Pulsed compression is introduced for the conversion of methane, by pyrolysis, into ethylene. At the point of maximal compression temperatures of 900 to 1620 K were reached, while the initial and final temperature of the gas did not exceed 523 K.
By the use of a free piston reactor concept pressures of up to 460 bar were measured with nitrogen as a diluting gas. From 1100 K onwards methane conversion was measured. By increasing the temperature, the mechanism of pyrolytic methane conversion, being subsequent production of ethane, ethylene, acetylene, benzene, and ultimately tar/soot, was clearly observed. Without hydrogen in the feed, the attainable operating window (C2-selectivity vs. methane conversion) observed was similar to other catalytic oxidative and non-oxidative coupling processes.
With hydrogen, in a first attempt to optimize the product yield, 24% C2-yield (62% ethylene selectivity, 93% C2- selectivity) at 26% conversion was reached without producing observable soot. It is worthwhile to explore pulsed compression further because it does not require a catalyst and therefore, does not deactivate over time and it operates at low reactor temperature.