CONVERSION OF COAL-TAR PITCH IN SUPERCRITICAL WATER

摘要

China has an abundance coal-tar pitch resource and the annual output is about 3 million tons. However, the use of coal-tar pitch has some drawbacks in relation with the emission of highly toxic and carcinogenic substances during combustion. Thus, conversion of coal-tar pitch into clean and light oil is very important. Recently, supercritical water (SCW) has gained great attention because of the significant variation of solvent properties around critical point. It can become miscible with light gases, oils and aromatics to form a homogeneous phase. Some researchers have studied the effect of SCW on coals and oil shale conversion. They found that SCW was an effective solvent for the extraction and decomposition of heavy hydrocarbons. The conversion in SCW was higher than that in supercritical toluene. Takafumi Sato et al. investigated the conversion of asphalt in supercritical water. Water apparently participated in the decomposition of asphalt into smaller molecular compounds. In this study, the conversion of coal tar-pitch to light oil in SCW was investigated.