Production of a ketone or aldehyde prepared by condensation is optimized by dehydration and hydrogenation of a starting acetone/ketone or aldehyde in a reaction zone and wherein water is partially eliminated from such reaction product by at least one membrane pervaporation module, the pervaporation module being fed tangentially and situated laterally to the reaction zone and operating in a loop, and wherein a fraction of reaction product exiting the reaction zone is thus partially dehydrated and recycling such dehydrated concentrate to the reaction zone.