| Popis: |
An analytical pyrolysis gas chromatography mass spectrometry method has been used for investigation into the reaction mechanism leading to polycyclic compounds such as polycyclic aromatic hydrocarbons and heterocyclic compounds. Six phenols with different pendant groups were used in this study. The formation mechanism of producing naphthalene and dibenzofuran from phenol is proposed. In this mechanism, a cyclohexadiene-1-one radical was an important intermediate for the formation of these products. Three unique products were detected from m-cresol: 3,7-dimethyldibenzofuran, 1,7-dimethyldibenzofuran and 1,9-dimehyldibenzofuran. Cyclohexadiene-1-one radical was also found to be an important intermediate for dimerization reaction. Guaiacol pyrolysis yielded phenol as the major product, with a small amount of benzofuran. There arrangement of methoxyl group to methyl group and addition of methyl radical on phenoxy radical was a crucial route in this mechanism. From pyrocatechol, three indanone derivatives were produced via CO elimination with aromatic ring opening followed by pentadienone formation. After two proton donation, three pentanone biradicals were intra molecularly coupled to form indanones. From syringol pyrolysis, only benzofuran was produced, and from ethyl phenol, three types of benzofuran were detected containing different pendant groups such as methyl, ethyl and ethenyl groups. These results indicated that the phenol’s ortho position is a vital reaction site for the formation of polycyclic compounds in pyrolysis. |
