Immobilized ionic liquid on the zeolite: its characterization and catalytic activity in the synthesis of coumarins via P
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ORIGINAL PAPER
Immobilized ionic liquid on the zeolite: its characterization and catalytic activity in the synthesis of coumarins via Pechmann reaction Mojgan Zendehdel1,2 · Soheila Khaghaninejad1,2 · Fatemeh Tavakoli1,2 · Shiva Ganji1,2 Received: 20 December 2019 / Accepted: 4 May 2020 © Iranian Chemical Society 2020
Abstract In this work, in the first step, the 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride ([MTMSPIm]Cl) is immobilized on HY and NaY zeolites as an acidic catalyst. The synthesized catalysts were well characterized by different methods such as FTIR, TGA, XRD, BET, SEM, EDX and ICP. The characterizations of catalysts indeed show the ionic liquid supported on amine-functionalized zeolites. Also, the result shows the micro-/mesoporous structure for catalysts which have been emerged as an important class of catalytic materials. The micro-/mesocatalyst ([MTMSPIm]Cl@zeolite) was used as an acidic catalyst to synthesize coumarins via Pechmann reaction in solvent-free condition. The effect of different factors such as catalyst amount, solvent and time was investigated. Finally, catalyst can be easily separated and reused for the next reactions at least for five runs without any significant changes in yield and structure of the catalyst. Comparison of modified zeolite with [MTMSPIm]Cl shows higher yield and selectivity and mild condition related to other works. Keywords ([mtmspim]cl@zeolite) · Micro-/mesostructure · Ionic liquids · Pechmann reaction
Introduction In the past decades, interest in ionic liquids (ILs) has been increased for organic reactions due to their unique properties such as solubility, very low vapor pressure, low toxicity, high chemical and thermal stabilities, which are often named as green solvents [1]. Also, ILs show good catalytic activity and high selectivity as a homogeneous catalyst for organic reaction. But ionic liquids are very expensive, and many efforts are made on the basis of economic * Mojgan Zendehdel m‑[email protected]; [email protected] Soheila Khaghaninejad S‑[email protected] Fatemeh Tavakoli F‑[email protected] Shiva Ganji [email protected] 1
Department of Chemistry, Faculty of Science, Arak University, Arāk 38156‑8‑8349, Iran
Institute of Nanosciences and Nanotechnology, Arak University, Arāk, Iran
2
criteria to minimize the amount of ILs in the reactions [2]. We know homogenous catalysts have some limited use, because usually separating them from the reaction products is difficult, which may lead to environmental and economic problems, especially in the case of expensive and toxic catalyst. Recently, to overcome these limitations, the immobilization of ionic liquid onto some solid supports such as polymer, complex, magnetite nanoparticles, graphene and mesoporous materials has been developed [3–5]. Zeolites are crystalline microporous aluminosilicate which have Brøonsted and Lewis sites, act as solid acid catalysts and are used as a support for heterogeneous catalyst [6–9]. Although zeolites have many advanta
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