XAFS Study of Dried and Reduced PtSn/C Catalysts: Nature and Structure of the Catalytically Active Phase

This study concerns single-site heterogeneous photocatalysts, composed of isolated transition metals ions (single-sites) dispersed on silica-based supports, which can be used as photocatalysts. The first part gives the definition of single-site heterogeneous catalysts. The main difficulty to prepare the latter resides in the speciation of the key elements (metal of the catalytically active phase and oxygen of the solid support) and other species (notably counter ions and ligands) the presence of which depends on the synthesis method adopted. The best preparation methods as well as the ideal features of single-site heterogeneous photocatalysts are discussed before the study focuses on single-site heterogeneous photocatalysts. Case studies are presented with photocatalysts involving titanium and chromium, and their photocatalytic reactions such as CO 2 reduction with H 2 O, degradation of organic pollutants diluted in water, NO decomposition and selective oxidation of propane are also described.

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Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

Catalysis Letters ◽

10.1007/s10562-020-03519-y ◽

2021 ◽

Author(s):

Petar Djinović ◽

Janez Zavašnik ◽

Janvit Teržan ◽

Ivan Jerman

Keyword(s):

Catalytic Activity ◽

Activated Carbon ◽

Oxidative Dehydrogenation ◽

Active Phase ◽

Lattice Oxygen ◽

Chemisorbed Oxygen ◽

Catalytically Active ◽

Temperature Programmed ◽

Propane Cracking

AbstractCeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested in propane oxidative dehydrogenation using CO2. Complete oxidation of propane to CO and CO2 is favoured by lattice oxygen of CeO2. The temperature programmed experiments show the ~ 4 nm AC supported CeO2 crystallites become more susceptible to reduction by propane, but less prone to re-oxidation with CO2 compared to bulk CeO2. Catalytic activity of CeVO4/AC catalysts requires a 1–2 nm amorphous CeVO4 layer. During reaction, the amorphous CeVO4 layer crystallises and several atomic layers of carbon cover the CeVO4 surface, resulting in deactivation. During reaction, V2O5 is irreversibly reduced to V2O3. The lattice oxygen in bulk V2O5 favours catalytic activity and propene selectivity. Bulk V2O3 promotes only propane cracking with no propene selectivity. In VOx/AC materials, vanadium carbide is the catalytically active phase. Propane dehydrogenation over VC proceeds via chemisorbed oxygen species originating from the dissociated CO2. Graphic Abstract

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In Situ Generated Nanosized Sulfide Ni-W Catalysts Based on Zeolite for the Hydrocracking of the Pyrolysis Fuel Oil into the BTX Fraction

Catalysts ◽

10.3390/catal10101152 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1152

Author(s):

Tatiana Kuchinskaya ◽

Mariia Kniazeva ◽

Vadim Samoilov ◽

Anton Maximov

Keyword(s):

Photoelectron Spectroscopy ◽

Active Phase ◽

Fuel Oil ◽

Oil Fraction ◽

Transmission Electron ◽

Catalytically Active ◽

Pyrolysis Fuel Oil ◽

Benzene Toluene ◽

Catalytic Reactivity

The hydrocracking reaction of a pyrolysis fuel oil fraction using in situ generated nano-sized NiWS-sulfide catalysts is studied. The obtained catalysts were defined using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The features of catalytically active phase generation, as well as its structure and morphology were considered. The catalytic reactivity of in situ generated catalysts was evaluated using the hydrocracking reaction of pyrolysis fuel oil to obtain a light fraction to be used as a feedstock for benzene, toluene, and xylene (BTX) production. It was demonstrated that the temperature of 380 °C, pressure of 5 MPa, and catalyst-to-feedstock ratio of 4% provide for a target fraction (IPB −180 °C) yield of 44 wt %, and the BTX yield of reaching 15 wt %.

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