Dialkylation of Naphthalene with Isopropanol Over H 3 PO 4 /MCM-41 Catalysts for the Environmentally Friendly Synthesis
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Dialkylation of Naphthalene with Isopropanol Over H3PO4/MCM-41 Catalysts for the Environmentally Friendly Synthesis of 2,6-Dialkylnaphthalene M. Ghiaci • B. Aghabarari • V. Rives • M. A. Vicente I. Sobrados • J. Sanz
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Received: 23 December 2009 / Accepted: 5 February 2010 / Published online: 23 February 2010 Ó Springer Science+Business Media, LLC 2010
Abstract AlMCM-41 materials with SiO2/Al2O3 molar ratios 20, 70, 110, 150, 200, and Si-MCM-41 were synthesized following standard procedures, and loaded with different amounts of H3PO4. The catalysts were well characterized by powder X-ray diffraction (XRD), nitrogen adsorption studies, and solid state 29Si, 27Al, 31P, 23Na and 1 H MAS NMR spectroscopy. Acidity measurement by FTIR spectroscopy monitoring of pyridine adsorption reveals that the incorporation of Al in the framework generates Brønsted and Lewis acidity, which increases with the increase in metal content. By loading H3PO4 on the AlMCM-41, Brønsted sites increases substantially, but the Lewis sites decrease to a large extent. Liquid phase isopropylation of naphthalene with isopropanol in n-hexane under autogeneous pressure was performed in the temperature range 473–623 K. The optimum feed molar ratio was found to be 1:2:10 (naphthalene:isopropanol:n-hexane), where the naphthalene conversion reaches to 85.5%. The b-and b,b-selectivities over 30 wt% H3PO4/AlMCM41(200) were 97.0 and 84.8, respectively, at 85.5% conversion. The main products of the reaction, mono and M. Ghiaci (&) B. Aghabarari Department of Chemistry, Isfahan University of Technology, Isfahan 8415683111, Iran e-mail: [email protected] V. Rives (&) M. A. Vicente (&) GIR-QUESCAT, Departamento de Quı´mica Inorga´nica, Universidad de Salamanca, 37008 Salamanca, Spain e-mail: [email protected] M. A. Vicente e-mail: [email protected] I. Sobrados J. Sanz Instituto de Ciencia de Materiales, C.S.I.C., C/Sor Juana Ine´s de la Cruz, 3, 28049 Cantoblanco, Madrid, Spain
diisopropylnaphthalenes, were analyzed and identified by gas chromatography and confirmed by GC–MS. The conversion and selectivity of the products are discussed from the point of view of catalyst characteristics and reaction conditions. Keywords Naphthalene Isopropanol 2-Isopropylnaphthalene 2,6-Di-isopropylnaphthlene H3PO4 AlMCM-41
1 Introduction Zeolites are used in alkylation reactions due to their activity, selectivity, thermal stability, reusability and ecofriendly nature. Naphthalene and its derivatives are rich in some refinery streams and in liquids derived from coals via carbonization, pyrolysis and liquefaction. Among the Friedel–Crafts reactions, selective alkylation of naphthalene to b mono- and b,b-dialkylated products is of practical relevance. 2-Naphthol, key intermediate for dyes, pharmaceuticals, and perfumes, can be obtained from 2-alkylnaphthalenes [1]. A diisopropylnaphthalene (DIPN) mixture is used as a high-quality solvent for copying materials [2]. Especially advantageous is the presence of a high content of 2,7-diisopropylnaphthalene in the solve
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