DE1294360B - Process for the production of formaldehyde - Google Patents

Description

1 2

The process, formaldehyde by dehydrogenating For the process are suitable pure methanol,

Oxidation of methanol over silver catalysts - technically pure methanol or mixtures thereof

delivering has long been used on a large scale with water; in the latter case, the concentration

Scale executed. After the previously carried out tration of the aqueous mixtures not critical and

Process was the silver catalyst per surface 5 can be between 40 and 70 percent by weight, preferably

Unit of the catalyst bed cross-section is sometimes between 50 and 65 percent by weight, methanol

unit can only fluctuate with relatively small amounts of methanol. As an oxidizing agent,

burdens, whereby the pure oxygen as well as free oxygen are correspondingly large for the reaction

Reactors had to be used. For example, the gases contained, in particular air, should be used.

USA.-Patent 2462413 known, only with _i0 oxygen and methanol are expedient in the

Catalyst loadings between the converted 0.195 molar ratio of 0.3 to 0.6, in particular of 0.4

and 1.4631 methanol per catalyst bed cross section up to 0.5 ,, each applied. There are possible companions

Hour to work. of oxygen, such as nitrogen and argon, do not

In the German Auslegeschrift 1231229 is also calculated. A dilution of the reaction mixture, not described, for the dehydrogenative oxidation of _i5 gene with water vapor can bring advantages, methanol to formaldehyde advantageous layers, where it is expedient to use from 0.8 to 1.9 parts by volume of silver crystals, the crystals of which are water vapor per part volume of methanol vapor used, at least 50 percent by weight from crystals of the The reaction temperatures are the new grain size 1.25 to 5.0 mm, and the height go between 600 and 800 ° C, advantageously to choose between the layer between 15 and 50 mm. At ₂₀ 675 _and 750 ° C. It is possible to carry out a preferred Hchem with the customarily mentioned interpretation, as well as with underpressure and overpressure; Embodiment for the implementation described, j _m generally pressures between 0.05 and which consists in the fact that one with a two ata into consideration.

Layered catalyst works, the lower layer _D i _e silver crystals are composed in a conventional manner by silver crystals of the mentioned particle size, up _a5 electrolysis of aqueous silver salt solutions provided a thin layer of silver crystals. These silver salt solutions can be located by adding grain sizes up to 1 mm. Also, this _{resolve of} fri _sc h _em silver or used catalyst was obtained with only 1,351 of methanol per square catalyst. The composition of the three-meter catalyst bed cross-section and the hour in _{which the} grain sizes are loaded in the layers of the catalyst, in order to achieve the longest possible catalyst _{life by sieving into} grain size classes and afterwards, subsequent mixing into the desired ones

It has now been found that formaldehyde can be obtained in proportions. But you can

the gas phase by reacting methanol with ⁵ _{also steer the electrolysis so} that you can immediately

Oxygen or free-oxygen containing gases, _a suitable _{for dne d} ^J _he catalyst layers

optionally obtained in the presence of water vapor with particle size distribution.

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Ι ^ Ζ ^^ ΖίΆ ^ οΓ ^^^^ ά ^A practical arrangement of the two-layer

which are arranged as a two-layer _{catalyst, where the catalyst consists e.g.}

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uses a two-layer catalyst whose ^X >? * ^{IS 2} : ^{5 m} . ^m 'on a perforated base, the lower layer is 15 to 40 mm thick and at least 4 <> for example a sieve or a perforated plate in at least 50 percent by weight of crystals of the grain. Layer height of 15 to 40 mm, preferably 20 to 1.0 to 4.0 mm in size, and its upper 30 mm, piles up. On the layer obtained, the layer will have a thickness of 0.75 to 3.0 mm and will consist of ^em , ^{e 0} ^ ⁵ . ^ s 3.0 mm, in particular 1.0 to 20 mm crystals with grain sizes from 0.1 to 0.9 mm, a ^{layer of} silver crystals with a grain size of stands, and this catalyst with 1.5 to 3 t, ins - 45 0.1 to 0.9 mm, advantageously 0.2 to 0.75 mm, in particular with 2 to 3 tons of methanol per square meter. You can load the upper layer of the two catalyst bed and hour. Layered catalyst evenly on the lower

According to the new process, a dehydrating layer is applied. However, it is useful that the Oxidation of methanol at about the same µm layer thickness of the upper layer in the edge zone The rate should be selected to be greater than in the middle of the catalytic converter load if the load is up to more than twice as high of the catalyst bed cross-section as before. For technical execution one uses executed. As a result, the diameter of the catalyst bed of the minde process is preferred over the known ones a significantly higher space-time clearance of at least 0.5 m, for example 1 to 3 m. Through the pouring of silver they become one another

The new process is based on the surprisingly mixed and heated raw materials Observation that during the space velocity over the catalyst, if with the addition of steam, through after the invention passed to the waste of the catalyst. After leaving the catalytic converter, the activity a larger amount of methanol per Ge reaction gases cooled as quickly as possible and weight unit of the catalyst is converted into formaldehyde, the condensate being used to wash out the is converted as if the catalyst is being used. In a downstream wrestler or even more heavily loaded. the remaining 5 to 15% of the

In the case of formaldehyde, the new process can advantageously be carried out in countercurrent with water.

Methanol conversions of at least 87%, purposefully washed; the amount of water is measured

moderately from 90 to 97%, in particular from 92 to sen, that the desired concentration is obtained.

96%, run. This procedure gives 65. .

higher yields of formaldehyde and corresponding examples i and /

smaller amounts of by-products than according to the amounts given in the table

known procedures. a mixture of methanol and water is used

evaporates and, mixed with air, at 650 to 700 ° C by the catalyst indicated in the table directed. With regard to the catalyst life, it results in the time until inactivation the amount of formaldehyde obtained per kilogram of the catalyst and the yield of the catalyst Formaldehyde the results given in the table

nits:

Examples of the catalyst bed and the space velocity over the catalyst

example
(Comparison)

Dumping height

catalyst

composition
Grain size / mm

Catalyst loading tons

Methanol

Water air
Ncm ³

Catalyst life

metric tons
formaldehyde
Day j _e kg

catalyst

yield
° / o of theory,
based on methanol used

2
(1)

20 mm

25 mm
20 mm

94% = 1.0 to 3.0
6% = 0.2 to 0.75

100% = 1.0 to 3.0

94% = 1.0 to 3.0
6% = 0.2 to 0.75

2.2

2.2
1.35

1.47

1.47 0.9 2900

2900
1800

70

75
90

33.5

34.5
26.4

89.0

86.8
88.3

Claims (1)

Claim: Process for the production of formaldehyde in the gas phase by converting methanol as with oxygen or gases containing free oxygen, optionally in the presence of water vapor, at temperatures of 600 to 800 ° C on silver crystals, which are used as a two-layer catalyst are arranged, the lower layer being coarser than the upper, characterized in that that a two-layer catalyst is used, the lower layer of which 15 to 40 mm thick and at least 50 percent by weight of crystals of grain size 1.0 up to 4.0 mm and its upper layer has a thickness of 0.75 to 3.0 mm and consists of crystals with grain sizes from 0.1 to 0.9 mm, and this Katalyastor with 1.5 to 3 t, in particular loaded with 2 to 31 methanol per square meter of catalyst bed cross-section and hour.