Consecutive scheme

Following a similar approach, a rate equation in the case of the consecutive scheme can be also derived. 

The kinetics of the toluene oxidation over Bi2Mo06 and a commercial Bi—Mo—P—O ammoxidation catalyst were investigated by Van der Wiele and Van den Berg [348]. A flow reactor was used at 450—550°C, 1—3 atm and varying feed rate, toluene and oxygen partial pressures. Benzaldehyde formation and combustion reactions are the main process the parallel-consecutive scheme which applies is... 

The major part of isomers (> 90%) are formed by an acid mechanism, according to the consecutive scheme odCB mdCB pdCB, as in homogeneous phase (ref.6). However, the small odCB pdCB direct interconversion, and the appearance of CB and TCBs, evidenced a dechlorination/chlorination process initiated on Fe + impurities by a radical mechanism (ref.6). 

The gas phase isomerisation of substituted halobenzenes occurs readily on zeolites. Similarities appear with the same reaction catalyzed by AlClj in the homogeneous phase, in particular the applicability of the Hammett equation. However, several differences stand in the mechanism and the reaction scheme. Part of the transformation of halobenzenes occurs by means of a radical dechlorination/chlorination mechanism. For the same reasons the formal reaction follows a triangular scheme which differs from the consecutive scheme occuring in the liquid phase. Moreover, selectivity can be strongly affected by the restriction to diffusion in the porous volume of the solid. 

Experiments determining temperature dependence of methanol oxidation with hydrogen peroxide were carried out under the same conditions. Figure 4.13 shows methanol conversion and formaldehyde yield (10%) maxima at 590 °C. A further increase of temperature decreases formaldehyde content in the reaction mixture. This testifies to the process proceeding by the consecutive scheme with further transformation of formaldehyde, CO and C02 concentration increasing simultaneously. 

The supposed consecutive scheme of the hydrogenation of benzene to cyclohexane over a Ni containing catalyst is... 

Is it possible, without using nonstationary kinetic experiments, to prove or disprove the validity of this consecutive scheme but not, for example, the consecutive scheme... 

As shown in figures 4 for HFAU30, double bond shift and toluene alkylation occur through consecutive schemes with all the zeohte samples ... 

A parallel-consecutive scheme holds at higher temperatures of 350 to 400°. 

Thus the parallel-consecutive scheme of propene oxidation to acrolein over cuprous oxide was revealed by the kinetic tracer method. 

Chromium sulfide is the active component for the dehydrogenation alumina which possesses desulfurization sites, confers a poor selectivity to the Cr/Al203 catalyst. We can note the very high activity of the Cr/C catalyst. The selectivity to dihydrothiophene (DHT) is always higher at a 50% conversion than at high conversion (80-100%). Results obtained at low conversion [9] confirm this tendency, the selectivity to DHT reaching 15-20% at a 10-20% conversion, in accordance with the consecutive scheme (Eqn.l) proposed for the dehydrogenation. 

This analysis can be used to test a hypothesis about the type of mechanism if more than one intersection of the concentration curves A and B is observed, this implies that the consecutive reaction scheme A B cannot be valid, and a more complex mechanism is needed. If, on the other hand, there is only one intersection, the consecutive scheme is likely and the fact that an intersection is indeed observed directly implies that k2 < 2ki-... 

This analysis, first presented by Yablonsky et al. (2010), can significantly improve our ability to distinguish between different reaction mechanisms. Previously, the observation of a maximum concentration of B in a reaction starting from A and involving B and C was considered to be a sufficient indication for distinguishing the consecutive scheme A —> B —> C from the parallel one, A —B, A C. Now, based on a number of possible types of intersection, we can falsify the assumption of the consecutive scheme (and propose a more complicated alternative) or justify it and deduce certain additional information regarding the rate coefficients. 

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