This invention relates to a process and the product thereof for preparing, a molecular sieve catalyst composition, comprising a mixture of: a first quantity of molecular sieve particles, having an 8-ring or larger structure, and a pore size of from about 3 angstroms to about 15 angstroms; and a second quantity of metal carbonate particles; the mixture having been calcined at a temperature of at least about 200.degree. C. for at least about 1 second.