A Catalyst System Based on Copper(II) Bromide Supported on Zeolite HY with a Hierarchical Pore Structure in Benzyl Butyl
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Catalyst System Based on Copper(II) Bromide Supported on Zeolite HY with a Hierarchical Pore Structure in Benzyl Butyl Ether Synthesis A. R. Bayguzinaa, *, L. I. Gallyamovaa, M. R. Agliullina, and R. I. Khusnutdinova aInstitute
of Petroleum Chemistry and Catalysis, Russian Academy of Sciences, Ufa, Republic of Bashkortostan, 450075 Russia *e-mail: [email protected] Received February 12, 2020; revised March 13, 2020; accepted April 10, 2020
Abstract—Novel catalyst systems based on CuBr2 supported on zeolite HY with a hierarchical pore structure have been proposed for benzyl butyl ether synthesis by the intermolecular dehydration of benzyl and butyl alcohols. It has been shown that catalyst systems with a CuBr2 content of ~10 wt % provide a benzyl butyl ether yield of ~95% at 150°C. Keywords: benzyl butyl ether, intermolecular dehydration, benzyl alcohol, n-butyl alcohol, copper(II) bromide, micro–meso–macroporous zeolite HY DOI: 10.1134/S0965544120080034
Benzyl alkyl ethers hold an important position in the class of ethers. Benzyl methyl and benzyl butyl ethers characterized by a pleasant fruity odor are commonly used in actual practice. Of all benzyl alkyl ethers, benzyl butyl ether is most in demand and, having a low toxicity, it is used to flavor food products (drinks, pastry, ice cream), perfumes, and cosmetics [1].Benzyl alkyl ethers can be synthesized by several methods. The most selective method to synthesize these ethers is the Williamson ether synthesis, which is based on the reaction of alkali metal alcoholates with benzyl halides [2–4] or the reaction of benzyl alcohol with alkyl halides in the presence of bases and phase transfer catalysts [5, 6].There are published data on the efficient synthesis of benzyl alkyl ethers in the presence of metal complex catalysts [7]. Thus, Tsai et al. [8] synthesized benzyl methyl ether with a yield of 20% by the TiCl4-activated (0.3 equiv) reaction of benzyl alcohol with methanol. A similar reaction is implemented using transition metal complexes, such as rhenium [ReBr(CO)5] [9] and iridium IrCl2Cp*(NHC) [10]. Disadvantages of metal complex catalysts are a low selectivity, which is due to the formation of all three possible ethers (dialkyl, dibenzyl, and benzylalkyl); a low water stability; a high cost; and the impossibility of reusing. It is known that heterogeneous catalysis has a number of advantages over homogeneous catalysis, namely, a low catalyst consumption; reusability; a long lifetime; the absence of necessity to extract the catalyst from solution, because it is readily separated from the reaction mixture; and a decrease in the amount of waste.
Zeolites have a developed microporous structure and contain Brønsted acid sites; therefore, they attract considerable attention as acid catalysts and their supports [11]. Particular attention has recently been paid to zeolite materials with a hierarchical pore structure, which, owing to the presence of meso- and macropores, provide a better diffusion of reactants and products; this feature provides a higher acti
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