Carbon dioxide, xxii

Since several cationic carbonyls react with water to give carbon dioxide and a metal hydride (18), it is predicted that Complex XV or XXII should be catalysts for the water gas shift reaction. Preliminary results indicate that this is correct and catalysis occurs slowly at 100°C in aqueous methanol, with the slow step in the catalytic cycle being the reaction of Complex XXII with water to regenerate Complex XV with the evolution of C02. 

The slow step is deduced from the reluctance of Complex XXII to react with water or OH- in model reactions to regenerate XV under mild conditions. This is probably because the single positive charge in Complex XXII is spread over two platinum centers and the carbonyl group is therefore not sufficiently activated towards nucleophilic attack. In contrast the dication [Pt2(CO)2(/i-dppm)2]2+, XIII, reacts readily with water to give XXII and carbon dioxide. 

The SSTAR reactor is coupled to a supercritical carbon dioxide (S-CO2) Brayton cycle power converter. It provides higher cycle efficiency than a helium ideal gas Brayton cycle or a Rankine saturated steam cycle operating at the same core outlet temperature. A key contributor to the high efficiency is the low amount of work (PdV work) to compress S-CO2 immediately above its critical temperature - due to the high S-CO2 density. Table XXII-6 compares the densities of S-CO2 at cycle conditions versus those for helium in the Eskom Pebble Bed Modular Reactor (PBMR) as well as typical liquid coolants the S-CO2 density is more like that of an ordinary liquid. Thus, the S-CO2 temperature and pressure at the low end of the cycle are designed close to but slightly greater than the critical temperature (30.98°C) and pressure (7.373 MPa) to exploit the small PdV work of compression. 

It is these steps which, subject to a distribution of radicals by the partial equilibria (i), (ii), (iii), and (xviii), exercise kinetic control over the rate of final equilibration. In flames which contain carbon monoxide and carbon dioxide in the burnt gas, reaction (xxi) may also be equilibrated, and reactions (xxii) ... 

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