High-vacuum heating of tars relevant in combustion and material science

Tars, typically derived from coal and heavy fuel processing or formed in combustion, are complex mixtures of organic species with aromatic and aliphatic functionalities spanning from few hundreds up to thousands of Da of molecular weight (MW). Many different diagnostics are required for their characterization, nevertheless the identification of single molecular components is not straightforward, and the speciation of the huge number of aromatic molecules is only partially effective avoiding reaching the complete map of the tar composition. In the present work a fractionation method based on low-vacuum heating has been preliminarily tested on synthetic mixtures of polycyclic aromatic hydrocarbons (PAH) presumed to be the basic aromatic moieties of tar components. The characterization of the separated components has been done to verify the operative conditions more favourable to an effective separation. The procedure has been also applied to a typical sample of combustion-formed tar and a synthetic pitch for tracing to their structure/composition.