A novel approach to prepare β-zeolite/MCM-41 composite molecular sieve with high hydrothermal stability

The beta-zeolite/MCM-41 binary-molecular sieve composite has been synthesized by using a novel approach, in which zeolite Beta was used as silica-alumina source of mesoporous phase. Moreover the amount of mesostructure in the composite was able to be controlled just by varying the n(Na)/n(Si). The products were characterized by XRD, FTIR, N-2 adsorption/desorption, SEM and hydrothermal treatment methods. XRD patterns of the composite showed the peaks for both beta-zeolite and mesoporous molecular sieve with hexagonal symmetry. Framework vibration modes and morphology of the composite were different from those of a physical mixture of MCM-41 and beta-zeolite. The characterization results also showed that the hydrothermal stability of the mesoporous phase in the composite material was greatly improved, which is believed to be related with the mesoporous structure that formed during the assembly of dissolved fragments of beta-zeolite with the surfactant molecules together with a lot of zeolite secondary building units.