Abstract Synthesizing fine chemicals and valuable pharmaceutical intermediates through selective catalytic oxidation of alcohols is indispensable and crucial. However, the conventional methods of alcohol oxidation have inevitable drawbacks, including harsh reaction conditions and environmental pollution. Thus, it is imperative to develop efficient catalytic oxidation systems for alcohols. Herein, we successfully synthesized a 15 wt %PI‐TiO 2 composite by a one‐step solid‐state heating polymerization technique. This catalyst exhibits excellent responsiveness to visible light and demonstrates remarkable catalytic activity. Furthermore, TEMPO was introduced as a cocatalyst to construct a PI‐TiO 2 /TEMPO/O 2 system for the catalytic oxidation of alcohols. In comparison to the individual effects of PI or TiO 2 , this system showcases improved catalytic activity and broader substrate applicability. As a result, the conversion efficiency of benzyl alcohol increases by 3.44 times and 2.26 times, respectively. This research not only introduces a novel approach for preparing visible light‐active PI‐TiO 2 catalysts but also indicates the significance of establishing an efficient electron transfer process in alcohol catalytic oxidation.
Inhibiting the side reactions (such as dehalogenation) while promoting both/transfer hydrogenation are the main target for the production of functional anilines from nitroarenes; consequently, the preparation of an ideal catalyst to improve reaction selectivity stays as the fundamental direction for this field. In this work, we provided an easy-to-prepared heterogeneous catalyst with multilayered graphene shells where cobalt nanoparticles were encapsulated inside and distributed uniformly. This as-prepared catalysts were fabricated via one-pot pyrolysis by using mixture of citrate acid and cobalt acetate as C source and Co source, respectively. First of all, structural features of catalyst were characterized by a series of analytic techniques involving XPS, SEM/EDS, TEM as well as elemental mapping, to reveal its unique properties in relation to the catalytic mechanisms; in simple terms, the outer graphitic shell could be activated by the electronic interaction between the inner metallic nanoparticles and the outer graphene layer. Subsequently, the catalytic performance was tested in hydrogenation of nitrobenezene by using H2 as hydrogen source, so as to optimize the preparation process as well as the reaction conditions. Other nitro aromatics with functional groups such as halogen atoms, methyl or hydroxyl were also tolerated under very mild industrially viable and scalable conditions (60 °C, 2 h, and 2 MPa H2). More surprisingly, this catalyst could still exhibit excellent yields over 96 % in gram-scale test for the selected substrates, and could also be easily separated from the aqueous system due to its magnetic properties. The determined yields of target products were not decreased even after eight cycles, suggesting a potential for future industrial application in the selective hydrogenation of nitroarenes to the corresponding amines.
The possibility of coupling the ethylbenzene dehydrogenation with water-gas shift, CO2 methanation, and nitrobenzene hydrogenation has been investigated thermodynamically. The chemical equilibria of these reactions have been calculated on the basis of the Soave−Redlich−Kwong equation of state, and the effects of the feed composition, temperature, and pressure upon ethylbenzene equilibrium conversion have been studied. It was found that the equilibrium conversion could be greatly enhanced by the reaction coupling, especially with nitrobenzene hydrogenation. When coupling with water-gas shift, the ethylbenzene equilibrium conversion can be elevated to 82.4% from 25.2% for the single ethylbenzene dehydrogenation at 550 °C. When coupling with nitrobenzene hydrogenation, the ethylbenzene equilibrium conversion can reach 98.5% at 400 °C, compared with the conversion of 3.5% at the same temperature for the single ethylbenzene dehydrogenation. The primary experiments on a series of catalysts also proved that the reaction coupling is an effective measure to improve the ethylbenzene dehydrogenation, although much more work is still necessary to develop proper catalysts for the coupling reactions.
Development of the economic, environmentally friendly synthesis of amines from nitro compounds remains important and challenging. In this work, the graphene shell encapsulated none noble Ni-based catalysts were successfully designed and synthesized via an environmentally friendly method using H2O or EtOH as solvent. These fresh and recycling catalysts were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. For the nitro compounds hydrogenation, [email protected]2O exhibits the best catalytic activity to achieve 100 mol/mol conversions of nitrobenzene and 99% selectivity of aniline under mild reaction conditions of 1.0 MPa H2 and 60 °C. Many halogen-substituted, olefin substituted nitro compounds and aliphatic nitro compounds were investigated and desired products were obtained in excellent selectivity. What is more, the catalyst had excellent stability and could be recycled 13 times without any significant loss in selectivity and activity. Furthermore, we also reported the methodology for tertiary amines synthesis using Ni-based catalyst via one-pot, cost-effective tandem combination reaction with nitrobenzene hydrogenation and amines N-methylation.
An environmentally friendly and simplified method for the preparation of graphene encapsulated Ni/NiO nanoalloy catalysts (Ni/NiO@C) was developed for the highly selective synthesis of N-methylated compounds under mild conditions.
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