The catalytic reactor consists of a chamber [1] that contains at least one catalyst bed [2] in solid form, with the reactor being supplied with effluent to be treated by a pipe [3] that empties into a separator [4] between gas and liquid, with the liquid obtained from the separator being collected in a tank, and a plate [9] being arranged between the separator [4] and the solid catalyst bed [2]. The plate [9] consists of at least two closed boxes [10], with at least two vertical tubes [11] provided with openings [12] linking with the interiors of the boxes [10] passing through the boxes, and with the liquid distributor [8] channeling the liquid from the tank into said boxes [10].