Synthesis of a Catalyst for Isobutane/Butylenes Alkylation Promising for Industrial Application
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hesis of a Catalyst for Isobutane/Butylenes Alkylation Promising for Industrial Application I. M. Gerzelieva, *, V. A. Temnikovaa, Z. A. Saitova, b, D. F. Asylbaeva, and M. N. Baskhanovaa aTopchiev
Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia AO Khadzhiev Elektrogorsk Institute of Oil Refining, Elektrogorsk, Moscow oblast, 142530 Russia *e-mail: [email protected]
b
Received May 29, 2020; revised June 1, 2020; accepted June 11, 2020
Abstract—A comparative study of two methods of ion exchange of a NaX zeolite molded with a binder is performed. The first method (I) consists in the successive treatment of the zeolite with solutions of calcium, lanthanum, and ammonium nitrates at 80°C under stirring over granules with the use of intermediate dryings and calcinations after each ion exchange. The second method (II) involves the successive hydrothermal treatment of the zeolite with the solutions of the salts at 140°C with intermediate rinsings. It is found that an almost complete replacement of sodium cations in the zeolite lattice (no more than 0.6 wt % of residual Na2O) requires a threefold ion exchange by method II and a fourfold ion exchange by method I. Comparing the physicochemical and catalytic properties of the obtained samples shows the advantage of ion exchange by method II due to preservation of the initial structural characteristics of the zeolite and, hence, higher concentration and strength of acid sites. Keywords: catalyst synthesis unit, ion exchange, NaX zeolite, heterogeneous alkylation catalyst, alkylation of isobutane with butylenes DOI: 10.1134/S0965544120100035
One of the key processes of deep petroleum processing, the production of alkyl gasoline, is performed in the presence of catalysts (sulfuric or hydrofluoric acid). The main disadvantage of their use is the negative effect on the environment; therefore, the search for green catalysts is a topical issue. An alternative is provided by zeolite catalysts, in particular, based on faujasite-type zeolites [1]. It was shown [2] that catalysts based on an X-type zeolite with a low Si/Al ratio manifest higher catalytic activity in the alkylation reaction of isobutane with olefins than Y-type analogs. The efficiency of catalysis can be noticeably increased by increasing the depth of ion exchange in the zeolite to achieve a high degree of replacement of sodium cations (up to 98 wt %) with calcium, ammonium, and rear-earth element cations; in this case, the catalytic activity of the zeolite catalysts noticeably increases due to a change in the type of acid sites in the zeolite [3]. Ion exchange is generally carried out at temperatures of up to 90°C under stirring over granules; intermediate stages of drying and calcination of the treated zeolite are needed after each ion exchange [4]. This method is labor-intensive and time-consuming. A more technological method of ion exchange is hydrothermal treatment in an autoclave, which makes it possible to exclude the intermediate stages of drying and calcination [5].
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