Carbon dioxide loss

Likewise, a-methylene-/3-lactones, 280, can serve as allene equivalents since they cycloadd to conjugated dienes to provide the expected [2 + 4] products, e.g. 281 and 282, which on heating fragment with carbon dioxide loss to furnish the allene adduct 279 again [116]. 

Figure 8 shows semilog plots of the carbon dioxide uptake as a function of evaluation time. Such plots show a linear correlation of carbon dioxide loss Avith the log of the time, consistent with a purely difiiisive mechanism for the loss of carbon dioxide. 

Lower temperatures slow the rate of carbon dioxide loss and can leave unburned limestone in the product (Table 7.1). Also, if a moderate particle size rather than finely ground limestone is used to reduce dust carryover in the kiln, additional carbon dioxide partial pressure must be developed in the larger granules to ensure carbon dioxide diffusion to the outside. 

Probably the rotary horizontal kiln is the most versatile, since it allows a feed of lumps or fines of limestone or marble, or wet or dry calcium carbonate sludges (Fig. 7.1). The main component of this calcination system is a 2.5- to 3.5-m diameter by 45- to 130-m long firebrick-lined inclined steel tube. Heat is applied to the lower end of this via oil, gas, or coal burners [7]. The feed to be calcined is fed in at the top end. Slow rotation of the tube on its axis gradually moves the feed down the tube, as it tumbles countercurrent to the hot combustion gases. In this way, wet feed is dried in the first few meters of travel. Further down the tube, carbon dioxide loss begins as the temperature of the feed rises. By the time the solid charge reaches the lower, fired end of the kiln it reaches temperatures of 900-1,000°C and carbon dioxide evolution is virtually complete. Normally the temperature of the lower end of the kiln is not allowed to go much above this as it reduces the life of the kiln lining. It also adversely affects the crystal structure of the lime product since it produces a dead-burned or overburned lime. Overburned lime is difficult to slake to convert it to calcium hydroxide and raises... 

The success of this process depends on the low solubility of calcium carbonate, which is also what allows this process to be used for small-scale production of sodium hydroxide by a batch process. For batch operation, the functions such as slaking, mixing, and settling may be carried out in the same wooden (or steel) vessel. Separate units are required for these steps in the continuous process. A further chemical feature important to the recycle of the spent lime of this process is the relatively easier thermal loss of carbon dioxide from calcium carbonate than from sodium carbonate. Since sodium bicarbonate (NaFICOs) may be calcined at 175°C to obtain carbon dioxide loss, it might be expected that sodium hydroxide could be made by heating sodium carbonate at a higher temperature followed by hydration of the resulting oxide (Eqs. 7.21 and 7.22). 

The slagging reactions (Eqs. 14.1-14.3) start to occur as the charge moves down the furnace and the limestone or dolomite flux reaches temperatures of about 900°C or more. As carbon dioxide loss occurs, the lime (and magnesia, if present) starts to react with and dissolve other oxide impurities of the charge into the slag layer. It is also possible to reduce silica and phosphate by the same kinds of reactions used to reduce iron which, in the process, contaminates the pig iron (Eqs. 14.13 and 14.14). 

The 1,5,2,4-dioxazadiazinedione system (35) has been prepared. However, these compounds decompose very readily. Thermal decomposition leads to carbon dioxide loss with the formation of isocyanates and nitrosoalkanes (Equation (1)). The compounds are stable to water, but are attacked by organic soluble nucleophiles, and reagents such as phenylmagnesium bromide, to yield products which arise from attack of the nucleophile at the carbonate carbonyl, followed by fragmentation (Equation (1)). Catalytic reduction of (35) leads to ureas <86JOC3355>. 

Methods must be devised for assessing carbon dioxide losses during transfer operations and also the leakage rates from each type of store. Several techniques are available or under development but these vary in applicability, site specificity and detection limits. The formulation of protocols for monitoring the hazards associated with carbon dioxide capture and transfer does not appear to present fundamentally new challenges, as similar protocols are part of standard environmental health and safety practices for toxic gases. 

A bond formed as a result of sharing electrons A reaction leading to the formation of a ring An addition reaction that forms a ring A substituent that decreases the reactivity of an aromatic ring to electrophilic substitution Loss of carbon dioxide Loss of water... 

Carbon dioxide, loss of, in intramolecular Diels-Alder 15, 19... 

Many studies have shown that the peak intensity of the carboxylate anion resulted from the sn-2 FA chain is approximately three times more intense than that arising from the sn-l FA chain of dPC species [17, 22, 29, 30]. This fact has been used to identify the location of fatty acyls and thus regioisomers of dPC species. However, this ratio becomes smaller than three if the sn-2 FA chain is a polyunsaturated FA substituent [22]. It is now clear that this reduced ratio is due to the fact that the resultant polyunsaturated FA carboxylate anion can go further fragmentation to yield an ion corresponding to the neutral loss of carbon dioxide (i.e., [carboxylate anion-44] ) [31-33]. This continuous loss of carbon dioxide has recently been exploited to identify the location of double bond(s) of fatty acyls [33]. With the recognition of carbon dioxide loss, the combined ion intensity of the carboxylate anion and [carboxylate anion-44] ion arising from sn-2 polyunsaturated FA chain is still approximately three times more intense than that of the sn-l FA carboxylate ion [32]. 

Rate constants and activation parameters are also given for loss of carbon dioxide from the intermediate d5-[Rh(en)2(C03H)(OH2)]. Here the rhodium(III) system has two advantages over its cobalt(III) counterpart, for not only is it possible to obtain kinetic data for the monodentate bicarbonato intermediate but also there is no concomitant isomerization to complicate the carbon dioxide loss kinetics in the rhodium(III) case. In the reverse direction, kinetic parameters were obtained for the reaction of c/5-[Rh(en)2(OH2)(OH)] and of d5-[Rh(en)2(OH)2] with carbon dioxide-(bi)carbonate. The products are cw-[Rh(en)2(C03)(0H2)] and d5-[Rh(en)2(C03)(0H)] there is no mention of a bidentate carbonato product. Kinetics of decarboxylation of the new complexes trans-[Rh(en)2(C03)(0H2)] and rra 5-[Rh(en)2(C03)2]" have been reported, with values for rate constants and activation parameters given. The bis(carbonato) complex loses both carbonate ligands at low pHs, but only one carbonate when pH > 6.5. The kinetics of the reverse carbonate-formation reactions, from trans-... 

The point at which concrete loses its integrity varies with the type of concrete, but generally occurs well before the carbon dioxide is released. Typical concrete contains about 4 to 9 weight percent water and 0 to 45 weight percent carbon dioxide. Loss of structural integrity is particularly important when considering the possible impact of CCIs upon vessel supports in BWRs. 

The catalysts include Be +, Co +, Ni +, Cu +, Zn +, Al +, Y +, La +, Gd +, and Lu +. The reaction mechanism proposed is the fast formation of a 1 1 complex followed by rate-determining loss of carbon dioxide from this complex. The cations thus affect the rate of loss of carbon dioxide in two ways, through the value of the pre-equilibrium complex-formation constant and through the consequences of their electron-withdrawing effect on the actual rate of carbon dioxide loss from the complex. The activation enthalpy is actually higher for the cation-catalysed reaction than for that of free oxaloacetic acid - the observed greater rates in the presence of the cations arise from a large, favourable TA5 difference. There is a LH vs. AS" correlation for all these cation-catalysed reactions. ... 

In breweries, for example, hermetic centrifuges can be used for pre-clarification of beer ready for packing, with no carbon dioxide losses and no destruction of protein for the clarification of the cold wort, with a good clarification efficiency because protein particles are not destroyed. In dairies, hermetic centrifuges are used because milk is sensitive to both oxidation and shear. 

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