Molecular weight distributions of tars produced by flash pyrolysis of coals

Abstract

The molecular weight distributions of tars produced during flash pyrolysis of coal have been determined by a combination of gel permeation chromatography and vapour phase osmometry. Small particles (62–88 μm) of two high-volatile and one low-volatile bituminous coal, and a lignite have been pyrolysed at heating rates of ≈1000 K s −1 at temperatures from 600 to 1300 K in a heated wire mesh apparatus. The molecular weight distributions range from ≈100 to 4000 and peak in the range from 250 to 750 in all cases. The evidence gathered on a softening bituminous coal clearly indicates a selective evaporation of light fractions of the metaplast.