Process for the dehydrogenation and methylation of silanes with chloromethane

Abstract

The present invention relates to a method for dehydrogenating and methylating silanes, wherein chloromethane is reacted with a silane selected from SiH4, H2SiMe2, H2SiMeCl, H3SiMe, H3SiCl, HSiMe2Cl and HSiMeCl2 in the presence of at least one ammonium salt and / or phosphonium salt at a temperature in the range of 70-350°C.

Description

Technical Field

[0001] The present invention relates to a method for dehydrogenating and methylating silanes with chloromethane (MeCl) in the presence of at least one ammonium salt and / or phosphonium salt at a temperature in the range of 70°C to 350°C. Background Technology

[0002] Methylchlorosilanes (MCS) are used, for example, in the production of silicones, for hydrophobication, and in organic synthesis.

[0003] The only way to efficiently form Me-Si bonds on an industrial scale is through the Müller-Rochow method. The Müller-Rochow method involves elemental silicon and simple organochlorine compounds such as MeCl.

[0004] However, the Rogjo-Müller method cannot convert methyl-H-silanes or H-silanes into methylated and more methylated methylchlorosilanes (MCS).

[0005] Methods for chloride-catalytic dehydrogenation of H-containing silanes are known from the literature:

[0006] US 2002 / 0082438 A1 describes the synthesis of organochlorosilanes starting from trichlorosilane, dichlorosilane, or dichloromethylsilane. Another starting material used is of formula R. 2 R 3 A CHX haloalkane, where X = Cl or Br, and R... 2 Selected from (C) 1-17 )-alkyl, having partially or fully fluorinated (C 1-10 )-fluorinated alkyl groups, (C 1-5 )-Alkenyl, (CH2) n SiMe 3-m Cl m (where n = 0 - 2 and m = 0 - 3), (CH2) p X (where p = 1-9 and X = Cl or Br), or ArCH2X (where Ar = aromatic (C) 6-14 )-hydrocarbon and X = Cl or Br), and R 3 Selected from H, (C 1-6 )-alkyl, Ar(R')q (where Ar = aromatic (C 6-14 )-hydrocarbon, R=(C 1-4 (α-alkyl, halogen, alkoxy, or vinyl, q = 0-5). Various quaternary phosphonium halides are used as catalysts. The reaction mechanism is assumed to be a dehydrochlorination reaction, in which hydrogen chloride is eliminated in all reactions.

[0007] PCT / EP2008 / 073933 discloses the reaction of dichlorosilane with (i) hydrogen halide or (ii) a haloalkane having the chemical formula (I) (including chloromethane). Summary of the Invention

[0008] Therefore, the object of the present invention is to provide a method for economically producing methylchlorosilane from H-containing silanes.

[0009] This objective is achieved by a method for dehydrogenating and methylating silanes, wherein chloromethane is reacted with a silane selected from the group consisting of SiH4, H2SiMe2, H2SiMeCl, H3SiMe, H3SiCl, HSiMe2Cl and HSiMeCl2 in the presence of at least one ammonium salt and / or phosphonium salt at a temperature in the range of 70-350°C.

[0010] In the method according to the invention, methyl chloride (MeCl) reacts with a silane selected from the group consisting of SiH4, H2SiMe2, H2SiMeCl, H3SiMe, H3SiCl, HSiMe2Cl and HSiMeCl2 in the presence of at least one ammonium salt and / or phosphonium salt as a catalyst.

[0011] In the first reaction step, an inseparable intermediate is first formed by removing hydrogen from the silane. This anion can be further reacted by formal nucleophilic substitution, or it can be inserted as a methylene silylene group. In the case of reaction with MeCl, the product is always a silane with additional methyl and Cl functional groups in each case. In both cases, chloride ions are released again, which can then be used as a catalyst.

[0012] In the method according to the invention, the catalyst used is at least one ammonium salt and / or phosphonium salt. This ammonium salt and / or phosphonium salt can also be used in immobilized form, for example, on a silicone resin, on silica, on an inorganic support, or on an organic polymer. The ammonium salt and / or phosphonium salt can also be formed in situ from an amine or phosphine and HCl.

[0013] The ammonium salt and / or phosphonium salt are preferably selected from the group consisting of: quaternary ammonium halides [R4N]X, quaternary phosphonium halides [R4P]X, and tertiary ammonium halides [R3NH]X, wherein in each case:

[0014] X = Cl, Br, or I, preferably Cl or Br, and

[0015] R = independently selected from (i)C1-C 12 -alkyl, (ii) C6-C substituted with C1-C6-alkyl14 -aryl, and (iii)phenyl, preferably ethyl, n-butyl and phenyl.

[0016] Particularly preferred examples of these compounds are [n-Bu4N]Cl, [Et4N]Cl, [Ph4P]Cl, and [n-Bu4P]Cl.

[0017] The method according to the invention is typically carried out at temperatures ranging from 70°C to 350°C, depending on the thermal stability of the catalyst. The temperature is preferably in the range of 100-350°C. For [n-Bu4N]Cl, [Et4N]Cl, and [n-Bu4P]Cl, the temperature is particularly preferably in the range of 100-180°C; very particularly preferably, the temperature is in the range of 150-180°C; and most preferably, the temperature is 170-180°C. For [Ph4P]Cl, the temperature is particularly preferably in the range of 70-350°C, and very particularly preferably in the range of 250-350°C.

[0018] The molar ratio of silane to MeCl can be freely chosen by those skilled in the art. Typically, this molar ratio is in the range of 1:1 to 1:10. In the case of all silanes with groups other than SiH4, the amount of MeCl added preferably corresponds to at least the stoichiometric amount of the silane to be converted; therefore, the molar ratio is preferably 1:1 to 1:2. In the case of SiH4, the amount of MeCl added preferably corresponds to at least twice that amount; therefore, the molar ratio is preferably 1:2 to 1:4.

[0019] The molar ratio of catalyst to silane can be freely selected by those skilled in the art. Preferably, the molar ratio is in the range of 0.01:1 to 0.2:1.

[0020] The method for dehydrogenating silane according to the present invention can be used to produce methylchlorosilane in an economically feasible manner. Detailed Implementation

[0021] Example

[0022] An Agilent 6890N (WLD detector; column: HP5 from Agilent: length: 30 m / diameter: 0.32 mm / film thickness: 0.25 μm; RTX-200 from Restek: length: 60 m / diameter: 0.32 mm / film thickness: 1 μm) was used. Retention times were compared to commercially available substances; all chemicals were used as purchased. MS measurements were performed using a ThermoStar with an iridium cathode. TM GSD320T2 is being used.

[0023] Example 1: Reaction of SiH4 with MeCl

[0024] SiH4 (9 g; 0.50 mol), [n-Bu4P]Cl (2.1 g; 7 mmol), and MeCl (64.0 g; 1.27 mol) were added to an autoclave. The autoclave was heated to 150 °C for 13 hours. After cooling, the pressure in the autoclave was maintained at approximately 30 bar. The pressure was reduced to 10 bar by depressurization, and the autoclave was then reheated to 150 °C for 13 hours. After cooling, the pressure in the autoclave was maintained at approximately 15 bar. The autoclave was depressurized and the gas space was purged with argon. The liquid product mixture consisted of the following components by weight: 60% HSiMeCl2, 14% MeSiCl3, 10% H2SiMeCl, 8% Me2SiCl2, 4% MeCl, and 4% other chlorinated, methylated, and / or methylene-substituted silanes. The gas formed in the reaction was definitively identified as hydrogen by mass spectrometry.

[0025] Example 2: Reaction of SiH4 with MeCl

[0026] SiH4 (9 g; 0.34 mol), [n-Bu4P]Cl (2.2 g; 7 mmol), and MeCl (48.0 g; 0.95 mol) were added to an autoclave. The autoclave was heated to 145 °C for 13 hours. After cooling, the pressure in the autoclave was maintained at approximately 25 bar. The autoclave was then depressurized and the gas space was purged with argon. The liquid product mixture consisted of, to a certain extent, 89% MeSiCl3, 9% MeCl, and 2% Me2SiCl2 by weight; in addition, a small amount of HSiMeCl2 was detectable. The gas formed in the reaction was definitively identified as hydrogen by mass spectrometry.

[0027] Example 3: Reaction of SiH4 with MeCl

[0028] SiH4 (7 g; 0.34 mol), [Ph4P]Cl (2.1 g; 6 mmol), and MeCl (25.0 g; 0.50 mol) were added to an autoclave. The autoclave was heated to 300 °C for 13 hours. After cooling, the pressure in the autoclave was maintained at approximately 25 bar. The autoclave was then depressurized and the gas space was purged with argon. The liquid product mixture consisted of 56% MeSiCl3, 2% MeCl, and 42% Me2SiCl2 by weight; in addition, a small amount of HSiMeCl2 was detectable. The gas formed in the reaction was definitively identified as hydrogen by mass spectrometry.

[0029] Example 4: Reaction of a mixture of SiH4 and SiCl4 with MeCl

[0030] SiH4 (9 g; 0.34 mol), [n-Bu4P]Cl (2.2 g; 0.7 mmol), MeCl (70.0 g; 1.38 mol), and SiCl4 (50.0 g; 0.29 mol) were added to an autoclave. The autoclave was heated to 190 °C for 13 hours. After cooling, the pressure in the autoclave was maintained at approximately 50 bar. The autoclave was depressurized and the gas space was purged with argon. The liquid product mixture consisted of 48% SiCl4, 47% MeSiCl3, 3% MeCl, and 2% Me2SiCl2 by weight; in addition, trace amounts of HSiMeCl2 and SiCl4 were detectable. The gas formed in the reaction was definitively identified as hydrogen by mass spectrometry.

[0031] Example 5: Reaction of HSiCl2Me with MeCl

[0032] HSiCl2Me (85 g; 0.75 mol), [n-Bu4P]Cl (2.1 g; 7 mmol), and MeCl (50.0 g; 0.99 mol) were charged into an autoclave. The autoclave was heated to 130 °C for 13 hours. After cooling, the pressure in the autoclave was maintained at approximately 5 bar. The autoclave was depressurized and the gas space was purged with argon. The liquid product mixture consisted of, by weight, 56% HSiCl2Me, 31% MeSiCl3, 7% Me2SiCl2, 5% MeCl, and 1% other chlorinated, methylated, and / or methylene-substituted silanes. The gas formed in the reaction was definitively identified as hydrogen by mass spectrometry.

[0033] Example 6: Reaction of HSiCl2Me with MeCl

[0034] HSiCl2Me (85 g; 0.75 mol), [n-Bu4P]Cl (2.5 g; 8 mmol), and MeCl (51.0 g; 1.01 mol) were charged into an autoclave. The autoclave was heated to 176 °C for 13 hours. After cooling, the pressure in the autoclave was maintained at approximately 20 bar. The autoclave was depressurized and the gas space was purged with argon. The liquid product mixture consisted of, by weight, 16% HSiCl2Me, 41% MeSiCl3, 33% Me2SiCl2, 9% MeCl, and 1% other chlorinated, methylated, and / or methylene-substituted silanes. The gas formed in the reaction was definitively identified as hydrogen by mass spectrometry.

[0035] Example 7: Reaction of HSiClMe2 with MeCl

[0036] HSiCl2Me (85 g; 0.75 mol), [n-Bu4P]Cl (2.5 g; 8 mmol), and MeCl (48.0 g; 0.95 mol) were charged into an autoclave. The autoclave was heated to 176 °C for 13 hours. After cooling, the pressure in the autoclave was maintained at approximately 30 bar. The autoclave was then depressurized and the gas space was purged with argon. The liquid product mixture consisted of, by weight, 16% HSiClMe2, 67% Me2SiCl2, 7% Me3SiCl, 9% MeCl, and 1% other chlorinated, methylated, and / or methylene-substituted silanes. The gas formed in the reaction was definitively identified as hydrogen by mass spectrometry.

Claims

1. A method for dehydrogenating and methylating silane, wherein chloromethane is reacted with SiH4 in the presence of a catalyst, wherein the molar ratio of SiH4 to chloromethane is in the range of 1:1 to 1:10, excluding 1:1, wherein the catalyst is selected from […]. n -Bu4N]Cl, [Et4N]Cl, [Ph4P]Cl and [ n -Bu4P]Cl, for [ n -Bu4N]Cl, [Et4N]Cl and [ n -Bu4P]Cl reacts in the temperature range of 150°C-180°C, while [Ph4P]Cl reacts in the temperature range of 250-350°C.

2. The method of claim 1, wherein the molar ratio of the catalyst to SiH4 is in the range of 0.01:1 to 0.2:

1.

3. The method of any one of claims 1 to 2, wherein the method is performed continuously or in batches.