Fluorescence Spectroscopic Analysis of Tars from the Pyrolysis of a Victorian Brown Coal in a Wire-Mesh Reactor

Abstract

Constant-energy synchronous fluorescence spectroscopy was used to examine the 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 temperatures, and holding times at the peak temperature were analyzed. The synchronous spectra of all of the tars showed two characteristic peaks with centers 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 measure of the relative amounts of aromatic ring systems in oligomeric structures. Increasing heating rate during pyrolysis was found to enhance the release of larger (3 or more fused rings) aromatic ring systems. The introduction of ion-exchangeable cations (e.g., Ca 2+ ) into the brown coal suppressed the release of the larger aromatic ring systems during pyrolysis.

Rapid Gasification of Nascent Char in Steam Atmosphere during the Pyrolysis of Na- and Ca-Ion-Exchanged Brown Coals in a Drop-Tube Reactor

“…It is known that loading of Na or Ca by ionexchange causes significant reduction of the yield of primary tar [44][45][46][47][48][49][50][51][52][53] that is the source of the soot-w and heavy tar as well the as soot-c and light tar. Thus, the result shown in Figure 4 was insufficient for demonstrating catalytic roles of the chars from the Na-form and Ca-form coals for indirect/direct steam reforming of the tar.…”

Synchronous fluorimetric characterization of heavy intermediates of coal direct liquefaction

“…In general, the aromatic structural features of PA and AS such as the size of aromatic ring and the degree of condensation are important for their upgrading and stability. Ultraviolet spectrometry (UV) and fluorescence spectrometry (FL) are always used to determine the aromatic system in crude oil and coal derivates [3][4][5]. However, the PA and AS all show very wide peak with no structural characteristic in their UV spectra before being fine separated [5].…”

“…However, the PA and AS all show very wide peak with no structural characteristic in their UV spectra before being fine separated [5]. Similarly, the FL spectrometry is also limited in the determinations of PA and AS because there are very complex phosphors and energy transfers [3]. In addition, 1 H NMR and 13 C NMR can be used to determine the contents of aromatic hydrogen and carbon but they can not give the distribution of aromatic ring number.…”

“…Kister et al determined quantitatively the polyaromatic hydrocarbons (PAHs) in extractables of coal by SFL, in which three main synchronous fluorescence spectral regions were fined according to the number of lineally condensed aromatic rings [11]. Kershaw et al found that the tar from the pyrolysis of Loy Yang coal showed two characteristic peaks in the constant-energy synchronous spectrum, and suggested that constant-energy SFL is a valuable method for monitoring the concentration of the larger aromatic ring systems in pyrolysis tars [3]. Li et al found that the pyridine-solubles of coal consisted of 3-5 aromatic rings by the SFL at a constant wavelength difference of 14 nm [12].…”

A case study: what is leached from mallee biochars as a function of pH?

“…The data are accumulative in nature, e.g. the organics in the leachate in 4 weeks included those of 1 h. To make a better identification of the observed leachate biochar spectra, previous UV-fluorescence studies of coals (Kashimura et al 2004; Kershaw et al 2000) and bio-oils (Oudenhoven et al 2016) were used. Oudenhoven et al (2016) studied (heavy) pyrolysis oils with UV-fluorescence.…”