Method of reducing contaminants on finely divided catalyst

Claim 1

IN A CONTINUOUS PROCESS FOR THE CONVERSION OF HYDROCARBONS WHEREIN CONVERSION IS OBTAINED IN THE PRESENCE OF FINELY DIVIDED FLUIDIZED CATALYST HAVING A GEL STRUCTURE, THE CATALYST CONTINUOUSLY CIRCULATING THROUGH A REACTION ZONE AND A REGENERATION ZONE AND WHEREIN THERE IS A GRADUAL ACCUMULATION OF NON-COMBUSTIBLE CONTAMINANTS ON THE CATALYST AS THE PROCESS CONTINUES, THE CATALYST ABOVE 40 MICRONS IN DIAMETER ACQUIRING A SURFACE COATING OF NON-COMBUSTIBLE CONTAMINANTS AND HAVING A CENTRAL CORE FREE OF THE CONTAMINANTS, THE CATALYST BELOW 40 MICRONS IN DIAMETER BECOMING COMPLETELY IMPREGNATED WITH THE CONTAMINANTS, THE STEPS WHICH COMPRISE ADDING TO THE CIRCUIT FRESH CATALYST IN THE FORM OF A COARSE FRACTION OF A PARTICLE SIZE ABOVE ABOUT 40 MICRONS IN DIAMETER, SUBJECTING THE CATALYST IN THE CIRCUIT TO ACCELERATED ATTRITION BEYOND THE NORMAL ATTRITION IN THE CIRCUIT WHEREBY FINE PARTICLES BELOW 40 MICRONS IN DIAMETER ARE FORMED DUE TO THE SCRAPINGS OF THE COARSE CATALYST AND A CENTRAL CORE SUBSTANTIALLY FREE OF CONTAMINANTS IS EXPOSED, AND CONTINUOUSLY SEPARATING AND DISCARDING FROM THE CIRCULATING CATALYST THE FINE PARTICLES CONTAINED THEREIN AT A RATE OF MAINTAIN IN THE CICUIT ABOUT 10 TO 20% OF THE FINE PARTICLES SO AS TO MAINTAIN THE FLUIDITY OF THE CATALYST, WHEREBY A HIGH LEVEL OF CATALYST ACTIVITY IS MAINTAINED WITHIN THE CIRCUIT.