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Carbon-Encapsulated Cobalt Particles Fixed in a Rigid CNT Framework: Synthesis by Spark Plasma Sintering and Catalytic Properties in CO Hydrogenationтезисы доклада Тезисы
- Авторы: Chernyak S.A., Paslova M.S., Ivanov Anton S., Egorova T.B., Maslakov K.I., Chernavskii P.A., Savilov S.V., Lunin V.V.
- Сборник: Catalyst Design: From Molecular to Industrial Level. 5th International School-Conference on Catalysis for Young Scientists (May 20-23, 2018, Moscow, Russia) [Electronic resource] : Abstracts / Boreskov institute of Catalysis SB RAS
- Тезисы
- Год издания: 2018
- Место издания: BIC Novosibirsk
- Первая страница: 145
- Последняя страница: 146
- Аннотация: Carbon encapsulated metal nanoparticles are known to be active in different catalytic reactions. For example, Pt@C was used for acetylene hydrogenation, N-doped carbon nanosheets embedded with Co nanoparticles were reported to be appropriate catalysts for oxygen reduction reactions, Fe and Ni can activate H2 in phenylacetylene hydrogenation, Co@C core-shell nanoparticles showed a high catalytic performance in Fischer-Tropsch synthesis [1]. There are several methods to prepare such systems: arc discharge, chemical vapor deposition, metal-template graphitization, spark plasma sintering (SPS) etc. Spark Plasma Sintering (SPS) is a technique utilizing uniaxial force and a pulsed direct electrical current under low atmospheric pressure to perform high speed consolidation of the powder. It is widely used for the synthesis of different materials, mainly ceramics and metal alloys, with carbon additives. Among many other approaches, it stands out for its rapidity, wide range of sintering pressure/temperature, and combination of compaction and sintering stages in one operation [2]. At the same time, important issue for catalysts preparation is the choosing of appropriate support which must have the following properties: thermal and chemical resistance, high thermal conductivity, facilitate uniform surface distribution of catalyst`s particles. Carbon nanotubes (CNTs) meet all these requirements and, besides, show lower degree of metal-support interaction, large surface area, ability to tune the surface properties in a wide range in comparison with oxide supports. SPS treatment of Co/CNT system should provide a simple one-stage technique to obtain novel type of material for catalysis in which Co nanoparticles are already reduced, stabile to oxidation, and rigidly fixed in the support framework. Moreover, such a way results in compaction and densification of CNT-based catalyst which is also important due to low density of carbon nanomaterials. In the present work a new type of 3D-material contained carbon-encapsulated cobalt nanoparticles in the framework of CNTs was synthesized by SPS to be tested in CO hydrogenation. Co/CNTs composite material was prepared by the impregnation of the multiwalled CNTs by Co(NO3)2∙6H2O ethanol solution. Samples where annealed at 350 °С for 2 h in N2 flow in quartz tubular reactor with the inner diameter of 10 mm. It was proved by XRD, TEM, and XPS that Co3O4 particles were reduced during the sintering process. Cobalt loading relative to Co0 was of 10 wt. % and samples were sintered at 800, 900, 1000, and 1200 °C 145 PP-I-13 and 30 MPa. Sintered Co/CNT samples were named as “CoTs” where TS is the sintering temperature. The influence of TS on the morphology, structure and catalytic properties of this material was investigated by Raman spectroscopy, electron microscopy, XPS, XRD. TEM and SEM images of Co800 sample are shown in Fig. 1. It was established that average diameter of the nanoparticles varied from ~7-8 in case of Co800 to few tens of nm in Co1200. Thickness of graphitic shells around Co increased and their defectiveness decreased with TS growth. According to the previously obtained data, particle size of 8-10 nm is the most effective for the achieving of optimal balance between activity and selectivity to C5+ fraction in CO hydrogenation to hydrocarbons [3]. Thus, samples sintered on 800, 900, 1000, 1200 °C have different carbon shells thickness, density and cobalt particles size increases with the sintering temperature. Most of Co particles in these samples are in metallic state and their nanoscale size make them promising for CO hydrogenation. References: [1] Hengfei Qin, Shifei Kang et al. Lignin Based Fabrication of Co@C Core-Shell Nanoparticles as Efficient Catalyst for Selective Fischer-Tropsch Synthesis of C5+ Compounds. Sustainable Chem. Eng., Just Accepted Manuscript. [2] Strokova, N.; Savilov, S.; Xia, H.; Aldoshin, S.; Lunin, V. Sintered Carbon Nanomaterials: Structural Change and Adsorption Properties. Z. Phys. Chem. 2016, 230, 1719. [3] S.A. Chernyak, E.V. Suslova, A.S. Ivanov, A.V. Egorov, K.I. Maslakov, S.V. Savilov, V.V. Lunin. Co catalysts supported on oxidized CNTs: Evolution of structureduring preparation, reduction and catalytic test in Fischer-Tropsch synthesis. Applied Catalysis A: General 2016, 523, 221–229.
- Добавил в систему: Черняк Сергей Александрович