The present invention discloses aqueous methods for enhancing the acid sites of
fluid catalytic cracking (FCC) catalysts. The methods comprise the steps of contacting an FCC catalyst, either spent or fresh, with an
aqueous solution comprising water, an inorganic acid substantially free of
chloride and aluminum. The acid is preferably sulfurous or
sulfuric acid. The aluminum is provided by an aluminum source selected from the group consisting of the
alumina trihydrates and aluminum
oxide.
Chloride contamination of the aluminum source should be minimal, preferably less than about 1000 ppm
chloride, more preferably less than about 200 ppm
chloride. The pH of the
aqueous solution is adjusted to about 3-12 by the addition of a sufficient quantity of
ammonium hydroxide. The FCC catalyst is added to this solution, preferably with stirring, in a weight ratio of about 1 part catalyst to about 1-10 parts water to prepare an aqueous
slurry. Upon stabilization of the pH of the aqueous
slurry, enhancement of the acid sites of the catalyst is achieved and the catalyst may be separated from the
slurry and, if desired, washed. This simple, aqueous process reduces the level of many
metal poisons on the FCC catalyst and produces a catalyst having an enhanced number of acid reaction sites.