Device for distributing a light fluid phase (2) in a heavy phase (4) in the fluidized state in a reaction chamber (5), comprising: a pipe (1) for transporting the light fluid phase; first and second windows (7, 8) created in the pipe, the second windows opening into the reaction chamber; and branches (6) extending each first window and splitting into: a central passage opening into the reaction chamber via an intermediate window (9) created in the upper wall of the branch (6); and at least two distinct lateral branches forming two lateral passages (10) opening into the reaction chamber via end-of-branch windows (11).