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  1. Book ; Online ; Thesis: Synthesis of oxymethylene ethers

    Grünert, Anna [Verfasser] / Schüth, Ferdi [Gutachter] / Muhler, Martin [Gutachter]

    2020  

    Author's details Anna Grünert ; Gutachter: Ferdi Schüth, Martin Muhler ; Fakultät für Chemie und Biochemie
    Keywords Technische Chemie ; Technical Chemistry
    Subject code sg660
    Language English
    Publisher Ruhr-Universität Bochum
    Publishing place Bochum
    Document type Book ; Online ; Thesis
    Database Digital theses on the web

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  2. Article: Proton Mobility, Intrinsic Acid Strength, and Acid Site Location in Zeolites Revealed by Varying Temperature Infrared Spectroscopy and Density Functional Theory Studies

    Losch, Pit / Joshi, Hrishikesh R / Vozniuk, Olena / Grünert, Anna / Ochoa-Hernández, Cristina / Jabraoui, Hicham / Badawi, Michael / Schmidt, Wolfgang

    Journal of the American Chemical Society. 2018 Nov. 29, v. 140, no. 50

    2018  

    Abstract: The intrinsic Brønsted acid strength in solid acids relates to the energy required to separate a proton from a conjugate base, for example a negatively charged zeolite framework. The reliable characterization of zeolites’ intrinsic acidity is fundamental ...

    Abstract The intrinsic Brønsted acid strength in solid acids relates to the energy required to separate a proton from a conjugate base, for example a negatively charged zeolite framework. The reliable characterization of zeolites’ intrinsic acidity is fundamental to the understanding of acid catalysis and setting in relation solid Brønsted acids with their activity and selectivity. Here, we report an infrared spectroscopic study with partial isotopic deuterium exchange of a series of 15 different acidic aluminosilicate materials, including ZSM-5 zeolites with very few defects. Varying Temperature Infrared spectroscopy (VTIR) permitted estimating activation energies for proton diffusion. Two different proton transfer mechanisms have been distinguished for two different temperature ranges. Si-rich zeolites appeared to be promising proton-transfer materials (Eact. < 40 kJ mol–1) at temperatures above 150 °C (423 K). Further, a linear bathochromic shift of the Si–(OD)–Al stretching vibration as a function of temperature was observed. It can be assumed that this red-shift is related to the intrinsic O–(H/D) bond strength. This observation allowed the extrapolation and estimation of precise v(O–D)@0 K values, which could be attributed to distinct crystallographic locations through Density Functional Theory (DFT) calculations. The developed method was used to reliably determine the likelihood of the position of a proton in ZSM-5 zeolites under catalytically relevant conditions (T > 423 K), which has so far never been achieved by any other technique.
    Keywords Bronsted acids ; acidity ; activation energy ; aluminum ; catalytic activity ; density functional theory ; deuterium ; energy ; infrared spectroscopy ; silicon ; spectral analysis ; temperature ; vibration ; zeolites
    Language English
    Dates of publication 2018-1129
    Size p. 17790-17799.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.8b11588
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

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  3. Article ; Online: Proton Mobility, Intrinsic Acid Strength, and Acid Site Location in Zeolites Revealed by Varying Temperature Infrared Spectroscopy and Density Functional Theory Studies.

    Losch, Pit / Joshi, Hrishikesh R / Vozniuk, Olena / Grünert, Anna / Ochoa-Hernández, Cristina / Jabraoui, Hicham / Badawi, Michael / Schmidt, Wolfgang

    Journal of the American Chemical Society

    2018  Volume 140, Issue 50, Page(s) 17790–17799

    Abstract: The intrinsic Brønsted acid strength in solid acids relates to the energy required to separate a proton from a conjugate base, for example a negatively charged zeolite framework. The reliable characterization of zeolites' intrinsic acidity is fundamental ...

    Abstract The intrinsic Brønsted acid strength in solid acids relates to the energy required to separate a proton from a conjugate base, for example a negatively charged zeolite framework. The reliable characterization of zeolites' intrinsic acidity is fundamental to the understanding of acid catalysis and setting in relation solid Brønsted acids with their activity and selectivity. Here, we report an infrared spectroscopic study with partial isotopic deuterium exchange of a series of 15 different acidic aluminosilicate materials, including ZSM-5 zeolites with very few defects. Varying Temperature Infrared spectroscopy (VTIR) permitted estimating activation energies for proton diffusion. Two different proton transfer mechanisms have been distinguished for two different temperature ranges. Si-rich zeolites appeared to be promising proton-transfer materials ( E
    Language English
    Publishing date 2018-12-07
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.8b11588
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Bonn / Germany

    Z 4' 55/32: Show issues
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    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

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