The device of the present invention delivers reactants to a reaction zone in a plug flow reactor. The feedblock encircles the reaction zone. Reactants enter the feedblock through an inlet port leading to a manifold for the delivery of reactants into a plurality of feed ports that are in connection with the reaction zone of a plug flow reactor. The invention additionally encompasses plug flow reactors including one or more feedblocks and the method of utilizing the feedblock for the reduction of radial variation in concentration upon entry of a reactant into the reaction zone.