• A Choukchou-Braham

      Articles written in Bulletin of Materials Science

    • Catalytic oxidation of cyclohexane to cyclohexanone and cyclohexanol by tert-butyl hydroperoxide over Pt/oxide catalysts

      I Rekkab-Hammoumraoui A Choukchou-Braham L Pirault-Roy C Kappenstein

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      Heterogeneous oxidation of cyclohexane with tertiobutyl hydroperoxide was carried out on Pt/oxide (Al2O3, TiO2 and ZrO2) catalysts in the presence of different solvents (acetic acid and acetonitrile). The catalysts were prepared using Pt(NH3)2(NO2)2 as a precursor and characterized by chemical analysis using the ICP–AES method, XRD, TEM, FTIR and BET surface area determination. The oxidation reaction was carried out at 70°C under atmospheric pressure. The results showed the catalytic performance of Pt/Al2O3 as being very high in terms of turnover frequency.

    • Synthesis of vanadium oxides 5 wt.%VO2–M𝑥O𝑦 by sol–gel process and application in cyclohexene epoxidation

      S El-Korso I Rekkab A Choukchou-Braham S Bedrane L Pirault-Roy C Kappenstein

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      A series of SiO2, Al2O3 and TiO2 mixed vanadium materials have been prepared from inorganic precursors via the sol–gel process and subsequently dried, calcined and reduced at elevated temperatures. Structural characterization of these materials was carried out by X-ray diffraction (XRD), N2 adsorption at 77 K, thermal analysis (TGA/DTA), UV-vis diffused reflectance spectroscopy (DR UV-vis) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX). Their catalytic activities in the epoxidation of cyclohexene with TBHP as oxidant were also examined. Results of XRD and DR UV-visible diffused revealed that VO2 species are predominant in all samples and no formation of V2O5 was detected. Experimental results indicated that the VO2–SiO2 catalysts performed excellently for the epoxidation of cyclohexene by tertiobutyl hydroperoxide.

    • Study of effect of chromium on titanium dioxide phase transformation

      A Bellifa L Pirault-Roy C Kappenstein A Choukchou-Braham

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      MTi𝑋 samples with different atomic chromium percentages were synthesized by sol–gel method and calcined at 400 °C under air. The effects of Cr and temperature on titanium dioxide phase transition were studied. In situ measurement showed the presence of anatase phase for all samples at temperature < 500 °C. Without Cr content, the anatase–rutile transition takes place at 600 °C and the rutile fraction increases with increase of temperature. In the presence of Cr content, rutile phase appeared at 700 °C. Cr2O3 phase was shown only in the case of CrTi20 content at 800 °C which indicates that the segregation remains modest. We have also studied the anatase–rutile transition kinetics by using in situ X-ray measurements. It was found that the anatase phase stability increases as the chromium content increases. Results confirm that the transformation of anatase–rutile is of first order.

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