Ultrafast, OSDA-free synthesis of mordenite zeolite

Abstract

We present herein an ultrafast, organic structure-directing agent (OSDA)-free synthesis of mordenite zeolite in a tubular reactor capable of fast heating. Using a typical Na₂O/SiO₂/Al₂O₃ system, the synthesis time was shortened to 10 min, which is much shorter than the time required by conventional methods (tens of hours). The addition of milled seeds, which have a smaller crystal size (200 nm), was found to be more effective in enhancing the crystallization than the micrometer-sized raw seeds (2 μm). The fast-synthesized mordenite possesses properties similar to those of mordenite synthesized by conventional methods in terms of crystallinity while having a comparably small crystal size. In addition, the effects of the alkalinity and SiO₂/Al₂O₃ ratio of the initial reactant mixture on the crystallization rate were evaluated, but no significant effects were observed. On the contrary, the yield and SiO₂/Al₂O₃ ratio of the product were dependent on the alkalinity and SiO₂/Al₂O₃ ratio of the initial reactant mixture. Based on these observations, the crystallization behavior of mordenite, obtained from an ultrafast, OSDA-free synthesis method, is discussed.