Hydrogenation Of 1-hexene Research Articles

Effects of sulfur compounds on the hydrogenation and isomerization of 1-hexene over a sulfided CoMo catalyst for hydrodesulfurization

Effects of H2S and organic sulfides on the hydrogenation and isomerization of 1-hexene over a CoMo catalyst were systematically investigated.

Facile preparation of ZIF-8@Pd-CSS sandwich-type microspheres via in situ growth of ZIF-8 shells over Pd-loaded colloidal carbon spheres with aggregation-resistant and leach-proof properties for the Pd nanoparticles

Aiming to enhance the stability of noble metal nanoparticles that are anchored on the surface of colloidal carbon spheres (CCSs), we designed and prepared a new kind of sandwich-structured ZIF-8@Pd-CCS microsphere. Typically, uniform CCSs were first synthesized by the aromatization and carbonization of glucose under hydrothermal conditions. Subsequently, noble metal nanoparticles, herein Pd nanoparticles, were attached to the surface of CCSs via self-reduction route, followed by in situ assembly of a thin layer of ZIF-8 over the Pd nanoparticles to form the sandwich-type ZIF-8@Pd-CCS microspheres. X-ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) spectra confirmed the presence of crystalline ZIF-8, while TEM analysis revealed that the ZIF-8 shells were closely bound to the Pd-loaded CCSs. The shell thickness could be tuned by varying the ZIF-8 assembly cycles. Further, liquid-phase hydrogenation of 1-hexene as the probe reaction was carried out over the ZIF-8@Pd-CCS microspheres and results showed that the prepared microspheres exhibited excellent agglomeration-resistant and leach-proof properties for the Pd nanoparticles, thus leading to the good reusability of the ZIF-8@Pd-CCS microspheres.

Synthesis, characterization and hydrogenation catalysis in biphasic medium (organic/water) of samarium (III) complex with glycine and 2,2-bipyridine ligands

Sm(bipy)(glycine)3 [bipy = 2,2-bipyridine] was synthesized by classic, microwave and mechanical methods. UV-Vis reveals a strong signal near 190 nm corresponding to a high energy Sm-O bond and f→f transitions. FT-IR spectra show a band between 490 - 450 cm-1 indicative of a Sm-O bond. TGA-DTA and MS analytical analysis, confirm the structural proposals. The samarium (III) complex was tested in 1-hexene hydrogenation, in biphasic media (cyclohexane/water) and the reaction parameters were optimized (time, temperature, substrate/catalyst ratio and H2 pressure). Catalystshowed 37.5 % conversion.

Trisphosphine-chelate-substituted molybdenum and tungsten nitrosyl hydrides as highly active catalysts for olefin hydrogenations.

Reaction of [M(NO)Cl3 (NCMe)2 ] (M=Mo, W) with (iPr2 PCH2 CH2 )2 PPh (etp(i) p) at room temperature afforded the syn/anti-[M(NO)Cl3 (mer-etp(i) p)] complexes (M=Mo, a; W, b; 3 a,b(syn,anti); syn and anti refer to the relative position of Ph(etp(i) p) and NO). Reduction of 3 a,b(syn,anti) produced [M(NO)Cl2 (mer-etp(i) p)] (4 a,b(syn)), [M(NO)Cl(NCMe)(mer-etp(i) p)] (5 a,b(syn,anti)), and [M(NO)Cl(η(2) -ethylene)(mer-etp(i) p)] (6 a,b(syn,anti)) complexes. The hydrides [M(NO)H(η(2) -ethylene)(mer-etp(i) p)] (7 a,b(syn,anti)) were obtained from 6 a,b(syn,anti) using NaHBEt3 (75 °C, THF) or LiBH4 (80 °C, Et3 N), respectively. 7 a,b(syn,anti) were probed in olefin hydrogenations in the absence or presence of a hydrosilane/B(C6 F5 )3 mixture. The 7 a,b(syn,anti)/Et3 SiH/B(C6 F5 )3 co-catalytic systems were highly active in various olefin hydrogenations (60 bar H2 , 140 °C), with maximum TOFs of 5250 h(-1) (7 a(syn,anti)) and 8200 h(-1) (7 b(syn,anti)) for 1-hexene hydrogenation. The Et3 SiH/(B(C6 F5 )3 co-catalyst is anticipated to generate a [Et3 Si](+) cation attaching to the ONO atom. This facilitates NO bending and accelerates catalysis by providing a vacant site. Inverse DKIE effects were observed for the 7 a(syn,anti)/Et3 SiH/(B(C6 F5 )3 (kH /kD =0.55) and the 7 b(syn,anti)/Et3 SiH/(B(C6 F5 )3 (kH /kD =0.65) co-catalytic mixtures (20 bar H2 /D2 , 140 °C).

Pd nanoparticles immobilized in a microporous/mesoporous composite ZIF-8/MSS: A multifunctional catalyst for the hydrogenation of alkenes

The work reports a new hierarchically core–shell structure that consists of a catalytically active core made of palladium–decorated mesoporous silica spheres (Pd/MSS) and an outer shell of microporous ZIF-8. The synthesis process involves (i) the preparation of MSS via supramolecular templating using a modified Stöber method, (ii) the loading of palladium nanoparticles into MSS, followed by (iii) the surface modification of Pd/MSS catalyst with polyelectrolyte to promote the nucleation and growth of a ZIF-8 shell. The core–shell Pd/MSS@ZIF-8 was characterized by X-ray diffraction, electron microscopy (SEM & TEM), FTIR, ICP-AES and N2 physisorption to determine its physicochemical properties. The core–shell Pd/MSS@ZIF-8 was used to catalyze the hydrogenation of 1-hexene and cyclohexene. Results showed that the Pd/MSS@ZIF-8 was a multifunctional catalyst with excellent reactant shape-selectivity, leaching-proof ability, improved poison resistance and good recyclability in contrast to the conventional Pd/MSS catalyst.

Core–shell Pd/ZSM-5@ZIF-8 membrane micro-reactors with size selectivity properties for alkene hydrogenation

A well-designed Pd/ZSM-5@ZIF-8 core–shell structure has been prepared by application of a combination of seed-induction synthesis strategy and self-assembly synthesis techniques. First, uniform ZSM-5 particles with micron size and high crystallinity were prepared from organic-template-free gel systems containing 200nm ZSM-5 seeds and exchanged with Pd(NO3)2 aqueous solution. Then incompatibility between the Pd/ZSM-5 core material and ZIF-8 shell precursor was circumvented by surface modification using a layer by layer self-assembly of polyelectrolyte, followed by a subsequent two-step temperature synthesis process inducing the formation of continuous and well-intergrown ZIF-8 shell. Thickness of ZIF-8 shell can be simply tuned by monitoring the assembly cycles. Furthermore, hydrogenations of 1-hexene and cyclohexene were chosen as model reactions to evaluate the catalytic behavior of the Pd/ZSM-5@ZIF-8 core–shell architecture and tert-dodecylthiol was used as a poison to test its anti-poisoning ability. Results show that such core–shell architecture exhibits excellent poison resistance and selectivity control properties for the hydrogenation reactions and can be potentially used as a membrane reactor in the field of heterogeneous catalysis.

Ruthenium Carbene–Diether Ligand Complexes: Catalysts for Hydrogenation of Olefins

A series of carbene–diether ligands were prepared and the corresponding Ag salts used to prepare the complexes RuHCl(PPh3)2(Im(OR)2) (Im(OR)2 = C3H2(NCH2CH2OR)2; R = Me (4a), t-Bu (4b), tert-hexyl (4c), Ph (4d), 2,6-i-Pr2C6H3 (4e)). In an analogous fashion the species RuHCl(PPh3)2(Y2Im(OMe)2) (Y2Im(OMe)2 = Y2C3(NCH2CH2OMe)2; Y2 = C6H4 (4f), Y = Cl (4g), Me (4h)) were also synthesized. Similarly RuHCl(CO)(PPh3)2(Im(OMe)2) (5) was prepared and readily converted to RuHCl(CO)(SIMes)(Im(OMe)2) (6) via treatment with SIMes. The reaction of 4a with SIMes afforded RuHCl(SIMes)(Im(OMe)2)(PPh3) (7), which reacts subsequently with Na[BPh4] to give [RuH(Im(OMe)2)(SIMes)][(η6-Ph)BPh3] (8). In a series of tests, the species 4a–h, 5, 6, and 8 were shown to catalyze the hydrogenations of 1-hexene, cyclohexene, and dimethyl itaconate. From the activity of 4a–h it is clear that the capability of the carbene–ether substituents to coordinate to the metal as well as electron-donating substituents on the carbene fragment enhan...

Polyoxotungstate stabilized palladium, gold, and silver nanoclusters: A study of cluster stability, catalysis, and effects of the stabilizing anions

Polyoxometalates (POMs) have demonstrated the unusual ability to both stabilize nanoclusters and facilitate catalytic activity by allowing substrate access to sufficient metallic surface area. This paper presents a wet chemical synthetic method to prepare Pd, Ag, and Au metal nanoclusters stabilized by tetrabutylammonium salts of Phosphotungstates with the well-known Keggin [α-PW12O40]3− (PW12), Wells–Dawson [P2W18O62]6− (P2W18), and their lacunary derivatives [α-PW11O39]7− (PW11) and [P2W15O56]12− (P2W15) structures. The preparation of this series of nanoclusters has facilitated a comparison of the effect these anions have in nanocluster stabilization and catalysis. The nanocluster systems were found to be re-dispersible in acetonitrile and acetone. The effect of aging on stability was followed over 3months and it was found that many systems were very stable for more than 70days without precipitation, depending on type of polytungstate stabilizer and the presence of competing ions. The PW12, P2W18, PW11, and P2W15 stabilized Pd nanoclusters have been investigated for catalytic activity in the hydrogenation of 1-hexene and were found to be very active with the P2W18 stabilized Pd nanoclusters demonstrating a best of 139,000 Total Turnovers, thus ranking this “soluble heterogeneous catalyst” among one of the longest lived reported in the literature. The nanocluster systems were characterized using instrumental techniques such as UV–Visible Spectroscopy, FTIR Spectroscopy, Powder X-ray Diffraction, Energy Dispersive Spectroscopy, X-ray Photoelectron Spectroscopy, and Transmission Electron Microscopy.

Catalytic activity of a supported palladium–benzimidazole complex toward alkene hydrogenation

A polymer anchored palladium complex was synthesized by sequential attachment of benzimidazole and palladium chloride to chloromethylated polystyrene divinyl benzene co-polymer with 6.5 % cross-linking. The product was characterized by XPS, UV–vis. spectrophotometry, FTIR and TGA. Various physico-chemical properties such as bulk density, surface area and swelling behavior in different solvents were also measured. The polymer anchored complex was tested as a catalyst for reduction of olefins. The kinetics of hydrogenation of 1-hexene was studied by varying the temperature, catalyst concentration and substrate concentration. The energy and entropy of activation were evaluated from the kinetic data. The catalyst could be recycled a number of times and no leaching of metal from the catalyst surface was observed.

Stabilisation of water-soluble platinum nanoparticles by phosphonic acid derivatives

Sodium 2-(diphenylphosphino)ethyl phosphonate (1) was investigated as a stabilising agent for platinum nanoparticles (Pt-NPs) in aqueous solution. This phosphino phosphonate is known to stabilise rhodium nanoparticles (NPs) in water. Here we report that in the case of Pt-NPs this ligand is indirectly involved in the stabilisation mechanism and the actual stabilisation agent is the platinum complex Na(2)[Pt(1)(2)] (2). The reduction of platinum(II) salts in the presence of the phosphonates 1, 2, sodium 2-(diphenylphosphoryl)ethyl phosphonate (3) and 3,3,3-triphenylpropyl phosphonate (4) leads to stable platinum NPs with a remarkably narrow particle size distribution. These platinum NPs show high catalytic activity in the hydrogenation of 1-hexene and 1-chloro-3-nitrobenzene under biphasic as well as heterogeneous (supported on charcoal) conditions. The activity of the supported NPs was 30 times higher than the commercially available catalyst Pt(0) EnCat®. Furthermore, the single-crystal X-ray structures of (1)(MeOH)(2)(H(2)O)(2), (3)(H(2)O)(4), and (4)(2)(H(2)O)(17) have been determined.

The hydrogenation of alkenes on Pd- blacken in a universal buffer solution under hydrogen pressure

Discussed the basic mechanisms and kinetics of the hydrogenation of 1-hexene, heptene-1 and cyclohexene in the presence of Pd-mob at different pH values and hydrogen pressure. It is shown that, depending on the chemical structure of hydrogenated compounds, pH and the hydrogen pressure in the hydrogenation reaction involved hydrogen, which has a different strength of bonding with the catalyst.

Synthesis, characterization, and biphasic ionic liquid media 1-hexene hydrogenation reaction of RuCl2(DMSO)2(NC5H4CO2Na-3)2

RuCl2(DMSO)2(NC5H4CO2Na-3)2 is very soluble in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium tetrafluoroborate, [(BMIM)BF4]. The complex was prepared by reacting RuCl2(DMSO)4 with NC5H4CO2Na-3, sodium nicotinate, in toluene, and was characterized by spectroscopic methods. The complex catalyzes the hydrogenation of 1-hexene (600 psi H2, 100 °C) in a two-phase system consisting of cyclohexane/[(BMIM)BF4] with 75% conversion in 24 h and modest substrate isomerization. The complex shows good stability and can be reused several times with little loss in activity.

Anchored Wilkinson Catalyst

A series of Anchored Wilkinson’s Catalysts were prepared by the reaction of the homogeneous Wilkinson catalyst with alumina/heteropoly acid support materials. It was found that the catalytically active species from these materials were unique in that they had only a single triphenylphosphine and a heteropoly acid as ligands giving these catalysts distinctive steric and electronic characteristics. These catalysts were used to promote the hydrogenation of 1-hexene and limonene with substrate to catalyst ratios of 10,000 and 7,500 respectively. The results were compared with those obtained using the homogeneous Wilkinson and 1% Rh/Al2O3 catalysts with respect to catalyst activity and stability as well as the reaction selectivity as measured by the amount of double bond isomerization observed. The observed rates of hydrogen uptake and double bond isomer formation in the hydrogenations of both 1-hexene and limonene follow the same order with respect to the nature of the heteropoly acid ligand used to anchor the Wilkinson catalyst to the alumina: silicotungstic acid > phosphotungstic acid > phosphomolybdic acid > silicomolybdic acid for hydrogen addition and the reverse for isomerization. This consistency provides a measure of the electronic character of these Keggin heteropoly acids when acting as ligands. In contrast to the reactions observed with the anchored catalysts the homogeneous Wilkinson catalyst was incapable of completing these high substrate/catalyst ratio hydrogenations. It became deactivated at about 85% 1-hexene conversion and only 10% limonene hydrogenation. As compared with the anchored catalysts the supported Rh promoted more isomerization of 1-hexene and limonene while the hydrogenation of the trisubstituted double bond in p-menthene was more difficult over the supported metal catalyst than with the sterically more accessible anchored Wilkinson catalysts.

Rhenium Hydride/Boron Lewis Acid Cocatalysis of Alkene Hydrogenations: Activities Comparable to Those of Precious Metal Systems

Dibromonitrosyl(dihydrogen)rhenium(I) complexes [ReBr(2)(NO)(PR(3))(2)(η(2)-H(2))] (1; R = iPr, a; Cy, b) and Me(2)NH·BH(3) (DMAB) catalyze at either 90 °C or ambient temperature under 10 bar of H(2) the hydrogenation of various terminal and cyclic alkenes (1-hexene, 1-octene, cyclooctene, styrene, 1,5-cyclooctadiene, 1,7-octadiene, α-methylstyrene). Maximum turnover frequency (TOF) values of 3.6 × 10(4) h(-1) at 90 °C and 1.7 × 10(4) h(-1) at 23 °C were achieved in the hydrogenation of 1-hexene. The extraordinary catalytic performance of the 1/DMAB system is attributed to the formation of five-coordinate rhenium(I) hydride complexes [Re(Br)(H)(NO)(PR(3))(2)] (2; R = iPr, a; Cy, b) and the action of the Lewis acid BH(3) originating from DMAB. The related 2/BH(3)·THF catalytic system also exhibits under the same conditions high activity in the hydrogenation of various alkenes with a maximum turnover number (TON) of 1.2 × 10(4) and a maximum TOF of 4.0 × 10(4) h(-1). For the hydrogenations of 1-hexene with 2a and 2b, the effect of the strength of the boron Lewis acid was studied, the acidity being in the following order: BCl(3) > BH(3) > BEt(3) ≈ BF(3) > B(C(6)F(5))(3) > BPh(3) ≫ B(OMe)(3). The order in catalytic activity was found to be B(C(6)F(5))(3) > BEt(3) ≈ BH(3)·THF > BPh(3) ≫ BF(3)·OEt(2) > B(OMe)(3) ≫ BCl(3). The stability of the catalytic systems was checked via TON vs time plots, which revealed the boron Lewis acids to cause an approximate inverse order with the Lewis acid strength: BPh(3) > BEt(3) ≈ BH(3)·THF > B(C(6)F(5))(3). For the 2a/BPh(3) system a maximum TON of 3.1 × 10(4) and for the 2a/B(C(6)F(5))(3) system a maximum TOF of 5.6 × 10(4) h(-1) were obtained in the hydrogenation of 1-hexene. On the basis of kinetic isotope effect determinations, H(2)/D(2) scrambling, halide exchange experiments, Lewis acid variations, and isomerization of terminal alkenes, an Osborn-type catalytic cycle is proposed with olefin before H(2) addition. The active rhenium(I) monohydride species is assumed to be formed via reversible bromide abstraction with the "cocatalytic" Lewis acid. Homogeneity of the hydrogenations was tested with filtration and mercury poisoning experiments. These "rhenium(I) hydride/boron Lewis acid" systems demonstrate catalytic activities comparable to those of Wilkinson- or Schrock-Osborn-type hydrogenations accomplished with precious metal catalysts.

Improvement in the Durability of Carbon Nanotube-Supported Ruthenium Catalysts by Coverage with Silica Layers

Abstract Carbon nanotube-supported Ru (Ru/CNT) catalysts were covered with silica layers to inhibit the aggregation of Ru particles as well as the detachment of Ru particles from the CNTs during catalytic reactions. Coverage of the Ru/CNT with silica was performed by the successive hydrolysis of 3-aminopropyltriethoxysilane and tetraethoxysilane in the presence of CNT-supported Ru metal precursors, followed by reduction with hydrogen at 623 K. The diameter of the Ru particles in the silica-coated Ru/CNT ranged from 1 to 3 nm. The Ru particles and the CNTs in the silica-coated catalysts were uniformly covered with silica layers a few nanometers thick. The size of the Ru particles in the silica-coated catalysts did not change appreciably after treatment at 873 K, while the metal particles in the Ru/CNT were seriously aggregated after treatment at 873 K. The silica-coated Ru/CNT catalyzed the CO hydrogenation and the 1-hexene hydrogenation, despite the coverage of Ru particles with silica. In addition, the silica-coated Ru catalysts showed high durability toward Ru detachment from the CNTs during the repeated hydrogenation of 1-hexene, whereas the catalysts without silica layers were deactivated because of Ru detachment. Therefore, coverage of the Ru/CNT catalysts with silica layers prevented the deactivation of the catalysts.

Influence of Bubble Evolution on the Effective Kinetics of Heterogeneously Catalyzed Gas/Liquid Reactions. Part I: Reactions with Gaseous Products

AbstractFor heterogeneously catalyzed multiphase reactions the formation of bubbles may have an influence on mass and heat transfer as well as on the effective reaction rate. This first of two contributions deals with the Ni‐catalyzed decomposition of H2O2, which was used as a model system for an (almost) isothermal reaction with a gaseous product. (In part II the strongly exothermic hydrogenation of hexene will be analyzed, where gas/vapor bubbles may be generated by overheating of the catalyst.) The discharge of O2 bubbles formed by decomposition of H2O2 enhances the external mass and heat transfer up to one order of magnitude. This is in analogy to the well‐known phenomena during nucleate boiling. The experiments and theoretical considerations also show that the internal mass transfer depends on the intensity of the reaction and thus on the H2O2 concentration, which is in contradiction to the classical Thiele approach. This discrepancy could be explained by a modified model that takes the formation of bubbles into account.

Influence of Bubble Evolution on the Effective Kinetics of Heterogeneously Catalyzed Gas/Liquid Reactions. Part II: Exothermic Gas/Liquid Reactions

AbstractFor heterogeneously catalyzed multiphase reactions the formation of bubbles may have an influence on the effective reaction rate. This second of a series of two contributions deals with the Ni‐catalyzed hydrogenation of hexene, which was used as a model system for an exothermic gas/liquid (G/L) reaction, where gas/vapor bubbles may be generated by overheating of the catalyst. (In part I, results of catalytic H2O2 decomposition were presented, where the evolution of gas bubbles (O2) always occurs.) A criterion for the formation of vapor bubbles for exothermic G/L reactions is presented, which was verified by experiments in a reactor with an inspection window. For a particle diameter of 6 mm, the effective kinetics of hexene hydrogenation is influenced by internal and external mass and heat transfer. A new and simple method to estimate the mass and heat transfer parameters and the effectiveness factors with regard to pore and external diffusion is presented, which combines the measured temperature difference(s) and the effective rate. For the given reaction conditions, the rate of hexene hydrogenation is not influenced by the evolution of vapor bubbles.

Hydrogenation of unsaturated hydrocarbons catalyzed by homogeneous and supported Rh, Rh-Co, and Pd, Pd-Ni complexes with oligomeric allene ligands

Mono- and bimetallic Rh and Rh-Co complexes containing oligoallene ligands were synthesized. Their catalytic activity was examined in the hydrogenation of unsaturated compounds, such as isoprene, hexene-1, and toluene. The catalytic activity of Rh(DMA)ol and Rh-Co(DMA)ol was shown to be 16 800 and 23000 mol/(mol h) in the hydrogenation of hexene-1 and 72 and 90 mol/(mol h) in the hydrogenation of toluene, respectively. Isoprene is hydrogenated completely: the rate curves exhibit two portions corresponding to hydrogenation of both double bonds. The catalytic activity of palladium oligodimethylallene complexes deposited on an inorganic support (γ-Al2O3) in isoprene hydrogenation depends on the support preparation procedure, the particle size, and the metal loading on the surface. Heterogenization of the homogeneous mono- and bimetallic Rh and Pd complexes somewhat enhances the catalytic activity in hydrogenation of the given substrates.

Effect of 1-Hexene Volume Fraction on the Reaction between 1-Hexene and Hydrogen Sulfide with Hydrogen

The recombination reaction between H2S and 1-hexene with H2 was detected. The catalyst used was NiMoS/Al2O3 (presulfided); the volume fraction of 1-hexene in the model feedstock was 5, 10, 15, 20, 25 (vol%), respectively; H2S concentration was 4,000 μg/g; initial H2 pressure was 2 MPa; and reaction time and reaction temperature were 2 hr and 473 K, respectively. It was revealed that, in the reaction system, as the volume fraction of 1-hexene increased, the concentration of total sulfur in the reaction system first increased significantly and then was steady; the hexanethiol content in the product first increased and then decreased. The hydrogenation of 1-hexene was promoted as the 1-hexene volume fraction increased. As the 1-hexene volume fraction increased, the mass fraction of hexane in the product increased; the mass fraction of 2-hexene in the product first increased and then decreased; the mass fraction of 3-hexene in the reaction system first increased significantly and then was steady.

Synthesis, characterization, and application of PdPt and PdRh bimetallic nanoparticles encapsulated within amine-terminated poly(amidoamine) dendrimers

PdPt and PdRh bimetallic dendrimer-encapsulated nanoparticles (DENs) were first prepared within fourth-generation amine-terminated poly(amidoamine) dendrimers (G4-NH2) by a co-complexation route, which included both co-complexation of bimetallic ions with dendrimers in HCl aqueous solution at pH 3 and subsequent reduction of the bimetallic ions in composite. The dendrimer-encapsulated bimetallic ions and reduction courses were analyzed by UV–vis spectroscopy and X-ray photoelectron spectroscopy. High-resolution transmission electron microscopy was used to characterize the two types of bimetallic nanoparticle size, size distribution, and particle morphology. The resulting PdPt and PdRh DENs show promising catalytic activities for the hydrogenation of 1-hexene.