First vinyl acetate monomer process

We first review in Part 1 the basics of plantwide control. We illustrate its importance by highlighting the unique characteristics that arise when operating and controlling complex integrated processes. The steps of our design procedure are described. In Part 2, we examine how the control of individual unit operations fits within the context of a plantwide perspective. Reactors, heat exchangers, distillation columns, and other unit operations are discussed. Then, the application of the procedure is illustrated in Part 3 with four industrial process examples the Eastman plantwide control process, the butane isomerization process, the HDA process, and the vinyl acetate monomer process. 

We have constructed a rigorous nonlinear first-principles dynamic model of this process with TMODS. We have used the model to test the control strategy and show that it does provides effective control of the vinyl acetate monomer process. 

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... 

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]. 

Process Make a presolution of the poly(vinyl alcohol). Add to the polymerization kettle, agitate, and heat to 65°C, meanwhile adding the other ingredients of the initial reactor charge. At 65°C, add the initial vinyl acetate monomer and the first initiator. Heat cautiously to 80°C, during which time the initial vinyl acetate will polymerize (shown by the development of a blue color, a reduction or cessation of reflux, and a slight exotherm). 

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. 

To survey as completely as possible the grafting behavior of EVA copolymers toward various vinyl compounds, our investigations covered the grafting of vinyl acetate, vinylidene chloride, and acrylic and meth-acrylic esters. As polymerization processes, at first we preferred suspension polymerization to exclude the influence of solvents by terminating or transfer reactions during polymerization. Grafting by emulsion polymerization, in which the EVA copolymer was dissolved in the monomer before polymerization, was difficult because coagulate was formed as polymerization proceeded. 

In addition to homopolymers of varying molecular and particle structure, copolymers are also available commercially in which vinyl chloride is the principal monomer. Comonomers used commercially include vinyl acetate, vinylidene chloride, propylene, acrylonitrile, vinyl isobutyl ether, and maleic, fumaric and acrylic esters. Of these the first three only are of importance to the plastics industry. The main function of introducing comonomer is to reduce the regularity of the polymer structure and thus lower the interchain forces. The polymers may therefore be processed at much lower temperatures and are useful in the manufacture of gramophone records and flooring compositions. 

Vinyl acetate polymerizes very easily by radical mechanism the technical method of polymerization is also a radical process. First, a typical radical polymerization scheme of the vinyl monomer takes place in the presence of an initiator, I, to yield a pair of free radicals R ... 

Emulsion polymerization requires free-radical polymerizable monomers which form the structure of the polymer. The major monomers used in emulsion polymerization include butadiene, styrene, acrylonitrile, acrylate ester and methacrylate ester monomers, vinyl acetate, acrylic acid and methacrylic acid, and vinyl chloride. All these monomers have a different stmcture and, chemical and physical properties which can be considerable influence on the course of emulsion polymerization. The first classification of emulsion polymerization process is done with respect to the nature of monomers studied up to that time. This classification is based on data for the different solubilities of monomers in water and for the different initial rates of polymerization caused by the monomer solubilities in water. According to this classification, monomers are divided into three groups. The first group includes monomers which have good solubility in water such as acrylonitrile (solubility in water 8%). The second group includes monomers having 1-3 % solubility in water (methyl methacrylate and other acrylates). The third group includes monomers practically insoluble in water (butadiene, isoprene, styrene, vinyl chloride, etc.) [12]. 

The MFFT of the emulsion as formulated must be lower than any tempoature at which the paint is likely to be applied. For an indoor paint in the UK it is unlikely that temperatures below 10°C will be encountered, whilst the outdoor limit might be 5°C. Damage to paint films can occur should the ambient temperature fall below the Tg of the film. The Tg of a hard polymer, such as vinyl acetate, styrene or methyl methacrylate, can be reduced either by copolymerisation with a soft monomer or by adding an external plasticiser, such as butyl phthalate. On a cost effective basis external plasticisation is better for reducing the Tg. The snags are, firstly, that plasticisers are slowly lost through evaporation and, secondly, they can also diffuse into the substrate. The use of an internally plasticised polymer overcomes both problems and also saves the processing time necessary to incorporate an external plasticiser. 

A more recent application of ultrasonics has been the characterization of the extent of polymerization in a condensation or radical process. The first observations were made by Sokolov, and subsequent reports of measurements on polystyrene, poly(vinyl chloride) and poly(vinyl acetate) " have confirmed the utility of the method. It is clear that this type of study is still in its infancy however, certain facts emerge which demonstrate the importance of this method. The compressibility of a solution containing monomer and polymer is directly related to the proportion of each component present. It is therefore possible to quantitatively estimate the extent of conversion from the observed velocity of sound. In a suspension polymerization, the glass transition of the polymer forming the bead is itself a function of the extent to which unreacted monomer is retained in the system. In this case, observation of the attenuation can indicate the extent to which polymerization has occurred in the system. Unfortunately the data are not sufficiently extensive to estimate the general validity of the method for the monitoring of polymerization in reactors, although the potential has been clearly demonstrated. 

The concept of unsaturated polyesters (international abbreviation UP) which can be cured and hardened by heating with sources of radicals was developed by C. Ellis in the 1930s [1-3], and the first patent application was submitted in 1936 Ellis also discovered that dilution of the unsaturated polyesters with vinyl monomers, such as styrene (most widely used) or vinyl acetate is favorable for most applications. The dilution reduces the viscosity. Eases the dissolution of additives and catalysts and lowers the costs. The most frequently used catalysts for the curing process are peroxides. The variation of their structure allows for optimization of the cure. The most important application of UPs are ... 

Glusker (37, 38) attempted to prove that these processes are absent by an estimation of active chains by reaction with C14 labelled C02 or H8(T) labelled acetic acid, followed by measurements of the radioactivity of the polymer isolated. Most of the experiments were carried out with fluorenyllithium as initiator in toluene containing 10% diethyl-ether at —60°. At —78° at least 80% of the polymer chains were found to be active at the end of polymerization. The lowest fraction was appreciably less active. Similar results were obtained at —60° although no examination was made of the fractions of lowest molecular weight. Kinetic experiments indicated a first order decay of monomer concentration after an initial rapid consumption of about 3 molecules of monomer per initiator molecule. The mechanism suggested to explain these results involves rapid addition of fluorenyllithium across the vinyl double bond followed by the rapid addition of three monomer units. At this stage it is... 

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