JPS59106437A - Production of vinyl acetate - Google Patents

Abstract

PURPOSE:To reduce the amount of by-produced water, and to reduce the distillation load of water in the preparation of vinyl acetate by the reaction of ethylene with acetic acid and oxygen, by supplying acetic anhydride to the receptor of crude vinyl acetate after the reaction, and hydrolyzing the acetic acid with the by-produced water. CONSTITUTION:Ethylene is made to react with acetic acid and O2 in the presence of a VIII-group noble metal catalyst at 50-200 deg.C under normal pressure - 200atm to obtain vinyl acetate. The crude vinyl acetate obtained by the reaction and collected in the receptor (c) contains usually about 5% of water produced by the side reaction of ethylene with O2. In order to reduce the distillation load of water in the process from the dehydrative distillation column (e) to the vinyl acetate distillation column (f), and to produce vinyl acetate with low energy consumption, acetic anhydride is supplied to the crude vinyl acetate receptor (c) and/or the azeotropic distillation column (d) to produce acetic acid by the hydrolysis with the by-produced water, and reusing the produced acetic acid as a raw material by recycling to the acetic acid distillation column (g).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in a process for producing vinyl acetate.

The conventional method for producing vinyl acetate is to react ethylene, acetic acid, and oxygen in the presence of an undisturbed metal catalyst at normal pressure to 200 atm and 50°C to 200°C, and the flow sheet is as follows: As shown in Figure 1.

In this method, water is inevitably produced as a by-product, as shown in the following equation (1).

0H2=CH2+CH3C○OI(+ -0□1→CH
CoOCH+HO・・・(1)3 2 3
2 Furthermore, along with the reaction (1), a side reaction as shown in formula (2) also proceeds.

0H2=CH2+ 30□→2CO□+2H20・-・
・(2) Therefore, the crude vinyl acetate receiver (C) after the reaction in the flow sheet of Figure 1 usually contains around 5% water; Distillation must be carried out by each distillation column, and the distillation load for this cannot be ignored.

Therefore, if the amount of by-product water contained in the crude vinyl acetate C after the reaction can be reduced, the subsequent distillation load (2, water ζ2) can be reduced, and it should be advantageous in terms of energy.

In view of this, the present inventors have made extensive studies and found that by supplying C2 and acetic anhydride during the vinyl acetate manufacturing process,
We have discovered that the amount of by-product water can be reduced, and hereby propose the present invention.

That is, the present invention supplies acetic anhydride to a crude vinyl acetate receiver and/or an azeotropic distillation column from the reaction column shown in the flow sheet of FIG. The aim is to hydrolyze acetic anhydride with moisture and reduce the distillation load associated with water after the dehydration distillation column.

(CH3CO)YUO, + H2O−2CH3COOH
...(3) In this case, since the same mole of water as acetic anhydride is removed, the amount of acetic anhydride supplied is adjusted according to the amount of by-product water, and the crude vinyl acetate receiver and/or azeotropic distillation are It may be supplied into the tower by any suitable method.

The present invention will be specifically explained below with reference to Examples.

Example 1 Azeotropic distillation column in vinyl acetate production process ζ2 (Fig. 1 d)
190 pieces of liquid collected from (95 w% acetic acid, 5 w% water) and 10 pieces of acetic anhydride! v- was placed in a three-way flask equipped with a reflux condenser and reacted in a hot water bath kept at 70°C while stirring with a magnetic stirrer, and the reaction solution was collected every 30 minutes and analyzed by gas chromatography. The results were as shown in Table-1.

Table 1 Example 2 The same procedure as in Example 1 was carried out except that the water bath temperature was 90°C, and the results shown in Table 2 were obtained.

Table 2 In Example 1.2, as shown in Tables 1 and 2, acetic anhydride was completely hydrolyzed, and water equivalent to the added acetic anhydride was reduced. The liquid after the reaction in .2 is
The acetic acid solution was fed without any problem to the reaction column (FIG. 1a) via the acetic acid distillation column (FIG. 1g).

Example 3 A liquid (vinyl acetate 15w%,
(acetic acid 78W%, water 6W%) 190y- and acetic anhydride 10?
When the same reaction as in Example 1 was carried out in a 50°C water bath, the results shown in Table 3C-2 were obtained.

Table 3 (Including water loss due to hydrolysis of wood vinyl acetate) As is clear from Table 3, acetic anhydride was completely hydrolyzed after 240 minutes. The liquid after the reaction can be shared without any problems.
The composition had enough carbon to be fed to the fP distillation column.

From the above examples, it will be understood that by utilizing the hydrolysis of acetic anhydride supplied during the vinyl acetate manufacturing process according to the present invention, the distillation load can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing a method for producing vinyl acetate. a... Reactor, b... Gas-liquid separator, C... Crude vinyl acid receiver, d... Azeotropic distillation column, e... Dehydration distillation column, f... Vinyl acetate Distillation column, g...acetic acid distillation column, h
...High boiling point separation tower. Patent applicant Shin-Etsu Vinyl Acetate Co., Ltd.

Claims (1)

[Claims] 1. A method of synthesizing vinyl acetate by reacting ethylene, acetic acid and oxygen in the presence of a standing metal catalyst at normal pressure to 200 atm and 50°C to 200°C. A method for producing vinyl acetate, which comprises supplying acetic anhydride to a receiver and/or an azeotropic distillation column, and hydrolyzing this with by-product water.