A method is disclosed of treating a crystalline material comprising a CHA framework-type molecular sieve, wherein said crystalline material has a composition and involving the molar relationship: (n)X2O3:YO2, where X is a trivalent element, Y is a tetravalent element, and n is less than 0.07, and wherein the crystalline material does not comprise a silicoaluminophosphate, is substantially free of framework phosphorus, or both. The method can comprise treating the crystalline material with steam under conditions such that the prime olefin selectivity of the treated material in an oxygenate conversion process is greater than the prime olefin selectivity of the untreated material in the same process.