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

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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 deposition. 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 studied 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 found as optimal as optimal temperature temperature during during the the reaction reaction study study with with 1% 1% Pt/HPS Pt/HPS (see (see Figure Figure2 2and and Table Table1, #1).1, #1). As As can can be seenbe seen in Figurein Figure2, the 2, initialthe initial rate rate of BZ of transformation BZ transformation gradually grad- uallyincreases increases with with the temperature the temperature increase increase from from 210 ◦210C up °C toup 230 to 230◦C. °C At. At 240 240◦C, °C, the the rate rate of ofBZ BZ hydrogenation hydrogenation attains attains the the maximum, maximum, and an thed the following following increase increase of of temperature temperature up up to to260 260◦C °C results results in ain sharp a sharp decrease decrease of the of reactionthe reacti rateon (noterate (note that the that critical the critical point ofpoint hexane of is 234.5 ◦C at 3.02 MPa). Recently, we have found that hydrogenation of NL to TL in hexane can effectively proceed at 250 ◦C and at 6 MPa of overall pressure [11]. The strong decrease of hydrogenation rate while shifting to supercritical hexane, in the case of BZ in contrast to NL, can be due to the difference in adsorption of mono- and dicyclic arenes. In general, if the metal NPs are large enough, condensed arenes should adsorb stronger. Nevertheless, in the range of 210–230 ◦C, the apparent activation energy of Molecules 2021, 26, x FOR PEER REVIEW 3 of 15

hexane is 234.5 °C at 3.02 MPa). Recently, we have found that hydrogenation of NL to TL in hexane can effectively proceed at 250 °C and at 6 MPa of overall pressure [11].

Table 1. Data of catalytic testing of HPS-based catalysts in hydrogenation of nonpolar aromatics (CS,0 = 0.28 mol/L, catalyst loading 100 mg, temperature 230 °C, overall pressure 5 MPa, reaction duration 60 min).

N Catalyst Substrate Product Solvent X (S), % R0, molsub/ (molMe × s) Molecules 2021, 26, 4687 3 of 15 1 1% Pt/HPS hexane 96 (100) 1.37 2 1% Pt/HPS (1) hexane 98 (100) 0.77 3 1% Pt/HPS 2nd use (1) hexane 84 (100) 0.43 BZ hydrogenation was calculated as Ea,app = 81 ± 5 kJ/mol (Figure2), which is in agreement 4 1% Pt/HPS-NR2 dodecane 38 (100) 0.47 with the data reported elsewhere [12,13]. It is noteworthy that for calculation of E , the 5 i-PrOH 90 (100) a,app 0.90 initial reaction rate R0 was obtained as a tangent of the slope on the kinetic curve related 6 2% Pt/HPS-NR2 (BZ) (CH) dodecane 92 (100) 0.89 MoleculesMolecules 2021 2021, 26, ,26 x ,FOR x FOR PEER PEER REVIEW REVIEWto the metal concentration (see Section 4.3). We can suppose that the coverage of3 of3 metal of15 15 Molecules 7 Molecules 2021 2021,, 26,, , ,26 xx ,FOR,FOR xx FORFOR PEERPEER PEERPEER REVIEWREVIEW REVIEWREVIEW hexane 100 (100) 3 1.66of3 of15 15 MoleculesMolecules 2021 2021, 26, ,26 x ,FOR x FOR PEER PEER REVIEW REVIEW 3 of3 of15 15 surface by hydrogen is low, which is typical for small conversions where concentration 8 2% Ru/HPS-NR2 of substrate is still high [14]. Thus, with highhexane selectivity to89 target (100) product and without0.40 9 2% Pd/HPS-NR2 hexane 100 (100) 0.82 hexaneanyhexane inﬂuence is is234.5 234.5 °C of °C at diffusion, at3.02 3.02 MPa). MPa). the Recently,irreversible Recently, we we have addition have found found of that hydrogen that hydrogenation hydrogenation atoms to of the ofNLadsorbed NL to toTL TL hexanehexane is 234.5is 234.5 °C °C at at3.02 3.02 MPa). MPa). Recently, Recently, we we have have found found that that hydrogenation hydrogenation of ofNL NL to toTL TL inhexane substratehexaneinhexane hexane is is234.5can can 234.5can effectively be°C effectively °C consideredat at 3.02 3.02 proceedMPa). proceedMPa). as Recently, a atRecently, rate-determining at250 250 °C we°C and we andhave haveat at6 found MPa step.6 found MPa of that ofoverallthat overallhydrogenation hydrogenation pressure pressure [11]. of [11]. of NL NL to to TL TL in inhexane hexane can can effectively effectively proceed proceed at at250 250 °C °C and and at at6 MPa6 MPa of ofoverall overall pressure pressure [11]. [11]. 10 1% Pt/HPS-NR2 (2) inin hexane hexane can can effectively effectively proceed proceed at at 250 250 °C °C and andhexane at at 6 MPa6 [11]MPa of of overall overall 94 (88) pressure pressure [11]. [11]. 0.15 Table 1. Data of catalytic testing of HPS-based catalysts in hydrogenation of nonpolar aromatics (C = 0.28 mol/L, catalyst TableTable 1. Data1. Data of ofcatalytic catalytic testing testing of ofHPS-based HPS-based cataly catalystssts in inhydrogenation hydrogenation of ofnonpolar nonpolar aromatics aromatics (SC,0 S(,0C S=,0 0.28 = 0.28 mol/L, mol/L, cata- cata- Table 1. Data of catalytic testing ◦of HPS-based catalysts in (TL)hydrogenation of nonpolar aromatics S(,0CS,0 = 0.28 mol/L, cata- TableTable 1. Data1. Data of ofcatalytic catalytic testing testing of ofHPS-based(NL) HPS-based cataly catalystssts in inhydrogenation hydrogenation of ofnonpolar nonpolar aromatics aromatics (C S(,0C =S,0 0.28 = 0.28 mol/L, mol/L, cata- cata- lystTableloadingTablelyst loading loading1. 1.Data 100 Data 100 mg, of100 mg, ofcatalytic temperaturemg,catalytic temperature temperature testing testing 230 of230 of230HPS-basedC, °C,HPS-based overall °C, overall overall pressure cataly pressure cataly pressurests 5sts in MPa,5 inMPa,hydrogenation 5 hydrogenationMPa, reaction reacti reaction durationon duration of duration ofnonpolar nonpolar 60 60 min). 60min). aromatics min). aromatics (C (SC,0 S=,0 0.28= 0.28 mol/L, mol/L, cata- cata- lystlyst loading loading 100 100 mg, mg, temperature temperature 230 230 °C, °C, overall overall pressure pressure 5 MPa, 5 MPa, reacti reactionon duration duration 60 60min). min). lystlystlyst loadingloading loading 100100 100 mg,mg, mg, temperaturetemperature temperature 230230 230 °C,°C, °C, overalloverall overall pressurepressure pressure 55 MPa, MPa,5 MPa, reactireacti reactiononon durationduration duration 6060 60 min).min). min). N NN CatalystCatalyst Catalyst Substrate Substrate PrProductoduct Product Solvent Solvent Solvent X (S), X (S), % % RR0,R 0mol0,, molmolsubsub/sub (mol//(mol (molMeMe Me× s) × s)s) N Catalyst Substrate Product Solvent X (S), % 0R0, molsubsub/ (molMe Me × s) 11N N 1% CatalystPt/HPS-NRCatalyst 2 Substrate Substrate Product Product Solvent Solventdodecane X (S), X (S), % %82 (88)R0,R mol0, molsub/sub (mol/ (molMe Me× 0.85s) × s) N1 N1 1%Catalyst1% CatalystPt/HPS Pt/HPS Substrate Substrate Pr Productoduct Solventhexane Solventhexane X96 X(S),96(100) (S), (100) % % R0R, mol0, molsub 1.37sub/ (mol 1.37/ (mol MeMe × s)× s) 1 11 1%1% Pt/HPS 1% Pt/HPS Pt/HPS hexanehexanehexane 96 96(100) (100) 1.37 1.37 1 1 1%1% Pt/HPS Pt/HPS (1) (1) (1) (ANC) (9,10-DANC) hexanehexane 96 96(100) (100) 1.37 1.37 21 12 2 1%1%1% 1%1%Pt/HPS Pt/HPS Pt/HPS Pt/HPS Pt/HPS (1) (1) hexanehexanehexane 989696 98(100) (100) 0.77 1.37 1.370.77 2 2 1%1% Pt/HPS Pt/HPS (1) (1) hexanehexane 98 98(100) (100) 0.770.77 2 2 1%1% Pt/HPS Pt/HPS (1) (1) (1) (1) (1) hexanehexane 98 98(100) (100) 0.770.77 32 23 3 1%1% 1%Pt/HPS1% Pt/HPS1% Pt/HPSPt/HPS Pt/HPS 2nd 2nd 2nduse use (1) use (1) hexanehexanehexanehexane 849898 84 (100)(100) (100) (100) 0.430.770.77 0.43 3 3 1%1% Pt/HPS Pt/HPS 2nd 2nd use use (1) (1) hexanehexane 84 84(100) (100) 0.430.43 3 3 1%1% Pt/HPS Pt/HPS2nd 2nd use use (1) (1) hexanehexane 84 84(100) (100) 0.430.43 43 34 41%1%1% Pt/HPS1% Pt/HPSPt/HPS-NR 1% Pt/HPS-NR Pt/HPS-NR2nd2nd use 2use 2 2 dodecanedodecanehexanedodecanehexane 388484 38 (100)(100) (100) (100) 0.470.430.430.47 12 4 1%1% Pt/HPS-NR Pt/HPS-NR2 2 2 dodecanedodecane 38 (100)80 (100) 0.47 1.41 4 4 1%1% Pt/HPS-NR Pt/HPS-NR2 2 dodecanedodecane 38 38(100) (100) 0.470.47 54 45 5 1%1% Pt/HPS-NR Pt/HPS-NR2 2 dodecaneii-PrOH-PrOHdodecanei-PrOH 903838 90 (100)(100) (100) (100) 0.900.470.47 0.90 5 5 (TOL) (MCH) i-PrOHi-PrOH 90 90(100) (100) 0.90 0.90 65 56 62%2% Pt/HPS-NR2% Pt/HPS-NR Pt/HPS-NR2 2 (BZ)(BZ) (CH)(CH)(CH) dodecane dodecanei-PrOHdodecanei-PrOH 92909092 (100) (100) 0.89 0.90 0.900.89 6 6 2%2% Pt/HPS-NR Pt/HPS-NR2 2 2 (BZ)(BZ) (1) (CH) (2) dodecanedodecane 92 92(100) (100) 0.89 0.89 6 6 2%2% Pt/HPS-NR Pt/HPS-NR2 2 (BZ)(BZ) CBZ,0 = 0.14(CH) mol/L.(CH) Temperaturedodecanedodecane 240 °C.92 92 (100) (100) 0.89 0.89 76 67 72%2% Pt/HPS-NR Pt/HPS-NR2 2 (BZ)(BZ) (CH)(CH) dodecanehexane hexanedodecanehexane 10092 10092 (100)(100) (100) (100) 1.660.89 0.891.66 7 7 hexanehexane 100100 (100) (100) 1.66 1.66 87 78 2%2% Ru/HPS-NR Ru/HPS-NR2 2 hexanehexane 10089100 89(100) (100) (100)(100) 0.40 1.66 1.660.40 88 2% 2% Ru/HPS-NR Ru/HPS-NR2 2 2 hexanehexane 89 (100) 0.40 8 8 2%2% Ru/HPS-NR Ru/HPS-NR2 2 hexanehexane 89 89(100) (100) 0.400.40 98 89 2%2%2% Pd/HPS-NRRu/HPS-NR Ru/HPS-NRPd/HPS-NR22 2 The strong decrease of hydrogenationhexanehexanehexanehexane rate10089 while10089 (100)(100) (100) (100) shifting to 0.82supercritical0.400.400.82 hexane, in 99 2% 2% Pd/HPS-NR Pd/HPS-NR2 2 2 hexanehexane 100 (100) 0.82 9 9 2%2% Pd/HPS-NR Pd/HPS-NR2 2 hexanehexane 100100 (100) (100) 0.820.82 9 9 2%2% Pd/HPS-NR Pd/HPS-NR2 2 the case of BZ in contrast to NL, canhexane behexane du e to 100the100 (100)difference (100) in adsorption0.820.82 of mono- and

(2) (2) 10 10 1%1% Pt/HPS-NR Pt/HPS-NR2 2 (2) (2) dicyclic arenes. In general, if the metalhexanehexane NPs[11] [11] are 94 large 94(88) (88) enough, condensed 0.15 0.15 arenes should 10 1% Pt/HPS-NR2 (2)(2)2 hexane [11] 94 (88) 0.15 10 10 1% Pt/HPS-NR1% Pt/HPS-NR2 2 (2)2 hexanehexane [11] [11] 94 94(88) (88) 0.15 0.15 10 1% Pt/HPS-NR2 (2)2 (2) hexane [11] 94 (88) 0.15 1010 1%1% Pt/HPS-NR Pt/HPS-NR adsorb(NL)(NL) stronger. Nevertheless,(TL)(TL) in thehexanehexane range [11] [11] of 210–230 94 94(88) (88) °C, the apparent 0.15 0.15 activation energy (NL)(NL) (TL)(TL)(TL) of (NL)BZ(NL)(NL) hydrogenation (TL) was(TL) calculated as Ea,app = 81 ± 5 kJ/mol (Figure 2), which is in

11 11 1%1% Pt/HPS-NR Pt/HPS-NR2 2 agreement with the data reported elsewheredodecanedodecane [12,8213]. 82(88) (88) It is noteworthy 0.85 0.85 that for calculation 11 1% Pt/HPS-NR2 2 dodecane 82 (88) 0.85 11 111% Pt/HPS-NR 1% Pt/HPS-NR2 2 dodecanedodecane 82 82(88) (88) 0.85 0.85 11 1% Pt/HPS-NR2 2 2 of Ea,app, the initial reaction rate R0 wasdodecane obtained as82 (88)a tangent of the 0.85 slope on the kinetic 1111 1%1% Pt/HPS-NR Pt/HPS-NR (ANC)(ANC) (9,10-DANC)(9,10-DANC) dodecanedodecane 8282 (88) (88) 0.85 0.85 (ANC)(ANC) (9,10-DANC)(9,10-DANC) curve(ANC)(ANC)(ANC) related to the(9,10-DANC)(9,10-DANC)(9,10-DANC) metal concentration (see Section 4.3). We can suppose that the coverage of metal surface by hydrogen is low, which is typical for small conversions where 12 12 1%1% Pt/HPS-NR Pt/HPS-NR2 2 dodecanedodecane 80 80(100) (100) 1.41 1.41 12 12 1%1% Pt/HPS-NR Pt/HPS-NR2 2 dodecanedodecane 80 80(100) (100) 1.41 1.41 12 12 1%1% Pt/HPS-NR Pt/HPS-NR2 2 dodecanedodecane 80 80(100) (100) 1.41 1.41 1212 12 1%1% Pt/HPS-NR 1% Pt/HPS-NR Pt/HPS-NR2 2 2 concentration(TOL)(TOL) of substrate(MCH)(MCH) is still highdodecanedodecane [14]. Thus, 8080 (100) with (100) high selectivity 1.41 1.41 to target product (TOL)(TOL) (MCH)(MCH) and(TOL) without(TOL)(TOL)(1) (1) any influence(MCH)(MCH)(2) (2) of diffusion, the irreversible addition of hydrogen atoms to the (TOL)(TOL)(1) C(1) BZ C,0BZ =,0 0.14 = 0.14 mol/L. mol/L.(MCH)(MCH) (2) Temperature(2) Temperature 240 240 °C. °C. (1) C(1)BZ C,0BZ =,0 0.14 = 0.14 mol/L. mol/L. (2) Temperature(2) Temperature 240 240 °C. °C. (1)C BZC,0BZ =,0 0.14 = 0.14 mol/L. mol/L. (2) Temperature Temperature 240 240 °C. °C. adsorbedC(1) (1)substrateBZ C,0BZ =,0 0.14= 0.14 mol/L. canmol/L. be (2)Temperature (2)considered Temperature 240 as 240 °C.◦a °C.rate-determining step. CBZ,0 = 0.14 mol/L. Temperature 240 C. TheThe strong strong decrease decrease of ofhydrogenation hydrogenation rate rate while while shifting shifting to tosupercritical supercritical hexane, hexane, in in TheThe strong strong decrease decrease of ofhydrogenation hydrogenation rate rate while while shifting shifting to tosupercritical supercritical hexane, hexane, in in thethe caseThe caseThe of strong ofBZstrong BZ in decrease incontrast decrease contrast ofto of toNL,hydrogenation hydrogenationNL, can can be be du due ratetoe rate tothe while the whiledifference difference shifting shifting in to inadsorption to supercriticaladsorption supercritical of ofmono- hexane, mono-hexane, and inand in thethe case case of ofBZ BZ in incontrast contrast to toNL, NL, can can be be du due toe tothe the difference difference in inadsorption adsorption of ofmono- mono- and and dicyclicthethedicyclic case case arenes.of arenes.of BZ BZ in Inin contrast In general,contrast general, to ifto NL, the ifNL, the canmetal can metal be be NPsdu duNPse toeare to theare largethe differencelarge difference enough, enough, in incondensed adsorption condensedadsorption arenes of arenesof mono- mono- should should and and dicyclicdicyclic arenes. arenes. In Ingeneral, general, if theif the metal metal NPs NPs are are large large enough, enough, condensed condensed arenes arenes should should adsorbdicyclicdicyclicadsorb stronger. arenes. stronger. arenes. In Nevertheless, In general,Nevertheless, general, if ifthe inthe inthemetal metalthe range rangeNPs NPs of are of 210–230are 210–230large large enough,°C, enough, °C, the the apparent condensed apparent condensed activation activation arenes arenes energyshould shouldenergy adsorbadsorb stronger. stronger. Nevertheless, Nevertheless, in inthe the range range of of210–230 210–230 °C, °C, the the apparent apparent activation activation energy energy ofadsorb adsorbofBZ BZ hydrogenationstronger. hydrogenationstronger. Nevertheless, Nevertheless, was was calculated calculated in in the the range asrange asE a,appofE of a,app210–230 = 210–230 =81 81 ± °C,5± °C,5kJ/mol the kJ/molthe apparent apparent (Figure (Figure activation 2),activation 2), which which energy energyis isin in a,appa,app ± of ofBZ BZ hydrogenation hydrogenation was was calculated calculated as asE a,appEa,app = 81= 81 ± 5± kJ/mol5 kJ/mol (Figure (Figure 2), 2), which which is isin in agreementofof agreementBZ BZ hydrogenation hydrogenation with with the the data datawas wasreported reportedcalculated calculated elsewhere elsewhere as as E a,appE [12,a,app [12,= 13]. =81 13].81 It± ±isIt5 5isnoteworthykJ/mol kJ/molnoteworthy (Figure (Figure that that 2), for2), forwhich calculationwhich calculation is isin in agreementagreement with with the the data data reported reported elsewhere elsewhere [12, [12,13].13]. It isIt isnoteworthy noteworthy that that for for calculation calculation ofagreementagreement ofEa,app Ea,app, the, the with initial with initial the thereaction datareaction data reported reportedrate rate R 0R elsewherewas0 elsewherewas obtained obtained [12, [12, 13].as 13]. asa It tangenta Itis tangent isnoteworthy noteworthy of ofthe the slope that slope that foron foron calculationthe calculationthe kinetic kinetic a,appa,app 0 0 of ofEa,app Ea,app, the, the initial initial reaction reaction rate rate R 0 Rwas0 was obtained obtained as asa tangenta tangent of ofthe the slope slope on on the the kinetic kinetic curveofof curveE a,appE a,apprelated, therelated, the initial toinitial tothe thereaction metalreaction metal concentration rate concentrationrate R 0R was0 was obtained (seeobtained (see Section Section as as a 4.3).atangent tangent4.3). We We ofcan of canthe supposethe slopesuppose slope on that on thatthe thethe kineticthe kineticcov- cov- curvecurve related related to tothe the metal metal concentration concentration (see (see Section Section 4.3). 4.3). We We can can suppose suppose that that the the cov- cov- eragecurvecurveerage ofrelated ofrelatedmetal metal to surface to thesurface the metal metalby by hydrogen concentration hydrogenconcentration is islow, low,(see (seewhich whichSection Section is istypical 4.3). typical 4.3). We forWe forcan small can small suppose suppose conversions conversions that that the wherethe cov-where cov- erageerage of ofmetal metal surface surface by by hydrogen hydrogen is low,is low, which which is typicalis typical for for small small conversions conversions where where concentrationerageerageconcentration of of metal metal of surface ofsurfacesubstrate substrate by by hydrogenis hydrogen isstill still high high is is[14].low, low,[14]. whichThus, whichThus, withis withistypical typicalhigh high forselectivity forselectivity small small conversions toconversions totarget target product whereproduct where concentrationconcentration of ofsubstrate substrate is isstill still high high [14]. [14]. Thus, Thus, with with high high selectivity selectivity to totarget target product product andconcentrationconcentrationand without without any ofany of influencesubstrate substrateinfluence ofis isofdiffusion,still stilldiffusion, high high [14].the [14]. the irre Thus, irre Thus,versibleversible with with addition high additionhigh selectivity selectivity of ofhydrogen hydrogen to to target targetatoms atoms product productto tothe the andand without without any any influence influence of ofdiffusion, diffusion, the the irre irreversibleversible addition addition of ofhydrogen hydrogen atoms atoms to tothe the adsorbedandandadsorbed without without substrate substrate any any influence influencecan can be be consideredof consideredof diffusion, diffusion, as the asa the rate-determining airre rate-determiningirreversibleversible addition addition step. step. of of hydrogen hydrogen atoms atoms to to the the adsorbedadsorbed substrate substrate can can be be considered considered as asa rate-determininga rate-determining step. step. adsorbedadsorbedadsorbed substratesubstrate substrate cancan can bebe be consideredconsidered considered asas as aa rate-determiningrate-determininga rate-determining step.step. step.

Figure 2. Effect of temperature on hydrogenation of BZ to CH over 1% Pt/HPS (5 MPa, catalyst loading 100 mg); inset shows the Arrhenius plot for initial reaction rate, R . 0

Molecules 2021, 26, x FOR PEER REVIEW 4 of 15

Molecules 2021, 26, 4687 4 of 15 Figure 2. Effect of temperature on hydrogenation of BZ to CH over 1% Pt/HPS (5 MPa, catalyst loading 100 mg); inset shows the Arrhenius plot for initial reaction rate, R0.

For the catalyst 1% Pt/HPS, the the effect effect of of reuse reuse was was also also studied studied (Table (Table1 1,, #2,3).#2,3). ItIt waswas 0 foundfound that that nearly double a a decrease of the initial reaction rate ((R0)) takes place at the secondsecond reactionreaction run.run. The The polymeric polymeric matrix matrix of HPSof HPS remained remained stable stable during during the experiments. the experiments.Low-temperature Low-temperature nitrogen nitrogen physisorption physisorptio revealedn revealed that the that speciﬁc the specific surface surface area (SSA) area (SSA)determined determined according according to the BET to the model BET was model nearly was the nearly same forthe bothsame the for initial both (934the minitial2/g) (934and them2/g) used and (955 the m 2used/g) catalyst.(955 m2/g) Using catalyst. the XPS Using method, the itXPS was method, found that it was there found is a slight that therechange is ina slight the ratio change between in the different ratio between forms di offferent Pt on theforms catalyst of Pt surface:on the catalyst the increase surface: of 0 0 thethe increase content Ptof the(binding content energy Pt (binding (BE) of energy Pt 4f7/2 (BE)is 71.5 of Pt eV) 4f was7/2 is observed71.5 eV) was (from observed 77 at.% (fromup to 8777 at.% at.%) up with to 87 concomitant at.%) with concomitant decrease of the decrease content of ofthe PtO content (BE of of Pt PtO 4f7/2 (BEis of 72.9 Pt 4f eV)7/2 isfrom 72.9 23 eV) at.% from to 1323 at.%;at.% however,to 13 at.%; these however, changes these cannot changes explain cannot the explain signiﬁcant the decreasesignificant in decreasecatalytic activityin catalytic for theactivity second for use. the Thesecond reason use. can The be reason due to can the formationbe due to the of carbonaceous formation of carbonaceousdeposits on the deposits surface on of the Pt NPs,surface which of Pt often NPs, causeswhich theoften catalyst causes deactivation the catalyst duringdeacti- vationthe hydrogenation during the hydrogenation of arenes [13, 15of]. arenes However, [13,15]. Pt However, content (determined Pt content (determined by the XPS) onby thethe XPS) catalyst on surfacethe catalyst even surface increases even after increa theses catalytic after the experiment catalytic experiment from about from 0.3 at.% about up 0.3to 0.5at.% at.%. up to Thus, 0.5 at.%. we canThus, suppose we can that suppose the observed that the observed drop in catalytic drop in catalytic activity isactivity likely isdue likely to the due changes to the changes in morphology in morphology of thecatalytically of the catalytically active phase,active phase, i.e., agglomeration i.e., agglom- erationof NPs. of It NPs. is known It is known that the that sizes the ofsizes Pt of NPs Pt haveNPs have a crucial a crucial effect effect on the on kineticsthe kinetics of BZ of BZhydrogenation hydrogenation [16 ].[16]. The effect of solventsolvent naturenature was was studied studied using using 2% 2% Pt/HPS-NR Pt/HPS-NR2 2as as catalyst catalyst (see (see Figure Figure3 3and and Table Table1, #5–7).1, #5–7). As As can can be be seen seen from from Figure Figu3,re the 3, usethe use of hexane of hexane as a as solvent a solvent provides provides the ◦ thehighest highest rate rate of BZ oftransformation, BZ transformation, although although at the at chosen the chosen temperature temperature (230 C),(230 the °C), vapor the vaporpressure pressure of hexane of hexane is rather is high—about rather high—about 2.7 MPa. 2.7 In theMPa. case In ofthei-PrOH case of and i-PrOH dodecane, and do- the ◦ decane,reaction the rate reaction was noticeably rate was lower,noticeably compared lower, tocompared hexane. to It ishexane. noteworthy It is noteworthy that at 230 thatC, ati-PrOH 230 °C, has i-PrOH vapor has pressure vapor higher pressure than higher 4 MPa, than which 4 MPa, drastically which drastically decreases hydrogendecreases hydrogenpartial pressure partial (overall pressure pressure (overall in pressure the reactor in the was reactor 5 MPa). was Nevertheless, 5 MPa). Nevertheless, the rate of the BZ ratehydrogenation of BZ hydrogenation in i-PrOH in medium i-PrOH wasmedium comparable was comparable with those with in dodecanethose in dodecane as a solvent, as a solvent,possibly possibly due to the due ability to the of abilityi-PrOH of toi-PrOH serve to as serve an effective as an effective hydrogen hydrogen donor [17 donor]. [17].

◦ Figure 3. 3. SolventSolvent effect effect on BZ on hydrogenation BZ hydrogenation to CH to over CH 2% over Pt/HPS-NR 2% Pt/HPS-NR2 (230 °C2, (2305 MPa,C, CBZ 5,0 MPa,= 0.28CBZ ,0mol/L,= 0.28 catalyst mol/L, loading catalyst 100 loading mg). 100 mg).

◦ At the chosen temperature (230 °C)C) in he hexanexane medium, the effect of metal nature was studied (Table 1 1,, #7–9).#7–9). ItIt waswas foundfound thatthat PtPt isis thethe mostmost effectiveeffective metalmetal asas itit providesprovides a 3–6-fold higher initial reaction rate compared to Pd and Ru (note that RuO is an active a 3–6-fold higher initial reaction rate compared to Pd and Ru (note that RuO22 is an active phase of 2% Ru/HPS-NR ). phase of 2% Ru/HPS-NR22). InIn contrast to BZ, TOL was three-foldthree-fold fasterfaster hydrogenatedhydrogenated exclusively with MCH (Figure1b) (Table1, #4 vs. 12) using 1% Pt/HPS-NR 2 in dodecane. This result is un- (Figure 1b) (Table 1, #4 vs. 12) using 1% Pt/HPS-NR2 in dodecane. This result is unusual, usual, since, according to other reports, the rates of BZ and TOL hydrogenation are often since, according to other reports, the rates of BZ and TOL hydrogenation are often com- comparable [18,19]. parable [18,19]. Hydrogenation of naphthalene (NL) and anthracene (ANC) was carried out over 1% Pt/HPS-NR2. NL was found to be selectively hydrogenated to target TL (Figure4), while in the case of ANC, 9,10-dihydroanthracene (9,10-DANC) was the main reaction product (Figure5). Pt-containing catalysts were shown to be stable in four consecutive runs of NL

Molecules 2021, 26, x FOR PEER REVIEW 5 of 15

Molecules 2021, 26, x FOR PEER REVIEW 5 of 15 Molecules 2021, 26, x FOR PEER REVIEW 5 of 15 Hydrogenation of naphthalene (NL) and anthracene (ANC) was carried out over 1% Pt/HPS-NR2. NL was found to be selectively hydrogenated to target TL (Figure 4), while in the case of ANC, 9,10-dihydroanthracene (9,10-DANC) was the main reaction Hydrogenation of naphthalene (NL) and anthracene (ANC) was carried out over Molecules 2021, 26, 4687 productHydrogenation (Figure 5). Pt-containing of naphthalene catalysts (NL) wereand anthracene shown to be(ANC) stable was in fourcarried5 consecutive of 15 out over 1% Pt/HPS-NR2. NL was found to be selectively hydrogenated to target TL (Figure 4), runs1% Pt/HPS-NRof NL and ANC2. NL hydrogenationwas found to bewithout selectively any noticeable hydrogenated loss ofto activitytarget TLand (Figure selectiv- 4), while in the case of ANC, 9,10-dihydroanthracene (9,10-DANC) was the main reaction itywhile under in thethe chosencase of reactionANC, 9,10-dihydroanthracene conditions. (9,10-DANC) was the main reaction product (Figure 5). Pt-containing catalysts were shown to be stable in four consecutive product (Figure 5). Pt-containing catalysts were shown to be stable in four consecutive runsand ANC of NL hydrogenation and ANC hydrogenation without any noticeable without loss any of noticeable activity and loss selectivity of activity under and the selectiv- chosenruns of reaction NL and conditions. ANC hydrogenation without any noticeable loss of activity and selectivity under the chosen reaction conditions. ity under the chosen reaction conditions.

Figure 4. Simplified scheme of selective hydrogenation of NL to TL.

Figure 4. Simplified scheme of selective hydrogenation of NL to TL. FigureFigure 4. 4.Simpliﬁed Simplified scheme scheme of selective of selective hydrogenation hydrogenation of NL toof TL.NL to TL.

Figure 5. Simplified scheme of selective hydrogenation of ANC to 9,10-DANC.

It was also found that the initial hydrogenation rate (R0) increases in the order: NL < Figure 5. Simplified scheme of selective hydrogenation of ANC to 9,10-DANC. BZFigureFigure < ANC 5. 5.Simplified Simplified (Table scheme 1,scheme #4,10,11). of selective of selective In hydrogenation contrast hydrogenation to ofthe ANC data of to ANC 9,10-DANC.reported to 9,10-DANC. by Rautanen et al. [20], who claimed that in condensed aromatics the first ring of diaromatic compounds (i.e., ItIt waswas alsoalso foundfound thatthat thethe initialinitial hydrogenationhydrogenation rate rate (R (0R)0 increases) increases in in the the order: order: NL < NL) isIt morewas also reactive found than that the the secondinitial hydrogenation one, in the case rate of (Pt/HPSR0) increases catalysts, in the NL order: was NLless < BZNL << BZANC < ANC (Table(Table 1, 1#4,10,11)., #4,10,11). In In contrastcontrast to to the the data data reported reported by Rautanen by Rautanen et al. [ 20 et], al. [20], reactiveBZ < ANC compared (Table to1, BZ.#4,10,11). In contrast to the data reported by Rautanen et al. [20], who claimedclaimed that that in condensedin condensed aromatics aromatics the first the ring first of diaromaticring of diaromatic compounds compounds (i.e., NL) (i.e., whoAt claimed the same that intime, condensed in the aromaticsANC hydrogenation, the first ring ofthe diaromatic main side compounds product was(i.e., NL)is more is reactivemore reactive than the than second the one, second in the one, case ofin Pt/HPSthe case catalysts, of Pt/HPS NL wascatalysts, less reactive NL was less 1,2,3,4-tetrahydro-ANCNL) is more reactive than (about the 9%second was accumulatedone, in the case during of Pt/HPS 60 min), catalysts, and no compoundsNL was less reactivecompared compared to BZ. to BZ. withreactive Athigher the compared samedegree time, to of BZ. insaturation the ANC were hydrogenation, found. This the result main indicates side product that wasthe rate of At the same time, in the ANC hydrogenation, the main side product was side-ring1,2,3,4-tetrahydro-ANCAt thehydrogenation same time, (about is inlow 9% the wasand ANC accumulatedcan be hydrogenation, due duringto the peculiarities 60 min),the andmain noof compoundssidearenes product adsorption was 1,2,3,4-tetrahydro-ANC (about 9% was accumulated during 60 min), and no compounds onwith1,2,3,4-tetrahydro-ANC Pt higher NPs. degreeHigher of reactivity saturation (about of were ANC9% found. was in comparaccumulated This resultison indicates with during BZ that is60 thelikely min), rate dueand of side-ring tono the compounds fact that with higher degree of saturation were found. This result indicates that the rate of Chydrogenationwith9 and higher C10 atoms degree is low of the and of central cansaturation be duering to inwere the ANC peculiarities foun haved. partiallyThis of arenes result higher adsorption indicates electron on that Ptdensity NPs. the duerate toof side-ring hydrogenation is low and can be due to the peculiarities of arenes adsorption theHigherside-ring influence reactivity hydrogenation of oftwo ANC side in rings,is comparison low makingand can with th be BZese due is carbon likely to the due atoms peculiarities to the more fact thatactive of Carenes9 forand hydrogena- C adsorption10 onatoms Pt ofNPs. the Higher central ring reactivity in ANC of have ANC partially in compar higherison electron with density BZ is duelikely to thedue influence to the fact that tion.on Pt NPs. Higher reactivity of ANC in comparison with BZ is likely due to the fact that Cof9 twoand side C10 rings,atoms making of the thesecentral carbon ring atomsin ANC more have active partially for hydrogenation. higher electron density due to C9 andHydrogenation C10 atoms of theof differentcentral ring substituted in ANC havearenes partially was also higher studied, electron taking density AN, due PL, to the influenceHydrogenation of two of side different rings, substituted making th arenesese carbon was alsoatoms studied, more takingactive AN,for hydrogena- PL, phenylacethylenethe influence of two (PHA), side andrings, propiophenone making these carbon(PP) as atoms models. more In activethe selective for hydrogena- hydro- phenylacethylenetion. (PHA), and propiophenone (PP) as models. In the selective hydro- genationgenationtion. ofof AN AN to to cyclohexylamine cyclohexylamine (CHA) (CHA) (see Figure (see 6Figure), HPS-supported 6), HPS-supported Pt NPs were Pt the NPs were Hydrogenation of different substituted arenes was also studied, taking AN, PL, themost most effectiveHydrogenation effective noble noble metal-containing of metal-containingdifferent catalystssubstituted ca independenttalysts arenes independent ofwas the polymeralso ofstudied, the type polymer and taking metal type AN, and PL, phenylacethylene (PHA), and propiophenone (PP) as models. In the selective hydro- metalloadingphenylacethylene loading (Figure (Figure7 and (PHA), Table 7 and2, #1–5).andTable propiophenone In2, spite#1–5). of In the spite fact (PP) of that the as numerous factmodels. that productsnumerousIn the selective can products be hydro- can genation of AN to cyclohexylamine (CHA) (see Figure 6), HPS-supported Pt NPs were beformedgenation formed during of during AN the to AN the cyclohexylamine hydrogenation AN hydrogenation [5 ],(CHA) we observed[5], (see we Figure observed only two 6), side HPS-supportedonly products two side depicted products Pt NPs were de- the most effective noble metal-containing catalysts independent of the polymer type and pictedinthe Figure most in6 Figure. effective 6. noble metal-containing catalysts independent of the polymer type and metal loading (Figure 7 and Table 2, #1–5). In spite of the fact that numerous products can metal loading (Figure 7 and Table 2, #1–5). In spite of the fact that numerous products can be formed during the AN hydrogenation [5], we observed only two side products de- be formed during the AN hydrogenation [5], we observed only two side products depicted in Figure 6. picted in Figure 6.

FigureFigure 6.6. SimpliﬁedSimplified scheme scheme of selectiveof selective hydrogenation hydrogenation of AN of to AN CHA. to CHA.

Figure 6. Simplified scheme of selective hydrogenation of AN to CHA. Figure 6. Simplified scheme of selective hydrogenation of AN to CHA.

Molecules 2021, 26, x FOR PEER REVIEW 6 of 15

However, in spite of the high initial reaction rate, Pt-containing HPS catalysts deac- tivated, especially at high initial concentrations of AN, which is seen from the shape of kinetic curves (see Figure 8a). At the same time, the apparent activation energy was 53 ± 5 kJ/mol (Figure 8b), which is comparable with literature data [21]. Moreover, it was found that 1% Pt/HPS is rather stable at the reuse (Table 2, #1,2); although the initial reaction rate slightly decreases, conversion and selectivity achieved in 120 min of the reaction remains the same. Observed loss of activity during the same reaction run can be due to strong adsorption of AN and products on the metal surface, acting similar to poisons [22,23], but this effect seems to take place only in situ under the reaction conditions.

Table 2. Data of catalytic testing of HPS-based catalysts in hydrogenation of substituted aromatics.

R0, molsub/ N Catalyst Substrate Product Solvent T, °C P, MPa X (S), % (molMe × s) 1 1% Pt/HPS hexane 150 2 100 (55) 1 0.32 2 1% Pt/HPS 2nd use hexane 150 2 100 (56) 1 0.21

3 2% Pt/HPS-NR2 hexane 150 3 41 (51) 2 0.32

4 2% Ru/HPS-NR2 hexane 150 3 54 (87) 2 0.05 (AN) (CHA) 5 2% Pd/HPS-NR2 hexane 150 3 58 (60) 2 0.07 6 water 150 2 96 (40) 3 0.24 7 EtOH 150 2 41 (60) 3 0.07 2% Pd/HPS-NR2 8 BuOH 150 2 53 (64) 3 0.12 (PL) (CHN) 9 TOL 90 ambient 100 (88) 4 6.70 10 EtOH 65 ambient 100 (78) 4 1.25 1% Pd/HPS-NR2 11 i-PrOH 70 ambient 100 (69) 4 2.25 (PHA) (STY)

12 1% Pd/HPS-NR2 hexane 80 0.25 92 (98) 5 0.13

MoleculesMolecules 2021 2021, ,26 26, ,x x FOR FOR PEER PEER REVIEW REVIEW 66 ofof 1515 (PP) (PPL) 1 CAN,0 = 0.14 mol/L, catalyst loading 100 mg, values of conversion (X) and selectivity (S) are indicated for the reaction time 120 min. 2 CAN,0 = 0.41 mol/L, catalyst loading 100 mg, values of X and S are indicated for the reaction time 150 min. 3 CPL,0 = 0.21 mol/L, catalyst Molecules 2021, 26, 4687 6 of 15 loading 50 mg, 2 MPa is partial hydrogenHowever,However, pressure, inin spitespite values ofof thethe of highXhigh and initial initialS are indicated reactionreaction for rate,rate, the Pt-containing Pt-containingreaction time 90 HPSHPS min. catalystscatalysts 4 CPHA,0 = 0.48 deac-deac- mol/L, catalyst loading 30 mg, maximumtivated,tivated, values especiallyespecially of X and atat corresponding highhigh initialinitial concentrations concentrationsS are indicated. 5of ofC PP AN,AN,,0 = 0.09 whichwhich mol/L, isis seenvaluesseen fromfrom of X andthethe Sshapeshape indicated ofof for the reaction time 150 min. kinetickinetic curvescurves (see(see FigureFigure 8a).8a). AtAt thethe samesame time,time, thethe apparentapparent activationactivation energyenergy waswas 5353 ±± 55 kJ/molkJ/mol (Figure(Figure 8b),8b), whichwhich isis comparablecomparable withwith literatureliterature datadata [21].[21]. Moreover,Moreover, itit waswas foundfound Molecules 2021, 26, x FOR PEER REVIEWthat 1% Pt/HPS is rather stable at the reuse (Table 2, #1,2); although the initial reaction6 of 15 that 1% Pt/HPS is rather stable at the reuse (Table 2, #1,2); although the initial reaction Molecules 2021, 26, x FOR PEER REVIEWraterate slightlyslightly decreases,decreases, conversionconversion andand selectivityselectivity achievedachieved inin 1201206 minofmin 15 ofof thethe reactionreaction

Molecules 2021, 26, x FOR PEER REVIEWremains the same. Observed loss of activity during the same reaction run6 of can15 be due to remains the same. Observed loss of activity during the same reaction run can be due to Molecules 2021, 26, x FOR PEER REVIEW 6 of 15 strongstrongHowever, adsorptionadsorption in spite ofof ANAN of the andand high productsproducts initial onreactionon ththee metalmetal rate, surface,Pt-containingsurface, actingacting HPS similarsimilar catalysts toto poisonspoisons deac- tivated,[22,23],[22,23],However, butespeciallybut thisthis in spite effecteffect at of high seemstheseems high initial to toinitial taketake concentrations reaction placeplace rate, onlyonly Pt-containing inin of situsitu AN, underunder which HPS the thecatalysts is reactionreaction seen deac- from conditions.conditions. the shape of tivated, However,especially inat spitehigh initialof the concentrationshigh initial reaction of AN, rate, which Pt-containing is seen from HPS the catalystsshape of deac- Molecules 2021, 26, x FORkinetic PEER REVIEW curves (see Figure 8a). At the same time, the apparent activation6 of 15 energy was 53 ± 5 kinetictivated,However, curves especially (see in spite Figure at of high 8a).the high Atinitial the initial same concentrations reaction time, the rate, apparent of Pt-containing AN, activationwhich isHPS seenenergy catalysts from was the deac-53 shape± 5 of TableTable 2.2. DataData ofof catalyticcatalytic testingtesting ofof HPS-basedHPS-based catalystcatalystss inin hydrogenationhydrogenation ofof substitutedsubstituted aromatics.aromatics. kJ/moltivated,kJ/molkinetic (Figure especially curves 8b), 8b), (see at which high whichFigure isinitial comparable 8a). is concentrationscomparable At the withsame literature time, ofwith AN, the literature data whichapparent [21]. is Moreover,seen activation data from [21]. theit energy was Moreover,shape found was of 53 ± it5 was found thatkineticthatkJ/mol 1% 1% curves Pt/HPS (FigureHowever, (see is 8b),Figureisrather in ratherspite which 8a).stable of the Atisstable comparable highatthe the sameinitial atreuse thereactiontime, with(Table reuse the rate, literature apparent2, Pt-containing(Table#1,2); dataalthoughactivation 2, [21].HPS#1,2); catalyststheMoreover, energy althoughinitial deac- was reaction it 53 was the± 5 found initial reaction RR00,, molmolsubsub// NN CatalystCatalyst ratekJ/molrateSubstrateSubstrate that slightlyslightly tivated, (Figure1% Pt/HPS decreases, especially decreases,8b), which isProductProduct ratherat conversion high is comparableconversion stableinitial concentrations andatSolventSolvent the withselectivity andreuse literature of selectivity(TableT, T,AN, achieved °C°C whichdata 2, #1,2); [21].is P,in P,seenachieved 120MPa Moreover,MPaalthough from min the of shapein the itthe Xwas X120 initial (S),ofreaction(S), found min % %reaction of the reaction that 1%kinetic Pt/HPS curves is rather(see Figure stable 8a). atAt the samereuse time, (Table the apparent 2, #1,2); activation although energy the wasinitial 53 ±reaction 5 remainsremainsrate slightly thethe same. same. decreases, Observed Observed conversion loss of loss activity andof activity duringselectivity the during sameachieved reaction the in same 120 run min canreaction beof duethe runreactionto can(mol(mol beMeMe due ×× s)s) to remainsratestrong slightly kJ/moladsorption the decreases,(Figuresame. of 8b), ObservedAN whichconversion and is comparableproducts loss and ofselectivity onwith activityth literaturee metal achieved duringdatasurface, [21]. in Moreover, actingthe 120 samemin similar it wasof reactionthe found to reactionpoisons run can be due to remainsthat 1% the Pt/HPS same. is Observedrather stable loss at the of reuse activity (Table during 2, #1,2); the although same thereaction initial reaction run can be 1due to 11 1%1% Pt/HPSPt/HPS strongremains[22,23], adsorption but the this same. effect Observed ofseems AN to loss andtake of placeactivityproductshexanehexane only during in onsitu150150 the thunder esame metal the reaction reaction 2 2surface, run conditions. can 100acting 100 be (55)due(55) similarto 1 to0.320.32 poisons strongrate adsorptionslightly decreases, of AN conversion and products and selectivity on th achievede metal insurface, 120 min acting of the reactionsimilar to poisons [22,23],strong adsorptionbut this effect of AN seems and products to take on place the metal only surface, in situ acting under similar the reactionto poisons1 1conditions. 22 1%1% Pt/HPSPt/HPS2nd2nd useuse Figure[22,23],remains 7.butCHA the this same. effect accumulation Observed seems lossto take usingofhexane hexaneactivity place different during only 150 in 150the noble situ same under metal reaction NPsthe2 2 run reaction supportedcan be due100 100conditions. to (56) on(56) HPS-NR (1500.210.21 ◦ C, 3 MPa, Table 2. Data of [22,23],catalyticstrong but testing this adsorption of effect HPS-based seems of AN catalyst to and take productss placein hydrogenation onlyon th ein metal situ of undersurface, substituted the acting reaction aromatics. similar conditions. to poisons 2 2 C = 0.41 mol/L, catalyst loading 100 mg). 22 3 3 2%2% Pt/HPS-NRTablePt/HPS-NR 2.Table Data 2.2 ofData catalytic of catalyticAN[22,23],,0 testing testing but ofthis of HPS-based effectHPS-based seems tocatalyst catalyst take hexaneplacehexanes ins onlyhydrogenationin hydrogenation in situ150150 under of the substituted reaction of 3substituted3 conditions. aromatics. 41 41aromatics. (51)(51) 0.320.32 TableTable 2. Data 2. Data of ofcatalytic catalytic testing of ofHPS-based HPS-based catalyst catalysts in hydrogenations in hydrogenation of substituted of aromatics. substituted R0, aromatics.molsub/ N Catalyst Substrate Product Solvent T, °C P, MPa X (S), % 2 4 2% Ru/HPS-NR2Table2 2. Data of catalytic testing of HPS-based catalysts inhexane hydrogenation of150 substituted aromatics.3 54 (87) 2 0.05 4 2% Ru/HPS-NRTable 2. Data of catalytic testing of HPS-based catalystshexane in hydrogenation150 3 of substituted(mol54Me (87)R × aromatics.0, s)mol sub/ 0.05 N Catalyst (AN)Substrate Product(CHA) Solvent T, °C P, MPa X (S), %R0 , molsub/ R0, molsub/ N1 1%Catalyst Pt/HPS Substrate(AN) Product(CHA) Solventhexane T,150 °C P, MPa 2 100 X (S), (55) % R1 0, molsub0.32/ 22 N55 2%2% Pd/HPS-NRCatalystPd/HPS-NRN 2Catalyst2 Substrate Substrate ProductProduct SolventSolventhexanehexane T, °C T, P,150150 MPa°C X P, (S), MPa3 3% X5858 (S), (mol (60)(60) % Me × s) 0.070.07 (molMe × s) R , mol / ◦ (mol1 Me × s) (mol0Me × s)sub N2 1% Catalyst Pt/HPS 2nd use Substrate Product hexane Solvent 150 2T, C 100 P, (56) MPa 1 0.21 X (S), % (mol × s) 1 1% Pt/HPS hexane 150 2 100 (55) 0.3233 66 1 1%1 Pt/HPS1% Pt/HPS hexanehexanewater water 150150 150150 2 2 100 100 (55) 2 2 (55) 1 1 0.32 96 960.32 (40)(40) (mol0.240.24Me × s) 2 1 1 3 2 1%2% 1%Pt/HPS Pt/HPS-NR Pt/HPS 2nd2 use hexane hexanehexane 150 150 1503 2 41 2 (51) 100 (56) 1001 0.32 (55) 0.21 0.32 2 1% Pt/HPS2 1% 2nd Pt/HPS use 2nd use hexane hexane 150 150 2 2 100 100 (56) (56) 1 1 0.21 0.21 331 77 1 1% Pt/HPS EtOHEtOHhexane 150150 150 22 2 2 4110041 (60)(60) (55) 0.070.070.32 4 2% Ru/HPS-NR 2 hexane 150 3 54 (87) 2 0.05 1 2 1%3 Pt/HPS 2%3 2nd Pt/HPS-NR2% use Pt/HPS-NR 2 2 hexanehexane hexane 150 150 1503 3 41 (51) 2 2 412 (51)0.32 100 (56)0.32 1 0.21 2 1%32% Pt/HPS Pd/HPS-NR2% Pt/HPS-NR 2nd use22 2 hexane hexane150 3 15041 (51) 2 1000.32 (56) 0.21 2% Pd/HPS-NR (AN) (CHA) 2 5 2% Pd/HPS-NR2 hexane 150 3 58 (60)2 0.07 4 2% Ru/HPS-NR2 2 hexane 150 3 54 (87) 0.052 22 3 2%4 Pt/HPS-NR2% Ru/HPS-NR22 2 hexanehexane 150 1503 3542 (87) 41 (51)0.0523 0.32 38 42% Pt/HPS-NR2% Ru/HPS-NR2 (AN) (CHA) hexane hexane BuOH150 1501503 543 2(87) 41530.05 (51) (64) 3 0.320.12 8 5 2% Pd/HPS-NR2 hexaneBuOH 150 1503 58 (60)2 2 3 0.07 53 (64) 2 0.12 46 2% Ru/HPS-NR2 (AN)(AN) (CHA)(CHA) water hexane150 2 150 96 (40) 3 2 0.2454 (87) 0.05 5 5 2%2% Pd/HPS-NR Pd/HPS-NR2 2 (AN) (CHA) hexanehexane 150 150 3 3 58 (60)58 2 (60) 0.07 0.072 4 2% Ru/HPS-NR6 2 (PL)(PL) (CHN)(CHN) waterhexane 150 150 2 96 (40)3 3 3 0.24 54 (87) 2 0.05 57 2% Pd/HPS-NR2 EtOH hexane150 2 15041 (60) 3 0.0758 (60) 0.07 6 water 150 2 963 (40) 3 0.24 6 2% Pd/HPS-NR7 2 (AN) (CHA) waterEtOH 150150 2 2 41 (60) 96 (40) 3 0.07 0.24 2 4 599 2% Pd/HPS-NR2 hexaneTOLTOL 1509090 ambientambient3 10058100 (60) (88)(88) 2 3 4 0.076.706.70 6 2% Pd/HPS-NR2 water 150 2 3 3 96 (40) 0.24 7 7 EtOHEtOH 150 150 2 2 41 (60)41 3 (60) 0.07 0.07 8 BuOH 150 2 53 (64) 0.12 34 72% Pd/HPS-NR8 2 BuOH EtOH150 2 15053 (64) 3 2 0.12 41 (60)34 0.07 10610 2%2% Pd/HPS-NR Pd/HPS-NR2 2 (PL) (CHN) waterEtOHEtOH 1506565 ambientambient 2 100 96100 (40) (78)(78) 0.241.251.25 (PL) (CHN) 3 81% Pd/HPS-NR2 (CHN) BuOH 150 2 3 3 53 (64) 0.12 81% 8 Pd/HPS-NR2 (PL) BuOH BuOH 150 150 2 2 53 (64)53 4(64) 0.12 0.123 7 9 9 TOLTOL EtOH 9090 ambientambient150 100100 (88)2 (88) 4 6.70 416.70 (60) 0.07 (PL)(PL) (CHN)(CHN) 44 9 TOL 90 ambient4 100 (88) 4 6.70 1111 102% Pd/HPS-NR10 2 EtOHEtOHi i-PrOH-PrOH 6565 ambientambient7070 100 ambient ambient100 (78) (78) 4 1.25 100 1001.25 (69)(69) 2.252.25 9 TOL 90 ambient 100 (88) 4 4 6.70 4 101%9 Pd/HPS-NR1% Pd/HPS-NR1% 2Pd/HPS-NR2 (PHA)2 (STY) TOL EtOH 90 ambient 65 ambient100 (88) 100 (78)6.70 1.25 (PHA) (STY) 3 8 BuOH 150 2 4 4 53 (64) 4 0.12 11 101110 11 (PHA) (STY) iEtOH-PrOHi-PrOHEtOH i -PrOH 657070 65 ambient ambientambient 70 100 100 (69) ambient (78)(69) 100 4 (78)2.25 4 1001.252.25 (69) 1.25 2.25 (PL) (PHA) (CHN)(STY) 1%1% Pd/HPS-NR Pd/HPS-NR2 2 (PHA)(PL) (STY)(CHN) 9 1111 i-PrOHi-PrOH TOL70 70 ambient90 ambient ambient 100 (69) 100 4 (69) 1004 2.25 (88) 2.25 4 6.70 5 12 1% Pd/HPS-NR 2 (PHA) (STY) hexane 80 0.25 55 0.13 1212 1%1% Pd/HPS-NRPd/HPS-NR22 (PHA) (STY) hexanehexane 8080 0.25 0.255 92 9292 (98)(98) 0.130.13 10 12 1% Pd/HPS-NR2 hexane EtOH 80 65 0.25 ambient 92 (98) 0.13100 (78) 4 1.25 12 1% Pd/HPS-NR2 hexane 80 0.25 92 (98) 5 0.13 1% Pd/HPS-NR2 (PP) (PPL) (PP) (PPL) 1 1 (PP)(PP) (PPL)(PPL) C12AN =1% 0.14CAN Pd/HPS-NR,0mol/L, = 0.14 mol/L, catalyst 2catalyst loading loading 100 100 mg, mg, values values of conversion of conversionhexane (X) and selectivity (X)80 and (S) are selectivity indicated 0.25 for (S) the 92are reaction (98) indicated 5time 120 formi0.13n.the reaction4 time 120 min. 11 ,0 2 (PP) (PPL) i-PrOH 70 ambient 5 100 (69) 2.25 2 12 2 1% Pd/HPS-NR hexane 80 0.25 3 92 (98) 3 0.13 11 AN,0 C = 0.41CAN,0 mol/L, = 0.41 mol/L, catalyst catalyst loading loading 100 100 mg, mg, values values of X and of XS are and indicated S are indicatedfor the reaction for time the 150 reaction min. CPL time,0 = 0.21 150 mol/L, min. catalystC = 0.21 mol/L, catalyst CCAN,0 == 0.1410.14 AN mol/L,mol/L,,0 catalystcatalyst loadingloading 100100 mg,mg, vavalueslues ofof conversionconversion (X)(X) andand selectivity selectivity (S)(S) areare indicatedindicated forfor thethePL reactionreaction,0 timetime 120120 mimin.n. CAN,0 = 0.14 mol/L,loading catalyst50 mg, 2 MPa loading is partial 100(PHA) hydrogenmg, va lues pressure, of conversion values(STY) of X (X) and and S are selectivity indicated for (S) the are reaction indicated time 90for min. the 4reaction CPHA,0 = 0.48 time mol/L, 120 mi4n. 2 loading 50 mg, 2 MPa is partial hydrogen pressure, values of X and S are indicated for the reaction time 90 min.3 C = 0.48 mol/L, 2 AN,0 2 3 3 PL,0 PHA,0 CCAN,0 == 0.410.41AN ,0 mol/L,mol/L, catalystcatalyst loading loading 100100(PP) mg,mg, values values of(PPL)of XX andand SS areare indicatedindicated 5 forPPfor,0 thethe reactionreaction timetimePL ,0 150150 min.min. CCPL,0 == 0.210.21 mol/L,mol/L, catalystcatalyst Ccatalyst = 0.41 loading mol/L,catalyst 30catalystloading mg, 30 maximumloading mg, maximum 100 values mg, values(PP) values of of X X of andand X andcorresponding corresponding(PPL) S are indicated S are Sindicated. arefor the indicated. reactionC = 0.09 5time mol/L,C 150 values= min. 0.09 ofmol/L,C X and = S0.21 indicated values mol/L, for of catalyst X and S indicated for the PP,0 4 4 loadingloading 1loading 50 50CAN mg,mg,,0 = 0.1450 22 mg, MPa MPamol/L,the 2reaction MPa isis catalyst partialpartial is time partial 150loading hydrogenhydrogen min. hydrogen 100 mg, pressure, pressure,pressure, values ofvalues conversion valuesvalues of X of andof (X) XX S andareand indicatedselectivity SS areare indicatedindicated for (S) the are reaction indicated forfor the thetime for reactionreaction 90the min. reaction C timetimePHA time,0 = 90 900.48 120 min.min. mol/L, min. 4 C C PHAPHA,0,0 == 0.480.48 mol/L,mol/L, reaction1 AN,0 time 150 min. 2 C = 0.14 mol/L, catalyst loading 100 mg, values of conversion (X) and selectivity 5 (S) are indicated3 for the reaction time 120 min. catalyst catalystloadingCAN,0 = 0.41loading 30 mol/L, mg, 30 catalystmg, maximum maximum loading values values 100 mg, of of valuesX Xand and correspondingof Xcorresponding and S are indicated S are indicated. S forare the indicated. reactionCPP,0 = 0.09 time 5 5 mol/L,C 150PP,0 min.= values 0.09 C PL mol/L,of,0 =X 0.21 and mol/L,valuesS indicated catalyst of forX and S indicated for catalyst loading2 AN,0 30 mg, maximum values of X and corresponding S are indicated. CPP,0 = 0.09 mol/L,3 PL,0 values of X and S indicated for C = 0.41 mol/L, catalyst loading 100 mg, values of X and S are indicated for the reaction time 150 min. 4C = 0.21 mol/L, catalyst loadingthe reaction 50 mg, time 2 MPa150 min. is partial hydrogen pressure, values of X and S are indicated for the reaction time 90 min. CPHA,0 = 0.48 mol/L,5 thethe 12 reactionreaction loading1% timetime Pd/HPS-NR 50 150150 mg, min.min. 2 MPa is2 partial hydrogenHowever, pressure, values in spite of X ofand the S hexaneare high indicated initial for80 the reaction reaction 0.25 rate,time 90 Pt-containing min. 4 C 92PHA (98),0 = 0.48 HPS mol/L, catalysts 0.13 deacti- catalyst loading 30 mg, maximum values of X and corresponding S are indicated. 5 CPP,0 = 0.09 mol/L, values of X and S indicated for catalyst loading 30 mg, maximum values of X and corresponding S are indicated. 5 CPP,0 = 0.09 mol/L, values of X and S indicated for the reaction time 150 min. vated, especially at high initial concentrations of AN, which is seen from the shape of kinetic the reaction time 150 min. curves(PP) (see Figure(PPL)8a). At the same time, the apparent activation energy was 53 ± 5 kJ/mol 1 (Figure8b), which is comparable with literature data [ 21]. Moreover, it was found that 1 CAN,0 = 0.14 mol/L, catalyst loading 100 mg, values of conversion (X) and selectivity (S) are indicated for the reaction time 120 min. 2 1% Pt/HPS is rather stable at the reuse (Table2, #1,2); although3 the initial reaction rate CAN,0 = 0.41 mol/L, catalyst loading 100 mg, values of X and S are indicated for the reaction time 150 min. CPL,0 = 0.21 mol/L, catalyst 4 loading 50 mg, 2 MPa is partial hydrogenslightly pressure, decreases, values conversion of X and S are and indicated selectivity for the achieved reaction in time 120 90 min min. of 4 C thePHA reaction,0 = 0.48 mol/L, remains 5 catalyst loading 30 mg, maximum valuesthe same.of X and Observed corresponding loss ofS are activity indicated. during 5 CPP,0 the = 0.09 same mol/L, reaction values run of Xcan and beS indicated due to strongfor the reaction time 150 min. adsorption of AN and products on the metal surface, acting similar to poisons [22,23], but this effect seems to take place only in situ under the reaction conditions. Hydrogenation of PL, PHA, and PP traditionally is carried out using Pd-containing

catalysts. In the case of PL hydrogenation (Figure9), different reaction conditions (solvents, temperatures, and pressures) can be used [24]. Earlier, we showed that PL can

be successfully hydrogenated in a gas phase in a ﬁxed-bed reactor over 0.5% Pd/HPS catalyst [25]. In this work, an autoclave-type reactor was used, and three solvents (Table2 , ◦ #6–8) at 150 C and hydrogen partial pressure of 2 MPa (comparable with some other works) [26] were tested. As can be seen from Table2 (#6–8), water is the best solvent,

Molecules 2021, 26, x FOR PEER REVIEW 7 of 15

Figure 7. CHA accumulation using different noble metal NPs supported on HPS-NR2 (150 °C, 3 MPa, CAN,0 = 0.41 mol/L, catalyst loading 100 mg).

Hydrogenation of PL, PHA, and PP traditionally is carried out using Pd-containing catalysts. In the case of PL hydrogenation (Figure 9), different reaction conditions (solvents, temperatures, and pressures) can be used [24]. Earlier, we showed that PL can be successfully hydrogenated in a gas phase in a fixed-bed reactor over 0.5% Pd/HPS catalyst [25]. In this work, an autoclave-type reactor was used, and three solvents (Table 2, Molecules 2021, 26, x FOR PEER REVIEW 7 of 15 #6–8) at 150 °C and hydrogen partial pressure of 2 MPa (comparable with some other works) [26] were tested. As can be seen from Table 2 (#6–8), water is the best solvent, al- Figurelowing 7. CHA the accumulation highest using hydrogenation different noble metal NPs rate, supported while on HPS-NR the2 (150selectivity °C, 3 over 2% Pd/HPS-NR2 with MPa, CAN,0 = 0.41 mol/L, catalyst loading 100 mg). respect to cyclohexanone (CHN) is moderate (91% to CHL at 50% of PL conversion) and needsHydrogenation further of improvement. PL, PHA, and PP traditionally is carried out using Pd-containing catalysts. In the case of PL hydrogenation (Figure 9), different reaction conditions (solvents, temperatures, and pressures) can be used [24]. Earlier, we showed that PL can be successfully hydrogenated in a gas phase in a fixed-bed reactor over 0.5% Pd/HPS cata-

Molecules 2021, 26, 4687 lyst [25]. In this work, an autoclave-type reactor was used, and three solvents (Table7 of 152, #6–8) at 150 °C and hydrogen partial pressure of 2 MPa (comparable with some other works) [26] were tested. As can be seen from Table 2 (#6–8), water is the best solvent, al- lowing the highest hydrogenation rate, while the selectivity over 2% Pd/HPS-NR2 with allowingrespect to the cyclohexanone highest hydrogenation (CHN) is rate,moderate while (91% the selectivity to CHL at over 50%2% of PL Pd/HPS-NR conversion)2 with and respectneeds further to cyclohexanone improvement. (CHN) is moderate (91% to CHL at 50% of PL conversion) and needs further improvement.

(a) (b) (a) (b) Figure 8. Effect of AN initial concentration (a) and temperature (b) on selective hydrogenation of FigureFigureAN 8. 8.to EffectEffect CHA of AN using initial concentration 1wt.% Pt/HPS ( (aa)) and and temperature temperature(2 MPa, (catalyst (bb)) on on selective selective loading hydrogenation hydrogenation 100 mg).of of ANAN toto CHACHA usingusing 11wt.% wt.% Pt/HPS (2 (2 MPa, MPa, catalyst catalyst loading loading 100 100 mg). mg).

Figure 9. Scheme of selective hydrogenation of PL to CHN.

PHA can be easily hydrogenated to styrene (STY) (Figure 10) under mild reaction conditions (low temperatures and ambient hydrogen pressure). Nevertheless, it is very Figure 9. Scheme of selective hydrogenation of PL to CHN. difficultFigure to 9.provide Scheme high ofselectivity selective with hydrogenation respect to STY [27] ofdue PL to toexceptionally CHN. high reactivityPHA of can triple be easily and double hydrogenated carbon–carbon to styrene bonds, (STY) when (Figure one of10 )the under hydrogen mild reactionatoms is conditionssubstituted (low in a temperaturesbenzene ring. andIn the ambient case of hydrogen1wt.% Pd/HPS-NR pressure).2, TOL Nevertheless, was found it to is be very the difﬁcultbest solvent, toPHA provide providing can high beexceptionally selectivity easily with hydrogenatedhigh respect activity to (Figure STY [27 11)]to due andstyrene to 88% exceptionally selectivity (STY) highwith (Figure 10) under mild reaction reactivityrespectconditions to of STY triple at and(lowclose double to temperatures100% carbon–carbon PHA conversion bonds, and (Table when ambient 2, one #9–11), of the hydrogenwhich hydrogen is comparable atoms pressure). is Nevertheless, it is very substitutedwith other inreports a benzene [28]. It ring. is noteworthy In the case ofthat 1 wt.%different Pd/HPS-NR temperatures2, TOL were was tested found which to be theweredifficult best about solvent, 10–15 to providing provide°C lower exceptionally than high the boiling highselectivity activity point (Figureof withthe 11corresponding) andrespect 88% selectivity solvent.to STY with The [27] due to exceptionally high respecthigherreactivity tothe STY temperature, at closeof triple to 100%the higherand PHA conversiondoublethe selectivity (Tablecarbon–carbon to2 ,olefinic #9–11), whichproduct; is bonds, comparablehowever, whenhydro- with one of the hydrogen atoms is Molecules 2021, 26, x FOR PEER REVIEWothergenation reports rate [usually28]. It isgoes noteworthy through a that maximum, different which temperatures is 90 °C for were TOL tested [29]. which were 8 of 15 aboutsubstituted 10–15 ◦C lower in than a benzene the boiling pointring. of theIn correspondingthe case of solvent. 1wt.% The Pd/HPS-NR higher the 2, TOL was found to be the temperature,best solvent, the higher providing the selectivity exceptionally to oleﬁnic product; however,high activity hydrogenation (Figure rate 11) and 88% selectivity with usually goes through a maximum, which is 90 ◦C for TOL [29]. respect to STY at close to 100% PHA conversion (Table 2, #9–11), which is comparable with other reports [28]. It is noteworthy that different temperatures were tested which were about 10–15 °C lower than the boiling point of the corresponding solvent. The

higher the temperature, the higher the selectivity to olefinic product; however, hydrogenation rate usually goes through a maximum, which is 90 °C for TOL [29].

Figure 10. 10.Scheme Scheme of selective of hydrogenation selective hydrogenation of PHA to STY. of PHA to STY.

Figure 11. Solvent effect on PHA hydrogenation to STY over 1wt.% Pd/HPS-NR2 (ambient H2 pressure, CPHA,0 = 0.48 mol/L, catalyst loading 30 mg).

PP was also hydrogenated using Pd-containing catalyst (1wt.% Pd/HPS-NR2). Phe- nylpropanol (PPL) was found to be the main reaction product (Figure 12).

Figure 12. Scheme of selective hydrogenation of PP to PPL.

Variation of overall pressure (Figure 13a) allowed determining the formal kinetic parameter with respect to hydrogen, which was close to the unit. The study of the temperature effect was carried out at 0.25 MPa (Figure 13b). It was found that the reaction rate increased with the increase of temperature from 60 °C up to 80 °C (in this range, Ea,app = 75 ± 5 kJ/mol, calculated taking into account the same assumptions as in the case of BZ hydrogenation). Further increase of temperature resulted in noticeable decrease of the PP hydrogenation rate due to the high vapor pressure of the solvent (hexane). Thus, 80 °C can be considered as the optimal temperature (see also Table 2, #12), which provided 98% conversion of PP (for 240 min) and exclusive formation of PPL (100% selectivity).

Molecules 2021,, 26,, xx FORFOR PEERPEER REVIEWREVIEW 8 of 15

Molecules 2021, 26, 4687 8 of 15

Figure 10. Scheme of selective hydrogenation of PHA to STY.

2 2 FigureFigure 11. SolventSolvent effect effect on on PHA PHA hydrogenation hydrogenation to to STY STY over over 1wt.% 1 wt.% Pd/HPS-NR Pd/HPS-NR2 (ambient(ambient2 (ambient HH2 H2 pressure, CPHA,0 = 0.48 mol/L, catalyst loading 30 mg). pressure, CCPHAPHA,0,0 == 0.48 0.48 mol/L, mol/L, catalyst catalyst loading loading 30 30 mg). mg).

PPPP waswas also also hydrogenated hydrogenated using using Pd-containing Pd-containing catalyst catalyst (1 wt.% (1wt.% Pd/HPS-NR Pd/HPS-NR2). Phenyl-22). Phe- propanolnylpropanol (PPL) (PPL) was was found found to be to the be the main main reaction reaction product product (Figure (Figure 12). 12).

FigureFigure 12.12. SchemeScheme ofof selectiveselective hydrogenationhydrogenation ofof PPPP toto PPL.PPL.

VariationVariation ofof overalloverall pressurepressure (Figure(Figure 1313a)a) allowedallowedallowed determiningdeterminingdetermining thethethe formalformalformal kinetickinetickinetic parameterparameter withwith respectrespect toto hydrogen,hydrogen, whichwhich waswas closeclose toto thethe unit.unit. The study of the tem- peratureperature effecteffect waswas carriedcarried outout atat 0.250.25 MPaMPa (Figure(Figure 1313b).b). ItIt waswas foundfound thatthat thethe reactionreaction rate increased with the increase of temperature from 60 ◦C up to 80 ◦C (in this range, rate increased with the increase of temperature from 60 °C up to 80 °C (in this range, Ea,appa,app ± E= a,app75 ±= 5 75 kJ/mol,5 kJ/mol calculated, calculated taking takinginto account into account the same the assumptions same assumptions as in the as incase the of case BZ ofhydrogenation). BZ hydrogenation). Further Further increase increase of temperature of temperature resulted resulted in noticeable in noticeable decrease decrease of the PP of Molecules 2021, 26, x FOR PEER REVIEWthehydrogenation PP hydrogenation rate due rate to duethe high to the vapor high vaporpressure pressure of the ofsolvent the solvent (hexane). (hexane). Thus,9 of Thus,80 15 °C 80 ◦C can be considered as the optimal temperature (see also Table2, #12), which provided can be considered as the optimal temperature (see also Table 2, #12), which provided 98% 98% conversion of PP (for 240 min) and exclusive formation of PPL (100% selectivity). conversion of PP (for 240 min) and exclusive formation of PPL (100% selectivity).

(a) (b)

FigureFigure 13. Effect of overall pressure (a) and temperature (b) on selective hydrogenation of PP to PPL PPL using 1wt.% Pd/HPS-NR2 (CPP,0 = 0.09 mol/L, catalyst loading 100 mg). using 1 wt.% Pd/HPS-NR2 (CPP,0 = 0.09 mol/L, catalyst loading 100 mg). It is noteworthy that, across the whole range of chosen temperatures, 98% selectivity with respect to PPL was found at 0.25 MPa overall pressure, which is a very promising result in comparison with other reported data [30,31]. A slight decrease of selectivity (at 99% of PP conversion) was observed at higher pressures: 97% at 5 MPa, and about 95% at 10 MPa.

3. Discussion The results of our work reported here demonstrate that noble metal NPs are effectively stabilized within polymeric networks of HPSs. HPSs of different types and properties (SSA, hydrophobicity, functional groups, etc.) are commercially available at a relatively low price while being chemically and mechanically stable. Moreover, contrary to most inorganic solids (such as alumina, silica, zeolites, etc.), HPSs have excellent wettability in organic solvents and do not present surface acidity, which is known to be responsible for the formation of a number of byproducts and carbon deposits, leading to catalyst deactivation. HPS-based catalysts containing NPs of different metals (Pt, Pd, Ru) were prepared via simple wet-impregnation and thoroughly characterized by different physical and chemical methods. Pd NPs had mean diameter of 2.6 ± 0.4 nm and were evenly distributed through the polymeric network irrespective of the polymer type, palladium loading, or reduction method. The 2% Pd/HPS-NR2 with hexane as solvent demonstrated extraordi- nary catalytic properties in BZ to CH hydrogenation, showing 100% CH selectivity at close to 100% conversion of BZ. Pd NPs stabilized by HPS also showed excellent results in PP hydrogenation, giving almost exclusively the target PPL. Pt NPs had slightly bigger mean diameter (3.9 ± 1.7 nm) compared to Pd and also some aggregates with diameters of >11 nm. The 2% Pt/HPS-NR2 also demonstrated 100% CH selectivity at up to full BZ conversion, but outperformed the Pd-based catalyst in terms of a twofold higher reaction rate under the same reaction conditions. The 2% Ru/HPS-NR2 contained small NPs of RuO2 of about 2–4 nm in diameter, which were distributed nonuniformly, closer to the outer surface of the polymer granule, and showed much lower performance in hydrogenation of BZ, compared to Pd and Pt. In contrast, it outperformed Pt- and Pd-based HPS in production of CHA during AN hydrogenation. Synthesized Pt-, Pd-, and Ru-containing HPS-based catalysts were shown to be highly active and selective in hydrogenation of both nonsubstituted and substituted arenes. Catalytic properties of synthesized samples are promising in comparison with some other reported results [32]. For example, hydrogenation of BZ and TL proceeded with 100% selectivity to CH and MCH, respectively, while using Pt NPs supported on HPS or HPS-NR2. For comparison, in the case of zeolite-supported catalysts, isomerization took

Molecules 2021, 26, 4687 9 of 15

It is noteworthy that, across the whole range of chosen temperatures, 98% selectivity with respect to PPL was found at 0.25 MPa overall pressure, which is a very promising result in comparison with other reported data [30,31]. A slight decrease of selectivity (at 99% of PP conversion) was observed at higher pressures: 97% at 5 MPa, and about 95% at 10 MPa.

3. Discussion The results of our work reported here demonstrate that noble metal NPs are effectively stabilized within polymeric networks of HPSs. HPSs of different types and properties (SSA, hydrophobicity, functional groups, etc.) are commercially available at a relatively low price while being chemically and mechanically stable. Moreover, contrary to most inorganic solids (such as alumina, silica, zeolites, etc.), HPSs have excellent wettability in organic solvents and do not present surface acidity, which is known to be responsible for the formation of a number of byproducts and carbon deposits, leading to catalyst deactivation. HPS-based catalysts containing NPs of different metals (Pt, Pd, Ru) were prepared via simple wet-impregnation and thoroughly characterized by different physical and chemical methods. Pd NPs had mean diameter of 2.6 ± 0.4 nm and were evenly distributed through the polymeric network irrespective of the polymer type, palladium loading, or reduction method. The 2% Pd/HPS-NR2 with hexane as solvent demonstrated extraor- dinary catalytic properties in BZ to CH hydrogenation, showing 100% CH selectivity at close to 100% conversion of BZ. Pd NPs stabilized by HPS also showed excellent results in PP hydrogenation, giving almost exclusively the target PPL. Pt NPs had slightly bigger mean diameter (3.9 ± 1.7 nm) compared to Pd and also some aggregates with diameters of >11 nm. The 2% Pt/HPS-NR2 also demonstrated 100% CH selectivity at up to full BZ conversion, but outperformed the Pd-based catalyst in terms of a twofold higher reaction rate under the same reaction conditions. The 2% Ru/HPS-NR2 contained small NPs of RuO2 of about 2–4 nm in diameter, which were distributed nonuniformly, closer to the outer surface of the polymer granule, and showed much lower performance in hydrogenation of BZ, compared to Pd and Pt. In contrast, it outperformed Pt- and Pd-based HPS in production of CHA during AN hydrogenation. Synthesized Pt-, Pd-, and Ru-containing HPS-based catalysts were shown to be highly active and selective in hydrogenation of both nonsubstituted and substituted arenes. Cat- alytic properties of synthesized samples are promising in comparison with some other reported results [32]. For example, hydrogenation of BZ and TL proceeded with 100% selectivity to CH and MCH, respectively, while using Pt NPs supported on HPS or HPS-NR2. For comparison, in the case of zeolite-supported catalysts, isomerization took place, resulting in the formation of methylcyclopentane as the main product [32]. Hydrogenation of NL to TL over Pt/HPS-NR2 proceeded with the selectivity of 88% at 94% of NL conversion, which is comparable with some reported results [32], or, in some cases, even higher [33]. Finally, we would like to underline that hyper-cross-linked polymers with various functionalities and cross-linking degrees should be used as catalytic supports for different metal NPs and should be tested in liquid-phase hydrogenations of arenes, giving much attention to catalyst stability in view of their multiple reuse. This work is in progress and will be reported elsewhere.

4. Materials and Methods 4.1. Materials HPS (Purolite Int., Llantrisant, UK), used as catalyst support, was of two types: hyper- cross-linked nonfunctionalized polystyrene, Macronet MN270 (BET SSA 1337 m2/g), and HPS containing tertiary amino groups, MN100 (BET SSA 724 m2/g), designated here as HPS-NR2. Both supports were washed with distilled water and acetone and then dried under vacuum as described elsewhere [34]. Benzene (BZ, 99.8%), toluene (TOL, 99.8%), naphthalene (NL, 99%), aniline (AN, 99%), anthracene (ANC, 97%), phenylacethylene (PHA, 98%), phenol (PL, ≥99%), propiophenone (PP, 98%), diphenylamine (DPA, 99%), Molecules 2021, 26, 4687 10 of 15

tetrahydrofuran (THF, ≥99.9%), methanol (MeOH, 99.8%), acetone (≥99.5%), hydrogen peroxide (H2O2, 35%), isopropanol (i-PrOH, ≥99.5%), butanol (BuOH, ≥99%), hexane (≥99%), and dodecane (≥99%) were obtained from Sigma-Aldrich. Chloroplatinic acid hydrate (H2PtCl6·6H2O, Pt content 38.41%), palladium acetate (Pd(CH3COO)2, Pd content 47.68%), and ruthenium hydroxychloride (Ru(OH)Cl3, Ru content 45.05%) were purchased from JSC “Aurat” (Moscow, Russia). Sodium hydroxide (NaOH) was obtained from Reakhim (Moscow, Russia). Reagent-grade hydrogen of 99.999% purity was received from AGA (Tver, Russia). All chemicals were used as received. Distilled water was puriﬁed with an Elsi-Aqua water puriﬁcation system.

4.2. Catalyst Synthesis and Characterization Pt-, Pd-, and Ru-containing HPS-based catalysts were synthesized via wet-impregnation according to procedure, which is described elsewhere [34–36]. In a typical experiment, 1 g of pretreated, dried, and crushed (<63 µm) granules of HPS were impregnated with 2.8 mL of the THF solution of precursor (H2PtCl6·6H2O or Pd(CH3COO)2) of a chosen concentration. The HPSs impregnated with Pt or Pd were dried, washed with distilled water until reaching a neutral pH, and dried again at 70 ◦C until the constant weight was achieved. In the case of Ru/HPS, a complex solvent (THF, MeOH, and water in a volu- metric ratio of 7:1:1) with dissolved therein calculated amount of Ru(OH)Cl3 was used for impregnation. The Ru-containing HPS was dried at 70 ◦C for 1 h, the dried catalyst was boiled in aqueous solution of NaOH (concentration of 0.1 mol/L) at continuous stirring, and then H2O2 was added. The resulting catalyst was washed with distilled water until neutral pH was reached, and dried again at 70 ◦C. Thus, the catalysts Pt/HPS, Pt/HPS-NR2, Pd/HPS-NR2, and Ru/HPS-NR2 were synthesized containing either 1 wt.% or 2 wt.% of noble metals. Before the experiments, all the catalyst samples were activated in a hydrogen flow (100 mL/min) at 300 ◦C for 3 h. Such activation has no influence on the HPS structure [11] (see also Figure S1) and results in formation of NPs of metallic Pd or Pt and RuO2 (see the data of XPS below) in a micro–mesoporous polymeric environment (BET SSA for all the samples was in the range 700–1000 m2/g). Figure 14 shows STEM data using the example of the 1% Pt/HPS-NR2, 2 wt.% Pd/HPS-NR2, and 2% Ru/HPS-NR2 catalysts. It was found that among these three samples, Pd NPs were the most evenly distributed (Figure 14b) and had mean diameter of 2.6 ± 0.4 nm, which is typical for HPS impregnated with Pd acetate, irrespective of the polymer type, palladium loading, and reduction method [37,38]. Pt NPs had mean diameter of 3.9 ± 1.7 nm, but also a lot of aggregates with diameters up to 11 nm and higher (Figure 14a). The 2 wt.% Ru/HPS-NR2 contained small NPs of RuO2 of about 2–4 nm in diameter (Figure 14c), which were located nonuniformly, closer to the outer surface of the polymer granule [39]. See also Figure 14d, where light regions correspond to RuO2 (the average content of elements calculated via EDX is the following: carbon 34%, oxygen 41%, ruthenium 25%). Metal state was confirmed by the XPS analysis. It was shown that palladium is present 0 in the form of metallic NPs (BE of Pd 3d5/2 is 335.0 ± 0.1 eV for Pd NPs and 336.0 ± 0.1 eV for small Pd clusters) and PdO (BE is 337.2 ± 0.1 eV [40]). The metallic form Pd0 was predominant on the catalysts’ surface (Figure S2c). The existence of oxide can be explained by the fact that, after the activation in H2 flow, the catalysts were stored in air. In the case of 1 wt.% Pt/HPS (Figure S2a) and 2 wt.% Pt/HPS-NR2 (Figure S2b), the following 0 values of BE (±0.1 eV) of Pt 4f7/2 were found: 71.5 eV (Pt ) and 72.9 eV (PtO) [40]. For 1% Pt/HPS-NR2 [11], BE of Pt 4f7/2 was equal to 71.4 ± 0.1 eV, which corresponds to 0 Pt [40]. In the case of 2 wt.% Ru/HPS-NR2 (Figure S2d), ruthenium was in the form of RuO2 (BE is 281.2 ± 0.1 eV) and RuO2*nH2O (BE is 283.0 ± 0.1 eV). Molecules 2021, 26, x FOR PEER REVIEW 11 of 15

ymer type, palladium loading, and reduction method [37,38]. Pt NPs had mean diameter of 3.9 ± 1.7 nm, but also a lot of aggregates with diameters up to 11 nm and higher (Figure 14a). The 2wt.% Ru/HPS-NR2 contained small NPs of RuO2 of about 2–4 nm in diameter (Figure 14c), which were located nonuniformly, closer to the outer surface of the poly- Molecules 2021, 26, 4687 11 of 15 mer granule [39]. See also Figure 14d, where light regions correspond to RuO2 (the average content of elements calculated via EDX is the following: carbon 34%, oxygen 41%, ruthenium 25%).

(a) (b)

Figure 14. HAADF-STEM images of activated samples ((a) 1% Pt/HPS-NR2 (scale 100 nm), (b) 2% Pd/HPS-NR2 (scale 50 Figure 14. HAADF-STEM images of activated samples ((a) 1% Pt/HPS-NR2 (scale 100 nm), (b) 2% Pd/HPS-NR2 (scale nm), (c) 2% Ru/HPS-NR2 (scale 10 nm)) and SEM image (d) of 2% Ru/HPS-NR2 (scale 20 μm). 50 nm), (c) 2% Ru/HPS-NR2 (scale 10 nm)) and SEM image (d) of 2% Ru/HPS-NR2 (scale 20 µm). 4.3. ReactionMetal state Procedure was confirmed and Analysis by the of Reaction XPS analysis. Mixture It was shown that palladium is present inTesting the form of Pt-,of metallic Pd-, and NPs Ru-containing (BE of Pd 3d HPS-based5/2 is 335.0 ± samples 0.1 eV for in Pd hydrogenation0 NPs and 336.0 of differ- ± 0.1 eVent for arenes, small with Pd clusters) the exception and PdO of PHA, (BE wasis 337.2 carried ± 0.1 out eV in [40]). a stainless-steel The metallic autoclave form Pd reactor0 was predominant(Parr Instruments, on the Moline, catalysts’ IL, surface USA) having (Figure an S2c). internal The volumeexistence of of 80 oxide mL. Incan a typicalbe ex- plainedexperiment, by the 0.05 fact g that, (or 0.1 after g) ofthe preliminarily activation in activatedH2 flow, the catalyst catalysts was were placed stored in the in reactor.air. In theThen, case substrate of 1wt.% and Pt/HPS 40 mL (Figure of solvent S2a) were and added.2 wt.% AfterPt/HPS-NR that, the2 (Figure reactor S2b), was sealed,the following purged valueswith nitrogen, of BE (±0.1 and eV) heated of Pt under4f7/2 were stirring found: (1500 71.5 rpm) eV (Pt up0) to and operating 72.9 eV temperature.(PtO) [40]. For After 1% Pt/HPS-NRreaching working2 [11], BE temperature, of Pt 4f7/2 was the equal ﬁrst to sample 71.4 ± of0.1 the eV, reaction which corresponds mixture was to taken. Pt0 [40]. Then, In nitrogen was replaced with hydrogen, overall working pressure was attained (time “zero” for the reaction), and the reaction started. Sampling of the reaction mixture was carried out via long narrow capillary (internal diameter of 0.1 mm); the volume of each sample

was 200 µL. In the case of PHA, hydrogenation was carried out in a 60 mL isothermal glass batch reactor installed in a shaker at vigorous stirring (more than 800 two-sided shakings per minute). The total volume of the liquid phase was 30 mL. A recirculating bath (LOIP LT 100, Molecules 2021, 26, 4687 12 of 15

Saint Petersburg, Russia) was used to stabilize the reaction temperature within ±1 ◦C, with water as a heating medium. The reactor was connected to a gasometrical burette for online hydrogen consumption control. At the beginning of each experiment, the temperature was stabilized, the reactor was charged with catalyst, and the catalyst was kept under hydrogen for 60 min. Then PHA was added, and reaction was started. Samples of the reaction mixture were analyzed via GC (Kristallux 4000M) equipped with FID and capillary column ZB-WAX (60 m × 0.53 mm i.d., 1 µm film thickness) or GC–MS (Shimadzu GCMS-QP2010S) equipped with a capillary column HP-1MS (100 m × 0.25 mm i.d., 0.50 µm film thickness). Helium was used as a carrier gas. The concentrations of the reaction mixture components were calculated using absolute calibration method using chemically pure components (in the case of GC) or using the internal standard calibration method (DPA was used as an internal standard) (in the case of GC–MS). Conversion of substrates was defined as

−1 X (%) = (Csub,0 − Csub,i) × Csub,0 × 100. (1)

Selectivity with respect to target product was given as

−1 S (%) = Cprod,i × (Csub,0 − Csub,i) × 100. (2)

Initial reaction rate was designated as R0, [molsub·molMe−1·s−1 ]:

−1 R0 = (Csub,0 − Csub,i) × (CMe × τi) . (3)

4.4. Catalyst Characterization Methods HPS-based catalysts were characterized by liquid nitrogen physisorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM). Liquid nitrogen physisorption was carried out using a Beckman Coulter SA 3100 (Coulter Corporation, Miami, FL, USA). Prior to the analysis, each sample was placed in a quartz cell installed in the Becman Coulter SA-PREP. The samples were pretreated over 60 min under nitrogen at 120 ◦C. Once the pretreatment was completed, the cell was cooled and weighed, and then transferred to the analytical port. Analysis was performed at −196 ◦C and at relative pressure of 0.9814 (for pores less than 100 nm in diameter) to obtain a PSD (ADS) profile. DRIFTS analysis was carried out using an IRPrestige-21 FTIR spectrometer (Shimadzu, Kyoto, Japan) equipped with a DRS-8000 diffuse reflectance accessory (Shimadzu, Japan). The background sample was a mirror of the material of the optical system of the DRS-8000 accessory. All spectra were recorded in the 4000–500 cm−1 range of wavenumbers at a resolution of 4 cm−1. XPS data were obtained using Mg Kα (hν = 1253.6 eV) radiation with an ES-2403 spectrometer (Institute for Analytic Instrumentation of RAS, Saint Petersburg, Russia) equipped with an energy analyzer PHOIBOS 100-MCD5 (SPECS, Berlin, Germany) and X-ray source XR-50 (SPECS, Berlin, Germany). All the data were acquired at X-ray power of 250 W. Survey spectra were recorded at an energy step of 0.5 eV with an analyzer pass energy of 40 eV, and high-resolution spectra were recorded at an energy step of 0.05 eV with an analyzer pass energy of 7 eV. Samples were outgassed for 180 min before analysis and were stable during the examination. The data analysis was performed via CasaXPS. STEM characterization was carried out using an FEI Tecnai Osiris instrument (Thermo Fisher Scientific, Waltham, MA, USA) operating at an accelerating voltage of 200 kV, equipped with a high-angle annular dark field (HAADF) detector (Fischione, Export, PA, USA) and an energy-dispersive X-ray (EDX) microanalysis spectrometer (EDAX, Mahwah, NJ, USA). Samples were prepared by embedding the catalyst in epoxy resin followed by microtomming (ca. 50 nm thick) at ambient temperature. For the image processing, DigitalMicrograph (Gatan, Pleasanton, CA, USA) software and TIA (Thermo Molecules 2021, 26, 4687 13 of 15

Fisher Scientiﬁc, Waltham, MA, USA) were used. Holey carbon/Cu grid was used as a sample support.

Supplementary Materials: The following are available online, Figure S1: DRIFT spectra of 2% Pt/HPS-NR2 (a), 2% Pd/HPS-NR2 (b), and 2% Ru/HPS-NR2 (c): initial (black line) and after activation in hydrogen flow (red line), Figure S2: High-resolution XPS spectra of Pt 4f (a,b), Pd 3d (c), and Ru 3d (d) in the activated samples: 1% Pt/HPS (a), 2% Pt/HPS-NR2 (b), 2% Pd/HPS-NR2 (c), and 2%-Ru/HPS-NR2 (d). Author Contributions: Conceptualization, A.V.B. and L.K.-M.; methodology, A.V.B.; data curation, A.V.B.; validation, L.K.-M. and L.Z.N.; investigation, E.S.B., A.V.M. and A.O.P.; formal analysis, E.S.B. and A.O.P.; resources, M.G.S.; writing—original draft preparation, L.Z.N.; writing—review and editing, L.K.-M.; visualization, G.N.D.; supervision, L.K.-M.; project administration, L.K.-M. and L.Z.N.; funding acquisition, M.G.S. and L.K.-M. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the Russian Science Foundation, grant number 20-19-00386. Data Availability Statement: Data sharing is not applicable to this article. Acknowledgments: The authors highly appreciate the work of Irina Yu. Tiamina on the catalysts preparation. The authors thank Alexander L. Vasiliev (National Research Centre “Kurchatov Insti- tute”, Moscow, Russia) for help with STEM studies of the catalysts. Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. Sample Availability: Samples of the HPS-based catalysts are available from the authors.

Abbreviations AN, aniline; ANC, anthracene; BZ, benzene; CH, cyclohexane; CHA, cyclohexylamine; CHN, cyclohexanone; 9,10-DANC, 9,10-dihydroanthracene; diphenylamine, DPA; HPS, hyper-cross-linked polystyrene; MCH, methylcyclohexane; NL, naphthalene; NP, nanoparticle; PHA, phenylacethylene; PL, phenol; PP, propiophenone, PPL, phenyl- propanol; STY, styrene; TL, tetralin; TOL, toluene.

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