DE1932522A1 - Process for the production of formaldehyde - Google Patents

Description

PATENT LAWYERS Dr. D. Thomson H. Tiedtke Q. Buhling

Dlpl.-Chem. Dipl.-Ing. Dlpl.-Chtm.

8000 MONKS 2

VAL 33

TELEPHONE 0811/22 ««

TELEGRAM ADDRESS: THOPATENT

Munich June 26, 1969 case No. B. 212OO / T 3169

Imperial Chemical Industries Limited London / Great Britain

Process for the production of formaldehyde

The invention relates to a process for the catalytic production of formaldehyde from methanol.

The production of formaldehyde from methanol is made generally carried out by mixing methanol with oxygen and a diluent over a catalyst directs. Particularly when the catalyst is metallic silver, great care must be taken to ensure that the methanol is free from impurities, especially iron compounds, which quickly destroy the catalyst poison. Accordingly, the usual methanol production for this process involves complicated and expensive distillation using two or more columns. as

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1937522

Alternatives or additional measures to the distillation process a considerable number of chemical treatments have been proposed in recent years.

According to the invention it has been found that both the distillation than the chemical treatments can be avoided even if the conditions of the process, which is produced, the methanol feedstock by W can be suitably selected.

In the process according to the invention for the production of formaldehyde, the vaporized feedstock is used Crude product of a methanol synthesis (preferably at a pressure of less than 150 atmospheres) from synthesis gas with a content of carbon dioxide over a copper-containing catalyst used.

The methanol synthesis is preferably carried out at a pressure in the range of 30 to 120 atmospheres, e.g. 80 atmospheres. So she becomes very suitable about a catalyst containing copper, zinc and a third element, e.g., chromium, as in the British patent 1 010 871, or a difficult to reducible metal of groups II to IV of the periodic table,

SO 9888/1659

as described in British Patent 1,159,035. Preferably the temperature below 300 ° C, in particular in the range of 190 ° to 27O ° C, measured at the outlet of the bed of synthesis catalyst _o The space velocity is preferably above 5000 h ~, in particular in the range of 7000 h to 25 000 calculated on the basis a pressure of one abs. Atmosphere and a temperature of 20 ° C. The synthesis gas for such a process is suitably produced by hydrocarbon steam reforming.

The reaction of methanol sur formation of formaldehyde, by .irgendeine combination wn dehydration vaiü oxidation and mLnem Oxyd- © * take place ferkatalysator of a silver © of Kiap. The method according to the invention is particularly applicable to the reaction over a silver catalyst *

If the reaction is effected in the presence of dilute Danqpf, a useful characteristic of the process according to the invention is that this vapor is formed at least in part by evaporation of the water present in the alcohol% dLrd _o Accordingly, the methanol synthesis process is preferably carried out in such a way that ei «raw product

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BATH ORIGINAL

which contains the required amount of water: the required conditions include, in particular, that a synthesis gas with a high CO ₂ and low CO content is used, as can be obtained by using raw synthesis gas of a CO exchange stage (shift stage ) or that methanol is obtained from the synthesis gas at least partially by absorption in water, fc as described in British patent application 16 853/68.

The method according to the invention is particularly advantageous when a methanol and a formaldehyde plant on must be operated at the same place, since then transporting the water-containing raw methanol does not entail any noticeable extra costs Comparison with a transport of essentially anhydrous methanol caused. If the two plants are the same Operated locally, further advantages can be obtained by summarizing of the two plants can be achieved. In particular " which can be the hydrogen-containing exhaust gas from a formaldehyde process including a dehydrogenation with a previous catalytic desulfurization of normally liquid hydrocarbon can be used in the synthesis gas generation stage the methanol plant is used.

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Example 1

A plant for the production of formaldehyde comprises the three main processes:

(a) Synthesis gas production by steam reforming of desulfurized Naphta (boiling point 30 ° to 170 ° C) at a steam ratio of 3.0, a temperature of 80 ° C and one Pressure of 12.7 atmospheres (180 psig),

(b) Methanol synthesis over a copper-zinc oxide-aluminum oxide catalyst at a pressure of 50 atmospheres,

(c) Synthesis of formaldehyde by transferring the evaporated Raw methanol with added air over a silver catalyst at atmospheric pressure,

The synthesis gas had the following composition (percent by volume); CO ₂ 15-16, CO 11-12, H ₂ 65-67, CH ₄ 6-7? the raw methanol, which was condensed from the converted synthesis gas, consisted of 76% w / w methanol and 24% w / w water. This mixture was evaporated and passed over a granular silver catalyst. The temperature of the gas leaving the catalyst was 595 to 600 ^° C. A formalin solution containing 15.2% w / w formaldehyde and 14.0 % w / w methanol was obtained condensed, with the remainder being water, Despite the fact that no measures were taken to purify the

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Methanol were undertaken, the activity of the silver catalyst remained, as seen from the essentially constant gas temperature, over a 21 1/2 hour Operation unchanged

Example 2

A plant for the production of formaldehyde by reacting methanol with air in the presence of steam over a silver catalyst is charged with aqueous crude methanol (30:70 w / w) as it condenses from the synthesis cycle system of an ICI low-pressure methanol plant at a temperature of 260 ° C and a space velocity of 9600 h ~, other conditions of the synthesis stage being the same as those of Example 1. The water-containing raw methanol is evaporated in the evaporator of the formaldehyde plant by a steam coil and an air atomizer, then to about 100 ^{Preheated to 0} C, mixed with dilute steam and passed to the granular silver catalyst, over which a reaction takes place at 600 ° to 650 ° C. The flow rates of the reactants are as follows:

Methanol 478 kg / h
Air 6OO Rm ³ A

Total steam 287 kg / h (206 kg with methanol sucked

give, 81 kg added as such). 90 9 88 6/16 59

A formalin solution (37% w / w formaldehyde plus 5% methanol in water) is drawn from the plant at a rate of 24 t / day obtained without any operational disruptions despite the fact that the methanol used was not purified became.

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Claims (7)

Claims [1.1 Process for the production of formaldehyde from Methanol, characterized in that the vaporized crude product of a methanol synthesis from synthesis gas is used as the starting material used with a content of carbon dioxide over a copper-containing catalyst. 2. The method according to claim 1, characterized in that the vaporized crude product is used as the feedstock a methanol synthesis at a pressure in the range of 30 to 120 atmospheres. 3. The method according to any one of the preceding claims, characterized in that the vaporized crude product of a methanol synthesis at a temperature is used as the starting material used in the range of 190 ° to 270 ° C. 4. The method according to any one of the preceding claims, characterized in that the vaporized crude product of a methanol synthesis at a space velocity is used as the starting material used in the range from 70,000 to 25,000 h. 909886/1659 ORIGINAL INSPECTED 5. The method according to any one of the vorhBggßlnpndeto claims, characterized in that the formaldehyde is produced from methanol by a combined dehydrogenation and oxidation, the catalyst being silver. 6. The method according to any one of the preceding claims, characterized in that the formaldehyde in one Plant at the site of a plant for methanol synthesis. 7. The method according to any one of the preceding claims, characterized in that the formaldehyde in one produces a formaldehyde plant that supplies hydrogen-containing exhaust gas and supplies this with a methanol feedstock, that from one of a normally liquid hydrocarbon generated synthesis gas was produced, with the exhaust gas in a previous desulfurization of normally liquid hydrocarbon used.