A shell-and-tube reactor is disclosed. Contact tubes are disposed within a cylindrical housing and are secured to tube plates. Gas and liquid phases are received via a feed opening in a lower end cap and discharged via an upper end cap in the housing. A distributor device is disposed in the housing, such that the tube plates serve as a horizontal plate for the distributor device to back up the gas phase and form a gas cushion, and vertical elements extend from the contact tubes. The vertical elements are adapted to conduct the liquid phase, are open in the upstream direction, and project outward in the direction of the feed opening through the gas cushion. The vertical elements further include at least one first opening on the circumference for the gas phase and at least one second opening for the liquid phase.