Effects of decrease in number of acid sites located on the external surface of Ni-SAPO-34 crystalline catalyst by the mechanochemical method

In order to improve shape selectivity of the methanol to ethylene conversion and mitigate coke formation, the acid sites located on the external surface of Ni-SAPO-34 crystals were neutralized by the intrinsic mechanochemical method. Ni-SAPO-34 crystals were mixed in an agate mortar with basic alkaline or alkaline earth metal oxides supported on microspherical non-porous silica. Their catalytic performances in methanol conversion were enhanced, especially in the case of BaO-modified catalyst. The reason was verified by adopting the cracking of t-butylbenzene, which could not access into the pore channel due to its bulky molecular size. These changes in the reaction performance consistently could be ascribed to the decrease of the acid sites on the external surfaces.