Process for the production of methylacetylene and propadiene

A process for producing methylacetylene and propadiene in a reaction zone which is elongate in one direction (one axis), comprising a heating zone and a cooling zone following said heating zone, said process comprising circulating a gas mixture comprising at least one hydrocarbon containing at least three carbon atoms and at least one diluent in the heating zone having a total residence time for the gas mixture in the heating zone in the range of about 12 to 2000 milliseconds (ms), at an absolute pressure which is above atmospheric pressure, in a flow direction substantially parallel to the direction (to the axis) of the heating zone, wherein the heating zone comprises in succession at least one pre-heating zone in which the temperature of said gas mixture increases by about 50° C. to 120° C. per {fraction (1/10)} of the length of the heating zone, at least one zone for pyrolysis in which the temperature rises further by about 20° C. to 50° C. per {fraction (1/10)} of the length of the heating zone and at least one methylacetylene-propadiene formation zone in which the temperature rises further by about 70° C. to 150° C. per {fraction (1/10)} of the length of the heating zone, wherein the residence time for the gas mixture in the methylacetylene-propadiene formation zone is shorter than the residence time for the gas mixture in the pyrolysis zone;

• and the residence time for the gas mixture in the pyrolysis zone is in the range of about 10 to 1000 ms, the products formed at the end of the heating zone being cooled in the cooling zone then recovered at the end of the reaction zone.