JPH0714452B2 - How to treat gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas containing dichlorosilane discharged from a manufacturing process of dichlorosilane, which is one of the raw materials of the semiconductor industry, and a utilization process such as epitaxial film formation. , How to handle safely.

[Conventional technology]

Dichlorosilane reacts with water to form a solid substance composed mainly of siloxane, and this solid substance has impact ignition properties.

Conventionally, to treat a gas containing dichlorosilane,
A method of washing the gas with an aqueous solution of caustic soda and neutralizing it has been carried out (Japanese Patent Laid-Open No. 63-59337), but in the acidic to weakly alkaline state, the generated silica precipitates in a gel form.
The pH had to be adjusted to 13-14 and the silica had to be Na ₂ SiO ₃ (sodium metasilicate), which required a large amount of caustic soda.

In order to solve this, a method of treating the resulting silica gel with calcium hydroxide at pH 9.5 to 10.5 has been proposed (JP-A-63-214321). However, these methods have a problem that impact ignitable substances are produced when the wastewater is finally neutralized and adjusted (pH 6 to 8.5) and discharged. The present inventors previously proposed in Japanese Patent Application No. 63-82356 the treatment of by-product polychlorosilane with a hydroxide of alkaline earth metal or ammonia at pH 7-14. However, in the case of a gas containing dichlorosilane, it has been found that when the pH at the end of the treatment is adjusted to 6 to 8.5, neutralization adjustment of waste water is not necessary and no impact ignition material is generated.

[Problems to be Solved by the Invention]

INDUSTRIAL APPLICABILITY The present invention solves the problem of impact ignitability of a solid produced by the treatment reaction of dichlorosilane and enables safe treatment of dichlorosilane.

[Means for Solving the Problems]

The present invention relates to a method for treating a dichlorosilane-divided gas by contacting it with a hydroxide or oxide of an alkaline earth metal, wherein the pH at the end of the contact treatment is 6 to 8.5. Is.

As the alkaline earth metal hydroxide used in the present invention, calcium hydroxide and magnesium hydroxide are easy to handle, and as the alkaline earth metal oxide, calcium oxide and magnesium oxide are easy to handle. It is easier to operate the alkaline earth metal hydroxide or oxide prepared in advance as a saturated aqueous solution or slurry. The alkaline earth metal hydroxide or oxide used in the present invention is preferably in powder form for preparing a slurry.

The reason why the pH at the end of the contact treatment is limited to 6 to 8.5 is that when the treatment is terminated at a pH lower than 6, the solid matter produced has impact ignition properties and is ineffective. Also, the pH is 8.5
When the treatment is completed at a higher temperature than that, the reaction is too early to be completely inactivated and a shock-ignitable solid substance is produced during neutralization preparation (pH 6 to 8.5) when discharging the waste water.

The apparatus used for the treatment is not particularly limited, but the stirring tank type is easy to operate. The treatment method may be a batch method or a continuous method.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but these are merely examples and the present invention is not limited thereto.

Example 1 A 500 ml round-bottom glass flask was charged with 280 g of 15 wt% calcium hydroxide slurry, and the mixture was kept at 20 ° C. with stirring at 300 rpm. Dichlorosilane with a purity of 99.5% (the rest is monochlorosilane and trichlorosilane) is added to this.
The mixture was added dropwise for 1 minute, and stirring was continued for another 30 minutes. The pH of the liquid after the reaction was 7.9.

Thereafter, solid particles generated by the reaction were separated by filtration, washed with water, and dried under a nitrogen atmosphere. A drop-type impact tester (manufactured by Kamijima Seisakusho Co., Ltd.) was used to measure the impact ignition properties of the dried solid particles. The amount of impact given is displayed as the product of the weight (kg weight) of the weight dropped and the height (m) of the weight dropped. As a result of the measurement, even if a shock of 1.0 kg weight / m was given, it did not ignite.

Example 2 Under the same conditions as in Example 1, 220 g of 15 wt% magnesium hydroxide slurry was used instead of 280 g of 15 wt% calcium hydroxide slurry. There was no ignition in the flask during stirring. The pH after the reaction was 7.6. It did not ignite even when given an impact of 1.0 kg weight / m with an impact tester.

Example 3 Under the same conditions as in Example 1, the same procedure was performed using 212 g of 15 wt% calcium oxide slurry instead of 280 g of 15 wt% calcium hydroxide slurry. PH after reaction is 7.8
Met. It did not ignite even when given an impact of 1.0 kg weight / m with an impact tester.

Example 4 Under the same conditions as in Example 1, 280 g of 15% by weight calcium hydroxide slurry was replaced with 152 g of 15% by weight magnesium oxide slurry, and the same operation was carried out. The pH after the reaction is 6.
It was 8. It did not ignite even when given an impact of 1.0 kg weight / m with an impact tester.

Example 5 In a 500 ml glass round-bottomed flask, 15% by weight calcium hydroxide slurry was added at a rate of 9.3 g / min, and dichlorosilane having a purity of 99.5% (the rest being monochlorosilane and trichlorosilane) at a rate of 1.0 g / min. It was added dropwise and supplied at 300 rpm with stirring. Thirty minutes after the start of dropping, the slurry-like reaction liquid was extracted at a rate of 10.3 g / min and continuously treated for 3 hours. The solid particles generated by the reaction were separated by filtration, washed with water, dried under a nitrogen atmosphere, and measured by an impact tester. It did not ignite even when given an impact of 1.0 kgf ・ m.

Comparative Example 1 Under the same conditions as in Example 1, the pH of the liquid after the reaction was 5.0.
And dichlorosilane were added to reach 1.5 and 1.5. The solid particles produced by the reaction were separated by filtration, washed with water, and then dried under a nitrogen atmosphere, and the impact ignition properties of the solid particles were measured.
Ignition occurred at 0.9 and 0.6 kg weight / m.

Comparative Example 2 Under the same conditions as in Example 1, the pH of the liquid after the reaction was 10.2.
Dichlorosilane was added until When the pH was adjusted to 7.5, gel-like solid particles were produced. This was separated by filtration, washed with water, dried under a nitrogen atmosphere, and the impact ignitability of the solid particles was measured.

Comparative Example 3 Under the same conditions as in Example 1, the same procedure was carried out using 151 g of a 15 wt% sodium hydroxide aqueous solution instead of the 15 wt% calcium hydroxide slurry. The pH of the liquid after the reaction is 13.2
It was. The solid particles produced when the pH was adjusted to 7.2 were separated by filtration, washed with water and dried in a nitrogen atmosphere, and the impact ignitability of the solid particles was measured.

〔The invention's effect〕

According to the present invention, a gas containing dichlorosilane can be safely treated.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B01D 53/34 ZAB

Claims (1)

[Claims] 1. A method of treating a dichlorosilane-containing gas by contacting it with a hydroxide or oxide of an alkaline earth metal, wherein the pH at the end of the contact treatment is 6 to 8.5. .