Abstract: Attrition resistant and stable catalyst composition comprising crystalline aluminosilicate zeolites e.g. rare earth exchanged zeolites dispersed in an inorganic matrix containing synthetic amorphous silica-alumina and clay are prepared by a process which reduces the level of polluting ammonium salts by eliminating the use of ammonium hydroxide in the steps prior to primary filtration. During the synthesis of the amorphous inorganic matrix wherein alkali metal silicate and aluminum salt solutions are gelled and subsequently combined with zeolitic materials, the ammonia reagent is replaced by non-polluting additives such as magnesium or calcium hydroxides (or oxides) prior to a primary filtration stage without decreasing the catalytic activity of the resulting zeolite promoted hydrocarbon conversion catalysts.