Preparation and activity of Cu-Al mixed oxides via hydrotalcite-like precursors for the oxidation of phenol aqueous solutions
The authors performed thermogravimetric analysis (TGA), X-ray diffraction (XRD), BET areas, and FT-IR spectroscopy to characterize copper-aluminium mixed-oxide samples with Cu/Al ratios between 0.5 and 3.0. The thermal stability, crystallinity, and purity of the materials depended on the Cu/Al atomic ratio. The FT-IR and TG detected carbonate (mainly) and nitrate as counteranions which interact in the interlayer region. The authors found loosely bound carbonate and nitrate anions and one strongly bound type of carbonate. They used dynamic XRD experiments to study the evolution of phases during calcination. All the samples after calcination showed well-dispersed CuO and/or CuAl{sub 2}O{sub 4} phases. They also tested their catalytic behavior for the oxidation of 5 g/l phenol aqueous solutions using a triphasic tubular reactor working in a trickle-bed regime and air with an oxygen partial pressure of 0.9 MPa at a temperature reaction of 413 K. Phenol conversion decreased continuously over time for the samples calcined at lower temperatures (673 K). This is because of continuous loss of the CuO phase by elution and the formation of a new phase like copper oxalate on the surface of the copper catalysts which also elutes with time XRD shows that samples calcined at higher temperatures (1,073 K) and after HCl treatment (0.1 M) to avoid the CuO phase, have a pure copper aluminate phase. This CuAl{sub 2}O{sub 4} phase reaches steady activity plateaus in the 55--65% range of phenol conversion. The triphasic tubular reactor using trickle-bed regime largely avoids polymer formation as a catalyst-deactivation process.
- Research Organization:
- Univ. Rovira i Virgili, Tarragona (ES)
- OSTI ID:
- 20005902
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 188; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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