Study on Time of Adding Calcium Salt during Crystallization Process for Zeolites Containing Calcium

Abstract

For the zeolites containing calcium, which are superior catalysts in high temperature MTO conversion, the effect of the time of adding calcium salt during the crystallization process on the physical properties and the catalytic performance was studied. It was found that large amounts of calcium were contained in the zeolite when calcium salt was added before or during the crystallization, while calcium was hardly done after the completion of it. It indicated that there were at least two kinds of modification states of the acid sites with calcium, because calcium contained by the addition of calcium salt before the crystallization was hardly ion-exchanged with potassium ions, while calcium during the crystallization can be done. Further, it was confirmed by methanol conversion that the amounts of calcium contained affected the yields of ethylene and propylene.