ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2017, Vol. 91, No. 7, pp. 1197–1203. © Pleiades Publishing, Ltd., 2017. Original Russian Text © N.S. Kobotaeva, T.S. Skorokhodova, G.I. Razd’yakonova, O.Kh. Poleshchuk, 2017, published in Zhurnal Fizicheskoi Khimii, 2017, Vol. 91, No. 3, pp. 1124–1131.
CHEMICAL KINETICS AND CATALYSIS
Physicochemical Properties and Catalytic Activity of Metal–Carbon Carrier Composite Materials N. S. Kobotaevaa,*, T. S. Skorokhodovaa, G. I. Razd’yakonovab,**, and O. Kh. Poleshchukc,*** aInstitute
of Petroleum Chemistry, Siberian Branch, Russian Academy of Sciences, Tomsk, 634021 Russia Institute of Hydrocarbon Processing, Siberian Branch, Russian Academy of Sciences, Omsk, 644040 Russia c National Research Polytechnical University, Tomsk, 634050 Russia *е-mail:
[email protected] **е-mail:
[email protected] ***е-mail:
[email protected]
b
Received June 16, 2016
Abstract—Composite metal–carbon materials are created on the basis of different kinds of carbon (multiwall carbon nanotubes, carbon black, Sibunit carbon–carbon material) and metals (Ag, Ni, Co), and their physicochemical and catalytic properties are investigated. It is shown that interaction between metals and carbon carriers proceeds not only with the functional groups on the surfaces of the carriers, but also through a system of –C–C– conjugated bonds. Silver deposited on the surface of a carbon carrier has a crystalline structure (dcr = 10–15 nm), while nickel has an amorphous lamellar structure. Based on quantum-chemical calculations using the density functional theory, it is shown that cumene oxidation occurs via a homogeneous–heterogeneous mechanism. Keywords: composite materials, carbon black, Sibunit, carbon nanotubes, catalytic activity DOI: 10.1134/S0036024417070172
INTRODUCTION Carbon materials are now finding increasing application in catalysis as supports for the active components of catalysts. This is due to their specific physicochemical properties, and especially to their chemical inertness and developed surfaces [1–3]. Catalysts on carbon carriers are often better than catalysts on oxide supports. A wide range of catalysts for heavy chemical processes have been obtained on the basis of carbon carriers [1]. Along with such traditional carbon carriers as activated carbons, other carbon materials (e.g., carbon nanotubes, graphitized nanofibers, fullerenes, and various carbon–carbon composite materials) have been widely studied [4–6]. The aim of this work was to obtain metal–carbon carrier composite materials based on different types of carbon (multiwall carbon nanotubes (MWCNTs), carbon black (CB), and the composite carbon–carbon material Sibunit) and metals (Ag, Ni, Co), and to study their physicochemical properties and catalytic activities in the low temperature oxidation of alkylaromatic hydrocarbons with molecular oxygen.
EXPERIMENTAL The following materials were used as our carbon supports: Baytubes C 150 P MWCNTs (Bayer MaterialScience AG) with 3–15 layers, diameters of 13– 16 nm, and lengths of 1–10 μm (NT(B)); P354 carbon black; and Sibunit carbon–carbon composite (Sibunit). The last two were prepared at the Institute of Hydrocarbon Processing, Siberian Branch, Russian Academy of Sciences (Omsk). Surface layer of Sibunit consists of pyrolytic carbon [7]. Carbon black contains 96.4% carbon, 2.5% oxygen, 0.5% sulfur, 0.3% nitrogen, and 0.3% hydrogen [8]. Silver–carbon support (Ag–MWCNT, Ag–CB, Ag–Sibunit) composite and nickel–cobalt–carbon support composite (Ni–Co–MWCNT, Ni–Co–CB, Ni–Co–Sibunit) were also used in this work. We studied the physicochemical properties of the composite materials by the following means. ● Powder X-ray diffraction, using a Shimadzu XRD 7000 diffractometer. Diffraction patterns were obtained using CuKα radiation in the Bragg–Brentano configuration with steps of 0.03, exposures of 6 s, and
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Table 1. Energy, interpretation, and relative intensity of components in the XPS spectra of CB (XPS C 1s) Irel, % Component
E, eV
Group P354 CB
C1
285.0
C=C sp2
71
C2
286.3
C*–CO C*–OH
13
C3
287.3
>C*–O–C
