Investigation of precursor reactions in the De-Novo-synthesis of PCDD/PCDF on fly ash

At 300°C thermal experiments are performed with fly ash which had been spiked with 12C-13C mixtures. The resulting isotopically labeled PCDD/PCDF were analyzed by HRGC-HRMS. With PCDD besides 12C12 and 13C12 structures also substantial fractions of mixed species (12C6-13C6) were formed, indicating that dioxins are formed partly via condensation of phenyl rings. In contrast to that no such mixed species were obtained with PCDF. Consequently the synthesis of furans proceeds directs from preformed biphenyl structures.