomass, substrate, or products. Most optimization is based on empirical methods simulation of quantitative models may provide more efficient optimization of fermentation. 

The per pass ethylene conversion in the primary reactors is maintained at 20—30% in order to ensure catalyst selectivities of 70—80%. Vapor-phase oxidation inhibitors such as ethylene dichloride or vinyl chloride or other halogenated compounds are added to the inlet of the reactors in ppm concentrations to retard carbon dioxide formation (107,120,121). The process stream exiting the reactor may contain 1—3 mol % ethylene oxide. This hot effluent gas is then cooled ia a shell-and-tube heat exchanger to around 35—40°C by usiag the cold recycle reactor feed stream gas from the primary absorber. The cooled cmde product gas is then compressed ia a centrifugal blower before entering the primary absorber. 

Immiscible-phase separation Transformation Processes No Fluids (such as gasoline) that are immiscible in water are a significant consideration in near-surface contamination. Deep-well injection is limited to wastestreams that are soluble in water. Well blowout from gaseous carbon dioxide formation is an example of this process that is distinct to the deep-well environment. 

Unopened bottles of this, all originating from the same batch and well within the manufacturer s expiry date, exploded while warming to room temperature. This was attributed to water contamination leading to hydrolysis and carbon dioxide formation, without supporting evidence—a number of other contaminants, both nucleophiles and acids, might catalyse carbon dioxide formation (Editor). 

The effect of microwave irradiation on the catalytic properties of a silver catalyst (Ag/Al203) in ethane epoxidation was studied by Klimov et al. [91]. It was found that on catalyst previously reduced with hydrogen the rates of both epoxidation and carbon dioxide formation increased considerably on exposure to a microwave field. This effect gradually decreased or even disappeared as the catalyst attained the steady state. It was suggested that this was very likely because of modification of electronic properties of the catalyst exposed to microwave irradiation. 

Again the close correspondence between the measured radical and carbon dioxide yields for 7-radiolysis of the N-acetyl amino acids in the solid state suggests that the mechanisms for radical production and carbon dioxide formation are closely related, as they were for the aliphatic carboxylic acids. The following mechanism has been proposed (5.) in order to account for the major degradation products and observed radical intermediates. 

Anode In aqueous anolytes, under conditions which favor the oxygen evolution, carbon is attacked under carbon dioxide formation, this is increasingly encountered with more porous materials. Glassy carbon will be relatively stable. A low pH value may retard the oxygen reaction, but carbon remains a problematic anode material in aqueous solutions. Additionally, it can be attacked because of intercalation of anions. 

Biological. Incubation of [ C]A/V-dimethylformamide (0.1-100 pg/L) in natural seawater resulted in the compound mineralizing to carbon dioxide. The rate of carbon dioxide formation was inversely proportional to the initial concentration (Ursin, 1985). 

Incubation of diuron in soils releases carbon dioxide (Madhun and Freed, 1987). The rate of carbon dioxide formation nearly tripled when the soil temperature was increased from 25 to 35 °C. Reported half-lives in an Adkins loamy sand are 705, 414, and 225 d at 25, 30, and 35 °C, respectively. However, in a Semiahoo mucky peat, the half-lives were considerable higher 3,991, 2,164, and 1,165 d at 25, 30, and 35 °C, respectively (Madhun and Freed, 1987). Under aerobic conditions, biologically active, organic-rich, diuron-treated pond sediment (40 pg/mL) converted diuron exclusively to CPDU (Attaway et al., 1982, 1982a Stepp et al., 1985). At 25 and 30 °C, 90% degradation was observed after 55 and 17 d, respectively (Attaway, 1982a). 

Wolfe has presented an excellent description of the systematic application of stable and radioactive isotope tracers in determining the kinetics of substrate oxidation, carbon dioxide formation (including C02 breath tests), glucose oxidation, and fat oxidation in normal and diseased states. Quantification of the rate and extent of substrate oxidation can be achieved by using a specific or C-substrate which upon oxidation releases radioactive carbon dioxide. 

The reaction is shown as reversible because calculations of the thermodynamics show the release of free energy to be only —7.1 to —2.6 kcal/ mole (4, 77). The actual reversibility of the reaction with this enzyme has not been shown. The activity is generally measured as carbon dioxide formation in a respirometer in the presence of L-malic acid and the cofactors. Lonvaud and Ribereau-Gayon (78) have simplified the method with the use of a carbon dioxide specific electrode. 

The selectivity of ethylene oxidation was found to be independent of feed composition at zero conversion. This was interpreted to mean that each of the two parallel processes is initiated by a similar type of transformation. Selectivity at zero conversion appeared to approach, a value considerably different from 100%. Therefore the Initial rate of carbon dioxide formation does not approach zero, as it should if it has to arise exclusively from ethylene oxide. The initial rate of ethylene oxide oxidation was found to depend on the partial pressure of both ethylene oxide and oxygen. Orzechoweki and Mac-Cormack concluded from this, in conflict with Twigg s earlier proposal,1771 that isomerization of ethylene oxide to acetaldehyde ie not a significant step in its further oxidation, Ethylene oxide could undergo oxidation either on the catalyst surface or in the gas phase by ooffision with an adsorbed oxygen atom.127 ... 

Christie et al. (45) and Pendleton and Taylor (46) have recently reported the results of propylene oxidation over bismuth molybdate and mixed oxides of tin and antimony and of uranium and antimony in the presence of gas-phase oxygen-18. Their work indicated that for each catalyst, the lattice was the only direct source of the oxygen in acrolein and that lattice and/or gas-phase oxygen is used in carbon dioxide formation. The oxygen anion mobility appeared to be greater in the bismuth molybdate catalyst than in the other two. 

Thus, when corrected for the small degree to which carbon dioxide is hydrated, it can be seen that carbonic acid is actually a stronger acid than acetic acid. Carboxylic acids dissolve in sodium bicarbonate solution because the equilibrium that leads to carbon dioxide formation is favorable, not because carboxylic acids are stronger acids than carbonic acid. 

The steam-methane reforming process involves the reaction of steam and natural gas (methane) to produce hydrogen and carbon monoxide although there may also be some carbon dioxide formation in the process ... 

All of these complexes decompose cleanly at low temperature to produce acetonitrile, carbon dioxide, and initially, the metal hydroxide (equation 45). The decomposition temperatures are 144,176, and 198 °C for Ba, Cu, and Y, respectively. In the case of copper and yttrium, the final product is the metal oxide produced by the dehydration of the hydroxide, while barium hydroxide recombines with carbon dioxide to yield the carbonate. Barium carbonate formation can be avoided, however, by use of a different ligand that avoids carbon dioxide formation. Benzoin a-oxime (Hbo) (13) has been found to be a quite suitable diprotic ligand for this purpose. The barium salt is easily prepared by reaction of the oxime with the metal dihydride (equation 46), and it decomposes cleanly to barium oxide by loss of benzaldehyde and benzonitrile at 250 °C (equation 47). 

Rates were followed by carbon dioxide formation manometrically and good mass balances (OLC analysis) were demonstrated. 

The oxidation of 2 mol butyric acid to 4 mol acetic acid is coupled with the reduction of 1 mol of carbon dioxide to methane. Tracer experiments showed that 98% of the methane is derived from carbon dioxide. In these examples of methane fermentation involving carbon dioxide reduction, no carbon dioxide is formed in the oxidation of the substrate. The fermentation of propionic acid by M. propionicum is more complicated because it involves both carbon dioxide formation and consumption (Stadtman and Barker, 1951) ... 

---