Nano-pellet α-Al 2 O 3 was prepared using aluminum nitrate as precursor and urea as fuel by a fast method of solution combustion synthesis. The formation of the nano material was dependent on the molar ratio of fuel/oxidant, calcination temperature, and foreign metallic ions. The prerequisite conditions of the formation were a suitable fuel/oxidant molar ratio larger than two and calcination temperature higher than 673 K. Foreign ions, Ce 4+ or Co 2+ , hindered this formation via promoting the generation of stable penta-coordinated Al 3+ ions due to strong interaction with alumina, were revealed by 27 Al NMR spectra. Such Al 3+ ions were recognized as a critical intermediate state for the phase transformation of alumina and their presence deterred the transformation. The nano-pellet morphology of the product demonstrated a specific surface area of 69 m 2 /g, of which the external surface area occupied 59 m 2 /g. It was found that the supported cobalt acetate on such nanopellets existed as nanoparticles attached to the external surface, evidenced by the TEM characterization. The prepared catalyst could efficiently catalyze the selective oxidation of cyclohexane under the reaction condition of pressure under 0.8 MPa, temperature at 373 K, and time for 4 hours. The conversion of the reaction achieved up to 7.9%; while the cyclohexanone selectivity was 42.7% and the cyclohexanone and cyclohexanol selectivity was 91.6%. This catalytic performance recommends the supported cobalt acetate on the inert nano-pellet a-Al 2 O 3 as a promising catalyst for the selective oxidation of cyclohexane.
In
this study, metallic–organic frameworks (MOFs) were used as
a precursor for different proportions of rare-earth ion doping in
the preparation process of the precursor system. The mesoporous nanoparticle
(anatase-type) titanium oxide with certain morphology was prepared
by calcining under air atmosphere at 500 °C. The mesoporous structure
and special morphology of the rare-earth ion-doped MOF structure are
observed. The as-obtained titanium oxide nanoparticle has good surface
area and uniform pore distribution, and its leakage current is reduced.
Scanning electron microscopy, transmission electron microscopy, X-ray
diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy,
Brunauer–Emmett–Teller (BET) measurements, and X-ray
photoelectron spectroscopy (XPS) were used to characterize their microscopic
morphology, composition, functional groups, porosity, and so on. Moreover,
the samples after calcination were evenly dispersed in silicone oil
as electrorheological materials and the electrorheological properties
were tested under the mode of controlling the shear rate. It was found
that the electrorheological efficiency of rare-earth ion-doped titanium
oxide was better than that of pure TiO2 obtained by calcining
an MOF precursor. Through the study of its dielectric properties,
it is found that good electrorheological (ER) performance is closely
related to good dielectric properties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.