Hydrogenation and Liquefaction of Waste Plastics through Partical Oxidation and Water Gas Shift Reaction in Supercritical Water

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We have developed a hydrogenation process of waste plastics through partial oxidation and water gas shift reaction in supercritical water. In this research, for the development of the process, we conducted the basic study of the key reactions, namely 1) pyrolysis of hydrocarbon, 2) partial oxidation of hydrocarbon, and 3) hydrogenation through partial oxidation and water gas shift (WGS) reaction in supercritical water. The results are as follows.1) Measurement of phase equilibria of hydrocarbon - supercritical water systemWe have developed the new equipment (vibrational density measurement apparatus for high temperature and pressure) to measure the phase equilibria of hydrocarbon - supercritical water system.2) Pyrolysis of hydrocarbon in supercritical waterPolyethylene pyrolysis experiments were conducted by using batch reactors. The results showed that l-alkane/alkene ratio increased and product distribution shifted toward shorter chain hydrocarbons with increasing water density. Thi … More s result can be explained by considering change of the reaction phase with water density.3) Study on hydrogenation of hydrocarbons through partial oxidation in supercritical water.The experiments of partial oxidation of n-hexadecane in supercritical water were conducted by batch reactors. In the results, the selectivities of CO and n-alkane formation were enhanced with increasing water density. The increase in n-alkane selectivity indicates that the produced CO reacted with water to produce H2 followed by the hydrogenation of l-alkane to n-alkane.We also conducted the experiments of partial oxidation of CH4 in supercritical water using a flow apparatus. The selectivity of CO increased with increasing water density. We applied a radical network model, which is commonly used for the gas-phase oxidation of CH4, for describing the partial oxidation of CH4 in supercritical water. Modifying the elementary reactions of forming H2O2 with considering the water density effect, we could described the reaction rate and the product distribution of the partial oxidation of CH4 in supercritical water by model.4) Designs of a continuous processWe made a feasibility study for a continuous process of partial oxidation of hydrocarbon based on the above experimental results. The results suggest that a) the feed concentration of hydrocarbon should be higher than 10%, b) oxygen concentration should be around 15%, and c) liquid phase feeding of oxygen is preferable.The above results suggest that catalytic hydrogenation through partial oxidation and water gas shift reaction in supercritical water have a high potential for hydrogenation of hydrocarbons. Less