Influence of the Ag Content on the Activity of Ag/CeO 2 Catalysts in the Reduction of 4-Nitrophenol at Room Temperature
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uence of the Ag Content on the Activity of Ag/CeO2 Catalysts in the Reduction of 4-Nitrophenol at Room Temperature and Atmospheric Pressure M. V. Chernykha, *, N. N. Mikheevaa, V. I. Zaikovskiib, and G. V. Mamontova aTomsk
State University, Tomsk, 634050 Russia Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia *e-mail: [email protected]
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Received December 16, 2019; revised March 2, 2020; accepted March 10, 2020
Abstract—Functionalized aromatic amines are an important basis for the production of pharmaceuticals, agrochemicals, polymers, dyes, and other industrially significant products. The catalytic reduction of nitroarenes to aromatic amines is one of the methods most commonly used for the production of amines both in industry and in the laboratory. In this work, we synthesized Ag/CeO2 catalysts with different silver contents (1, 3, 5, and 10 wt %) and studied the physicochemical and catalytic properties of these systems. The effect of the amount of an active component (Ag) on the activity of the catalyst in the reduction of 4-nitrophenol with sodium borohydride in water at room temperature and atmospheric pressure was shown. As the silver content was increased to 10 wt %, the rate of reaction increased, but the absolute activity (TOF) decreased. Keywords: Ag/CeO2 catalysts, reduction of 4-nitrophenol, 4-aminophenol, mild conditions DOI: 10.1134/S002315842005002X
INTRODUCTION The reduction of nitro compounds to corresponding amino compounds is an important intermediate stage in the production of medicines, plastics, agrochemicals, etc. [1]. Systems that make it possible to carry out the process under mild conditions (at room temperature and atmospheric pressure with the use of harmless solvents), do not contain expensive noble metals (Pd, Au, Pt, etc.), and are characterized by high activity and selectivity are promising catalysts for the reduction of nitro compounds [2]. Currently, silvercontaining catalysts satisfy these requirements; the high activity of these catalysts is achieved by simple regulation of the sizes and shapes of Ag particles at the stage of synthesis [3]. In addition, silver-containing systems are inexpensive and nontoxic [4]. Many metal oxides (Fe2O3 [5], Fe3O4 [6], SiO2 [7], CeO2 [8], etc.), SBA-15 [9], carbon nanotubes [10], graphene oxide [11], and polymeric and other composite materials [12] are widely used as the supports of silver catalysts for the reduction of nitro compounds. CeO2 attracted the attention of researchers due to its unique properties, which allow it to be used not only as Abbreviations: HR TEM, high resolution transmission electron microscopy; TPR-H2, temperature-programmed reduction with hydrogen; TOF, turnover function; BJH, Barrett–Joyner– Halenda method; BET, Brunauer–Emmett–Teller method.
a support in heterogeneous catalysis but also in fuel cells, oxygen sensors, mechanical polishing, ultraviolet blocks, and luminescent materials [13]. The surface Lewis basic sites and oxygen vacancies of ceria can take
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