Pyrolysis of poly-p-xyleneglycol in supercritical water, supercritical methanol, and supercritical ethanol

Pyrolysis of poly-p-xyleneglycol(PPXG) in supercritical water, supercritical methanol and supercritical ethanol were studied. Experiments were performed at temperatures of 648 K and 693 K, and at pressures of 10, 20, 30, and 40 MPa. Reaction period of 1 h was specified for all reactions. Products of reaction were classified into four categories: gas, volatile matter, oil and char. The yields of these four classes of components were determined. The reactions in supercritical water produced mainly both oil and char, while only a small amount of gaseous matter was produced. Regarding the reactions in supercritical methanol and supercritical ethanol, the main products were gaseous matters. The amount of gaseous products increased steeply in condition of high-temperature and high-pressure, while formation of char was inhibited. The main gaseous product was methane in the case of reaction in supercritical methanol and ethane in the case of reaction in supercritical ethanol. From volatile chemicals produced, it was found that PPXG decomposed by parallel reactions of radical decomposition and solvolysis reaction. The yield of char decreased as pressures were raised in lhe reactions in each of the three supercritical solvents. The total amount of the products of reaction was almost the same as that of the initial amount of PPXG charged to the reactions in supercritical water. On the other hand, concerning reactions in supercritical methanol and supercritical ethanol, the total amount of products of reaction was in excess of the initial amount of PPXG charged in high-temperature and high-pressure conditions. This implies that the methanol or ethanol reacts directly and converted into the reaction products.