【2026 Pyrolysis Reaction】The pyrolysis reaction must be carried out at a low hydrocarbon partial pressure

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Why must the cracking reaction be carried out at a low hydrocarbon partial pressure? From the perspective of chemical equilibrium, the hydrocarbon cracking reaction is a process in which the number of molecules increases. For dehydrogenation reactions, reducing the pressure favors the formation of ethylene and hinders the occurrence of secondary reactions. From a kinetic perspective, a low hydrocarbon partial pressure reduces the rates of both the primary and secondary reactions, but its effect on the rate of the secondary reaction is much greater than that on the primary reaction, thereby increasing the relative rate of the primary reaction with respect to the secondary reaction. Therefore, the pyrolysis reaction must be carried out at a low hydrocarbon partial pressure to reduce the occurrence of secondary reactions.