Process for the preparation of ethyl acetate

Details Process for the preparation of ethyl acetate Process for the preparation of ethyl acetate

2001-06-05

2004-10-26

Raymond, Richard L. (Department: 1624)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C560S238000, C560S239000

Reexamination Certificate

active

06809217

ABSTRACT:

This invention relates to a process for the production of ethyl acetate.
Etyl acetate is a relatively expensive bulk chemical which is conventionally produced by esterification of acetic acid with ethanol according to equation (1):
CH
3
.CO.OH+CH
3
CH
2
OH═CH
3
.CO.O.CH
2
.CH
3
+H
2
O  (1).
Because this reaction does not tend to lead to formation of by-products which have boiling points close to that of ethyl acetate, recovery of substantially pure ethyl acetate from the esterification product mixture is usually not complicated by the presence of by-products of the esterification reaction.
Some other methods which have been proposed for the conversion of ethanol to ethyl acetate, however, tend to lead to formation of by-products, notably n-butyraldehyde and butan-2-one, which have boiling points close to that of ethyl acetate and hence make the recovery of substantially pure ethyl acetate from the resulting reaction product mixtures more difficult than from esterification reaction mixtures. These methods include dehydrogenation of ethanol, oxidation of ethanol, reaction of ethanol with acetaldehyde, and oxidation of ethanol to acetaldehyde followed by the Tischenko reaction.
Ethyl acetate can be produced from acetaldehyde according to the Tischenko reaction given in equation (2):
2CH
3
.CHO═CH
3
.CO.O.CH
2
.CH
3
  (2).
It is also possible to produce ethyl acetate from ethanol by dehydrogenation according to equation (3):
2CH
3
.CH
2
.OH═CH
3
.CO.O.CH
2
.CH
3
+2H
2
  (3).
According to China Chemical Reporter, 26 Mar. 1996, a plant with a capacity of 5000 tonnes per annum for production of ethyl acetate by dehydrogenation of ethanol has been constructed at Linshu Chemical Fertilizer Plant of Shandong using a catalyst developed by Qinghua University.
Ethanol is produced in large quantity by a variety of processes, including hydration of ethylene, the Fischer Tropsch process, or as a fermentation product. The purity of the ethanol often depends upon the method used for its production. For example, although hydration of ethylene yields a substantially pure ethanol product, the Fischer Tropsch process yields also a number of by-products which are troublesome to remove from the ethanol product. In the case of fermentation, the ethanol product is obtained as an aqueous solution which may also contain by-products whose removal from the ethanol is difficult.
In certain circumstances ethanol may be available in excess capacity, whilst acetic acid is not readily available in the necessary quantity. Accordingly, there are many reasons why, particularly in countries having a relative abundance of ethanol with respect to acetic acid, it is commercially interesting to produce ethyl acetate from ethanol, acetaldehyde or a mixture thereof.
Catalytic dehydrogenation of alcohols with reduced copper under ultra violet light was described by S. Nakamura et al, in
Bulletin of the Chemical Society of Japan
(1971), Vol. 44, pages 1072 to 1078.
K. Takeshita et al described reduced copper catalysed conversion of primary alcohols into esters and ketones in
Bulletin of the Chemical Society of Japan
, (1978) Vol. 51(9), pages 2622 to 2627. These authors mention that the mechanism for ester formation has been described in the literature as the Tischenko reaction. That is to say that dehydrogenation of ethanol yields acetaldehyde as an intermediate which combines according to the Tischenko reaction to produce ethyl acetate. Alternatively, or as well, 1 mole of ethanol may combine with 1 mole of acetaldehyde to yield 1 mole of ethyl acetate and 1 mole of hydrogen according to equation (4)
CH
3
CH
2
OH+CH
3
.CHO═CH
3
.CO.O.C
2
.CH
3
+H
2
  (4).
U.S. Pat. No. 4,996,007 teaches a process for the oxidation of primary alcohols to aldehydes, acids and esters, particularly to aldehydes. In this process a primary alcohol is contacted, together with molecular oxygen, with a catalyst selected from ruthenium, rhodium, platinum, palladium, rhenium and mixtures thereof, optionally a quaternary C
1
to C
20
alkyl ammonium cocatalyst, and as oxygen activator dihydrodihydroxynaphthalene, dihydrodihydroxyanthracene or a mixture thereof. The product aldehydes, acids and esters are then separated from the reaction mixture.
In U.S. Pat. No. 4,220,803 catalytic dehydrogenation of ethanol for the production of acetaldehyde and acetic acid using a supported copper oxide essentially free of barium is proposed.
A silver-cadmium alloy catalyst has been suggested for use in production of alkyl alkanoate esters, by contacting a primary alkanol in the vapour phase with the catalyst at a temperature of between about 250° C. and 600° C., in U.S. Pat. No. 4,054,2424.
In U.S. Pat. No. 4,440,946 there is described a process for producing a carboxylate ester which comprises contacting a mixture of alcohol and aldehyde in the vapour phase with a coprecipitate composition comprising silver-cadmium-zinc-zirconium which is substantially in the free metal form.
Use of the Tischenko reaction for the production of mixed esters from aldehydes is described in U.S. Pat. No. 3,714,236.
U.S. Pat. No. 5,334,751 teaches production of ethyl acetate by reaction of ethanol and oxygen in the presence of a solid catalyst that contains crystalline TiP
2
O
7
and has the formula Pd
a
M
b
TiP
c
O
7
, where M is Cd, Au, Zn, Tl, or an alkali metal or alkaline earth metal, a is 0.0005-0.2, b is 0.3a, c is 0.5-2.5, x has a value to satisfy the valencies, and Ti and P of the crystalline TiP
2
O
7
represent part of the crystalline TiP
2
O
7
.
BR-A-91/04652 teaches pre-treatment of a palladium on a silica carrier catalyst for production of ethyl acetate by direct oxidation of ethanol with air.
Production of esters from primary alcohols by dehydrogenation using bromous acid or a salt thereof in acid medium is described in JP-A-59/025334.
In SU-A-362814 there is described a process for production of ethyl acetate by dehydrogenation of ethanol at 180° C. to 300° C. in the presence of a copper catalyst containing zinc as an activator with an ethanol feed rate of 250 to 700 liters per liter of catalyst per hour.
The dehydrogenation of ethanol to form ethyl acetate is described in GB-A-287846. This proposes use of a dehydrogenating agent, such as a copper catalyst, a temperature of from 250° C. to 500° C., and a pressure of more than 10 atmospheres (1.013×10
6
Pa).
Vapour phase contact of ethanol at a temperature above its critical temperature with a catalyst comprising copper and a difficultly reducible oxide, such as zinc oxide or manganese oxide, is proposed in GB-A-312345, use of a temperature of 375° C. and a pressure of 4000 psi (27.58 Mpa) being suggested.
GB-A-470773 teaches a process for conversion of ethanol to ethyl acetate by dehydrogenating ethanol over a catalyst consisting of a reduced metal, for example, copper on infusorial earth with 10% uranium oxide as promoter, maintained at a temperature of 220° C. to 260° C., removing by condensation some of the gas-vapour product rich in hydrogen resulting from the reaction, and returning the gaseous remainder rich in hydrogen to the catalysing zone.
EP-A-0151886 describes a process for the preparation of C
2+
esters of alkyl carboxylic acids from C
2+
primary alcohols which comprises contacting a vaporous mixture containing a primary C
2+
alkanol and hydrogen in an alkanol:hydrogen molar ratio of from 1:10 to about 1000:1 at a combined partial pressure of alkanol and hydrogen of from about 0.1 bar (10
3
Pa) up to about 40 bar (4×10
6
Pa) and at a temperature in the range of from about 180° C. to about 300° C. in a catalytic reaction zone with a catalyst consisting essentially of a reduced mixture of copper oxide and zinc oxide, and recovering a reaction product mixture containing a primary C
2+
alkyl ester of an alkyl carboxylic acid which ester contains twice as many carbon atoms as the primary C
2+
alkanol.
In EP-A-0201105 there is described a method for converting primary alcohols, s

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