Synthesis and Characterization of ERI-Type UZM-12 Zeolites and Their Methanol-to-Olefin Performance

Abstract

A wide variety of different linear, diquaternary alkylammonium ions have been used as supplementary crystallization structure-directing agents (SDAs) in the synthesis of UZM-12, a high-silica version of zeolite erionite, via a charge density mismatch (CDM) approach. When tetraethylammonium is used as a CDM SDA, the crystallization of UZM-12 was found to be critically dependent not only on the type of alkali metal cations added as another crystallization SDA to the synthesis mixture, but also on the size of the groups on the diquaternary ammonium ion employed and the length of its central polymethylene chain that are closely related to the dimensions of cylindrical 23-hedral [4(12)6(5)8(6)] eri cages in this small-pore zeolite. (27)Al MQ MAS NMR measurements reveal a preferential location of Al on the high-multiplicity site over the lower-multiplicity site of the UZM-12 framework. The catalytic results from the methanol-to-olefin reaction over a series of H-UZM-12 zeolites with similar acidic properties but different crystallite sizes (100-2500 nm in length) demonstrate that the nanocrystallinity (probably the ≤100 nm range) may have a detrimental effect on the activity and stability for this reaction, probably due to the fast buildup of large coke molecules on the external surface of zeolite crystallites that inhibits the methanol diffusion to intrazeolitic acid sites, rendering them ultimately inaccessible for catalysis.

Evolution of Hydrocarbon Pool over SAPO‐34 Catalyst during Methanol to Light Olefins

“…For UZM‐12, the nanocrystals of ≤100 nm reduced MTO activity and stability mainly due to coke formation rapidly on the external surfaces. The diffusion of methanol to the intrazeolitic acid site was hindered, which leads to low catalytic activity . Compared with ZSM‐5 of 3D zigzag topology, under the same condition, SAPO‐34 contained heavier coke molecule, for example pyrene …”

Cage-based small-pore catalysts for NH3-SCR prepared by combining bulky organic structure directing agents with modified zeolites as reagents

“…(28) Very recently, the preparation of the AFX and ERI zeolites was optimized by post-synthetic or direct synthesis methods, respectively. (29,30) In one case, the crystal size of the AFX material could be reduced from 3 µm down to almost 100 nm by following a postmilling recrystallization method. (29) In the other case, ERI was directly synthesized as a pure phase by using diverse flexible diquaternary alkylammonium cations as OSDAs, resulting in materials with a Si/Al molar ratio of ~ 5.5, and crystal sizes from 400 nm to 2 µm.…”

“…(29) In the other case, ERI was directly synthesized as a pure phase by using diverse flexible diquaternary alkylammonium cations as OSDAs, resulting in materials with a Si/Al molar ratio of ~ 5.5, and crystal sizes from 400 nm to 2 µm. (30) To the best of our knowledge, these materials have not yet been tested as catalysts in the selective catalytic reduction of NOx using ammonia.…”

Toward Greener and Designed Synthesis of Zeolite Materials

“…The concept of CDM approach was first developed by researchers at UOP in the 2000s, which was designed to develop cooperation between two or more different SDAs during the crystallization process of zeolites. In 2010, Hong and coworkers synthesized aluminosilicate zeolite UZM-12 (ERI) zeolite by the cooperative effects of TEA + , alkali metal and diquaternary ammonium cations in crystallization to direct zeolite frameworks [88]. Early in 2004, Wilson and coworkers demonstrated the template cooperation in the synthesis of aluminosilicate zeolite UZM-9 (LTA) [86,87].…”