DE102014018435A1 - Process for recovering hexachlorodisilane from mixtures of chlorosilanes contained in process effluent streams - Google Patents

Abstract

The invention relates to a process for recovering hexachlorodisilane from mixtures of chlorosilanes having the general formula SixHyCl2x + 2-y contained in process exhaust gas streams, where x = 1 and y = 0-3 and x = 2 and y = 0-5. The present invention is therefore based on the object to provide a method which is a separation of Hexachlordisilans with high yields from the chlorosilane mixtures described in the thermal reaction of hydrogen with monosilanes of the general formula SixHyCl2x + 2-y, where x is 1 and y equals 0-2, accumulates, allows. The object is achieved by a process for recovering hexachlorodisilane from mixtures of chlorosilanes with the general formula SixHyCl2x + 2-y contained in process exhaust gas streams, where x = 1 and y = 0-3 and x = 2 and y = 0-5 in that the exhaust gas streams or fractions thereof are converted into the liquid phase and thereafter the partially hydrogenated chlorodisilanes of the general formula SixHyCl2x + 2-y (x = 2, y = 1-5) present in the mixture of the chlorosilanes are additionally catalytically added be converted to hexachlorodisilane and separated from the resulting mixture hexachlorodisilane by distillation.

Description

The invention relates to a process for the recovery of hexachlorodisilane of mixtures of chlorosilanes having the general formula Si _x H _y Cl _{2x + 2-y} contained in process gas streams, where x = 1 and y = 0-3, and x = 2 and y = 0-5 is.

In addition to chlorodisilanes with the general formula Si _x H _y Cl _{2x + 2-y} , where x = 1 and y = 0-3, the process exhaust streams can also significant proportions of partially hydrogenated chlorodisilanes having the general formula Si _x H _y Cl _{2x + 2 -Y} , where x = 2 and y = 1-5, and small proportions of higher-boiling silicon compounds and in the reaction with hydrogen chlorosilanes of the general formula Si _x H _y Cl _{2x + 2-y} , where x = 1 and y = 0 -2 is included.

Processes such as the chemical vapor deposition of silicon from monosilanes, with the general formula Si _x H _y Cl _{2x + 2-y} , where x = 1 and y = 0-2, as in the chemical vapor deposition of the Siemens process as well as in other CVD For example, microelectronic processes using chlorosilanes, hydrogenation of silicon tetrachloride to produce trichlorosilane or trichlorosilane synthesis from metallurgical silicon produce such process effluents. In addition, such exhaust gases also occur in the case of plasma reactions (T> 200 ° C.) of chlorosilanes, with the general formula Si _x H _y Cl ₂ x _{+ 2-y} where x = 1 and y = 1-3, without hydrogen being added. Processes such as heating trichlorosilane in an electrode burner to> 200 ° C, as in DE1142848B described, can supply these process exhaust gases.

In the industrially customary process steps known per se, the low-boiling components (boiling temperatures <57 ° C. at 1013.25 mbar) of the abovementioned process offgases are partially or completely separated in one or more distillation steps. A chlorosilane mixture with components having a boiling point> 57 ° C. (at 1013.25 mbar) remains in the distillation bottoms. This chlorosilane mixture contains Si ₂ Cl ₆ (hexachlorodisilane) and further partially hydrogenated chlorodisilanes having the general formula Si _x H _y Cl ₂ x _{+ 2-y} , where x is 2 and y is 1-5.

Hexachlorodisilane is an important starting material in microelectronics. The compound is, inter alia, precursor in CVD deposition for high-purity silicon nitride, silicon oxide or silicon carbide layers. Furthermore, hexachlorodisilane plays an important role in transistor fabrication in memory chips. By means of low-temperature epitaxy, epitaxial silicon layers are deposited.

So far, the difficulty was due to the very similar boiling points of hexachlorodisilane and other partially hydrogenated chlorodisilanes a pure fraction of hexachlorodisilane (Si ₂ Cl ₆ ) to win. For this purpose, an energetically and technically complicated distillation with a high number of separation stages is required, as in EP 1264798 described. The resulting yields of hexachlorodisilane are low and can only be increased by the chlorination of the partially hydrogenated chlorosilanes by an additional chlorination step with the chlorinating agent chlorine. The use of chlorine increases the equipment and safety costs.

Previous methods aimed in particular at destroying the chlorodisilanes having the general formula Si _x H _y Cl _{2x + 2-y} , where x is 2 and y is 0-5, which usually occur as undesirable by-products in the process. The pure hydrolysis of these components disadvantageously led to highly reactive solids. For this reason, the destruction of these high-boiling components is difficult. A destruction of these chlorosilanes is in EP 2544795 B1 and US 2009/0104100 A1 described.

Another method describes the reaction with chlorine gas after EP 2036859 B1 causes the silicon-silicon bond to be cleaved, thus destroying the high-quality disilanes of the general formula Si _x H _y Cl _{2x + 2-y} , where x is 2 and y is 1-5. The aim of this reaction is to convert the disilane to silicon tetrachloride and return it back to the material cycle in order to increase the material yield.

In DE 3503262 A1 describes the catalytic conversion of hexachlorodisilane / pentachlorodisilane mixtures to organotitrogen or phosphorus compounds. The objective of the applicants is complete decomposition of the listed disilanes to trichlorosilane, silicon tetrachloride and solid polychlorosilane.

The present invention is therefore based on the object to offer a process which comprises a separation of the hexachlorodisilane with high yields from the chlorosilane mixtures described, which is obtained in the thermal reaction of hydrogen with monosilanes of the general formula Si _x H _y Cl _{2x + 2-y} , where x is 1 and y is 0-2, is possible.

The object is achieved by a method for the recovery of hexachlorodisilane of mixtures of chlorosilanes having the general formula Si _x H _y Cl _{2x + 2-y} contained in process gas streams, where x = 1 and y = 0-3, and x = 2 and y = 0-5, which is characterized in that the exhaust gas streams or portions thereof are converted into the liquid phase and then the partially hydrogenated chlorodisilanes contained in the mixture of chlorosilanes of the general formula Si _x H _y Cl _2x-2-y (x = 2 , y = 1-5) are reacted catalytically in addition to hexachlorodisilane and separated from the resulting mixture hexachlorodisilane by distillation.

Advantageous developments are specified in the subclaims.

Thereafter, the transfer of the exhaust gases into the liquid phase takes place by condensation or absorption in a solvent and the catalytic reaction is carried out at a temperature of 0 to 100 ° C and a pressure up to 20 bar.

In an advantageous embodiment of the invention, the reaction is carried out in a batch or in a continuous process.

A further advantageous embodiment of the method is that the catalyst is immobilized on inorganic, such as Al ₂ O ₃ , SiO ₂ or organic, such as copolymer of styrene and divinylbenzene, solids, dispersed or used dissolved in a mixture of chlorosilanes.

• – primäre, sekundäre, tertiäre Amine der allgemeinen Formel I:
  
  wobei R1, R2 und R3 Wasserstoff-, Alkyl- mit C₁ bis C₁₀, Cycloalkyl- mit einer Ringgröße von 4 bis 8, Alkenyl- mit C₁ bis C₁₀ oder Aryl- mit einer Ringröße von 4 bis 8, Gruppen sind und R1 ≠ R2 ≠ R3, R1 = R2 ≠ R3 oder R1 = R2 = R3 ist, wobei die organischen Reste linear als auch verzweigt vorliegen können,
• – quartäre Amine/Ammoniumsalze der allgemeinen Formel II:
  
  wobei R1, R2, R3 und R4 Wasserstoff-, Alkyl- mit C₁ bis C₁₀, Cycloalkyl- mit einer Ringröße von 4 bis 8, Alkenyl- mit C₁ bis C₁₀ oder Aryl- mit einer Ringröße von 4 bis 8 Gruppen und A Halogenide, Pseudohalogenide, Phosphate und Sulfate sind und R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 oder R1 = R2 ≠ R3 ≠ R4 oder R1 = R2 = R3 = R4, wobei die organischen Reste linear als auch verzweigt vorliegen können,
• – heterozyklische Stickstoffverbindungen der allgemeinen Formel III:
  
  mit einer Ringgröße von 4 bis 8, wobei R1, R2, R3 und R4 Wasserstoff-, Alkyl- mit C₁ bis C₁₀, Cycloalkyl- mit einer Ringröße von 4 bis 8, Alkenyl- mit C₁ bis C₁₀ oder Aryl- mit einer Ringröße von 4 bis 8 Gruppen sind und R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 oder R1 = R2 ≠ R3 ≠ R4 oder R1 = R2 = R3 = R4 ist, wobei die organischen Reste linear als auch verzweigt vorliegen können,
• – heterozyklische aromatische Verbindungen (Azine) mit ein bis vier Stickstoff-Atomen im Ring, wie Pyridin, Pyrazin, Triazin und deren Derivate, deren Reste Wasserstoff-, Alkyl- mit C₁ bis C₁₀, Cycloalkyl- mit einer Ringröße von 4 bis 8, Alkenyl- mit C₁ bis C₁₀ oder Aryl- mit einer Ringröße von 4 bis 8 Gruppen sein können, wobei die organischen Reste linear als auch verzweigt vorliegen können.
• – Organophosphorverbindungen, wie primäre, sekundäre, tertiäre Phosphine, der allgemeinen Formel IV
  
  wobei R1, R2 und R3 Wasserstoff-, Alkyl- mit C₁ bis C₁₀, Cycloalkyl- mit einer Ringröße von 4 bis 8, Alkenyl- mit C₁ bis C₁₀ oder Aryl- mit einer Ringröße von 4 bis 8 Gruppen sind und R1 ≠ R2 ≠ R3, R1 = R2 ≠ R3 oder R1 = R2 = R3 ist, wobei die organischen Reste linear als auch verzweigt vorliegen können, und
• – quartäre Phosphine der allgemeinen Formel V
  
  wobei R1, R2, R3 und R4 Wasserstoff-, Alkyl- mit C₁ bis C₁₀, Cycloalkyl- mit einer Ringröße von 4 bis 8, Alkenyl- mit C₁ bis C₁₀ oder Aryl- mit einer Ringröße von 4 bis 8 Gruppen und A Halogenide, Pseudohalogenide, Phosphate und Sulfate sind und R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 oder R1 = R2 ≠ R3 ≠ R4 oder R1 = R2 = R3 = R4 ist, wobei die organischen Reste linear als auch verzweigt vorliegen können.

An inventive embodiment provides that the following compounds are used as catalysts:

• Primary, secondary, tertiary amines of general formula I:
  
  wherein R 1, R 2 and R 3 are hydrogen, alkyl with C ₁ to C ₁₀ , cycloalkyl having a ring size of 4 to 8, alkenyl with C ₁ to C ₁₀ or aryl with a ring size of 4 to 8, groups and R1 ≠ R2 ≠ R3, R1 = R2 ≠ R3 or R1 = R2 = R3, it being possible for the organic radicals to be linear or branched,
• Quaternary amines / ammonium salts of general formula II:
  
  wherein R ₁ , R 2, R 3 and R 4 are hydrogen, alkyl of C ₁ to C ₁₀ , cycloalkyl having a ring size of 4 to 8, alkenyl of C ₁ to C ₁₀ or aryl having a ring size of 4 to 8 groups and A are halides, pseudohalides, phosphates and sulfates and R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 or R1 = R2 ≠ R3 ≠ R4 or R1 = R2 = R3 = R4, where the organic radicals are linear as well as branched can be present
• Heterocyclic nitrogen compounds of general formula III:
  
  having a ring size of 4 to 8, wherein R ₁ , R 2, R 3 and R 4 are hydrogen, C ₁ to C ₁₀ alkyl, cycloalkyl of 4 to 8, alkenyl of C ₁ to C ₁₀ or aryl a ring size of 4 to 8 groups and R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 or R1 = R2 ≠ R3 ≠ R4 or R1 = R2 = R3 = R4, wherein the organic radicals are linear as well as branched can be present
• - Heterocyclic aromatic compounds (azines) having one to four nitrogen atoms in the ring, such as pyridine, pyrazine, triazine and their derivatives, their radicals hydrogen, alkyl with C ₁ to C ₁₀ , cycloalkyl having a ring size of 4 to 8 , Alkenyl- with C ₁ to C ₁₀ or aryl with a ring size of 4 to 8 groups may be, wherein the organic radicals may be linear or branched.
• - Organophosphorus compounds, such as primary, secondary, tertiary phosphines, the general formula IV
  
  wherein R1, R2 and R3 are hydrogen, alkyl with C ₁ to C _10, cycloalkyl with a ring size and are 4-8, alkenyl with C ₁ to C ₁₀ or aryl having a ring size 4-8 groups R1 ≠ R 2 ≠ R 3, R 1 = R 2 ≠ R 3 or R 1 = R 2 = R 3, where the organic radicals may be linear or branched, and
• - Quaternary phosphines of the general formula V
  
  wherein R ₁ , R 2, R 3 and R 4 are hydrogen, alkyl of C ₁ to C ₁₀ , cycloalkyl having a ring size of 4 to 8, alkenyl of C ₁ to C ₁₀ or aryl having a ring size of 4 to 8 groups and A are halides, pseudohalides, phosphates and sulfates and R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 or R1 = R2 ≠ R3 ≠ R4 or R1 = R2 = R3 = R4, where the organic radicals are linear as well may be branched.

In one development of the invention, the chlorosilane mixture is mixed with silicon tetrachloride, which advantageously leads to an increase in yield. A further embodiment is characterized in that, after the catalytic conversion of the chlorosilane mixture, the distillative separation of the reaction mixture takes place or the catalytic reaction takes place during a reactive distillation.

The advantages here are in particular the lower equipment costs and the better energy balance. Increasing the temperature, then catalytically reacting and distilling immediately is energetically and technologically more advantageous than increasing the temperature, catalytically reacting, cooling, reheating and then distilling.

Particularly advantageous catalysts such as alkylated or arylated tertiary amines such as trimethylamine, in homogeneous form or immobilized on inorganic or organic support materials alkylated or arylated tertiary amines are used which have groupings such as dimethylamino groups, heterocyclic nitrogen compounds (azines), pyridine groups or nitriles or quaternary amines, with trimethylammonium chloride groups supported on an organic carrier material, such as. As a copolymer of styrene and divinylbenzene or on an inorganic support material such. As silica, are immobilized.

The heterogeneous catalyst is used in the form of pellets having a particle size greater than 0.5 mm. A fine fraction is not included. The catalyst still has sufficient stability at at least 100 ° C., is insoluble and substantially does not tend to split off the amine. The catalytically active functional groups are easily accessible.

For the homogeneous reaction are tertiary alkylamines, such as. B.: Trimethylamine, which are soluble in the system one and have a significantly lower boiling point than that of hexachlorodisilane, so that a good separation is guaranteed.

According to the invention, chlorosilane mixtures having proportions of chlorosilanes of the general formula Si _x H _y Cl _{2 x + 2-y} , where x is 2 and y is 0-5, of process exhaust gas streams from the reaction of hydrogen with chlorosilanes having the general formula Si _x H _y Cl _{2x + 2-y} , where x equals 1 and y equals 0-2. The aim of this processing is the recovery of high-boiling components Si _x H _y Cl _{2x + 2-y} , where x> 1 (boiling point> 100 ° C, at 1013.25 mbar), in particular hexachlorodisilane (Si ₂ Cl ₆ ).

The catalytic conversion of the chlorosilane mixture leads mainly to the formation of hexachlorodisilane and higher-boiling silicon compounds, which allows a particularly clean separation of hexachlorodisilane. The boiling point differences which can advantageously be achieved with the invention are so serious in the system obtained that separation of the components can take place with little technical and energy expenditure. Consequently, the purity of the obtained fractions can be increased. In contrast to EP 1264798 A1 Here is a complete implementation of all partially hydrogenated chlorodisilanes. In addition, advantageously additional hexachlorodisilane is formed according to the invention by the catalytic reaction and thus increases the overall yield.

Further advantages of the present invention are that hexachlorodisilane can be separated from the exhaust gases of the processes described with low equipment costs and low costs, without additional safety risks, in high purity. This is achieved by means of the selective catalytic reaction of partially hydrogenated chlorodisilane moieties in the chlorosilane mixture, having the general formula Si _x H _y Cl ₂ x _{+ 2-y} , where x is 2 and y is 0-5. By means of the catalytic reaction, the yield of hexachlorodisilane is considerably increased.

The invention is based on 1 in which the method according to the invention is shown schematically in a flow chart, and explained in more detail in subsequent embodiments.

According to flow chart 1 in the process for recovering hexachlorodisilane from mixtures of chlorosilanes in a process exhaust range 1 resulting process waste gases, after conversion into the liquid phase by condensation in a distillative pre-separation 2 into a separation area 3 and a separation area 4 separated.

In the separation area 3 in this case, predominantly chlorosilanes of the general formula Si _x H _y Cl _{2x + 2-y} , (x = 1, y = 0-3) and in the separation region collect 4 a mixture of SiCl ₄ with proportions between 10 and 99% by mass and Si _x H _y Cl _{2x + 2-y} (x = 2, y = 0-5) with proportions between 1 and 90% by mass.

The further treatment of the mixture of chlorosilanes, in the separation area 4 obtained, with the aim in particular to enrich and separate hexachlorodisilane.

According to the invention, in an advantageous variant of the method, a catalytic reaction 5 of the chlorosilane mixture from the separation area 4 carried out. This as a result of the catalytic reaction 5 resulting reaction mixture is then in a distillative separation 7 separated into three fractions. A faction 7.1 contains chlorosilanes of the general formula Si _x H _y Cl _2x-2-y (x = 1, y = 0-2). It is a separation of the monosilanes contained for the return to the process cycle conceivable. A faction 7.2 contains the target product hexachlorodisilane Si ₂ Cl ₆ and the distillation bottoms 7.3 contains a mixture of higher-boiling silicon compounds with> 2 silicon atoms in the molecule.

In a further advantageous variant of the method according to the invention by means of a reactive distillation 6 the chlorosilane mixture from the separation area 4 catalytically reacted during the distillation. After separation of the fraction 6.1 containing mainly trichlorosilane, the catalyst must be separated from the liquid phase prior to further distillation to thereafter silicon tetrachloride as a separate fraction 6.2 and hexachlorodisilane as a fraction 6.3 to win. What remains is a distillation bottoms 6.4 from higher-boiling silicon compounds with> 2 silicon atoms in the molecule.

Embodiment 1 (Comparative Example)

767.0 g of a chlorosilane mixture, which corresponds to the high boiler fraction of a distillation of exhaust gases of a silicon production, were separated by distillation. Fractions listed below were obtained. The swamp was not investigated further. Table 1. Overview of the composition of the starting mixture and the fractions of the comparative example (TCS = trichlorosilane, STC = silicon tetrachloride, TCDS = tetrachlorodisilane, PCDS = pentachlorodisilane, HCDS = hexa-chlorodisilane)

Embodiment 2 (according to FIG. 1, implementation 5 )

In a three-necked flask, 303.3 g of chlorosilane mixture were mixed with 0.4 g of the catalyst Amberlyst A21 ^® at 20 ° C. After one week, the composition was redetermined (Table 2). The catalyst was filtered off and the mixture was separated by distillation. Three fractions were taken. The third fraction or the bottoms contained, in addition to hexachlorodisilane, further higher-boiling silicon compounds. Table 2. Overview of compositions of the mixtures and the fractions of Example 1 (TCS = trichlorosilane, STC = silicon tetrachloride, TCDS = tetrachlorodisilane, PCDS = pentachlorodisilane, HCDS = hexachlorodisilane and HSS = higher boiling silicon compounds). Composition determined by NMR spectroscopy.

Embodiment 3 (according to FIG. 1, implementation 5 )

In a three necked flask, 20.5 g of Amberlyst A21 ^® (ca. 900 mL) chlorosilane mixture at 20 ° C and 1352.3 g. The mixture was analyzed by NMR spectroscopy after one week. The catalyst was filtered off and the mixture was separated by distillation. It was possible to obtain 232.7 g of hexachlorodisilane (Table 3). Table 3. Overview of Compositions of the Mixtures of Example 2 (TCS = trichlorosilane, STC = silicon tetrachloride, TCDS = tetrachlorodisilane, PCDS = pentachlorodisilane, HCDS = hexachlorodisilane and HSS = higher boiling silicon compounds). Composition determined by NMR spectroscopy.

Embodiment 4 (of FIG. 1, reactive distillation 6 )

In a distillation apparatus 1344.6 g of a Chlorsilangemischs were added to 19.9 g of the catalyst Amberlyst A21 ^® and heated to 45 ° C. Here, 119.9 g of trichlorosilane were separated. Subsequently, the catalyst was filtered off. From the remaining solution were then 851.7 g of silicon tetrachloride and 236.8 g of hexachlorodisilane are separated by distillation. The bottom remained as a yellowish solution (136.2 g). in this solution, an additional 4.0 g hexachlorodisilane were included (NMR spectroscopic investigation). The remainder was assigned to higher boiling silicon compounds (Table 4). Table 4. Overview of compositions of the mixtures and the fractions of Example 1 (TCS = trichlorosilane, STC = silicon tetrachloride, TCDS = tetrachlorodisilane, PCDS = pentachlorodisilane, HCDS = hexachlorodisilane and HSS = higher-boiling silicon compounds). Composition determined by NMR spectroscopy.

Embodiment 5 (according to FIG. 1, implementation 5 )

In a three-necked flask, 304 g of chlorosilane mixture were mixed with 0.4 g of a dimethylamino-functionalized silica (catalyst) at 20 ° C.

After stirring for one week at room temperature, the composition was redetermined (Table 5). The catalyst was filtered off and the mixture was separated by distillation. Three fractions were taken. The third fraction or the bottom contained, in addition to hexachlorodisilane, further higher-boiling silicon compounds. Table 5. Overview of compositions of the mixtures and the fractions of Example 4 (TCS = trichlorosilane, STC = silicon tetrachloride, TCDS = tetrachlorodisilane, PCDS = pentachlorodisilane, HCDS = hexachlorodisilane and HSS = higher boiling silicon compounds). Composition determined by NMR spectroscopy.

Embodiment 6 (according to FIG. 1, implementation 5 )

In a three-necked flask, 305.2 g of chlorosilane mixture were mixed with 0.4 g of a pyridine-functionalized silica (catalyst) at 20 ° C. After one week at room temperature, the composition was redetermined (Table 6). The catalyst was filtered off and the mixture was separated by distillation. Three fractions were taken. The third fraction or the bottom contained, in addition to hexachlorodisilane, further higher-boiling silicon compounds. Table 6. Overview of compositions of the mixtures and the fractions of Example 5 (TCS = trichlorosilane, STC = silicon tetrachloride, TCDS = tetrachlorodisilane, PCDS = pentachlorodisilane, HCDS = hexachlorodisilane and HSS = higher boiling silicon compounds). Composition determined by NMR spectroscopy.

Embodiment 7 (according to FIG. 1, implementation 5 )

In a three-necked flask, 298.4 g of chlorosilane mixed with 0.4 g of a diphenylphosphine-functionalized silica (catalyst) at 20 ° C were added. After one week at room temperature, the composition was redetermined (Table 7). The catalyst was filtered off and the mixture was separated by distillation. Three fractions were taken. The third fraction or the bottom contained, in addition to hexachlorodisilane, further higher-boiling silicon compounds. Table 7. Overview of compositions of the mixtures and the fractions of Example 6 (TCS = trichlorosilane, STC = silicon tetrachloride, TCDS = tetrachlorodisilane, PCDS = pentachlorodisilane, HCDS = hexachlorodisilane and HSS = higher boiling silicon compounds). Composition determined by NMR spectroscopy.

LIST OF REFERENCE NUMBERS

1

Process exhaust area

2

Pre-separation (distillative)

3

separating region

4

separating region

5

implementation

6

reactive distillation

6.1

fraction

6.2

fraction

6.3

fraction

6.4

distillation bottoms

7

distillation

7.1

fraction

7.2

fraction

7.3

distillation bottoms

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 1142848 B [0003]
• EP 1264798 [0006]
• EP 2544795 B1 [0007]
• US 2009/0104100 A1 [0007]
• EP 2036859 B1 [0008]
• DE 3503262 A1 [0009]
• EP 1264798 A1 [0023]

Claims (7)

A process for recovering from hexachlorodisilane contained in process gas streams mixtures of chlorosilanes having the general formula Si _x H _y Cl _{2x + 2-y,} wherein x = = 1 and y = 0-3, and x = 2 and y 0-5, characterized characterized in that the exhaust gas streams or portions thereof are converted into the liquid phase and then the contained in the mixture of chlorosilanes, partially hydrogenated chlorodisilanes of the general formula Si _x H _y Cl _{2x + 2-y} (x = 2, y = 1-5), catalytically are reacted in addition to hexachlorodisilane and separated from the resulting mixture hexachlorodisilane by distillation. A method according to claim 1, characterized in that the transfer of the exhaust gases into the liquid phase is carried out by condensation or absorption in a solvent, and the catalytic reaction at a temperature of 0 to 100 ° C and a pressure up to 20 is carried out bar. A method according to claim 1 or 2, characterized in that the reaction is carried out in a batch or in a continuous process. Method according to one of claims 1 to 3, characterized in that the catalyst is immobilized on inorganic, such as Al ₂ O ₃ , SiO ₂ or organic, such as copolymer of styrene and divinylbenzene, solids, dispersed or dissolved in a mixture of chlorosilanes , Method according to one of claims 1 to 4, characterized in that are used as catalysts - primary, secondary, tertiary amines of the general formula

wherein R1, R2 and R3 are hydrogen, alkyl with C ₁ to C _10, cycloalkyl are equipped with a ring size of 4 to 8, alkenyl with C ₁ to C ₁₀ or aryl having a ring size 4-8, groups and R 1 ≠ R 2 ≠ R 3, R 1 = R 2 ≠ R 3 or R 1 = R 2 = R 3, where the organic radicals may be linear or branched, quaternary amines / ammonium salts of the general formula II

wherein R ₁ , R 2, R 3 and R 4 are hydrogen, alkyl of C ₁ to C ₁₀ , cycloalkyl having a ring size of 4 to 8, alkenyl of C ₁ to C ₁₀ or aryl having a ring size of 4 to 8 groups and A are halides, pseudohalides, phosphates and sulfates and R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 or R1 = R2 ≠ R3 ≠ R4 or R1 = R2 = R3 = R4, where the organic radicals are linear as well as branched may be present, - heterocyclic nitrogen compounds of general formula III

having a ring size of 4 to 8, wherein R ₁ , R 2, R 3 and R 4 are hydrogen, C ₁ to C ₁₀ alkyl, cycloalkyl of 4 to 8, alkenyl of C ₁ to C ₁₀ or aryl a ring size of 4 to 8 groups and R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 or R1 = R2 ≠ R3 ≠ R4 or R1 = R2 = R3 = R4, wherein the organic radicals are linear as well as branched - Heterocyclic aromatic compounds (azines) having one to four nitrogen atoms in the ring, such as pyridine, pyrazine, triazine and their derivatives, their radicals hydrogen, alkyl with C ₁ to C ₁₀ , cycloalkyl having a ring size of 4 to 8, alkenyl with C ₁ to C ₁₀ or aryl can be with a ring size of 4 to 8 groups, wherein the organic radicals may be linear or branched. - Organophosphorus compounds, such as primary, secondary, tertiary phosphines, the general formula IV

wherein R ₁ , R 2 and R 3 are hydrogen, alkyl of C ₁ to C ₁₀ , cycloalkyl of 4 to 8 in ring size, alkenyl of C ₁ to C ₁₀ or aryl of 4 to 8 ring size, and R ₁ ≠ R 2 ≠ R 3, R 1 = R 2 ≠ R 3 or R 1 = R 2 = R 3, where the organic radicals may be linear or branched, and quaternary phosphines of the general formula V

wherein R ₁ , R 2, R 3 and R 4 are hydrogen, alkyl of C ₁ to C ₁₀ , cycloalkyl having a ring size of 4 to 8, alkenyl of C ₁ to C ₁₀ or aryl having a ring size of 4 to 8 groups and A are halides, pseudohalides, phosphates and sulfates and R1 ≠ R2 ≠ R3 ≠ R4, R1 = R2 = R3 ≠ R4 or R1 = R2 ≠ R3 ≠ R4 or R1 = R2 = R3 = R4, where the organic radicals are linear as well may be branched. Method according to one of claims 1 to 5, characterized in that the chlorosilane mixture is mixed with silicon tetrachloride. Method according to one of claims 1 to 6, characterized in that after the catalytic conversion of the chlorosilane mixture, the distillative separation ( 7 ) of the reaction mixture or the catalytic reaction during a reactive distillation ( 6 ) he follows.

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