A study on microwave-assisted synthesis of MCM-22 zeolite

MCM-22 zeolite has been synthesized successfully from hydrogels with microwave (MW) heating method, the process of which was compared with that of conventional hydrothermal synthesis (HTS). The MW-assisted heating showed a significant advantage that it reduced greatly the crystallization time. For instance, it led to a fully crystallized MCM-22 within 29 h in contrast to 5 d required by HTS synthesis. Microwave- assisted MCM-22 had good quality in phase purity, crystallinity, textual properties and incorporated tetrahedral Al ions as evidence by the characterizations with XRD, SEM, FT-IR, ICP and Al²⁷ MAS NMR techniques. The paramount role of structure-directing agent in the MW-assisted process has been investigated to give a possible mechanism of crystallization. Moreover, by adding a small amount of alcohols in the initial gels, the crystallization time was further shortened to 24 h.