Method and apparatus for separating a liquid reaction product from a gaseous stream in a catalytic reactor by means of a metallic sheet being indirectly cooled by a cooling surface and having a plurality of percolations in form of geometric-shaped protrusions on both sides of the sheet each with an open base, the open base is on the side of the sheet facing a catalyst bed are arranged upwards and on the side facing the cooling surface the open base faces downwards.