Separation of contact solids according to degree of contamination

Claim 1

IN A PROCESS WHEREIN A SYNTHETIC SILICA-ALUMINA GEL CATALYST POWDER IS CIRCULATED BACK AND FORTH BETWEEN A FLUIDIZED GAS OIL CRACKING ZONE AND A FLUIDIZED CATALYST REGENERATION ZONE AND BECOMES CONTAMINATED WITH IRON, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF WITHDRAWING FROM THE REGENERATION ZONE A STREAM OF IRON CONTAMINATED CATALYST, COOLING SAID CATALYST, INTRODUCING THE WITHDRAWN CATALYST INTO A FLOTATION CELL CONTAINING WATER AND ABOUT 0.001 TO 0.1 WEIGHT PERCENT BASED ON THE WATER OF A COLLECTOR SELECTED FROM THE GROUP CONSISTING OF FATTY ACIDS AND NAPTHENIC ACIDS CONTAINING 8 TO 20 CARBON ATOMS PER MOLECULE, SAID FLOTATION CELL BEING MAINTAINED AT A PH BETWEEN ABOUT 2.0 AND 6.5 PASSING AIR UPWARDLY THROUGH THE FLOTATION CELL TO AERATE AND FROTH THE ACIDCONTAINING WATER AND TO FLOAT A CONCENTRATE OF RELATIVELY HIGH CONTAMINATED CATALYST PARTICLES TO THE SURFACE WHILE TAILINGS CONTAINING RELATIVELY LESS CONTAMINATED PARTICLES SETTLE OUT AT THE BOTTOM, REMOVING THE RALATIVELY HIGHLY CONTAMINATED CONCENTRATE FROM A TOP PORTION OF THE FLOTATION CELL, AND REMOVING THE LESS CONTAMINATED TAILINGS FROM A BOTTOM PORTION OF THE FLOTATION CELL.