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The Low‐Temperature Oxidation of Propane by using H 2 O 2 and Fe/ZSM‐5 Catalysts: Insights into the Active Site and Enhancement of Catalytic Turnover Frequencies
Author(s) -
Peneau Virginie,
Armstrong Robert D.,
Shaw Greg,
Xu Jun,
Jenkins Robert L.,
Morgan David J.,
Dimitratos Nikolaos,
Taylor Stuart H.,
Zanthoff Horst W.,
Peitz Stefan,
Stochniol Guido,
He Qian,
Kiely Christopher J.,
Hutchings Graham J.
Publication year - 2017
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201601241
Subject(s) - catalysis , chemistry , propane , aqueous solution , zeolite , inorganic chemistry , alkane , hydrogen peroxide , zsm 5 , x ray photoelectron spectroscopy , microporous material , magic angle spinning , desorption , temperature programmed reduction , adsorption , nuclear magnetic resonance spectroscopy , chemical engineering , organic chemistry , engineering
Fe‐containing ZSM‐5 catalysts are reported to be efficient catalysts for the partial oxidation of propane to oxygenated products at reaction temperatures as low as 50 °C in an aqueous phase reaction when using the green oxidant H 2 O 2 . It was previously proposed that extra framework Fe species at the exchange sites of the zeolite are responsible for activation of both the alkane and hydrogen peroxide. Through a systematic study of the influence of framework topology and exchange properties, it is now shown that this high catalytic activity is specific to the MFI‐type Brønsted acidic zeolite ZSM‐5. Furthermore, through a simple aqueous acid washing treatment, leaching of approximately 77 % of iron present within a Fe/ZSM‐5 catalyst only caused the relative propane conversion to decrease by 17 %; implying that most of the initially loaded Fe does not actually contribute to the catalytic activity. This small change in conversion after ‘excess’ Fe removal, amounts to a three‐fold increase in turnover frequency (TOF) (Fe) from 66 h −1 to 232 h −1 compared with the parent Fe/ZSM‐5 catalyst. By comparing these samples, it is shown by NH 3 temperature‐programmed desorption, 27 Al magic angle spinning NMR spectroscopy, X‐ray photoelectron spectroscopy and TEM analysis that surface iron oxide species are effectively spectators in the oxidation of propane with H 2 O 2 . This provides further insight as to the location and true nature of the catalytically active Fe species.