29 regenerated catalyst particles flow to a wetting zone 30 through a line 32 line 32 may include a means such as a valve which is not shown in the figure for allowing catalyst particle flow and for restricting gas flow between the vapor phase regeneration zone 28 and the wetting zone 30 by such means the vapor phase regeneration zone 28 can operate at a pressure that is different from that of the wetting zone 30 and that of the separation zone 20 the pressure of the vapor phase regeneration zone 28 is generally at least 5 psi 34 5 kpa and preferably from 5 to 15 psi 34 5 to 103 4 kpa greater than the pressure of the wetting zone 30 because of the means for restricting gas flow in the line 32 fluctuations in the pressure of the vapor phase regeneration zone 28 generally do not propagate to the wetting zone 30 or to the separation zone 20 therefore pressure fluctuations in the wetting zone 30 or the separation zone 20 are minimized in the wetting zone 30 the entering catalyst particles are contacted with liquid isobutane some of the liquid isobutane in the wetting zone 30 is recycled via lines 23 and 35 from the product recovery facilities 40 as described hereinafter and the remainder is makeup isobutane that enters through.