Heterogeneous–homogeneous oxidation of pyrrole in water vapor at elevated pressure

Abstract

The paper presents research results of the pyrrole oxidation in stoichiometric, rich, and lean mixtures of C4H4NH/O2 (ρPy = 0.15 mol/dm3, ρO2 = 0.61−0.91 mol/dm3), diluted with argon and water vapor (xD = 46−62%mol), at the uniform heating (1 K/min) of a tubular reactor made of stainless steel. It was revealed that pyrrole oxidation proceeds through the heterogeneous and homogeneous oxidation mechanisms. The contribution of heterogeneous oxidation increases with the accumulation of corrosion products on the reactor wall and a decrease in the density of water vapor. Based on the time dependences of the temperature of the reaction mixtures, it was revealed that in the presence of corrosion products, the ignition temperature of pyrrole in argon medium is about 50 K below than that in water vapor (varies within the range 608−619 K). From the results of mass spectrometric analysis, it follows that pyrrole oxidation occurs mainly through the formation of NH3. Along with N2 and NH3, N2O was detected in volatile oxidation products. It is shown that the increase in water vapor density inhibits pyrrole oxidation. The degree of nitrogen removal from the pyrrole in the form of N2 is changed from 9.9 to 90.1%mol. The composition and morphology of corrosion products are determined by X-ray diffraction analysis and scanning electron microscopy.