Method for producing and purifying 1,3-butadiene

Method for producing butadiene from butanediol that is fed with a butanediol feedstock, with said method comprising at least:

• a) An esterification step comprising:
• A reaction section that is fed with at least said butanediol feedstock, a carboxylic-acid-rich stream that is obtained from step c), and at least one fraction of the carboxylic acid effluent that is obtained from the separation section of step a);
• A separation section that separates the effluent that is obtained from the reaction section into at least one butanediol diester effluent, a water effluent, and a carboxylic acid effluent;
• with said reaction section being implemented in the presence of an acid catalyst, at a pressure of between 0.01 and 1.0 MPa, and at an MMH in the reaction section (molar flow rate of diol feeding said section with a catalyst mol number in said section) of between 0.05 and 25 h−1;
• b) A pyrolysis step comprising a pyrolysis reactor that is fed with at least said butanediol diester effluent that is obtained from the esterification step a), carried out at a temperature of between 400 and 650° C. in such a way as to produce a pyrolysis effluent;
• c) A step for separation of said pyrolysis effluent that is obtained from step b), comprising at least:
• A section for cooling said pyrolysis effluent to a temperature that is lower than 150° C., producing a liquid pyrolysis effluent and a vapor pyrolysis effluent;
• A gas-liquid washing section that is fed at the top with at least one fraction of the carboxylic acid effluent that is obtained from the separation section of step a) and at the bottom with said vapor pyrolysis effluent and producing a butadiene effluent at the top and a washing effluent at the bottom;
• in which a carboxylic-acid-rich stream comprising at least a portion of the liquid pyrolysis effluent is recycled to step a);
• d) A purification step that is fed with the butadiene effluent that is obtained from step c) comprising at least:
• A gas-liquid washing section that is fed at the top with a water-rich effluent and at the bottom with the butadiene effluent that is obtained from step c) and producing a hydrated butadiene effluent and at the bottom an aqueous washing effluent;
• A section for final purification of the hydrated butadiene effluent making it possible to eliminate water, butenes, and lighter products.