High Potential of Interzeolite Conversion Method for Zeolite Synthesis

Sano, Tsuneji; Itakura, Masaya; Sadakane, Masahiro

doi:10.1627/jpi.56.183

Cited by 102 publications

(95 citation statements)

References 62 publications

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“…Herein, we demonstrate the direct transformation of USY (FAU) to ZSM‐5 in the absence of organics and without the use of ZSM‐5 seeds. This specific transformation involving two zeolites lacking a common CBU was previously deemed improbable . The FAU‐to‐MFI interzeolite transformation is accomplished using a growth medium that favors OSDA‐free ZSM‐5 crystallization.…”

Section: Figurementioning

confidence: 99%

Organic‐Free Interzeolite Transformation in the Absence of Common Building Units

Qin

Jain

Hernández

et al. 2019

Chemistry A European J

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Zeolite crystals can be used as seeds or aluminosilicate sources in syntheses to control polymorphs and/or reduce the quantity of organics used as structure‐directing agents. A frequently invoked hypothesis for interzeolite transformations is that zeolites share some underlying similarity in structure, most notably in cases pertaining to organic‐free syntheses. Herein, we show for the first time that ZSM‐5 (MFI) can be directly obtained from USY (FAU) through an interzeolite transformation between parent–daughter structures lacking common building units in the absence of a structure‐directing agent and seeds. We show that interzeolite transformation leads to a crystalline product with fewer defects. Our findings also reveal that ZSM‐5 is a metastable intermediate that undergoes further transformation to mordenite (MOR) and quartz. The MFI‐to‐MOR transition is counter to reported trends for which transformations lead to structures with reduced molar volume. Herein, we propose mechanistic arguments that suggest the driving force for interzeolite transformation is more complex than guidelines posited in the literature.

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Section: Figurementioning

confidence: 99%

Organic‐Free Interzeolite Transformation in the Absence of Common Building Units

Qin

Jain

Hernández

et al. 2019

Chemistry A European J

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“…[10,11] If this is so, it could also be expected that the lower dissolution rates observed for crystalline molecular sieves acting as Si and Al sources, could preclude the excessive dissolution towards monomeric silicate species that would remain in solution, favoring the efficient synthesis of SSZ-39 with high solid yields when combined with simple alkyl-substituted cyclic quaternary ammonium cations acting as OSDAs, such as N,Ndimethyl-3,5-dimethylpiperidinium.…”

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confidence: 99%

“…[10] The reason for that is because these crystalline sources can intensely change the nucleation/crystallization driving forces compared to other amorphous silicoaluminate precursors.…”

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confidence: 99%

Efficient synthesis of the Cu-SSZ-39 catalyst for DeNOx applications

et al. 2015

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The use of small pore zeolites with large cavities has been reported for relevant applications in catalysis or gas separation.[1] One of the most important applications of these materials as catalysts is the selective catalytic reduction (SCR) of nitrogen oxides (NO x ), where copper-containing zeolites with small pore sizes show excellent activities to remove these hazardous compounds produced during combustion in diesel engines. [1,2] Interestingly, these small-pore zeolites show higher hydrothermal stability compared to other zeolitic materials presenting larger pore sizes, such as Cu-ZSM-5 or Cu-Beta. [3] The particular stabilization of the Cu 2+ cations within the double 6-rings (D6Rs) present in some structures of these small pore zeolites, i.e. chabazite (CHA structure), has been claimed as a plausible reason for their higher hydrothermal stability.[4]Another zeolite with related structural properties to chabazite is SSZ-39 (AEI structure), which is an aluminosilicate with large cages connected by a three-directional small 8-ring (8-R) pore system, and also with D6R as secondary building units in its structure.[5]Recently, we have reported that Cu-exchanged SSZ-39 zeolite is an active and hydrothermally stable catalyst for the SCR of NO x with ammonia, showing even better catalytic performance than Cu-exchanged CHA.[6]The preferred synthesis procedure of SSZ-39 requires the use of simple alkylsubstituted cyclic quaternary ammonium cations as organic structure directing agents (OSDAs) in alkaline conditions. [7] These organic cations could be easily prepared from commercially-available pyridine precursors, [8] making attractive the use of these OSDAs for the synthesis of the SSZ-39 from an economic point of view. Unfortunately, this methodology can afford the preparation of the SSZ-39 in low solid yields (lower than 50%), since the final crystalline solids show much lower Si/Al ratios than the Si/Al ratios initially introduced in the synthesis gels, [6,7,8] indicating that most of the Si species remain in solution after the crystallization procedure. This fact limits the potential use of SSZ-39 in commercial applications.Recently, the synthesis of the high silica AEI zeolite with high solid yields (above 80%) has been reported using USY zeolite as silicon source and tetraethylphosphonium (TEP)cations as OSDA. [9] Although this achievement is highly relevant in terms of the optimization of the SSZ-39 synthesis, the use of P-based OSDAs still presents some 3 important drawbacks. On one hand, phosphine-derived organic molecules show important environmental and health hazards, and, on the other hand, the complete removal of the phosphorous-species entrapped within the zeolitic cavities is very difficult, especially within small pore zeolites, and their calcination process requires high temperatures and hydrogen atmospheres for the complete decomposition/elimination of these compounds.[9]It is worth mentioning that in the last years the use of pre-formed crystalline zeolitic precursors to synthesize different...

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“…To meet the mass balance, the initial reactant molar composition was set as follows: 25 structure, the zeolite transformation from lower to higher SiO 2 / Al 2 O 3 . XRD identified the FAU-MWW co-existing zeolites as intermediate states during the topology reconstruction, and the resulting phase as pure MWW structure zeolite.…”

Section: Topology Reconstruction From Fau To Mww Structurementioning

confidence: 99%

“…Another type of ''zeolite to zeolite'' transformation, the so-called ''interzeolite http://dx.doi.org/10.1016/j.micromeso.2014.08.045 1387-1811/Ó 2014 Elsevier Inc. All rights reserved. conversion'' [19][20][21][22][23][24][25], proceeded as following sequence: starting zeolites ? amorphous phase (XRD) ?…”

Section: Introductionmentioning

confidence: 99%