Conversion of butanediol into butadiene, with scrubbing using diesters

Method for converting butanediol into butadiene that is fed with a butanediol feedstock, where said method comprises at least:

• a) an esterification step that comprises:
• a reaction section that is fed with a butanediol feedstock, with at least a fraction of the liquid pyrolysis effluent obtained from step c), and with the carboxylic acid effluent obtained from the separation section of step a), where said reaction section is implemented in the presence of an acidic catalyst at a pressure of between 0.01 and 1.0 MPa and an MMH in the reaction section of between 0.05 and 25 h−1, where MMH is equal to the molar flow rate of diol that feeds said section over the mole number of the catalyst in said section,
• a separation section that separates the effluent obtained from the reaction section into at least a diester effluent of butanediol, a water effluent, and a carboxylic acid effluent;
• b) a pyrolysis step that comprises a pyrolysis reactor that is fed with at least a fraction of the diester effluent of butanediol obtained from esterification step a) and with a fraction of the washing effluent obtained from step c), where said reactor is operated at a temperature of between 500 and 650° C. and said step produces a pyrolysis effluent,
• c) a step for separation of said pyrolysis effluent obtained from step b) such as to produce at least a liquid pyrolysis effluent, a butadiene effluent, and a washing effluent and comprising at least:
• a section for cooling said pyrolysis effluent to a temperature of less than 150° C. and for producing a liquid pyrolysis effluent and a steam pyrolysis effluent;
• a gas-liquid washing section that is fed at the top with a fraction of the diester effluent of butanediol obtained from step a) and at the bottom with the steam pyrolysis effluent and that produces a butadiene effluent at the top and a washing effluent at the bottom.