Effect of the variation of metal and cerium loadings on CeO2x–TiO2(100−x) supports in the complete catalytic oxidation of formaldehyde

Research on Chemical Intermediates - Formaldehyde has been successfully converted into CO2 and H2O at low temperature in the presence of CeO2x–TiO2(100?x) mixed oxides prepared by the...     

Diagnosis of deactivation sources for vanadium catalysts used in SO2 oxidation reaction and optimization of vanadium extraction from deactivated catalysts

Physico-chemical analysis (X-ray, FTIR) and/or methanol oxidation reaction test were performed on fresh and deactivated vanadium catalysts used in H₂SO₄ manufacturing. It allowed the diagnosis of catalyst deactivation sources, as well as the processes of regenerating and recycling the worn out catalyst in converter. One of these processes is hydrometallurgical method. It consists in treating the deactivated catalyst with alkaline or acidic reagents and forming vanadate solution. A simple and non-costly operation of chemical attack permits the extraction of vanadium from silica in deactivated catalyst. The extracted vanadium can be used for the confection of regenerated catalysts or metallic tools. After optimization, this method can be used for industrial application.     

Preparation and characterization of CeO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> aerogels supported ruthenium for catalytic wet air oxidation of p-hydroxybenzoic acid

Catalytic wet air oxidation of an aqueous solution of p-hydroxybenzoic acid was conducted over ruthenium catalysts (1 wt%) supported on CeO₂–Al₂O₃ aerogels mixed oxides at 140 °C and 50 bars of air. We study the effect of the amount of CeO₂ in the catalyst. We found that the optimal cerium content in the Al₂O₃ support was 20 wt%. The activity of the Ru/Al₂O₃ and Ru/CeO₂ was also tested for comparison. It was found that the addition of CeO₂ on the alumina support improves the activity of Ru catalysts. The activity of the samples decreases in the following order: Ru/Ce–Al (20) > Ru/Ce–Al (10) > Ru/Ce–Al (5) ≈ Ru/Al₂O₃ > Ru/CeO₂. Samples characterization was performed by means of N₂ adsorption–desorption, XRD, UV–Vis, TPR, SEM and TEM.     

Ag/ZrO2 and Ag/Fe–ZrO2 catalysts for the low temperature total oxidation of toluene in the presence of water vapor

Transition Metal Chemistry - New mesoporous and well-structured Ag-based catalysts (xAg/ZrO2 and xAg/Fe–ZrO2 with x&nbsp;=&nbsp;2&nbsp;wt%) have been investigated in the total...     

Synthesis of W‐doped TiO2 by low‐temperature hydrolysis: Effects of annealing temperature and doping content on the surface microstructure and photocatalytic activity

A series of tungsten‐doped Titania photocatalysts were synthesized using a low‐temperature method. The effects of dopant concentration and annealing temperature on the phase transitions, crystallinity, electronic, optical, and photocatalytic properties of the resulting material were studied. The X‐ray patterns revealed that the doping delays the transition of anatase to rutile to a high temperature. A new phase W_yTi_1‐yO₂ appeared for 5.00 wt% W‐TiO₂ annealed at 900 °C. Raman and diffuse reflectance UV–Vis spectroscopy showed that band gap values decreased slightly up to 700 °C. X‐ray photoelectron spectroscopy showed that surface species viz. Ti³⁺, Ti⁴⁺, O^2?, oxygen‐vacancies, and adsorbed OH groups vary depending on the preparation conditions. The photocatalytic activity was evaluated via the degradation of methylene blue using LED white light. The degradation rate was affected by the percentage of dopants. The best photocatalytic activity was achieved with the sample labeled 5.00 wt% W‐TiO₂ annealed at 700 °C.     

Ruthenium catalysts supported on TiO<Subscript>2</Subscript> prepared by sol–gel way for <Emphasis Type="Italic">p</Emphasis>-hydroxybenzoic acid wet air oxidation

The wet air oxidation of p-hydroxybenzoic acid, chosen as a model compound of olive mills wastewaters was carried out at 140 °C and 50 bar air over Ru catalysts supported on TiO₂ prepared by sol–gel method. These catalysts were characterized by means of N₂ adsorption–desorption, XRD and TEM. Optimization of the catalytic performances was obtained by studying some parameters such as the catalyst preparation method, the solvent evacuation way, the nature of the hydrolysis agent, the influence of the ruthenium salt used as the metal precursor (Ru(NO)(NO₃)₃ or Ru(acac)₃) and the catalyst pretreatment. The pre-calcination of the catalyst precursor at 300 °C under oxygen, before the reduction step under hydrogen, was detrimental to the activity. The results showed that the use of nitric acid as hydrolysis agent, drying under supercritical conditions and the use of Ru(NO)(NO₃)₃ leads to the more efficient catalyst with high TOC abatement.