CN110172072B

CN110172072B - Method for removing chloride from alkoxy silane

Info

Publication number: CN110172072B
Application number: CN201910560871.1A
Authority: CN
Inventors: 王度; 叶丹; 李钊
Original assignee: Jiangxi Bluestar Xinghuo Silicone Co Ltd
Current assignee: Jiangxi Bluestar Xinghuo Silicone Co Ltd
Priority date: 2019-06-26
Filing date: 2019-06-26
Publication date: 2022-03-04
Anticipated expiration: 2039-06-26
Also published as: CN110172072A

Abstract

The invention relates to a method for removing chloride from alkoxy silane, which comprises the following steps: adding transition metal chloride into the crude product of the alkoxy silane, mixing, performing a first heating stage, performing a second heating stage at a higher temperature, simultaneously adding a cationic surfactant, performing heat preservation reflux reaction, cooling after the reaction is finished, adding a lower alcohol solution of lower sodium alkoxide for neutralization, and rectifying to obtain the alkoxy silane product with low chlorine content. The content of alkoxy silane chlorine after the treatment of the method is as low as below 3.2ppm, the conductivity is as low as below 0.52 mu s/cm, the hue index is below APHA30, the yield is high, and the product loss rate is small. The treatment method is simple and convenient, has low cost, does not relate to flammable, explosive or toxic chemical reagents in the treatment process, does not have potential safety hazard, and is an industrial alkoxy silane refining method worthy of commercial popularization.

Description

Method for removing chloride from alkoxy silane

Technical Field

The invention relates to the field of organic silicon, in particular to a method for removing chloride from alkoxy silane, and particularly relates to a method for removing chloride from alkoxy silane used in the electronic and electrical industry.

Background

The alkoxy silane has large demand in the electronic and electrical industry and very strict purity, and particularly, if the alkoxy silane contains chloride, the alkoxy silane has high corrosivity and causes corrosion to equipment and pipelines, and the chloride ion is high, so that the conductivity of the product is high and the like, so that the chloride in the alkoxy silane needs to be removed in time. At present, the common removal method is neutralization by a neutralizer, and a distillation method is used for separating nonvolatile components, but the method cannot remove nonionic chlorine, obviously increases the hue index of a product after treatment, and the like, and limits the application in the electronic and electric fields. At present, the method for producing methyltrimethoxysilane in domestic industry mainly adopts a sodium methoxide secondary reaction removal method, and comprises the following specific steps:

1. neutralizing crude methyltrimethoxysilane generated by the reaction with sodium methoxide, and then distilling to obtain a pure methyltrimethoxysilane product, wherein the purity is generally more than 99.5 percent, and the content of non-hydrolytic chlorine is generally more than 200 ppm;

2. adding the pure methyltrimethoxysilane into a reaction kettle, adding 1.5% of silver nitrate methanol solution, refluxing, heating and reacting for 1h, adding sodium methoxide for neutralization, and rectifying to obtain the pure methyltrimethoxysilane, wherein the chlorine content in the pure methyltrimethoxysilane can generally reach about 50 ppm.

However, when the sodium methoxide is used industrially, the method has the disadvantage of significant decomposition of the product, and the yield is reduced and the by-products are increased due to the formation of tetramethoxysilane during the combination of methyltrimethoxysilane and sodium methoxide; further, the use of sodium methoxide neutralizer tends to increase the silicone color index after treatment.

The prior journal literature and the technical contents disclosed in the patents of all countries can explain the current situation of removing chloride in alkoxy silane.

Non-patent documents disclose a treatment method using lithium aluminum hydride, dibutyltin and a 50% sodium metal suspension (Journal of organic chemistry, vol.265, 135-.

German patent 1530673 discloses the preparation of aminoalkylalkoxysilanes by adding to the reaction mixture after the alkoxylation of the chlorohydrocarbyls an amount of sodium alkoxide equal to the chlorohydrocarbylalkoxysilane in the mixture. In EP 0282846A2, alkoxysilanes containing small amounts of chloride are treated with an excess of sodium alkoxide and reacted in an organic solvent, such as toluene, and then filtered to remove salts. In EP 0532872B1, alkoxysilanes are reacted with alcohols in a pressure vessel in the presence of an excess of neutralizing agent, under a pressure adjusted to be above the boiling point of the alcohol. The salt was separated off and the excess alcohol was decanted off. The neutralizing agent is NH₃Organic amines and sodium alkoxides. The above conditions are not suitable for chloroalkylalkoxysilanes due to NH₃Organic amines and sodium alkoxides can react with chlorocarbons. In the prior art, metal salt of sterically hindered amine or sodium sterically hindered alkoxide is used as a neutralizer, the treatment is carried out for 1-2h at the temperature of 80 ℃, acidic pollutants in alkoxy silane are removed, and then distillation is carried out. Chinese patent 102372733A discloses a continuous preparation method of methyltrialkoxysilane, which comprises alcoholysis of methyltrichlorosilane as pigment with fatty alcohol, neutralizing, and rectifying to obtain product, wherein the neutralizing agent is sodium methoxide, sodium ethoxide,Triethylamine and urea. In the prior art, a method for preparing chlorine-free alkoxy silane by reacting pure silicon with an alcohol compound is also provided, for example, in CN1935649A, triethoxy silane is prepared by using industrial silicon and ethanol as raw materials, the triethoxy silane is separated by adsorption or distillation purification, then the catalytic disproportionation is carried out to prepare monosilane, and then the monosilane is purified by an absorption or adsorption method. The patent avoids the introduction of halogen in the initial raw material stage, but the method has high cost and low yield, and only 150-250 g of triethoxysilane can be produced per kilogram of silicon, thus being not suitable for large-scale industrial production. Chinese patent CN102199168A discloses the synthesis of chloropropyltriethoxysilane, which uses a large amount of alcohol solvent in the chloride treatment process and uses a large amount of magnesium powder for neutralization. In the chinese patent 107522731a, aluminum trichloride is used as a dechlorinating agent, and aluminum powder is used as a neutralizer to treat methyltriethoxy to obtain a product with very low chlorine content. But a large amount of aluminum powder was used. Aluminum powder and magnesium powder belong to substances which are easy to burn in chemical industry, can emit a large amount of heat, and have serious potential safety hazard in use, so the aluminum powder and the magnesium powder are avoided to the greatest extent in chemical production.

In summary, the prior art methods for chloride removal from alkoxysilanes have several disadvantages. Currently, only European countries such as Germany have mastered their technology and can reduce the chlorine content in alkoxysilanes to below 20 ppm. Although China has already studied, the method basically maintains the content of the alkoxy silane chlorine at about 50ppm and has poor product quality due to great technical defects, so that the market share is small. Therefore, the development of a simple and efficient method for removing the chloride in the alkoxy silane has great research and development significance and commercial value.

Disclosure of Invention

In view of the above problems, it is an object of the present invention to provide a method for removing chloride from an alkoxysilane, which has a low chlorine content of 5ppm or less, preferably 3.2ppm or less, more preferably 2ppm or less, in the product after the treatment, and which has a high yield, a low product loss rate, a low hue of the alkoxysilane after the treatment, a low color degree of APHA30 or less, and a simple and convenient treatment. The above object of the present invention is solved by the following technical solutions:

a method for removing chloride from an alkoxysilane comprising the steps of:

adding transition metal chloride into the crude product of the alkoxy silane, mixing, performing a first heating stage, performing a second heating stage at a higher temperature, simultaneously adding a cationic surfactant, performing heat preservation reflux reaction, cooling after the reaction is finished, adding a lower alcohol solution of lower sodium alkoxide for neutralization, and rectifying to obtain the alkoxy silane product with low chlorine content.

The low chlorine content means that the chloride content in the system after the treatment is as low as 5ppm or less, preferably as low as 3.2ppm or less, more preferably as low as 2ppm or less.

The first heating stage is to heat up and evaporate the recovered methanol at 70-90 ℃ for 1-3 hours; and/or the second heating stage is heating reflux reaction, heating to 100-120 deg.C for 2-5 hr; and/or the temperature reduction is to reduce the temperature to 30-50 ℃.

The alkoxysilane is not particularly limited as long as it is an alkoxysilane obtained by alcoholysis of a chlorosilane with an aliphatic alcohol and falls within the scope of the present invention regarding the "alkoxysilane", and typical examples in industry include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, tetramethoxysilane, tetraethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and the like. In particular, in the electronic and electrical industry, methyltrimethoxysilane is used more frequently, and the content of chloride in the methyltrimethoxysilane is more strictly required. Therefore, the alkoxy silane to be removed from chloride in the embodiment of the present invention is methyl trimethoxy silane, but it should not be construed as limiting the scope of the present invention, and for other alkoxy silanes, similar effects can be achieved by the method for removing chloride provided by the present invention, and thus it is within the scope of the present invention.

The transition metal chloride is at least one selected from ferric chloride, cupric chloride, nickel chloride and cobalt chloride, and is preferably ferric chloride.

The amount of the transition metal chloride is 0.05-0.5%, preferably 0.1-0.3% of the mass of the alkoxysilane to be chloride-removed. The amount of the transition metal chloride should be within a suitable range to achieve the object of the invention to the optimum extent, and if the amount is too small, the chloride in the system cannot be removed effectively, and if the amount is too large, the color of the product is deepened, and the hue index is deteriorated.

The cationic surfactant is quaternary ammonium salt cationic surfactant, such as alkyl ammonium halide, aryl ammonium halide, alkyl aryl ammonium halide, and specific examples include, but are not limited to, at least one of octadecyl trimethyl ammonium chloride, hexadecyl dimethyl benzyl ammonium bromide, dodecyl dimethyl benzyl ammonium chloride, dodecyl dimethyl benzyl ammonium bromide, tetrabutyl ammonium chloride, and tetrabutyl ammonium bromide.

The cationic surfactant of quaternary ammonium salt is added for complexing with a small amount of dissolved metal ions in the crude product stored in the metal storage tank, so that the hue index of the system is reduced. The inventors have unexpectedly discovered that the addition of a quaternary ammonium salt cationic surfactant in an amount that, in addition to reducing the product hue index, also promotes a further reduction in the chloride content of the system to some extent. The reason may be that the formed metal complex has certain catalytic chlorosilane hydrolysis/alcoholysis activity, so that the chlorosilane which is not completely hydrolyzed by body weight is hydrolyzed or alcoholyzed, chlorine in high-boiling residues and nonvolatile impurities is converted into hydrogen chloride which is easy to neutralize and discharge, and the content of chloride in the system is further reduced.

The amount of the cationic surfactant is 0.01 to 0.1%, preferably 0.02 to 0.05% by mass of the alkoxysilane to be chloride-removed. The dosage of the cationic surfactant is too small, the hue index of the product cannot be effectively reduced, and the cationic surfactant cannot synergistically play a role in removing chloride with the transition metal chloride; the use of the cationic surfactant is excessive, and the removal of the chloride in the system is not facilitated.

The lower alcohol is aliphatic alcohol with 1-4 carbon atoms, preferably methanol, ethanol, propanol and butanol. In the lower alcohol solution of the lower sodium alkoxide, the alcohol of the lower sodium alkoxide and the alcohol of the lower alcohol solvent can be the same or different, and the aim of the invention is not affected. The lower sodium alkoxide is an alcoholic solution with the mass percent concentration of 20-50%, and preferably an alcoholic solution with the mass percent concentration of 30-40%. The amount of the lower sodium alkoxide solution used is 0.5 to 3%, preferably 1 to 2%, based on the mass of the alkoxysilane to be chloride-removed.

The neutralization is to change the pH of the solution from acidity to 9-11.

In the preferred technical scheme of the invention, alkoxysilane and anhydrous ferric trichloride powder are put into a reaction kettle, heated to 70-90 ℃ to evaporate methanol, then continuously heated to 100 ℃ and 120 ℃ to reflux for 1-3h, hexadecyl trimethyl ammonium chloride is added, heat preservation and reflux reaction are carried out for 1-2h, after the reaction is finished, the temperature is reduced to 30-50 ℃, 30-40 wt% of methanol solution of sodium methoxide is added to react for 0.5-1h, the pH of the crude product is neutralized to 9-11, and then rectification is carried out to obtain a low-chlorine methyltrimethoxysilane pure product; wherein the dosage of the anhydrous ferric chloride is 0.1-0.2% of the mass of the alkoxy silane, the dosage of the hexadecyl trimethyl ammonium chloride is 0.02-0.05% of the mass of the alkoxy silane, and the dosage of the sodium methoxide solution is 0.8-1.5% of the mass of the alkoxy silane.

The principle and process of the invention are as follows:

anhydrous ferric trichloride is reacted with crude alkoxy silane to convert non-hydrolyzed chlorine into free chloride, then a cationic surfactant is used for reaction to remove metal ions and the like which promote the color of the solution to become dark, and then methanol solution of sodium methoxide is further used for reaction with the crude product to remove hydrolyzable chlorine in the crude product. Taking methyltrimethoxysilane as an example, the specific process comprises the following steps:

(1) industrially, alkoxy silane is generally prepared by alcoholysis of chlorosilane and aliphatic alcohol, for example, methyltrimethoxy silane is prepared by reacting monomethyltrichlorosilane with methanol, and because industrial raw material monomethyltrichlorosilane contains a small amount of high-boiling-point substances which can not completely react under the reaction condition, the product contains chlorine which is not completely substituted; the ferric trichloride is complexed with unsubstituted chlorine (methyl dimethoxy chlorosilane, dimethyl methoxy chlorosilane, trimethyl chlorosilane and the like) in the crude product, the boiling point of heavy metal salt is very high, so that the complex chlorine is very stable, and when the product is rectified, the product is distilled out and then collected, so that the product cannot be carried to the distilled product and only stays at the bottom of the final rectifying kettle; in addition, ferric trichloride is also a good high-efficiency catalyst and a complexing agent, so that unsubstituted and complete chlorosilane is completely converted into alkoxy silane, and the aim of removing chloride is fulfilled.

(2) As industrial chlorosilane is stored in a carbon steel storage tank, the chlorosilane contains a large amount of metal ions, and heavy metal salt is added during chlorine treatment, the hue of the solution is obviously improved, and the hue index of the solution is obviously reduced after the cationic surfactant is added for complexing. The inventors have also unexpectedly found that the addition of a certain amount of cationic surfactant not only reduces the hue index but also promotes the removal of chloride from the system to some extent, probably because the complex formed by complexing the cationic surfactant with the metal ion also has some activity in catalyzing the hydrolysis of chlorosilanes.

(3) Adding lower sodium alkoxide solution with certain concentration, such as 30-40% sodium methoxide in methanol, reacting sodium methoxide with free chlorine (mainly hydrogen chloride) in methyltrimethoxysilane at 30-50 deg.C, neutralizing to remove chlorine dissolved in crude product to obtain methanol, and maintaining pH of the solution at 9-11.

(4) And (3) rectifying the mixture after the reaction is finished to obtain a pure product of the methyltrimethoxysilane, and recovering and treating the residual high-boiling-point solvent in the kettle.

(5) By adopting the treatment method, the chlorine content in the crude methyltrimethoxysilane product in the whole process can be reduced from 500ppm to below 2ppm, the conductivity is as low as 0.2 mu s/cm, the yield of the product reaches about 99%, the loss rate is below 1%, the color degree reaches APHA10, and the treatment process is simple and convenient.

Drawings

FIG. 1 is a schematic diagram of the chloride removal scheme for alkoxysilanes according to the present invention.

Detailed Description

The method for removing chloride by using alkoxysilane according to the present invention is explained in further detail with reference to the following embodiments, and the alkoxysilane used in the examples is a crude methyltrimethoxysilane because the methyltrimethoxysilane used in the electrical and electronic industry has more strict requirements for the chloride content. Therefore, the alkoxy silane to be removed from chloride in the embodiment of the present invention is methyl trimethoxy silane, but it should not be construed as limiting the scope of the present invention, and for other alkoxy silanes, similar effects can be achieved by the method for removing chloride provided by the present invention, and it is within the scope of the present invention.

Example 1

Putting 2000kg of methyltrimethoxysilane crude product (chromatographic analysis of methyltrimethoxysilane content 91%, chlorine content 520ppm and APHA50) obtained by the reaction into a reaction kettle, then adding 2kg of anhydrous ferric trichloride powder into the reaction kettle, heating to 80 ℃ under the condition of stirring, keeping the temperature for 2h, evaporating out methanol, continuously heating to 110 ℃ for refluxing for 2h, adding 0.4kg of octadecyl trimethyl ammonium chloride, and continuously keeping the temperature for refluxing for 1.5 h; after the reaction is finished; cooling to 40 ℃, adding 20kg of methanol solution of 30% sodium methoxide, stirring and reacting for 0.5h, and measuring the pH value of the solution to be 10; further distilling off methanol, and rectifying to obtain pure product 1812 kg.

Example 2

The same procedure as in example 1 was conducted, except that 3kg of anhydrous ferric trichloride and 0.6kg of octadecyl trimethyl ammonium chloride were used instead.

Example 3

The same procedure was followed as in example 2, except that 30kg of a 30% sodium methoxide solution in methanol was used instead.

Example 4

The same procedure was followed as in example 2, except that the amount of 30% sodium methoxide in methanol was changed to 10 kg.

Example 5

The same procedure was followed as in example 2, except that the amount of octadecyl trimethyl ammonium chloride was changed to 0.2 kg.

Example 6

The same procedure was followed as in example 2, except that the amount of octadecyl trimethyl ammonium chloride was changed to 0.8 kg.

Example 7

The same procedure was followed as in example 2, except that the amount of octadecyl trimethyl ammonium chloride was changed to 1.2 kg.

Example 8

The same procedure as in example 2 was followed, except that the amount of anhydrous ferric chloride was changed to 10 kg.

Example 9

The same procedure as in example 2 was followed, except that 50kg of anhydrous ferric chloride was used instead.

Example 10

The same procedure was followed as in example 2, except that the cationic surfactant was replaced with tetrabutylammonium chloride.

Example 11

The same procedure as in example 2 was followed, except that the cationic surfactant was replaced with cetyldimethylbenzylammonium chloride.

Comparative example 1

The same procedure as in example 2 was followed, except that no cationic surfactant was added.

Comparative example 2

Putting 2000kg of methyltrimethoxysilane crude product (chromatographic analysis of methyltrimethoxysilane content 91%, chlorine content 520ppm, APHA50) obtained by the reaction into a reaction kettle, heating to 60 ℃, adding 30kg of 30% sodium methoxide methanol solution, stirring and reacting for 0.5h, and measuring the pH of the solution to be 8; further rectifying to obtain a pure product, and detecting to obtain 1761kg of a finished product.

The methyltrimethoxysilanes from the above examples and comparative examples were tested and the various indices are shown in table 1:

TABLE 1

Sample (I)	Purity/%)	Yield/%	Chlorine content/ppm	Conductivity of aqueous solution/μ s/cm	Hue index
						Example 1	99.58	99.14	1.5	0.28	APHA20
Example 2	99.74	99.42	1.0	0.20	APHA10
						Example 3	99.57	98.34	1.2	0.22	APHA10
Example 4	99.55	99.39	2.1	0.36	APHA20
						Example 5	99.49	99.45	1.8	0.26	APHA30
Example 6	99.52	99.39	1.6	0.31	APHA10
						Example 7	99.54	99.43	3.2	0.52	APHA10
Example 8	99.43	99.32	2.5	0.44	APHA20
						Example 9	99.31	99.33	1.3	0.55	APHA40
Example 10	99.62	99.42	1.5	0.23	APHA10
						Example 11	99.51	99.38	1.7	0.25	APHA20
Comparative example 1	99.42	98.87	4.8	0.87	APHA80
						Comparative example 2	99.08	95.59	124	1.80	-

The conductivity of the aqueous solution was measured by preparing the resulting methyltrimethoxysilane as a2 wt% aqueous solution and measuring its conductivity.

The method of measuring the color index is carried out according to the standard ASTM D1209-2005.

As can be seen from the data in Table 1, the method for removing chloride from alkoxysilane provided by the invention adopts the compounding of anhydrous ferric chloride and cationic surfactant to exert a synergistic effect, so that the content of chloride in the treated alkoxysilane is greatly reduced and can reach below 3.2ppm, and the preferred embodiment can reach 1 ppm; and the conductivity of the obtained alkoxysilane aqueous solution is below 0.55 mu s/cm, the preferred embodiment can reach 0.2 mu s/cm, and the removal of chloride is relatively thorough as reflected in the side surface. In addition, through the test of hue index, after the alkoxy silane is treated by the method for removing chloride provided by the invention, the hue index is lower and is generally below APHA30, and the preferred embodiment can reach APHA10, thereby meeting the requirement of practical application. In addition, the method for removing the chloride has the advantages of high product yield of about 99.5%, low loss rate, simple and convenient treatment process, low cost of the process for removing the chloride from the alkoxy silane and good effect, and is a dechlorination method suitable for large-scale industrial popularization.

The above-mentioned embodiments are only preferred embodiments of the present invention, and are not intended to limit the embodiments of the present invention, and those skilled in the art can easily make various changes or modifications according to the main concept and spirit of the present invention, so the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for removing chloride from an alkoxysilane comprising the steps of:

adding transition metal chloride into the crude product of the alkoxy silane, mixing, performing a first heating stage, performing a second heating stage at a higher temperature, simultaneously adding a cationic surfactant, performing heat preservation reflux reaction, cooling after the reaction is finished, adding a lower alcohol solution of lower sodium alkoxide for neutralization, and rectifying to obtain an alkoxy silane product with low chlorine content;

the first heating stage is to heat up and evaporate the recovered methanol at 70-90 ℃ for 1-3 hours; the second heating stage is heating reflux reaction to 100 deg.c and 120 deg.c for 2-5 hr;

the transition metal chloride is ferric chloride; the dosage of the transition metal chloride is 0.1 to 0.3 percent of the mass of the alkoxy silane needing to remove the chloride;

the cationic surface activity is selected from at least one of octadecyl trimethyl ammonium chloride, hexadecyl dimethyl benzyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride and tetrabutyl ammonium chloride; the dosage of the cationic surfactant is 0.02-0.05% of the mass of the alkoxy silane needing to remove chloride.

2. The method of claim 1, wherein the reducing the temperature is to reduce the temperature to 30-50 ℃.

3. The method of claim 1, wherein the alkoxysilane comprises methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, tetramethoxysilane, tetraethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane.

4. The method of claim 1, wherein the lower alcohol is an aliphatic alcohol having 1 to 4 carbon atoms; and/or the lower sodium alkoxide is an alcoholic solution with the mass percentage concentration of 20-50%; the amount of the lower sodium alkoxide solution is 0.5-3% of the mass of the alkoxy silane to be chloride removed.

5. The method of claim 4, wherein the lower alcohol is methanol, ethanol, propanol, and butanol; the lower sodium alkoxide is an alcoholic solution with the mass percentage concentration of 30-40%; the amount of the lower sodium alkoxide solution is 1-2% of the mass of the alkoxy silane to be chloride removed.

6. Putting alkoxysilane and anhydrous ferric trichloride powder into a reaction kettle, heating to 70-90 ℃ to evaporate methanol, then continuously heating to 100-120 ℃ to reflux for 1-3h, adding hexadecyl trimethyl ammonium chloride, preserving heat and refluxing for 1-2h, after the reaction is finished, cooling to 30-50 ℃, adding 30-40 wt% of methanol solution of sodium methoxide to react for 0.5-1h, neutralizing until the pH value of a crude product is 9-11, and then rectifying to obtain a low-chlorine pure alkoxysilane; wherein the dosage of the anhydrous ferric chloride is 0.1-0.2% of the mass of the alkoxy silane, the dosage of the hexadecyl trimethyl ammonium chloride is 0.02-0.05% of the mass of the alkoxy silane, and the dosage of the sodium methoxide solution is 0.8-1.5% of the mass of the alkoxy silane.