DE1206408B - Process for the production of acidic ammonium fluoride - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

COIc

German KL: 12 k-1/16

Number:
File number:
Registration date:
Display day:

J 22039IV a / 12 k

5th July 1962

December 9, 1965

The invention relates to a process for the production of acidic ammonium fluoride with a molar ratio HF: NH ₃ between 1.50 and 2.10.

For some years now, ammonium bifluoride has been used in industry as a particularly suitable fluorinating agent used. It has the property that about 70% contained hydrogen fluoride by simple to release thermal decomposition. Because of this, this acidic solid salt can be used as a source for HF to be considered. Its main uses are: glass grinding, removal of Crusts in cooking utensils, descaling and cleaning agents in the petroleum industry, production of Beryllium metal, in laundries and cleaning companies and as an antifungal agent in breweries and for the preservation of wood.

Its fluorinating effect is also used in the production of inorganic (HF ₃ , UF ₄ ) and organic fluorine derivatives.

Usually this product is made an aqueous one by adding the required amount of ammonia Hydrogen fluoride solution obtained with salt formation. Then it is evaporated, and the Crystals are centrifuged.

This procedure that must be applied must if the hydrogen fluoride is only available in solutions or as a by-product from another Processing is obtained, in industrial practice encountered difficulties, which are always related to the crystallization, Filtration, centrifugation and drying are related. In addition, the gained Ammonium bifluoride sinter or agglomerate, causing serious problems later feeding and dosing arise.

The object of the invention is to create a process for the production of acid Ammonium fluoride, the disadvantageous work-up from aqueous solution and the shortcomings of the so produced Product avoids.

The process according to the invention for obtaining acidic fluorammonium with a molar ratio HF: NH ₃ between 1.50 and 2.10 is characterized in that hydrogen fluoride and ammonia, both essentially anhydrous, in a molar ratio between the values 1.50 and 2.10 are reacted, the reaction mixture is condensed and immediately afterwards converted into the solidification state on a cooling surface.

A preferred embodiment provides that hydrogen fluoride and ammonia are reacted in a molar ratio between 1.98 and 2. Preferably, the reaction mixture is part of a process for the recovery of acidic
Ammonium fluoride

Applicant:

Societä Edison, Milan (Italy)

Representative:

Dr.-Ing. H. Negendank, patent attorney,

Hamburg 36, Neuer Wall 41

Named as inventor:

Franco Gozzo,

Paolo Bortolini, Milan (Italy)

Claimed priority:

Italy 7 July 1961 (12 468)

Surface with a temperature not exceeding 160 ° C condensed and on a surface with a Solidified at a temperature not exceeding 100 ° C.

When using this method, compared to all previously known methods are essential Advantages through easy management of the plant, high conversion performance, purity of the product and other properties noted.

The advantages are in detail:

Extensive elasticity in the composition, which is only determined by the ratio with which the reagents (HF and NH ₃ ) are fed in. In the form of flakes or shards with a smooth surface, the product is easy to dose and, under normal conditions, easy to handle without any difficulties arising from the chemical side. In view of the numerous uses of ammonium bifluoride, the invention offers the possibility of obtaining products with a number of chemico-physical properties that can be varied _{by the ratio of HF: NH 3.}

Constancy of the HF content. After determining the desired ratio in the end product

509 757/373

3 4

HF: NH ₃ in the reaction gases remains on the cylinder surface. The acid fluorammonium film

HF content in the product without affecting that on the cylinder is according to an already known

Plant constant in the range of + 0.5% if and in the industry with widely used processes

the NHj gas flow remains constant and the HF aid is broken up into scales by knives. It's falling

Gas flow random fluctuations of +1% 5 then due to its own weight via a funnel into the

has around the setpoint. corresponding collection container.

The yield is 99%. ^{Thanks to the} rapidity of solidification, condensation and reaction and because that with the outside air

The facility is easy to drive. no longer _in Related melt time

ίο remains in the molten state, a chemical

With a molar ratio HF: NH ₃ = 2, the corresponding composition of the product obtained, corresponding to the compound NH ₄ HF ₂ , the system is and essentially corresponds to that with which the stable. It partially decomposes when the reagents are fed in. The losses become the melting temperature and develop a larger one as a result, reduced to about 1 Vo , although the amount of melt HF is kept under a slight negative pressure according to equation 15.
jyjjj jjp _ ^ J ^ [JJ 1 2 HF ^ ^u ^ ^ ^em paths from the reaction zone for solidification ^{42 3} 'capture zone is no moving mechanical member being obtained at a richer NH ₃ melt. needed.

On the other hand, the system RF NH ₃ low Specifically, the reaction between fluorine-HF: NH ₃ molar ratio, so escapes abundant 20 is hydrogen and ammonia uniform and continuous-NH _3, and the melt accumulates at HF. If the two reagents are brought into contact with the melt at a temperature close to that of the melt, a very narrow zone, the temperature is maintained so that they mix rapidly. <
Although it is not absolutely necessary, the molar ratio HF: NH ₃ = about 1.90 equals hydrogen fluoride, expediently in gaseous form with vapors of the same composition, and equals an equivalence at the contact zone. When the reaction between HF and weight temperature is reached, in the case of the vapor phase and NH ₃ in the gaseous phase, the reac- liquid phase is in equilibrium with each other, the heat of the ion is quickly removed and the product and the product melted during processing in the surrounding area condensed. At faster pressure between 230 and 240 ° C, without solidification of the goods on a cold surface, cooling or thermal insulation intervenes with very high performance a product that must be obtained.

practically the same composition as that. It has also been found appropriate to have the sum of the two reagents fed in. Agitation between the gases in a cruciform was found to be the best method to run the reactor at a molar flow ratio HF: NH ₃ to both pure ammonium bifluoride (NH ₄ HF ₂ ), between 1.8 and 2.10. Under these ratios, as well as a product with variable ratios, the mixture was mixed particularly quickly to obtain _{HF: NH 3.} and complete.

It has also been observed that the intrinsic is just below the narrow reaction zone

Shafts of solid products depending on the HF: NH ₃ - 40 effective heat exchanger arranged, which

Ratio are quite different. Does this have a z. B. in the test facility from a vertical

Value of 1.98 to 2, the solid substance is colorless, the bundle of tubes consisted of one in the closed

transparent and brittle; it shows in the case of a sub-circuit circulating liquid is flowing around it,

search with X-rays the characteristic whereby the liquid in the opposite direction to the reaction

Spectrum of ammonium bifluoride. When the value 45 flows tion mixture.

gradually drops below 2, the solid material loses the melted material is immediately transferred to the

its transparency, gradually receives a dull bottom of a tub. The level of the good

white color and becomes progressively harder. He will be in the tub by ongoing removal with the

to a homogeneous union of NH ₄ HF ₂ - and the surface of a rotating cylinder

NHjF crystals. 50 hold, with the inner part of this cylinder with

Other mem- Water is cooled accordingly. The inlet temperature of the

times, such as the solubility and the sliding melt in the tub, will be at a value between

like between the surfaces that with the ab- the melting temperature of the product and 160 to

increase in the HF: NH ₃ ratio. Maintained 170 ° C. In the extraction of ammo

Preferably, in the case of the nium bifluoride according to the invention, it was considered expedient to

Process the reagents HF and NH ₃ in the water to keep this temperature at 130 to 140 ° C, where-

free state in a small reaction chamber at about atmospheric pressure.

Brought into contact, which results in the evaporation. A higher temperature favors evaporation

Mixing through a heat exchanger and dispersing the material, thereby increasing the performance

leads, in which the material is practically completely reduced in the 60.

Finally, the temperature of the outer surface of the tub is drained, the temperature of which is kept slightly above that of the cylinder between the zone of contact with the melting point. Melted material and the cutting knives are arranged above the tub, depending on the dimensions and the HF content of the material in a known manner Inflow into the interior of the cylinder changed more or almost the whole horizontal cross-section of the less quickly. In the case of a reduction, the tub covers. The melt solidifies immediately to the HF: NH ₃ molar ratio below 1.9 to 2

It is advantageous to reduce the inflow of the cooling liquid, since the solidified product with gradual Cooling rests better on the surface and does not come off before the cutting knife is in action step.

To prevent evaporation of the material, it is necessary that the temperature of the surface in the warmest zone, namely at the point of contact with the melt, is not higher than 100 ° C.

To make the process easier to understand, two examples are given below.

example 1

In a reactor, consisting of a cross-shaped tube made of Monel metal, NH ₃ gas is fed through a vertical line and HF gas through the two horizontal lines in the following quantities:

NH ₃ 35.9 kg / h

HF 84.6 kg / h

The speeds of the two gases are:

NH ₃ 15m / sec

HR 35 m / sec

As a result of the presence of the gaseous and liquid phases, the temperature takes on an equilibrium value and stays at this value by itself, which is between 235 and 238 ° C. The reaction mixture is in a tube bundle through a Cooling liquid condenses, the inlet and outlet temperature of which at the heat exchanger 130 or 155 ° C.

The molten material emerging from the tube bundle reaches a temperature of 135 ° C into a tub and immediately solidifies on the surface of a rotating, internally water-cooled cylinder.

Over the course of 12 hours, the total production of ammonium bifluoride in clear Shed 1439 kg.

The chemical analysis of an average sample of the product gives the following result:

HF (free acid) 34.88%

H ₂ O 0.12%

F: NH ₄ + 1.99 molar ratio

An X-ray analysis of the same pattern shows the spectrum of the compound NH ₄ HF ₂ without any impurities.

Example 2

With the device of Example 1, HF and NH _{3 are} reacted in gaseous form in a ratio of 1.9 moles of HF per mole of NH ₃ in a narrow reaction zone. The temperature in this zone is

ίο 234 ° C. The reaction mixture becomes in the melting state condensed and put on a crusher in the form of white, semi-transparent Shed converted into a solid state. The output of finished product is 99%.

The chemical analysis of an average sample gives:

HF (free acid) 32.7%

H ₂ O 0.2%

NH ₃ 30.8%

F: NH ₄ + 1.90 molar ratio

An analysis of the same pattern with the aid of X-rays shows, in addition to the spectrum of ammonium bifluoride, less pronounced peaks which are characteristic of the neutral fluoride NH ₄ F.

Claims (3)

Patent claims: 1. Process for the production of acidic fluorammonium with a molar ratio HF: NH ₃ between 1.50 and 2.10, characterized in that hydrogen fluoride and ammonia, both essentially anhydrous, in a molar ratio between the values 1.50 and 2.10 are reacted, the reaction mixture is condensed and immediately afterwards converted into the solidification state on a cooling surface. 2. The method according to claim 1, characterized in that hydrogen fluoride and ammonia are implemented in a molar ratio between 1.98 and 2. 3. The method according to claim 1 and 2, characterized in that the reaction mixture to condensed on a surface with a temperature not exceeding 160 ° C and on a surface solidified at a temperature not exceeding 100 ° C. 509 757/373 11.65 © Bundesdruckerei Berlin