A mesoporous
crystalline niobium oxide with tunable pore sizes
was synthesized via the sol–gel-based inverse micelle method.
The material shows a surface area of 127 m2/g, which is
the highest surface area reported so far for crystalline niobium oxide
synthesized by soft template methods. The material also has a monomodal
pore size distribution with an average pore diameter of 5.6 nm. A
comprehensive characterization of niobium oxide was performed using
powder X-ray diffraction, Brunauer–Emmett–Teller, thermogravimetric
analysis, scanning electron microscopy, transmission electron microscopy,
UV–vis, and X-ray photoelectron spectroscopy. The material
acts as an environmentally friendly, solid acid catalyst toward hydration
of alkynes under with excellent catalytic activity (99% conversion,
99% selectivity, and 4.39 h–1 TOF). Brønsted
acid sites present in the catalyst were found to be responsible for
the high catalytic activity. The catalyst was reusable up to five
cycles without a significant loss of the activity.
Direct catalytic conversion of methane to methanol with O2 has been a fundamental challenge in unlocking abundant natural gas supplies. Metal-free methane conversion with 17% methanol yield based on the limiting reagent O2 at 275 °C was achieved with near supercritical acetonitrile in the presence of boron nitride. Reaction temperature, catalyst loading, dwell time, methane–oxygen molar ratio, and solvent-oxygen molar ratios were identified as critical factors controlling methane activation and the methanol yield. Extension of the study to ethane (C2) showed moderate yields of methanol (3.6%) and ethanol (4.5%).
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