Method for producing and purifying 1,3-butadiene

A method for producing butadiene from a butanediol feedstock, said method comprising:

• a) An esterification step comprising:
• feeding a reaction section said butanediol feedstock, a carboxylic-acid-rich stream that is obtained from step c), and at least one fraction of a carboxylic acid effluent that is obtained from a separation section of step a) said reaction section comprises an acid catalyst and is operated 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 to produce a reaction section effluent comprising butanediol diester;
• separating in the separation section the reaction section effluent into at least one butanediol diester effluent, a water effluent, and the carboxylicacid effluent;
• b) A pyrolysis step comprising feeding a pyrolysis reactor with at least said butanediol diester effluent that is obtained from the esterification step a), said pyrolysis carried out at a temperature of between 400 and 650° C. to produce a pyrolysis effluent;
• c) A separating step for separation of said pyrolysis effluent that is obtained from step b), comprising at least:
• cooling said pyrolysis effluent in a cooling section to a temperature that is lower than 150° C. to produce a liquid pyrolysis effluent and a vapor pyrolysis effluent;
• feeding the top of a gas-liquid washing section with at least one fraction of the carboxylic acid effluent that is obtained from the separation section of step a) and at the bottom of the gas-liquid washing section with said vapor pyrolysis effluent to produce a butadiene effluent at the top and a washing effluent at the bottom;
• recycling at least a portion of the liquid pyrolysis effluent to step a) as the carboxylic-acid-rich stream;
• d) A purification step that is fed with the butadiene effluent that is obtained from step c) comprising at least:
• introducing a stream comprising water to the top of a second gas-liquid washing section and introducing at the bottom of the second gas-liquid washing section the butadiene effluent that is obtained from step c) and producing a hydrated butadiene effluent and at the bottom an aqueous washing effluent;
• eliminating water, butenes and light products comprised in the hydrated butadiene effluent in a final purification section to produce butadiene.