DE557650C - Process for the production of formaldehyde - Google Patents

Description

Process for the production of formaldehyde It has already been proposed To produce formaldehyde through the catalytic combination of carbon monoxide with hydrogen, possibly in the presence of water vapor, which, however, remains unchanged in the end product finds again.

However, these methods have not proven their worth in practice.

The invention now relates to a process for the production of Formaldehyde, which is based on the fact that the new reaction 2C0 + H20-CO2 + HCOH be carried out in the presence of suitable catalysts on an industrial scale can. The water required for the reaction can be in liquid or vapor form State to be present.

It is already known from carbon dioxide and water in the presence of Catalysts to produce formic acid, and on the other hand one has after various Methods Formic acid is converted into formaldehyde. However, it is not yet known been that the total conversion according to the above empirical formula in a single operation can be made with a single catalyst.

Runs under the conditions described in more detail below the reaction almost exclusively in terms of the stated molecular formula, others between Carbon oxide and water - also possible reactions, e.g. B.

CO -f- H20 - C02 --f- H2 CO + I-12 O = @ H C 02 H, can be found in noticeable extent does not take place.

The reaction on which the invention is based is preferably allowed go on under pressure and at temperatures of about zoo to 60 degrees. The cheapest The value for the temperature depends on the level of the applied pressure. As catalysts the metals or oxides of the groups magnesium-zinc, manganese, tin and antimony are used. On the other hand, the metals or metal oxides of the chromium group, vanadium, copper, Keep away from the iron-cobalt-nickel group, as well as the alkali metals that make up the water attack even when cold. The other metals have no significant effect.

You can also use salts of the abovementioned catalyst metals, for example those of these salts, such as formic acid salts, which no other Element included than the elements included in the reaction equation, or the salts produced by combining the effective oxides with not harmful Oxides, for example magnesi-umsilicate, can be obtained.

It goes without saying that the above catalysts - either - alone or mixed with one another or in combination with one another (e.g. antimonsaures Magnesium) can be used.

According to the foregoing, those in contact with the gases can Walls of the reaction vessel by indifferent metals such as aluminum, or by Alloys of such metals with one another or through alloys and associations such metals react with harmful metals (e.g. tin-plated Copper).

Since the reaction takes place under -developing heat, -so can if necessary, take the known measures to dissipate the excess heat, and the reaction in the appropriate temperature range. to keep zen. _ _ The carbon dioxide may contain gases, such as hydrogen, nitrogen, oxygen, methane, etc., which with regard to the catalysts used and the reaction conditions show remarkable peculiarity; that they are practically indifferent and to be found again in the residual gases.

The following is an example of an embodiment of the present Invention to be described 'in which water is used in the liquid state will; in the drawing is a 'device shown schematically, - the one can use for this `purpose.

In this drawing, A 'is a pressure-resistant steel pipe; that with one inner jacket B made of aluminum is provided, within which "the catalytic material C is located. The carbon dioxide is fed to the lower part at D under pressure, while the water heated to the desired temperature is added to the upper part E is depressed. This water flows in the opposite direction as the carbon dioxide; and above at F- a mixture of carbon dioxide, water vapor and carbonic acid flows out, that will be subjected to further treatment after the carbon dioxide has been eliminated can. On the other hand, water flows out below at G, the formaldehyde and carbonic acid contains in a dissolved state.

As an example, the working conditions should be given under which you can work with this facility on a smaller scale. -As a catalyst If a mixture of 2 MgO = [- Sb20g is chosen, it is applied to a pumice stone support and inserted into the jacket B in a space 45 mm in diameter by 450 mm in length will. Under a pressure of 45o atm. at D there are about 8oo 1 carbon dioxide in the Hour, while at E under the same pressure 5oo ccm of water at 2oo ° to be introduced; the reaction temperature is raised by suitable heating Maintained 34o ° .. --- At this temperature the vapor tension of the water is approximately i 5oAtm; at a total pressure of 45oAtm. is the partial pressure of the carbon dioxide 300 atm., So that the gas phase has the molecular composition corresponding to the desired reaction has, namely 2 C0 + H20. A need to maintain that relationship " however does not exist.

At G water comes out, the weight of about 12 ° 10% formaldehyde contains, and in the gas escaping at F one can determine that about 13 °! O CO have disappeared, while 6 ° I carbonic acid have formed.

If marL uses carbon oxide which has been obtained from a hydrogen-rich gas mixture by separation, it usually still contains considerable amounts of hydrogen, which, however, have no influence on the course of the process. - - Are z. B. in the specified device every hour 800 liters of a gas mixture with 85% carbon oxide; iö °] o hydrogen and 5 ° / o nitrogen - under a pressure of 4500 atmospheres. introduced and = also soo ccm of water under the same pressure; in this way, a solution with about 10 % formaldehyde is obtained at G. while at F about 7501 of a mixture escapes which contains -79 to 80 ° 10 carbon dioxide, 5 ° 10 carbon dioxide; contains io to ii ° 1o hydrogen and 5 ° 1o-- nitrogen.

One recognizes - that - the nitrogen as well as the hydrogen -not participate in the reaction, remain inert and remain almost completely in the residual gases find again.

The use of water in a liquid state, i.e. at temperatures below its critical point, offers several advantages, in particular that the reaction is not limited, because - the - equilibrium - present in the gas phase will. by the permanent excretion of the formaldehyde produced by dissolution postponed. The elimination of formaldehyde is almost complete, since the Vapor tension of the aqueous formaldehyde solution can be neglected; accordingly the escaping gases contain very little formaldehyde.

In addition, the planned uptake of the carbon dioxide is ensured by a- Circulation of the same carried out in countercurrent to the water and the formation of polymers of Formaldehyde avoided, which would otherwise occur with dry condensation .of the gaseous reaction products arise. Finally the liquid water forms a thermal flywheel, which avoids any local increase in temperature will.

Claims (3)

PATENT CLAIMS: i. Process for the catalytic production of formaldehyde from carbon dioxide, characterized in that carbon dioxide, which has practically been freed from hydrogen, is reacted with water in the liquid or vapor state in the presence of catalysts and at temperatures above 200 °, preferably at 32o to 36o °. 2. The method according to claim i, characterized in that that oxides and salts of metals from the groups magnesium-zinc, manganese, Tin or antimony can be used. 3. embodiment of the method according to claim i and 2, characterized in that the reaction preferably takes place under temperature and pressure conditions are made that cycle a liquid water stream and a stream of carbon dioxide in opposite directions in contact enable with the catalyst.