EFCA - Programme Franco-Allemand : Catalyse Homogène et Hétérogène pour le Développement Durable (Environmentally Friendly homogeneous and heterogeneous Catalysis - EFC)

Development of novel ammoxidation catalysts with tailored anion structures based on transition metal nitrides and oxynitrides – AMMOXAN

Development of novel ammoxidation catalysts with tailored anion structures based on transition metal nitrides and oxynitrides

Development of catalysts to substitute propane to propene <br />increasingly scarce and costly. <br />

Development of novel ammoxidation catalysts with tailored anion structures based on transition metal nitrides or oxynitrides

Acrylonitrile is an important intermediate in chemical industry for the synthesis of various polymers and coatings. Acrylonitrile is currently produced by ammoxidation of costly and increasingly scarce propylene. This project aims at developing novel catalysts allowing the use of cheaper and abundant propane, which is of industrial interest, economic potential and sustainability, since natural resources (gas and oil) can be more efficiently used. <br />Despite much research in the last decade, propane-based processes have not been industrialized. Hence, totally novel routes to tailored catalysts should be developed. For that we tried to exploit the unique properties of nitrides and oxynitrides of transition metal. A rational approach has been followed that integrates catalyst synthesis, catalyst function explored under working conditions as well as tests and kinetic studies, taking advantage of the complementary skills of the two collaborating laboratories. For exploring the application potential and the role of the structure of the catalysts, these catalysts have been tested for both ammoxidation propane and 3-picoline. Each of the two reactions was studied by one laboratory to increase the impact of the research undertaken. <br />

Oxi-nitrides based catalysts have been prepared nitriding mixed oxides under ammoniac or in catalytic reaction conditions. These amorphous catalysts have been characterized using a multi-techniques approach using XRD, chemical analysis, Raman and Xanes spectroscopies, NMR, EPR and electron microscopy. After characterization the catalysts have been tested for the ammoxidation of propane between 480 and 520°C. They have also been tested for a low temperature reaction (300-400°C): the ammoxidation of 3-picoline. Various parameters were studied like the gas partial pressures (propane, O2, NH3), the temperature or the contact time in order to better understand the catalytic reaction mechanism. After testing the catalysts were characterized to evidence possible transformations and try to relate the catalytic and structural or textural properties. With that respect, we have also characterized catalysts in reaction conditions (operando) by X-ray emission spectroscopy (XES) and EPR-uv-Raman. The operando characterization of catalysts by XES was made for the first time in the world.

This project allowed understanding the origin of the catalytic properties of oxinitrides for alkanes ammoxidation and to propose sites for alkane activation and N insertion. A new preparation method of catalysts has been finalized. It can be applied to syntheses of numerous binary or ternary oxides and enable to increase the metallic elements distribution in the oxides. All these results have led to the design of more efficient catalysts. Finally the study has also demonstrated that X-ray emission spectroscopy could be applied in operando conditions to characterize catalysts.

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The results will be valorized by six publications in international journal with high impact factors (J. Catal., Catal. Today, ChemCatChem, Appl. Catal. A)
and two that will be submitted before the end of 2012 (J. phys. Chem. And Catal. Comm.). Although efficient catalysts have been designed, no patent has been taken.

Acrylonitrile (ACN) is an important intermediate in chemical industry for the manufacture of acrylic fibres, polymers and coatings being currently produced by ammoxidation of costly and increasingly scarce propylene. This project aims at developing novel catalysts allowing the use of cheaper and abundant propane, which is of high industrial interest, economic potential and sustainability, since natural resources (gas and oil) can be more efficiently used. Despite much research in the last decade, propane-based ACN processes are still in their infancy. Currently, the best catalysts are based on well-known MoVNbTe mixed oxides (“Mitsubishi” systems) which provide maximum ACN yields of only 60 %. Attempts to enhance the catalytic performance were mainly based on modifying the catalysts cation composition, yet with limited success. Therefore, it is anticipated that the propane-based route to ACN using “Mitsubishi” catalysts cannot be considerably improved anymore. Hence, novel routes to tailored catalysts shall be developed, which do not just vary the cation composition in MoVNbTe oxides as usual, but exploit the unique properties of different anion structures, e. g., from mixed transition metal nitrides and oxynitrides. A complex, rational approach will be followed that integrates catalyst synthesis, catalyst function explored under working conditions as well as catalytic tests and kinetic studies, taking advantage of the complementary skills of the two collaborating laboratories in each step of the research program. For exploring the application potential and the role of structural features of the new catalysts with respect to ammoxidation of aromatic substrates, toluene shall also be used as reactant.

Project coordinator

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

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Beginning and duration of the scientific project: - 0 Months

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