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Abstract: In this work gas phase photocatalytic selective oxidation of ethanol to acetaldehyde was studied with directly fluidizable photocatalysts made of grafted VO x on titania/silica in presence of phosphors as light carriers to test their performances in the photocatalytic system. The presence of VO x species anchored on TiO2/SiO2 enhanced ethanol conversion up to 66%, with acetaldehyde selectivity higher than 99%. The performances of V-based sample at 11wt% of TiO2 supported on fluidizable support were higher than those evaluated when nano-TiO2 powder is used as support. Moreover, the photocatalytic conversion of ethanol was further increased in presence of phosphors as light carriers. From the obtained results, it is concluded that by preparing VO x based catalyst through grafting method allows a dramatic enhance in the productivity of acetaldehyde, even when the concentration level of alcohol at photoreactor inlet is increased. [Copyright &y& Elsevier]

Abstract: In this work, an innovative and effective formulation of photocatalysts is presented. The highly selective photocatalysts at 5wt% of nominal V2O5 on TiO2 for the photoconversion of ethanol to acetaldehyde was supported on the surface of commercial ZnS based phosphors (ZSP), on the base of the evidence that the addition of these phosphors, physical mixed with the photocatalysts, as light carriers inside a gas-solid fluidized bed photoreactor resulted in a significantly improved photoefficiency. Structured vanadia-titania catalysts in the form of micropellets were successfully synthesised by sol–gel method on the UV activated luminescent phosphors microparticles. The catalysts were investigated by TG-MS analyses, Raman and UV–vis spectroscopy, X-ray diffraction, as well as adsorption of N2 at −196°C. A progressive increase of the amount on titania on the phosphors was realized to get the well dispersed nanoparticles of TiO2 on ZSP surface, able to absorb the UV light needed by the photoreaction in the proximity of light source. The residual UV light can penetrate up to the phosphors core, leading to their excitation and emission of further radiation at 440nm useful to proceed the photoreaction in darker zones. The performances of structured VO x /TiO2/ZSP have been compared to physical mixtures of VO x /TiO2 catalyst with phosphors in the partial photooxidation of ethanol to acetaldehyde with the gas-solid fluidized bed photoreactor at high illumination efficiency. The ethanol consumption rate increased linearly with the ethanol initial concentration and at given alcohol concentration, its value was significantly higher on VO x /TiO2/ZSP with respect to the case in which the photocatalyst was only mixed with them. The results underlined as the higher capture of the structured photocatalyst, due to the additional light harvesting of support, gives enhanced activity in the selective oxidation of ethanol to acetaldehyde already dramatically improved by the innovative use of light emitting phosphorescent particles. [Copyright &y& Elsevier]

Abstract: The photocatalytic oxidative dehydrogenation of cyclohexane on sulphated MoO x /γ-Al2O3 catalysts has been studied in a two-dimensional fluidized bed photoreactor. The influence of Mo loading at similar sulphate content and the effect of catalyst preparation method have been investigated. Considering the influence of Mo loading at similar sulphate content, the highest photoactivity at 2.4 SO4 wt% was found at MoO3 loading of 8wt%. Selectivity to cyclohexene was 100%, irrespective of the Mo content. At fixed MoO x content, in particular at 50% of theoretical monolayer coverage, the preparation method of catalysts strongly affected the photocatalysts performances, showing in addition a slight decrease in selectivity to cyclohexene due to side-production of benzene. All the catalysts showed a similar equivalent band gap energy. Thermogravimetric analysis evidenced the presence of surface sulphate species of different thermal stabilities. A linear correlation of photoactivity with the surface sulphates amount of lower thermal stability has been found for all sub-monolayer MoO x sulphated catalysts. The neighboring of surface sulphates to octahedral polymolybdate species appears to be a key parameter for the photoactivity of the catalysts. The catalyst selectivity was related to surface acidity. Higher acidity resulted in increased cyclohexene dark adsorption and consequently in enhanced benzene formation. [Copyright &y& Elsevier]

Abstract: The photocatalytic properties of sulphated MoOx/γ-Al2O3 catalysts in cyclohexane oxidative dehydrogenation have been determined in a two-dimensional fluidized bed photoreactor and compared to those of sulphated MoOx/TiO2 catalysts. Photocatalytic tests on MoOx/γ-Al2O3 at 8wt% MoO3 and various sulphate contents showed the selective (100%) formation of cyclohexene, without production of benzene, as instead found with MoO x /TiO2. These results show that the selectivity of photocatalytic cyclohexane oxydehydrogenation is dramatically influenced by the catalyst support. Maximum cyclohexane conversion and cyclohexene yield of 11% were obtained for SO4 content of 2.6wt% at 120°C. Physico-chemical characterisation of catalysts indicates the presence of both octahedral polymolybdate and sulphate species on alumina surface, as previously found for titania. Increasing sulphate load, thermogravimetry evidenced the presence of up to three sulphate species at different thermal stability. The lower activity observed at high sulphate content is likely due to polymolybdate decoration by sulphates. [Copyright &y& Elsevier]

Abstract: Heterogeneous oxidative dehydrogenation of cyclohexane to benzene was found to occur under photocatalytic conditions on MoO x /TiO2. Initial cyclohexane conversion of 15% and maximum selectivity to benzene of 65% were achieved at 308K on 8wt.% MoO x /TiO2 under irradiation with a continuous flow reactor. The main by-product was carbon dioxide. Catalyst deactivation was observed. Titania exhibited high activity of total oxidation to carbon dioxide but was not selective for conversion to benzene. Polymolybdate species seem to be responsible for changing the selectivity of titania, favouring the formation of benzene. Nevertheless, when supported on α- or γ-alumina they promote only the formation of carbon dioxide. [Copyright &y& Elsevier]

The very specific operating conditions of catalytic processes for the abatement of pollutants from mobile or fixed sources, require an unusual experimental set-up to determine the catalyst performance. Selected examples of environmental catalysis applications such as deNOx with NH3 or hydrocarbons, deSOx with either powder or monolith catalysts, low temperature soot oxidation, are discussed with respect to the experimental methods to be employed for catalytic activity measurements. [Copyright &y& Elsevier]

Abstract: Heterogeneous photocatalytic partial oxidation of ethanol was studied over different Pt/TiO2 as an alternative green process for acetaldehyde production. The catalysts were synthesized through the photodeposition of Pt over sol–gel TiO2 with platinum loads of 0.5 and 1wt.%. The effect of some experimental conditions during photodeposition, such as deposition time and Pt loading, was investigated. A short deposition time at 0.5wt.% Pt nominal loading led to small average particle size of platinum (2–3nm) homogeneously distributed all over the TiO2 surface. Ethanol partial oxidation was tested in a gas–solid photocatalytic fluidized bed reactor at high illumination efficiency, using different reaction temperatures. Activity results have been correlated with characterization results of the different samples. Platinized samples prepared with short deposition times showed high conversion levels and high selectivity to acetaldehyde. Materials prepared at longer times, 120min, showed selectivities >98%, although with lower ethanol conversion. Sample with 1wt.% Pt loading prepared with 15min deposition time combined a good compromise between a relevant ethanol conversion and a very high selectivity to acetaldehyde at a selected reaction temperature of 80°C, with an acetaldehyde yield higher than 80%, which make of this catalyst a good candidate for acetaldehyde production by photocatalysis. [Copyright &y& Elsevier]

Abstract: The performances of Nb2O5–SiO2 catalysts prepared by sol–gel technique in the epoxidation of soybean oil with hydrogen peroxide have been investigated. The most active catalyst showed a good activity in epoxidation reaction but also a low selectivity to epoxide. The low selectivity has been attributed to the presence on the surface besides the Lewis acid sites, that promote the epoxidation, also of strong Brønsted acid sites, that promote the reaction of ring epoxide opening by hydrolysis. [Copyright &y& Elsevier]