Zeolites have been utilized in many industrial technologies, including gas adsorption, ion exchange, separation, and catalysis for their unique porosity and high surface area. Recently, eight-membered-ring (8MR) zeolites and zeolitetype (zeotype) materials have attracted much attention, as their small pores are expected to be beneficial for selective catalysis. For example, CHA-zeotype materials such as SSZ-13 and SAPO-34 showed excellent catalytic activity for the methanol-to-olefins (MTO) reaction to provide ethylene and propylene, which are important chemicals for the polymer industry. [1][2][3][4][5] The activity of these catalysts, however, is drastically decreased owing to the deposition of coke derived from polymethylbenzene and aromatic polycyclic compounds, which are formed in a cavity in the zeolite.[6]The RTH-type zeolite, which was discovered in 1995, consists of RTH cages with 8MR openings and has twodimensional channels with aperture size of 0.41 0.38 nm and 0.56 0.25 nm, which run parallel to the a axis and the c axis, respectively. Since its discovery, this zeolite has been expected to show unique properties in the fields of catalysis and adsorption because of its unique structure. Note that the free volume of RTH-type zeolite for the MTO reaction (408 3 ) is smaller than that of CHA-type zeolites (415 3 ). [7] Considering the differences in pore dimension, size, and the free volume between RTH-and CHA-type zeolites, if the RTHtype zeolite is applied as a catalyst for the MTO reaction, the deposition of coke could be suppressed so that the catalytic performances could be improved. Unfortunately, only two examples on the RTH-type zeolites have been reported to date. One is a borosilicate zeolite, RUB-13, which is the first example of the RTH-type zeolite. This borosilicate (designated as [B]-RUB-13) can be synthesized by using a mixture of 1,2,2,6,6-pentamethylpiperidine (PMP) and ethylenediamine (EDA) as organic structure-directing agents (SDAs). [7,8] The other RTH-type zeolite is SSZ-50, which is an aluminosilicate zeolite and will be useful as a solid-acid catalyst. Unfortunately, the synthesis of SSZ-50 requires a special organic SDA, N-ethyl-N-methyl-5,7,7-trimethylazoniumbicyclo[4.1.1]octane cation, [9] which is not commercially available and is obtained through an elaborate multistep organic synthesis. The synthesis of SSZ-50 has not been remarkably advanced to date. Thus, the compositional variations in the RTH-type zeolites and their applications have been limited; especially, the incorporation of heteroatoms, the use of alternative organic SDAs, and the catalytic applications have not been investigated. Therefore, we have focused on the diversification of the RTH-type zeolites. Herein, we report the incorporation of Al atoms into [B]-RUB-13 synthesized with a mixture of PMP and EDA as SDAs. Furthermore, an organic-SDA-free synthesis route to the RTH-type zeolites has been developed. Remarkable catalytic activities of newly developed heteroatom-containing RTH-type zeolites for the MTO rea...

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The mechanism of the initial C–C bond formation on methanol to olefin (MTO) and/or methanol to hydrocarbon (MTHC) reaction were not clarified. In this paper, the reaction mechanism and the reactivity of methoxy species on H-ZSM-5 zeolite with methanol or dimethyl ether (DME), which is the initial product of MTO and MTHC reactions, were observed by infrared (IR) spectroscopy. The direct production of propene from methoxy groups and DME is evidenced on H-ZSM-5 zeolite by isotopic studies of IR observation of surface species and GC-mass analysis of products. Stepwise reactions of DME to ethene and water followed by methylation of ethene by methoxy groups were negligible during the generation of propene by the reaction of methoxy groups and DME.

Secrets revealed: IR spectroscopy shows that the recovered acidic hydroxy groups after the reaction of [D3]methoxy groups with light alkenes on zeolites are all deuterated (see scheme). The results indicate that the reaction occurs through methylene rather than methyl units.