A method for modifying a molecular sieve catalyst to reduce methane production during conversion of oxygenates to olefins. The molecular sieve catalyst comprises a separately synthesized framework comprising a material selected from the group consisting of silica, alumina, phosphate, and combinations thereof. The framework is contacted with a modifier, in the absence of a salt comprising a metal selected from the group consisting of manganese, zirconium, and hafnium, under conditions effective to modify the framework but insufficient to dealuminize or deironize the framework. The modifier comprises an oxygenated chelating agent comprising a parent compound which is readily removable from the framework by calcination to leave the modified molecular sieve catalyst. Also encompassed are the modified molecular sieve catalysts produced by the method, and a method of using the modified molecular sieve catalysts to reduce methane production during conversion of oxygenates to olefins.