Catalytic Hydrogenation Of 1-hexene Research Articles

Generation and Stabilization of Small Platinum Clusters Pt12±x Inside a Metal-Organic Framework.

The generation and matrix stabilization of ligand-free, small platinum nanoclusters (NCs) Pt12±x is presented. The metal-organic framework-template approach is based on encapsulating CO-ligated, atom-precise Pt9 Chini clusters [{Pt3(CO)6}3]2- into the zeolitic imidazolate framework ZIF-8. The selective formation of the air-stable inclusion compound [NBu4]2[{Pt3(CO)6}4]@ZIF-8 of defined atomicity Pt12 and with Pt loadings of 1-20 wt % was monitored by UV/vis and IR spectroscopy and was confirmed by high-resolution transmission electron microscopy (HR-TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (PXRD). Thermally induced decarbonylation at 200 °C yields the composite material Ptn@ZIF-8 with a cluster atomicity n close to 12, irrespective of the Pt loading. The PtNCs retain their size even during annealing at 300 °C for 24 h and during catalytic hydrogenation of 1-hexene at 25 °C in the liquid phase. The Ptn@ZIF-8 material can conveniently be used for storing small PtNCs and their further processing. Removal of the protective ZIF-8 matrix under acidic conditions and transfer of the PtNCs to carbon substrates yields defined aggregation to small Pt nanoparticles (1.14 ± 0.35 nm, HR-TEM), which have previously shown exceptional performance in the electrocatalytic oxygen reduction reaction (ORR).

Enhanced Hydrothermal Stability of γ-Al2O3 Catalyst Supports with Alkyl Phosphonate Coatings.

In this study, monolayers formed from organophosphonic acids were employed to stabilize porous γ-Al2O3, both as a single component and as a support for Pt nanoparticle catalysts, during exposure to hydrothermal conditions. To provide a baseline, structural changes of uncoated γ-Al2O3 catalysts under model aqueous phase reforming conditions (liquid water at 200 °C and autogenic pressure) were examined over the course of 20 h. These changes were characterized by X-ray diffraction, NMR spectroscopy, N2 physisorption, and IR spectroscopy. It was demonstrated that γ-alumina was rapidly converted into a hydrated boehmite (AlOOH) phase with significantly decreased surface area. Deposition of alkyl phosphonate groups on γ-alumina drastically inhibited the formation of boehmite, thereby maintaining its high specific surface area over 20 h of treatment. 27Al MAS NMR spectra demonstrated that hydrothermal stability increased with alkyl tail length despite lower P coverages. Although the inhibition of boehmite formation by the phosphonic acids was attributed primarily to the formation of Al2O3-PO x bonds, it was found that use of longer-chain octadecylphosphonic acids led to the most pronounced effect. Phosphonate coatings on Pt/γ-Al2O3 improved stability without adversely affecting the rate of a model reaction, catalytic hydrogenation of 1-hexene.

A Synthetic Route to a New Surface-Active Phosphine Ligand: 12-DPDP (12-Diphenylphosphinododecylphosphonate)

A water-soluble phosphonate-functionalized phosphine ligand Na 2[Ph 2P(CH 2) 12PO 3] ( 8), was prepared in eight steps from cyclododecanone. Phosphine 8 reacts with [Rh(COD)Cl] 2 in methanol to give the new complex Na 2[Rh(COD)(Ph 2P(CH 2) 12PO 3)Cl] ( 9). Complex 9 is inactive in the catalytic hydrogenation of 1-hexene and cyclohexene due to the decomposition of 9 to rhodium metal in the presence of hydrogen gas. Hydrogenation of decene using [Rh(COD) 2]BF 4 and 3 equiv. of 8 in an aqueous emulsion was achieved using 1 atm H 2. 31P NMR studies on 8 suggest a lack of well-defined aggregation in water, which has been ascribed to the steric bulk of the diphenylphosphino group.

Dicyclopentadienyl-titanium and -zirconium complexes as catalysts for hydrogenation of olefins

The catalytic hydrogenation of 1-hexene, 4-methyl-2-pentene (65% cis), cyclohexene, styrene, isoprene, 1,3-cyclooctadiene and 1,5-cyclooctadiene has been studied by using different metallocene-type complexes of stoichiometry [Cp 2MX 2], (M  Ti or Zr), containing equivalent, mixed ansa and bridging cyclopentadienyl ligands. The dichloro complexes (X  Cl) were reduced previously with an excess of magnesium, activated by the addition of a small amount of HgCl 2, in the presence or absence of PMePh 2. Cyclohexane solutions of the dialkyl derivatives (X Me, CH 2SiMe 3, CH 2PPh 2, CH 2Ph, Ph, p-MeC 6H 4 or PPh 2) were used in reactions generally carried out in dihydrogen at 7 bar pressure and 90°C, with a concentration of catalyst of around 10 −3 M and an olefin-to-catalyst molar ratio of between 300 and 500. The isolation and structural characterization of the new complexes [Ti(η 5-C 5H 5)(η 5-C 5Me 5)Cl(CH 2PPh 2)], [Ti(η 5- C 5H 5)(η 5-C 5Me 5)( p-MeC 6H 4)] 2], [Ti{μ 2-η 5-η 5-(C 5H 4) 2SiMe 2}(CH 2PPh 2) 2] and [Ti(η 5-C 5Me 5)(η 5-C 5H 4CH 2CH 2PPh 2)Cl 2] are also reported.

Competitive hydrogenation of binary olefin mixtures in the liquid phase

The effect of a series of alcohol solvents on the selectivity of the competitive catalytic hydrogenation of 1-hexene and 2-methyl-3-butene-2-ol on Pt/SiO2 catalyst has been investigated. With increasing molecular mass of the alcohol, the rate of hydrogenation of 1-hexene becomes relatively preferred; the same was observed also with branched alcohols compared with those having a straight chain. Systems were found in which the degree of coating of the platinum catalyst with copper affected (or did not affect) the selectivity of the competitive hydrogenation of pairs of olefinic substrates.

Catalytic hydrogenation of 1-hexene by rhodium complexes in the intracrystal space of a swelling layer lattice silicate

Catalytic hydrogenation of 1-hexene by rhodium complexes in the intracrystal space of a swelling layer lattice silicate

Zum Mechanismus der katalytischen Hydrierung von Maleinsäuredimethylester und 1-Hepten mit RhH(CO)(PΦ3)3 in Toluol / Mechanism of Catalytic Hydrogenation of Dimethyl-Maleate and 1-Heptene with RhH (CO) (ΡΦ3)3 in Toluene

In contrary to catalytic hydrogenation of 1-hexene and 1-decene with RhH (CO) (ΡΦ3) 3 in benzene in toluene as a solvent the reaction rate r can be represented by the equation 1/r=K/k1·[H2] · [M]0 · [M]0· [Κa]0+Ka]o+1/k1 · [H2] · [Ka]0, yet, only in a very small concentration range of substrate 1-heptene [=M]. However, if free ligand ΡΦ3, was added to the reaction mixture, formation of the more active catalyst RhH (CO) (ΡΦ3) 2 was supressed and r could be measured only for the catalyst RhH (CO) (ΡΦ3)3 s. In this case kinetic data can be represented by the equation 1/r proportional 1/[M]0.