Partial oxidation Reaction conditions

Thermodynamically, the oxidation of hydrocarbons to carbon dioxide and water is preferred to any partial oxidation reaction. The possibility of forming partial oxidation products is thus entirely dependent on the kinetics of the oxidation process. The oxidation of hydrocarbons, is in general, a stepwise process. One way to confine the depth of oxidation, therefore, is to apply a low oxygen to hydrocarbon ratio and a short reaction time. However, to avoid a multitude of products with different oxidation depths, the use of a catalyst is obviously required. In that case, the above two factors (oxygen deficient conditions and short reaction time) may loose their importance. 

Oxidative coupling of isobutene suffers from severe deep oxidation. As in many other partial oxidation reactions selectivity remains low, despite intensive optimization of catalysts and reaction conditions. Among various new reactor concepts, the separation of catalyst reduction and reoxidation is very promising (two step process). Reaction engineering investigations of the two step process have been done. The influence of reaction conditions and reversibility of reduction/reoxidation cycles have been investigated. Based on the reaction engineering results a first approach to a kinetic model of both reaction steps has been developed. 

The vanadium pentoxide cataKtic membrane reactor was prepared by coating its sol inside the Vycor tube membrane. After heat treatment of the prepared membrane, the [010] planes of vanadium pentoxide layer were grown largely which contributes to partial oxidation reaction of 1-butene to maleic anhydride. The partial oxidation of 1-butene to maleic anhydride was carried out in the catalytic membrane reactor. The maximum selectivity of 95% was obtained at 350 °C when the surface velocity was 500cm/h. And at this condition, oxygen permeability was almost four times higher than the reaction had not occured. 

This model accounts for fuel atomization and vaporization, partial oxidation, steam reforming, and anode exhaust combustion. It is asumed that the partial oxidation reaction is very fast and occurs at the top of the catalyst bed along with fuel atomization and vaporization. It is also assumed that the steam reforming initiates after all O2 is consumed in the partial oxidation reaction. Therefore, the reactor will initially be considered as two plug-flow reactors in series. Figure 2 and 3 depict the inlet conditions for the ATR model and results from the model, respectively. 

A comparison of the intrinsic activity of all fifteen catalyst formulations, tested under CO oxidation reaction conditions, is given in the bar diagram of Fig.3 which shows the maximum measured turnover numbers at 227°C and oxygen partial pressure of 2.6 kPa. Rhodium is clearly a far superior CO oxidation catalyst as compared to Pt and Pd, in accordance with results of other investigators [21], It is also observed in Fig. 3 that the activity of Rh for CO oxidation is very sensitive to the carrier employed for its dispersion. A weaker sensitivity is exhibited by Pd and Pt. 

A very important issue is the adsorption and dissociation of O2 on the Au/oxide systems since this seems to be a necessary step in total and partial oxidation reactions. " Can isolated Au nanoparticles dissociate O2 Is the Au/oxide interface necessary for the cleavage of 0-0 bonds Calculations based on density functional theory have been carried out for a series of unsupported Au nanoparticles as well as for extended systems containing low-coordinated sites. Strong adsorption of molecular oxygen on Au nanoparticles is a necessary but not sufficient condition for O2 dissociation. For reasonably large Au cubo-octahedral nanoparticles, there is a common pathway for O2 dissociation on nanoparticles which involves a particular configuration of adsorption sites and a critical particle size. If these conditions are not satisfied, the... 

In catalytic partial oxidation (CPO) the chemical conversions take place in a catalytic reactor without a burner. In all cases of partial oxidation, some or all of the reactions listed in Table 1.7 are involved. The partial oxidation reactions are accompanied by the steam reforming and shift reactions (Table 1.2). The oxidation reactions are irreversible under all conditions of practical interest. 

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