Reactor for performing a reaction between two fluid reactants over a catalyst bed with premixing of the fluid reactants in a mixing

a reactor (1) for carrying out a reaction between two fluid reactants (2, 3) on a catalyst bed (4) with premixing of the fluid starting materials (2, 3) before being fed to the catalyst bed within a delay time is proposed less than 150 ms in a Mixing device (5), which is characterized in that the mixing device (5) is formed of the following elements, which are arranged transversely to the direction of flow of the first fluid feed stream (2) is substantially: - two or three successively arranged rows of tubes (6) thereof, which constrict with turbulence generators on the outside of the passage cross section for the first fluid reactant stream (2) to 1/2 to 1/10, wherein through the interiors of the tubes (6) the second fluid reactant stream (3) and guided through openings (7) in the tubes (6) in the first fluid reactant stream (2) is injected, and - an upstream the pipes (6) perforated plate (10) and - a downstream pipes (6) perforated plate (11).