Selective hydrogenation of phenol to cyclohexanone catalyzed by palladium nanoparticles supported on alumina/lanthanide
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Selective hydrogenation of phenol to cyclohexanone catalyzed by palladium nanoparticles supported on alumina/lanthanide oxides Mehrnaz Aliahmadi1 · Monireh Davoudi1 · Ali Nemati Kharat1 Received: 20 July 2020 / Accepted: 18 October 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Palladium nanoparticles supported on mixture of alumina and lanthanide oxides were synthesized and employed for one stage hydrogenation of phenol to cyclohexanone. A conversion of 99.8% with a selectivity of 96.3% to cyclohexanone was obtained using Pd supported on alumina/lanthanum oxide/cerium oxide with mole ratio of 9:1:1 at mild condition of 80 °C and low H2 pressure of 3 bar. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and volumetric isothermal nitrogen gas adsorption-desorption method (BET) were used for characterization of prepared catalysts. Keywords Phenol hydrogenation · Supported Palladium · alumina/lanthanum oxide · Cyclohexanone · Nano particles
Introduction Cyclohexanone is an important organic compound because of its utilization as a precursor to fabrication of caprolactam and adipic acid for nylon-6 and nylon-66, respectively [1]. Industrially, cyclohexanone is produced through cyclohexane oxidation [2] or Asahi process [3]. The first route requires harsh reaction conditions such as high temperature and pressure, producing undesirable byproducts which are complicatedly separated and suffers low cyclohexanone yield [4, 5]. In Asahi process benzene is partially hydrogenated to cyclohexene which is then hydrated to cyclohexanol, and cyclohexanol is subsequently dehydrogenated to cyclohexanone [3]. Hydrogenation of phenol is an alternative desired strategy for synthesis of cyclohexanone that can be done either in two-step or one-step process [6]. The two-step process involves hydrogenation of phenol to cyclohexanol followed * Ali Nemati Kharat [email protected] 1
School of Chemistry, College of Science, University of Tehran, Tehran, Iran
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Reaction Kinetics, Mechanisms and Catalysis
by dehydrogenation to cyclohexanone [7]. The one-step hydrogenation of phenol to cyclohexanone avoids dehydrogenation step and favors cyclohexanone formation [8]. Therefore, direct hydrogenation process by simplifying reaction steps and improving hydrogen utilization while facilitating separation of cyclohexanone and cyclohexanol having approximately same boiling point is more preferable from the viewpoints of cost and energy saving [9, 10]. Cyclohexanone is rather active and can undergo further hydrogenation to cyclohexanol or other undesired adducts [11]. In order to overcome the drawbacks, considerable efforts have been made to develop effective catalysts for this catalytic system. Catalytic hydrogenation of phenol has extensively been conducted over various metals such as Ni [12], Pd [13, 14], Pt [15], Rh [16], and Ru [17] in both gas [13] and liquid phase [18]. It has been established that Pd exhibits the best performance among other noble metal catalysts [13, 14]. Haruhiko et al
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