Process for preparing silica-alumina catalysts and hydrocarbon cracking process using said catalysts

Claim 1

A PROCESS FOR CRACKING HYDROCARBON OILS WHICH COMPRISES PASSING THE OIL UNDER CRACKING CONDITIONS THROUGH A CRACKING ZONE CONTAINING A SILICA-ALUMINA CATALYST HAVING ABOUT 15-40% ALUMINA PREPARED BY REACTING AN AQUEOUS ALKALI METAL SILICATE SOLUTION HAVING A SILICA:ALKALI METAL OXIDE WEIGHT RATIO OF ABOUT 3.25:1 WITH CARBON DIOXIDE TO FORM A SLURRY OF SILICA HYDROGEL CONTAINING DISSOLVED ALKALI METAL CARBONATE, ADDING TO SAID SLURRY WITH AGITATION A SUPPLEMENTARY AMOUNT OF BASIC REAGENT WHICH TOGETHER WITH THE RESIDUAL ALKALI METAL CARBONATE PRESENT IN SAID SLURRY IS SUFFICIENT TO SUBSEQUENTLY PERCIPITATE ABOUT 15-40% ALUMINA IN THE FINAL CATALYST, COMMINGLING THEREWITH THE REQUISITE AMOUNT OF AN AQUEOUS SOLUTION OF AN ALUMINUM SALT OF A STRONG MINERAL ACID WHEREBY ALUMINA IS PRECIPITATED FROM SAID SALT SOLUTION IN AND ON SAID HYDROGEL AND THEREBY FORM A SILICA-ALUMINA COMPOSITE, AND PURIFYING AND DRYING SAID COMPOSITE.