Structural analysis of tars from fluidized-bed pyrolysis of coal. 1. Gas-liquid chromatography of aliphatic and aromatic subfractions

The effect of pyrolysing gas composition on the low-molecular-weight aliphatic and aromatic components of fluidized-bed tars has been investigated. Two tars from the rapid pyrolysis of coal in a fluidized-bed were solvent-fractionated into oils, asphaltenes and benzene-insoluble materials. The aliphatic and low-molecular-weight aromatic subfractions of the oils were then analysed by glass-capillary column gas-liquid chromatography. The results show that pyrolysis in a more active atmosphere of char gasification gases is ‘deeper’, and, to some extent, similar to hydrogen-assisted pyrolysis; the yield of tar is higher, and the product has higher aromaticity and average molecular weight compared with pyrolysis in nitrogen-rich flue gases.