Oils and Phenols-and-Water-Free Tars Produced in Pyrolysis of 23 Chinese Coals in Consecutive Temperature Ranges

摘要

Coal pyrolysis has been widely studied, and the overall tar yield has been reported frequently in the literatures. It is recognized that the yield and composition of the tar vary with the coal rank and pyrolysis temperature, but detailed information is limited, especially for the oil fraction defined as the hexane-soluble matter. In this work, 23 Chinese coals of different rank with carbon content of 73.7-89.1% are pyrolized in a fixed-bed reactor, and the liquid products collected in the temperature ranges of 110-300, 300-400, 400-500, 500-600, and 600-800 ℃ are extracted by n-hexane. The yields of phenols-and-water-free tars and oils are estimated, and the oil fractions are analyzed by HPLC. It is found that the total yields of the phenols-and-water-free tar are generally greater than 10 wt % of the coals (dry and ash-free), and 30-60 wt % of the tars are soluble in n-hexane. Generally, about 50 wt % of the phenols-and-water-free tars and oils are produced in the temperature range of 400-500 ℃. The HPLC analysis indicates that the oils from the coals with carbon contents of less than 80 wt % are dominated by aliphatic hydrocarbons, whereas those from the coals with carbon contents of greater than 80 wt % are dominated by one- and two-ring aromatics. Aliphatic hydrocarbons appear in all the oil fractions regardless of the pyrolysis temperature and coal rank, whereas the one-ring aromatics are found only in oils produced at 400-500 ℃.