108-05-4

Nanostructured Pd?Cu Catalysts Supported on Zr?Al and Zr?Ti for Synthesis of Vinyl Acetate

Gonzalez Caranton, Alberth Renne,Dille, Jean,Barreto, Jade,Stavale, Fernando,Pinto, José Carlos,Schmal, Martin

, p. 5256 - 5269 (2018)

Renewable ethylene can be obtained by dehydration of bio-ethanol and used for production of vinyl acetate (VAM) through reaction with acetic acid (AcOH), using Pd?Cu catalysts. In the present manuscript, structural characterizations of Pd?Cu/ZrO2 catalysts show that these systems present cubic structure with different spatial distributions. Particularly, it is shown that combustion of ethylene and acetic acid can be inhibited below 180 °C, maximizing the rates of VAM formation, when the catalysts are modified with Ti+4. The effects of AcOH concentration on rates of VAM formation show that higher AcOH concentrations favor the formation of undesired byproducts, while lower AcOH concentrations favor effects related to O2 mobility, which can lead to surface decomposition. VAM formation is favored, with selectivities ranging from 0.8 to 1.0. XPS results indicate the existence of metallic Pd, CuO species and Zr species, in agreement with IR results. DRIFTS results also show that different Pd-acetate intermediates can be present, depending on the electronic effects associated to Pd?Cu and Zr species.

Monoatomically dispersed Pd/TiO2 catalyst effective for epoxidation of propylene at ambient temperature in the presence of H2 and O2

Hikazudani, Susumu,Mochida, Tatsuya,Matsuo, Naofumi,Nagaoka, Katsutoshi,Ishihara, Tatsumi,Kobayashi, Hisayoshi,Takita, Yusaku

, p. 89 - 98 (2012)

The catalytic activity of monoatomically dispersed Pd supported on TiO 2 toward propylene epoxidation in the presence of H2 and O2 was studied at ambient temperature, and both propylene oxide (PO) and propane were obtained. Short-chain alkanes also reacted but epoxide formation was not observed in those reactions except in the case of isobutane, which formed isobutylene oxide at a low rate. The optimum surface concentration of Pd on TiO2 was 0.005-0.01 atom/nm2; because the supported amount of Pd is extremely small relative to the surface area of the support, the supported Pd is thought to be monoatomically dispersed. Pd/TiO 2 catalysts prepared from a tetraphenylporphyrin-Pd chloride complex showed almost the same product distribution for propylene epoxidation as did catalysts prepared from Pd(NO3)2. Isotope exchange between H2 and D2 proceeded over Pd/TiO2 with a low surface concentration (0.0001 atom-Pd/nm2), and chemical potential calculations suggested that H2 molecules could dissociatively adsorb onto the monoatomically dispersed Pd/TiO2. A PO formation mechanism over the catalyst is proposed on the basis of these results. The results presented here may provide the first clear evidence of catalysis by monoatomically dispersed noble metals.

THE CATALYSIS OF THE ELECTROCHEMICAL REDUCTION OF ALKYL BROMIDES BY NICKEL COMPLEXES: THE FORMATION OF CARBON-CARBON BONDS

Gosden, Cary,Pletcher, Derek

, p. 401 - 409 (1980)

The square planar, macrocyclic nickel complex, N,N'-ethylenebis(salicylidene-iminato)nickel(II), is shown to be an effective catalyst for the electrochemical reduction of substituted alkyl bromides; this indirect cathodic reduction can lead to a good yield of dimeric products.The reduction of alkyl bromides in the presence of an activated olefin is shown to lead to mixtures of products compatible with radical addition to the double bond.The mechanism of the reaction of nickel(I) complexes with alkyl bromides is discussed in the light of these results.

Nakamura,Yasui

, p. 315,316, 317 (1971)

Dendrimer-stabilized bimetallic Pd/Au nanoparticles: Preparation, characterization and application to vinyl acetate synthesis

Kuhn, Martin,Jeschke, Janine,Schulze, Steffen,Hietschold, Michael,Lang, Heinrich,Schwarz, Thomas

, p. 78 - 82 (2014)

The preparation, characterization and a novel application to vinyl acetate synthesis of dendrimer-stabilized Pd/Au nanoparticles are described. The nanoparticles were synthesized by co-precipitation of aqueous Pd 2 +/Au3 + salt solutions with hydrazine in the presence of (poly)amidoamine (PAMAM)-based dendrimers functionalized with terminal ethylene glycol ethers. Characterization by transmission electron microscopy and UV-vis spectroscopy confirmed that alloyed Pd/Au nanoparticles with a mean diameter of 6.0 (± 1.2) to 10.4 (± 1.7) nm were formed. After nanoparticle immobilization onto a silica support and thermal dendrimer removal, the resulting materials are high active catalysts in ethylene acetoxylation to vinyl acetate monomer with a productivity of 2.1 kgVAM kg cat- 1 h- 1.

Nanosized {Pd4(μ4-C)}Pd32(CO)28(PMe3)14 Containing Tetrahedrally Deformed Pd4 Cage with Encapsulated Carbide Atom: Formal Substitution of Geometrically Analogous Interior Au4 Entity in Isostructural Au4Pd32(CO)28(PMe3)14 by Electronically Equivalent Pd4(μ4-C) and Computational/Catalytic Implications

Mednikov, Evgueni G.,Ivanov, Sergei A.,Dahl, Lawrence F.

, p. 6157 - 6168 (2015)

This first homopalladium carbido cluster, {Pd04(μ4-C)}Pd32(CO)28(PMe3)14 (1), was isolated (3-7% yields) from an ultimately simplified procedure - the reaction of CHCl3 under N2 with either Pd8(CO)8(PMe3)7 or Pd10(CO)12(PMe3)6 at room temperature. Charge-coupled device (CCD) X-ray diffraction data at 100 K for 1·2.5 C6H14 (1a) and 1·3 CHCl3 (1b) produced closely related molecular parameters for 1. This {Pd4C}Pd32 cluster (1) possesses a highly unusual tetracoordinated carbide atom that causes a major distortion of a central regular Pd4 tetrahedron into a new symmetry type of encapsulated Pd4 cage of pseudo-D2 (222) symmetry. Mean Pd-Pd distances for the three pairs of opposite twofold-equivalent Pd-Pd tetrahedral-like edges for 1a are 2.71, 2.96, and 3.59 ?; the mean of the four Pd-C distances [range, 1.87(2)-1.94(2) ?] is 1.91 ?. An astonishing molecular feature is that this {Pd4C}Pd32 cluster (1) is an isostructural and electronically equivalent analogue of the nanosized Au4Pd32(CO)28(PMe3)14 (2). Cluster 2, likewise a pseudo-D2 molecule, contains a geometrically analogous tetrahedrally deformed interior Au4 entity encapsulated within an identical Pd32(CO)28(PMe3)14 shell; mean distances for the three corresponding symmetry-equivalent pairs of slightly smaller opposite tetrahedral-distorted Au-Au edges are 2.64, 2.90, and 3.51 ?. A computational study by both a natural population analysis (NPA) and an atoms-in-molecules (AIM) method performed on model analogues {Pd4C}Pd32(CO)28(PH3)14 (1-mod) and Au4Pd32(CO)28(PH3)14 (2-mod) suggested that the negatively charged Au4 entity in 2-mod may be described as two weakly interacting electron-pair Au2 intradimers. In contrast, an NPA of the {Pd4C} entity in 1-mod revealed that two similarly oriented identical Pd2 intradimers of 2.71 ? are primarily stabilized by Pd-C bonding with a negatively charged carbide atom. The isostructural stabilizations of 1 and 2 are then attributed to the similar sizes, shapes, and overall negative charge distributions of the electronically equivalent interior {Pd4C} and Au4 entities. This resulting remarkable structural/electronic equivalency between 1 and 2 is consistent with the greatly improved performances of commercial palladium catalysts for vinyl acetate synthesis by gold-atom incorporation to suppress carbonization of the Pd atoms, namely, that the extra Au 6s1 valence electron of each added Au atom provides an effective "negative charge protection" against electron-donating carbon atoms forming Pd carbido species such as {Pd4C}. (Figure Presented).

Neuartige basische Liganden fuer die homogenkatalytische Methanolcarbonylierung XXIX. Kieselgelfixierte (Ether-Phosphan)Rhodium-Komplexe in der katalytischen Hydrocarbonylierung von Methylacetat zu Ethylidendiacetat

Lindner, Ekkehard,Glaser, Erhard,Mayer, Hermann August,Wagner, Peter

, p. 325 - 337 (1990)

The heterogenized (ether-phosphane)rhodium complexes 2Rh(CO)Cl (2a-d) are obtained from the silica anchored silylalkyl(ether-phosphanes) 1a-d and (μ-CIRh(CO)2>2.The palladium complex 2PdCl2 (4) is formed by addition of (COD)PdCl2 to the heterogenized alkyldiphenylphosphane (3).High pressure experiments provide information on conversion and selectivity in the hydrocarbonylation of methylacetate to ethylidenediacetate, if parameters like pressure, temperature, ether moieties in the ligands 1a-d, and composition of catalyst and synthesis gas are varied.To investigate the influence of temperature and pressure on the leaching of metals, the supported catalysts are recovered and re-used. trans-(PO)2Rh(CO)Cl (7e) is formed in homogeneous phase by reaction of 2 (5) with the ligand 6e O = Me3Si(CH2)3P(Ph)CH2CH2OCH3>.Oxidative addition of CH3I to 7e affords trans-(PO)2Rh(CO)(CH3)(I)2 (9e).In the presence of CO methyl migration in 9e leads to trans-(PO)2Rh(CO)(COCH3)(I)2 (10e).Reductive elimination of CH3C(O)I from 10e regenerates 7e, probably via the cationic intermediate O)-(P O)Rh(CO)COCH3)I> (8e).The unstable cationic (ether-phosphane)rhodium complex O)(P O)Rh(CO)COCH3)I> (11e) which is isostructural to 8e is obtained by I- abstraction from 10e.

Vinyl acetate formation in the reaction of acetylene with acetic acid catalyzed by zinc acetate supported on porous carbon spheres

Yan, Feng-Wen,Guo, Cun-Yue,Yan, Fang,Li, Feng-Bo,Qian, Qing-Li,Yuan, Guo-Qing

, p. 796 - 801 (2010)

A kind of porous carbon spheres (PCS) was prepared by the carbonization of poly(vinylidene chloride) synthesized by suspension polymerization. Structure analyses revealed the existence of bumps and holes on the surface of PCS. The PCS, with the pore size between 0.8-1.2 nm, could be used as the support of zinc acetate because of the regular shape, high specific surface area, and good mechanical strength. Vinyl acetate was produced from acetylene and acetic acid using the PCS-supported zinc acetate (PCS-Zn) under mild conditions. In a single-pass operation performed at 220°C, the conversions of acetic acid and acetylene reached 22.6 and 5.3% respectively while the activity of vinyl acetate formation was above 1000 g mol-1 h-1.

Catalytic Hydrogenation of Trivinyl Orthoacetate: Mechanisms Elucidated by Parahydrogen Induced Polarization

Pravdivtsev, Andrey N.,Brahms, Arne,Kienitz, Stephan,S?nnichsen, Frank D.,H?vener, Jan-Bernd,Herges, Rainer

, p. 370 - 377 (2021)

Parahydrogen (pH2) induced polarization (PHIP) is a unique method that is used in analytical chemistry to elucidate catalytic hydrogenation pathways and to increase the signal of small metabolites in MRI and NMR. PHIP is based on adding or exchanging at least one pH2 molecule with a target molecule. Thus, the spin order available for hyperpolarization is often limited to that of one pH2 molecule. To break this limit, we investigated the addition of multiple pH2 molecules to one precursor. We studied the feasibility of the simultaneous hydrogenation of three arms of trivinyl orthoacetate (TVOA) intending to obtain hyperpolarized acetate. It was found that semihydrogenated TVOA underwent a fast decomposition accompanied by several minor reactions including an exchange of geminal methylene protons of a vinyl ester with pH2. The study shows that multiple vinyl ester groups are not suitable for a fast and clean (without any side products) hydrogenation and hyperpolarization that is desired in biochemical applications.

Catalyst for acetylene method vinyl acetate synthesis

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Paragraph 0043-0245, (2021/11/10)

The invention relates to a catalyst for acetylene-method vinyl acetate synthesis and a preparation method thereof, and mainly solves the problem that by-product benzene content in the prior art is high. The catalyst comprises a carrier and an active component loaded on the carrier, wherein the active component comprises zinc acetate, and the carrier is activated carbon. The content of zinc acetate in the catalyst is 25 - 50g/L, the zinc acetate particle size is 3.0 - 5.0 nm, the problem is well solved, and the catalyst can be used in industrial production of acetylene-method vinyl acetate.

Post-gilding of PD-AU-coated shell catalysts

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Page/Page column 16; 17, (2018/02/28)

The invention relates to a method for producing a shell catalyst that is suitable for producing vinyl acetate monomer (VAM). The invention further relates to a shell catalyst that is obtainable by the method according to the invention and to the use of the shell catalyst according to the invention for producing VAM.