A High-Performance Aluminum Oxide Desiccant
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A High-Performance Aluminum Oxide Desiccant V. Yu. Kruglyakova, *, A. V. Glazyrina, **, E. P. Meshcheryakovb, ***, I. A. Kurzinab, ****, and L. A. Isupovaa, ***** a
Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia bNational Research Tomsk State University, Tomsk, 634050 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] ****e-mail: [email protected] *****e-mail: [email protected] Received June 20, 2019; revised September 6, 2019; accepted September 10, 2019
Abstract—A study is performed of the effect of the conditions of preparation (the nature and amount of alkali used to hydrate a gibbsite thermal activation product and the amount of nitric acid (acid modulus value) in preparing a moldable paste) on the properties of aluminum oxide desiccants. A desiccant is obtained that has higher dynamic capacity (more than 10.0 g/100 g) at close specific surface values of around 300 m2/g and higher static capacity (20–22 g/100 g) than foreign and Russian analogues. The desiccant has high strength of more than 8.0 MPa. Such a desiccant can improve the productivity of existing adsorbers and reduce the cost of sorbent regeneration, which is of undoubted practical interest. Keywords: aluminum oxide, desiccant, alkaline modification, dynamic capacity DOI: 10.1134/S2070050420030083
INTRODUCTION Aluminum oxide desiccants are widely used to dry various media, including natural gas, due to their high efficiency (especially when drying wet gases), considerable mechanical strength, stability in humid atmospheres, available raw materials, and multiple regeneration with minimal energy costs [1–4]. The most attractive ways of preparing them require use of the products of gibbsite thermoactivation to obtain granular active aluminum oxides of different low-temperature modifications (η-Al2O3. γ-Al2O3 or χ-Al2O3) without stages of precipitation. χ-Al2O3 spherical pellets can be prepared via the plate-shaped granulation of a product of gibbsite thermal activation [4–7], while γ-Al2O3, η-Al2O3 cylindrical, or more complex pellets are obtained via the extrusion molding of hydrated products of thermal activation [8–10]. Axens, Alcoa, Alumac, Albemarle, and BASF are the best known manufacturers of aluminum oxide desiccants. In Russia, desiccants are produced via thermal activation technology at NKZ, SKTB Katalizator, and KNTgroup. The adsorption of water with desiccants is due to (1) the chemisorption or dissociative adsorption of water molecules on active sites of a surface of aluminum oxide to form a first layer, (2) physical adsorption to form multilayers with hydrogen bonds, and (3) capillary condensation in pores due to the growth
of multilayers and condensation at temperatures above the dew point in the gas phase [1, 3]. As a result, the efficiency of adsorbents and their static and dynamic capacities depend on the structural modification of aluminum oxide (η-Al2O3, γ-Al2O3, and χ-Al2O3) and the conditions of
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