Effect of SiO2/AL2O3 ratio on synthesis of MCM-22, UTM-1 and kenyaite

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 SiO2/Al2O3 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 SiO2/Al2O3 ratio in the gel was an important factor affecting the product composition. When n(SiO2)/n(Al2O3) = 30similar to50, the product was MCM-22, and when n(SiO2)/n(Al2O3) = 71similar to190, the product was a mixture of MCM-22 and kenyalte. The fraction of MCM-22 decreased while that of kenyalte increased with the decrease in alumina content. When n (SiO2) In (Al1O3) = 228 similar to 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 kenyalte. In the synthesis of UTM-1, a shorter induction time was observed. MCM-22, UTM-1 and kenyalte could be distinguished from each other by SEM though they all had platelet morphology.