The Exchange Reaction of Deuterium with the Hydroxyl Groups of Zeolite Catalysts

The concentration of hydroxyl (–OH) groups in epitaxial barium titanate (BaTiO3) films (thickness ∼ 200 nm), deposited on single-crystal strontium titanate (SrTiO3) at 150 °C by a hydrothermal technique, was investigated using x-ray photoelectron spectroscopy and Fourier transform infrared (FTIR) spectroscopy. After hydrothermal treatment, a broad FTIR resonance for the hydroxyl groups indicated a significant concentration of surface –OH groups in the films. The as-deposited films were subsequently treated hydrothermally with D2O, and the kinetics of the exchange reaction between –OH incorporated into the film and –OD from the D2O were studied using FTIR. For reactions carried out intermittently, the kinetics of the exchange reaction between –OH by –OD depended not only on the total reaction time, but also on the duration of each treatment. The broad FTIR hydroxyl resonance in the as-deposited hydrothermal film was significantly reduced only after heating for 1 h at 600–800 °C.

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SITING OF AL AND BRIDGING HYDROXYL GROUPS IN ZEOLITE CATALYSTS. COMPUTER SIMULATIONS OF THEIR STRUCTURE, VIBRATIONAL SPECTRA AND ACIDITY

Proceedings from the Ninth International Zeolite Conference ◽

10.1016/b978-1-4832-8383-8.50081-7 ◽

1993 ◽

pp. 687-694

Author(s):

K.-P. SCHRöDER ◽

J. SAUER

Keyword(s):

Computer Simulations ◽

Vibrational Spectra ◽

Zeolite Catalysts ◽

Hydroxyl Groups

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Theoretical Studies on the Mechanism of deNOx Process in Cu–Zn Bimetallic System—Comparison of FAU and MFI Zeolites

Molecules ◽

10.3390/molecules27010300 ◽

2022 ◽

Vol 27 (1) ◽

pp. 300

Author(s):

Izabela Kurzydym ◽

Izabela Czekaj

Keyword(s):

Density Functional ◽

Co Adsorption ◽

Computer Calculation ◽

Zeolite Catalysts ◽

Hydroxyl Group ◽

Hydroxyl Groups ◽

Hydrothermal Conditions ◽

Fau Zeolite ◽

Cu Catalyst ◽

Mfi Zeolites

In the present study we propose a more promising catalyst for the deNOx process to eliminate harmful nitrogen oxides from the environment. The study was performed with a computer calculation using density functional theory (DFT) based on an ab initio method. Two zeolite catalysts, FAU and MFI, were selected with additional Cu–O–Zn bimetallic dimer adsorbed inside the pores of both zeolites. Based on the analysis of preliminary studies, the most probable way of co-adsorption of nitric oxide and ammonia was selected, which became the initial configuration for the reaction mechanism. Two types of mechanisms were proposed: with hydroxyl groups on a bridged position of the dimer or a hydroxyl group on one of the metal atoms of the dimer. Based on the results, it was determined that the FAU zeolite with a bimetallic dimer and an OH group on the zinc atom was the most efficient configuration with a relatively low energy barrier. The real advantage of the Cu–Zn system over FAU and MFI in hydrothermal conditions has been demonstrated in comparison to a conventional Cu–Cu catalyst.

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