Process and apparatus for producing ethylenically unsaturated halogenated hydrocarbons

An improved process for the thermal dissociation of halogenated aliphatic hydrocarbons to form ethylenically unsaturated halogenated hydrocarbons in a reactor which comprises reaction tubes running through a convection zone and through a radiation zone located downstream in the flow direction of the reaction gas, which has one or more burners in the radiation zone to heat the reaction tubes, and a heating apparatus is provided for the halogenated aliphatic hydrocarbon which is located outside the reactor and is heated by the energy content of the reaction gases leaving the radiation zone, wherein the improvement comprises:

• a.) introducing a controlled input of an initiator for the thermal dissociation of said halogenated aliphatic hydrocarbon into the reaction tubes at one or more points within the reactor, said initiator being chosen from the group consisting of at least one chemical promoter for the thermal dissociation reaction;
• a localized energy input adapted to form free radicals to promote the thermal dissociation reaction;
• and combinations of the foregoing:
• b.) controlling the input of an initiator and amount of the fuel for the burners such that:
• i.) the conversion of the dissociation reaction changes by no more than 20%, if at all, compared to operation without the chemical promoter and/or the localized energy input,
• ii.) the temperature of the reaction mixture leaving the reactor is in the range from 400° C. to 470° C., and
• iii.) the molar conversion based on the halogenated aliphatic hydrocarbon used is in the range from 50 to 65%.

An improved apparatus for the thermal dissociation of halogenated aliphatic hydrocarbons to form ethylenically unsaturated halogenated hydrocarbons, which comprises a reactor having:

• a.) a convection zone;
• and a radiation zone defined therein,
• b.) reaction tubes running through the convection zone and through the radiation zone, the radiation zone being located downstream in the flow direction of the reaction gas,
• c.) at least one burner being provided in the radiation zone to heat the reaction tubes,
• d.) a flue gas chimney;
• and
• said apparatus further comprising a heating apparatus for the halogenated aliphatic hydrocarbon which is:
• i.) located outside the reactor;
• and
• ii.) heated by the energy content of the reaction gases leaving the radiation zone,
• wherein the improvement comprises:
• e.) means for introducing an initiator for accelerating the dissociation of said halogenated aliphatic hydrocarbon including:
• i.) means of introducing chemical promoters for the thermal dissociation reaction into the reaction tubes;
• ii.) means of introducing localized energy to form free radicals in the reaction tubes, or
• 111.) a combination of means for introducing chemical promoters and localized energy to form free radicals;
• f.) means of for evaluating the degree of dissociation of said halogenated aliphatic hydrocarbon by:
• i.) determining the dew point of the flue gas at the exit from the convection zone;
• means of introducing the fuel for the burner(s),
• ii.) determining the dew point of the flue gas in the flue gas chimney, or
• iii.) determining the molar conversion of the dissociation reaction, or
• iv.) a combination of any of the foregoing i.), ii.) and iii.);
• and
• g.) means for controlling the degree of dissociation of said aliphatic halogenated hydrocarbon by:
• i.) regulating the amount of fuel;
• ii.) regulating the input of initiator;
• or
• iii.) a combination of the foregoing i.) and ii.) in response to:
• iv.) the dew point of the flue gas at the exit from the convection zone;
• or
• v.) the dew point of the flue gas in the flue gas chimney;
• or
• vi.) the molar conversion of the dissociation reaction.