A CHEMICAL STUDY OF ASPHALTENES FROM THE LIQUEFACTION OF COAL.

摘要

The chemistry of asphaltenes was studied in an attempt to determine the influence of coal characteristics on the composition of the liquefaction products. Forty coals were liquefied in tetralin and the coals and asphaltenes were studied using spectroscopic, oxidative degradative, and derivatization techniques. A suite of 26 high-sulfur coals were selected to provide a homogeneous set with which to evaluate the relationships between coals and asphaltene using bivariate and multivariate statistical techniques. Other coals studied were from 5 different geologic provinces, had low sulfur contents, and several exhibited notably high-hydrogen contents.;The asphaltenes from the high-sulfur coals were structurally homogeneous since the range of variability was quite narrow in terms of the compositional parameters. The carbon and oxygen contents of the asphaltenes varied linearly with coal rank parameters. This was also evident in the low-sulfur coals that were studied. However, the structural parameters obtained from the spectroscopic analyses and oxidative degradation of asphaltenes could not be statistically related to coal properties or behavior.;In most cases the asphaltenes exhibited a higher concentration of aryl methyl than coals, indicating that analogs of dibenzyl ether and/or diphenylethane had been cleaved. Alkyl chains having between 9 and 17 carbon atoms on aromatic rings were ubiquitous in asphaltenes. Generally, protons in the (alpha) position were most abundant in the asphaltenes from typical, high-vitrinite coals, and their concentration varied little between coals. Aromatic and (beta) protons, however, displayed greater variability with rank and petrology of the feed coal.;The principal coal properties which influenced the chemical composition of asphaltenes were related to coal rank and petrology; however, other geologic considerations such as weathering and an accelerated rate of coalification also affected asphaltene structure.;Nuclear magnetic resonance was used to obtain carbon and hydrogen distributions, and infrared analysis was used to obtain additional information on functional groups. Oxidation with trifluoroperoxyacetic acid was used to study hydrogen-rich structures, and the reaction was modified to better preserve primary oxidation products such as citraconic, homophthalic, cyclohexene dicarboxylic, and long-chain alkanoic acids.