Process and use of amino-functional resins for dismutating halosilanes and for removing extraneous metals

Abstract

The invention relates to a process for dismutating at least one halosilane and reducing the content of extraneous metal and/or a compound containing extraneous metal in the at least one halosilane and in the at least one silane obtained, by contacting at least one halosilane of the general formula I, H.sub.nSiCl.sub.m (I), where n and m are integers and n=1, 2 or 3 and m=1, 2 or 3 and n+m=4, with a particulate, organic, amino-functional resin to obtain at least one silane of the general formula II, H.sub.aSiCl.sub.b (II), where a and b are integers and a=0, 2, 3 or 4 and b=0, 1, 2 or 4 where a+b=4, in one step, in which the content of extraneous metal and/or compounds containing extraneous metal has been reduced compared to the halosilane of the formula I. The invention further provides for the use of this resin for dismutating halosilanes and as an absorbent of extraneous metals or compounds containing extraneous metal in a process for preparing monosilane.

Claims

1. A process for dismutating a trichlorosilane, the process comprising: first washing a particulate, organic, amino-functional resin with deionized water, the resin comprising a dialkylamino- or dialkylaminomethylene-functionalized divinylbenzene-styrene copolymer or trialkylammonium- or trialkylammoniummethylene-functionalized divinylbenzene-styrene copolymer, to obtain a water-containing resin; then applying reduced pressure or vacuum to the water-containing resin and regulating the temperature at below 200 C., and then removing the reduced pressure or vacuum, thereby obtaining an anhydrous and solvent-free catalyst resin having a water content of less than 2% by weight, without contacting the resin with an organic solvent after washing with the deionized water; and conducting a reactive distillation or reactive rectification of a trichlorosilane-containing stream with the anhydrous and solvent-free catalyst resin, to obtain at least two silanes, thereby reducing a content of a compound comprising boron, iron, or both to less than 10 g/kg, wherein: the at least two silanes are represented by formula (II):
H.sub.aSiCl.sub.b(II); a and b are integers; a=0, 2, 3 or 4; b=0, 1, 2 or 4; a+b=4; the catalyst resin, then contacted with the trichlorosilane, has a water content, if present, of less than 2% by weight and an organic solvent content, if present, of 2.5% by weight or less; the content of the compound comprising boron, iron, or both is reduced by from 70 to 99% by weight; and the reactive distillation or reactive rectification comprises reaction and distillative separation in one apparatus.

2. The process of claim 1, wherein a silane of the at least two silanes comprises a monosilane which is distilled with the catalyst resin after the conducting and is decomposed thermally to ultrapure silicon.

3. The process of claim 1, wherein contacting the trichlorosilane with the catalyst resin reduces a content of iron.

4. The process of claim 1, wherein contacting the trichlorosilane with the catalyst resin reduces a content of boron.

5. The process of claim 1, wherein the content of the compound comprising boron, iron, or both is reduced by from 95 to 99% by weight.

6. The process of claim 1, wherein the catalyst resin, when contacted with the trichlorosilane, has an organic solvent content, if present, of 0.5% by weight or less.

7. The process of claim 1, wherein the process does not comprise contacting either of the at least two silanes with activated carbon.

8. The process of claim 2, wherein the process does not comprise any further purification step after the monosilane is distilled.

9. The process of claim 1, wherein the catalyst resin has a water content of less than 0.8% by weight.

10. The process of claim 1, wherein contacting trichlorosilane with the catalyst resin comprises supplying trichlorosilane is supplied batchwise to the catalyst resin.

11. The process of claim 1, wherein the apparatus comprises a column.

12. The process of claim 11, wherein the apparatus further comprises a side reactor assigned to the column.

Description

EXAMPLE 1.1

(1) Pretreatment of the resin or of the pure adsorbents. The adsorbents are carefully dried before use in the process in order to prevent hydrolysis of the halosilanes to be purified.

EXAMPLE 1.2

(2) General process method for treating the halosilane contaminated with extraneous metals and/or metallic compounds.

(3) A defined amount of amino-functionalized resin or adsorbent is initially charged in a 500 ml stirred apparatus comprising a glass four-neck flask with condenser (water, dry ice), dropping funnel, stirrer, thermometer and nitrogen connection, and, under reduced pressure (<1 mbar), a) the amino-functionalized resin and Amberlite XAD 4 are dried at 95 C. and b) the further adsorbents are each dried at 170 C. over 5 hours, followed by slow venting with dry nitrogen and cooling.

(4) Subsequently, 250 ml of the halosilane are added via the dropping funnel. Over a period of 5 hours, the adsorption operation is performed under standard pressure at room temperature under a protective gas atmosphere. The adsorbent is removed from the silane by drawing it through a frit (por. 4) into an evacuated 500 ml glass flask with discharge device. Subsequently, the glass flask is vented with nitrogen and discharged into a nitrogen-purged Schott glass bottle.

EXAMPLE 1.3COMPARATIVE EXAMPLE

(5) The example which follows was performed according to the general process method with the amounts specified here.

(6) 36.0 g of Amberlite XAD 4 were pretreated according to the general method described under Example 1.2, and 250 ml of trichlorosilane were added. The metal contents before and after the treatment were determined by means of ICP-MS. The trichlorosilane content was determined by gas chromatography (area percent).

(7) TABLE-US-00001 TABLE 1.3 Extraneous metal contents before and after the treatment: Metal Content before treatment Content after treatment Boron 1100 g/kg 13 g/kg Iron 130 g/kg 7.9 g/kg GC: Trichlorosilane 99.9% 99.9%

EXAMPLE 1.4COMPARATIVE EXAMPLE

(8) The example which follows was performed according to the general process method with the amounts specified here.

(9) 36.9 g of K 10 montmorillonite were pretreated according to the general method described under Example 1.2, and 250 ml of trichlorosilane were added. The metal contents before and after the treatment were determined by means of ICP-MS. The trichlorosilane content was determined by gas chromatography (area percent).

(10) TABLE-US-00002 TABLE 1.4 Extraneous metal contents before and after the treatment: Metal Content before treatment Content after treatment Aluminium 18 g/kg <0.9 g/kg Boron 1100 g/kg 54 g/kg Iron 3.1 g/kg 1.3 g/kg GC: Trichlorosilane 99.9% 99.9%

EXAMPLE 1.5COMPARATIVE EXAMPLE

(11) The example which follows was performed according to the general process method with the amounts specified here.

(12) 20.0 g of Wessalith F 20 were pretreated according to the general method described under Example 1.2, and 250 ml of trichlorosilane were added. The metal contents before and after the treatment were determined by means of ICP-MS. The trichlorosilane content was determined by gas chromatography (area percent).

(13) TABLE-US-00003 TABLE 1.5 Extraneous metal contents before and after the treatment: Metal Content before treatment Content after treatment Aluminium 130 g/kg 66 g/kg Boron 1100 g/kg <10 g/kg Iron 130 g/kg 4.0 g/kg GC: Trichlorosilane 99.9% 99.9%

EXAMPLE 1.6INVENTIVE

(14) The example which follows was performed according to the general process method with the amounts specified here.

(15) 14.2 g of Amberlyst A21 (dry mass) were pretreated according to the general method described under Example 1.2, and 250 ml of trichlorosilane were added. The metal contents before and after the treatment were determined by means of ICP-MS. The composition was determined by gas chromatography (area percent).

(16) TABLE-US-00004 TABLE 1.6 Extraneous metal contents before and after the treatment, and composition: Metal Content before treatment Content after treatment Boron 840 g/kg 72 g/kg Iron 31 g/kg 8 g/kg GC: Trichlorosilane 99.9% 91.7% Silicon tetrachloride 5.5% Dichlorosilane 2.8% Monochlorosilane <0.1% * Monochlorosilane was detectable in traces. Owing to the low boiling points, the monochlorosilane and monosilane reaction products could not be retained quantitatively in the reaction mixture.

EXAMPLE 1.7INVENTIVE

(17) The example which follows was performed according to the general process method with the amounts specified here.

(18) 80.2 g of Amberlyst A21 (dry mass 28.9 g) were pretreated according to the general method described under Example 1.2, and 250 ml of trichlorosilane were added. The composition was determined by gas chromatography (area percent).

(19) TABLE-US-00005 TABLE 1.7 Composition GC Content before treatment Content after treatment Trichlorosilane 99.9% 87.8% Silicon tetrachloride 8.4% Dichlorosilane 3.6% Monochlorosilane* <0.1% *Monochlorosilane was detectable in traces. Owing to the low boiling points, the monochlorosilane and monosilane reaction products could not be retained quantitatively in the reaction mixture.