Investigation on the Stability of Silicoaluminophosphate Molecular Sieve SAPO-34

The stability of silicoaluminophosphate molecular sieve SAPO-34 has been investigated with DTA,XRD and severe treatment at high temperature.DTA tests of as-synthesized and calcined samples revealed that the framework destruction temperature of SAPO-34 is over 1300K.According to in situ XRD studies,no framework collapse happens during the organic template removing process at the temperature of ～973K and the following cooling period.The crystallinity of SAPO-34 sample remains over 80% and its catalytic performances in methanol conversion change little after 300h continuous calcination in air at 1073K.The successive steaming treatment over 45h at 1073K only destroyed the sample's crystallinity of less than 20% and damaged a little of its catalytic property,showing the high hydrothermal stability of SAPO-34.The surface composition analysis results discloses that calcination,especially steaming at 1073K gives rise to the deprivation of aluminum and phosphorus from SAPO-34 framework.