MAPO-5 molecular sieves from alkylimidazolium bromide ionic liquids

Creators: Citrak, Susan C.¹; Ehlke, Beatriz¹; Zones, Stacey I.²; Xie, Dan²; Hwang, Son-Jong³; Ichimura, Andrew S.⁴; Zhang, Linjuan^{5, 6}; Xi, Shibo⁷; Oliver, Scott R.J.¹

1. University of California, Santa Cruz
2. Chevron (United States)
3. California Institute of Technology
4. San Francisco State University
5. Shanghai Institute of Applied Physics
6. University of Chinese Academy of Sciences
7. Agency for Science, Technology and Research

Abstract

The ionic liquids diisopropylimidazolium bromide (DIPI) and diisobutylimidazolium bromide (DIBU) were used both as solvents and structure-directing agents (SDAs) to obtain AlPO₄-5 and MnAPO-5 (Mn-AFI) molecular sieves. For increasing level of manganese, DIBU always yielded pure-phase Mn-AFI whereas DIPI led to amorphous product when more than 0.13 eq of Mn was added. Varying amounts of water, HF and metal led to AFI, cristobalite or tridymite phases. We also explored the use of nickel as the metal dopant, and although AFI phase were obtained under certain conditions, no framework incorporation of the metal was observed. Because of the vanishingly low vapor pressure of the ILs, the synthesis does not carry the risk of pressure build-up. The ILs were easily and fully recyclable and used for multiple syntheses. The MnAPO-5 material was characterized with powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), electron paramagnetic resonance (EPR), multinuclear solid-state nuclear magnetic resonance (SS-NMR) and X-ray absorption fine structure (XAFS). These findings provide new insight into the ionothermal synthesis of metal-doped AFI frameworks with possible implications in catalytic applications.

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Acknowledgement

Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund in support of this research (grant No. 60870-ND10). The authors thank Dr. Graham Roseman in the group of Professor Glenn Millhauser, University of California, Santa Cruz, Department of Chemistry & Biochemistry for EPR data collection and analysis. The XAFCA beamline at SSLS was supported by the ‘Transformational Technologies for Clean Energy and Demonstration’ Strategic Priority Research Program of the Chinese Academy of Sciences (grant No. XDA21000000).

Contributions

Susan C. Citrak: Writing – review & editing, Writing – original draft, Visualization, Validation, Methodology, Investigation, Formal analysis, Data curation. Beatriz Ehlke: Writing – review & editing, Writing – original draft, Visualization, Validation, Investigation, Formal analysis, Data curation. Stacey I. Zones: Writing – review & editing, Writing – original draft, Visualization, Validation, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Dan Xie: Formal analysis, Data curation. Son-Jong Hwang: Formal analysis, Data curation. Andrew S. Ichimura: Formal analysis, Data curation. Linjuan Zhang: Formal analysis, Data curation. Shibo Xi: Formal analysis, Data curation. Scott R.J. Oliver: Writing – review & editing, Writing – original draft, Validation, Supervision, Project administration, Methodology, Funding acquisition, Formal analysis, Conceptualization.

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