A process for carrying out a multi-phase reaction in a continuously operated tube reactor operated according to the counter current principle in which reactor components of a liquid phase flowing downwards as a thin film in said tube reactor and components of a continuous gas flowing upward in said tube reactor are brought to material transfer, or reaction respectively. The gas phase is pulsed, by repeated temporary pressure lowering at the gas entry into said tube reactor and/or repeated temporary pressure increase at the gas exit from said tube reactor, to counteract film thickness growth and liquid phase stagnation.