Process for producing alkylalkoxysilanes

Abstract

A process produces a C.sub.3- to C.sub.20-alkyltrialkoxysilane by hydrosilylation, wherein alkoxy represents methoxy, ethoxy or propoxy. Initially, a mixture is charged of at least one hydroalkoxysilane from the group of hydrotrialkoxysilane, hydroalkyldialkoxysilane, and hydrodialkylalkoxysilane, and a Pt catalyst. The mixture is then heated to a temperature of 30 C. to 60 C. Subsequently, with mixing, an omega-unsaturated or mono-unsaturated C.sub.3- to C.sub.20-hydrocarbon, at least one carboxylic acid and at least one alcohol as cocatalysts are added to the mixture. The mixture is then reacted and subsequently worked up to obtain the product.

Claims

1. A process for producing a C.sub.3- to C.sub.20-alkyltrialkoxysilane by hydrosilylation, wherein alkoxy represents methoxy, ethoxy or propoxy, the process comprising: a) initially charging a mixture of at least one hydroalkoxysilane selected from the group consisting of hydrotrialkoxysilane, hydroalkyldialkoxysilane, and hydrodialkylalkoxysilane, and a Pt catalyst, b) heating the mixture to a temperature of 30 C. to 60 C., c) subsequently, with mixing, adding/metering an omega-unsaturated or mono-unsaturated C.sub.3- to C.sub.20-hydrocarbon, at least one carboxylic acid and at least one alcohol as cocatalysts, and d) reacting the mixture and subsequently working up the mixture.

2. The process according to claim 1, wherein the at least one hydroalkoxysilane and the at least one alcohol are employed in a molar ratio of 1:0.01 to 1:0.2.

3. The process according to claim 1, wherein the at least one hydroalkoxysilane and the Pt catalyst are employed in a molar ratio of 1:110.sup.4 to 1:110.sup.9.

4. The process according to claim 1, wherein the at least one hydroalkoxysilane and the at least one carboxylic acid are employed in a molar ratio of 1:110.sup.3 to 1:1010.sup.3.

5. The process according to claim 1, wherein the at least one hydroalkoxysilane and the C.sub.3- to C.sub.20-hydrocarbon are employed in a molar ratio of 1:1 to 1:1.2.

6. The process according to claim 1, wherein the at least one carboxylic acid is selected from the group consisting of benzoic acid, 3,5-di-tert-butylbenzoic acid, and 3,5-di-tert-butyl-4-hydroxybenzoic acid.

7. The process according to claim 1, wherein the at least one alcohol is at least one C.sub.1-C.sub.10-alcohol.

8. The process according to claim 1, wherein the at least one hydroalkoxysilane is selected from the group consisting of hydrotrimethoxysilane (TMOS), hydrotriethoxysilane (TEOS), methyldiethoxysilane (DEMS), methyldimethoxysilane (DMMS), dimethylethoxysilane (DMES), dimethylmethoxysilane (MDMS), hydrotripropoxysilane, hydromethyldipropoxysilane, and hydrodimethylpropoxysilane.

9. The process according to claim 1, wherein the Pt catalyst is at least one Pt catalyst selected from the group consisting of Karstedt catalyst, hexachloroplatinic(IV) acid, and Pt applied to a solid catalyst support.

10. The process according to claim 1, wherein the process comprises: initially charging and heating the at least one hydroalkoxysilane and the Pt catalyst as a mixture, combining the omega-unsaturated or mono-unsaturated C.sub.3- to C.sub.20-hydrocarbon, the at least one carboxylic acid and the at least one alcohol and metering the combination into the mixture with mixing over a period of 1 to 10 hours at a temperature in the initial charge of 30 C.-60 C., post-reacting the mixture over a period of 0.2 to 2 hours, wherein any heterogeneous catalyst present may optionally be removed from the mixture, performing the subsequent distillative workup of the mixture, and obtaining a target product.

11. The process according to claim 1, wherein 1-hexadecene is employed as the C.sub.3- to C.sub.20-hydrocarbon.

12. The process according to claim 7, wherein the at least one alcohol is t-butanol.

13. The process according to claim 1, wherein the Pt catalyst is at least one Pt catalyst selected from the group consisting of platinum(0) 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex as a Karstedt catalyst, a Speyer catalyst as a hexachloroplatinic(IV) acid catalyst, and Pt applied to activated carbon as a solid catalyst support.

14. The process according to claim 1, wherein the Pt catalyst is at least one Pt catalyst selected from the group consisting of a Karstedt catalyst in xylene or toluene with a Pt(0) content of 0.5% to 5% by weight, and a hexachloroplatinic(IV) acid catalyst dissolved in acetone.

15. The process according to claim 10, wherein the post-reacting step is performed under protective gas.

16. The process according to claim 15, wherein the protective gas is nitrogen.

17. The process according to claim 10, wherein the distillative workup is performed at 45 C.-150 C. and a reduced pressure.

18. The process according to claim 10, wherein the distillative workup removes at least one low boiler selected from the group consisting of: xylene, toluene, alcohol, carboxylic acid, excess hydroalkoxysilane and any olefin component present.

19. The process according to claim 4, wherein the molar ratio is 1:210.sup.3 to 1:610.sup.3.

20. The process according to claim 10, further comprising distilling the target product.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) It has proven particularly advantageous when the present process is preferably performed with a homogeneous platinum(0) complex catalyst, especially a Karstedt catalyst, a Speyer catalyst, hexachloroplatinic(IV) acid or a supported, i.e. heterogeneous, Pt catalyst, for example Pt on activated carbon. A Karstedt catalyst is moreover preferably used in the form of a platinum(0) complex catalyst solution, especially dissolved in xylene or toluene. The present procedure also makes it possible to reduce the content of Pt catalyst and the Pt loss, thus saving costly Pt. It has further proven particularly advantageous in the present process to use a carboxylic acid from the group of benzoic acid, 3,5-di-tert-butylbenzoic acid and/or 3,5-di-tert-butyl-4-hydroxybenzoic acid.

(2) A product mixture obtained by the present process is suitably worked up by distillation, optionally under reduced pressure, and the desired (target) product is obtained. When using a heterogeneous catalyst, this may suitably be separated from the product mixture prior to the distillation, for example by filtration or centrifugation, and this thus-recovered Pt catalyst may advantageously be recycled into the process.

(3) Thus, the target product is obtained as bottoms product in the distillation performed after the reaction and after any removal of a heterogeneous catalyst: the target product is not distilled over in the distillative workup and is obtained as a colourless bottoms product. Should a particularly high purity be required, the product may also be distilled. The present process may moreover be performed particularly economically even at a relatively low temperature of 30-60 C.

(4) In the present process the double bonds of the olefin component used here can thus advantageously be hydrosilylated practically completely and advantageously only very few byproducts are formed.

(5) Furthermore, the present, i.e. inventive, process may advantageously be performed without separate addition of an aliphatic or aromatic hydrocarbon as solvent or diluent and with only a small proportion of the (co)catalyst component carboxylic acid remaining in the target product.

(6) The present invention thus provides a process for producing a C.sub.3- to C.sub.20-alkyltrialkoxysilane by hydrosilylation, wherein alkoxy represents methoxy, ethoxy or propoxy, comprising initially charging a mixture of at least one hydroalkoxysilane from the group of hydrotrialkoxysilane, hydroalkyldialkoxysilane, hydrodialkylalkoxysilane [also referred to hereinbelow as H-silane for short] and a Pt catalyst, heating the mixture to a temperature of 30 C. to 60 C., subsequently, with mixing, adding/metering an omega-unsaturated or mono-unsaturated C.sub.3- to C.sub.20-hydrocarbon [also referred to hereinbelow as olefin component for short], at least one carboxylic acid and at least one alcohol as cocatalysts. reacting the mixture and subsequently working up the thus-obtained product mixture.

(7) In the process according to the invention, H-silane and olefin component are advantageously employed in a molar ratio of 1:1 to 1.2, preferably of 1:1.05 to 1.2, wherein representative and exemplary examples of just some of the possible intermediate values apparent to and derivable by a person skilled in the art from the preceding or present information include in particular 1:1.01, 1:1.03, 1:1.08, 1:1.1, 1:1.13, 1:1.15, 1:1.18.

(8) The H-silane employed is preferably hydrotrimethoxysilane (TMOS), hydrotriethoxysilane (TEOS), methyldiethoxysilane (DEMS), methyldimethoxysilane (DMMS), dimethylethoxysilane (DMES), dimethylmethoxysilane (MDMS), hydrotripropoxysilane, hydromethyldipropoxysilane and/or hydrodimethylpropoxysilane.

(9) The process according to the invention further preferably employs 1-hexadecene as the olefin component.

(10) It is advantageously preferable in the process according to the invention to employ H-silane and alcohol in a molar ratio of 1:0.01 to 0.2, preferably 1:0.02 to 0.18, particularly preferably 1:0.02 to 0.15, very particularly preferably 1:0.025 to 0.1, in particular 1:0.03 to 0.06. The alcohol selected for this purpose is preferably tert-butanol.

(11) It is further advantageous in the process according to the invention to employ H-silane and Pt in a molar ratio of 1:110.sup.4 to 110.sup.9, preferably 1:110.sup.5 to 110.sup.8, in particular of 1:110.sup.5 to 910.sup.6.

(12) The Pt catalyst employed is suitably a heterogeneous Pt catalyst, preferably Pt applied to a solid catalyst support, in particular Pt on activated carbon, or a homogeneous Pt catalyst, preferably a Pt complex catalyst, such as hexachloroplatinic(IV) acid, also known as Speyer catalyst, in particular hexachloroplatinic(IV) acid dissolved in acetone, preferably a Pt(0) complex catalyst, particularly preferably a Karstedt catalyst, very particularly preferably a platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, in particular a Karstedt catalyst in xylene or toluene with a Pt(0) content of 0.5% to 5% by weight. Such a solution generally contains a platinum(0) 3-divinyl-1,1,3,3-tetramethyldisiloxane complex dissolved in xylene or toluene and a solution used in accordance with the invention is advantageously employed in diluted form and preferably has a Pt content of 0.5% to 5% by weight. Thus, in the process according to the invention it is advantageous to use a Pt catalyst from the group of Karstedt catalyst, in particular a Karstedt catalyst solution, preferably platinum(0) 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in xylene or toluene with a Pt(0) content of 0.5% to 5% by weight, hexachloroplatinic(IV) acid, preferably Speyer catalyst, in particular hexachloroplatinic(IV) acid dissolved in acetone, or Pt supported on activated carbon.

(13) Furthermore, in the process according to the invention H-silane and carboxylic acid are preferably employed in a molar ratio of 1:110.sup.3 to 1010.sup.3, particularly preferably 1:110.sup.3 to 810.sup.3, in particular of 1:210.sup.3 to 610.sup.3.

(14) The carboxylic acid is advantageously selected from the group of benzoic acid, 3,5-di-tert-butylbenzoic acid and 3,5-di-tert-butyl-4-hydroxybenzoic acid.

(15) The process according to the invention is preferably performed by initially charging and heating the components H-silane and Pt catalyst as a mixture, combining the olefin component, the carboxylic acid and the alcohol and metering the mixture containing the olefin component, the carboxylic acid and the alcohol into the initial charge with mixing over a period of 1 to 10 hours at a temperature in the initial charge of 30-60 C. and subsequently post-reacting the mixture over a period of 0.2 to 2 hours, wherein the reaction is preferably performed under protective gas, in particular under nitrogen, wherein any heterogeneous catalyst present may optionally be removed from the thus-obtained product mixture, the subsequent distillative workup of the obtained product mixture is preferably performed at 45-150 C. and a reduced pressure, in particular to remove from the product mixture any low boilers present, for example xylene/toluene, alcohol, carboxylic acid, excess H-silane and any olefin component present, and to obtain the (target) product.

(16) The process according to the inventionwith all of its possible combinations of the features detailed in the present descriptionmay therefore generally be performed as follows:

(17) Performing the hydrosilylation according to the invention to produce an alkylmethoxy- or alkylethoxysilane having long alkyl chains comprises initially charging the hydroalkoxysilane (H-silane), preferably trimethoxysilane (TMOS), triethoxysilane (TEOS-H), methyldiethoxysilane (DEMS), methyldimethoxysilane (DMMS), dimethylethoxysilane (DMES), dimethylmethoxysilane (MDMS), hydrotripropoxysilane, hydromethyldipropoxysilane and/or hydrodimethylpropoxysilane, together with a platinum catalyst, suitably a Speyer catalyst, preferably hexachloroplatinic(IV) acid dissolved in acetone or hexachloroplatinic(IV) acid hexahydrate dissolved in acetone, or a Karstedt catalyst, wherein said catalyst is preferably employed as a platinum(0) complex catalyst solution, or Pt on activated carbon in a stirred reactor fitted with metering, heating/cooling, reflux and distillation apparatuses, suitably under protective gas, for example nitrogen, and heating the initially charged mixture advantageously to a temperature of 30 C. to 60 C. This is followed by addition/metering, with mixing, of the olefin component, at least one carboxylic acid, preferably benzoic acid, 3,5-di-tert-butylbenzoic acid and/or 3,5-di-tert-butyl-4-hydroxybenzoic acid and at least one alcohol, for example any of the abovementioned C.sub.1-C.sub.10-alcohols, in particular t-butanol, as a further so-called cocatalyst: The components olefin, carboxylic acid and alcohol may be added or metered into the hydroalkoxysilane/platinum(0) complex catalyst mixture of the initial charge portionwise or continuously individually in succession or advantageously in the form of an olefin/carboxylic acid/alcohol mixture over a defined period, preferably under temperature control and over 1 to 10 or more hours, wherein the metering time may, however, be dependent on the batch size and the reactor design, and the reaction/product mixture is post-reacted, preferably with mixing and under temperature control, suitably at a temperature of 60-100 C., in particular over 0.5 to 2 hours. Thus, in the present processes the respective input materials are preferably employed in a well-defined molar ratio: H-silane to olefin component in a molar ratio of 1:1 to 1.2 H-silane to alcohol in a molar ratio of 1:0.01 to 0.2 H-silane to Pt in a molar ratio of 1:110.sup.4 to 110.sup.9 H-silane to carboxylic acid in a molar ratio of 1:110.sup.3 to 1010.sup.3

(18) The employed Karstedt catalyst solution is further preferably produced from a commercially available so-called Karstedt concentrate (platinum(0) 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, platinum content: 20.37% by weight), wherein the concentrate is preferably adjusted to a Pt content of 0.5% to 5% by weight by the addition of xylene or toluene. A thus-obtained product mixture is suitably worked up by distillation to obtain the desired (target) product. To this end, the distillation is preferably performed starting at 45 C. to 150 C. and a reduced pressure (vacuum distillation at less than 1 bar and falling, in particular not more than 0.1 bar) thus removing in particular any low boilers, for example alcohol, excess H-silane and any remaining olefin component, from the product mixture. If a heterogeneous Pt catalyst is used for performing the process according to the invention, the heterogeneous Pt catalyst may be separated from the product mixture obtained after the reaction in the course of the product workup, i.e. prior to the distillation step, for example by filtration or centrifugation, and advantageously recycled back into the process. However, to achieve higher purities, the product may also be distilled overhead.

(19) Thus, according to the invention, alkylalkoxysilanes having a long chain alkyl group, in particular a hexadecyltrimethoxysilane and a hexadecyltriethoxysilane, may be produced in particularly simple and economic fashion in high yield and selectivity, i.e. with only small proportions of byproducts, advantageously also on a large industrial scale.

(20) The examples which follow provide additional elucidation of the present invention without limiting the subject matter thereof:

EXAMPLES

(21) Analytical Investigations

(22) The progress of the reactions was followed by means of GC measurements.

(23) GC column: HP-5; length: 30 m; diameter: 530 m

(24) Injection volume: 0.4 l

(25) Temperature program: 120 C.2 min.15 C./min.275 C.20 min.

(26) Chemicals Used:

(27) Karstedt concentrate (platinum(0) 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex,

(28) platinum content: 20.37% by weight), HERAEUS

(29) Acetone, pure, LABC Labortechnik

(30) Hexachloroplatinic(IV) acid hexahydrate, platinum content 40% by weight. HERAEUS Platinum-activated carbon, hydrogenation catalyst, platinum content 10% by weight, MERCK

(31) Xylene Technical, VWR Chemicals

(32) Dynasylan TMOS (trimethoxysilane), EVONIK Industries

(33) Dynasylan TEOS-H (triethoxysilane), EVONIK Industries

(34) Dynasylan DEMS (methyldiethoxysilane). EVONIK Industries

(35) Dynasylan DMES (dimethylethoxysilane), EVONIK Industries

(36) 1-Hexadecene, Dow Corning

(37) Benzoic acid 99.5% by weight, ROTH

(38) 3,5-Di-tert-butylbenzoic acid >98.0% by weight, TOKYO CHEMICAL INDUSTRY

(39) 3,5-Di-tert-butyl-4-hydroxybenzoic acid, >98.0% by weight, TOKYO CHEMICAL INDUSTRY

(40) Acetic acid, 99% by weight, SIGMA-ALDRICH

(41) tert-Butanol, 99.0% by weight (for synthesis). ROTH

(42) Production of Karstedt-Catalyst No. 1 with 2% by Weight Platinum Content in Xylene:

(43) In a 0.2 l glass bottle, 9.8 g of Karstedt concentrate (platinum(0) 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, platinum content 20.37%) were mixed with 90.2 g of xylene.

Comparative Example 1 Based on U.S. Pat. No. 5,986,124, Example 1, and with a Reduced Proportion of Carboxylic Acid

(44) 128.3 g of Dynasylanl TMOS (1.05 mol) and 0.2 g of Karstedt catalyst (corresponds to 0.02563 mmol of Pt) were initially charged in a 0.5 l stirred apparatus fitted with a reflux condenser and metering apparatus. At a temperature of 41-56 C. a mixture consisting of 224.4 g of hexadecene (1.0 mol) and 0.393 g of acetic acid (6.55 mmol) was metered in over 39 minutes. Thereafter, the mixture was held at 55 C. for a further hour. Subsequently, 17.2 g of low boilers were removed at 76-123 C. and a pressure of <0.1 mbar. 331.3 g of bottoms product were obtained.

(45) GC analysis of the bottoms product showed the following composition:

(46) TABLE-US-00001 Sum of C16 n-C16- Sum of C16 Remainder olefin GC- silane GC- silane GC- GC-WLD- WLD-FL % WLD-FL % WLD-FL % FL % 9.8 89.0 89.5 0.7

Example 1

(47) 128.3 g of Dynasylan TMOS (1.05 mol) and 0.2 g of Karstedt catalyst (corresponds to 0.02563 mmol of Pt) were initially charged in a 0.5 l stirred apparatus fitted with a reflux condenser and metering apparatus. At a temperature of 33-48 C., a mixture consisting of 224.4 g of 1-hexadecene (1.0 mol), 0.800 g of benzoic acid (6.55 mmol) and 2.5 g of t-butanol (33.73 mmol) was metered in over 2 hours. Thereafter, the mixture was held at 47 C. for a further hour. Subsequently, 12.1 g of low boilers were removed at 42-111 C. and a pressure of <0.1 mbar. 339.8 g of bottoms product were obtained. GC analysis of the bottoms product showed the following composition:

(48) TABLE-US-00002 Sum of C16 n-C16- Sum of C16 Remainder olefin GC- silane GC- silane GC- GC-WLD- WLD-FL % WLD-FL % WLD-FL % FL % 5.8 89.6 92.7 1.5

Example 2

(49) 128.3 g of Dynasylan TMOS (1.05 mol) and 0.2 g of Karstedt catalyst (corresponds to 0.02563 mmol of Pt) were initially charged in a 0.5 l stirred apparatus fitted with a reflux condenser and metering apparatus. At a temperature of 48-57 C., a mixture consisting of 224.4 g of 1-hexadecene (1.0 mol), 1.64 g of 3,5-di-tert-butylhydroxybenzoic acid (6.55 mol) and 2.5 g oft-butanol (33.73 mmol) was metered in over 1 and hours. Thereafter, the mixture was held at 55 C. for a further hour. Subsequently, 13.9 g of low boilers were removed at 31-110 C. and a pressure of <0.1 mbar. 337.4 g of bottoms product were obtained. GC analysis of the bottoms product showed the following composition:

(50) TABLE-US-00003 Sum of C16 n-C16- Sum of C16 Remainder olefin GC- silane GC- silane GC- GC-WLD- WLD-FL % WLD-FL % WLD-FL % FL % 6.3 91.0 92.9 0.8

Example 3

(51) 172.5 g of Dynasylan TEOS (1.05 mol) and 0.2 g of Karstedt catalyst (corresponds to 0.02563 mmol of Pt) were initially charged in a 1 l stirred apparatus fitted with a reflux condenser and metering apparatus. At a temperature of 45-46 C., a mixture consisting of 224.4 g of 1-hexadecene (1.0 mol), 0.800 g of benzoic acid (6.55 mmol) and 2.5 g of t-butanol (33.73 mmol) was metered in over 1 hour. Thereafter, the mixture was held at 46 C. for a further hour. Subsequently, 20.1 g of low boilers were removed at 58-144 C. and a pressure of <0.1 mbar. 376.4 g of bottoms product were obtained. GC analysis of the bottoms product showed the following composition:

(52) TABLE-US-00004 Sum of C16 n-C16- Sum of C16 Remainder olefin GC- silane GC- silane GC- GC-WLD- WLD-FL % WLD-FL % WLD-FL % FL % 5.3 91.2 94.1 0.6

Example 4

(53) 141.0 g of Dynasylan DEMS (1.05 mol) and 0.2 g of Karstedt catalyst (corresponds to 0.02563 mmol of Pt) were initially charged in a 1 l stirred apparatus fitted with a reflux condenser and metering apparatus. At a temperature of 41-47 C., a mixture consisting of 224.4 g of 1-hexadecene (1.0 mol), 0.800 g of benzoic acid (6.55 mmol) and 2.5 g of t-butanol (33.73 mmol) was metered in over 1 hour. Thereafter, the mixture was held at 46 C. for a further hour. Subsequently, 16.3 g of low boilers were removed at 40-125 C. and a pressure of <0.1 mbar. 348.1 g of bottoms product were obtained. GC analysis of the bottoms product showed the following composition:

(54) TABLE-US-00005 Sum of C16 n-C16- Sum of C16 Remainder olefin GC- silane GC- silane GC- GC-WLD- WLD-FL % WLD-FL % WLD-FL % FL % 5.1 91.8 94.1 0.8

(55) The experimental results in terms of yield and selectivity from the examples recited hereinabove are summarized in the table which follows.

(56) The process according to the invention thus advantageously makes it possible to achieve a further improvement in yield and product selectivity.

(57) TABLE-US-00006 n-C.sub.16- Sum of C.sub.16- Experiment No. C.sub.16-Olefin Alkylalkoxysilne alkylalkoxysilane Remainder (Product) GC-WLD-FL % GC-WLD-FL % GC-WLD-FL % GC-WLD-FL % Comparative example 1 9.8 89.0 89.5 0.7 (hexadecyltrimethoxysilane) Example 1 5.8 89.6 92.7 1.5 (hexadecyltrimethoxysilane) Example 2 6.3 91.0 92.9 0.8 (hexadecyltrimethoxysilane) Example 3 5.3 91.2 94.1 0.6 (hexadecyltriethoxysilane) Example 4 5.1 91.8 94.1 0.8 (hexadecylmethyldiethoxysilane)

(58) The inventive experiments show that through the combination of the measures procedure/process conditions, reduction of cocatalyst proportion carboxylic acid based on the H-silane, and addition of a further cocatalyst in the form of an alcohol, it is possible to achieve a further improvement in the yield of target product coupled with a reduction in the proportion of carboxylic acid remaining in the product.