Some aspects of the chemistry of coal tars. I. Chemical nature

Abstract

The chemical, and to a more limited extent the physical,, properties of coal tars of different origins are revicwed to serve as a background to the work to be described in later parts, mainly on tars derivcd from down-jet combustion of bituminous coal. To the same end, the chemistry of the amorphous constituents of coal tars is separately considered, and a classification on the basis of known data is given.The experimental work to be described in this series of papers is concerned with, but not entirely confined to, the chemistry of tars derived from the down-jet combustion of coal. It is desirable first to summarize and re-evaluate those portions of the literature bearing on the work undertaken.tAlthough the general characteristics of low-temperature and high-temperature tars are well known, it is not generally recognized that low-temperature tars can be subdivided according to the degree of decomposition suffered by the tar, so that only by broadly surveying the whole field can an attempt be made to construct a scale to serve as a measure of the ' primariness ' of any particular tar. One of the main obstacles in obtaining a clearer view of the interrelationships between tars and between specific tar-components is the presence of amorphous materials of unknown chemical structures, which are particularly plentiful in low-temperature tars. A critical examination of the literature was thought to be of value here in reducing the confusion that exists between amorphous materials of differing structures and origins. This was considered important not only in the further study of the amorphous constituents themselves, but also in attempting to relate the structures of the more primary of them to the chemical constitution of coal. Thus it was realized quite early in the work on down-jet tar that it was of a high degree of ' primariness ' ; this determined, to a considerable extent, the course of the subsequent investigations.

Characterization of Middle-Temperature Gasification Coal Tar. Part 1: Bulk Properties and Molecular Compositions of Distillates and Basic Fractions

“…Hence, it is important to better understand the composition of LTCT for downstream processing and reducing environmental impacts of process operation. The chemical composition of LTCT is distinctly different from that of high-temperature coal tar. − LTCT has been a supplementary feedstock to petroleum crude oil since the 1970s. − Tremendous efforts have been devoted to characterize the molecular structure and mass distribution of coal-derived liquids. Size-exclusion chromatography (SEC) is commonly used to determine the molecular size distributions of complex coal-derived liquids.…”