Isobutane/1-butene Alkylation Performance of Ammonium Fluoride-Modified HUSY Zeolite
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Isobutane/1‑butene Alkylation Performance of Ammonium Fluoride‑Modified HUSY Zeolite Jing Liu1 · Ning Ding1 · Xuesi Hong2 · Sinong Zhou1 · Xiaolong Zhou1 · Jin An Wang3 · Lifang Chen3 Received: 19 December 2019 / Accepted: 13 March 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A series of modified HUSY zeolites were prepared by immersing with different concentration of NH4F solution at low temperature, and their catalytic performance for isobutane/1-butene alkylation reaction was investigated. The physicochemical properties of modified catalysts were characterized by XRD, N 2 adsorption–desorption isotherms, ICP, pyridine-IR and SEM. The results indicated that HUSY zeolite with higher Si/Al ratio is more sensitive to NH4F leaching, resulting in more severe structural amorphization. N H4F modification affects not only the pore structure but also the acid properties. The amount of Lewis acid sites on the modified zeolites was reduced and the ratio of Brønsted/Lewis acid sites was significantly enhanced in comparison with that of parent zeolite. Such properties of modified zeolites account for the superior performance for isobutane/1-butene alkylation. The initial C8 selectivity was increased to 74 wt% over the modified HUSY (Si/Al = 2.7) zeolite using 5 wt% NH4F solution, which was about 15 wt% higher than that achieved on the HUSY parent. TG and in situ IR analyses of the deactivated catalyst indicated that some deposits were formed on the catalyst and the alkylation activity could be restored by regeneration at suitable conditions (520 °C under air atmosphere). Graphic Abstract
Keywords HUSY · Ammonium fluoride · Isobutane/butene alkylation · Acid property · Regeneration
1 Introduction
* Xuesi Hong * Xiaolong Zhou [email protected] Extended author information available on the last page of the article
Nowadays, the regulation of gasoline is becoming increasingly strict. Alkylate is an excellent blending component for clean gasoline, which has high octane number, low Reid vapor pressure (RVP) and nearly no aromatics, alkenes and sulfur [1]. Traditionally, the industrial alkylation reactions are mostly catalyzed using inorganic acid
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including hydrofluoric acid (HF) and sulfuric acid (H2SO4) in petroleum refineries. Polymerization reaction occurs rapidly when using H 2SO 4 as a catalyst, resulting in a number of byproducts containing heavy hydrocarbons and spent acids; while the primary problem of HF is its volatility and high corrosivity [2]. In recent years, environmentfriendly ionic liquid catalyst has attracted much attention from researchers [3–5]. However, its severe synthesis conditions and high cost may impede the wide application in alkylation industry. Consequently, the solid acid catalysts are expected to be the alternative in the future. So far, various solid acid catalysts have been investigated widely, especially zeolitic catalysts, among which Y and Beta zeolites predominate [6, 7]. However, the rapid deactivation due to
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