KR100716064B1 - Preparation method of tetraalkoxysilane from waste silicon - Google Patents

Abstract

The present invention relates to a method for producing a tetraalkoxysilane, and more particularly, to a method for producing a tetraalkoxysilane by reacting a discarded metal silicon with a lower alcohol, which is separated from waste in the presence of a high boiling potassium alkoxide catalyst, It relates to a method for producing a tetraalkoxysilane by reacting the recovered metal silicon with an alcohol such as methanol, ethanol at 175 ~ 210 ℃.

The method for producing tetraalkoxysilane according to the present invention can greatly suppress the production of alkoxysilanes such as trialkoxysilanes of the prior art, and can ultimately increase the yield of tetraalkoxysilane, the target compound, and silicon waste sludge. The silicon separated from can be recycled.

Waste sludge, magnetic screening, heavy liquid screening, silicone, alcohol, tetraalkoxysilane

Description

Preparation method of tetraalkoxysilane using waste silicon metal {Preparation Method of Tetraalkoxysilane from waste silicon}

1 is a silicon separation process in the waste silicon sludge according to the present invention

Figure 2 is a silicon alkoxide manufacturing process according to the present invention

The present invention relates to a method for producing a tetraalkoxysilane of the present invention, and more particularly, to a metal alcohol (Silicon), which is separated and recovered from waste in the presence of a high boiling alkali alkoxide catalyst, and low-cost alcohols such as methanol and ethanol. It relates to a method for producing tetraalkoxysilane by reacting at 210 ° C.

In the cutting process for making silicon wafers from silicon ingots, wire saws are generally used. In this case, a cutting slurry containing about 0.14 μm in diameter and silicon carbide having an average particle diameter of 20 μm is used. Doing. In this cutting process, waste sludge containing a large amount of silicon carbide, silicon particles, and cutting oil is produced, which has been landfilled by a waste disposal company until a few years ago.

Currently, silicon carbide and cutting oil with an average particle size of 20㎛ contained in this waste slurry are separated and recovered, and a facility that can be reused in the cutting process of silicon wafer is operated. Providing. However, the waste sludge remaining as a residue even in the case of such reuse is known as thousands of tons per year. The waste sludge contains silicon carbide with an average particle diameter of 5 μm or less, silicon metal with a low particle size, and oil-soluble oil. Therefore, the waste sludge can be effectively separated and recovered and reused or recycled as a useful resource. It is meaningful. In the case of effectively separating and recovering useful resources, silicon carbide can be used as a raw material for ceramics such as high temperature refractory materials or silica composites, and silicon powder can be used as a synthetic raw material for high purity silicon compounds.

In addition, a method for recycling waste cutting fluid for cutting wire saws has been developed. Known technology for the waste cutting fluid regeneration technology for cutting is the Korean Patent No. 0,385,177, which dilutes and mixes the coolant with a certain ratio before the waste sludge is introduced into the decanter and separates it by a decanter to separate sawdust and shredding. To ensure more efficient removal of the cutting agent, and to provide a means for adjusting the viscosity of the liquid phase by heating the temperature heating device during mixing supply, the filtrate from the primary decanter is recovered by recovering the coolant by the secondary decanter The coolant is characterized in that it is pressurized at all times to allow extrusion to be supplied during cleaning and mixing with the waste sludge. In addition, Korean Patent No. 0535808 is a technique for cleaning and separating the contaminated particles of waste sludge, and relates to a contaminant washing and separating apparatus for waste sludge, which is a suspension containing a large amount of oil generated in the pore and polishing process of the workpiece. The present invention relates to the effective separation of the cutting agent and the cutting oil contained in the waste sludge containing the cutting agent, the cutting oil and the fine particles.

Metal alkoxides were used as synthetic reagents or catalysts until the 1970s and were not received much attention industrially. However, since the 1970s, metal alkoxides have been used in ceramics and ceramics, and have recently been used as essential materials for precision ceramics as well as electronic materials. In particular, alkoxy silanes such as tetraethyl orthosilicate and tetramethyl silane are widely used as sol-gel optical fibers, starting materials for the synthesis of ceramics, and materials for forming semiconductor insulating films.

In 1846, Ebelmen synthesized tetraethoxysilane from silicon tetrachloride and ethanol to report on the first alkoxy silane synthesis reaction. Since 1920, many studies on the reaction mechanism and physical properties of various metal alkoxides including alkoxy silane have been conducted. . Various methods of synthesizing alkoxy silane are known, such as 1) reaction of silicon chloride and alcohol, 2) reaction of metal silicon and alcohol, 3) reaction of silicon hydroxide or oxide and alcohol, and 4) exchange of alcohol.

At present, the most widely used method for the production of alkoxysilanes is a method for preparing by reacting tetrachloride silane with an alcohol. However, the method requires a device of a special material to prevent this by the corrosion of the production apparatus by the hydrogen chloride by-produced, there is a disadvantage in that a large cost is required for its removal and disposal. In order to overcome this problem, a method of preparing a tetraalkoxysilane by reacting a metal silicon powder with a lower alcohol using a copper catalyst has been proposed, but in this reaction, a trialkoxysilane and other silicone derivatives as well as tetraalkoxysilane as a target compound are proposed. Produced together, there are disadvantages in that a disilane compound having a high molecular weight and a high boiling point is also produced. And the reaction of silicon metal or oxide with alcohol needs to optimize these factors to obtain high temperature, high pressure, large surface area of metal and substantial fast reaction rate. In addition, the silicon alkoxide may be produced by the electrolytic method, but this method requires a lot of investment cost and operation cost, and there is a problem that separation of the product is difficult.

In order to improve the production efficiency of such tetraalkoxysilane, a method using metal copper or a compound thereof has already been disclosed. For example, US Pat. Nos. 4,289,889 and 4,762,939 use a copper catalyst and a special type of solvent to react in a liquid phase, or US Pat. No. 4,447,632 uses alkali metal carbonate as a high pressure reaction catalyst. Or US Pat. Nos. 4,211,717 and 4,752,647 disclose methods for reacting in a liquid phase using an alkali metal or alkali metal alkoxide as a catalyst and using a special type of solvent.

It is claimed that the purity of the tetraalkoxysilane can be improved by the direct synthesis method, but it is required that a high-pressure reaction vessel is required under high pressure, or that various alkoxysilanes such as trialkoxysilane are simultaneously produced and that a continuous process is impossible. There is such a problem. In addition, the silicon metal used is made of high-purity metal silicon, and the method using waste silicon is not mentioned.

Accordingly, the present invention has been made to solve the above problems,

The raw material of silicon was used as a sample of the silicon separated and recovered from the sludge generated during the cutting process of the silicon wafer, which is a semiconductor manufacturing waste. The purpose of the present invention is to increase the reaction rate of alkoxysilane and selectivity to tetraalkoxysilane by adopting a catalyst that can increase the conversion rate to silane and ultimately increase the yield of tetraalkoxysilane.

Method for producing a tetraalkoxysilane using the waste silicon metal of the present invention for achieving the above object,

In the method for producing a tetraalkoxysilane using waste silicon metal,

A dissolving process of dissolving and cutting the cutting oil by mixing 2 to 3 v / v% of an organic solvent with a mixture of cutting oil, silicon and silicon carbide, which are waste sludges generated in the cutting process of the silicon ingot; A magnetic screening process for removing iron, which is an impurity, from the residue by magnetic screening; A heavy liquid sorting process for separating high purity silicon through a heavy liquid sorting of a mixture of silicon and silicon carbide; separating the recovered silicon from the waste,

In the presence of a high boiling potassium alkoxide catalyst, recovered silicon separated from the waste is prepared by reacting with lower alcohol at 175-210 ° C.

High boiling alcohols used in the preparation of the potassium alkoxide catalyst, 2-2-butoxyethoxy ethanol (2--2-butoxyethoxy ethanol), 2-butoxyethanol (2-butoxyethanol), diethylene glycol (diethylene glycol), Diethylene glycol ethyl ether (diethylene glycol ethylether), 2-ethoxyethanol (2-ethoxyethanol) from the group consisting of single or two or more mixed use,

The lower alcohol is used alone or in combination of two or more from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol and tertiary butanol.

The optimum reaction temperature of the recovered silicon and lower alcohol is 180 to 195 ° C.

The organic solvent is used alone or two or more selected from the group consisting of methanol, ethanol, propanol, butanol, normal nucleic acid, acetone and ether, the organic solvent used for the selection of the heavy liquid is a mixture of tetrabromoethane and acetone with a specific gravity of 2.8 It is characterized by.

Hereinafter, a method for producing tetraalkoxysilane using waste silicon metal according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows a flow chart for oil-soluble oil separation, iron removal, and the separation and recovery of silicon and silicon carbide from the waste slurry according to the present invention. Figure 2 shows a silicon alkoxide manufacturing process according to the present invention. Each process is briefly described below.

Synthesis of the alkoxy silane is first performed by the reaction of the metal silicon recovered and recovered from the slurry with the potassium alkoxide, which is a catalyst, and alkoxysilane synthesis by high boiling alkoxy silane and low boiling alcohol. It consists of a step reaction. Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.

Example  One

Oil-soluble oils have a high boiling point and have a high energy cost in order to separate and recover them by distillation, and deterioration may occur due to high processing temperatures. Therefore, a separation method using an organic solvent which can be mixed well with oil-soluble oil was used. That is, a large amount of acetone or dichloromethane (CH ₂ Cl ₂ ) was mixed with the waste slurry and vigorously stirred to selectively dissolve the oil-soluble oil from the waste slurry. The solid phase and the liquid phase separated the solid silicon, silicon carbide and the liquid oil-soluble oil by filtration and centrifugation.

Acetone and dichloromethane 260 ml were added to 100 g of silicon cut waste sludge, followed by vigorous stirring for 3 hours, and the filtrate and residue were separated by filtration. The filtrate was distilled to remove dichloromethane to separate and recover the oil-soluble oil.

Waste oil from which oil-soluble oil is removed contains a large amount of iron in addition to silicon and silicon carbide. This iron is produced by the friction of the wire saw and silicon, and its amount varies depending on the generation state of the sample and the post-treatment state. Therefore, iron in the solid-phase mixture from which oil-soluble oil was separated and removed was separated using a magnetic separator with a magnetic flux density of 500 gauss.

The specific gravity of the metal silicon is 2.33 g / cm ³ , and the specific gravity of the silicon is 3.23 g / cm ³ . Therefore, the middle liquid screening was performed using the specific gravity of tetra bromoethane and acetone mixture as 2.8. The silicon and silicon carbide obtained by the solid solution was washed with a large amount of acetone and used as a sample for analysis. The washed solvent was fractionally distilled and reused.

Waste sludge is not always released as a constant component, and depending on the sampling conditions, the amount of oil, silicon and silicon carbide can vary significantly. Table 1 summarizes the results of oil soluble oil removal, iron removal, and the separation and recovery of silicon and silicon carbide from silicon ingot-cut waste sludge. The purity of silicon was over 96% and the recovery was about 90%.

Table 1 Separation of Silicon and Silicon Carbide from Silicon Ingot Cutting Sludge

Example  2

500 ml three-necked flask reactor with 2.0 mol (324.4 g) of 2-2-butoxyethoxy ethanol, a high boiling alcohol, and 1.0 mol (65.4 g) of 50 mL of toluene and granular KOH Potassium alkoxide catalyst was synthesized by reflux with vigorous stirring at 180 ° C. under nitrogen atmosphere for about 2.5 hours. At this time, the water contained in the resulting catalyst was removed 24 ml of water by azeotropic distillation using toluene. The residual toluene was also distilled off. As the high boiling alcohol, in addition to 2- (2-butoxyethoxy) ethanol, alcohols such as 2-butoxyethanol, diethylene glycol and diethylene glycol ethylether can be used. .

Example  3

The reactor for the synthesis of alkoxy silane was attached to a 250 ml round bottom three-necked flask with a rubber stopper, a Teflon vane stirrer, a distillation set, three sets of 50 ml containers, a thermometer, and a hydrogen produced by installing a wet test meter. The volume of was measured.

In the synthesis reaction, 10 g of the catalyst synthesized above was added to 0.2 mol (5.6 g) of 96% silicon powder in a nitrogen atmosphere, and reacted at 180 ° C. until hydrogen generation stopped. When hydrogen evolution stopped, alcohol (ethanol / methanol) was injected under the surface of the reaction liquid at a rate of 0.33 ml / min using a metering pump, and the reaction temperature was reacted in the range of 175 to 210 ° C. At the same time, the reaction product tetraalkoxysilane was continuously distilled with ethanol or methanol, cooled in a condenser, collected in 30-minute increments, and subjected to qualitative and quantitative analysis by gas chromatography.

Example  4

By the method described in Example 3, the yield of tetraethoxysilane according to the amount of potassium alkoxide added as a catalyst was measured at 180 ° C. The amount of catalyst per 0.2 mol of Si was added 5, 10, 20, 30g, the yield of tetraethoxysilane was changed according to the amount of catalyst added. When the amount of the catalyst was 10 g, the highest value was obtained with a production rate of tetraethoxysilane of 60%.

Example  5

By the method described in Example 3, the effect of the reaction temperature on the yield was examined at intervals of 5 ° C in the reaction temperature range of 185 ° C to 205 ° C. As the reaction temperature increases, the yield is increased and shows the highest value at 195 ° C. However, if the temperature is higher than that, the yield is falling. Therefore, the optimum reaction temperature is determined to be 195 ℃. In addition, as a result of gas chromatography analysis of the product fractionated by the reaction time at the optimum reaction temperature of 195 ° C., a small amount of tetraethoxysilane was formed until 30 minutes after the start of the reaction, and a peak of the reaction by-product was observed. Therefore, it can be seen that the peak of the impurities disappears and only tetraethoxysilane is produced. That is, a small amount of TEOS is produced by 30 minutes, but the amount of tetraethoxysilane produced is increased from 30 minutes, showing the highest value at 150 minutes, and then gradually decreasing. After reacting for 6 hours, the yield of tetraethoxysilane was 60%.

Example  6

The effect of reaction temperature on the yield of tetramethoxysilane was examined by the method described in Example 5. In the tetramethoxysilane synthesis reaction, the higher the reaction temperature, the higher the yield, and the highest yield is obtained at 180 ° C. The higher the temperature, the higher the yield, the higher the yield, it is determined that the optimum reaction temperature is 180 ℃. After the reaction for 6 hours, the yield of tetramethoxysilane was 88%, it can be seen that the production rate of tetramethoxysilane is faster than the production rate of tetraethoxysilane of Example 5. Lower alcohols may use alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol and tertiary butanol.

In addition, the above-mentioned example is only an example to demonstrate this invention. Therefore, it is obvious that the ordinary skilled in the art to which the present invention pertains uses the partial change with reference to the detailed description.

As described above, the method for producing tetraalkoxysilane using the waste silicon metal of the present invention,

The sample separated and recovered from the sludge generated during the cutting process of the silicon wafer, which is a semiconductor manufacturing waste, was used as a sample. It is possible to provide a useful method for improving the recycling of waste silicon by increasing the reaction rate of the alkoxysilane and the selectivity to the tetraalkoxysilane by adopting a catalyst that can ultimately increase the yield of the tetraalkoxysilane by increasing the yield. It is.

Claims (4)

In the method for producing a tetraalkoxysilane using waste silicon metal, A dissolving process of dissolving and cutting the cutting oil by mixing 2 to 3 v / v% of an organic solvent with a mixture of cutting oil, silicon and silicon carbide, which are waste sludges generated in the cutting process of the silicon ingot; A magnetic screening process for removing iron, which is an impurity, from the residue by magnetic screening; A heavy liquid sorting process for separating high purity silicon through heavy liquid sorting of a mixture of silicon and silicon carbide; separating recovered silicon from the waste; In the presence of a high boiling potassium alkoxide catalyst, the recovered silicon separated from the waste is prepared by reacting with lower alcohol at 175 ~ 210 ℃, High boiling alcohols used in the preparation of the potassium alkoxide catalyst, 2-2-butoxyethoxy ethanol (2--2-butoxyethoxy ethanol), 2-butoxyethanol (2-butoxyethanol), diethylene glycol (diethylene glycol), Diethylene glycol ethyl ether (diethylene glycol ethylether), 2-ethoxyethanol (2-ethoxyethanol) from the group consisting of single or two or more mixed use, The lower alcohol is a method for producing tetraalkoxysilane using waste silicon metal, characterized in that used alone or in combination of two or more from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol and tertiary butanol. . The method of claim 1, The reaction temperature of the recovered silicon and lower alcohol is a method for producing tetraalkoxysilane using waste silicon metal, characterized in that 180 ~ 195 ℃. The method of claim 1, The organic solvent is methanol, ethanol, propanol, butanol, normal nucleic acid, acetone and ether selected from the group consisting of one or more selected from the group consisting of tetraalkoxysilane using waste silicon metal, characterized in that used. The method of claim 1, The organic solvent used for the selection of the heavy liquid is tetrabromoethane and acetone mixture, specific gravity of 2.8 The method for producing tetraalkoxysilane using waste silicon metal, characterized in that.

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