Abstract
Biocarbon supported Ni catalysts have been prepared by facile impregnation of Ni species by microwave-heating and used for selective hydrogenation of nitrobenzene to cyclohexylamine. These catalysts were characterized by X-ray diffraction, Raman spectra, N2 sorption measurement, X-ray photoelectron spectroscopy, temperature programmed reduction of H2 and H2 temperature-programmed desorption. The morphology and particle size of catalysts were imaged by scanning electron microscope and transmission electron microscope. For the hydrogenation of nitrobenzene to cyclohexylamine, 10%Ni/CSC-II(b) exhibits the best catalytic activity to achieve 100 mol% conversion of nitrobenzene and 96.7% selectivity of cyclohexylamine under reaction conditions of 2.0 MPa H2 and 200 °C, ascribed to high dispersion of Ni species and formation of nanosized Ni particles on the support aided by microwave-heating. Thus-prepared Ni/CSC catalyst is greatly activated, in which the addition of precious metal like Rh is totally avoided.
Highlights
At present, the focus on the environment and the reduction of energy consumption and chemical waste in chemical transformations is a great challenge[1]
Our previous work reported highly selective ‘one-step’ catalytic hydrogenation from nitrobenzene to cyclohexylamine over the supported %Ni-‰Rh composite catalysts[52], in which the addition of 3‰Rh was necessary for enhanced activity of Ni/CSC catalysts
The results show that the catalyst 10%Ni/CSC-II (b) prepared via supporting Ni species on ball-milled CSC by microwave-heating contains more structural defects and exhibits higher catalytic activity than other catalysts
Summary
The focus on the environment and the reduction of energy consumption and chemical waste in chemical transformations is a great challenge[1]. Metal catalysts have been relatively efficient for catalytic hydrogenation of nitro compounds, inclusive of Raney nickel, copper chromite or noble metals including platinum, palladium and rhodium These metals exhibit high catalytic hydrogenation activity, the selectivity to the desired aromatic amines is generally not high. Our previous work reported highly selective ‘one-step’ catalytic hydrogenation from nitrobenzene to cyclohexylamine over the supported %Ni-‰Rh composite catalysts[52], in which the addition of 3‰Rh was necessary for enhanced activity of Ni/CSC catalysts. Such a process can completely skip the synthesis, separation and transformation of aromatic amine intermediates, and meet the requirements of energy-saving green chemistry. The corresponding effects are deeply revealed by wide reactions and structural characterizations
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