Influence of the Preparation Method on the Physicochemical and Catalytic Properties of Platinum Catalysts Supported on B
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uence of the Preparation Method on the Physicochemical and Catalytic Properties of Platinum Catalysts Supported on Bayerite Alumina for the Partial Oxidation Reactions of Hydrocarbons K. I. Shefera, b, *, L. M. Kovtunovaa, b, V. N. Rogozhnikova, O. A. Stonkusa, b, T. V. Larinaa, and I. A. Chetyrina aBoreskov
Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia b Novosibirsk State University, Novosibirsk, 630090 Russia *e-mail: [email protected] Received December 26, 2019; revised April 9, 2020; accepted April 21, 2020
Abstract—Platinum catalysts supported onto bayerite alumina were synthesized and studied. Alumina of the θ-Al2O3 type, which was prepared from metallic aluminum by an aluminate method, was used as a support, and platinum(IV) nitrate and hydrogen hexachloroplatinate(IV) precursors containing Pt4+ ions were used for supporting an active component. The catalysts were studied by physicochemical methods such as X-ray phase analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, and ultraviolet-visible diffuse reflection spectroscopy. It was found that platinum occurred in a finely dispersed state in both of the catalysts, and it was uniformly distributed over the support surface. The particle sizes were 2.8 and 0.9 nm in the samples synthesized from platinum(IV) nitrate and hydrogen hexachloroplatinate(IV), respectively. The most uniform surface distribution, high dispersity, and a narrow particle-size distribution were obtained with the use of hydrogen hexachloroplatinate(IV). The catalysts were tested in the partial oxidation of natural gas. The catalyst synthesized using platinum(IV) nitrate afforded an almost thermodynamically equilibrium distribution of the reaction products of partial oxidation at a temperature of 700–800°С. Keywords: supported catalysts, platinum, alumina, partial oxidation of hydrocarbons DOI: 10.1134/S0023158420050092
INTRODUCTION Alumina–platinum catalysts are widely used in oil refining, petroleum chemistry, gas treatment processes, hydrogen energetics, and related areas. Hydrogen can be obtained as a result of the partial oxidation of hydrocarbons, and synthesis gas formed in this reaction can be used for the manufacture of various chemical products [1, 2]. Noble metals and, in particular, platinum are the best active components of catalysts for the partial oxidation of hydrocarbons [3–9]. The activity of a platinum catalyst depends on both the particle size of platinum [3] and the amount of ionic platinum species [4, 5]. It was found that, as a result of strong interaction with the support, the metal in alumina–platinum catalysts occurs in an electron-deficient state in the form of ions embedded in the surface layers of aluminum oxide at defect sites in the oxide structure [6, 7]; in this case, an antibatic relationship between the amount of Abbreviations: XPS, X-ray photoelectron spectroscopy; TEM, transmission electron microscopy; UV-Vis DRS, ultraviolet-visible diffuse reflectance spectroscopy; CSR, cohere
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