Factors Governing the Formation of Hierarchically and Sequentially Intergrown MFI Zeolites by Using Simple Diquaternary Ammonium Structure-Directing Agents

Sye Hoe Keoh; Watcharop Chaikittisilp; Koki Muraoka; Rino R. Mukti; Atsushi Shimojima; Prashant Kumar; Michael Tsapatsis; Tatsuya Okubo

doi:10.1021/acs.chemmater.6b03887

Factors Governing the Formation of Hierarchically and Sequentially Intergrown MFI Zeolites by Using Simple Diquaternary Ammonium Structure-Directing Agents

Sye Hoe Keoh, Watcharop Chaikittisilp, Koki Muraoka, Rino R. Mukti, Atsushi Shimojima, Prashant Kumar, Michael Tsapatsis, Tatsuya Okubo

Chemical Engineering and Materials Science

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Abstract

Zeolites with hierarchical structures are of particular interest because such structures can improve molecular diffusion, particularly that of bulky molecules. N,N,N,N′,N′,N′-Hexapropylpentanediammonium cations (Pr₆-diquat-5), a simple diquaternary ammonium organic structure-directing agent (OSDA), can direct the formation of hierarchically and sequentially intergrown MFI zeolites without employing any mesoporogens. In this paper, the effects of OSDAs having structures similar to Pr₆-diquat-5 but different lengths of alkyl spacers and/or different substituting groups on the phase selectivity and morphology of the resulting zeolites are presented. It was revealed that the number of carbon atoms between two charged nitrogens in the OSDAs significantly affected the intergrowth and morphology of the crystals formed. In addition, the propyl-substituted OSDAs were found to be very selective to the formation of MFI zeolite, whereas the butyl-substituted OSDAs were not. For Pr₆-diquat-5, the condition for the formation of hierarchically and sequentially intergrown MFI zeolites was somewhat narrow with the optimized molar composition of 1 SiO₂:0.2 Pr₆-diquat-5:0.375-0.500 KOH:200 H₂O:4 EtOH. Defect lines observed on the obtained zeolite crystals by a transmission electron microscope were considered to be connectors for such intergrowths. The unique intergrowth formed by Pr₆-diquat-5 was surmised to be due to the unusual fitting of Pr₆-diquat-5 inside the channels of MFI zeolite, which was explained by comparing molecular dimensions and stabilization energies of each OSDA.

Original language	English (US)
Pages (from-to)	8997-9007
Number of pages	11
Journal	Chemistry of Materials
Volume	28
Issue number	24
DOIs	https://doi.org/10.1021/acs.chemmater.6b03887
State	Published - Dec 27 2016

Bibliographical note

Funding Information:
S.H.K. thanks Panasonic Scholarship and Honjo International Scholarship Foundation for financial support during his graduate study. This work was supported in part by Grant-in- Aids for Scientific Research (A) (JSPS KAKENHI Grant Number: 26249118) and for Young Scientists (B) (JSPS KAKENHI Grant Number: 16K18284) by the Japan Society for the Promotion of Science (JSPS). Parts of this work were conducted at the Center for Nano Lithography andAnalysis at The University of Tokyo, which is supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), and at the University of Minnesota Characterization Facility, which receives partial support from the NSF through the NNIN program.

Publisher Copyright:
© 2016 American Chemical Society.

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title = "Factors Governing the Formation of Hierarchically and Sequentially Intergrown MFI Zeolites by Using Simple Diquaternary Ammonium Structure-Directing Agents",

abstract = "Zeolites with hierarchical structures are of particular interest because such structures can improve molecular diffusion, particularly that of bulky molecules. N,N,N,N′,N′,N′-Hexapropylpentanediammonium cations (Pr6-diquat-5), a simple diquaternary ammonium organic structure-directing agent (OSDA), can direct the formation of hierarchically and sequentially intergrown MFI zeolites without employing any mesoporogens. In this paper, the effects of OSDAs having structures similar to Pr6-diquat-5 but different lengths of alkyl spacers and/or different substituting groups on the phase selectivity and morphology of the resulting zeolites are presented. It was revealed that the number of carbon atoms between two charged nitrogens in the OSDAs significantly affected the intergrowth and morphology of the crystals formed. In addition, the propyl-substituted OSDAs were found to be very selective to the formation of MFI zeolite, whereas the butyl-substituted OSDAs were not. For Pr6-diquat-5, the condition for the formation of hierarchically and sequentially intergrown MFI zeolites was somewhat narrow with the optimized molar composition of 1 SiO2:0.2 Pr6-diquat-5:0.375-0.500 KOH:200 H2O:4 EtOH. Defect lines observed on the obtained zeolite crystals by a transmission electron microscope were considered to be connectors for such intergrowths. The unique intergrowth formed by Pr6-diquat-5 was surmised to be due to the unusual fitting of Pr6-diquat-5 inside the channels of MFI zeolite, which was explained by comparing molecular dimensions and stabilization energies of each OSDA.",

author = "Keoh, {Sye Hoe} and Watcharop Chaikittisilp and Koki Muraoka and Mukti, {Rino R.} and Atsushi Shimojima and Prashant Kumar and Michael Tsapatsis and Tatsuya Okubo",

note = "Funding Information: S.H.K. thanks Panasonic Scholarship and Honjo International Scholarship Foundation for financial support during his graduate study. This work was supported in part by Grant-in- Aids for Scientific Research (A) (JSPS KAKENHI Grant Number: 26249118) and for Young Scientists (B) (JSPS KAKENHI Grant Number: 16K18284) by the Japan Society for the Promotion of Science (JSPS). Parts of this work were conducted at the Center for Nano Lithography andAnalysis at The University of Tokyo, which is supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), and at the University of Minnesota Characterization Facility, which receives partial support from the NSF through the NNIN program. Publisher Copyright: {\textcopyright} 2016 American Chemical Society.",

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T1 - Factors Governing the Formation of Hierarchically and Sequentially Intergrown MFI Zeolites by Using Simple Diquaternary Ammonium Structure-Directing Agents

AU - Keoh, Sye Hoe

AU - Chaikittisilp, Watcharop

AU - Muraoka, Koki

AU - Mukti, Rino R.

AU - Shimojima, Atsushi

AU - Kumar, Prashant

AU - Tsapatsis, Michael

AU - Okubo, Tatsuya

N1 - Funding Information: S.H.K. thanks Panasonic Scholarship and Honjo International Scholarship Foundation for financial support during his graduate study. This work was supported in part by Grant-in- Aids for Scientific Research (A) (JSPS KAKENHI Grant Number: 26249118) and for Young Scientists (B) (JSPS KAKENHI Grant Number: 16K18284) by the Japan Society for the Promotion of Science (JSPS). Parts of this work were conducted at the Center for Nano Lithography andAnalysis at The University of Tokyo, which is supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), and at the University of Minnesota Characterization Facility, which receives partial support from the NSF through the NNIN program. Publisher Copyright: © 2016 American Chemical Society.

PY - 2016/12/27

Y1 - 2016/12/27

N2 - Zeolites with hierarchical structures are of particular interest because such structures can improve molecular diffusion, particularly that of bulky molecules. N,N,N,N′,N′,N′-Hexapropylpentanediammonium cations (Pr6-diquat-5), a simple diquaternary ammonium organic structure-directing agent (OSDA), can direct the formation of hierarchically and sequentially intergrown MFI zeolites without employing any mesoporogens. In this paper, the effects of OSDAs having structures similar to Pr6-diquat-5 but different lengths of alkyl spacers and/or different substituting groups on the phase selectivity and morphology of the resulting zeolites are presented. It was revealed that the number of carbon atoms between two charged nitrogens in the OSDAs significantly affected the intergrowth and morphology of the crystals formed. In addition, the propyl-substituted OSDAs were found to be very selective to the formation of MFI zeolite, whereas the butyl-substituted OSDAs were not. For Pr6-diquat-5, the condition for the formation of hierarchically and sequentially intergrown MFI zeolites was somewhat narrow with the optimized molar composition of 1 SiO2:0.2 Pr6-diquat-5:0.375-0.500 KOH:200 H2O:4 EtOH. Defect lines observed on the obtained zeolite crystals by a transmission electron microscope were considered to be connectors for such intergrowths. The unique intergrowth formed by Pr6-diquat-5 was surmised to be due to the unusual fitting of Pr6-diquat-5 inside the channels of MFI zeolite, which was explained by comparing molecular dimensions and stabilization energies of each OSDA.

AB - Zeolites with hierarchical structures are of particular interest because such structures can improve molecular diffusion, particularly that of bulky molecules. N,N,N,N′,N′,N′-Hexapropylpentanediammonium cations (Pr6-diquat-5), a simple diquaternary ammonium organic structure-directing agent (OSDA), can direct the formation of hierarchically and sequentially intergrown MFI zeolites without employing any mesoporogens. In this paper, the effects of OSDAs having structures similar to Pr6-diquat-5 but different lengths of alkyl spacers and/or different substituting groups on the phase selectivity and morphology of the resulting zeolites are presented. It was revealed that the number of carbon atoms between two charged nitrogens in the OSDAs significantly affected the intergrowth and morphology of the crystals formed. In addition, the propyl-substituted OSDAs were found to be very selective to the formation of MFI zeolite, whereas the butyl-substituted OSDAs were not. For Pr6-diquat-5, the condition for the formation of hierarchically and sequentially intergrown MFI zeolites was somewhat narrow with the optimized molar composition of 1 SiO2:0.2 Pr6-diquat-5:0.375-0.500 KOH:200 H2O:4 EtOH. Defect lines observed on the obtained zeolite crystals by a transmission electron microscope were considered to be connectors for such intergrowths. The unique intergrowth formed by Pr6-diquat-5 was surmised to be due to the unusual fitting of Pr6-diquat-5 inside the channels of MFI zeolite, which was explained by comparing molecular dimensions and stabilization energies of each OSDA.

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Factors Governing the Formation of Hierarchically and Sequentially Intergrown MFI Zeolites by Using Simple Diquaternary Ammonium Structure-Directing Agents

Abstract

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