A fixed bed catalytic reactor for converting process fluids having an upper catalyst bed and a lower catalyst bed below the upper catalyst bed for converting process fluids flowing through the upper and lower beds. A mixing zone is located between the upper bed and lower beds, and at least one jet is provided for injecting an inclined fluid jet into the mixing zone against the flow of the process fluids to entrain process fluids within the jet and to radially mix the process fluids across the mixing zone.