Influence of ion exchange and calcination on pore size and thermal stability of MCM-41 with different Si/Al ratios

A decrease in pore size and increase in thermal stability of three different MCM-41 materials with Si/Al ratios of 18.6, 17.3 and 3.1, due to ammonia ion exchange and following calcination at 540°C, has been observed by N2 sorption measurements, differential thermal analysis (DTA) and X-ray diffraction (XRD). An explanation based on recrystallization at the pore mouth is proposed and the influence of the alumina content of the materials is discussed.