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An original process based on cold plasma assisted polymerization of tetramethyldisiloxane (TMDSO) in the presence of O2 was developed to cover substrates showing various shapes (plate and foam). In the frame of catalytic application, this coating has to act as a bonding layer for the deposition of active phase such as VOx/TiO2 well‐known for its properties in NOx and volatile organic compounds abatement and in the production of chemical intermediates. Good results were obtained by the deposition of a 5‐μm thick polysiloxane film followed by a thermal treatment under air at 650°C and by a remote nitrogen plasma post treatment. This procedure led to a silica‐like layer allowing its coating in an aqueous suspension of TiO2. Such a multilayered material can be obtained homogeneously on the whole surface of a sample showing a 3D open geometry like metallic foam. Characterizations of the different steps of the elaborated multilayer material were performed by Fourier transformed infrared spectroscopy, Raman spectrometry, X‐ray photoelectron spectroscopy, and electron probe micro‐analyzer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

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.

Cesium heteropolysalts Cs 3 PMo 12 O 40 and HCs 3 PVMo 11 O 40 were synthesized by modifying the preparation conditions in order to get materials with a much higher surface area than the original Keggin-type heteropolyacids (H 3 PMo 12 O 40 and H 4 PVMo 11 O 40 ). These solids were used as carriers for the dispersion of H 4 PVMo 11 O 40 heteropolyacid by the incipient wetness impregnation technique. The textural and structural properties of supports and catalysts were examined by scanning electron microscopy, N 2 adsorption-desorption isotherms and Raman spectroscopy. The supported catalysts were studied before and after red/ox pretreatments by X-ray photoelectron spectroscopy, which showed that both the surface composition and oxidized to reduced species ratio depend on the used carrier. The catalytic performances of these novel supported catalysts in the selective oxidation of isobutane to methacrylic acid and methacrolein were studied. The best catalytic properties were obtained when H 4 PVMo 11 O 40 was supported on HCs 3 PVMo 11 O 40 . The isobutane conversion and yield of the desired oxygenates increased along the unsupported H 4 PVMo 11 O 40 < H 4 PVMo 11 O 40 /Cs 3 PMo 12 O 40 < H 4 PVMo 11 O 40 /HCs 3 PVMo 11 O 40 series.