Fluorescence spectroscopic analysis of tars from the pyrolysis of a Victorian brown coal in a wire-mesh reactor

Constant-energy synchronous fluorescence spectroscopy was used to examine t he aromatic structural features of the tars from the pyrolysis of Loy Yang brown coal in a wire-mesh reactor. Tars from the pyrolysis of the raw coal and its H-form and Ca-form coal samples at various heating rates, peak temp eratures, and holding times at the peak temperature were analyzed. The sync hronous spectra of all. of the tars showed two characteristic peaks with ce nters at ca. 335-340 and 385-390 nm. Synchronous fluorescence intensity per unit absorbance was found to be a useful parameter to examine the changes in the intramolecular energy transfer due to the changes in tar structural features. The degree of intramolecular energy transfer is considered a meas ure of the relative amounts of aromatic ring systems in oligomeric structur es. Increasing heating rate during pyrolysis was found to enhance the relea se of larger (3 or more fused rings) aromatic ring systems. The introductio n of ion-exchangeable cations (e.g,, Ca2+) into the brown coal suppressed t he release of the larger aromatic ring systems during pyrolysis.