TWI430953B - Method of preparing anhydrous hydrogen fluoride by using sodium aluminum tetrafluoride and reaction device for the same - Google Patents

Description

Method for preparing anhydrous hydrogen fluoride by using sodium aluminum fluorideate and reaction device for the same

The present invention relates to a process for preparing anhydrous hydrogen fluoride by using sodium aluminum tetrafluoride and a reaction apparatus therefor. More specifically, the present invention relates to a method for preparing anhydrous hydrogen fluoride and a reaction apparatus for the same, which comprises mixing a sodium fluoride tetrafluoride (NaAlF ₄ ) as a fluoride source with sulfuric acid in a prereactor and The pulverization is carried out to obtain gaseous anhydrous hydrogen fluoride (HF) and a solid material, and the obtained solid material is heat-treated in a main reactor to obtain gaseous anhydrous hydrogen fluoride and solid sodium aluminum sulfate (NaAl(SO ₄ ) ₂ ). According to the present invention, the expensive fluorite (CaF ₂ ) can be replaced by the NaAlF _{4 by} -product of the production of monodecane as a source of fluoride for the preparation of anhydrous hydrogen fluoride, which is very economical and environmentally friendly. Further, since the generation of the bulky solids and the fine pulverization of the reactants are suppressed by uniformly dispersing the viscous reaction intermediate calcium hydrogen sulphate (Ca(HSO ₄ ) ₂ ), the yield of HF can be remarkably improved. Further, since HF can be produced in a relatively large amount as compared with the weight of the raw material, industrial mass production is feasible. And the produced by-product NaAl(SO ₄ ) ₂ can be reused to obtain sodium sulfate and aluminum sulfate by separation.

Since the 1940s, a method of preparing anhydrous hydrogen fluoride by reacting naturally occurring fluorite with sulfuric acid has been known. In such processes, the production of anhydrous hydrogen fluoride has been improved to date by improving the reactor materials and forms.

It is formed in the reaction intermediate calcium hydrogen sulphate (Ca(HSO ₄ ) ₂ ) in the process of using anhydrous fluorite and sulfuric acid to prepare anhydrous hydrogen fluoride, which is viscous, thereby causing the starting material to coagulate with the reaction intermediate. Because of the presence of such a large amount of cohesive and strong material, the reactivity is lowered and internal heat transfer during the heat treatment becomes difficult, thereby reducing the conversion yield of HF. In addition, such a large amount of material adheres to the inner wall of the reactor to block the inside thereof.

In order to overcome the above problems, U.S. Patent No. 3,607,121 proposes a rotary kiln reactor having a casing construction. In the rotary kiln reactor of the casing construction, the reaction by-product gypsum (CaSO ₄ ) is recycled to the inlet of the raw fluorite by disposing a spiral for transferring the solid material internally to dilute the fresh fluorite. Reduce the cohesion of raw materials. However, the apparatus is provided with a transfer screw for recycling the reactants to narrow the cross-sectional area of the kiln, hindering the movement of the reactants and causing solid matter to accumulate in the kiln.

U.S. Patent No. 3,718,736 proposes a method for inhibiting the cohesiveness of a reaction intermediate by diluting a raw material by feeding a reaction by-product gypsum in a molar amount of more than three times fluorite while feeding fluorite. However, if such a gypsum system is obtained again from the completion of the reaction, the yield becomes lower.

U.S. Patent No. 4,120,939 proposes a fluidized bed reactor in which small particles of fluorite are combined at the top of a vertical reactor to inject SO ₃ and vapor into the bottom to produce and vaporize sulfuric acid and produce heat. When it falls, the fluorite falling from the top reacts with the vaporized sulfuric acid to produce HF. However, this device is complicated and it is difficult to optimize the operating conditions and thus cannot be utilized for mass production.

[Previous Technical Publication] [Patent Announcement]

US Patent No. 3,607,121

US Patent No. 3,718,736

US Patent No. 4,120,939

In order to solve the problems of the prior art as described above, it is an object of the present invention to provide an economical and environmentally friendly method for preparing anhydrous hydrogen fluoride and a reaction apparatus therefor, which can be solved by a viscous reaction intermediate. The problem of cohesiveness significantly improves the yield, thereby making it possible to industrially produce HF.

In order to achieve the above object, the present invention provides a method for preparing anhydrous hydrogen fluoride, which comprises the steps of: (1) mixing and pulverizing sodium fluoride tetrafluoride (NaAlF ₄ ) and sulfuric acid as a fluoride source in a pre-reactor; Gaseous anhydrous hydrogen fluoride (HF) and a solid material, and (2) heat treatment in the main reactor to obtain the solid material from the step (1) to obtain gaseous anhydrous hydrogen fluoride and solid sodium aluminum sulfate (NaAl(SO ₄ ) ₂ ).

Another aspect of the present invention provides a reaction apparatus for preparing anhydrous hydrogen fluoride, comprising: (1) a temperature controllable kneading type pre-reactor having a fluoride raw material inlet, a sulfuric acid inlet and a mixture outlet; and (2) temperature controllable A rotary kiln type main reactor having a kneader mixture inlet connected to a mixture outlet of the kneader type pre-reactor, a gaseous anhydrous hydrogen fluoride outlet, and a solid product outlet.

According to the present invention, the expensive fluorite (CaF ₂ ) can be replaced by the NaAlF _{4 by} -product of the production of monodecane as a source of fluoride for the preparation of anhydrous hydrogen fluoride, which is very economical and environmentally friendly. Further, since the generation of the bulky solids and the fine pulverization of the reactants are suppressed by uniformly dispersing the viscous reaction intermediate calcium hydrogen sulphate (Ca(HSO ₄ ) ₂ ), the yield of HF can be remarkably improved. Furthermore, since HF can be produced in a relatively large amount as compared with the weight of the raw material, industrial mass production is feasible. Further, the produced by-product NaAl(SO ₄ ) ₂ can be reused to obtain sodium sulfate and aluminum sulfate by separation.

Hereinafter, a method for producing anhydrous hydrogen fluoride according to the present invention and a reaction apparatus for producing anhydrous hydrogen fluoride will be described in detail.

In the step (1) of the present process for producing anhydrous hydrogen fluoride, there is no particular limitation on the sodium aluminum fluoride (SAF) as a fluoride source. Preferably, a NaAlF _{4 by} -product produced by the reaction of the SiF ₄ gas with the reducing agent NaAlH ₄ to produce monodecane may be used, as shown in the following reaction formula 1) or by mechanical milling of AlF ₃ and A mixture of NaF was prepared as the NaAlF ₄ product as shown in the following reaction formula 2). In particular, it is more economical and environmentally friendly to use the NaAlF _{4 by} -product produced in the process of preparing monodecane.

1) SiF ₄ + NaAlH ₄ → SiH ₄ + NaAlF ₄

2) AlF ₃ + NaF → NaAlF ₄

In the step (1) of the present process for producing anhydrous hydrogen fluoride, sulfuric acid is used in an amount satisfying the following reaction formulas 3) and 4) based on the SAF feed amount.

3) NaAlF ₄ + 2H ₂ SO ₄ → NaAlF ₂ (HSO ₄ ) ₂ + 2HF (main reaction in the pre-reactor)

4) NaAlF ₂ (HSO ₄ ) ₂ +2H ₂ SO ₄ →NaAl(HSO ₄ ) ₄ +2HF (second reaction in the pre-reactor)

In the step (1) of the present process for preparing anhydrous hydrogen fluoride, the SAF may preferably be used in a powder form (about 20 micrometers (μm) size) or a granular form (about 1 millimeter (mm) size). Sulfuric acid may use 98% sulfuric acid, or fuming sulfuric acid may be used to reduce corrosion. There is no limitation on the manner of feeding the SAF and sulfuric acid as starting materials. In terms of process efficiency, continuous feed is preferred.

Any reactor capable of mixing and pulverizing SAF and sulfuric acid can be used as the pre-reactor used in the present process for preparing anhydrous hydrogen fluoride, and is not particularly limited. However, depending on the reaction process of the above formula 3) and formula 4) in the prereactor, the amount of sulfuric acid is reduced to reduce the fluidity of the reaction mixture, and a viscous NaAl(HSO ₄ ) _{4 by} -product is produced. Thus, for uniform mixing, the pre-reactor must be capable of mechanically mixing and comminuting the reactants. Accordingly, a temperature-controlled, kneading-type pre-reactor is particularly preferred as the pre-reactor system.

The form of the kneader is not particularly limited. However, it must be able to uniformly mix the SAF and sulfuric acid and heat them to 100 to 300 ° C so that the reaction can proceed. It must also be capable of comminuting the reaction mixture to a size of preferably 1 mm or less and then feeding it into the main reactor in the next step. Such a kneader can be manufactured in a double helix or a general batch kneader can be used.

In the step (1) of the present process for producing anhydrous hydrogen fluoride, it is preferred to control the reaction conditions so that a total reaction of about 50% can be carried out, thereby obtaining gaseous anhydrous hydrogen fluoride (HF) and a solid material. Since the pre-reactor is assembled in a sealed manner to prevent the generated gas from being dissipated from the inlet of sulfuric acid and SAF, the gaseous anhydrous hydrogen fluoride is discharged to the outside after being transferred to the main reactor, and preferably the solid material is pulverized to 1 mm. It is transferred to the main reactor in a smaller size.

In the step (2) of the present process for producing anhydrous hydrogen fluoride, gaseous anhydrous hydrogen fluoride (HF) and solid sodium aluminum sulfate (SAS) are obtained from the solid material obtained in the step (1).

According to the above Reaction Formulas 3) and 4), HF is obtained from the unacted NaAlF ₄ and H ₂ SO ₄ present in the solid material obtained in the step (1). According to the following reaction formula 5), gaseous anhydrous hydrogen fluoride and SAS are obtained from NaAl(HSO ₄ ) ₄ which is obtained from the solid material obtained in the step (1) or in the reaction of the step (2), and the unacted NaAlF ₄ . Further, according to the second reaction of the following reaction formula 5), gaseous anhydrous hydrogen fluoride and SAS are obtained from NaAlF ₂ (HSO ₄ ) _{2 which is} obtained from the solid material obtained in the step (1) or in the reaction of the step (2). .

5) NaAl(HSO ₄ ) ₄ +NaAlF ₄ →2NaAlF ₂ (HSO ₄ ) ₂ →2NaAl(SO ₄ ) ₂ +2HF

Any reactor capable of producing a gaseous anhydrous hydrogen fluoride and SAS as long as it can carry out the reaction of the above formula 3) to formula 5) can be used as the main reactor used in the step (2) of the present process for preparing anhydrous hydrogen fluoride, without particular limitation. . It is preferred to use a temperature control, rotary kiln reactor.

According to a specific example of the present invention, a rotary kiln reactor having a length of 5 m, a width of 1 m, a number of revolutions of 1 to 6 rpm, and a slope of 1/500 can be used. The residence time of the reactants can be adjusted by the feed rate of the feedstock, the rotational speed of the kiln or the discharge level of the reactants. The reaction temperature is preferably from 100 to 700 ° C, more preferably from 200 to 500 ° C and still more preferably from 300 to 500 ° C. Heating can be carried out by external heating. A float valve may be provided at the end of the rotary reactor to discharge the reaction product SAS. It is preferred to control the residence time of the reactants by adjusting the height of the float valve. The residence time of the reactants is preferably from 2 hours to 6 hours. The generated HF passes through a filter to remove fine particles, and is compressed by a compressor and stored in an HF high pressure tank. As for the operating pressure, in order to facilitate the discharge of the gas generated by the pre-reactor and the main reactor, it is preferred to carry out the reaction under a pressure-reducing condition maintained at -20 mmHg to atmospheric pressure. The SAS solid product is discharged outside the kiln, and then can be reused by separating sodium sulfate and aluminum sulfate.

According to another aspect, the present invention provides a reaction apparatus particularly suitable for the above-described method for producing anhydrous hydrogen fluoride, the apparatus comprising: (1) a temperature control of a fluoride raw material inlet, a sulfuric acid inlet and a mixture outlet, and a kneading type pre-reaction And (2) a kneader mixture inlet having a mixture connection with the kneader type pre-reactor, a temperature-controlled, gaseous rotary hydrogen fluoride outlet and a solid product outlet, a rotary kiln main reactor. A specific example of the reaction apparatus of the present invention is shown in Fig. 1.

Referring to Fig. 1, a preparation procedure of the present anhydrous hydrogen fluoride using the present reaction apparatus will be exemplified below.

First, the raw material is fed into a kneader (B) as a prereactor through a fluoride raw material inlet (1) and a sulfuric acid inlet (2). The sulfuric acid is fed to the kneader (B) via a backflow prevention screw (D) connected to the motor (E). The kneader (B) is heated to 100 to 300 ° C to initially react, mix and pulverize the raw materials therein, and then transferred to the kiln (A) as a main reactor. The kiln (A) is heated to 300 to 500 ° C and rotated to complete the action. The final solid product is discharged outside the kiln via the discharge screw (C) and the gaseous HF is collected via the gas outlet (3).

The invention will be described in more detail by way of the following examples and comparative examples. However, they do not limit the scope of the invention.

[Examples 1 to 5] Preparation of anhydrous hydrogen fluoride by using a kneader and a kiln reactor

The fluoride raw materials used in Examples 1 to 4 were powdered (about 20 μm in size) or granular (about 1 mm in diameter) sodium aluminum tetrafluoride (NaAlF ₄ ), which was produced from the preparation of monodecane (SiH ₄ ). A by-product of the action of antimony tetrafluoride (SiF ₄ ) and sodium aluminum hydride (NaAlH ₄ ). The fluoride raw material was dried in a calciner at 300 ° C and fed to a kneader reactor at a feed rate of 6.87 kg / hr (kg / hr). The fluoride raw material used in Example 5 was a product prepared by mechanically milling a mixture of AlF ₃ and NaF.

At the same time as the fluoride feedstock was fed, an equivalent ratio of 98% concentrated sulfuric acid was fed into the kneader reactor at a feed rate of 10.70 kg/hr. The reactants are allowed to remain in the kneader reactor for 2 minutes or longer. The kneader reactor was maintained at 200 ° C and the gases produced were collected via a gas outlet line in the kiln. The reaction intermediate passing through the kneader is further subjected to a high temperature to act on the kiln to produce anhydrous hydrogen fluoride. The yield was determined by titration based on the amount of anhydrous hydrogen fluoride obtained by feeding sulfuric acid for 12 hours. The results are shown in Table 1 below.

The production of anhydrous hydrogen fluoride increases as the temperature of the kiln increases. In the case of having a relatively small amount of the raw material in Example 4, the production of anhydrous hydrogen fluoride was increased by increasing the residence time in the kneader and in the kiln.

[ Comparative Examples 1 to 3] Preparation of anhydrous hydrogen fluoride by using only a kiln

A powdery (about 20 μm size) or granular (about 1 mm diameter) sodium aluminum tetrafluoride (NaAlF ₄ ) was dried in a calciner at 300 ° C and fed to a kiln reactor at a feed rate of 6.87 kg / hr. in. At the same time, an equivalent ratio of 98% concentrated sulfuric acid was fed into the kiln reactor at a feed rate of 10.70 kg/hr to carry out the reaction. The gases produced are collected via a gas outlet line in the kiln. The yield was measured in the same manner as in the examples. The results are shown in Table 2 below.

In the example of reacting SAF and sulfuric acid by using only a kiln without a kneader reactor, kiln clogging occurs due to accumulation of reaction intermediates in the kiln reactor.

[Comparative Examples 4 to 5] Preparation of anhydrous hydrogen fluoride by using only a kneader

A powdery (about 20 μm size) or granular (about 1 mm diameter) sodium aluminum fluoride (NaAlF ₄ ) was dried in a calciner at 300 ° C and fed to a kneader reaction at a feed rate of 6.87 kg / hr. In the device. At the same time, an equivalent ratio of 98% concentrated sulfuric acid was fed into the kneader reactor at a feed rate of 10.70 kg/hr to carry out the reaction. The kneader reactor has a diameter of 1.2 m, and the kneader is surrounded by a heating jacket to be maintained at 150 ° C to 200 ° C. The generated gas is collected via a gas outlet line connected to a solid storage tank disposed at the end of the kneader. The yield was measured in the same manner as in the examples. The results are shown in Table 3 below.

In the example of reacting SAF and sulfuric acid using only a kneader without a kiln reactor, the solid material is discharged in a wet state, and anhydrous hydrogen fluoride is low in output due to a low reaction temperature.

1‧‧‧ hydrogen fluoride raw material inlet

2‧‧‧ sulfuric acid inlet

3‧‧‧ gas export

A‧‧‧Rotary Kiln Reactor

B‧‧‧Kneader Reactor

C‧‧‧Draining spiral

D‧‧‧Preventing backflow spiral

E‧‧‧Motor

Fig. 1 is a view showing a specific example of a reaction apparatus for producing anhydrous hydrogen fluoride according to the present invention.

1. . . Hydrogen fluoride raw material inlet

2. . . Sulfuric acid inlet

3. . . Gas outlet

A. . . Rotary kiln reactor

B. . . Kneader reactor

C. . . Spiral discharge

D. . . Prevent backflow spiral

E. . . motor

Claims (7)

A method for preparing anhydrous hydrogen fluoride comprises the steps of: (1) mixing and pulverizing sodium tetrafluorofluoride as a source of fluoride and sulfuric acid in a prereactor to obtain gaseous anhydrous hydrogen fluoride and a solid material, and (2) in the main The heat treatment in the reactor is obtained from the solid material of the step (1) to obtain gaseous anhydrous hydrogen fluoride and solid sodium aluminum sulfate, wherein the reaction in the pre-reactor is carried out at 100 to 300 ° C, and wherein the main reactor The reaction is carried out at 300 to 500 °C. The method for preparing anhydrous hydrogen fluoride according to claim 1, wherein the sodium aluminum tetrafluoride is prepared by reacting a silicon tetrafluoride (SiF ₄ ) gas with a reducing agent sodium hydrogen hydride (NaAlH ₄ ). A by-product produced during the process of decane, or a product prepared by mechanically milling a mixture of aluminum fluoride (AlF ₃ ) and sodium fluoride (NaF). The method for preparing anhydrous hydrogen fluoride according to claim 1, wherein the pre-reactor is a kneader reactor. The method for producing anhydrous hydrogen fluoride according to claim 1, wherein the solid material obtained from the step (1) is pulverized to a size of 1 mm (mm) or less and transferred to the main reactor. The method for producing anhydrous hydrogen fluoride according to claim 1, wherein the main reactor is a rotary kiln reactor. The method for producing anhydrous hydrogen fluoride according to claim 1, wherein the reaction is carried out under a reduced pressure condition maintained at -20 mmHg to atmospheric pressure. The method for producing anhydrous hydrogen fluoride according to claim 1, wherein the solid sodium aluminum sulfate obtained from the step (2) is separated into sodium sulfate and aluminum sulfate.