Methanol-to-olefin over gallosilicate analogues of chabazite zeolite

Gallosilicate analogues of chabazite zeolite with CHA topology have been synthesized, characterized and employed as catalysts for the methanol-to-olefin (MTO) process. 71Ga NMR spectra indicate that Ga is incorporated into the framework of these zeolitic materials during the hydrothermal synthesis. IR measurements show that stretching vibration of the hydroxyl groups associated with the framework Ga appears at 3600 cm−1. The gallosilicates with high Ga contents show Lewis acidity, which is possibly caused by degalliation during calcination, whereas only Brönsted acid sites are observed on the sample with relatively low Ga content. The catalysts show promising catalytic performance in the MTO reaction, particularly from the stability point of view, compared with H[Al]CHA zeolites. This is attributed to the weak Brönsted acidity associated with the framework Ga in the gallosilicates.