Dissociation carbonate

Carbon dioxide-water systems play an important role in controlling the pH of alkaline and calcareous soils as well as adjusting solubility of most trace elements and their compounds. Carbon dioxide dissolves in water to form dissolved C02 and dissociated carbonic acid, H2CO30 ... 

The basicity of the molten carbonate is defined as equal to -log (activity of O ) or -log aM20, where a is the activity of the alkali metal oxide M2O. Based on this definition, acidic oxides are associated with carbonates (e g., K2CO3) that do not dissociate to M2O, and basic oxides are formed with highly dissociated carbonate salts (e.g., U2CO3). The solubility of NiO in binary carbonate melts shows a clear dependence on the acidity/basicity of the melt (18,19). In relatively acidic melts, NiO dissolution can be expressed by... 

Most Group VIII metals adsorb carbon monoxide dissociatively, and, consequently, they are good Fischer-Tropsch catalysts.240 In contrast, Pd, Pt, Ir, and Cu do not dissociate carbon monoxide. Of these metals, copper and more recently palladium were found to be excellent methanol-forming catalysts. 

Evidence was presented that cobalt precursors under the reaction conditions are transformed into cobalt carbonyls.31 Additives such as Lewis bases accelerate the formation of the catalyst.11 [CoH(CO)4] the key catalytic species was shown by infrared (IR) spectroscopy to be formed under hydroformylation conditions32 and was isolated in the reaction of [Co(CO)4]2 and hydrogen.33 [CoH(CO)4] dissociates carbon monoxide to create [CoH(CO)3] [Eq. (7.2)], which is capable of olefin com-plexation because of a ligand vacancy ... 

Environmental concerns of lime kiln operation chiefly relate to exhaust gas dust control and are usually solved by water scrubbing. The slaked lime (calcium hydroxide) produced by the scrubber can be employed as a base in the operations of a chemical complex, or sold. Electrostatic precipitation of precooled gases is also used, sometimes in series with water scrubbing. The dissociated carbon dioxide discharged is not ordinarily regarded as a pollutant. The amount discharged from this source is far less than the carbon dioxide produced by fossil fuel combustion. Lime kilns associated with Solvay ammonia-soda plants may be able to recycle a part of the dissociated carbon dioxide, particularly if the concentrations are raised by the use of oxygen-enriched combustion air. Recently, interest has been shown... 

Weakly dissociated carbonic acid is formed from the strongly conducting sodium bicarbonate by exchanging the eluent sodium ions with the protons of the cation exchanger ... 

As the result of the suppressor reaction, strongly conducting mineral acids in the presence of weakly dissociated carbonic acid enter the conductivity cell and are thus easily be detected. 

Guczi and coworkers [4.61] studied CO chemisorption on glassy and crystalline FeNiB alloys in the presence and in the absence of hydrogen using XPS and UPS. They found that CO chemisorption at 300 K is characteristic of the surface structure. At S70 K, no difference could be observed in the mode of chemisorption because only dissociative carbon was present. However, the reactivity differences observed in the CO + H2 reaction could be ascribed to the difference in the surface transformation of the carbidic species. The authors suggested that this species can be stabilized by the small ensemble size characteristic for glassy and partially crystallized samples, whereas the main route of the dissociative carbon on crystallized samples is the inactive bulk carbide formation. This phenomenon was found to be influenced by the alloy composition and by the presence of hydrogen. 

The transformation of a radical-cation into a radical involves processes such as carbon-hydrogen dissociation, carbon-metal bond dissociation, carbon-carbon bond dissociation (this latter process is not frequently encountered and will not be treated in this review) and nucleophilic addition. 

In chemical reactions usually only CO2 or H2CO3 is written, but it always expresses the total quantity of dissolved CO2 in the form of both hydrated CO2 and non-dissociated carbonic acid. 

While the hydrogenation of the active surface carbon that forms from CO dissociation appears to be the predominant mechanism of CH4 formation, it is not the only mechanism that produces methane. Poutsma et al. [85] have detected the formation of CH4 over paliadium surfaces that do not readily dissociate carbon monoxide. They also observed methane formation over nickel surfaces at 300 K under conditions in which only molecular carbon m.onoxide appears to be present on the catalyst surfaces [81]. Vannice [86] also reported the formation of methane over platinurh, palladium, and iridium surfaces, and independent experiments indicate the absence of carbon monoxide dissociation over these transition-metal catalysts in most cases. It appears that the direct hydrogenation of molecular carbon monoxide can also occur but that this reaction has a much lower rate than methane formation via the hydrogenation of the active carbon that is produced from the dissociation of carbon monoxide in the appropriate temperature range. 

It should be noted that both the surface temperature and the pressure are important variables in this reaction that should be studied independently. Much of the carbon monoxide adsorbed on the catalyst surface at 300 K remain molecular while dissociation commences as the temperature is increased. By changing the surface temperature, one can control the ratio of molecular and dissociated carbon monoxide on the surface. Thus, low temperature studies are likely to lead to the formation of higher-molecular-weight hydrocarbons if molecular CO is necessary for the... 

The TPD of CO from supported Co catalysts is a complicated process involving other reactions such as CO dissociation and CO disproportionation. It is referred that the low temperature peak of CO2 desorption resulted from CO disproportionation [18], and the higher temperature peaks from the recombination of dissociated carbon and oxygen. For Co/A.C. and Pd promoted Co/A.C., the CO2 desorption peak located at higher temperature than that of Ru and Pt promoted Co/A.C. and the temperature of CO2 desorption peak was the lowest for Ru promoted Co/A.C.. It seems that CO2 formed on Ru promoted Co/A.C. was mainly attributed to the CO disproportionation, indicating that this catalyst was inactive to decompose adsorbed CO to form dissociated carbon and oxygen band, consequently improving the CO insert reaction in hydroformylation reaction of 1-hexene. 

Pt promoted Co/A.C., which located at 466 K, unlike that of Co/A.C. and lwt% Pd promoted Co/A.C. catalysts. The desorbed CO/CH4 ratio in TPSR was 0.77, 0.81, 1.12 and 0.94 for Co/A.C., Pd, Ru and Pt promoted Co/A.C. catalyst, respectively. These facts suggested that CO was adsorbed in a more inactive state on the Ru promoted Co/A.C. catalyst than on the others, which was difficult to be dissociated and reacted with hydrogen to form CH4 in TPSR. Based on above, the Ru promoted Co/A.C. had the lowest CO cleavage activity and was inactive for dissociating carbon and oxygen bond of adsorbed CO, due to its smallest particle size as compared in Table 3. This feature is very advantageous to CO molecular reactions, contributing to the CO insert reaction in hydroformylation of 1-hexene. 

Strongly conducting sodium bicarbonate is converted to weakly dissociated carbonic acid by exchanging sodiiun ions of the eluent with hydroniiun ions of the cation exchanger ... 

To turn to the other extreme, numerous examples are known of heterosubstituted organometallics that spontaneously undergo -elimination. Although they obey an Elcb pattern, we again face an ambiguity. Normally the metal actively participates in the elimination process. Free carbanions are involved only in the rare cases of dissociated carbon-metal bonds (as in triphenylmethyl- or fluorenyllithiums if adequately solvated). 

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