Abstract
Tar is one of by products which have high impact on the environment and human bodies, but it contains a lot of chemical compounds which can be used for industrial applications. This hazardous waste, however, has been disposed without any treatment because no method which tar could be easily and environmentally friendly converted to fuels and chemical intermediates. Water at sub- and supercritical conditions are considered a promising solvent for decomposition of hazardous waste into harmless compounds. In this study, experiments of catalytic or non-catalytic tar decomposition in sub- and supercritical water using a batch-type reactor at various operating conditions (623 - 773K and 30 MPa) have been conducted. First, the product distribution of tar decomposition was examined through a variety of experiments. Next, the reaction rate and a reaction mechanism for tar decomposition were determined at the identical conditions was also proposed. The recoveries of phenol and diphenylether (DPE) increased with increasing water density and in the fact the addition KOH 0.1 mol L-1 as a catalyst has influence dramatically on the product distribution. The kinetic rate constants for tar decomposition (k1) and DPE degradation to phenol (k2) were obtained from the simple kinetic analysis on the basis of simple reaction pathway.
