Ammonia fixed mass ratio

The initial alcohol/amine ratio can determine the product distribution. In the synthesis of primary amines a rather high ammonia/alcohol molar ratio (up to 10-25), and usually high pressure, are required to compensate for the low reactivity of ammonia and suppress the formation of secondary amines. Selectivity for primary diamines could be improved in the amination of 1,3-dihydroxy compounds when using supercritical ammonia as solvent and reactant in a continuous fixed-bed reactor [12]. The remarkable changes in selectivity in the near-critical region (100-110 bar) are attributed to the increased concentration of ammonia on the metal surface as a result of elimination of mass-transport limitations in the two-phase system, and to suppression of hydrogenolysis and water elimination reactions which lead to monofunctional by-products. An example is shown in Figure 1. 

Colombo et al. [48] performed a simulation study of the de-NOj activity effect on soot regeneration. Simulations were carried out at a fixed temperature of 500 °C and with a feed mixture containing equal amounts of ammonia and NOj. The initial soot load was set to 8 g/1 and simulations were repeated with two different NO2/NO , ratios, namely 0 and 1. For both reacting systems, simulations were first performed considering the SCR reactivity and then repeated by deactivating the de-NO reactions. The computed evolution of the total soot mass and of wall soot was followed as a function of time, as shown in Fig. 13.16. 

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