JPS6328415B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 3.1 Industrial Application Field The present invention relates to a method for separating and purifying allyl alcohol from a mixture of allyl alcohol, allyl acetate, and water.

3.2 Prior Art Regarding the purification and recovery of allyl alcohol from the above-mentioned ternary mixture, methods using one distillation column and an azeotrope agent are disclosed in Japanese Patent Publication No. 50-28934, Japanese Patent Publication No. 48-23408, 49-4203,
There is a method using two distillation columns.

However, in these methods, allyl alcohol is only obtained as water or a mixture with water and an azeotrope, and alcohol concentration exceeding the binary azeotrope composition of allyl alcohol-water (water-72.3 wt%) is required. is not possible.

In order to perform further dehydration, it is necessary to take measures such as adding a fourth component as an azeotrope agent, which increases the size of the equipment and increases equipment costs and operating costs.

3.3 Problems to be Solved by the Invention The present invention aims to solve the above problems and provide a method for efficiently recovering highly pure allyl alcohol.

3.4 Structure and means of the present invention As a result of various studies on a distillation method that can simultaneously dehydrate allyl alcohol and remove allyl acetate, the present inventor has found that by combining a specific reflux system, it is possible to use a distillation method that can be practically used in one method. The inventors have discovered that highly pure allyl alcohol, which is functionally free of allyl acetate and water, can be obtained from the bottom of the column by using a distillation column of 1,000,000.

Although the gist is as described in the claims, specific examples of the configuration of the invention will be explained below with reference to FIGS. 1 and 2.

In Figure 1, 200w of water is supplied from raw material supply pipe 1.
The purpose is to supply a mixture of allyl alcohol, allyl acetate, and water that contains more than In this case, the water content in the overhead distillate in the overhead liquid withdrawal pipe 17 cannot be concentrated to more than 20 wt%, which is the ternary azeotropic composition.

In addition, in the vicinity of this composition, allyl alcohol behaves as a low-boiling point component with respect to water, and therefore water cannot be removed from the bottom effluent by a normal reflux method.

In the present invention, we focus on the fact that the top distillate separates into two liquid phases after cooling, and as shown in FIG.
The two phases are separated by the weir 21.

Among the two phases, the decanter rich water phase 3 is normally discharged through the rich water phase extraction pipe 4, but depending on the allyl acetate concentration in the raw material supply pipe 1, a part of it can be refluxed to the upper part of the column through the rich water phase reflux pipe 19.

On the other hand, a part of the decanter poor water phase 2 is refluxed to the upper part of the column through the poor water phase reflux pipe 16, and the remaining part is discharged through the poor water phase extraction pipe 7.

Refluxing via the poor aqueous phase reflux tube 16 causes a change in the relative volatility of water and allyl alcohol;
Allyl alcohol begins to behave as a high boiling point component.

That is, by circulating allyl acetate via the poor water phase reflux tube 16, allyl alcohol can be dehydrated. The liquid in the hydrophilic phase reflux pipe 16 may not be directly refluxed to the tower, but may be mixed with the liquid in the raw material supply pipe 1 and supplied to the tower.

If the water content in the liquid in the raw material supply pipe 1 is 20 wt% or less, water behaves as a low boiling point component with respect to allyl alcohol due to a change in specific volatility. In this case, depending on the allyl acetate concentration in the raw material supply pipe 1 liquid,
It is necessary to circulate the rich water phase from the rich water phase return pipe 19.

The principle behind this will be explained below with reference to FIG.

In Figure 3, the azeotropic temperatures at normal pressure are: a: 88.9°C b: 82.6°C c: 83.0°C i: 95.1°C Also, the boiling points of pure substances are: A: 100°C B: 97°C C: 104°C It is. Curve DE⌒ shows the solubility curve and is a straight line with DE⌒
If a ternary composition exists in the area surrounded by AC, it will separate into two phases, an aqueous-poor phase and an aqueous-rich phase, according to tie lines.

No matter which region of the ternary system is distilled, the top evaporation composition will not deviate from the low boiling point zone connecting a, b, and c due to the relationship of vapor-liquid equilibrium, and ultimately, b converge to a point.

Therefore, in normal distillation, the following 3 CASEs occur depending on the feed composition.

(CASE-1) If the feed composition is in the A-a-c region on the rich water side than the azeotrope saddle line on the water-allylic alcohol side shown by the curve connecting a, b, and c, allyl alcohol at the bottom of the column is Although allyl acetate can be removed, dehydration is impossible.

(CASE-2) Water-allyl alcohol azeotrope whose supply composition is on the rich water side of the straight line connecting ternary system azeotrope point b and pure allyl alcohol B, and is represented by a curve connecting a, b, and c. If appropriate conditions (reflux ratio/number of stages) on the water-poor side of the saddle line (area surrounded by a, b, and B) are selected, the top evaporation composition will be
Since it can be set above the AB line, dehydrated, deacetated and allyl alcohol can be obtained from the bottom of the column.

(CASE-3) Supply composition is another area b
-B-C-c region, contrary to CASE-1, dehydration is possible, but allyl acetate is not possible.

Therefore, in order to obtain highly pure allyl alcohol at the bottom of the column, it is necessary to set the feed composition in the CASE-2 region as described above. To achieve this, we set conditions that result in two-phase separation when the top vapor composition is condensed, and utilize the water-poor phase and water-rich phase.

Example The top vapor composition is set to, for example, the ternary azeotropic point b, reflux is carried out at that composition, and a portion is led to a decanter.

(CASE-1) Feed composition “f” (feed composition is
(area of CASE 1), and the supply amount is L. By returning a portion of the aqueous phase "d" in the decanter to the column, high purity allyl alcohol can be obtained in the same manner as in CASE-2 by apparently shifting the feed point from f to e.

The amount to return Γ is ef/ed×L.

Amount led to the Γ decanter Bf/Bg×gd/bd×L The composition of the top distillate is “g” in terms of balance.

(CASE-3) Feed composition “f” (feed composition is
In the case of CASE 3), contrary to CASE-1, by returning a portion of the rich water phase "h" from the decanter to the column, the supply point is apparently moved from f' to e'.

ΓReturn amount e′f′/e′h×L ΓAmount led to decanter Bf′/Bg′×g′h/bh×L The top distillate composition obtains "g'" on balance.

Further, for cooling the overhead distillate, in addition to using the tower top condenser 9 as shown in FIG. 1, an external condenser 29 as shown in FIG. 2 may be used.

3.5 Example A ternary mixture was purified using an Olderschau type rectifier having an inner diameter of 50 mm and having the configuration shown in FIG.

The preheated mixed liquid (water 21.20 wt%, allyl alcohol 40.61 wt% and allyl acetate 38.19 wt%) is sent to the supply stage 55 to the tower upper part 42 to 10 stages, the tower middle part 43 to 10 stages, and the tower lower part 44 to 20 stages. 294Kg/h was supplied.

The composition of the aqueous phase 51 in the distillate from the top of the tower is water.
7.45wt%, allyl alcohol 19.31wt%, allyl acetate 73.24wt%, and this was transferred to the poor aqueous phase reflux pipe 48.
When the reaction mixture was refluxed to a 160 kg/h tower, 83 kg/h of allyl alcohol substantially free of water and allyl acetate was obtained from the bottom of the tower.

3.6 Effects of the Invention The present invention has made it possible to purify allyl alcohol at low cost and efficiently.

[Brief explanation of the drawing]

FIG. 1 is a diagram using an internal condenser, FIG. 2 is a diagram using an external condenser, FIG. 3 is a phase equilibrium diagram of a ternary mixture, and FIG. 4 is an explanatory diagram of an example apparatus. 1... Raw material supply chamber, 2... Decanter poor water phase, 3...
Decanter rich water phase, 4...water rich phase extraction pipe, 7...poor water phase extraction pipe, 8...bottom extraction pipe, 9...tower top condenser, 1
0, 11, 12... tower, 13... reboiler, 15...
Top gas phase pipe, 16... poor water phase reflux pipe, 17... tower top liquid withdrawal pipe, 19... rich water phase reflux pipe, 20... decanter, 21... weir, 29... external condenser, 40... raw material supply pipe, 41...Tower top condenser, 42...Tower upper part, 43...
Tower middle part, 44... Tower lower part, 48... Poor water phase reflux pipe, 5
1...Aqueous phase, 52...Aqueous rich phase, A...Water, B...Allyl alcohol, C...Acetic alcohol, ED⌒...Solubility curve,...Tie line passing through point b, a...Water-allyl alcohol azeotropic point, b ...Water-allylic alcohol...Allyl acetate ternary azeotropic point, c...Water-allyl acetate azeotropic point, d...Allyl acetate phase (poor aqueous phase) at composition at point b, e...apparent feed composition, f...supply composition , g... Composition extracted from the top of the tower, h... Water phase (rich water phase) in the composition at point b, i... Allyl alcohol... Allyl acetate azeotropic point, e', f', g'... Corresponds to e, f, g.

Claims (1)

[Claims] 1. A method for separating and purifying allyl alcohol from a mixture of water, allyl acetate, and allyl alcohol, using substantially one distillation column, and from the top of the column,
A fraction with an azeotropic composition or a composition close to this composed of the above mixture is distilled out, this distillate is condensed in a condenser, and the two liquid phases generated by the condensation are separated, and then an aqueous phase is formed. A method for purifying allyl alcohol, which comprises obtaining allyl alcohol containing almost no allyl acetate and water by refluxing at least a portion of the alcohol.