Studies on the crystallization process of BEA/MOR co-crystalline zeolite

BEA/MOR co-crystalline zeolite was synthesized using tetraethylammonium-fluorides as composite templates. The crystallization process of BEA/MOR co-crystalline zeolite was systematically investigated based on XRD, ICP, SEM, TGA, and nitrogen adsorption characterizations. Through the XRD patterns of the samples with different crystallization times, the BEA and MOR phases did not appear simultaneously in the crystallization process. The BEA phase was the favored product at the beginning of crystallization, whereafter the MOR phase emerged, and the BEA/MOR co-crystalline zeolite was gradually formed. The morphology of obtained particles changed a little during the crystallization process, but the granularity distribution range broadened. Asymmetry of BEA/MOR co-crystalline zeolite particles led to uneven distribution of the mesopores. It is showed that the pore size distribution of the samples with more than 90-h crystallization period exhibited bimodal mesopores distribution, and the pore sizes of the extra mesopores were 4.9 and 5.6 nm, respectively. Based on these results, the crystallization mechanism of BEA/MOR co-crystalline zeolite in tetraethylammonium-fluoride binary templates was roughly proposed.