Palladium acetate monomer

The commercial process for the production of vinyl acetate monomer (VAM) has evolved over the years. In the 1930s, Wacker developed a process based upon the gas-phase conversion of acetylene and acetic acid over a zinc acetate carbon-supported catalyst. This chemistry and process eventually gave way in the late 1960s to a more economically favorable gas-phase conversion of ethylene and acetic acid over a palladium-based silica-supported catalyst. Today, most of the world s vinyl acetate is derived from the ethylene-based process. The end uses of vinyl acetate are diverse and range from die protective laminate film used in automotive safety glass to polymer-based paints and adhesives. 

The most difficult problem in the selectivity between the various reactions is the way in which oxygen inhibits formation of Va, although it is expected that oxygen is involved, only after further steps in the sequence. Perhaps palladium acetate monomer and Va arise by the following equilibrium process ... 

A gold-palladium catalyst which includes potassium acetate is very well established for the production of vinyl acetate monomer (VAM) from ethene, acetic acid and oxygen in selectivities as high as 96% (see Section 8.4). VAM is an important intermediate used in the production of polyvinyl acetate, polyvinyl butyral and a variety of other polymers, and the gold-catalysed process followed many years of industrially focused research and patent activity in a number of large industrial companies 39-43... 

Leap A process for making vinyl acetate monomer. It uses a fluidized bed of a new catalyst in powder form the reactants are acetic acid, ethylene, and oxygen. Developed by BP Amoco and first operated in Hull, England, in 2001. The catalyst is a supported gold-palladium alloy made by... 

World production of vinyl acetate monomer was 4 x 10 t in 1999. This represented 84% of the total capacity. In 2002, North American companies produced 1654 X 10 t of vinyl acetate. See Table 5 for producers and their capacities (22). The dominant method of production in North America is by the reaction of ethylene with acetic acid and oxygen in the presence of palladium catalyst. New construction in recent years has been focused in southeast asia, although European and North American producers have expanded their plants. 

The major use of acetic acid is for the production of vinyl acetate monomer (VAM). This application consumes approximately 40% to 45% of the world s production of acetic acid. The reaction is of ethylene and acetic acid with oxygen over a palladium catalyst. 

Vinyl acetate is the most available and widely used member of the vinyl ester family. This colorless, flammable liquid was first prepared in 1912. Liquid-phase processes were commercialized early in Germany and Canada, but these have been replaced generally by vapor-phase processes. Earlier commercial processes were based on the catalyzed reaction of acetylene with acetic acid. The more recent technical development is the production of vinyl acetate monomer from ethylene and acetic acid. Palladium catalyst is used for the vapor phase process. The ethylene route is the dominant route worldwide. 

Already, the hrst practical application for a gold-palladium catalyst within a major industrial process is well established for the manufacture of vinyl acetate monomer (VAM) [22,23], and a pilot plant has been built for the production of methyl glycolate [24],... 

Carbonylation of methanol to acetic acid is fully discussed in Chapter 9. Another carbonylation process using a phosphine ligand to control the course of the reaction is a highly atom efficient route to the widely used monomer methyl methacrylate (Scheme 4.19). In this process the catalyst is based on palladium acetate and the phosphine ligand, bisphenyl(6-methyl-2-pyridyl) phosphine. This catalyst is remarkably (>99.5%) selective for the 2-carbonylation of propyne under the relatively mild conditions of <100 °C and 60 bar pressure. 

Pol5uireas were among the first polycondensation pol-5mers to be employed as catal dic supports for heterogeneous metal catalysts. The first report about palladium on polyurea, by Zhang and Neckers [99] dates back to 1979. They obtained their catalyst in a two step preparation, where the co-monomers (2,4- toluendiisocyanate, TDI, and the complex between palladium acetate and 4,4 -di-amino-2,2 -bip5Tiridine) were condensed together and... 

Another route to the diol monomer is provided by hydroformylation of allyl alcohol or allyl acetate. Allyl acetate can be produced easily by the palladium-catalyzed oxidation of propylene in the presence of acetic acid in a process similar to commercial vinyl acetate production. Both cobalt-and rhodium-catalyzed hydroformylations have received much attention in recent patent literature (83-86). Hydroformylation with cobalt carbonyl at 140°C and 180-200 atm H2/CO (83) gave a mixture of three aldehydes in 85-99% total yield. 

Reaction of 4-nitro-l-benzoyl chloride with benzocyclobutene 1 provided the benzoylated product 15 [36]. The nitro group of 15 was reduced with hydrogen in the presence of palladium on charcoal to afford he amine product 16 [44]. Reaction of the amine with maleic anhydride provided the amic acid which was converted to the maleimide 17 by cyclodehydration with acetic anhydride and sodium acetate at 95 °C [45-47], This monomer and its homo-polymer will be discussed in greater detail in a later section. 

With regard to catalytic activity, a catalytic system comprising palladium(II) acetylacetonate or palladium(II) acetate, dimeth-ylanilinium tetrakis(pentafluorophenylborate), and tricyclohexyl-phosphine is more effective than a catalyst system comprising (allylPdCl)2, borate, and phosphine. It is believed that the acetylacetonate group is easily released from palladium to form a large space around the palladium, so a large norbornene monomer can access the site easily (9). 

It is also worthwhile to note that the relatively slow catalytic hydrogenolysis of A/ -Z-protected peptide derivatives pemnits some interesting chemical transformations to be performed in situ. For example, direct conversion of Z protection to Boc protection is possible when the hydrogenation is conducted in the presence of di-tert-butyl dicarbonate under neutral conditions.h Alternatively, the same transformation is achieved by the use of triethylsilane and di-tert-butyl dicarbonate in ethanol with catalytic amounts of palladium(II) acetate.h 1 More efficiently this one-pot transformation is achieved by catalytic transfer hydrogenation in the presence of di-terf-butyl dicarbonate (cf. Section 2.1.1.1.3.1.1.6).h l Similarly, peptide cyclization reactions have been performed in situ over Pd/C and the high yields of cyclic monomers are attributed to the high dilution effect as well as to catalysis of the charcoal surface.h l... 

Telomerization of Isoprene.—Reviews have appeared on isoprene and chloro-prene, and on the complex reactions of isoprene to form terpenoids (in Japanese). Isoprene reacts with magnesium, especially in the presence of Lewis acids, and the resulting complex gives adducts with aldehydes. As usual in this type of reaction, a very complex mixture is obtained. The palladium-chloride-catalysed reaction of isoprene with acetic acid gives different products in different solvents. Monomers predominate in benzene [2-methylbut-2-enyl acetate (5) and 3-methylbut-2-enyl acetate (6)] while dimers [(7), (8), neryl (9), and geranyl (10) acetates] tend to be formed in tetrahydrofuran. Further details of the synthesis of Cio alcohols from isoprene and naphthyl-lithium are available, as well as of the in situ oxidation,but there is little of novelty (see Vol. 1, p. 17). 

The vinyl ester exchange has also been studied in the chloride-free palladium(II) acetate system, using vinyl propionate as substrate. Of the three Pd(II) species present in this system (Section II, A, 2), the dimer is most reactive, with the trimer Pd3(OAc)g next, and the monomer unreac-tive. The rate expression for exchange catalyzed by the dimer is (214). 

Powell et al. (113) have utilized NMR to aid in the detection of a tri-haptoidimexy-pentahaptoijaonovaeT) equilibrium for a series of hepta-2,6-dienylpalladium acetate complexes in chloroform solution. The chemical shifts for C(l) and C(2) in IV (W = H, X = O2CCF3) are compatible with a coordinated olefin, but for IV (W = Cl, X = O2CCF3) these shifts are almost identical to those of III (W = Cl, X = hfacac) in which the olefin C(l) = C(2) is not coordinated to palladium. This evidence together with molecular weight data led the authors to conclude that IV existed in an /t (dimer)-A (monomer) equilibrium the position of equilibrium being dependent on both the olefinic substituent W and the carboxylate substituent R. 

All C-H activation procedures for polymers reported thus far have been carried out under dry inert atmosphere using sealed vessels (Schlenk glassware). Similar to small-molecule procedures, polar (DMF, DMAc) and nonpolar (toluene, THE) aprotic solvents have been used and are degassed prior to use. Most thiophene-based monomers are not commercially available and must be synthesized according to literature procedures. It is very important that these monomers be extremely pure and free of all aryl impurities since other aryl bonds may undergo C-H activation and be incorporated into the polymer. All examples have employed palladium (II) acetate or the Herrmann-Beller catalyst. The latter can be prepared from Pd(OAc)2 and tris-(t)-tolyl)phosphine. All phosphine ligands, anhydrous bases and pivalic acid are commercially available and are stored under inert atmosphere. 

The major route for the industrial production of vinyl acetate, the monomer of polyvinyl acetate (emulsion paints, adhesives) and its hydrolysis product, polyvinyl alcohol (textiles, food packaging) is closely related to the Wacker acetaldehyde process, but the industrial catalysts are heterogeneous. A mixture of ethene, oxygen and acetic acid is passed over a palladium catalyst supported on alumina at 100-200°C. The overall reaction is H C=CH2-hCHjCO H-hyO ->H2C=CHC02CH3 -hH O. Ethene is no longer cheap, so that work is being pursued to make vinyl acetate from synthesis gas (p. 384). 

Scheme 9.7 (a) Grafting from cobalt/carbon [82], (b) Water-soluble third-generation nanoparticles, attachment of monomer by ruthenium catalysts 49a-c, PEG oligomers diazonium precursor, copolymerization with attached in ortho, meta, and para positions, Grubbs second-generation ruthenium cat- phosphorylcholine in para position [84]. alyst, and reaction with palladium acetate... 

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