Synthesis of Aluminum Oxides with Controlled Textural and Strength Parameters
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GANIC SYNTHESIS AND INDUSTRIAL INORGANIC CHEMISTRY
Synthesis of Aluminum Oxides with Controlled Textural and Strength Parameters A. S. Zaguzina,*, A. V. Romanenkoa, and M. V. Bukhtiyarovaa a Boreskov
Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090 Russia *e-mail: [email protected] Received October 26, 2019; revised March 13, 2020; accepted April 9, 2020
Abstract—The effect of a number of burn out additives introduced into the composition of pastes prepared on the basis of aluminum hydroxide, Pural SCF-55, and the modes of sample calcination on the texture and strength parameters of the obtained aluminum oxides has been investigated. The additives are represented by three types of carbon blacks: acetylene, Vulcan XC-72, and Katjenblack EC-300J, as well as ultrafine diamonds, oxidized graphite, egg white, and bovine albumin. It is shown that the introduction of burn out additives affects both the mesoporous and macroporous structure of the support and leads to the formation of transport pores up to 10 μm in size. It has been established that calcining the formed aluminum hydroxide granules, including the considered carbon blacks, in air at 600°C with a preliminary rise in temperature to 450°C in an argon atmosphere makes it possible to obtain Al2O3 with higher crushing strength. Keywords: aluminum oxide, carbon, carbon black, burn-out additives, pseudoboehmite DOI: 10.1134/S1070427220080029
Aluminum oxides are widely used as sorbents and desiccants. The share of their consumption in the composition of catalyst components is steadily increasing, primarily as carriers for oil refining processes such as hydrocracking, reforming, hydrotreating, as well as for the dehydrogenation of light hydrocarbons. This fact is due to the possibility of the targeted formation of various modifications of aluminum oxide (γ-, η-, θ-Al2O3, etc.) with the required textural and strength parameters and a given surface state, which ensure the production of effective catalysts (activity, selectivity, thermal, corrosion resistance) for the developed processes. The nature of chemical processes involving supported catalysts is largely determined by the porous structure of the used support, which can be represented by micro-, meso- and macropores. Conventionally, micro- and mesopores, in which the main catalytic transformations take place, include pores less than 2 and 2–50 nm in size, respectively, and macropores, are transport pores with a size of more than 50 nm [1]. In catalytic processes with the participation of “large” molecules, when a significant amount of the
active component is localized in micropores and on the surface of narrow mesopores, diffusion restrictions arise. Therefore, to increase the efficiency of catalysts, it is necessary either to develop complex techniques that reduce the amount of particles formed in narrow pores during the deposition of an active component, or to use meso- and macroporous carriers with a large mesopore size. It should be noted that in the second case, negative e
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