JPH06321957A - Production of trialkoxysilane - Google Patents

Abstract

PURPOSE:To provide a production method of a trialkoxysilane having high metal silicon conversion ratio, suppressing discharge of industrial waste by the unreacted metal silicon, having improved environmental aspect and excellent efficiency. CONSTITUTION:Metal silicon is reacted with a 1-4C alkyl alcohol in the presence of a catalyst and aluminum and/or an aluminum compound except an aluminum- based impurity contained in the metal silicon to produce a trialkoxysilane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an efficient method for producing trialkoxysilane useful as a raw material for silane coupling materials and the like.

[0002]

2. Description of the Related Art Alkoxysilanes are useful as various silane coupling agents and raw materials for insulating thin films. Trialkoxysilanes have SiH bonds in their molecules.
Moreover, since it is chemically more stable than monoalkoxysilane and dialkoxysilane, there is a demand for a highly costly and efficient production method.

Conventionally, as a method for producing trialkoxysilane, a method using chlorosilanes and lower alkyl alcohols as raw materials has been known. However, chlorosilanes are expensive and, in addition to the desired alkoxysilane, hydrochloric acid. As a by-product, it is difficult to purify the product, and the reaction apparatus is corroded.

On the other hand, a method called a direct method for reacting metallic silicon with an alkyl alcohol is known, and this method is carried out in a gas phase or a liquid phase in the presence of a copper catalyst, for example. This reaction can be said to be an industrially and economically advantageous method because the target trialkoxylane can be produced by a one-step reaction, but there is a big problem that the silicon conversion rate is low, and a large amount of unreacted metallic silicon is generated. Since it is discharged as industrial waste, there is an environmental problem.

[0005]

In view of the above problems, the present inventors have a high conversion rate of metallic silicon, reduce the amount of unreacted metallic silicon, and suppress the discharge of industrial waste. ,
The present invention has been completed as a result of earnest research on a method for producing trialkoxylane which is also improved in terms of environment.

[0006]

According to the present invention, when a trialkoxysilane is produced by reacting metallic silicon with an alcohol having 1 to 4 carbon atoms, the reaction is carried out in the presence of aluminum and / or an aluminum compound. And a method for producing trialkoxysilane.

The metallic silicon used as one of the raw materials in the method of the present invention is not particularly limited, but one having a purity of 80% by weight or more is preferable. Further, the type and amount of impurities contained in the metallic silicon are not particularly limited, and for example, Al, Fe, Ca, etc. may be contained up to 1% by weight as impurities.
Alternatively, it may be washed with hydrofluoric acid or the like.

The shape of metallic silicon is preferably granular, and the particle size is not particularly limited, but usually the average particle size is 2 mm.
The following is preferable, and the average particle diameter is more preferably 25 to 500.
μm, and particularly preferably, the average particle size is 50 to 300 μm.

The lower alkyl alcohol, which is another raw material, may be linear or branched, and specifically, methanol, ethanol, n-propanol, iso-propanol, n-butanol, There are sec-butanol, iso-butanol, and tert-butanol, methanol and ethanol are preferable, and among these, ethanol is particularly preferable.

Lower alkyl alcohol has a purity of 95% by weight.
The above is preferable, and it is preferable that the water content is reduced to 2000 ppm or less, more preferably 500 ppm or less by treating with a dehydrating agent.

The supply rate of the lower alkyl alcohol to the reaction system is preferably 10 to 1,000 mmol / hr of the lower alkyl alcohol, and more preferably 50 to 500 mmol / hr, to 1 mol of metal silicon. 1,00
If it exceeds 0 mmol / hr, the amount of unreacted lower alkyl alcohol increases and the conversion rate of metal silicon decreases, which is not economical, and if it is too small, the conversion rate of metal silicon may decrease.

The lower alkyl alcohol may be supplied alone or diluted with a diluent gas and supplied. The diluent gas is not particularly limited as long as it does not react with the raw material or trialkoxysilane, and for example, nitrogen,
Examples thereof include argon and hydrogen.

As the catalyst in the present invention, any of commonly used catalysts such as a copper catalyst, a zinc catalyst and a nickel catalyst can be used and is not particularly limited, but a copper catalyst is particularly preferable. Specific examples include cuprous chloride, cupric chloride, copper bromide, copper iodide, copper fluoride, copper carbonate, copper sulfate, copper acetate, copper oxalate, copper thiocyanate, and the like, or hydroxide salts. Examples thereof include copper-containing inorganic compounds such as cuprous, cupric hydroxide, copper cyanide, copper sulfide, and copper oxide, organic copper compounds such as methyl copper and ethyl copper, or metallic copper.

Of the above, cuprous chloride is more preferable, and cuprous chloride produced by a wet method (hereinafter referred to as wet-type cuprous chloride) is particularly preferable.

The wet process cuprous chloride is cuprous chloride produced by crystallizing cuprous chloride in a solvent, separating and drying. Specifically, for example, copper pieces are added to an aqueous solution of cupric chloride to be crystallized as cuprous chloride, which is separated by drying and then produced, or copper sulfate, hydrochloric acid, copper and The cuprous chloride produced by the dissolution reaction with sodium chloride is crystallized, and after separation,
Examples include those produced by drying. This wet process cuprous chloride is clearly distinguished from cuprous chloride produced by the dry process, that is, cuprous chloride produced using metallic copper and chlorine gas as raw materials.

The purity of the catalyst is preferably 90% by weight or more.
If it is less than 90% by weight, the conversion rate of metallic silicon may be lowered.

The particle size of the catalyst is preferably less than 40 μm, more preferably less than 2 μm. When it is 40 μm or more, the reaction rate may be lowered, which also leads to a decrease in the conversion rate of metallic silicon.

The particle size of the catalyst can be adjusted freely depending on the production conditions, but if it is too fine, the efficiency of the crystallization and drying steps in the production process will be poor, and the surface of the particles will be deactivated by heat, moisture, etc. Therefore, as a particularly preferable method, the particle size of wet-type cuprous chloride is set to 20 μm.
A method of pulverizing to a particle size of less than 2 μm with a ball mill or the like after manufacturing the product to have a particle size of m or more is mentioned. The crushing is preferably carried out in air having a low water content, more preferably in nitrogen.

The catalyst is generally supplied to the reaction system separately from metallic silicon, but the catalyst may be mixed with metallic silicon in advance, or metallic silicon supported on the metallic silicon may be supplied. You may.

The catalyst is preferably activated together with metallic silicon and supplied to the reaction system. The activation method is 100
C. to 600.degree. C., particularly preferably 130.degree. C. to 230.degree. C., is preferable. If the temperature is lower than 100 ° C., it takes time to activate and cannot be said to be efficient. If the temperature exceeds 600 ° C., the catalytic action may be deactivated. Also activation is
Taking the case of a liquid phase reaction as an example, it may be carried out before addition to the solvent or may be carried out in the solvent while normally blowing an inert gas.

The amount of the catalyst used is preferably 0.5 to 50 parts by weight, more preferably 5 to 30 parts by weight, based on 100 parts by weight of metallic silicon. If it is less than 0.5 parts by weight or more than 50 parts by weight, both of them may lead to a decrease in silicon conversion rate.

In the present invention, in addition to aluminum-based impurities present as impurities in metallic silicon, aluminum and / or aluminum compounds (hereinafter simply referred to as aluminums) to be present in the reaction system are metallic aluminum, Aluminum metal such as aluminum alloy with Si, Mg and Ca, aluminum halide such as aluminum chloride, aluminum bromide, aluminum fluoride and aluminum iodide, aluminum salt such as aluminum carbonate and aluminum sulfate, aluminum hydroxide and aluminum sulfide. And aluminum-containing inorganic compounds such as aluminum acetate, aluminum oxalate, trialkoxyaluminum, and other aluminum-containing organic compounds, and particularly aluminum metal such as aluminum metal and aluminum alloy. It is preferred. The aluminums may be used alone or in combination of two or more.

The amount of aluminums is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 2 parts by weight, based on 100 parts by weight of metallic silicon. If it is less than 0.01 parts by weight or more than 10 parts by weight, the silicon conversion rate may decrease.

When the aluminum is an aluminum alloy, the content of aluminum is preferably 50% by weight or more, more preferably 85% by weight or more.

Aluminum may be supplied to the reaction system alone, or may be supplied as a mixture with metallic silicon or a catalyst.

The reaction of the present invention can be carried out in a gas phase or a liquid phase, but the liquid phase is particularly preferable. Hereinafter, the present invention will be specifically described by taking a liquid phase reaction as an example.

The reactor may be of any shape as long as the metallic silicon is kept in a good dispersed state. An external jacket for cooling or heating may be provided outside the reactor, and fins may be provided inside the reactor to improve heat transfer.
It may be provided with a coil or the like. Usually, the reactor is equipped with a pipe for supplying a silicon raw material as a reaction raw material and an alcohol, a discharge pipe for a reaction liquid containing the produced trialkoxysilane as a main component and containing other by-produced silicon compounds and unreacted alcohol, and a reaction liquid. It is equipped with a discharge port for the remaining residue. Further, as the material of the reactor, a quartz tube, a glass tube, a metal tube or the like can be used and is not particularly limited.

The reaction system may be either a batch system in which the entire amount of metallic silicon and the catalyst are initially charged, or a continuous system in which the metal silicon and the catalyst are continuously supplied during the reaction.

When carried out in the liquid phase, a solvent is used. The solvent is not particularly limited as long as it is an inert one that does not react with metallic silicon, a catalyst and trialkoxysilane, but a solvent having a high boiling point and stable is preferable. For example, paraffin hydrocarbons such as octane, decane, dodecane, tetradecane, hexadecane, octadecane, eicosane, diethylbenzene, trimethylbenzene, cymene,
Butylbenzene, butyltoluene, octylbenzene,
Alkylbenzene hydrocarbon such as dodecylbenzene or its hydride, diphenyl hydrocarbon such as diphenyl, diphenyl ether, monoethyldiphenyl, diethyldiphenyl, triethyldiphenyl or its hydride, alkylnaphthalene hydrocarbon or its hydride, triphenyl Hydrocarbon or its hydride etc. are mentioned. Of these, alkylbenzene hydrocarbons are preferable, and dodecylbenzene hydrocarbons are particularly preferable. These solvents may be used alone or in combination of two or more.

A suitable ratio of metallic silicon to the solvent is preferably 0.1 kg to 1 kg of metallic silicon, and more preferably 0.3 kg to 0.7 kg, per liter of the solvent.

The reaction temperature of the present invention is preferably 100 ° C to 300 ° C, particularly preferably 150 ° C to 230 ° C.
If it is less than 100 ° C, the conversion rate of metallic silicon may be lowered, and if it exceeds 300 ° C, the lower alkyl alcohol may be decomposed by contact with metallic silicon and the catalyst to cause deactivation of the catalyst.

The reaction of the present invention may be carried out at atmospheric pressure, elevated pressure or reduced pressure, but atmospheric pressure is preferred from the viewpoint that the apparatus is simple and economical and advantageous.

The trialkoxysilane obtained in the present invention has an alkoxy group corresponding to the lower alkyl alcohol used as a raw material. Specifically, trimethoxysilane, triethoxysilane, tri-n-propoxysilane, Triisopropoxysilane, tri-n-butoxysilane, tri-sec-butoxysilane, triisobutoxysilane, tri-tert-butoxysilane and the like can be mentioned, and more preferable examples of the trialkoxysilane produced in the present invention are Trimethoxysilane and triethoxysilane, with triethoxysilane being most suitable.

The reaction product solution according to the present invention contains a high concentration of trialkoxysilane, and also contains tetraalkoxysilane and other side reaction products and unreacted alcohol. It can be easily separated and obtained from this reaction product liquid by distillation or another conventional method.

The reaction solvent after the trialkoxysilane is separated and obtained is in the form of a reddish brown slurry due to the copper powder produced during the reaction and the unreacted metallic silicon, but according to the method of the present invention, the unreacted metallic silicon is used. The reaction residue is small and can be easily separated by filtration or centrifugation. Most of the separated solid content reaction residue is copper powder, and the amount of unreacted metallic silicon is very small. The solvent recovered by filtration can be reused.

[0036]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples. The selectivity of trialkoxysilane and the conversion rate of metal silicon in the present specification are values calculated by the following formulas. Trialkoxysilane selectivity (mol%) = [(mol of trialkoxysilane) / (mol of trialkoxysilane + mol of tetraalkoxysilane)] × 100 Metallic silicon conversion (wt%) = 100 -[(Weight of metallic silicon in reaction residue) / (weight of charged metallic silicon)] x 1
00

Example 1 A 500 ml glass reactor equipped with a raw material blowing pipe, a thermometer, a stirrer, a cooler and a cooling liquid outlet was charged with 300 ml of dodecylbenzene as a solvent, and metallic silicon (silicon content 99.8% by weight). , Aluminum content 0.38% by weight, iron content 0.43% by weight average particle size 100 μm)
150 g, wet method cuprous chloride (purity 95%) 15 g and aluminum powder 1 g were charged. Next, while supplying nitrogen (30 ml / min), stirring and mixing at 200 ° C.
The catalyst was activated by heating for 10 hours. In addition,
As the above wet method cuprous chloride, after copper sulfate, hydrochloric acid, copper and sodium chloride are dissolved and reacted to crystallize cuprous chloride,
This is separated and dried to obtain solid cuprous chloride, and the particle size is 0.06 to 1.
The one having a size of 48 μm was used.

Then, the temperature of the reactor was kept at 180 ° C.,
While stirring and mixing, while supplying nitrogen (30 ml / mi
n), 50 g / hr of vaporized ethanol from the blowing tube
Was fed into the solvent and reacted.

Five minutes after the start of the reaction, the product solution started to distill out from the cooler. The composition of the product solution that distilled out was analyzed by gas chromatography, and the change with time of the composition was observed. The reaction was terminated when the composition of ethanol reached 100%.

After 23 hours from the start of the reaction, the reaction was completed and a reaction product liquid containing the target product, triethoxysilane, was obtained. Table 1 shows the analysis results of the composition of all the obtained product solutions, and the triethoxysilane selectivity and silicon conversion rate based on the analysis results.

[0041]

[Table 1]

The content of the reactor after the trialkoxysilane was separated and obtained was in the form of a reddish brown slurry, the solid content reaction residue obtained by filtration was mostly copper powder, and the amount of unreacted silicon was very small. The solvent collected by filtration was colorless and transparent and could be reused.

Example 2 Instead of aluminum powder, aluminum silicon (Si
The reaction was performed in the same manner as in Example 1 except that 1 g of the content rate of 10 wt%) was used. The reaction was completed in 31 hours.

Table 1 shows the analysis results of the composition of all the obtained product solutions, and the triethoxysilane selectivity and silicon conversion rate based on the analysis results.

Example 3 A reaction was carried out in the same manner as in Example 2 except that the amount of aluminum silicon used was 0.5 g. The reaction was completed in 23 hours.

Table 1 shows the analysis results of the composition of all the obtained product liquids, and the triethoxysilane selectivity and silicon conversion ratio based on the analysis results.

Comparative Example 1 The reaction was carried out in the same manner as in Example 1 except that aluminum powder was not added. The reaction was completed in 23 hours.

Table 1 shows the analysis results of the composition of all the obtained product liquids, and the selectivity of triethoxysilane and the conversion rate of metal silicon based on the analysis results.

[0049]

INDUSTRIAL APPLICABILITY According to the present invention, when a trialkoxysilane is produced by reacting metallic silicon with an alcohol having 1 to 4 carbon atoms in the presence of a catalyst, aluminum other than aluminium-based impurities contained in metallic silicon or / And the presence of an aluminum compound, the conversion rate of metallic silicon is high. Therefore, the amount of unreacted metallic silicon is reduced, the emission of industrial waste is suppressed, and the environment-improved trialkoxy is improved. It is a method of manufacturing orchids.

Claims (1)

[Claims] 1. Metal silicon and a carbon number of 1 to 4 in the presence of a catalyst.
When a trialkoxysilane is produced by reacting the alkyl alcohol of 1., the reaction is carried out in the presence of aluminum or / and an aluminum compound other than aluminum-based impurities contained in metallic silicon. .