Highly dispersed Fe 3+ -Al 2 O 3 for the Fenton-like oxidation of phenol in a continuous up-flow fixed bed reactor. Enhancing catalyst stability through operating conditions,

Fe2O3/Al2O3 catalysts (2% Fe) were prepared and characterized by XRD, BET, Raman, and SEM-EDAX. The systems were tested for the catalytic oxidation of phenol solutions (5000 ppm) with H2O2. The effects of reaction temperature, catalyst loading, phenol initial concentration, and H2O2:phenol molar ratio were evaluated. The relatively low oxidant consumption rates favored increased mineralization levels at substoichiometric H2O2 initial concentrations. The stability of the catalytic system was improved by means of a thermal treatment at 900 °C, which did not seriously affect the overall reaction performance.

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Highlights Mesoporous Al2O3 and Fe-Al2O3 were synthesized by a sol-gel methodology. Mesoporous synthesized materials were effective As(III) and As(V) adsorbents. Mesoporous alumina showed better performance than commercial alumina. Mesoporous Al 2 O 3 Sol-gel synthesisEvaporation Induced Self-Assembly (EISA)

BACKGROUND: Improved Fe 2 O 3 /Al 2 O 3 catalysts were studied for the catalytic oxidation of concentrated phenol solutions (5 g L −1 ) with H 2 O 2 . To enhance catalyst stability, two strategies were investigated: the use of a high calcination temperature and a step of immersion into an organic acid solution. The reaction runs were performed in a continuous reactor at 70 ∘ C and atmospheric pressure. RESULTS: For all the catalysts, almost complete phenol degradation was achieved. The mineralization levels were incomplete, reaching 60 and 50% for the catalysts treated with acetic and oxalic acid, respectively. The leaching levels were reduced from 25% (for the untreated catalyst) to 11% after the immersion in oxalic acid. In all cases, the formation of reversible carbonaceous deposits was observed during reaction and a progressive decay in phenol, TOC and H 2 O 2 conversions was registered. CONCLUSION: Catalyst resistance to leaching was significantly enhanced by combining both thermal and acidic treatments. These procedures did not affect the catalytic wet hydrogen peroxide oxidation (CWHPO) performance in terms of mineralization levels. The lixiviation levels were acceptable, taking into account the strong acidic reaction medium. Deactivation processes might be primarily associated with the formation of reversible carbonaceous deposits due to intermediates accumulation onto the catalyst surface.

The dispersion of intercalated/exfoliated clays in polymers imparts some desired properties to the neat matrix, such as a decrease in permeability due to geometrical effects and an increase in the fire resistance due to the inorganic character of the clay. However, processing is difficult mainly due to the high viscosities of the starting dispersions. In this article we explored the possibility of producing a dispersion of crystalline platelets in situ during polymerization, starting from homogeneous solutions. For this purpose, we replaced the clays with polyhedral oligomeric silsesquioxanes (POSS) because they can be dissolved in adequate polymer precursors and can be phase-separated in the course of polymerization. The aim was to find conditions where a crystal-liquid (C-L) phase separation could take place instead of a conventional L-L phase separation. The in-situ generation of POSS crystalline platelets can impart similar characteristics to those observed in clay-modified polymers (except for the nanoscopic size of thickness), with the advantage of a much easier processing. The selected formulation was based on glycidyloxypropyl-heptaisobutyl POSS dissolved in a stoichiometric mixture of diglycidyl ether of bisphenol A (DGEBA) and 4,4 0 -methylenebis(2,6diethylaniline) (MDEA). In a specific range of POSS concentrations and polymerization temperatures, a C-L phase separation was observed generating POSS crystalline platelets with sizes in the range of the micrometers. Following this primary phase separation, a dispersion of POSS-rich droplets was produced when the residual liquid phase entered the L-L immiscibility region. The final material exhibited a dual dispersion of POSS platelets and spherical POSS-rich domains uniformly dispersed in the matrix. A thermodynamic model enabled to provide an explanation of the experimental observations.

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