ISSN 0040-5795, Theoretical Foundations of Chemical Engineering, 2015, Vol. 49, No. 4, pp. 502–511. © Pleiades Publishing, Ltd., 2015. Original Russian Text © A.G. Dedov, A.S. Loktev, D.A. Levchenko, A.A. Karavaev, N.A. Spesivtsev, K.V. Parkhomenko, S.D. Golikov, V.K. Ivanov, A.V. Ishmurzin, A.A. Fomkin, I.I. Moiseev, 2014, published in Khimicheskaya Tekhnologiya, 2014, Vol. 15, No. 5, pp. 268–277. 502 INTRODUCTION The synthesis of aromatic hydrocarbons from lower alkanes attracts increasing attention of both industry and specialists studying the fundamental problems of catalysis [1–6]. The most efficient catalysts for this purpose contain MFI-type (mordenite framework inverted) zeolites [7], which are widely known under the ZSM-5 trademark. These materials are character- ized by ordered channel structure and increased ther- mal stability. It is known that the conversion of light alkanes, i.e., natural and associated petroleum gas components, into aromatic hydrocarbons is catalyzed by Brønsted (B) and Lewis (L) acidic sites of zeolites [1–6, 8–13]. The aromatization of light alkanes (their conver- sion into aromatics) on zeolite catalysts is the subject of numerous studies generalized in a series of reviews [12–17]. The efficiency of bifunctional catalysts based on zeolites containing acidic and dehydrogenating active sites, including the sites in the form of vicinal groups, in the aromatization of light alkanes is shown in [1–17] and many other works. This provokes inter- est in improving the properties of a zeolite catalyst in the reaction of aromatization with the use of promot- ing additives, such as zinc, gallium, indium, cadmium, magnesium, manganese, molybdenum, tungsten, copper, platinum and nonplatinum VIII Group met- als, and rare-earth elements. The objective of this work is to study the effect of the nature of promoters, the alkaline treatment of ZSM-5 zeolites and the method of their synthesis on their structural characteristics and the results of the conversion of a propane-enriched mixture of C 3 –C 4 alkanes. MATERIALS AND METHODS This study deals with the catalysts containing ZSM-5 zeolites, which were synthesized by us under laboratory conditions and produced by OAO Novosi- birsk Chemical Concentrates Plant (Table 1). Labora- torial ZSM-5 samples were synthesized hydrother- mally by heating aqueous solutions of precursors (tet- raethoxysilane, sodium aluminate, tetrapropylammonium hydroxide) in a Teflon- inserted autoclave or exposing the same mixture in a DAP-100 Teflon autoclave to microwaves using a Speedware 4 temperature- and pressure-controlled microwave digestion system. The synthesized zeolites were converted into the hydrogenated (HZSM-5) form by means of multiple ion exchanges in an aque- ous ammonium nitrate solution with subsequent dry- ing and calcination. Industrial catalyst samples were tested in the same form in which they were received from the manufac- turer, or additionally promoted with a calculated Effect of the Nature of Promoters, the Alkaline Treatment of ZSM-5 Zeolites, and the Method of Their Synthesis on the Conversion of C 3 –C 4 Alkanes A. G. Dedov a , A. S. Loktev a , D. A. Levchenko a , A. A. Karavaev a , N. A. Spesivtsev a , K. V. Parkhomenko b , S. D. Golikov a , V. K. Ivanov d , A. V. Ishmurzin c , A. A. Fomkin d , and I. I. Moiseev a a Gubkin Russian State University of Oil and Gas, Leninskii pr. 65, Moscow, 119991 Russia b Université de Strasbourg, rue de Blaise Pascal 4, Strasbourg, CEDEX F-67081 France c OAO Gazprom, ul. Nametkina 16, Moscow, 117997 Russia d Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991 Russia e-mail: genchem@gubkin.ru, parkhomenko@unistra.fr Received January 27, 2014 Abstract—The zinc and chromium copromotion of an industrial ZSM-5 zeolite and its structural analogues synthesized under laboratorial conditions by the hydrothermal and microwave-assisted hydrothermal meth- ods increases the selectivity towards the formation of aromatics from a mixture of C 3 –C 4 alkanes. The for- mation of additional mesopores in the structure of ZSM-5 also improves the selectivity to aromatic hydrocar- bons. Keywords: ZSM-5 zeolites, promoters, aromatization, C 3 –C 4 alkanes DOI: 10.1134/S0040579515040077 CATALYTIC PROCESSES