An Al-rich zeolite beta with *BEA topology and a Si/Al ratio as low as 6–7 was synthesized without the use of an organic structure-directing agent (OSDA) and subsequently treated by steam followed by heating with nitric acid for the purposes of dealumination, so as to prepare a catalyst. The steaming process played an important role in stabilizing the *BEA framework, presumably by repairing site defects with migrating silicon species. Steaming at around 700 °C was observed to produce optimal stabilization of the zeolite and allowed subsequent acidic dealumination while maintaining an intact framework. A second demonstration of successful OSDA-free synthesis and effective catalyst fabrication through postsynthetic modification involved the fabrication of a 12–10–10-ring zeolite having an MSE-type framework. This represented the first successful synthesis of an Al-rich MSE-type zeolite (with a Si/Al ratio as low as 6–7) using seed crystals in the absence of any OSDA. The gel composition as well as the crystallization temperature and time were optimized for the purpose of this synthesis such that a pure MSE phase could be obtained in a relatively short crystallization period of only 45 h. Longer crystallization periods and inadequate aging times gave mordenite as an impurity and as a major phase, respectively. These results offer further support for the so-called “composite building unit” hypothesis. As with the zeolite beta, direct dealumination of the MSE-type zeolite by acid treatment resulted in the collapse of the framework, which was avoided by steaming at 700 °C. After stabilization by steaming, acidic dealumination without framework collapse became possible. The dealuminated versions of the Al-rich beta and MSE-type zeolites were shown to be effective catalysts for the hexane cracking reaction, affording propylene in high selectivity. The MSE-type zeolite exhibited a particularly high level of coking resistance in addition to a significant yield of propylene, indicating that zeolites synthesized without using an OSDA show promise for industrial applications as highly selective and long-lived catalysts.

Control of the acid site distribution on MCM-68 zeolite catalysts can be achieved by the acid-treatment with nitric acid. Less coke is deposited during DTO reactions over dealuminated MCM-68 compared to the parent MCM-68 probably due to the selective removal of acid sites on the external surface of the parent MCM-68. The higher yields of propylene and butylenes are obtained with lower selectivity for ethylene and lower paraffins over dealuminated MCM-68, whereas ethylene and lower paraffins are predominant over parent MCM-68. The acid-treatment may preferentially remove the strong acid sites, and thus the retained acid sites with moderate strength mainly convert dimethyl ether into propylene and butylenes with high propylene/ethylene (P/E) molar ratio. Besides the issue of high P/E ratio, the ratio is also widely controllable by changing the reaction temperature.

An aluminum-rich MSE-type zeolite (Si/Al is as small as 7) has been successfully synthesized in a remarkably short crystallization period of only 3 days by the hydrothermal conversion of an FAU-type zeolite, presumably by the assembly of four-membered-ring (4-R) aluminosilicate oligomers supplied by the double 6-R (D6R) components of the FAU framework with the aid of the structure-directing agents and seed crystals. The dealuminated version of the aluminum-rich MSE-type zeolite showed a high level of coke durability in addition to a significant yield of propylene, which indicates that this novel zeolitic material is suitable for industrial applications as a highly selective and long-lived catalyst.

Mordenite nanocrystals of around 80 nm in length along the c axis were synthesized successfully by using a hydrophobic structure-directing agent (SDA). The nanometer-sized mordenite catalyst showed higher activity than the micron-or submicronsized versions in cumene cracking.

Pore system of MSE-type zeolite Before After Post-synthetic acid-treatment acid-site 12-ring supercage 10-ring Remarkable enhancement of catalytic activity and selectivity of MSEtype zeolite by post-synthetic modification