The stability of H-MCM-22 under severe thermal conditions

This study shows that the MWW structure is more stable than previously known zeolites. Structural, thermal and spectroscopic analyses have shown that acid MCM-22 zeolite is stable up to 1373K under vacuum and to 1473K in air. The Brönsted hydroxyl groups withstand temperatures up to 1173K. At 1473K there is a phase transition from the MWW structure into α-cristobalite when the sample is under vacuum while for the sample treated in air only a small fraction of the total is transformed to α-cristobalite at 1473K.