Conversion of Dimethyl Ether to a Triptane-Enriched Mixture of Liquid Hydrocarbons: Influence of Modifier and Reaction C
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LYSIS
Conversion of Dimethyl Ether to a Triptane-Enriched Mixture of Liquid Hydrocarbons: Influence of Modifier and Reaction Conditions Z. M. Matievaa,*, Yu. M. Snatenkovaa, N. V. Kolesnichenkoa, and A. L. Maksimova a
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received February 17, 2020; revised May 18, 2020; accepted June 9, 2020
Abstract—The influence of the active element in the alkylation catalyst as a component of a combined catalyst for the production of liquid hydrocarbons with increased triptane content from dimethyl ether was studied. A mixture of liquid hydrocarbons containing more than 8.5 wt % triptane was prepared under the optimum conditions (temperature 340°С, pressure 10 MPa, dimethyl ether weight space velocity 4 h–1) on a combined catalyst in the form of a physical mixture of catalysts (mean grain size 2–4 mm) for the synthesis of lower olefins, based on Mgmodified НZSM-5 zeolite, and for the alkylation, based on La- and Pd-modified HY zeolite. Keywords: НZSM-5 zeolite, НY zeolite, dimethyl ether, liquid hydrocarbons, triptane DOI: 10.1134/S1070427220080200
A catalytic process for the conversion of methanol to a mixture of aliphatic and aromatic hydrocarbons on HZSM-5 zeolite (MTG process) is being actively developed and has been brought to commercial implementation [1]. After the development of a onestep procedure for producing dimethyl ether, which is an intermediate product of the conversion of nonpetroleum feedstock to valuable chemical products, the process for producing liquid hydrocarbons from syngas via dimethyl ether has become more promising [2]. Interest in this research field steadily increases [3–7], especially concerning production of high-octane environmentally clean automobile fuel enriched in isoparaffins [8]. Isoparaffins with high octane number are ideal components of hydrocarbon fuels. Their complete combustion is reached owing to high hydrogen-tocarbon ratio in their composition. The most valuable high-octane component of gasoline among С5–С8 isoparaffins is triptane (2,2,3-trimethylbutane). Owing to highly branched structure and high octane number equal to 112, triptane is particularly effective for replacing aromatic components in the fuel [8, 9]. Today there are no acceptable methods for triptane production that could be recommended for commercial implementation
because of low values of the dimethyl ether conversion and triptane yield [10–15]. Previously we prepared a liquid synthetic product containing more than 8.5 wt % 2,2,3-trimethylbutane and no more than 0.5 wt % aromatic compounds on a combined catalyst consisting of a catalyst for the synthesis of lower С2–С4 olefins and of an alkylation catalyst. The reaction conditions were relatively harsh (340°С, 10 MPa) [16]. Despite practical absence of aromatic compounds, the product had research and motor octane numbers of 84.5 and 82.0, respectively [16]. In this work, we studied how the selectivity with respect to a mixture of liquid hydrocarbons with increa
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