Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Azeotropic vaporization, heat

Vinyl acetate is a colorless, flammable Hquid having an initially pleasant odor which quickly becomes sharp and irritating. Table 1 Hsts the physical properties of the monomer. Information on properties, safety, and handling of vinyl acetate has been pubUshed (5—9). The vapor pressure, heat of vaporization, vapor heat capacity, Hquid heat capacity, Hquid density, vapor viscosity, Hquid viscosity, surface tension, vapor thermal conductivity, and Hquid thermal conductivity profile over temperature ranges have also been pubHshed (10). Table 2 (11) Hsts the solubiHty information for vinyl acetate. Unlike monomers such as styrene, vinyl acetate has a significant level of solubiHty in water which contributes to unique polymerization behavior. Vinyl acetate forms azeotropic mixtures (Table 3) (12). [Pg.458]

This gives the heat received by the system per mole of mixture evaporated azeotropically at constant T and p. It is called the latent heat of azeotropic vaporization, which we shall denote by AJi ... [Pg.452]

The utilization of availability can be enhanced by maintaining a constant temperature difference between the vapor and coolant, all along the heat exchanger. This can be achieved by using a certain non-azeotropic vapor mixture which can maintain a constant temperature difference due to its variable boiling temperature characteristics. The introduction of another condensable vapor may alter the composition of the vapor and decrease the heat and mass transport in the condenser. Furthermore, the orientation of the condenser can affect the flow regime in the condenser, and hence alter the performance of the condenser. [Pg.64]

In a 2-1. flask fitted with a total-reflux, variable-take-off distillation head is placed a solution of 53 g. (0.472 mole) of dihydroresorcinol (Note 1), 2.3 g. of -toluenesulfonic acid monohydrate and 250 ml. of absolute ethanol in 900 ml. of benzene. The mixture is heated to boiling and the azeotrope composed of benzene, alcohol, and water is removed at the rate of 100 ml. per hour. When the temperature of the distilling vapor reaches 78° (Note 2), the distillation is stopped and the residual solution is washed with four 100-ml. portions of 10% aqueous sodium hydroxide which have been saturated with sodium chloride. The resulting organic solution is washed with successive 50-ml. portions of water until the aqueous washings are neutral and then concentrated under reduced pressure. The residual liquid is distilled under reduced pressure. The yield of 3-ethoxy-2-cyclohexenone (Note 3), b.p. 66-68.5°/0.4 mm. or 115-121°/11 mm., Mq 1.5015, is 46.6-49.9 g. (70-75%). [Pg.41]

Ease of recovery. It is always desirable to recover the solvent for reuse. This is often done by distillation. If this is the case, then the solvent should be thermally stable and not form azeotropes with the solute. Also, for the distillation to be straightforward, the relative volatility should be large and the latent heat of vaporization small. [Pg.185]

Vapor-liquid equilibrium compositions, K-values, activity coeff., etc., azeotrope temperature and composition, enthalpy and heat capacity, heats of vaporization... [Pg.469]

At this time 270 ml. of toluene is added to the mixture and the condenser is changed for distillation. An azeotropic mixture of ethanol, toluene, and water is distilled at 75-78° with the bath at 105-110°. When the temperature begins to drop (Note 1), 525 ml. of commercial absolute ethanol is added and the mixture is again heated under reflux for 12-16 hours (Note 2). Again 270 ml. of toluene is added, and the azeotropic mixture is distilled until the vapor temperature falls to 68°. After the residue is cooled, the system is evacuated to 25-35 mm. and the remaining ethanol and toluene are distilled. [Pg.16]

We can estimate the change in the entropy of vaporization at azeotropic temperature when the heat flow is known at azeotropic pressure... [Pg.101]

We may estimate the heat of vaporization for azeotropic mixtures from the Lee-Kesler correlation, with some suitable mixing rules... [Pg.101]

Step 5. The azeotropic distillation column does not produce the final salable vinyl acetate product. Its primary role is to recover and recycle unreacted acetic acid and to remove from the process all of the vinyl acetate and water produced. So we want little acetic acid in the overhead because this represents a yield loss. Also, the bottoms stream should contain no vinyl acetate since it polymerizes and fouls the heat-exchange equipment at the elevated temperatures of the column base and the vaporizer. Hence we have two control objectives base vinyl acetate and top acetic acid compositions. And we have two manipula-... [Pg.332]

Because of nonequilibrium boiling conditions in a simple distillation, the vapors may not contain the true azeotrope, and the heat cost may be too high. Therefore a column is still used to rectify the exact azeotrope at the head of the column however, only a few trays are required. [Pg.119]

Table I shows that, as the boiling point of the hydrocarbon used as the entrainer increases so does that of the azeotrope with water and the percent of water therein. A high percentage of water in the azeotrope is desired for the heat required for the distillation, which is mainly that of the latent heat of the water plus that of the entrainer. Sufficient entrainer should be available in the azeotrope for reflux to the column although this requirement is not large. Also, the solubility or dilution effect is better with lower-boiling hydrocarbons. Thus there are several factors to be balanced in choosing the azeotrope. The effect of relative boiling points, vapor pressures, and amounts of different entrainers in their azeotropes with water has been discussed as affecting the choice of entrainers for separating water from acetic acid (5). However, that represents a much more difficult selection because there the quantity of reflux is important and also the solvent characteristics of the entrainer for the acetic acid also control the choice. Table I shows that, as the boiling point of the hydrocarbon used as the entrainer increases so does that of the azeotrope with water and the percent of water therein. A high percentage of water in the azeotrope is desired for the heat required for the distillation, which is mainly that of the latent heat of the water plus that of the entrainer. Sufficient entrainer should be available in the azeotrope for reflux to the column although this requirement is not large. Also, the solubility or dilution effect is better with lower-boiling hydrocarbons. Thus there are several factors to be balanced in choosing the azeotrope. The effect of relative boiling points, vapor pressures, and amounts of different entrainers in their azeotropes with water has been discussed as affecting the choice of entrainers for separating water from acetic acid (5). However, that represents a much more difficult selection because there the quantity of reflux is important and also the solvent characteristics of the entrainer for the acetic acid also control the choice.
Figure 2 shows a continuous azeotropic column using a fixed amount of entrainer which remains in the unit. Since reflux is largely supplied by feed of the emulsion near the top of the column, the entrainer from the decanter passes to a reboiler and is fed back to the tower as vapors. This gives a more nearly counter-current action of the azeotropic distilling operation, and a lesser heat input required into the viscous oil at the base of the column, usually with more or less silt in suspension while... [Pg.124]

Given in the literature are vapor pressure data for acetaldehyde and its aqueous solutions (1—3) vapor—liquid equilibria data for acetaldehyde—ethylene oxide [75-21-8] (1), acetaldehyde—methanol [67-56-1] (4), sulfur dioxide [7446-09-5]— acetaldehyde—water (5), acetaldehyde—water—methanol (6) the azeotropes of acetaldehyde—butane [106-97-8] and acetaldehyde—ethyl ether (7) solubility data for acetaldehyde—water—methane [74-82-8] (8), acetaldehyde—methane (9) densities and refractive indexes of acetaldehyde for temperatures 0—20°C (2) compressibility and viscosity at high pressure (10) thermodynamic data (11—13) pressure—enthalpy diagram for acetaldehyde (14) specific gravities of acetaldehyde—paraldehyde and acetaldehyde—acetaldol mixtures at 20/20°C vs composition (7) boiling point vs composition of acetaldehyde—water at 101.3 kPa (1 atm) and integral heat of solution of acetaldehyde in water at 11°C (7). [Pg.49]

Reactive distillation is in theory a simpler process than extractive distillation, but it has yet to be demonstrated experimentally. There are two key differences between reactive and extractive distillation. First, unlike the extractive process, the HI, azeotrope is not broken, so the composition in both the liquid and vapor phases is the same. Second, the reactive process must be conducted under pressure. Figure 4.7 shows a schematic of the reactive distillation flow sheet, and the processing conditions are listed in table 4.4. In this process, azeotropic HI, is distilled inside a pressurized reactive column and the HI gas within the HI vapor stream is decomposed catalytically, resulting in a gas mixture of HI, Ij, H2, and H2O. To accomplish this, the HI feed from Section I is first heated to 262°C from 120°C and is then fed into the reactive column. At the bottom of the column, the HI is brought to a boil at around 310°C, and this boiling HI vapor results in an equilibrium vapor pressure of 750 psi inside the distillation column. [Pg.89]


See other pages where Azeotropic vaporization, heat is mentioned: [Pg.53]    [Pg.53]    [Pg.451]    [Pg.451]    [Pg.64]    [Pg.324]    [Pg.75]    [Pg.483]    [Pg.483]    [Pg.291]    [Pg.409]    [Pg.1543]    [Pg.19]    [Pg.53]    [Pg.95]    [Pg.291]    [Pg.316]    [Pg.75]    [Pg.377]    [Pg.409]    [Pg.194]    [Pg.1177]    [Pg.73]    [Pg.1365]    [Pg.58]    [Pg.80]    [Pg.483]   
See also in sourсe #XX -- [ Pg.451 , Pg.461 ]




SEARCH



Vaporization, heat

© 2024 chempedia.info