Abstract: Frangible, spray dried agglomerate catalyst supports are provided, e.g. of silica gel, which possess a controlled morphology of microspheroidal shape, rough, scabrous appearance, and interstitial void spaces which penetrate the agglomerate surface and are of substantially uniform size and distribution. The agglomerates also possess a 1-250 micron particle size, 1-1000 m2/gm. surface area, and an Attrition Quality Index (AQI) of at least 10. The agglomerates are derived from a mixture of dry milled inorganic oxide particles, e.g. silica gel, and optionally but preferably wet milled inorganic oxide particles, e.g. silica gel particles, (which preferably contain a colloidal segment of <1 micron particles) slurried in water for spray drying. The high AQI assures that the agglomerates are frangible and that polymerization performance is improved.