Carbon vinyl acetate monomer process

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. 

Vinyl acetate was first described in a German patent awarded to Fritz Klatte and assigned to Chemishe Fabriken Grieshiem-EIectron in 1912. It was identified as a minor by-product of the reaction of acetic acid and acetylene to produce ethylidene diacetate. By 1925, commercial interest in vinyl acetate monomer and the polymer, polyvinyl acetate, developed and processes for their production on an industrial scale were devised. The first commercial process for vinyl acetate monomer involved the addition of acetic acid to acetylene in the vapor phase using a zinc acetate catalyst supported on activated carbon. This process was developed by Wacker Chemie in the early 1930s and dominated the production of vinyl acetate until the 1960s when an ethylene-based process was commercialized which supplanted the earlier acetylene technology [24]. 

Vinyl acetate monomer can be produced by the vapor phase reaction of acetylene and acetic acid using a zinc acetate on activated carbon catalyst. The reaction can be carried out in either the liquid or vapor phase but the vapor phase process is more efficient [28]. The chemistry is as follows ... 

Vinyl acetate monomer can be synthesized by the reaction of acetic acid with either acetylene or with ethylene. For the production of vinyl acetate from acetic acid and acetylene, the following process was adopted a gaseous mixture of acetylene and acetic acid was reacted at about 200°C in the presence of active carbon impregnated with zinc acetate... 

The two-carbon short-chain acetic acid is start material for the production of vinyl acetate monomer (VAM). This application consumes one third of the world s production of acetic acid (Cheung et al. 2005). The product of the condensation of two molecules of acetic acid is acetic anhydride. The worldwide production of acetic anhydride is a further major application and uses approximately 25-30 % of the global production of acetic acid. The main process involves dehydration of acetic acid to give ketene at the temperature of 700-750 °C. Ketene is thereafter reacted with acetic acid to obtain the anhydride (Held et al. 2005). Acetic anhydride is an acetylation agent. As such, its major application is for cellulose acetate, a... 

The co-monomers such as vinyl acetate, acrylate esters, or carbon monoxide are fed together with ethylene, or introduced by liquid pumps, into the suction of the secondary compressor. The concentration in the feed of the co-monomer which is required to achieve a certain level of the co-monomer in the resulting polymer depends on the reactivity ratios, ri and r2, which are the ratios of rate constants of chain-propagation reactions [5]. The values for the co-monomers used in the high-pressure process are presented in Table 5.1-3. In the case of vinyl acetate, both reactivity ratios are identical and therefore the composition of the copolymer is the same as that of the feed. The concentration of vinyl acetate, for example, in... 

Poly( vinyl alcohol) is a versatile polymer with many industrial applications, and it may be the only polymer with an all carbon-carbon bond backbone that is truly biodegradable. The monomer is vinyl acetate, which is readily polymerized with free radical initiators to form poly(vinyl acetate), and the latter can be hydrolyzed either partially to prepare vinyl alcohol-vinyl acetate copolymers, or fully to prepare poly(vinyl alcohol). At high vinyl alcohol contents, the copolymers, and the vinyl alcohol homopolymer, are water soluble, and the aqueous solutions of these polymers find many applications for example, as adhesives or for coatings. The homopolymer and the very high vinyl alcohol copolymers are crystalline with melt transitions between 180 and 230 °C and glass transitions between 58 and 85 °C, depending on the vinyl alcohol content. The polymers can be melt processed to form molded plastics, fibers and films [36]. 

Polymers with pendant cyclic carbonate functionality were synthesized via the free radical copolymerization of vinyl ethylene carbonate (4-ethenyl-l,3-dioxolane-2-one, VEC) with other imsaturated monomers. Both solution and emulsion free radical processes were used. In solution copolymerizations, it was found that VEC copolymerizes completely with vinyl ester monomers over a wide compositional range. Conversions of monomer to polymer are quantitative with complete incorporation of VEC into the copolymers. Cyclic carbonate functional latex polymers were prepared by the emulsion copolymerization of VEC with vinyl acetate and butyl acrylate. VEC incorporation was quantitative and did not affect the stability of the latex. When copolymerized with acrylic monomers, however, VEC is not completely incorporated into the copolymer. Sufficient levels can be incorporated to provide adequate cyclic carbonate functionality for subsequent reaction and crosslinking. The unincorporated VEC can be removed using a thin film evaporator. The Tg of VEC copolymers can be modeled over the compositional range studied using either linear or Fox models with extrapolated values of the Tg of VEC homopolymer. 

Solvent effects on, and products from, reaction of styrene with ethylene in the presence of di-)ti-chloro-dichlorobis(styrene)dipalladium(n), [Pd-(Ph CH—CH2)Cl2]2, indicate a mechanism similar to (i)->(iv) above, with the addition of a preliminary equilibrium between the dimer and solvated monomers. The mechanism of reaction of styrene with vinyl compounds, catalysed by the same chloride-bridged dipalladium complex, has been studied using isotopic tracer (H, D) experiments. Palladium-acetate-catalysed reaction of styrene with benzene, also investigated using deuterium tracer experiments, involves no hydride shift, in contrast to the rather closely related Wacker process. The importance of intermediates with palladium-carbon n-bonds in palladium(ii)-catalysed alkylation and arylation of alkenes has been demonstrated. 

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