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Title: Mechanism of Phenol Alkylation in Zeolite H-BEA Using In Situ Solid-State NMR Spectroscopy

Abstract

Alkylation of phenolic compounds in the liquid phase is of fundamental and practical importance to the conversion of biomass-derived feedstocks into fuels and chemicals. In this work, the reaction mechanism for phenol alkylation with cyclohexanol and cyclohexene has been investigated on a commercial HBEA zeolite by in situ 13C MAS NMR, using decalin as the solvent. From the variable temperature 13C MAS NMR measurements of phenol and cyclohexanol adsorption on HBEA from decalin solutions, it is shown that the two molecules have similar adsorption strength in the HBEA pore. Phenol alkylation with cyclohexanol, however, becomes significantly measurable only after cyclohexanol is largely converted to cyclohexene via dehydration. This is in contrast to the initially rapid alkylation of phenol when using cyclohexene as the co-reactant. 13C isotope scrambling results demonstrate that the electrophile, presumably cyclohexyl carbenium ion, is directly formed in a protonation step when cyclohexene is the co-reactant, but requires re-adsorption of the alcohol dehydration product, cyclohexene, when cyclohexanol dimer is the dominant surface species (e.g., at 0.5 M cyclohexanol concentration) that is unable to generate carbenium ion. At the initial reaction stage of phenol-cyclohexanol alkylation on HBEA, the presence of the cyclohexanol dimer species hinders the adsorption of cyclohexenemore » at the Brønsted acid site and the subsequent activation of the more potent electrophile (carbenium ion). Isotope scrambling data also show that intramolecular rearrangement of cyclohexyl phenyl ether, the O-alkylation product, does not significantly contribute to the formation of C-alkylation products.« less

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1];  [1];  [2]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [3]
  1. Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
  2. Department of Chemistry and Catalysis Research Center, TU München, Lichtenbergstrasse 4, 85748 Garching, Germany
  3. Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States; Department of Chemistry and Catalysis Research Center, TU München, Lichtenbergstrasse 4, 85748 Garching, Germany
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1372006
Report Number(s):
PNNL-SA-122818
Journal ID: ISSN 0002-7863; 48810; KC0302010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 139; Journal Issue: 27
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Environmental Molecular Sciences Laboratory

Citation Formats

Zhao, Zhenchao, Shi, Hui, Wan, Chuan, Hu, Mary Y., Liu, Yuanshuai, Mei, Donghai, Camaioni, Donald M., Hu, Jian Zhi, and Lercher, Johannes A.. Mechanism of Phenol Alkylation in Zeolite H-BEA Using In Situ Solid-State NMR Spectroscopy. United States: N. p., 2017. Web. doi:10.1021/jacs.7b02153.
Zhao, Zhenchao, Shi, Hui, Wan, Chuan, Hu, Mary Y., Liu, Yuanshuai, Mei, Donghai, Camaioni, Donald M., Hu, Jian Zhi, & Lercher, Johannes A.. Mechanism of Phenol Alkylation in Zeolite H-BEA Using In Situ Solid-State NMR Spectroscopy. United States. doi:10.1021/jacs.7b02153.
Zhao, Zhenchao, Shi, Hui, Wan, Chuan, Hu, Mary Y., Liu, Yuanshuai, Mei, Donghai, Camaioni, Donald M., Hu, Jian Zhi, and Lercher, Johannes A.. 2017. "Mechanism of Phenol Alkylation in Zeolite H-BEA Using In Situ Solid-State NMR Spectroscopy". United States. doi:10.1021/jacs.7b02153.
@article{osti_1372006,
title = {Mechanism of Phenol Alkylation in Zeolite H-BEA Using In Situ Solid-State NMR Spectroscopy},
author = {Zhao, Zhenchao and Shi, Hui and Wan, Chuan and Hu, Mary Y. and Liu, Yuanshuai and Mei, Donghai and Camaioni, Donald M. and Hu, Jian Zhi and Lercher, Johannes A.},
abstractNote = {Alkylation of phenolic compounds in the liquid phase is of fundamental and practical importance to the conversion of biomass-derived feedstocks into fuels and chemicals. In this work, the reaction mechanism for phenol alkylation with cyclohexanol and cyclohexene has been investigated on a commercial HBEA zeolite by in situ 13C MAS NMR, using decalin as the solvent. From the variable temperature 13C MAS NMR measurements of phenol and cyclohexanol adsorption on HBEA from decalin solutions, it is shown that the two molecules have similar adsorption strength in the HBEA pore. Phenol alkylation with cyclohexanol, however, becomes significantly measurable only after cyclohexanol is largely converted to cyclohexene via dehydration. This is in contrast to the initially rapid alkylation of phenol when using cyclohexene as the co-reactant. 13C isotope scrambling results demonstrate that the electrophile, presumably cyclohexyl carbenium ion, is directly formed in a protonation step when cyclohexene is the co-reactant, but requires re-adsorption of the alcohol dehydration product, cyclohexene, when cyclohexanol dimer is the dominant surface species (e.g., at 0.5 M cyclohexanol concentration) that is unable to generate carbenium ion. At the initial reaction stage of phenol-cyclohexanol alkylation on HBEA, the presence of the cyclohexanol dimer species hinders the adsorption of cyclohexene at the Brønsted acid site and the subsequent activation of the more potent electrophile (carbenium ion). Isotope scrambling data also show that intramolecular rearrangement of cyclohexyl phenyl ether, the O-alkylation product, does not significantly contribute to the formation of C-alkylation products.},
doi = {10.1021/jacs.7b02153},
journal = {Journal of the American Chemical Society},
number = 27,
volume = 139,
place = {United States},
year = 2017,
month = 6
}
  • The oligomerization reactions of propene on zeolite catalyst HY have been studied in detail by in situ variable-temperature /sup 13/C solid-state NMR with cross polarization (CP) and magic-angle spinning (MAS). Propene is shown to be highly mobile in the zeolite at temperatures far below the onset of chemical reactivity. Alkoxy species formed between protonated alkenes and zeolite framework oxygens are found to be important long-lived intermediates in the reactions. Simple secondary or tertiary carbocations either do not exist as free ions in the zeolite at low temperature or are so transient that they are not detected by NMR, even atmore » temperatures as low as 163 K. There is, however, evidence for long-lived alkyl-substituted cyclopentenyl carbocations, which are formed as free ions in the zeolite at room temperature. These carbocations do not form until all of the propene is consumed and hence do not play a significant role in the oligomerization reactions. A detailed mechanism is proposed to account for all of the experimental observations. Novel experimental techniques are introduced which will be applicable to the study of many highly reactive catalyst/adsorbate systems.« less
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  • In situ high energy X-ray diffraction (HEXRD) and in situ X-ray absorption near edge spectroscopy (XANES) were carried out to understand the soild state synthesis of Na xMnO 2, with particular interest on the synthesis of P2 type Na 2/3MnO 2. It was found that there were multi intermediate phases formed before NaMnO 2 appeared at about 600 °C. And the final product after cooling process is a combination of O'3 NaMnO 2 with P2 Na 2/3MnO 2. A P2 type Na 2/3MnO 2 was synthesized at reduced temperature (600 °C). The influence of Na 2CO 3 impurity on themore » electrochemical performance of P2 Na 2/3MnO 2 was thoroughly investigated in our work. It was found that the content of Na 2CO 3 can be reduced by optimizing Na 2CO 3/MnCO 3 ratio during the solid state reaction or other post treatment such as washing with water. Lastly, we expected our results could provide a good guide for future development of high performance cathode materials for sodium-ion batteries.« less