Preparation method of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane

Abstract

The invention relates to the technical field of organic synthesis, in particular to a preparation method of 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane. The preparation method comprises the following steps: S1, acetylene and dimethylchlorosilane are subjected to a hydrosilylation reaction under the action of a platinum monatomic catalyst, and a mixture is obtained; s2, pressurizing the mixture to 0.1-0.2 MPa, and condensing through a condenser; s3, the gas phase is recycled, and the liquid phase part is subjected to rectification separation to obtain vinyl dimethyl chlorosilane; s4, carrying out countercurrent reaction on the vinyl dimethyl chlorosilane and water, so as to generate a 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane crude product and hydrochloric acid; and S5, rectifying the crude product to obtain a pure product. The invention provides the preparation method of the 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane, which is high in atom economy and simple and convenient to operate, and meanwhile, the requirements of high selectivity, low environmental load and low cost are met.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and in particular to a method for preparing 1,3-divinyl-1,1,3,3-tetramethyldisiloxane. Background Art

[0002] 1,3-Divinyl-1,1,3,3-tetramethyldisiloxane, referred to as "vinyl dicap", is the core functional monomer of high-performance silicone materials. Its importance stems from the unique divinyl-siloxane synergistic structure. Vinyl dicap can be used as a crosslinking agent and is widely used in addition-type liquid silicone rubber, photocurable silicone resin and electronic packaging adhesive. It achieves efficient curing through platinum-catalyzed hydrosilylation reaction. As a modified intermediate, it can be used to prepare vinyl silicone oil and special silane coupling agents, giving the material hydrophobic, viscosity-increasing and interface-enhancing properties. In the field of advanced materials, it is used to synthesize photonic crystals, low refractive index coatings and high-temperature resistant ceramic precursors. The preparation methods of 1,3-divinyltetramethyldisiloxane currently reported in the literature mainly include the addition method, Grignard reagent method and sodium condensation method. The details are as follows: Addition method: 1,1,3,3-tetramethyldisiloxane and acetylene are used as raw materials, and a hydrosilylation reaction occurs in the presence of a catalyst to produce the product. For example, patent CN102875585A discloses a method using platinum as a catalyst for this reaction. Another method uses ruthenium compounds as catalysts, such as carbonylruthenium chloride and triphenylphosphine ruthenium chloride, in the presence of a co-catalyst amine compound to react 1,1,3,3-tetramethyldisiloxane with acetylene at 0-90°C to produce the target product. However, this method is prone to numerous side reactions in actual application, resulting in low yields of the main product, making it unsuitable for industrial production.

[0003] The Grignard reagent method involves a nucleophilic substitution reaction between 1,3-dichlorotetramethyldisiloxane and a vinyl Grignard reagent under anhydrous and oxygen-free conditions, efficiently introducing two vinyl groups in a single step to produce the target vinyl double-capped product. The key advantages of this method lie in its high reaction selectivity (>95%), excellent yield, and mature and stable process. However, its major disadvantages include its demanding operating conditions (strictly relying on an anhydrous and oxygen-free environment), the production of magnesium salt-containing wastewater, which increases the environmental burden, and the poor stability of the vinyl Grignard reagent, which requires fresh preparation and use, posing safety and cost challenges.

[0004] Sodium condensation method: First, diethoxydimethylsilane and monochloroethylene are used as raw materials, and vinyldimethylethoxysilane is prepared through a sodium condensation reaction. Then, it is hydrolyzed to obtain a vinyl double head with a yield of 77.6%. However, this method has harsh reaction conditions and relatively many steps, and the cost is relatively high in industrial production.

[0005] Existing technologies cannot simultaneously meet the triple requirements of high selectivity, low environmental load and low cost. There is an urgent need to develop alternative processes with high atomic economy and simple operation. Summary of the Invention

[0006] The object of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a method for preparing 1,3-divinyl-1,1,3,3-tetramethyldisiloxane.

[0007] The object of the present invention is to provide a method for preparing 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, comprising the following steps: S1. Acetylene and dimethylchlorosilane undergo a hydrosilylation reaction in the presence of a platinum single atom catalyst to produce a mixture containing vinyldimethylchlorosilane; S2. The mixture containing vinyldimethylsilyl chloride is pressurized to 0.1 to 0.2 MPa and condensed through a condenser; S3. The gas phase is recycled, and the liquid phase is separated by distillation to obtain vinyldimethylchlorosilane; S4. Vinyldimethylsilyl chloride enters the reaction tower from the bottom, and water enters the reaction tower from the top. Vinyldimethylsilyl chloride and water react in a countercurrent manner to produce crude 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and hydrochloric acid. The crude 1,3-divinyl-1,1,3,3-tetramethyldisiloxane is discharged from the top of the reaction tower. S5. The crude product of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane is distilled to obtain pure 1,3-divinyl-1,1,3,3-tetramethyldisiloxane.

[0008] Furthermore, the preparation method of the platinum single atom catalyst in S1 is: a: Dissolve glucose, hydroxylamine hydrochloride, and chloroplatinic acid in an ethanol / water mixture, then add activated carbon and heat with stirring for 4-6 hours; b: drying the above mixture to obtain a solid; c: The obtained solid was heated at 5 °C min under argon atmosphere. -1 The heating rate is from room temperature to 400~600℃, maintained for 1.5~2 hours, then NH3 is introduced, the temperature is raised to 900~1000℃, and maintained for 1.5~2 hours; the final solid obtained is a platinum single atom catalyst.

[0009] Furthermore, in step a, the mass ratio of activated carbon to glucose is 3-5, the mass ratio of activated carbon to hydroxylamine hydrochloride is 8-12, and the mass ratio of activated carbon to chloroplatinic acid is 30-50.

[0010] Furthermore, in step a, the heating temperature is 60-80°C.

[0011] Further, in step S1, the reaction temperature is 80-150 DEG C, the pressure is normal pressure to 0.05 MPa, the space velocity is 4000-8000 h -1 .

[0012] Further, in step S1, the feed molar ratio of acetylene to dimethylchlorosilane is 1.5-3, and the single-pass conversion rate of dimethylchlorosilane is controlled to be 10-40%.

[0013] Further, in step S1, the reaction is carried out in a shell-and-tube reactor, the platinum monatomic catalyst is loaded in the tube side, and the circulating water in the shell side is used to control the reaction temperature and remove the heat generated in the reaction.

[0014] Further, in step S2, the condensation temperature is-10-10 DEG C; and in step S3, the purity of the vinyl dimethylchlorosilane obtained is higher than 98%.

[0015] Further, in step S4, the reaction temperature is room temperature.

[0016] Further, in step S4, the feed mass ratio of the vinyl dimethylchlorosilane to water is 0.2-0.5.

[0017] The present application provides a vinyl double-capped preparation method with high atom economy and simple operation, which meets the requirements of high selectivity, low environmental load and low cost, and proposes a step-by-step catalysis-controllable hydrolysis strategy to solve the above problems: a platinum monatomic catalyst is used to catalyze the silicon-hydrogen addition of acetylene and cheap dimethylchlorosilane to generate vinyl dimethylchlorosilane; then the vinyl dimethylchlorosilane is subjected to hydrolysis condensation to generate the vinyl double-capped 1,3-divinyl-1,1,3,3-tetramethyldisiloxane.

[0018] In the new process provided by the present application, there are two core reaction processes: one is the silicon-hydrogen addition of acetylene and cheap dimethylchlorosilane to generate vinyl dimethylchlorosilane; and the other is the hydrolysis condensation of the vinyl dimethylchlorosilane to generate the vinyl double-capped. Under the addition of the catalyst, the selectivity and yield of the first step reaction are close to 95%, the yield of the second step reaction is close to 100%, and the total yield is more than 93%.

[0019] The silicon-hydrogen addition of acetylene and dimethylchlorosilane is an exothermic reaction, and the generated vinyl dimethylchlorosilane may be subjected to secondary addition with dimethylchlorosilane. In order to prevent the reaction process from flying temperature and the side reaction, the single-pass conversion rate of dimethylchlorosilane is controlled to be 10-40%, and the unreacted raw material is recycled.

[0020] The raw material dimethyl chlorosilane used is a basic intermediate in the silicone industry chain, which is low in price, and the raw materials silicon powder and chloromethane for preparing dimethyl chlorosilane are cheap and easy to obtain. The yield of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane prepared from dimethyl chlorosilane and acetylene is more than 93% under the process.

[0021] The platinum single-atom catalyst prepared in the application introduces and stabilizes specific chemical functional groups (such as nitrogen-containing groups and oxygen-containing groups) on the surface of the activated carbon carrier through a specific precursor (glucose, hydroxylamine hydrochloride) and a heat treatment process (especially ammonia high-temperature treatment). These functional groups act as "anchoring sites" and use a nitrogen-oxygen bifunctional group anchoring strategy. The synergistic effect (bifunctional group) provides a diverse and strong coordination environment for the subsequent stable anchoring of platinum atoms. This solves the problem of easy migration and agglomeration of single-atom catalysts, ensures the formation of a strong chemical bond between platinum atoms and the carrier, and inhibits the migration and agglomeration of metal sites during the reaction process, thereby achieving ultra-high stability. The Pt single-atom catalyst can only perform single-molecule adsorption and has stronger adsorption performance for acetylene, which can inhibit the excessive addition of acetylene, significantly inhibit the adsorption of vinyl dimethyl chlorosilane, and inhibit the secondary addition and self-condensation side reactions of vinyl dimethyl chlorosilane, and the selectivity of the target product vinyl dimethyl chlorosilane can reach about 95%. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The transmission electron micrograph of the catalyst prepared in Example 1 is shown in the figure; Figure 2 The transmission electron micrograph of the catalyst prepared in Example 2 is shown in the figure; Figure 3 The transmission electron micrograph of the catalyst prepared in Example 3 is shown in the figure; Figure 4 The transmission electron micrograph of the catalyst prepared in Example 4 is shown in the figure; Figure 5 The transmission electron micrograph of the catalyst prepared in Comparative Example 1 is shown in the figure; Figure 6 The transmission electron micrograph of the catalyst prepared in Comparative Example 2 is shown in the figure; Figure 7 The transmission electron micrograph of the catalyst prepared in Comparative Example 3 is shown in the figure; Figure 8 The transmission electron micrograph of the catalyst prepared in Comparative Example 4 is shown in the figure; Figure 9 The transmission electron micrograph of the catalyst prepared in Comparative Example 5 is shown in the figure; Figure 10 The single-pass conversion rate of dimethyl chlorosilane and the selectivity of vinyl dimethyl chlorosilane under 200 hours of reaction of Example 8 are shown in the figure. DETAILED DESCRIPTION

[0023] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0024] Example 1 500 mg of glucose, 200 mg of hydroxylamine hydrochloride, and 50 mg of chloroplatinic acid were dissolved in a mixed solution of ethanol / water, and then 2 g of activated carbon was added and heated with stirring for 4-6 h. The mixture was dried in a drying oven at 70 °C for 12 h to obtain a solid. The obtained solid was heated at 5 °C min under an argon atmosphere. -1 The temperature was raised from room temperature to 600 °C and maintained for 2 h, and then NH3 was introduced and the temperature was raised to 950 °C and maintained for 2 h. The solid obtained was the prepared catalyst.

[0025] Figure 1 TEM image of the obtained catalyst shows that Pt is evenly dispersed and no Pt particles are present. Example 1 Within the limited conditions of the present invention, a single-atom catalyst can be prepared.

[0026] Examples 2-4 The methods of Examples 2 to 4 are similar to those of Example 1, except that the material ratios and calcination conditions are different, but all are within the conditions specified in the present invention. The process parameters are shown in Table 1.

[0027] Table 1

[0028] Comparative Examples 1 to 5 Comparative Examples 1 to 5 are similar to the methods of Example 1, but the material ratios and calcination conditions are different, exceeding the conditions specified in the present invention. The process conditions are shown in Table 2.

[0029] Table 2

[0030] Figures 5-9 Transmission electron micrographs of the catalysts prepared in Comparative Examples 1-5; in Comparative Example 1, a large amount of chloroplatinic acid was added, and Pt could not be completely dispersed, resulting in the formation of a large number of Pt particles.

[0031] In Comparative Example 2, the amount of hydroxylamine hydrochloride added was small, and in Comparative Example 3, the amount of glucose added was small, which could not provide sufficient coordination and anchoring sites for Pt. Therefore, a large number of Pt particles were formed.

[0032] In Comparative Example 4, the argon calcination temperature was 350° C., which did not reach the carbonization temperature of glucose, resulting in agglomeration of Pt during the subsequent high-temperature ammonia calcination.

[0033] The temperature of ammonia calcination in Comparative Example 5 is 1100℃, which exceeds the temperature range defined in the present application, resulting in the agglomeration of Pt.

[0034] Synthesis of vinyl dimethylchlorosilane Example 5 Acetylene and dimethylchlorosilane are first introduced into the raw material mixing tank in the gas phase, and the molar ratio of acetylene to dimethylchlorosilane in the mixing tank is controlled to be about 2.5. The reactants are introduced from the raw material mixing tank into the tube reactor, the reaction temperature is 120℃, the pressure is 0.02 MPa (gauge pressure), and the space velocity is 5000 h -1 . After detection by a gas chromatograph, the single-pass conversion rate of dimethylchlorosilane is 24.8%.

[0035] After the reaction, the material is pressurized to 0.1 MPa and cooled to -5℃ by a heat exchanger. The cooled material is introduced into a gas-liquid separation tank, and after gas-liquid separation, the gas phase is unreacted acetylene and dimethylchlorosilane, and the gas phase is reintroduced into the raw material mixing tank. The liquid phase is crude vinyl dimethylchlorosilane, and the liquid phase is detected by a gas chromatograph, with a purity of 92.8% and a catalytic selectivity of 94.8%.

[0036] Example 6 Acetylene and dimethylchlorosilane are first introduced into the raw material mixing tank in the gas phase, and the molar ratio of acetylene to dimethylchlorosilane in the mixing tank is controlled to be about 2. The reactants are introduced from the raw material mixing tank into the tube reactor, the reaction temperature is 90℃, the pressure is 0.03 MPa (gauge pressure), and the space velocity is 6000 h -1 . After detection by a gas chromatograph, the single-pass conversion rate of dimethylchlorosilane is 13.5%.

[0037] After the reaction, the material is pressurized to 0.2 MPa and cooled to -5℃ by a heat exchanger. The cooled material is introduced into a gas-liquid separation tank, and after gas-liquid separation, the gas phase is unreacted acetylene and dimethylchlorosilane, and the gas phase is reintroduced into the raw material mixing tank. The liquid phase is crude vinyl dimethylchlorosilane, and the liquid phase is detected by a gas chromatograph, with a purity of 94.1% and a catalytic selectivity of 95.5%.

[0038] Example 7 Acetylene and dimethylchlorosilane are first introduced into the raw material mixing tank in the gas phase, and the molar ratio of acetylene to dimethylchlorosilane in the mixing tank is controlled to be about 3. The reactants are introduced from the raw material mixing tank into the tube reactor, the reaction temperature is 150℃, the pressure is 0.05 MPa (gauge pressure), and the space velocity is 8000 h -1 . After detection by a gas chromatograph, the single-pass conversion rate of dimethylchlorosilane is 26.1%.

[0039] The reaction product was pressurized to 0.2 MPa and cooled to 0°C through a heat exchanger. The cooled product was introduced into a gas-liquid separation tank, and after gas-liquid separation, the gas phase was unreacted acetylene and dimethylchlorosilane, and the gas phase was re-introduced into the raw material mixing tank. The liquid phase was the crude product of vinyl dimethylchlorosilane, and the liquid phase was detected by gas chromatography, with a purity of 94.2% and a catalytic selectivity of 94.1%.

[0040] Comparative Example 6 Comparative Example 6 was similar to Example 5, except that the catalyst used was a commercial platinum-carbon catalyst (platinum loading of 5%).

[0041] After the reaction, the conversion of dimethylchlorosilane was 19.6% by gas chromatography. After gas-liquid separation, the purity of the liquid phase was 33.9% by gas chromatography, and the catalytic selectivity was 38.4%.

[0042] The commercial platinum-carbon catalyst was not a single-atom catalyst, and did not have the characteristics of the catalyst of the present application to improve selectivity, so the selectivity of the reaction was low and did not have economic value.

[0043] Comparative Example 7 Comparative Example 7 used a Speier catalyst, and the reaction process was a homogeneous reaction.

[0044] Acetylene and dimethylchlorosilane were first introduced into the raw material mixing tank in the gas phase, and the molar ratio of acetylene to dimethylchlorosilane in the mixing tank was controlled to be about 2.5. The reactants were introduced from the raw material mixing tank into a glass reaction kettle containing a dimethylbenzene solution of Speier catalyst with a Pt content of 30 ppm, and the reaction temperature was 120°C and the pressure was 0.02 MPa (gauge pressure). After the reaction, the conversion of dimethylchlorosilane was 27.1% by gas chromatography, and the catalytic selectivity was 57.4%.

[0045] Comparative Example 8 Comparative Example 8 was similar to Comparative Example 7, except that the catalyst used was a Karstedt catalyst. After the reaction, the conversion of dimethylchlorosilane was 22.1% by gas chromatography, and the catalytic selectivity was 61.8%.

[0046] Comparative Example 9 Comparative Example 9 was similar to Example 5, and the space velocity of the reaction process was reduced to 2000 h -1 . The conversion of dimethylchlorosilane was 64.1% by gas chromatography. The purity of the crude product of vinyl dimethylchlorosilane was 76.2%, and the catalytic selectivity was 78.9%.

[0047] Compared with Example 5, the space velocity during the reaction is decreased, and the single-pass conversion of dimethylchlorosilane is increased; a large amount of vinyl dimethylchlorosilane in the system will undergo secondary addition with dimethylchlorosilane, resulting in a significant decrease in catalytic selectivity.

[0048] Example 8 The performance of the catalyst under 200 hours of continuous use was tested under the same operating conditions as in Example 5.

[0049] Figure 10 For the single-pass conversion of dimethylchlorosilane and the selectivity of vinyl dimethylchlorosilane at 200 hours, it can be seen that the conversion and selectivity do not change significantly under 200 hours of continuous use, confirming that the catalyst has excellent stability.

[0050] Synthesis of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane Example 9 The crude vinyl dimethylchlorosilane prepared in Examples 5-7 was respectively fed into a rectification tower, and separated by rectification to obtain vinyl dimethylchlorosilane with a purity of 99.8%. The vinyl dimethylchlorosilane was fed from the lower part of the reaction tower, and water was fed from the upper part of the reaction tower for countercurrent reaction to generate crude 1,3-divinyl-1,1,3,3-tetramethyldisiloxane. The crude 1,3-divinyl-1,1,3,3-tetramethyldisiloxane was subjected to rectification to obtain pure 1,3-divinyl-1,1,3,3-tetramethyldisiloxane with a purity of 99.5%.

[0051] It is calculated that the total yield of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane in Examples 5-7 is 93.5%, 93.9% and 93.1%.

[0052] The above not involved, applicable to the prior art.

[0053] Although some specific embodiments of the present application have been described in detail by way of examples, it should be understood that the above examples are only for illustration and are not intended to limit the scope of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, without deviating from the direction of the present application or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modification, equivalent replacement, improvement, etc. made to the above embodiments according to the technical essence of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, characterized in that: The steps include: S1. Acetylene and dimethylchlorosilane undergo a hydrosilylation reaction in the presence of a platinum single atom catalyst to produce a mixture containing vinyldimethylchlorosilane; S2. The mixture containing vinyldimethylsilyl chloride is pressurized to 0.1 to 0.2 MPa and condensed through a condenser; S3. The gas phase is recycled, and the liquid phase is separated by distillation to obtain vinyldimethylchlorosilane; S4. Vinyldimethylsilyl chloride enters the reaction tower from the bottom, and water enters the reaction tower from the top. Vinyldimethylsilyl chloride and water react in a countercurrent manner to produce crude 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and hydrochloric acid. The crude 1,3-divinyl-1,1,3,3-tetramethyldisiloxane is discharged from the top of the reaction tower. S5. The crude product of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane is distilled to obtain pure 1,3-divinyl-1,1,3,3-tetramethyldisiloxane.

2. The preparation method according to claim 1, wherein The preparation method of the platinum single atom catalyst in S1 is: a: Dissolve glucose, hydroxylamine hydrochloride, and chloroplatinic acid in an ethanol / water mixture, then add activated carbon and heat with stirring for 4-6 hours; b: drying the above mixture to obtain a solid; c: The obtained solid was heated at 5 °C min under argon atmosphere. -1 The heating rate is from room temperature to 400~600℃, maintained for 1.5~2 hours, then NH3 is introduced, the temperature is raised to 900~1000℃, and maintained for 1.5~2 hours; the final solid obtained is a platinum single atom catalyst.

3. The preparation method according to claim 2, wherein In step a, the mass ratio of activated carbon to glucose is 3-5, the mass ratio of activated carbon to hydroxylamine hydrochloride is 8-12, and the mass ratio of activated carbon to chloroplatinic acid is 30-50.

4. The preparation method according to claim 2, wherein In step a, the heating and stirring temperature is 60-80°C.

5. The preparation method according to claim 1, wherein In step S1, the reaction temperature is 80-150°C, the pressure is from normal pressure to 0.05 MPa, and the space velocity is 4000-8000 h -1 .

6. The preparation method according to claim 1, wherein In step S1, the feed molar ratio of acetylene to dimethylchlorosilane is 1.5-3, and the single-pass conversion rate of dimethylchlorosilane is controlled at 10-40%.

7. The preparation method according to claim 1, wherein In step S1, the reaction is carried out in a shell-and-tube reactor, with a platinum single-atom catalyst loaded in the tube side and circulating water in the shell side for controlling the reaction temperature and removing the heat generated by the reaction.

8. The preparation method according to claim 1, wherein In step S2, the condensation temperature is -10~10°C; and in step S3, vinyldimethylchlorosilane with a purity higher than 98% is obtained.

9. The preparation method according to claim 1, wherein In step S4, the reaction temperature is room temperature.

10. The preparation method according to claim 1, wherein In step S4, the feed mass ratio of vinyldimethylsilyl chloride to water is 0.2-0.5.

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