A shelf is incorporated into a typical FCC riser that permits the tips of the nozzles to extend past the wall of the riser while preventing the tips from promoting coke build-up and protecting the tips from erosion. The shelf can be part of an angled section that often appears in a transition zone for increasing the internal diameter of the riser to accommodate the volumetric expansion of the feed. The shelf section reduces the non-uniformity in the mixing of the catalyst and feed and minimizes backmixing of the feed injection. The shelf of this invention accomplishes these objectives without recessing the feed injectors into the riser wall which can interfere with the spray pattern.