DE1216290B - Process for the production of vinyl acetate - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07c

German class: 12 ο -19/03

Number: 1216 290

File number: F 43090IV b / 12 ο

Filing date: June 5, 1964

Opening day: May 12, 1966

As is known, the industrial production of vinyl acetate takes place predominantly by converting Acetic acid with acetylene in the gas phase over a zinc acetate-carbon catalyst. In more recent times are Also, procedures have been described that are in place of acetylene use ethylene and oxygen and are therefore of economic importance, because ethylene is much cheaper than acetylene. In this type of process, catalysts are used used, which is a noble metal of group VIII of the Periodic Table of the Elements according to Mendelejeff, especially palladium, either in the form of salts, with an additional redox system is present, or in elementary form. The main by-product of this process is Acetaldehyde. In addition, carbon dioxide, carbon oxide, ethyl acetate, methyl acetate and acetone are also used obtain. The formation of these by-products makes the purification of the vinyl acetate difficult and makes it technical laborious.

There has now been a method of making vinyl acetate by reacting acetic acid with Ethylene and molecular oxygen in the gas phase in the presence of a solid, composed of a carrier and a Noble metal of group VIII of the Periodic Table of the Elements found existing catalyst, which is characterized in that the catalyst contains a manganese compound in addition to the noble metal. The reaction mixture obtained consists practically only of vinyl acetate and water in addition to unchanged Source material.

A noble metal of group VIII of the periodic table serves as a catalyst in the most finely divided elementary form Shape. Palladium is generally preferred. However, for example, platinum, ruthenium, Suitable for rhodium and iridium. The precious metals are expediently on a carrier, e.g. B. activated carbon, pumice stone, Silica gel or aluminum oxide, which is soaked with a solution of a manganese compound and is applied is then dried again at an elevated temperature.

The manganese compound can be any one or more manganese compounds, especially Use manganese salts, which preferably contain manganese as cations, but also in the anion may contain. Manganese (II) salts, especially manganese (II) acetate, are preferred. Other manganese (II) salts, such as manganese (II) sulfate and manganese (II) chloride, with which the carrier containing the noble metal is added The beginning of the reaction can be impregnated by the vaporous which is passed over during the reaction Acetic acid is converted more or less quickly into manganese (II) acetate.

Process for the production of vinyl acetate

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning,

Frankfurt / M.

Named as inventor:

Dr. Hans Krekeler, Wiesbaden;

Dr. Hans Fernholz, Fischbach (Taunus);

Dr. Günter Jacobsen, Frankfurt / M.-Höchst

The concentration of the noble metal in the catalyst can be chosen, for example, to be 1 to 40 percent by weight, preferably 5 to 30 percent by weight. The concentration of the manganese compounds in the catalyst can vary within wide limits. Advantageously, impregnating the carrier with a 1 to 10 ° / _o solution of the manganese compound, especially an aqueous solution of manganese (II) salt.

The reaction is in the gas phase by passing a mixture of acetic acid, ethylene and Oxygen carried over the catalyst. One or more of these respondents can Contain additives of inert gases. The oxygen is preferably supplied in the form of air. The ethylene can optionally contain nitrogen, ethane or carbon oxides. The condensable Fractions are worked up to vinyl acetate in a known manner, advantageously by distillation. Not in Acetic acid which has undergone the reaction can be used again for the reaction after the water of reaction has been removed will. The unreacted gaseous

Components ethylene and oxygen are expediently recycled back into the reaction zone. The reaction is expediently in the temperature range between 100 and 25O ⁰ C, especially between 130 and 18O ⁰ C.

The molar ratio of acetic acid to ethylene to oxygen can be varied within wide limits. Has advantage is in many cases a ratio of 4: 5: 1. But other compositions can also lead to good results Lead to results. You only have to ensure that you do not enter the area of the known explosion limits for ethylene-oxygen mixtures.

609 568/568

The invention is illustrated by the following examples. The yield percentages are percentages by weight. The catalyst used in the examples was prepared as follows:

16.6 g of palladium (II) chloride are dissolved in 42 ml of half-concentrated hydrochloric acid with heating. 190 g of granulated activated charcoal are impregnated with this solution. When the solution is fully absorbed by the porous carbon, a mixture of 19.4 g of 85 ° / _o hydrazine hydrate and 266 ml of 1-η sodium hydroxide solution is added. The mixture remains at room temperature for 6 hours with repeated shaking at the beginning. The solid catalyst is then poured off the liquid and washed by repeated decanting with water until it reacts neutral. It is then ^{dried at 120 °} C. for 24 hours. The catalyst contains about 5 percent by weight metallic palladium.

Comparative example 1

A glass tube 600 mm long and 20 mm inside diameter is filled with part of the catalyst prepared in the manner described above. At a temperature of 150 ^° C., 28 Nl of ethylene, 5.6 Nl of oxygen and 60 g of evaporated acetic acid are passed through the tube every hour and a mixture consisting of unchanged acetic acid, water, vinyl acetate and acetaldehyde is then obtained by condensation. The conversion of ethylene is 3.4 ° / _0, the yield of vinyl acetate 86 ° / ₀ and di & acetaldehyde 9%, based on reacted ethylene.

example 1

Operating under the stated conditions in Comparative Example 1 with the difference that poured over the catalyst prepared according to Comparative Example 1 prior to its use for vinyl acetate with a 10 ° / _o aqueous solution of manganese (II) acetate. After 6 hours of standing, the excess solution is decanted and the catalyst dried for 12 hours at 12O ⁰ C. If, as indicated in Comparative Example 1, ethylene, oxygen and acetic acid are now passed over this catalyst, the conversion of ethylene is 5.2%, the yield of vinyl acetate is 95% and that of acetaldehyde is 0.1%, each based on the ethylene converted .

Compare example 2
■ '- - ■ ■

Under the given conditions in Comparative Example 1 is introduced at 150 ⁰ C every hour 18 Nl of ethylene, 6.5 Nl of oxygen and 120 g of acetic acid in vapor form over the catalyst indicated there, ίο The conversion of ethylene is 3.0%, the yield of vinyl acetate 88 %, of acetaldehyde 8%, each based on converted ethylene.

Example 2

The procedure is as indicated in Comparative Example 2, but that described in Example 1 is used Catalyst. The ethylene is converted to 3.8%. Vinyl acetate is obtained in a yield of 96% and acetaldehyde in a yield of 0.02%, each based on the ethylene converted.

The difference from 100% here and in the other examples consists mainly of carbon dioxide.

Claims (4)

Patent claims: 1. Process for the production of vinyl acetate by reacting acetic acid with ethylene and molecular oxygen in the gas phase in Presence of a solid catalyst containing, on a support, a Group VIII noble metal of the periodic table of the elements, especially palladium in elemental form, because of this characterized in that the catalyst is a manganese compound in addition to the noble metal contains. 2. The method according to claim 1, characterized in that the manganese compound is a Manganese (II) salt, especially manganese (II) acetate. 3. The method according to claims 1 and 2, characterized in that the carrier with a 1- to 10% aqueous solution of a manganese (II) salt is impregnated. 4. Process according to Claims 1 to 3, characterized in that at temperatures between 100 and 250 ⁰ C, preferably between +5 130 and 180 ⁰ C, works. 609 568/568 5.66 © Bundesdruckerei Berlin