CN111138667B - A kind of liquid phase flow synthesis device of polycarbosilane and synthesis method thereof - Google Patents
A kind of liquid phase flow synthesis device of polycarbosilane and synthesis method thereof Download PDFInfo
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Abstract
本发明公开一种聚碳硅烷的液相流动合成装置及其合成方法，该方法不需要使用现有方法中采用的反应釜体，而是采用本发明提供的液相流动合成装置，利用液相在该装置的细小管道中高效的传热传质效果并借助聚二苯基硼硅氧烷的催化作用，使反应液和催化液在流动过程中充分混合并可在较低温度下实现充分反应，从而降低合成温度，提高合成的均匀性和转化产率，降低聚碳硅烷的成本。本发明提供的合成方法可克服现有技术中使用反应釜带来的系列问题，且能成功合成得到性能优异的聚碳硅烷，在聚碳硅烷的批量工程化上有很好的应用前景。
The invention discloses a liquid-phase flow synthesis device for polycarbosilane and a synthesis method thereof. The method does not need to use the reaction kettle body used in the existing method, but adopts the liquid-phase flow synthesis device provided by the invention, and utilizes the liquid phase flow synthesis device. The efficient heat and mass transfer effect in the small pipes of the device and the catalysis of polydiphenylborosiloxane make the reaction liquid and the catalytic liquid fully mixed during the flow process and can fully react at a lower temperature , thereby reducing the synthesis temperature, improving the synthesis uniformity and conversion yield, and reducing the cost of polycarbosilane. The synthesis method provided by the invention can overcome a series of problems caused by using a reaction kettle in the prior art, and can successfully synthesize polycarbosilane with excellent performance, which has a good application prospect in the batch engineering of polycarbosilane.
Description
Technical Field
The invention relates to the technical field of polymer synthesis, in particular to a liquid phase flow synthesis device and a synthesis method of polycarbosilane.
Background
The SiC ceramic is a covalent bond compound bonded by Si-C bonds, has a diamond structure, has a distance between adjacent atoms of 0.186nm, and has a Si-C bond energy of 347 KJ/mol. The special crystal structure of the SiC ceramic determines that the SiC ceramic has excellent characteristics of high strength, high temperature resistance, corrosion resistance, oxidation resistance and the like when being used as a high-temperature structural material, and the SiC ceramic is widely applied to the fields of spaceflight, automobiles, petrifaction and the like; when used as a functional material, SiC has the advantages of high breakdown electric field, wide energy band structure, high thermal conductivity and the like, and has good application prospect in the aspects of electroluminescent devices, wave-absorbing materials, gas sensors and the like.
The precursor conversion method is a commonly used method for preparing SiC ceramic, and comprises the steps of firstly synthesizing an organic polymer containing silicon and carbon elements, and preparing the corresponding SiC ceramic material by utilizing the good forming performance of the polymer through forming and pyrolysis. The precursor conversion method has the advantage of lower preparation temperature; meanwhile, the method can prepare low-dimensional ceramic materials which are difficult to obtain by the traditional method; in addition, the method can carry out molecular design to obtain precursor polymers with different element compositions, and obtain multi-element multi-phase ceramics or ceramic alloy through thermal decomposition and conversion. At present, a precursor conversion method has become a mainstream preparation method of ceramic fibers and ceramic matrix composites.
Polycarbosilane is the most successful precursor for preparing SiC ceramic by a precursor conversion method, is also a raw material capable of simultaneously realizing the preparation of ceramic powder, ceramic fiber and a ceramic matrix composite precursor, and has already realized industrialization at present, and the annual capacity exceeds hundreds of tons. The polycarbosilane is prepared by two methods, one method is a high-pressure method in the teaching of Yajima, namely, Polydimethylsilane (PDMS) is used as a raw material, the temperature is kept in an autoclave at 450-500 ℃ for a period of time, so that the PDMS is cracked and rearranged, and the polycarbosilane is obtained through further polycondensation. However, the reaction pressure of the method exceeds 10MPa, the requirement on equipment is extremely high, the danger in industrial production is large, the cost of the high-pressure polycarbosilane is high, and the application of the high-pressure polycarbosilane is limited. In the other method, PDMS is used as a raw material, poly diphenyl borosiloxane is used as a catalyst, and the PDMS is subjected to cracking, rearrangement and polycondensation at the temperature of 300-400 ℃ under normal pressure to prepare the polycarbosilane. Compared with a high-pressure method, the method has the advantages of low requirement on equipment, easiness in industrial production and relatively low cost of the prepared polycarbosilane.
However, in the process of cracking PDMS by using either the high pressure method or the normal pressure catalytic method, due to poor heat transfer property of PDMS powder, large temperature gradient fields exist at different positions in the reaction vessel body, the cracking of PDMS gradually diffuses from the vessel wall to the center, and different environmental and thermal experiences occur at different positions in the reaction vessel, resulting in the generation of cracking products in different states. In addition, the reaction kettle can only heat the outer wall, the heat is diffused from outside to inside, the reaction kettle has a temperature gradient from the outer wall to the center, and the rearrangement polycondensation reaction is not uniform, so that the molecular weight distribution of the prepared polycarbosilane is widened; in addition, in order to ensure that the raw materials in the central area in the kettle can be fully reacted, the temperature of the kettle wall is often higher, the coking phenomenon of the kettle wall is serious, and the synthesis yield is low. Especially in the industrial production, the larger the reaction kettle is, the more uneven the reaction is, the more serious the coking of the kettle wall is, and the lower the yield (generally not more than 40%), so that the cost of the polycarbosilane is extremely high, and more than 3000 yuan per kilogram, and great obstacle is brought to the application of engineering.
Disclosure of Invention
The invention provides a liquid phase flow synthesis device and a synthesis method of polycarbosilane, which are used for overcoming the defects of widened molecular weight distribution, coking kettle wall, low yield, high cost and the like of polycarbosilane caused by poor heat transfer property of PDMS powder and poor heat and mass transfer property of a large reaction kettle in the prior art.
In order to achieve the purpose, the invention provides a liquid phase flow synthesis device of polycarbosilane, which comprises an input pipeline 2, a mixing pipeline 3, a reaction pipeline 4, an output pipeline 5 and a receiving kettle 6 which are connected in sequence;
the input pipeline 2 comprises at least two input ports for inputting different reaction liquids into the mixing pipeline 3.
In order to achieve the above object, the present invention further provides a liquid phase flow synthesis method of polycarbosilane, which adopts the liquid phase flow synthesis device of polycarbosilane as described above to synthesize polycarbosilane, and comprises the following steps:
s1: placing Polydimethylsiloxane (PDMS) alkane in an inert atmosphere, heating from room temperature to 350-450 ℃ at the speed of 1-10 ℃/min, and preserving heat at 350-450 ℃ for 0.5-10 h to obtain a reaction solution;
s2: dissolving poly diphenyl borosiloxane in an organic solvent to obtain a catalytic solution;
s3: introducing inert atmosphere into the liquid phase flow synthesis device to clean pipelines, then injecting reaction liquid and catalytic liquid into an input pipeline 2 from different input ports respectively, mixing in a mixing pipeline 3, carrying out heating reaction in a reaction pipeline 4, and finally flowing into a receiving kettle 6 through an output pipeline 5 to obtain a crude product;
s4: and distilling the crude product at 150-250 ℃ under reduced pressure to obtain polycarbosilane.
Compared with the prior art, the invention has the beneficial effects that:
the liquid phase flow synthesis method of polycarbosilane provided by the invention comprises the steps of firstly cracking PDMS to obtain reaction liquid, and preparing poly diphenyl borosiloxane into catalytic liquid; then, respectively injecting reaction liquid and catalytic liquid into an input pipeline from different input ports, mixing through a mixing pipeline 3, heating and reacting through a reaction pipeline 4, and finally flowing into a receiving kettle 6 through an output pipeline 5 to obtain a crude product; and finally, distilling the crude product under reduced pressure to obtain polycarbosilane. Compared with the existing industrial synthesis method of polycarbosilane, the synthesis method provided by the invention does not need to use a reaction kettle body adopted in the existing method, but adopts the liquid phase flow synthesis device provided by the invention, utilizes the high-efficiency heat and mass transfer effect of a liquid phase in a fine pipeline and the catalytic action of poly diphenyl borosiloxane, so that the reaction liquid and the catalytic liquid are fully mixed in the flow process and can fully react at a lower temperature, thereby reducing the synthesis temperature, improving the synthesis uniformity and the conversion yield and reducing the cost of polycarbosilane. The synthesis method provided by the invention can overcome series problems caused by using a reaction kettle in the prior art, can successfully synthesize polycarbosilane with excellent performance, and has good application prospect in the batch engineering of polycarbosilane.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a structural diagram of a liquid phase flow synthesis apparatus for polycarbosilane according to the present invention;
FIG. 2 is an infrared spectrum of polycarbosilane synthesized in example 1;
FIG. 3 is a photograph of polycarbosilane synthesized in example 1.
The reference numbers illustrate: 1: taking a liquid device; 2: an input pipeline; 3: a mixing line; 4: a reaction pipeline; 5: an output pipeline; 6: and (4) receiving the kettle.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.
The drugs/reagents used are all commercially available without specific mention.
The invention provides a liquid phase flow synthesis device of polycarbosilane, which comprises an input pipeline 2, a mixing pipeline 3, a reaction pipeline 4, an output pipeline 5 and a receiving kettle 6 which are connected in sequence as shown in figure 1;
the input pipeline 2 comprises at least two input ports for inputting different reaction liquids into the mixing pipeline 3.
Different reaction liquids can be fed into the feed line 2 from different inlets via the liquid take-off 1. The liquid taking device 1 can be a syringe pump, a liquid transferring gun, a syringe and the like.
Preferably, the input pipeline 2, the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 are made of stainless steel, the inner diameter of each pipeline is 2-20 mm, and the wall thickness of each pipeline is 1-5 mm. The pipeline is made of stainless steel to prevent corrosion of chemical reagents, prolong the service life and avoid polluting reaction liquid due to corrosion. When the inner diameter of the pipeline is less than 2mm, the viscosity of the liquid phase at the later stage of synthesis is increased, and the pipeline is easy to block; when the inner diameter of the pipeline is more than 20mm, the reaction liquid and the catalytic liquid are mixed unevenly under the flowing state in the pipeline, and the uniformity and the yield of the synthesized polycarbosilane are reduced. When the wall thickness of the pipeline is less than 1mm, the pressure resistance is not enough, and the pipeline is easy to damage and leak; when the wall thickness of the pipeline is higher than 5mm, the thermal expansion difference between the heating pipeline and the normal temperature pipeline is too large, and the pipeline leakage is easily caused.
Preferably, the length of the mixing pipeline 3 is more than or equal to 10cm, and the length of the reaction pipeline 4 is more than or equal to 250 cm. When the length of the mixing pipeline 3 is less than 10cm, the reaction liquid and the catalytic liquid are mixed unevenly in a flowing state in the pipeline, and the uniformity and the yield of the synthesized polycarbosilane are reduced. The length of the reaction line 4 is less than 250cm, which may result in insufficient synthesis reaction, failure to obtain polycarbosilane, or decrease in yield of polycarbosilane.
Preferably, the reaction channel 4 is helical. The reaction line 4 may be a straight line or a bent line, but in industrial production, a spiral line is preferable to reduce the floor space of the apparatus when the required reaction line 4 is long because of a large production amount.
The invention also provides a liquid phase flow synthesis method of polycarbosilane, which adopts the liquid phase flow synthesis device of polycarbosilane to synthesize the polycarbosilane and comprises the following steps:
s1: placing polydimethylsiloxane in an inert atmosphere, heating from room temperature to 350-450 ℃ at the speed of 1-10 ℃/min, and preserving heat at 350-450 ℃ for 0.5-10 h to obtain a reaction solution;
s1 is the cracking of polydimethyl silane in a cracking kettle. The inert atmosphere may be a nitrogen atmosphere, an argon atmosphere, or the like.
S2: dissolving poly diphenyl borosiloxane in an organic solvent to obtain a catalytic solution;
polydiphenyl borosiloxane is used as a catalyst to facilitate the synthesis reaction.
Preferably, the polydiphenyl borosiloxane has the formula
n is 2 to 30. When n is less than 2, the molecular weight of the poly diphenyl borosiloxane is too low, and the catalytic synthesis effect is not obvious; when n is more than 30, the molecular weight of the poly diphenyl borosiloxane is too large, the viscosity is too high after the poly diphenyl borosiloxane is prepared into a solution, the poly diphenyl borosiloxane cannot flow in a pipeline, and the polycarbosilane cannot be prepared by the method provided by the invention.
Preferably, the organic solvent is toluene or xylene; the concentration of poly diphenyl boron siloxane in the catalytic liquid is 100-3000 g/L. Toluene or xylene is a common organic solvent and has good dissolving effect on poly diphenyl borosiloxane. The concentration of the poly diphenyl borosilicate solution is lower than 100g/L, the catalytic effect is not obvious, and the synthesis yield of polycarbosilane is low; the concentration of the poly diphenyl borosilicate siloxane solution is higher than 3000g/L, the concentration of the solution is too high, a pipeline is easily blocked in the synthesis process, and polycarbosilane cannot be prepared.
S3: introducing inert atmosphere into the liquid phase flow synthesis device to clean pipelines, then injecting reaction liquid and catalytic liquid into an input pipeline 2 from different input ports respectively, mixing in a mixing pipeline 3, carrying out heating reaction in a reaction pipeline 4, and finally flowing into a receiving kettle 6 through an output pipeline 5 to obtain a crude product;
the inert atmosphere may be a nitrogen atmosphere, an argon atmosphere, or the like.
Preferably, the proportion relationship between the added amounts of the reaction liquid and the catalytic liquid is as follows: the mass ratio of the reaction liquid to the polydiphenyl borosiloxane in the catalytic liquid is 100 (2-20). The mass ratio of the reaction liquid to the polydiphenyl borosiloxane in the catalytic liquid is lower than 100: 2, the catalytic effect is not obvious, and polycarbosilane cannot be prepared; higher than 100: 20, the reaction is too rapid, the molecular weight is increased too fast, and pipelines are easy to block.
Preferably, the flow speed of the mixed solution of the reaction solution and the catalytic solution in the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 is more than or equal to 1cm/s, if the flow speed is lower than 1cm/s, the liquid phase viscosity at the later stage of synthesis is increased, the pipeline is easy to block, and continuous synthesis cannot be performed; the heating temperature of the reaction pipeline 4 is 200-300 ℃, the temperature is lower than 200 ℃, the rearrangement polycondensation reaction cannot occur, and polycarbosilane cannot be obtained; the temperature is higher than 300 ℃, the reaction is too rapid, the molecular weight is increased too fast, and pipelines are easy to block. The flow rate is controlled primarily by the pressure of the syringe pump.
Preferably, the pipeline cleaning is as follows: and cleaning for 5-60 min under the conditions that the pressure of the inert atmosphere is 0.15-1.00 MPa and the flow is 50-500 mL/min, so as to ensure that the pipeline is cleaned.
S4: and distilling the crude product at 150-250 ℃ under reduced pressure to obtain polycarbosilane.
Example 1
The embodiment provides a liquid phase flow synthesis device of polycarbosilane, which comprises an input pipeline 2, a mixing pipeline 3, a reaction pipeline 4, an output pipeline 5 and a receiving kettle 6 which are connected in sequence;
the input pipeline 2 comprises two input ports for inputting different reaction liquids into the mixing pipeline 3.
The reaction pipeline 4 is in a spiral shape so as to reduce the floor area of the device.
The length of the mixing pipeline 3 is 20cm, and the length of the reaction pipeline 4 is 300 cm.
The embodiment also provides a liquid phase flow synthesis method of polycarbosilane, which adopts the above liquid phase flow synthesis device to synthesize polycarbosilane, and comprises the following steps:
s1: placing 1320g of polydimethyl siloxane (PDMS) alkane in a cracking kettle, vacuumizing to replace nitrogen, heating from room temperature to 450 ℃ at the speed of 1 ℃/min, and preserving heat at 450 ℃ for 0.5h to obtain 1000g of reaction liquid;
s2: 100g of polydiphenyl borosiloxane (formula:)
) Dissolving in 1000mL of dimethylbenzene to obtain a catalytic solution;
s3: introducing nitrogen with the pressure of 0.5MPa and the flow rate of 500mL/min into the liquid phase flow synthesis device, cleaning for 5min, injecting all reaction liquid obtained from S1 and all catalytic liquid obtained from S2 into an input pipeline 2 from different input ports respectively through a liquid transfer gun, mixing through a mixing pipeline 3, heating and reacting through a reaction pipeline 4, and finally flowing into a receiving kettle 6 through an output pipeline 5 to obtain a crude product; the flow speed of the mixed solution of the reaction liquid and the catalytic liquid in the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 is 5 cm/s; the heating temperature of the reaction pipeline 4 is 300 ℃;
s4: the crude product was distilled at 250 ℃ under reduced pressure to give 772g of polycarbosilane, as shown in FIG. 3.
The polycarbosilane synthesized in this example was characterized by infrared. The structure of polycarbosilane is measured by a KBr tablet sample preparation method and a Nicolet-360 type infrared spectrometer of the United states of America thermoelectric company, and the scanning range is 400-4000 cm-1Resolution of 4cm-1. The IR spectra are shown in FIG. 2, from which it can be seen that 2950 and 2900cm-1The left and right are C-H stretching vibration peak, 2100cm-1At the position of the vibration peak is Si-H stretching vibration peak, 1400 cm and 1350cm-1Are each Si-CH3C-H deformation vibration and Si-CH in structure2CH in the-Si structure2Out-of-plane rocking vibration, 1250cm-1Is of Si-CH3In the structure of CH3Deformation vibration, 1020cm-1Is of Si-CH2Stretching vibration of Si-C-Si in-Si structure, 820cm-1Here, Si-C stretching vibration confirmed that polycarbosilane was synthesized.
The synthesis yield (the mass/(cracked liquid product A + poly diphenyl borosiloxane) x 100%) of the polycarbosilane in the embodiment is 70.2%, which is greatly improved compared with the yield (40-50%) of the polycarbosilane synthesized by the current engineering.
The molecular weight and the dispersion coefficient of the polycarbosilane are measured by using a Wyatt DAWN HELEOS-II light scattering instrument and a high-efficiency gel permeation chromatograph together and using tetrahydrofuran as a solvent, a chromatographic column is an S-Styragel packed column, and the leaching rate is l mL/min. The number average molecular weight is 1020, the molecular weight dispersion coefficient is 1.66, and compared with the molecular weight dispersion coefficient (2-4) of the existing engineering synthetic polycarbosilane, the molecular weight distribution is more uniform, and the method has more advantages in the aspect of fiber forming.
Example 2
Compared with the device in the embodiment 1, the inner diameters of the input pipeline 2, the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 are all 20mm, and the wall thickness of the pipelines is 1 mm. The length of the mixing pipeline 3 is 50cm, and the length of the reaction pipeline 4 is 600 cm. The other structure is the same as that of embodiment 1.
The embodiment also provides a liquid phase flow synthesis method of polycarbosilane, which adopts the above liquid phase flow synthesis device to synthesize polycarbosilane, and comprises the following steps:
s1: putting 1410g of polydimethyl siloxane (PDMS) alkane into a cracking kettle, vacuumizing to replace nitrogen, heating from room temperature to 380 ℃ at the speed of 10 ℃/min, and preserving the heat at 380 ℃ for 10 hours to obtain 1000g of reaction liquid;
s2: 20g of polydiphenyl borosiloxane (formula:)
) Dissolving in 60mL of toluene to obtain a catalytic solution;
s3: introducing nitrogen with the pressure of 0.15MPa and the flow rate of 50mL/min into the liquid phase flow synthesis device, cleaning for 60min, injecting all reaction liquid obtained from S1 and all catalytic liquid obtained from S2 into an input pipeline 2 from different input ports respectively through injection pumps, mixing through a mixing pipeline 3, heating and reacting through a reaction pipeline 4, and finally flowing into a receiving kettle 6 through an output pipeline 5 to obtain a crude product; the flow speed of the mixed solution of the reaction liquid and the catalytic liquid in the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 is 1 cm/s; the heating temperature of the reaction pipeline 4 is 300 ℃;
s4: the crude product was distilled at 150 ℃ under reduced pressure to give 604g of polycarbosilane.
The synthetic yield of the polycarbosilane synthesized by the embodiment is 59.2%; the number average molecular weight of the synthesized polycarbosilane is 763, and the molecular weight dispersion coefficient is 1.47.
Example 3
This example provides a liquid phase flow synthesis apparatus for polycarbosilane, and the length of the reaction pipeline 4 is 6000cm compared with the apparatus of example 2. The other structure is the same as that of embodiment 2.
The embodiment also provides a liquid phase flow synthesis method of polycarbosilane, which adopts the above liquid phase flow synthesis device to synthesize polycarbosilane, and comprises the following steps:
s1: the same as step S1 of embodiment 2;
s2: the same as step S2 of embodiment 2;
s3: the same as step S3 of embodiment 2;
s4: the crude product was distilled at 150 ℃ under reduced pressure to give 726g of polycarbosilane.
The synthetic yield of the polycarbosilane synthesized by the embodiment is 71.2%; the number average molecular weight of the synthesized polycarbosilane was 906, and the molecular weight dispersion coefficient was 1.55.
Comparing example 2 with example 3, it was found that: under the same conditions, the length of the reaction pipeline 4 is increased, and the synthesis yield can be effectively improved.
Example 4
Compared with the device in the embodiment 1, the inner diameters of the input pipeline 2, the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 are all 10mm, and the wall thickness of the pipelines is 2 mm. The length of the mixing pipeline 3 is 50cm, and the length of the reaction pipeline 4 is 3000 cm. The other structure is the same as that of embodiment 1.
The embodiment also provides a liquid phase flow synthesis method of polycarbosilane, which adopts the above liquid phase flow synthesis device to synthesize polycarbosilane, and comprises the following steps:
s1: placing 1270g of Polydimethylsiloxane (PDMS) alkane in a cracking kettle, vacuumizing to replace nitrogen, heating from room temperature to 400 ℃ at the speed of 2 ℃/min, and preserving heat at 400 ℃ for 3h to obtain 1000g of reaction liquid;
S2：200g of polydiphenyl borosiloxane (formula:)
) Dissolving in 200mL of dimethylbenzene to obtain a catalytic solution;
s3: introducing nitrogen with the pressure of 0.2MPa and the flow rate of 100mL/min into the liquid phase flow synthesis device, cleaning for 10min, injecting all reaction liquid obtained from S1 and all catalytic liquid obtained from S2 into an input pipeline 2 from different input ports respectively through a liquid transfer gun, mixing through a mixing pipeline 3, heating and reacting through a reaction pipeline 4, and finally flowing into a receiving kettle 6 through an output pipeline 5 to obtain a crude product; the flow speed of the mixed solution of the reaction liquid and the catalytic liquid in the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 is 5 cm/s; the heating temperature of the reaction pipeline 4 is 200 ℃;
s4: the crude product was distilled at 170 ℃ under reduced pressure to give 842g of polycarbosilane.
The synthetic yield of the polycarbosilane synthesized by the embodiment is 70.2%; the number average molecular weight of the synthesized polycarbosilane was 716, and the molecular weight dispersion coefficient was 1.42.
Example 5
The embodiment provides a liquid phase flow synthesis method of polycarbosilane, which adopts the liquid phase flow synthesis device provided in embodiment 4 to synthesize polycarbosilane, and comprises the following steps:
s1: the same as step S1 of embodiment 4;
s2: the same as step S2 of embodiment 4;
s3: compared with step S3 of example 4, the heating temperature of the reaction line 4 is 250 ℃, and the other processes are the same as those of example 4;
s4: the crude product was distilled at 170 ℃ under reduced pressure to give 901g of polycarbosilane.
The synthetic yield of the polycarbosilane synthesized by the embodiment is 75.1%; the resulting polycarbosilane had a number average molecular weight of 938 and a molecular weight dispersion coefficient of 1.69.
Comparing example 4 with example 5, it was found that: under the same condition, the heating temperature of the reaction pipeline 4 is increased, and the synthesis yield can be effectively improved.
Example 6
Compared with the device in the embodiment 1, the inner diameters of the input pipeline 2, the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 are all 10mm, and the wall thickness of the pipelines is 2 mm. The length of the mixing pipeline 3 is 100cm, and the length of the reaction pipeline 4 is 6000 cm. The other structure is the same as that of embodiment 1.
The embodiment also provides a liquid phase flow synthesis method of polycarbosilane, which adopts the above liquid phase flow synthesis device to synthesize polycarbosilane, and comprises the following steps:
s1: placing 1270g of Polydimethylsiloxane (PDMS) alkane in a cracking kettle, vacuumizing to replace nitrogen, heating from room temperature to 400 ℃ at the speed of 2 ℃/min, and preserving heat at 400 ℃ for 3h to obtain 1000g of reaction liquid;
s2: 100g of polydiphenyl borosiloxane (formula:)
) Dissolving in 200mL of dimethylbenzene to obtain a catalytic solution;
s3: introducing nitrogen with the pressure of 0.4MPa and the flow rate of 100mL/min into the liquid phase flow synthesis device, cleaning for 30min, injecting all reaction liquid obtained from S1 and all catalytic liquid obtained from S2 into an input pipeline 2 from different input ports respectively through injection pumps, mixing through a mixing pipeline 3, heating and reacting through a reaction pipeline 4, and finally flowing into a receiving kettle 6 through an output pipeline 5 to obtain a crude product; the flow speed of the mixed solution of the reaction liquid and the catalytic liquid in the mixing pipeline 3, the reaction pipeline 4 and the output pipeline 5 is 3 cm/s; the heating temperature of the reaction pipeline 4 is 280 ℃;
s4: the crude product was distilled at 220 ℃ under reduced pressure to give 808g of polycarbosilane.
The synthetic yield of the polycarbosilane synthesized by the embodiment is 73.5%; the resulting polycarbosilane had a number average molecular weight of 1139 and a molecular weight dispersion coefficient of 1.74.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
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| CN111138859A (en) * | 2020-01-09 | 2020-05-12 | 合肥工业大学 | Three-dimensional structure nano composite intelligent sponge, preparation method and application |
| CN113388920B (en) * | 2021-05-25 | 2022-11-25 | 湖南泽睿新材料有限公司 | Preparation method of silicon carbide fiber containing heterogeneous elements |
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