Vinyl acetate azeotrope with water

Methyl Vinyl Ketone. Methyl vinyl ketone [78-94-4] (3-buten-2-one) is a colorless Hquid with a pungent odor. It is stable only below 0°C, and readily polymerizes on standing at room temperature. It can be inhibited for storage and transportation by a mixture of acetic or formic acid and hydroquinone or catechol (266). This ketone is completely soluble in water, and forms a binary azeotrope with water (85 MVK 15 H2O vol %) at 75.8°C. 

It should be noted again that in the procedure attributed to Wilson [123], as in many other suspension polymerization procedures mentioned above and in many procedures for emulsion polymerizations to be described later, reaction temperatures are given which are above the boiling point of the monomer (72.7°C at 760 mm Hg), not to mention, above the boiling point of the vinyl acetate-water azeotrope (66°C) (composition, 92.7% vinyl acetate, 7.3% water, cf. Table I). For reactions carried out in sealed ampoules or closed bottles, this reaction temperature is readily explained. How such reaction temperatures are reached in a reflux apparatus open to the atmosphere is in question. It is hardly likely that the rate of polymerization is so rapid that no free monomer exists when it is added with conventional initiators to hot water. We presume that most of the polymerizations reported to proceed at about 66 C in an aqueous medium are simply run at reflux. At such a temperature, initiation by dibenzoyl peroxide is rather slow. If the suspension polymerization is to be forced at higher temperatures, provisions will have to be made to force the monomer into the... 

Table 10.4 presents basic physical properties of the key components. By boiling point the acetic acid is the heaviest. Vinyl acetate is a light species with a normal boiling point at 72.6 °C. Of major interest is the low-boiler heterogeneous azeotrope vinyl acetate/water with 25 mol% water and nbp at 65.5 °C. The very low solubility of vinyl acetate in water, less than 1 wt%, is to be noted. Low reciprocal solubility can be exploited for separating the mixtures vinyl acetate/water by azeotropic distillation. In addition the densities of water and vinyl acetate are sufficiently distinct to ensure good liquid-liquid decanting. 

The first separation step produces essentially the liquid ternary mixture vinyl acetate, water and acetic acid with some dissolved gases. Other light and heavy components are neglected. The RCM analysis indicated as feasible the separation of the heterogeneous azeotrope VAM/water in top followed by quantitative separation of components by decantation. The flowsheet configuration is shown in Figure 10.5. The feed of the column (C-3) collects the ternary mixture from the absorber combined with the water solution from the wash column. The column... 

Step 1. For this process we must be able to set the production rate of vinyl acetate while minimizing yield losses to carbon dioxide. During the lifetime of the catalyst charge, catalyst activity decreases and the control system must operate under these different conditions. To maintain safe operating conditions, the oxygen concentration in the gas loop must remain outside the explosivity region for ethylene. The azeotropic distillation column must produce an overhead product with essentially no acetic acid and a bottoms product with no vinyl acetate. The absorber must recover essentially all of the vinyl acetate, water, and acetic acid from the gas recycle loop to prevent yield losses in the CCf removal system and purge,... 

FIG. 13-95 Number of theoretical stages versus solvent-to-feed ratio for extractive distillation, (a) Close-boiling vinyl acetate-ethyl acetate system with phenol solvent, (b) Azeotropic acetone-methanol system with water solvent. 

Emulsion polymerization reactors are made of stainless steel and are normally equipped with top-entry stirrers and ports for addition of reactants. Control of the reaction exotherm and particle size distribution of the polymer latex is achieved most readily by semibatch (also called semicontinuous) processes, in which some or all of the reactants are fed into the reactor during the course of the polymerization. Examples are given in Chapter 8. In vinyl acetate copolymerizations, a convenient monomer addition rate is such that keeps the vinyl acetate/water azeotrope retluxing. at about 70°C. 

Ma, Xu, Liu, and Sun (2010) used perfluorosulfonic acid-poly(vinyl alcohol)-Si02/ poly(vinyl alcohol)/polyacrylonitrile (PFSA-PVA-Si02/PVA/PAN) bifunctional hollow-fiber composite membranes. The catalytic and the selective layer of the membrane were independently optimized. These membranes were synthesized by dipcoating. The performance of these bifunctional membranes was evaluated by dehydrating the ternary azeotropic composed of a water, ethanol, and ethyl acetate system (top product of a reactive distillation process of esterification of acetic acid with ethanol), obtaining separation factors of water/ethanol up to 379. An extensive assessment on the esterification reaction of ethanol-acetic acid was later published (Lu, Xu, Ma, Cao, 2013). In this case, the reaction equilibrium was broken in less than 5 h, and a 90% conversion of acetic acid was achieved after 55 h. 

A soln. of K in ferf-butanol added dropwise at 0° to a-formyl-y-carbethoxy-butyrolactone, then methyl vinyl ketone added during 0.5 hr., and stored 10 hrs. at 20 -> adduct (Y 85%) refluxed 25 hrs. in benzene containing piperidinium acetate and glacial acetic acid with azeotropic entrainment of the water formed ethyl cyclohex-2-en-4-one-l-carboxylic acid-1-lactate lactone (Y 68%). F.e. s. H. Plieninger et al., B. 94, 2106 (1961). 

We first examine the effect of changing the setpoint of the middle tray temperature control loop. Because the desirable top vapor of this column is the vinyl acetate-water two component azeotrope (at 65.45°C) and the bottom is the pure acetic acid product (n.b.p. at 118.01°C), the setpoint value of this middle temperature control loop was set to be the average of the two temperatures at 91.73°C. Table 13.7 shows five simulation runs with this temperature setpoint altered firom 71.73 to 111.73°C in increments of 10°C. This is a very wide range of values for setting this setpoint. However, even with this wide range of... 

The penalty for setting the setpoint value too high is not very severe with only a little increase in the total batch time and an increase in the acetic acid loss toward the top of the column. The reason for the wide tolerance of the setting of the middle tray temperature setpoint is because thermodynamically the bottom product will approach the heavy boiler (pure acetic acid) and the top vapor will approach the lightest boiler (vinyl acetate-water two-component azeotrope). Thus, as long as the middle tray temperature setpoint is set between these two temperatures, and also allowing for enough trays above and below the middle tray, the desirable separation will be achieved. 

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