Preparation And Application Of C-mcm-22 Composite Zeolites

For hard templates have good stability and spatial confinement, the hard template method is a very important method for synthesizing composite materials and the zeolites with specific size and morphology.In this paper, firstly, SiO₂ colloidal crystal and MCM-22 zeolites were synthesized. Secondly, macroporous carbon zeolites were prepared using SiO₂ colloidal crystal as hard template. Thirdly, granular C-MCM-22 composite zeolites were prepared using carbon zeolites as hard template, and monodisperse C-MCM-22 composite zeolites were preapared using MCM-22 zeolites as hard template. All the materials were characterized by XRD,SEM, and so on. At last, composite catalysts were used in the synthesizing of dimethyl carbonate (DMC)by gas-phase oxidative carbonylation of co-feeding methanol with dimethyl ether. The results aresummarized as follows:1. Monodisperse SiO₂ microspheres were prepared by sol-gel method. Then, SiO₂ colloidal crystal was synthesized by solvent evaporation method. Finally, macroporous carbon zeolites were prepared using SiO₂ colloidal crystal as hard template. The characterized results indicated that the monodispersed SiO₂ microspheres with diameter about 200nm had regular spherical shape, and the SiO₂ colloidal crystal was ordered. The macroporous carbon zeolites have copied the ordered structure of SiO₂ colloidal crystal. Its bore diameter was as large as the bore diameter of SiO₂ microspheres.2. Using hexamethyleneimine(HMI) as soft template, and the macroporous carbon zeolites as hard template, granular C-MCM-22 composite zeolites were prepared by static hydrothermal crystallization. The characterized results of SEM and XRD showed that the lamellar MCM-22 zeolite had grown inside the macroporous carbon zeolites. The shape of this MCM-22 zeolites were different from the common MCM-22 zeolites. Its diameter ranges from 50 nm to 200 nm.3. Monodisperse MCM-22 zeolites were prepared by static hydrothermal crystallization method. Then, the monodisperse C-MCM-22 composite zeolites were prepared by static hydrothermal crystallization method, using sucrose as carbon source and MCM-22 zeolites as hard template. The characterized results proved that the MCM-22 zeolites was thin pancake-shaped, and the monodisperse C-MCM-22 composite zeolites, wrapped by a layer of carbon, was thin pancake-shaped too. After the MCM-22 zeolites were moved away from C-MCM-22 by HF, the zeolites are pancake-shaped with hollow.4. The space time yield of DMC over the mixed catalysts of Cu-Pd-TBAB/AC and Cu-Pd/MCM-22 could be improved effectively after the dimethyl ether was introduced to the gas-phase oxidative carbonylation of methanol. However, the catalytic performance in the co-feeding system over the bi-functional catalysts, which were prepared by using the monodisperse C-MCM-22 composite zeolites or granular C-MCM-22 composite zeolites as support, was decreased.