JPS63170210A - Production of chlorosilane - Google Patents

Abstract

PURPOSE:To produce trichlorosilane in high yield, by allowing metallic Si powder to react with gaseous hydrogen chloride contg. non-oxidizing gas in a fluidized bed under a special condition. CONSTITUTION:The metallic Si powder having 80-150mum mean particle size is packed into a fluidized bed reaction tube 1 and the tube is heated to 250-300 deg.C with the heater 2a, 2b. Then a gaseous mixture, which is obtained by mixing the hydrogen chloride with the non-oxidizing gas of 0.1-1.0 in the molar ratio to the hydrogen chloride amt., is fed into the reaction tube 1 at the linear velocity of 4-10 times of the velocity at which the metallic Si powder starts to fluidize and then is brought into contact with the metallic Si at the pressure of 1-4atm for 2-25sec. Thereafter the trichlorosilane and CCl4 are recovered with a trap 5 for product by separating the metallic Si entrained with the reaction gas. On the other hand, non-reacted gaseous hydrogen is introduced into a trap 6 and neutralized.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing chlorosilane, and more particularly to a method for producing chlorosilane that can produce trichlorosilane with high selectivity.

Technical background of the invention and its problems In recent years, demand for chlorosilane has increased in the field of semiconductors and as a raw material for organic silane chemistry.

In particular, trichlorosilane (Si Cl 3>) is used as a raw material for producing high-purity silicon for semiconductors and silane-based camping agents, and silicon tetrachloride (Si C14>) is used as a raw material for producing synthetic quartz.

Incidentally, a method for producing trichlorosilane and silicon tetrachloride by reacting metallic silicon and hydrogen chloride in a flowing vJ layer is conventionally known. however,
Conventional fluidized bed reaction methods have problems such as the tendency for local high temperature areas (hot spots) to occur in the fluidized bed during the reaction.

In order to prevent the occurrence of such hot spots, a method of introducing an inert gas into a fluidized bed has been proposed. However, this inert gas introduction method causes new problems in the reaction process, such as forming bubbles in the fluidized bed, making the reaction incomplete, and carrying the silicon powder raw material out of the fluidized bed. Therefore, it is not considered an effective method today.

Various attempts have also been made to optimize the reaction temperature by using specific metal catalysts (for example,
Japanese Patent Publication No. 37-18703, Japanese Patent Publication No. 61-4768
However, these conventional methods are not necessarily fully satisfactory in terms of simplification of the manufacturing process, economic efficiency, and yield of the desired product.

The present invention has been made in view of the problems associated with the prior art as described above, and is a method for obtaining trichlorosilane in high yield by relatively simple reaction control means. The purpose is to provide a method.

Oioji and 1 The present inventors have discovered that among the above-mentioned fluidized bed reaction methods, conventional
After reconsidering the inert gas introduction method, which was thought to have many disadvantages in manufacturing, and after conducting various research, we succeeded in eliminating hot spots by controlling the mixture ratio of inert gas and the linear velocity of the introduced reactant gas. It has been found that it is possible to prevent the generation of trichlorosilane and to control the temperature conditions and temperature distribution within the fluidized bed to an optimal state, thereby allowing trichlorosilane to be produced with good selectivity.

The present invention has been made based on the above-mentioned findings, and more specifically, when producing a mixture of trichlorosilane and silicon tetrachloride by reacting metal silicon powder and hydrogen chloride gas in a fluidized bed, A non-oxidizing gas is mixed at a molar ratio of 0.1 to 1.0 to hydrogen chloride gas, and the mixed gas is passed through a fluidized bed at a linear velocity of 4 to 20 times the fluidization start speed of the metal silicon powder. It is characterized in that the reaction temperature in the fluidized bed is controlled at 250 to 350°C.

Hereinafter, the method for producing chlorosilane according to the present invention will be explained in detail, including examples.

In the method of the present invention, after filling a fluidized bed reactor with metal silicon powder, hydrogen chloride (HCI) gas is introduced, and at this time, a non-oxidizing gas is mixed as a diluent gas.

The average particle size of the metal silicon powder used at this time is 80~
It is 150 μm, more preferably 90 to 120 μm. It is desirable that the amount of incidental impurities in silicon be as small as possible.

As the non-oxidizing gas to be mixed, inert gases such as N2, He, Ar, etc., and reducing gases such as H2 are used singly or in combination, and among these, N2 is preferably used. H
The mixing ratio of non-oxidizing gas to CI gas is the molar ratio (
Non-oxidizing gas/HCI) is preferably 0.1 to 1.0,
More preferably, it is 0.2 to 0.8. Mixing ratio is 0.1
If it is less than this, the temperature distribution within the fluidized bed will not be uniform, and local high temperature areas (hot spots) will likely occur, resulting in a decrease in the selective production rate of trichlorosilane, which is not preferable. On the other hand, when the mixing ratio exceeds 1.0, the amount of product chlorosilane entrained in the non-oxidizing gas and the chlorosilane gas produced by the reaction increases, making it difficult to separate and purify the non-oxidizing gas and chlorosilanes. This is not preferable because the energy required increases significantly and the process becomes complicated.

The linear velocity of the mixed gas of hydrogen chloride gas and non-oxidizing gas in the fluidized bed is 4 to 20 times, more preferably 5 to 15 times the speed at which the metal silicon powder starts to be fluidized by the introduction of the mixed gas. It is important and necessary to control it so that it doubles. The fluidization start speed of this metal silicon powder can generally be determined as follows.

Belly! Umf: Fluidization start speed [cm/sec]D
= Particle diameter [Cm] P: Fluid density C9/cm3] π εmf: Loosest filling porosity [-] Visual observation method: With respect to the gas cylinder velocity [cm/sec] introduced into the layer,
The pressure drop in the bed [g/cra] is plotted and the minimum gas cylinder velocity is read for which the pressure drop is a constant value that balances the total weight of solid particles in the bed.

The reason why the linear velocity of the mixed gas (fluidizing gas) is limited to 4 to 20 times the fluidization starting velocity of metal silicon is that a good fluidized bed is formed within this range, and therefore the temperature distribution within the fluidized bed is This is because it is maintained in an optimal state. If the linear velocity exceeds 20 times, the entrainment m of the metal silicon powder to the outside of the reaction system will increase, and the energy required for separation and purification of chlorosilanes and non-oxidizing gas will increase, resulting in a complicated process. Undesirable.

The linear velocity of the above-mentioned mixed gas, when expressed in absolute value, is usually 2 to
'l0cm/sec, more preferably 2.5 to 7.5
cm/sec, most preferably 3-5 cm/sec.

The reaction temperature in the fluidized bed is preferably 250 to 350'C1, more preferably 270 to 330C, and a specific metal catalyst is essential.

On the other hand, if the reaction temperature exceeds 350'C, the selectivity of trichlorosilane, which is more useful, will decrease and the selective production rate of silicon tetrachloride will increase, which is undesirable because it is economically disadvantageous.

Further, the reaction pressure in the fluidized bed is preferably 1 to 4 atm, more preferably 1 to 3 atm.

The contact time between silicon and mixed gas in the fluidized bed is 2 to
A range of 25 seconds is sufficient, and more preferably 3 to 10 seconds.

In the method of the present invention, sufficiently good results can be obtained without using a catalyst, but a catalyst such as cupric chloride powder may be used if desired.

According to the reaction conditions of the present invention described above, trichlorosilane can be obtained at a high selective production rate without using a specific catalyst unlike conventional methods. Note that the conversion rate of hydrogen chloride is 95 mol % or more when the contact time is 3 seconds or more.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited by these Examples.

Example 1 FIG. 1 is a schematic diagram of a reaction apparatus used in Examples. Pyrex glass reaction section (30# diameter, 700m height)
A hydrochlorination reaction was carried out using a reaction tube 1 having a gas deceleration section (50 m diameter, 300 m height).The gas dispersion plate was made of sintered glass (G-3), and the reaction tube was This was installed at a position 300 m from the bottom.

Temperature control is performed using heaters 2a and 2 provided on the outer wall of the reaction tube 1.
It was done in b. The temperature of the fluidized bed was measured using thermometer 3 at three points (directly above the dispersion plate, 1 cm above the dispersion plate, and 1 cm above the dispersion plate).
0 cm above). Note that no external cooling was performed.

On the other hand, the flow rates of the introduced gases (HCI, N2. Town) were measured using mass flowmeters (rotameters) 4, respectively.

The flow rate was controlled and supplied to the reaction tube. Metallic silicon entrained in the fluidizing gas (reactant gas) is separated by a separator, and the products trichlorosilane and silicon tetrachloride are
After cooling with water, the product was collected in a product trap 5 at a dry ice-methanol temperature.

In addition, unreacted HCI gas is removed from the HCI trap 6 containing a NaOH solution of known concentration after collecting the product.
The amount of HCI gas discharged was determined by introducing the gas into the reactor and performing a neutralization reaction, and the reaction yield was calculated from the amount of discharged metal silicon.

First, metal silicon powder having the following particle size distribution and composition ratio was prepared.

25 μm or less: 12% 25-50 μTrL: 16% 50-100μTrL: 20% 100-15C1m: 18% 150-200μTrL = 11% 200-300μTrL: 12% 3ooμm or more = 11% Si>98.3% Fe<0.46% AI <0.13% Ca <0.22% A reaction tube was filled with 130 g of the above metal silicon.

The filling height (static layer) at this time was 180 m.

Next, the reaction tube was preheated to 300°C, and N2 gas was added at 15°C.
．． 6NN/hour and HCI gas were supplied to the reaction tube at a rate of 22.8Nρ/hour. At this time, the introduced molar ratio of N2 gas to HCl gas was 0.68, and the linear velocity of the mixed gas in the reaction tube was 3.1 cm/sec (reaction temperature 31
5°C).

As the mixed gas is introduced, the bed expands to a filling height of 201 m, and the temperature of the fluidized bed rises due to an exothermic reaction. At this time, the temperature of the fluidized bed is controlled to 315 ± 2 °C by controlling the external temperature. did.

The reaction was continued for 6.5 hours while maintaining this temperature, yielding product at a rate of 46.4 g/hour. Gas chromatographic analysis of the product showed 1q of 85 mol% trichlorosilane and 15 mol% silicon tetrachloride. Moreover, the reaction yield was 99% based on the introduced HCI and the consumed metal silicon. −
After 6.5 hours, the height of the fluidized bed increased from 201 m to 111 m.
It decreased to #l111. Therefore, the contact time between the CI/N 2 mixed gas and metal silicon changed from 6.5 seconds to 3.6 seconds.

In addition, the entrained metal silicon was 5.1g/6.
It took 5 hours.

The reaction conditions and other conditions are summarized in Table 1 below.

- Example 2 and Comparative Examples 1 to 3 Using the same apparatus as in Example 1, a hydrochlorination reaction of metallic silicon was carried out in Examples and Comparative Examples in which the reaction conditions were changed. The results are summarized in Table 1 below.

Example 3 First, a metal silicon powder having the same particle size distribution and content composition as in Example 1 was prepared, and this metal silicon powder 130 and 7.8 g of commercially available copper powder (copper content of 99% or more) were thoroughly mixed. Then, the same reaction tube as in Example 1 was filled. The filling height difference (stationary layer) at this time was 190 Ml11.

Next, the reaction tube was preheated to 240°C, and N2 gas was added at 19°C.
．． 2Nj! /h, and HCI gas was supplied to the reaction tube at a rate of 19.2 Nj/h. The introduced molar ratio of N2 gas to HCI gas was 1.0, and the linear velocity of the mixed gas in the reaction tube was 2.7 cm/sec.

As the mixed gas was introduced, the bed expanded to a filling height of 212 m, and the fluidized bed temperature rose due to an exothermic reaction, but the fluidized bed temperature was controlled at 250±2° C. by external temperature control.

The hydrochlorination reaction was continued for 6.5 hours while maintaining this temperature, yielding product at a rate of 35.5 g/hour. Gas chromatographic analysis of the product showed that 87 mole % trichlorosilane and 13 mole % silicon tetrachloride were obtained.

The reaction yield was 97% based on the introduced HCI and disinfected metal silicon.

After 6.5 hours, the height of the fluidized bed increased from 212 m to 133 m.
decreased to m. Therefore, the contact time between the 1-1 cl/N2 mixed gas and the metallic silicon/copper powder changed from 7.8 seconds to 4.9 seconds. Note that the entrainment time of the metal silicon/copper powder mixture was 4.89/6.5 hours.

In addition, in the above table, the evaluation of temperature distribution was performed as follows.

If the temperature readings of thermometers installed 1 cm above the dispersion plate or 10 cm above the dispersion plate differ by 5°C or more, the temperature distribution will be 1 cm higher.
For those below °C, the temperature distribution was classified as "good."

Effects of the Invention As can be understood from the results of the above Examples and Comparative Examples, according to the production method of the present invention, trichlorosilane can be obtained in high yield by relatively simple reaction control means, and it is industrially suitable. Very useful.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a reactor system used in Examples of the present invention.

Claims (1)

[Claims] When producing a mixture of trichlorosilane and silicon tetrachloride by reacting metal silicon powder and hydrogen chloride gas in a fluidized bed, a non-containing compound with a molar ratio of 0.1 to 1.0 to the introduced hydrogen chloride gas is used. While mixing the oxidizing gas, the mixed gas is mixed at
A method for producing trichlorosilane, which comprises introducing the trichlorosilane into a fluidized bed at a linear velocity of ~20 times, and controlling the reaction temperature in the fluidized bed at 250 to 350°C.