Structural Evolution under Reaction Conditions of Supported (NH4)3HPMo11VO40 Catalysts for the Selective Oxidation of Isobutane

Catalysts

Fangli Jing¹  Benjamin Katryniok¹  Elisabeth Bordes-Richard¹  Franck Dumeignil¹  Sstien Paul¹ 

[1] CNRS UMR 8181, Unité de Catalyse et Chimie du Solide (UCCS), Université Lille 1 Sciences et Technologies, F-59655 Villeneuve d’Ascq Cedex, France; E-Mails:

关键词: isobutane;    methacrylic acid;    selective oxidation;    characterization by in situ methods;    heteropolymolybdates;   

DOI  :  10.3390/catal5010460

来源: mdpi

【 摘 要 】

When using heteropolycompounds in the selective oxidation of isobutane to methacrolein and methacrylic acid, both the keeping of the primary structure (Keggin units) and the presence of acidic sites are necessary to obtain the desired products. The structural evolution of supported (NH₄)₃HPMo₁₁VO₄₀ (APMV) catalysts under preliminary thermal oxidizing and reducing treatments was investigated. Various techniques, such as TGA/DTG (Thermo-Gravimetric Analysis/Derivative Thermo-Gravimetry), H₂-TPR (Temperature Programed Reduction), in situ XRD (X-Ray Diffraction) and XPS (X-ray Photoelectron Spectroscopy), were applied. It was clearly evidenced that the thermal stability and the reducibility of the Keggin units are improved by supporting 40% APMV active phase on Cs₃PMo₁₂O₄₀ (CPM). The partial degradation of APMV takes place depending on temperature and reaction conditions. The decomposition of ammonium cations (releasing NH₃) leads to the formation of vacancies favoring cationic exchanges between vanadium coming from the active phase and cesium coming from the support. In addition, the vanadium expelled from the Keggin structure is further reduced to V⁴⁺, species, which contributes (with Mo⁵⁺) to activate isobutane. The increase in reducibility of the supported catalyst is assumed to improve the catalytic performance in comparison with those of unsupported APMV.

【 授权许可】

CC BY   
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