Dinitriles and nitriles are common intermediates of pyrrole pyrolysis

Abstract

Pyrrole is a typical fuel nitrogen model compound of coal and it is the precursor of fuel-NOx. The mechanism and kinetics of pyrrole pyrolysis were studied in a jet-stirred reactor coupled with a synchrotron vacuum ultraviolet molecular beam mass spectrometer and a gas chromometer over the temperature range of 940–1240 K at atmospheric pressure. Two sets of new data of pyrrole pyrolysis were provided. Based on the photoionization efficiency analysis, nitrogenous products are mainly produced in the form of nitriles and dinitriles. Of the pyrrole pyrolysis products, six nitriles were newly identified including methyl isocyanide (C2H3N), cyanogen (NCCN), isocyanogen (CNCN), propionitrile (C3H5N), propanedinitrile (C3H2N2), butanedinitrile (C4H4N2). Mole fractions of pyridine (C5H5N), C3H2N2, cyanovinylacetylene (C5H3N), and benzonitrile (C7H5N) were also quantified. HCN is the dominant nitrogenous product of pyrrole pyrolysis. C2H2 and CH4 are the major carbonaceous products. An updated pyrrole kinetic model was proposed comprising 196 species and 2939 reactions. The production of pyridine and several nitriles during pyrrole pyrolysis could be reasonably predicted using the current model. C3H2N2 is mainly produced by the reaction between CH2CN and other nitriles, and it is converted into CH2CN and CH3CN. The reaction between CH3 and C3H2N2 is the most sensitive reaction for promoting the consumption of C3H2N2. Results of this work confirm the importance of dinitriles and nitriles during the pyrolysis of pyrrole as an important fuel-NOx model compound of coal and other nitrogen-containing fuels.