Studies on the hydrolysis of {Cu[Al(OPri)4]2}, a single source precursor for CuAl2O4 spinel (original) (raw)
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Journal of Catalysis, 1999
We 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. We found loosely bound carbonate and nitrate anions and one strongly bound type of carbonate. We used dynamic XRD experiments to study the evolution of phases during calcination. All the samples after calcination showed welldispersed CuO and/or CuAl 2 O 4 phases. We also tested their catalytic behaviour 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 (1073 K) and after HCl treatment (0.1 M) to avoid the CuO phase, have a pure copper aluminate phase. This CuAl 2 O 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.
: Present article impetus on exploring the synthesis of spinel copper aluminate nanocomposites (CuAl2O4 NCs) for the electrochemical performance, and the solvent-free synthesis of xanthanedione derivatives. CuAl2O4 NCs were synthesized from copper nitrate and aluminum nitrate with/without use of sodium dodecyl sulfate (SDS) by aqueous precipitation (AP) and microwave-assisted (MW) technique. As-synthesized CuAl2O4 NCs were characterized for the structural and morphological facet by XRD, FT-IR, DRS, EDS, XPS, Raman, SEM, TEM, and AFM. Cubic spinel-structure formed after calcinations at 900oC was confirmed by XRD, while Raman, XPS, and EDS validated composition and purity. TEM results reveals that the shapes of particles were appeared a uniform nanosphere with an average sizes 10 nm for MWS-CuAl2O4 (Microwave-assisted with surfactant), while APS-CuAl2O4 NCs exhibited nanograins with particle size 17 nm (Aqueous precipitation with surfactant). AFM discloses comparatively higher surface roughness by the MWS-CuAl2O4 NCs than APS-CuAl2O4 NCs. The electrochemical performance of CuAl2O4 NCs was examined in aqueous Na2SO4 (1M) as electrolyte using cyclic voltammetry (CV). CV results divulged MWS-CuAl2O4 NCs demonstrated a high specific capacitance (125 F g-1) at a current density (0.5 mA cm-2). Furthermore, one-pot, facile, eco-friendly MWS-CuAl2O4 NCs catalyzed synthesis of xanthanediones has been developed, which possessed excellent yield and reusability with negligible reduction in efficiency even after four consecutive cycles.