Hynek Balcar

Academy of Sciences of the Czech Republic, Praha, Praha, Czech Republic

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Publications (71)150.62 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Chain-growth polymerization of 1,4-diethynylbenzene into conjugated crosslinked polyacetylene-type poly(1,4-diethynylbenzene)s (PDEBs) is reported. While metathesis catalysts (WCl6/Ph4Sn, MoCl5/Ph4Sn, Mo Schrock carbene) fail in this polymerization, insertion Rh catalysts ([Rh(nbd)acac], [Rh(nbd)Cl](2)) provide microporous PDEBs in high yields. The Brunauer-Emmett-Teller (BET) surface, S-BET, of PDEBs prepared with [Rh(nbd)acac] increases, in dependence on the polymerization solvent, in the order: THF << pentane < benzene < methanol < CH2Cl2. S-BET further increases with both increasing monomer concentration and increasing polymerization temperature and reaction time, reaching a highest value of 1469 m(2) g(-1). In addition to micropores, PDEBs contain mesopores. The mesopore volume and average mesopore diameter increase with the time and the temperature of the polymerization up to 2.52 cm(3) g(-1) and 22 nm (72 h, 75 degrees C). The post-polymerization thermal treatment of PDEB (280 degrees C) results in formation of new crosslinks and modification of PDEB texture and sorption behavior manifested mainly by enhancement of H-2 adsorption capacity up to 4.55 mmol g(-1) (77 K, 750 Torr).
    Macromolecular Chemistry and Physics 10/2014; 215(19). DOI:10.1002/macp.201400198 · 2.45 Impact Factor
  • Journal of Polymer Research 09/2014; 21(9). DOI:10.1007/s10965-014-0557-6 · 1.90 Impact Factor
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    ABSTRACT: Ruthenium olefin metathesis catalysts bearing a polar quaternary ammonium group in N-heterocyclic ligand were immobilized on silica and siliceous mesoporous molecular sieves with different pore sizes (SBA-15 and MCM-41). The activity of the heterogeneous catalysts was found to increase with an increase in pore size of the support used, with the best results observed for SBA-15-supported catalyst. The influence of reaction conditions (temperature, solvent, catalyst, and substrate concentration) on the efficiency of new heterogeneous catalysts was established. A significant influence of the counterion present in the ruthenium complex on the activity of immobilized catalysts was also found: those derived from chloride containing ion exhibited the highest activity. High activity in ring-closing metathesis of substrates as citronellene, 1,7-octadiene, and diallyl compounds as well as in cross-metathesis of unsaturated aliphatic compounds with methyl acrylate was observed under optimized conditions. In some cases, heterogenization led to catalysts with efficiency higher than those observed for corresponding homogeneous complexes.
    ACS Catalysis 08/2014; 4(4):3227–3236. DOI:10.1021/cs500796u · 7.57 Impact Factor
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    ABSTRACT: The Hoveyda-Grubbs type Zhan catalysts (ZC) and Grubbs second generation catalyst (GII) were immobilized on SBA-15 mesoporous molecular sieve by non-covalent interactions and phosphine linkers, respectively. Both hybrid catalysts proved to be highly active and selective in cardanol metathesis and cardanol cross-metathesis with ethene and cis-1,4-diacetoxy-2-butene (DAB). GII/SBA-15 was less active than ZC/SBA-15, however, Ru leaching was significantly lower for GII/SBA-15 (0.5%) than for ZC/SBA-15 (2.5%). In ethenolysis of cardanol, 3-(non-8-enyl)phenol was isolated as a major product. In cross-metathesis with DAB 9-(3-hydroxyphenyl)non-2-enyl acetate and non-2-enyl acetate were formed with high selectivity. Easy catalyst product separation and low Ru leaching provide the products (applicable as detergent precursors and fragrance and flavor agents) free from the catalyst residue.
    Applied Catalysis A General 05/2014; 478:138–145. DOI:10.1016/j.apcata.2014.03.036 · 3.67 Impact Factor
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    ABSTRACT: Spontaneous catalyst‐free polymerizations of 4‐ethynylpyridine (4EPy) and 2‐ethynylpyridine with bifunctional quaternizing agents (QAs) of bis(bromomethyl)arenes provide highly crosslinked polymer networks in high yields. 13C cross‐polarization magic‐angle spinning (CP/MAS) NMR, Fourier transform IR (FTIR) and diffuse reflectance vis spectroscopy confirm that these networks consist of polyacetylene main chains substituted with pyridyl and pyridiniumyl groups, the latter interconnected with –CH2(arylene)CH2– linkers. Variation of the 4EPy/QA ratio in the polymerization feed results in networks with different extents of crosslinking and pyridyl/pyridin­iumyl ratio (N/N+ from 0 to 1.32). Networks exhibit photolumi­nescence and are also moderately active in CO2 capture (the highest uptake is 16.4 cm3 (STP) g−1 at 293 K and an equilibrium CO2 pressure of 750 Torr).
    Macromolecular Chemistry and Physics 12/2013; 214(24). DOI:10.1002/macp.201300540 · 2.45 Impact Factor
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    ABSTRACT: New heterogeneous, reusable catalysts for olefin metathesis have been prepared by immobilizing the Hoveyda-Grubbs first generation type alkylidene (commercially available as the Zhan catalyst-1C) on siliceous mesoporous molecular sieves with different pore sizes and architectures (SBA-15, SBA-16, MCM-41 and MCM-48) having the surface modified with molecules bearing dicyclohexylphosphine (PCy2) end groups. Resulting novel heterogenized catalysts proved high activity in ring-closing metathesis (RCM) of 1,7-octadiene, diethyl diallylmalonate, tert-butyl N,N-diallylcarbamate and N,N-diallyl-2,2,2-trifluoroacetamide, in homometathesis of 1-decene, 5-hexenyl acetate and methyl 10-undecenoate, and in cross-metathesis (CM) of allylbenzene with cis-1,4-diacetoxy-2-butene. The catalytic activity decreased with decreasing pore size of supports in the order SBA-15 > MCM-48 > SBA-16 and MCM-41. Filtration test suggested that the solid catalyst was responsible for the catalytic activity. Catalysts were easily separated from the reaction mixtures and products of low levels of Ru concentration were obtained. (c) 2013 Elsevier B.V. All rights reserved.
    Journal of Molecular Catalysis A Chemical 11/2013; 378:184-192. DOI:10.1016/j.molcata.2013.06.006 · 3.68 Impact Factor
  • Journal of Molecular Catalysis A Chemical 11/2013; 378:57-66. DOI:10.1016/j.molcata.2013.05.022 · 3.68 Impact Factor
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    ABSTRACT: Hyperbranched partly cross-linked polycyclotrimers of 1,4-diethynylbenzene, 2,6-diethynylnaphthalene, and 2,6-diethynylanthracene, Pc(1,4-DEB), Pc(2,6-DEN), and Pc(2,6-DEA), respectively, are prepared using TaCl5/Ph4Sn catalyst. Brunauer-Emmett-Teller (BET) surface area, microporosity, and maximum sorption capacity for H-2 and CO2 decrease in the order of decreasing relative content of branching points in polycyclotrimers Pc(1,4-DEB) > Pc(2,6-DEN) > Pc(2,6-DEA), the highest values for Pc(1,4-DEB) being S-BET = 1299 m(2)g(-1),a(H2) = 1.26 wt% (100 kPa, 77 K), and a(CO2) = 10.8 wt% (100 kPa, 273 K). N-2 isotherms show that adsorption/desorption hysteresis occurs already at low equilibrium pressures. CO2 isotherms show that the time allotted to the measurement influences both the maximum adsorption capacity and the hysteresis upon desorption.
    Macromolecular Chemistry and Physics 09/2013; 214(18). DOI:10.1002/macp.201300317 · 2.45 Impact Factor
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    ABSTRACT: Ruthenium complex 3b bearing chelating carboxylate ligand was immobilized on mesoporous molecular sieve SBA-15 via cleavage of carboxylate by fluorocarboxylic acid groups introduced on the support surface. The hybrid olefin metathesis catalyst Ru/L/SBA-15, prepared straightforward without use of silver salts, exhibited high activity and selectivity in model metathesis reactions and low ruthenium leaching.
    Catalysis Communications 05/2012; 21:42–45. DOI:10.1016/j.catcom.2012.01.020 · 3.32 Impact Factor
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    ABSTRACT: Microporous organic polymers (MOP) of a new type have been synthesised in high yields by a simple coordination polymerization of 1,3-diethynylbenzene, 1,4-diethynylbenzene and 4,4'-diethynylbiphenyl catalysed by [Rh(cod)acac] and [Rh(nbd)acac] complexes. The new MOPs are non-swellable polyacetylene-type conjugated networks consisting of ethynylaryl-substituted polyene main chains that are crosslinked by arylene linkers. Prepared MOP samples have a mole fraction of branching units (by (13) C CP/MAS NMR) from 0.30 to 0.47 and exhibit the BET (Brunaer-Emmett-Teller) surface up to 809 m(2) g(-1) and hydrogen uptake up to 0.69 wt% (77 K, H(2) pressure 750 torr).
    Macromolecular Rapid Communications 01/2012; 33(2). DOI:10.1002/marc.201100599 · 4.61 Impact Factor
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    ABSTRACT: New hybrid olefin metathesis catalysts were prepared by immobilization of Hoveyda–Grubbs type catalyst (commercially available as Zhan catalyst-1B) on the surface of mesoporous molecular sieves differing in pore size and architecture (MCM-41, MCM-48, and SBA-15) and conventional silica for a comparison. The activity of these catalysts was tested in RCM of (−)-β-citronellene, metathesis of 1-decene, ADMET of 1,9-decadiene, and in ROMP of cyclooctene and was found to increase significantly with the increasing pore size of the supports used. In all reactions, the activity of hybrid catalysts based on mesoporous molecular sieves was higher than that of catalyst using conventional silica as a support. In ROMP of cyclooctene, high molecular weight polymer (Mw=300,000) in high yield (70–80%) was obtained with catalysts based on mesoporous supports, however, only 40% polymer yield was obtained using catalyst based on conventional silica.
    Catalysis Today 01/2012; 179(1). DOI:10.1016/j.cattod.2011.06.012 · 3.31 Impact Factor
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    ABSTRACT: Hybrid catalysts for olefin metathesis were prepared by the immobilization of Ru alkylidenes (Grubbs catalysts) on mesoporous molecular sieves SBA-15 and MCM-41 having the surface modified with molecules bearing dicyclohexylphosphine (PCy2) and pyridine end groups. Hybrid catalysts with Ru attached to the surface via PCy2 ligands exhibited higher activity and stability than those with Ru attached via pyridine ligands. The former catalysts exhibited a high activity in a series of metathesis reactions (RCM, ROMP, and cross-metathesis) reaching turnover numbers (TONs) from 200 to 2000 and being reusable several times. The filtration tests for all catalysts suggested that the solid catalysts were responsible for catalytic activity during the reactions. Only low Ru leaching was observed. A positive effect of the pore size of the support on catalyst activity was observed for the metathesis of methyl oleate.
    ACS Catalysis 05/2011; 1(7):709–718. DOI:10.1021/cs200090e · 7.57 Impact Factor
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    ABSTRACT: Substituted polyvinylenes, polymers with conjugated polyene main chains, attract attention because of their unique properties implicating applications in electronics and optics [1] (electro- and photoconductivity, electro- and photoluminescence, optic non-linearity). So far, these polymers have been prepared almost exclusively by homogeneously catalyzed polymerization of corresponding substituted acetylenes with transition metal catalysts (most frequently compounds of W, Mo, Rh and Pd) [2–4]. However, catalyst residues in polymers may undesirably affect the polymer properties (especially those essential for their applications) and polymer purification (e.g. by repeated polymer precipitation) leads often to the decrease of molecular weight and changes in microstructure resulting from polymer degradation [5,6]. Therefore, new polymerization procedures minimizing the content of catalyst residues in the resulting polymers can be of important advantage.
    03/2011: pages 155-165;
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    ABSTRACT: A commercially available Hoveyda-Grubbs type catalyst (RC303 Zhannan Pharma) was immobilized on mesoporous molecular sieves MCM-41 and on SBA-15 by direct interaction with the sieve wall surface. The immobilized catalysts exhibited high activity and nearly 100% selectivity in several types of alkene metathesis reactions. Ru leaching was found to depend on the substrate and solvent used (the lowest leaching was found for ring-closing metathesis of 1,7-octadiene in cyclohexane - 0.04% of catalyst Ru content). Results of XPS, UV-vis and NMR spectroscopy showed that at least 76% of the Ru content was bound to the support surface non-covalently and could be removed from the catalyst by washing with THF.
    Beilstein Journal of Organic Chemistry 01/2011; 7:22-8. DOI:10.3762/bjoc.7.4 · 2.80 Impact Factor
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    ABSTRACT: New heterogeneous catalysts for ring opening metathesis polymerization (ROMP) have been prepared by immobilization of RuCl2(p-cymene)(PCy3) (Cy=cyclohexyl) on silica and siliceous mesoporous molecular sieves SBA-15 and MCM-41. Activity of these catalysts was investigated in ROMP of norbornene (NBE) and its derivatives (dicyclopentadiene, 5-norbornene-2-yl acetate). High molecular weight polymers (Mw up to 400000) were prepared in yields up to 80% using catalysts based on mesoporous sieves. In contrast, with catalyst based on conventional silica the yield did not exceed 28% (ROMP of NBE). Filtration test proved that the catalytic activity was bound to the solid phase. Catalysts could be easily separated from the reaction mixture in contrast to the corresponding homogeneous system. Therefore, polymers with reduced amounts of catalyst residues were obtained.
    Journal of Molecular Catalysis A Chemical 11/2010; 332(1-2):19-24. DOI:10.1016/j.molcata.2010.08.012 · 3.68 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 07/2010; 31(28). DOI:10.1002/chin.200028025
  • Hynek Balcar, Jiří Čejka
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    ABSTRACT: Siliceous mesoporous molecular sieves MCM-41, MCM-48 and SBA-15 and organised mesoporous alumina represent progressive supports for new heterogeneous catalysts for olefin metathesis and metathesis polymerization. In combination with Mo and Re oxides they provide catalysts of considerably higher activity in comparison with those based on conventional silica and alumina. Immobilization of Mo and Ru alkylidenes on these materials led to the highly active and selective catalysts with negligible leaching of transition metal.
    Macromolecular Symposia 07/2010; 293(1):43 - 47. DOI:10.1002/masy.200900043
  • David Bek, Hynek Balcar, Jan Sedlácek
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    ABSTRACT: A new heterogeneous catalyst for ring opening metathesis polymerization (ROMP) has been prepared by immobilization of [RuCl2(p-cymene)]2 on siliceous mesoporous molecular sieves SBA-15. Activity of the catalyst was tested in ROMP of norbornene. Filtration test proved that the catalytic activity is bound to the solid phase. Catalyst could be easily separated from reaction mixture in contrast to the corresponding homogeneous system and therefore polymer with reduced amounts of catalyst residues was obtained.
    NATO Security through Science Series A: Chemistry and Biology 01/2010; DOI:10.1007/978-90-481-3433-5_25
  • Hynek Balcar, Jiří Čejka
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    ABSTRACT: Heterogeneous catalysts for olefin metathesis using different types of (i) siliceous mesoporous molecular sieves, and (ii) organized mesoporous alumina as supports are reported. The catalysts were prepared either by spreading of transition metal oxidic phase on the support surface or by immobilizing transition metal compounds (mostly organometallic) on the support. The activity of these catalysts in various types of metathesis reactions (i.e. alkene and diene metathesis, metathesis of unsaturated esters and ethers, RCM, ROMP and metathesis polymerization of alkynes) was described. The main advantages of these catalysts consist generally in their high activity and selectivity, easy separation of catalysts from reaction products and the preparation of products free of catalyst residue. The examples of pore size influence on the selectivity in metathesis reactions are also given.
    12/2009: pages 101-114;
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    ABSTRACT: New heterogeneous catalysts for alkene metathesis were prepared by immobilization of molybdenum dioxide bis(acetylacetonate) and molybdenum dioxide bis(glycolate) on mesoporous molecular sieve SBA-15. Thermal spreading (TS) method and wet impregnation (WI) followed by calcinations were employed as synthesis approaches. These new catalysts represent inexpensive, easy-to-prepare and highly active and selective heterogeneous catalysts for metathesis of higher linear 1-alkenes applicable under mild reaction conditions without the necessity of solvent or co-catalyst in the reaction mixture. In metathesis of 1-octene, these catalysts showed up to four times higher activity compared with MoO3 supported on conventional silica as well as on SBA-15. This is probably due to the better dispersion of the molybdenum oxide phase on the mesoporous support surface. In metathesis of 1-dodecene and 1-tetradecene these catalysts based on SBA-15 exhibited a significantly higher activity than corresponding catalysts on MCM-41, probably due to the larger pores.
    Applied Catalysis A General 05/2009; 359(1-2):129-135. DOI:10.1016/j.apcata.2009.02.037 · 3.67 Impact Factor

Publication Stats

426 Citations
150.62 Total Impact Points

Institutions

  • 1994–2014
    • Academy of Sciences of the Czech Republic
      • J. Heyrovský Institute of Physical Chemistry
      Praha, Praha, Czech Republic
  • 2010–2013
    • The Police Academy of the Czech Republic in Prague
      Praha, Praha, Czech Republic
  • 1999
    • Université de Rennes 1
      • UMR CNRS 6118 - Géosciences Rennes
      Roazhon, Brittany, France
  • 1995–1998
    • Charles University in Prague
      • Department of Physical and Macromolecular Chemistry
      Praha, Praha, Czech Republic