Pyrolysis Study Of Pyrrole, Pyridine And 4-methyl Pyridine Compounds

This dissertation is dedicated to investigate the pyrolysis of the fuel-bonded nitrogen(FBN) model compounds,including five(six)-membered ring nitrogen model compound pyrrole(pyridine) and the substituted six-membered ring nitrogen compound 4-methyl pyridine,with vacuum ultraviolet single-photon ionization combined with molecular beam mass spectrometry technique.This dissertation consists of five chapters.It mainly focuses on the identification and quantification of the pyrolysis products,intermediates and isomers.The consumption reactions and the decomposition channels of nitrogen containing model compounds are calculated by Gaussian-3(G3) method.In Chapter 1,the importance of the pollutant controlling to the widely employed basic energy source especially for coal and coal derived liquid fuel are briefly introduced.And the realistic signification of the inert pyrolysis investigation of the nitrogen containing model compounds to the modeling of the initial rich fuel combustion process has been pointed out.The formation mechanisms of the NO_X and the existing N element together with their conversion are reviewed.Some basic concepts related to pyrolysis are briefly introduced.The powerful combination of molecular beam mass spectrometry(MBMS) with photoionization by tunable VUV synchrotron offers significant improvements over some other pyrolysis diagnostics, including superior signal-to-noise,soft ionization,and tunability in a wide range. These advantages make threshold ionization possible,which can be used to identify isomers and detect active intermediates such as free radicals.In Chapter 2,the pyrolysis experiment equipment is introduced in detail, including the parameters of storage ring of National Synchrotron Radiation Laboratory(NSRL) and the structures of U10 and U14C beamlines.The description of the endstation combined with the principles of molecular beam and reflectron mass spectrometry are presented.A detailed description of the data dealing processes is exhibited.In Chapter 3,the pyrolysis study of pyrrole at low pressure is presented in detail. Major products observed from pyrrole pyrolysis,including H₂,C₂H₂,HCN,p-C₃H₄, C₂H₃N,especially the radical C₄H₄N,C₂H₂N are identified unambiguously by measurements of photoionization efficiency spectra.Mole fraction profiles of these pyrolysis species are measured at the selective photon energies near ionization thresholds.The lowest dissociation channels and consumption reactions of the major products of pyrrole are calculated by Gaussian-3(G3) method.The experimental results are in good agreement with theoretical predictions.In Chapter 4,pyrolysis of six-membered pyridine model compound has been studied.In general,the major products of the pyrolysis of pyridine have been identified by the measurements of photoionization efficiency spectra and the main production pathways have been proposed with respect to the Gaussian-3(G3) method calculation.Different from the primary pyrolysis procedure of pyrrole with the complex tautomers the initial precursors of the major pyrolysis products are simple and the corresponding pathways are more distinct.The pyrolysis is mainly initiated from the hydrogen abstract radicals of pyrrole,the linear radicals from the hydrogen abstract of pyrrole and the direct ring open products.It is worthy of noting that different from the pyrolysis of pyrrole and other aroma compounds the products of pyridine pyrolysis is relatively less in number and has low tendency of sooting.In Chapter 5,the pyrolysis of substituted six-membered ring model compound 4-methyl pyridine has been investigated.Instead of detail theoretical analysis of the reaction mechanism,the general results have been proposed from the products distribution and the combination of the pyrolysis investigation of its analogous pyridine.The major products are H₂,C₂H₂,C₄H₂,C₃H₃N and HCN,here HCN is not a primary initial product at low extent of decomposition.The mole fraction profiles of products have been obtained from the near threshold ionization.The pyrolysis of 4-methyl pyridine is initiated from the methyl abstraction and hydrogen abstraction procedures which are associated with the understanding of the soot formation and the NOX precursor correspondingly.