The Synthesis of Methylacetylene by the Pyrolysis of Propylene. IV. The Pyrolysis of Allyl Chloride

Abstract

Abstract Allyl chloride has been pyrolyzed in a flow system over a wide range of conditions (temperature, 800–1200°C; contact time, 0.665×10−3–78.9×10−3 sec; concentration, 4.0–13.5 mol%; pressure, atmospheric pressure) to find suitable conditions for producing methylacetylene and allene. In addition, a study on the mechanism of pyrolysis of allyl chloride at high temperatures (800–1200°C) has been made. A total yield of allene and methylacetylene of 14 mol per 100 mol of allyl chloride pyrolyzed was obtained under suitable conditions. By means of the zero conversion method, hydrogen, propylene, allene, diallyl, 1,3-cyclohexadiene, and benzene have been found to be the main reaction products in the early stage of the pyrolysis, while methane, acetylene, ethylene, methylacetylene, butene-1, and butadiene have been found to be the side reaction products. The over-all activation energy of decomposition was 39.4 kcal/mol for an A factor of 108.7 sec−1. On the basis of the observed results, a free-radical mechanism has been proposed for the main reactions and the principal side reactions. It was further concluded that the pyrolysis was a radical decomposition initiated by the reaction C3H5Cl→C3H5·+Cl and that the over-all mechanism in the early stage of the pyrolysis was represented essentially by the reaction 2C3H5Cl→C3H5·+\dotC3H4Cl+HCl.