The Synthesis of Methylacetylene by the Pyrolysis of Propylene. I. The Effect of Pyrolysis Conditions on Product Yields

Propylene has been pyrolyzed in a flow system over a wide range of conditions (temperature, 800∼1400°C; contact time, 4.4×10−4∼2.3 sec.; pressure, 40∼160 mmHg) to find suitable conditions for producing methylacetylene (and allene) and for obtaining data concerning the distribution of pyrolysis products. Under proper conditions, the pyrolysis occurred without any appreciable production of tarry and carbonaceous materials. High temperatures (1200∼1300°C), short contact times (millisecond order; conversions below 30%), and low pressures (below l00 mmHg) were found to required for the good production of methylacetylene-allene. A methylacetylene-allene yield of 38 mol. per 100 mol. of propylene pyrolyzed was realized at 1200°C, 50 mmHg pressure (partial pressure of propylene, 40 mmHg), and 24% conversion (contact time, 1.7 msec.). The other gaseous products were found to be methane, ethylene, hydrogen, acetylene, 1-butene and butadiene, in decreasing order.