A process for continuous heterogeneous catalytic hydrogenation of MDA. The process occurs in a reactor cascade including n serially connected reaction spaces, R.sub.i, that are each filled with catalyst and can be filled or emptied independently of one another where 1in, in the order in which they are connected. R.sub.1 is temporarily disconnected from the cascade as soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree. The reconfigured reactor cascade R.sub.i, includes i reaction spaces where 1i(n1), in the order in which they are connected. Each reaction space R.sub.i where 2in becomes a reaction space R.sub.i where 1i(n1). The catalyst in R.sub.1 is replaced and/or regenerated and R.sub.1 is subsequently connected as reaction space R.sub.i where i=n.

A process for continuous heterogeneous catalytic hydrogenation of MDA. The process occurs in a reactor cascade including n serially connected reaction spaces, R.sub.i, that are each filled with catalyst and can be filled or emptied independently of one another where 1in, in the order in which they are connected. R.sub.1 is temporarily disconnected from the cascade as soon as the catalyst present in R.sub.1 has in the course of the reaction become deactivated to an undesirable degree. The reconfigured reactor cascade R.sub.i, includes i reaction spaces where 1i(n1), in the order in which they are connected. Each reaction space R.sub.i where 2in becomes a reaction space R.sub.i where 1i(n1). The catalyst in R.sub.1 is replaced and/or regenerated and R.sub.1 is subsequently connected as reaction space R.sub.i where i=n.

The present invention provides a process for producing methylenebis(cyclohexylamine), comprising the steps of 1) catalytically hydrogenating MDA, 2) removing the catalyst and 3) subsequently distilling the product of the hydrogenation, in which at least one dividing-wall column is used in step 3). Exposure to high temperature and residence time of the product is reduced and problems due to crystallization do not occur. The methylenebis(cyclohexylamine) isomer ratio also may remain largely constant during the distillation.

The present invention provides a process for producing methylenebis(cyclohexylamine), comprising the steps of 1) catalytically hydrogenating MDA, 2) removing the catalyst and 3) subsequently distilling the product of the hydrogenation, in which at least one dividing-wall column is used in step 3). Exposure to high temperature and residence time of the product is reduced and problems due to crystallization do not occur. The methylenebis(cyclohexylamine) isomer ratio also may remain largely constant during the distillation.

A plant for hydrogenation of methylenedianiline with a hydrogen donor has a conditioning unit for the reactants, a reactor unit for synthesis of PACM and a separation unit. The conditioning unit has at least part of the length of the (feed) conduits for reactants1, reactant2 and at least one solvent, at least one heat exchanger in at least one (feed) conduit, at least one mixer for mixing the reactants and/or at least one reactant with at least one solvent. The reactor unit has at least one fixed bed reactor as main reactor with an immobile catalyst packing. The separation unit has at least a first separation stage for removal of the at least one solvent and a second separation stage for separation of the reactant and by-products from the PACM product. The hydrogenation of MDA is conducted in a corresponding process.

A plant for hydrogenation of methylenedianiline with a hydrogen donor has a conditioning unit for the reactants, a reactor unit for synthesis of PACM and a separation unit. The conditioning unit has at least part of the length of the (feed) conduits for reactants1, reactant2 and at least one solvent, at least one heat exchanger in at least one (feed) conduit, at least one mixer for mixing the reactants and/or at least one reactant with at least one solvent. The reactor unit has at least one fixed bed reactor as main reactor with an immobile catalyst packing. The separation unit has at least a first separation stage for removal of the at least one solvent and a second separation stage for separation of the reactant and by-products from the PACM product. The hydrogenation of MDA is conducted in a corresponding process.