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Effect of SiO_2/Al_2O_3 Ratio on Synthesis of MCM-22, UTM-1 and Kenyaite

LIU Ziyu 1,2 , LIU Zhongmin 1* , QI Yue 1, XU Lei 1, HE Yanli 1, YANG Yue 1 , ZHANG Yangyang 1,2 (1 Dalian Institute of Chemical Physics, The Chinese Academy of Sciences, Dalian 116023, Liaoning, China; 2 Graduate School of The Chinese Academy of Sciences, Beijing 100039, China)  
The unique porous network of MCM 22 suggests its potential use in a variety of catalytic processes. However, it is difficult to synthesize MCM 22 with high silica because the increase of SiO 2/Al 2O 3 ratio in the gel often leads to contaminated zeolites. The synthesis of MCM 22, UTM 1 and kenyaite by rotating hydrothermal crystallization method, using fumed silica, sodium aluminate and hexamethyleneimide (HMI) as raw materials, was investigated. It was found that SiO 2/Al 2O 3 ratio in the gel was an important factor affecting the product composition. When n (SiO 2) / n (Al 2O 3) =30~50, the product was MCM 22, and when n (SiO 2) / n (Al 2O 3) =71~190, the product was a mixture of MCM 22 and kenyaite. The fraction of MCM 22 decreased while that of kenyaite increased with the decrease in alumina content. When n (SiO 2) / n (Al 2O 3) =228~609, 8 membered ring UTM 1 was obtained. Pure layered silicate kenyaite was obtained in the absence of alumina in the gel. The presence of alumina in the gel system was critical for the formation of MCM 22 and UTM 1, but it was not the case for kenyaite. In the synthesis of UTM 1, a shorter induction time was observed. MCM 22, UTM 1 and kenyaite could be distinguished from each other by SEM though they all had platelet morphology.
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