ARTICLE This journal isRuthenium-doped H-Montmorillonite (H-Mont) and Ti-pillared clay (Ti-PILC) were prepared then studied for oxidation of cyclohexene, with tert-butylhydroperoxide (TBHP) as the oxygen source. The Ti-PILC support was prepared by hydrolysis of Ti(OC 3 H 7 ) 4 with HCl. The synthesized Ru/Ti-PILC and Ru/H-Mont catalysts were characterized by chemical analysis, surface area/pore volume measurements, Fourier transform infrared (FTIR) spectroscopy, Xray powder diffraction (XRD), and UV-vis-diffuse reflectance spectroscopy (UV-vis-DRS). Both catalysts can selectively oxidize cyclohexene through allylic oxidation to give 2cyclohexene-1-one as the major product, and 2-cyclohexene-1-ol as the minor product. The influence of reaction time, temperature, catalyst amount, and substrate/oxidant ratio was also investigated to find the optimal reaction for cyclohexene oxidation to get the highest conversion. Indeed, when the 5%Ru/Ti-PILC was employed as catalyst, 59 % of cyclohexene conversion, 87 % of selectivity for 2-cyclohexene-1-one and 13 % of selectivity for 2cyclohexene-1-ol were obtained under ambient pressure, at 70 °C, for a 6 h reaction time. The catalysts were reused in four consecutive runs.

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In this work, we study cyclohexene oxidation by molecular oxygen on doped-TiO 2 . The improvement of the oxidizing capacity of titanium oxide by doping with iron oxide at different molar ratios is checked. All materials with different molar ratios (Ti/Fe = 9, 4, and 2) are prepared by the sol-gel method and fully characterized by ICP, XRD, SEM, DR/UV-vis, IR, and N 2 adsorption/desorption. The results show that iron is successfully incorporated into the titanium matrix but the incorporated amount is limited. In catalytic tests, improved activity is noticed while using TiO 2 in the presence of Fe 2 O 3 , which is due the improved oxidation. Conversion in the range of 21-42% depending on the presence of iron oxide was obtained with excellent yield of adipic acid (97% selectivity).

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Several VO 2 /CeO 2 based catalysts, with V loadings between 5 and 20 wt%, were prepared by impregnation and subsequently dried, calcined and reduced at 673 K. The structural characterization of these materials was carried out using X-ray diffraction (XRD), N 2 adsorption-desorption at 77 K, UV-vis diffuse reflectance spectroscopy (DR UV-vis) and Fourier-transform infrared spectroscopy (FTIR). Their catalytic activities in the epoxidation of cyclohexene, with TBHP as oxidant and heptane as solvent, were also examined. XRD results revealed a good dispersion of VO 2 species on ceria. FTIR and DR UV-visible spectroscopy techniques indicated that polymeric vanadyl species are present on all catalysts and a crystalline VO 2 phase appears on the 20 wt% vanadium sample. Experimental results revealed that catalyst activity decreases with increased vanadium loading, whereas the epoxide selectivity increased up to 90% when the vanadia loading reached 15 wt%. In the case of 20 wt% VO 2 /CeO 2 , the reaction switched towards a 100% enol, enone selectivity. The presence of CeVO 4 was shown to influence the conversion and selectivity of the reaction.

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Heterogenization of homogenous catalysts consisting of vanadium substituted polyphosphomolybdate with Keggin structure supported on activated bentonite for epoxidation of cyclohexene.