Exothermal propylene ammoxidation

The very high exothermal reaction of propylene ammoxidation develops a large amount of heat, in this case 61.5 MW or 15.35 GJ/t. Up to 30% can be exported on site, depending on the technology [21]. For assessing the opportunities for... 

The Sohio process is considered one of the most successful applications of FCB. Problems in industrial application of the reaction arose from the strong exothermicity of propylene ammoxidation and from the intermediate production of acrylonitrile in the consecutive reactions (V9). It is particularly noticeable that the catalyst gives high selectivity, and the reactor design aims at better fluidization and higher contact efficiency than in the FCC process. 

The reaction is highly exothermic and uses volumetric flow ratios, air/CH4/NH3, of about 5/1/1. Whereas propylene ammoxidation proceeds at about 440° C, the ammoxidation of methane requires temperatures... 

Several important aspects of propane ammoxidation reaction chemistry are quite different from that of propylene ammoxidation and have to be taken into account in the development of a commercial operation. One important difference is the higher heat content of propane as compared to propylene, thus making the propane ammoxidation reaction a more exothermic reaction than the propylene ammoxidation reaction (Table 2). Compared to propylene ammoxidation at typical reaction temperatures, approximately 117 kJ more heat is produced for each mole of propane converted. For a commercial process this means that careful attention must be paid to heat management in the reactor. For such a highly exothermic process, a fluid-bed reactor provides better isothermality through more uniform heat distribution and more efficient heat removal than is possible with a fixed-bed reactor. Thus, a commercial propane ammoxidation process will likely use fluid-bed cataljdic technology similar to the current propylene-based process. 

As with other oxidation reactions, ammoxidation of propylene is highly exothermic, so an efficient heat removal system is essential. 

Another industrially important reaction of propylene, related to the one above, is its partial oxidation in the presence of ammonia, resulting in acrylonitrile, H2C=CHCN. This ammoxidation reaction is also catalyzed by mixed metal oxide catalysts, such as bismuth-molybdate or iron antimonate, to which a large number of promoters is added (Fig. 9.19). Being strongly exothermic, ammoxidation is carried out in a fluidized-bed reactor to enable sufficient heat transfer and temperature control (400-500 °C). 

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