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Noble Metal Nanoparticles Stabilized by Hyper-Cross-Linked Polystyrene As Effective Catalysts in Hydrogenation of Arenes

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Noble Metal Nanoparticles Stabilized by Hyper-Cross-Linked Polystyrene As Effective Catalysts in Hydrogenation of Arenes molecules Article Noble Metal Nanoparticles Stabilized by Hyper-Cross-Linked Polystyrene as Effective Catalysts in Hydrogenation of Arenes Elena S. Bakhvalova 1, Arina O. Pinyukova 2, Alexey V. Mikheev 2, Galina N. Demidenko 2, Mikhail G. Sulman 2, Alexey V. Bykov 2, Linda Z. Nikoshvili 2,* and Lioubov Kiwi-Minsker 1,3,* 1 Regional Technological Centre, Tver State University, Zhelyabova Str., 33, 170100 Tver, Russia; [email protected] 2 Department of Biotechnology, Chemistry and Standardization, Tver State Technical University, A.Nikitina Str., 22, 170026 Tver, Russia; [email protected] (A.O.P.); [email protected] (A.V.M.); [email protected] (G.N.D.); [email protected] (M.G.S.); [email protected] (A.V.B.) 3 Department of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne (GGRC-ISIC-EPFL), CH-1015 Lausanne, Switzerland * Correspondence: [email protected] (L.Z.N.); lioubov.kiwi-minsker@epfl.ch (L.K.-M.); Tel.: +7-904-005-7791 (L.Z.N.); +41-21-693-3182 (L.K.-M.) Abstract: This work is addressing the arenes’ hydrogenation—the processes of high importance for petrochemical, chemical and pharmaceutical industries. Noble metal (Pd, Pt, Ru) nanoparticles (NPs) stabilized in hyper-cross-linked polystyrene (HPS) were shown to be active and selective catalysts in hydrogenation of a wide range of arenes (monocyclic, condensed, substituted, etc.) in a batch mode. HPS effectively stabilized metal NPs during hydrogenation in different medium (water, organic Citation: Bakhvalova, E.S.; Pinyukova, A.O.; Mikheev, A.V.; solvents) and allowed multiple catalyst reuses. Demidenko, G.N.; Sulman, M.G.; Bykov, A.V.; Nikoshvili, L.Z.; Keywords: polymeric catalysts; hydrogenation of arenes; noble metals; hyper-cross-linked Kiwi-Minsker, L. Noble Metal polystyrene; catalyst stability Nanoparticles Stabilized by Hyper-Cross-Linked Polystyrene as Effective Catalysts in Hydrogenation of Arenes. Molecules 2021, 26, 4687. 1. Introduction https://doi.org/10.3390/ Hydrogenation of different arenes, mono- and polycyclic, and their mixtures are molecules26154687 highly used in modern industries: refining of fuels; hydrogenation of benzene (BZ) to cyclohexane (CH) for the synthesis of caprolactam and toluene (TOL) to methylcyclohexane Academic Editor: Federico Cesano (MCH); hydrogenation of naphthalene (NL) in the synthesis of tetralin (TL) and decalin (industrial hydrogen donors and solvents used for extraction); hydrogenation of aniline Received: 30 June 2021 (AN) and its derivatives for the production of anticorrosive additives. All these reactions Accepted: 31 July 2021 Published: 3 August 2021 are energy-intensive, large-capacity petrochemical processes that produce reagents for chemical and pharmaceutical industries, and are used for reduction of residuals in fuels Publisher’s Note: MDPI stays neutral and lubricants [1–4]. with regard to jurisdictional claims in Most methods for the production of functionalized and nonfunctionalized cycloalka- published maps and institutional affil- nes from BZ, NL, polyarenes, and their derivatives are based on gas-phase catalytic pro- iations. cesses. Such processes have a number of disadvantages: high temperatures of vapor–gas mixture and nonuniform heat removal resulting in catalyst deactivation; catalyst abrasion and metal loss in the case of fluidized bed reactors. Liquid-phase hydrogenation of arenes is carried out at much lower temperatures using catalytic systems based mainly on nickel or noble metals (Pt, Pd, Ru, Rh) deposited on inorganic supports, but is less studied [5–7]. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. The conditions for hydrogenation of aromatics are selected depending on the con- This article is an open access article centration of sulfur-containing impurities in the raw material [8]. If BZ is almost free of distributed under the terms and sulfur compounds, the reaction is carried out in the presence of low-temperature catalysts conditions of the Creative Commons at low hydrogen pressure. The BZ containing sulfur impurities must be hydrogenated over Attribution (CC BY) license (https:// sulfur-resistant catalysts under more harsh conditions. Nickel catalysts, in comparison creativecommons.org/licenses/by/ with platinum group metals, are preferred for hydrogenation of sulfur-containing raw 4.0/). materials since they are more resistant to sulfur poisoning. Molecules 2021, 26, 4687. https://doi.org/10.3390/molecules26154687 https://www.mdpi.com/journal/molecules Molecules 2021, 26, x FOR PEER REVIEW 2 of 15 ated over sulfur-resistant catalysts under more harsh conditions. Nickel catalysts, in Molecules 2021, 26, 4687 comparison with platinum group metals, are preferred for hydrogenation of 2sul- of 15 fur-containing raw materials since they are more resistant to sulfur poisoning. The use of different inorganic supports (e.g., alumina, silica, zeolites) allows high catalyst activity and selectivity; however, their acidic properties provoke carbon deposi- tion. TheMoreover, use of active different metal inorganic phase deposited supports on (e.g., inorganic alumina, supports silica, is zeolites) often unstable allows highand undergoescatalyst activity sintering, and selectivity; resulting however,in catalyst their deactivation. acidic properties The use provoke of polymeric carbon deposition.supports bringsMoreover, a big active advantage: metal phase the catalytically deposited onactive inorganic phase supportsis well stabilized is often unstable within cavities and un- distributeddergoes sintering, over the resulting entire volume in catalyst of the deactivation. polymer and The becomes use of polymeric fully accessible supports to bringsreac- tantsa big advantage:when the support the catalytically swells. Moreover, active phase polymeric is well stabilizedsupports withinare usually cavities hydrophobic, distributed andover are the suitable entire volume for organic of the solvents. polymer and becomes fully accessible to reactants when the supportIn this swells. work, Moreover, for the first polymeric time, supportshydrogenation are usually by molecular hydrophobic, hydrogen and areof suitablea wide rangefor organic of arenes solvents. (monocyclic and condensed, substituted and nonsubstituted) was stud- ied overIn this noble work, metal for (Pd, the firstPt, Ru) time, NPs hydrogenation supported on by hyper-cross-linked molecular hydrogen polystyrene of a wide (HPS)range ofof arenestwo types: (monocyclic MN270 and (nonfunctionalized) condensed, substituted and MN100 and nonsubstituted) (bearing tertiary was studiedamino over noble metal (Pd, Pt, Ru) NPs supported on hyper-cross-linked polystyrene (HPS) of groups and designated as HPS-NR2). two types:It is noteworthy MN270 (nonfunctionalized) that, to date, there and are MN100 only a (bearing few reports tertiary on aminothe use groups of poly- and mer-baseddesignated catalysts as HPS-NR in hydrogenation2). of arenes. The most recent work, of Davankov et al. [9], wasIt is devoted noteworthy to the that, hydrogenation to date, there areof BZ, only TOL, a few TL, reports and onphenol the use (PL) of using polymer-based Pd NPs catalysts in hydrogenation of arenes. The most recent work, of Davankov et al. [9], was supported on the HPS of MN200-type (analogue of MN270, but with larger me- devoted to the hydrogenation of BZ, TOL, TL, and phenol (PL) using Pd NPs supported so-/macro-pores with a mean diameter of 70 nm). It was shown that, using supercritical on the HPS of MN200-type (analogue of MN270, but with larger meso-/macro-pores with CO2 or methylene chloride as a solvent, Pd/MN200 successfully catalyzed hydrogenation a mean diameter of 70 nm). It was shown that, using supercritical CO or methylene of aromatics in the temperature range of 55–150 °C. Moreover, Pd/HPS catalysts2 exhib- chloride as a solvent, Pd/MN200 successfully catalyzed hydrogenation of aromatics in ited higher activity compared to traditional catalysts containing an equivalent amount of the temperature range of 55–150 ◦C. Moreover, Pd/HPS catalysts exhibited higher activity Pd [10]. compared to traditional catalysts containing an equivalent amount of Pd [10]. 2. Results First, the hydrogenation of BZBZ toto cyclohexanecyclohexane (CH)(CH) waswas studiedstudied (the(the simplifiedsimplified reac- re- actiontion scheme scheme is is shown shown in in Figure Figure1 a)1a) at at variation variation of of solvent solvent nature,nature, BZBZ concentration,concentration, and catalyst composition (polymer (polymer type, type, metal metal loading, loading, and and nature). nature). It It is is noteworthy noteworthy that that different side products can be found during BZ BZ hydrogenation hydrogenation [5,7], [5,7], but but their their formation formation is associated with with the the acid–base acid–base properties properties of of the the supports supports used. used. In In the the case case of of polymeric polymeric supports (in(in particular,particular, HPS), HPS), 100% 100% selectivity selectivity with with respect respect to CH to wasCH observedwas observed irrespective irre- spectiveof the metal of the nature metal and nature reaction and reaction conditions conditions (see Table (see1). Table 1). (a) (b) Figure 1. SimplifiedSimplified schemes schemes of of selective selective hydrogenation hydrogenation of of BZ BZ to to CH CH ( (aa)) and and TOL TOL to to MCH MCH ( (bb).). Most ofof BZBZ hydrogenations hydrogenations were were carried carried out out in in hexane hexane medium medium at 230at 230◦C, which°C, which was wasfound
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