Effect of the hydrogen pressure on the kinetics of the liquid-phase catalytic hydrogenation of aromatic nitro compounds
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The relation between the rate of liquid-phase nitro compound hydrogenation and the hydrogen pressure is complex. Over the pressure range from 0.1 to 0.9 MPa, the concentration of the initial nitro product varies in direct proportion to the hydrogen pressure, and this despite the fact that the rate of conversion of the intermediate phenylhydroxylamine into the amino product is unaffected by an alteration in the pressure. This supports the suggestion that the catalytic hydrogenation of nitro compounds proceeds through disproportionation, rather than reduction, of the phenylhydroxylamines.
The possibility of increasing the selectivity of the hydrogenation reaction for pchlorohydroxylamine formation is discussed, and it is shown that the yield of this product can be increased markedly by working at high pressure and low temperature.
KeywordsHydrogenation High Pressure Pressure Range Disproportionation Hydrogen Pressure
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