Structural Properties and Molecular Mass Distributions of Biomass-Coal Cogasification Tars as a Function of Aging

This work describes an analytical approach to determine changes in mass distributions and structural properties of biomass/coal cogasification tars, after storage of these samples as a function of temperature, time, and presence of ambient light. The samples examined were tars recovered during cogasification of pine and a sub-bituminous coal (70:30 wt %). It is shown that the approach used was able to reveal even subtle differences in the tar, which occurred during its aging under different storage conditions. Precipitation was observed to occur in the tars after 5 °C. Size exclusion chromatography and laser desorption mass spectrometry revealed the presence of molecular masses from 2000 u in the tars. UV-fluorescence spectroscopy provided information on extents of conjugation, providing evidence of sizes of conjugated aromatic systems in these tars up to at least 8 rings. The study revealed that the molecules that contained the largest conjugated aromati...