Cofeed mode

The formation of carbon oxides is usually attributed to non-selective oxygen i.e. O2, 02(ads), 0 , O [2] present when the reaction mixture contains both the hydrocarbon to be oxidized and oxygen ( COFEED mode ), Therefore the application of a CBR reactor fed with propane in the reaction zone (riser) and with oxygen in the regeneration zone (fluidized bed), should improve the selectivity to propene ( REDOX mode ) Other advantages of CBR are discussed elsewhere [3]... 

In this chapter a specific type of membrane reactor, the so-called distributor was analyzed theoretically. In contrast to conventional tubular fixed-bed reactors (FBR), where all reactants are introduced together at the reactor inlet (cofeed mode), packed-bed membrane reactors (PBMR) allow dosing of one or several reactants via membranes over the reactor wall along the axial coordinate (distributed-feed mode). 

As pointed out in Section 1, research and development work on the catalytic OCM reaction is mainly carried out in the "cofeed" mode although a significant amount of development work has been also accomplished in the "redox" mode by ARCO. It appears, however, that work at ARCO has been terminated. For both types of processing catalytic fixed-bed and fluidized-bed reactors have been applied in bench-scale and mini-pilot-plant studies. Steep axial and radial... 

The status and fiitine trends in the development and application of novel reactors equipped with solid electrolyte based membrane materials was analyzed in a review article [105]. BaCo Fe Zr Oj perovskite hollow-fiber membrane reactor was used with permeable and passivated surface segments to enable controlled oxygen insertion into the reactor. The reduced oxygen concentration offered higher ethene selectivity. At low and moderate ethane conversion, the performance of the membrane reactor was on par with the best catalysts used in cofeed mode. The ethene yield was comparable with that of the industrial steam cracking process. However, the reaction temperature was 100°C lower [106],... 

The adsorption of iron(O) pentacarbonyl was recently studied on a Si(lll)-(7 x 7) surface. The interest in Fe(CO)5 lies in its availability as a source gas for the chemical vapor deposition of FeSi2, a critical microelectronics material. Even at temperatures as low as lOOK, Fe(CO)5 already underwent dissociative adsorption to yield a linear iron monocarbonyl (FeCO) surface complex. The prominent loss peaks that appeared at 53meV (428 cm ), 81meV (653 cm ), and 255 meV (2056 cm ) were assigned to the Si-COFe, Fe-CO, and C=0 stretch modes, respectively. These peaks were shown to arise only via dipole scattering which, because of the dipole selection rule, indicates that the adsorbed FeCO is oriented vertically with the CO moiety bonded to the Si surface. 

It is interesting to compare the behavior of a catalyst working in the COFEED and in the REDOX modes. Are the advantages for the selectivity of the absence of gas (adsorbed) oxygen real i ... 

Depending on the mode of feeding of methane and oxidant, different catalytic materials are applied. When the OCM reaction is performed with cofed CH4 and O2, nonreducible metal oxides show higher C2 selectivity than reducible metal oxides. Promoting with alkaline earth and alkali metal oxides significantly enhances the selectivity to C2 hydrocarbons of reducible and nonreducible metal oxides [8,10-12]. Very recently, Ivanov et al. [22] demonstrated that MgO and SrO formed under reaction conditions and stabilized on the surface of Mg-, A1-,... 

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