JP6538476B2 - Method for producing siloxane compound and gold catalyst used therefor - Google Patents

Description

  The present invention uses a fine particle of gold supported on a carbon carrier as a catalyst, a solvent, and water as an oxidizing agent to synthesize a siloxane compound from a silane compound at a high efficiency under an inert gas atmosphere at room temperature. It relates to catalytic reaction technology that can be done with high safety and low environmental impact.

  Various methods have been considered for the catalytic reaction for synthesizing a siloxane compound from a silane compound. Examples of such catalytic reactions include an example of using a homogeneous catalyst and an example of using a heterogeneous catalyst. As an example using a homogeneous catalyst, there is known one as described in Non-Patent Document 1 in which safe and inexpensive water is used as a reaction solvent. However, when a homogeneous catalyst is used, it is difficult to separate the catalyst component from the catalytic reaction system. In addition, when separating the catalyst from the reaction system, the structure of the catalyst may change, which makes it difficult to reuse the catalyst, particularly when using a catalyst containing a noble metal component as a homogeneous catalyst. Incurs soaring manufacturing costs. Moreover, the yield of the target siloxane compound was also low.

  On the other hand, as an example of synthesizing a siloxane compound from a silane compound using a heterogeneous catalyst, a reaction using metal palladium as a catalyst is known (Non-Patent Document 2, Non-Patent Document 3). In Non-Patent Document 3, water is also used together with metallic palladium. Thus, the catalyst in the case of using a heterogeneous catalyst is separable from the reaction system by filtration and is easy to reuse. However, in the reaction example using the conventional heterogeneous catalyst, there are also cases where solvents that may cause toxicity or ignition are used for the reaction, and there have been problems in industrial use from the environmental aspect and safety aspect. In addition, satisfactory results have not yet been obtained.

  In recent years, gold has attracted attention as a catalytically active species. Gold was once said to be chemically inert and unsuitable as a catalyst, but when it comes to very small nanoparticles with a diameter of 2 to 5 nm, oxidative decomposition of harmful substances at room temperature, In recent years, it has become known that the catalyst can be used as a catalyst in chemical processes, such as the synthesis of chemical products by selective oxygen oxidation and hydrogenation. (Patent Document 1) As such a gold catalyst, an oxidation catalyst is implemented as its main use.

Unexamined-Japanese-Patent No. 09-122478 gazette

Organic Letters, (2012), 14 (10), 2642-2645. Journal of the American Chemical Society, (2013), 135 (42), 15714-15717. ChemCatChem, (2012), 4 (4), 521-524.

  An object of the present invention is to provide a technology for synthesizing a siloxane compound from a silane compound with high efficiency under a safe and low environmental load condition using a catalytic reaction.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors surprisingly found that the gold catalyst, which has been mainly examined so far for use as an oxidation catalyst, unexpectedly contains siloxane compounds from silane compounds in the presence of water. They found that they could be synthesized with high efficiency, and completed the present invention. The present invention has also been completed by finding that the above synthesis reaction proceeds even with a gold catalyst in which gold particles of crystallite size larger than those hitherto known are supported on a carbon carrier.

  That is, the present invention is a method for producing a siloxane compound, characterized in that a silane compound is brought into contact with a gold catalyst having nano-sized gold particles supported on a carbon support using water as a solvent in an inert gas atmosphere.

  The present invention is also a gold catalyst in which nanosized gold particles are supported on a carbon carrier, and is a gold particle characterized in that the crystallite size is 10 to 100 nm.

  According to the present invention, by using a gold catalyst in which nanosized gold is supported on a carbon support, it is safe and inexpensive as a solvent, and high yield can be obtained in a short time even using water having a function as an oxidizing agent. A siloxane compound can be obtained from a silane compound.

  In addition, it is possible to use a gold catalyst supported on a carbon support with gold particles having a large gold crystallite size which has not been known to have activity as a catalyst until now.

  The catalyst used in the method for producing a siloxane compound of the present invention (hereinafter referred to as "the present method") is a gold catalyst (hereinafter referred to as "Au /") in which nanosized gold (Au) particles are supported on a carbon (C) carrier. C)).

  Conventionally, it is known that a catalyst supporting very small nano-sized gold particles of 2 to 5 nm has activity as an oxidation catalyst, but such catalyst is disiloxane by coupling from phenylsilane It is not known to synthesize. Further, a catalyst carrying gold particles of a size of more than 10 nm was originally said to have no activity as a catalyst.

  In the method of the present invention, Au / C having any nanosized gold particle supported on a carbon support can be used without particular limitation, but the crystallite size of the gold particle is, for example, 1 to 100 nm, preferably Is 10 to 100 nm. The definition of crystallite size and particle size may differ depending on the technical field, but in general, in the field of catalyst technology, the crystallite size refers to the size of the single crystal constituting the particle. A particle composed of such a single crystal as a minimum unit is called a particle diameter. In other words, the gold particles in Au / C are a set of one or more gold crystallites, and the size of the gold crystallite size is necessarily equal to or less than the gold particle size. For example, as in the example described later, when the gold crystallite size is 31.6 nm, it can be said that the particle diameter is necessarily larger than that. The gold crystallite size refers to the value derived from the Scherrer equation from the results measured by X-ray diffraction.

The carbon support used for Au / C used in the method of the present invention is not particularly limited, but is preferably a carbon support having a large specific surface area (BET), for example, a BET 500 to 2500 m ² / g carbon support, preferably 700 to 1500 m ² / g carbon support. When a carbon support having an excessively small BET value is used, if the specific surface area value is too small, the dispersibility of gold may be reduced and the reactivity may be reduced, or in the process for producing a catalyst described later. It may be difficult to obtain nano-sized gold particles. Although the reason is not clear, the reactivity may be lowered in the method of the present invention even if the specific surface area is too large. In addition, BET value makes nitrogen adsorb to a solid surface, measures the specific surface area of a solid from the amount of adsorption, and is measured using a specific surface area measuring device or a gas adsorption device.

  Further, the particle diameter of the carbon support is not particularly limited, but for example, the distribution (50% particle size distribution) of the particle diameter of 50% or more of all carbon particles is included in the range of 1 to 500 μm. Preferably, it is more preferably contained in the range of 5 to 100 μm. If the 50% particle size distribution is too small, separation of the catalyst after the reaction may be difficult and recycling of the catalyst may be difficult. If the particle size of the 50% particle size distribution is too large, the surface area of Au / C per unit volume may be small, and the activity of the catalyst may be reduced. The 50% particle size distribution is measured by a laser diffraction method. This is because when a particle is irradiated with a monochromatic laser, diffracted light and scattered light are generated according to the size of the particle, so the particle size distribution is determined by analyzing the diffraction and scattering intensity distribution of the light, particle size It measures using a distribution measuring device.

  Examples of such a carbon support include activated carbon, carbon nanotubes, graphite, graphene and the like, but from the wide range of physical property values such as availability, BET value, breadth of selection of particle size, etc. It is preferred to use activated carbon. Moreover, as origin of activated carbon, it does not specifically limit, For example, the thing derived from plant raw materials, such as large saw powder and coconut shell, The thing derived from petroleum raw materials, such as a hydrocarbon, etc. are mentioned.

  In addition, although the said carbon support may contain components other than carbon, it is preferable that the component and content do not inhibit the activity of a catalyst. As such components, for example, hydrogen, oxygen, silicon, aluminum and the like have limited effect on the catalyst activity, and alkali metals, alkaline earth metals, and sulfur described later inhibit the catalyst activity. It is desirable not to include it or to reduce its content.

  In addition, it is preferable that the carbon support does not contain components that may inhibit the activity of the catalyst, such as sodium (Na), sulfur (S), magnesium (Mg), calcium (Ca) and the like. In particular, the alkali component such as sodium is, for example, preferably 0.2 wt% or less in terms of element in the carbon support, and more preferably 0.1 wt% or less. In order to reduce the alkali component from the carbon carrier, the operation such as washing with pure water at 70 to 80 ° C. may be performed once to a plurality of times as necessary.

  The amount of gold supported on Au / C used in the method of the present invention is not particularly limited, but is, for example, 1 to 20 wt%, preferably 2 to 15 wt%, more preferably 5 to 15 wt% in terms of metal relative to the carbon support. %. The yield can be expected to be improved by containing a certain amount or more of gold as the active species, and by keeping the gold content to a certain extent or less, the dispersibility of gold is maintained high and the activity in Au / C is improved. I can expect it. Gold is more stable than platinum and palladium, and can easily maintain a so-called metal state. By limiting the content of such gold, it is possible to suppress aggregation of the gold in the production process or reaction process of the catalyst such as Au / C, and to maintain high dispersibility.

  Among the Au / C catalysts used in the method of the present invention, those having a crystallite size of, for example, 1 to 10 nm or less are, for example, K-Type from N. Chemcat, and RR from Haltagord. What is marketed, for example, may be prepared by the method described in Example 8 of JP-A-2009-240951.

  On the other hand, among the Au / C catalysts used in the method of the present invention, for example, those having a crystallite size of 10 to 100 nm can be prepared as follows.

  First, a suspension in which a carbon carrier is suspended in a solvent in which a gold salt is soluble is prepared. Separately from this suspension, a gold salt solution in which a gold salt is dissolved is prepared. The suspension and gold salt solution are mixed, and gold is immobilized on a carbon carrier. Thus, Au / C having a crystallite size of 10 to 100 nm can be obtained by washing the gold supported on the carbon support with a suitable solvent.

  As a gold salt used above, chloroauric acid, tetrabromoaurate (III) acid, sodium tetrabromoaurate (III), potassium tetrabromoaurate (III), potassium dicyanoaurate (I), dicyanoaurate (I) Ammonium phosphate, sodium dicyanogold (I), potassium tetracyanogold (III), sodium tetracyanogold (III), ammonium tetracyanogold (III), gold (III) acetate, gold (III) nitrate, bis (ethylenediamine) ) Gold (III) acid chloride etc. may be mentioned, and it may be appropriately selected from the above options in view of compatibility with the carrier, reducing conditions etc. It is easy.

  As the solvent in which the gold salt used is soluble, water, methanol, ethanol, acetic acid, dimethylformamide, dimethylacetamide, ethylene glycol, glycerin and the like can be used, but it is easy to handle. It is preferable to use water, and it is preferable to use a gold salt that is soluble in water.

  The carbon carrier may be suspended in the above solvent by mixing and stirring the solvent and the carbon carrier, but if necessary, the interface of sodium stearate, sodium oleate, cetyltrimethyl ammonium bromide, etc. Activators and pH adjusters such as sodium hydrogencarbonate, sodium carbonate, sodium metaborate, sodium tetraborate, monosodium citrate and disodium citrate may be used.

  The solution in which the gold salt is dissolved may be selected appropriately from among the above solvents to dissolve the gold salt.

  Although the method of mixing the said suspension and a gold salt solution and immobilizing gold on a carbon support is not particularly limited, for example, a reducing agent described later may be added to this mixed solution to immobilize.

  As a reducing agent used for immobilization, sodium borohydride, sodium formate, formic acid, formaldehyde, oxalic acid, sodium oxalate, hydrazine hydrate, hydrazine hydrochloride, hydroxylamine, hydrogen peroxide, hydrogen peroxide, ascorbic acid, ascorbic acid Sodium, citric acid, malic acid, tartaric acid and the like can be mentioned. In the reduction, if necessary, the pH of the mixed solution may be adjusted using a conventionally known pH adjuster. For example, when using sodium borohydride as a reducing agent, in order to prevent the decomposition | disassembly in the aqueous solution of sodium borohydride, it is preferable to make pH high using the sodium hydroxide which is a pH adjuster.

  As a solvent used to wash gold supported on a carbon carrier, it is desirable to use hot pure water of 70 to 80 ° C. The washing method is not particularly limited, and mixing with warm pure water, stirring, filtration may be repeated, or washing with water may be performed in a filtration device.

  After washing, drying etc. may be performed as appropriate. The conditions in the case of drying are not particularly limited, and in the case of using water as a solvent, for example, drying may be performed at 90 to 110 ° C. in the atmosphere until the predetermined water content is achieved.

  The Au / C of the present invention is highly durable and can be reused multiple times.

  In addition, it can be confirmed that the Au / C having a crystallite size of 10 to 100 nm is generated by measurement of X-ray diffraction or the like.

The silane compound to be a substrate in the method of the present invention is not particularly limited, and examples thereof include silane compounds such as arylsilanes and alkylsilanes. Among these silane compounds, arylsilanes are preferred, and phenylsilane represented by the following formula (1) is particularly preferred.

Here, R ¹ represents a phenyl group which may have a substituent, and R ² and R ³ may each independently have hydrogen, an alkyl group having 1 to 3 carbon atoms, or a substituent. Represents a phenyl group. Incidentally, the substituents R ² and R ³ are as desirably low bulk, preferably those having 5 or less carbon atoms, more preferably of 2 or less carbon atoms. In addition, such a substituent is preferably linear.

  Specific examples of such phenylsilanes include dimethylphenylsilane, dimethyl (4-methoxyphenyl) silane, dimethyl (4-methylphenyl) silane, dimethyl (4-fluorophenyl) silane and dimethyl (4-bromophenyl). Silane, dimethyl (4-chlorophenyl) silane, dimethyl (4-trifluoromethylphenyl) silane, dimethyl (4-tertbutyldimethylsiloxymethylphenyl) silane, diethylphenylsilane, di-n-butylphenylsilane, dimethyl- (2 -Methoxyphenyl) silane, dimethyl- (2-fluorophenyl) silane, dimethyl- (2-bromophenyl) silane, dimethyl- (2-chlorophenyl) silane, dimethyl- (3-methoxyphenyl) silane, dimethyl- (2-) Florofe Le) silane, dimethyl - (3-bromophenyl) silane, dimethyl - (2-chlorophenyl) silane, and the like.

  In the method of the present invention, by bringing the above-described silane compound into contact with Au / C using water as a solvent in an inert gas atmosphere, the silane compound is coupled to obtain a siloxane compound having a siloxane bond.

  Specifically, when the silane compound is a phenylsilane represented by the above formula (1), a disiloxane represented by the following formula (2) can be obtained as a siloxane compound.

In formula, R < ¹ >, R < ² >, R < ³ > represents the same group as Formula (1).

  When the silane compound is an alkylsilane having a low bulky substituent, such as triethylsilane, not only disiloxane but also trisiloxane can be obtained as a siloxane compound.

  The inert gas used in the method of the present invention includes argon gas, but nitrogen gas or a mixed gas of argon gas and nitrogen gas may be used.

  Then, the method of the present invention can obtain a siloxane compound with excellent selectivity by contacting the silane compound with Au / C in such an inert gas atmosphere, and depending on the conditions, the selectivity is 90% or more. Siloxane compounds can be obtained. The method of bringing the silane compound into contact with Au / C is not particularly limited, and for example, stirring may be performed under extremely mild conditions such as room temperature of about 20 ° C. under atmospheric pressure. It is needless to say that the reaction conditions, such as temperature increase and pressure increase, may have to be suitably changed in the case where the reaction time is shortened, or when a substrate in which the reaction is difficult to proceed is used.

  The amount of catalyst used in the method of the present invention is appropriately set according to the type of silane compound as the substrate and other reaction conditions, and for example, the amount of gold is 0.5 with respect to the amount of substance of the substrate. It is preferable that it is -50 mol%, and it is more preferable that it is 2-10 mol%. If the amount of gold relative to the substrate is 0.3 mol% or more, the reaction is favorably promoted, and if it is 50 mol% or less, shortening of the reaction time accompanying increase in the amount of catalyst can be expected. In addition, the amount of gold in the carbon support is 1 to 20 wt%, preferably 2 to 15 wt%, and more preferably 5 to 15 wt%. If the amount is less than 10%, the dispersibility of gold in the carrier can be well maintained, the influence of sintering is small, and shortening of the reaction time accompanying the increase of active species can be expected.

  The solvent used in the method of the present invention is water, but if necessary, an organic solvent may be mixed as appropriate. Such an organic solvent is not particularly limited, and examples thereof include alcohols such as methanol and ethanol, acetic acid, tetrahydrofuran and the like, but in order to suppress the formation of by-products, other than alcohols It is preferred to use a solvent of It is needless to say that it is preferable from the viewpoints of cost and safety that the solvent used for the reaction is only water unless it is necessary to use such a mixed solvent. In the method of the present invention, water also acts as an oxidant.

  After the siloxane compound is obtained by the method of the present invention, separation, purification, drying and the like may be appropriately performed.

  The method of the present invention as described above is excellent in both safety and economy, and depending on the conditions, it is possible to produce a siloxane compound from a silane compound with a high yield of over 90%.

  Examples of the present invention will be described below, but it is needless to say that the present invention is not limited to the following examples, and can be widely practiced within the scope of the present invention.

Production example 1
Catalyst Preparation:
In a 10 L beaker, the pure water 2,000 ml and an activated carbon carrier 180 g having an average particle diameter of 20 to 30 μm and a specific surface area of 1,000 to 1,200 m ² / g were stirred. The activated carbon carrier used here was washed by passing through water with 134 ml of pure water per 1 g of the carrier, and the amount of Na contained in the carrier was reduced to 0.06 wt% in terms of Na element. To the slurry of the carbon carrier-water, 1,800 ml of an aqueous solution of chloroauric acid containing 20 g of chloroauric acid (HAuCl ₄ ) in terms of gold was added and further stirred. An aqueous solution containing sodium borohydride (NaBH ₄ ) and sodium hydroxide is added to a slurry consisting of a carbon support-water containing this gold component and stirred to reduce chloroauric acid by stirring, standing, filtration, repeated pure water Water washing was carried out to remove sodium contained to obtain an Au / C catalyst with a 10 wt% gold loading amount used in the example of the present invention.

When crystal size was measured by XRD (X-ray diffraction: X-ray diffraction) about 10 wt% Au / C obtained in this way, crystal size was 31.6 nm. Physical properties are described below along with other data.
・ Gold loading: 10 wt%
・ Gold crystallite size: 31.6 nm
Carrier specific surface area: 1,000 to 1,200 m ² / g
-Elemental equivalent sodium content: 0.06 wt%

Production example 2
Catalyst Preparation:
In the same manner as in Example catalyst 1 except that washing with water as in Example catalyst 1 was not performed on the coconut shell charcoal carrier, an Au / C catalyst was obtained. The sodium content in the carrier was 0.32 wt% in terms of sodium element. Other physical properties were almost the same as those prepared in Production Example 1.

Example 1
Disiloxane synthesis:
(1) Catalyst used <Catalyst 1>
Au / C catalyst prepared in Production Example 1 <Catalyst 2>
Au / C catalyst prepared in Production Example 2 <Catalyst 3>
Gold nanoparticle catalyst purchased from Haltagold (trade name: RR2C)
-Gold loading: 0.89 wt%
・ Gold crystallite size: 8.0 nm
· Specific surface area of support: 731 m ² / g
-Sodium content: less than detection limit <comparative catalyst 1>
[10 wt% Pt / C: NE Chemcat "10% Pt / C K-Type"]
・ Supported amount of platinum: 10 wt%
Carrier specific surface area: 1,000 to 1,200 m ² / g
-Elemental equivalent sodium content: 0.32 wt%
<Comparison catalyst 2>
[5 wt% Pt / C: NE Chemcat "5% Pt / C K-Type"]
-Platinum loading: 5 wt%
Carrier specific surface area: 1,000 to 1,200 m ² / g
-Elemental equivalent sodium content: 0.32 wt%
<Comparison catalyst 3>
[10 wt% Pd / C: NE Chemcat "10% Pt / C K-Type"]
・ Palladium loading amount: 10 wt%
Carrier specific surface area: 1,000 to 1,200 m ² / g
-Elemental equivalent sodium content: 0.32 wt%
<Comparison catalyst 4>
[10 wt% Rh / C: NE Chemcat "10% Pt / C K-Type"]
・ Rhodium load: 10 wt%
Carrier specific surface area: 1,000 to 1,200 m ² / g
-Elemental equivalent sodium content: 0.32 wt%
<Comparison catalyst 5>
[10 wt% Ru / C: NE Chemcat "10% Pt / C K-Type"]
-Ruthenium loading: 10 wt%
Carrier specific surface area: 1,000 to 1,200 m ² / g
-Elemental equivalent sodium content: 0.32 wt%
<Comparison catalyst 6>
[Activated carbon carrier]
Carrier specific surface area: 1,000 to 1,200 m ² / g
-Elemental equivalent Na content: 0.32 wt%

(2) Synthesis reaction The reaction of disiloxane synthesis was performed on the above catalyst under the following conditions. The substrate, temperature, reaction time, and disiloxane yield in the following reaction formula are described in Table 1.
Substrate: 0.25 mmol
・ Catalyst: 10 wt% Au / C (use 5 mol% to substrate)
Solvent: water (3 ml)
Temperature: described in Table 1 Reaction time: described in Table 1 Reaction atmosphere: Argon gas atmosphere Measurement of yield: Calculated by 1 H NMR after isolation Yield of disiloxane compound: Table 1 Ratio of disiloxane to substrate

  It was found that catalysts 1 to 3 were able to produce disiloxanes with high yields comparable to or better than the same amount of platinum catalyst. In addition, it was also found that the yield is higher as the sodium content in the catalyst is particularly low and the gold crystallite size is larger.

Example 2
Catalyst reuse:
After the completion of the synthesis reaction of Example 1, Catalyst 1 was recovered and used again for the same synthesis reaction to evaluate its durability. Evaluation conditions are the same as in Example 1. The results are shown in Table 2.

  From the results in Table 2, it was found that Catalyst 1 exhibited excellent performance even in repeated reuse. From this result, it can be seen that the catalyst 1 has excellent performance also in durability, and it can be said that the value of industrial use is high.

Example 3
Substrate diversity:
A synthesis reaction was carried out using Catalyst 1 in the same manner as in Example 1 except that the substrate and the like were replaced with those described in Table 3 below. The results are also shown in Table 3.

  From the results in Table 3, it was found that Catalyst 1 exhibited excellent performance even on various substrates.

Example 4
Substrate diversity:
The synthesis reaction was carried out using catalyst 1 in the same manner as in Example 1 except that the substrate and reaction time were changed to the following.

  It has been found that when a silane compound having a low bulk substituent such as triethylsilane is a substrate, catalyst 1 can produce not only disiloxane but also trisiloxane.

The method of the present invention can be used to produce siloxane compounds in high yield from silane compounds under safe and low environmental load conditions.

that's all

Claims (7)

  A method for producing a siloxane compound, which comprises bringing a silane compound into contact with a gold catalyst having nano-sized gold particles supported on a carbon support using water as a solvent in an inert gas atmosphere. The silane compound is represented by the following formula (1)

(In formula (1), R ¹ represents a phenyl group which may have a substituent, and R ² and R ³ each independently have hydrogen, an alkyl group having 1 to 3 carbon atoms, or a substituent Represents an optionally substituted phenyl group)
And the siloxane compound is represented by the following formula (2)

(In Formula (2), R ^{1 to} R ³ represent the same group as Formula (1))
The method for producing a siloxane compound according to claim 1, which is a disiloxane represented by   The gold catalyst in which nano-sized gold particles are supported on a carbon support is a gold catalyst in which gold particles having a crystallite size of 10 to 100 nm are supported on a carbon support having an element-equivalent sodium of 0.2 wt% or less. Or the manufacturing method of the siloxane compound of 2. The method for producing a siloxane compound according to any one of claims 1 to 3, wherein the carbon support has a specific surface area of 500 to 2,500 m ² / g and the amount of gold supported is 1 to 20 wt%. A gold catalyst supported gold nano-sized particles to the carbon carrier, a siloxane compound for producing gold catalysts, wherein the crystallite size is 10~100nm gold particles. The gold catalyst for producing a siloxane compound according to claim 5, which is a carbon support having an element conversion sodium of 0.2 wt% or less. Carbon support a specific surface area value 500~2500m ² / g, the supported amount of gold being is 1 to 20 wt% at which claim 5 or 6, wherein the siloxane compound for producing gold catalyst.