CN117247532A - Synthesis process of polypropylene carbonate - Google Patents

Synthesis process of polypropylene carbonate Download PDF

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Publication number
CN117247532A
CN117247532A CN202311346291.5A CN202311346291A CN117247532A CN 117247532 A CN117247532 A CN 117247532A CN 202311346291 A CN202311346291 A CN 202311346291A CN 117247532 A CN117247532 A CN 117247532A
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polypropylene carbonate
catalyst
reaction
carbon dioxide
molecular sieve
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何泽宇
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Yuanjia Biotechnology Guangdong Co ltd
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Yuanjia Biotechnology Guangdong Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G64/00—Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule
    • C08G64/20—General preparatory processes
    • C08G64/32—General preparatory processes using carbon dioxide
    • C08G64/34—General preparatory processes using carbon dioxide and cyclic ethers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G64/00—Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule
    • C08G64/02—Aliphatic polycarbonates
    • C08G64/0208—Aliphatic polycarbonates saturated
    • C08G64/0216—Aliphatic polycarbonates saturated containing a chain-terminating or -crosslinking agent

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Polyesters Or Polycarbonates (AREA)

Abstract

The application discloses a synthesis process of polypropylene carbonate, wherein carbon dioxide participating in reaction adopted in the synthesis process of the polypropylene carbonate is supercritical carbon dioxide. The supercritical carbon dioxide has the property of liquid and stable chemical property, can serve as a part of a reaction solvent to dilute the polypropylene carbonate product, so that the problem of high viscosity of the polypropylene carbonate in the later stage of the preparation process is solved, the heat transfer rate is high, the heat generated in the preparation process of the polypropylene carbonate can be timely dissipated, and the reaction probability of the carbon dioxide and propylene oxide can be remarkably increased. And the modified catalyst added in the synthesis process is a molecular sieve supported metal carboxylate catalyst, so that the catalytic efficiency of the catalyst can be increased, and meanwhile, the catalyst can be adapted to the processing conditions of high temperature and high pressure in the application, and the catalytic efficiency is not easy to deactivate, so that the catalytic efficiency is reduced.

Description

Synthesis process of polypropylene carbonate
Technical Field
The application relates to the field of processing of polypropylene carbonate, in particular to a synthesis process of polypropylene carbonate.
Background
The polypropylene carbonate is an alternating copolymer of carbon dioxide and propylene oxide, has good gas barrier property, transparency and biodegradability, can be widely applied to packaging materials, gas barrier materials and biomedical materials, can realize full utilization of carbon dioxide, remarkably relieves greenhouse effect caused by carbon dioxide emission, and opens up a new field of fixing the carbon dioxide into biodegradable polymers.
At present, the industrialized production of the polypropylene carbonate generally adopts a bulk polymerization process, but in the later stage, the polymer is continuously generated in the process of bulk polymerization, the system viscosity is high, the heat dissipation is difficult, meanwhile, the polypropylene carbonate is a heat sensitive material, the system viscosity cannot be reduced in a mode of increasing the temperature, and finally, the conversion rate of propylene oxide in the industrial production process is low, and the production cost is increased.
Disclosure of Invention
In order to solve the problems of high viscosity, low propylene oxide conversion rate, high cost and the like in the industrial production process of the polypropylene carbonate, the application provides a synthesis process of the polypropylene carbonate.
In a first aspect, the present application provides a process for the synthesis of polypropylene carbonate, comprising the steps of:
s1, dehydrating the reaction solvent 1;
s2, mixing the reaction solvent 2 with the modified catalyst in the carbon dioxide atmosphere to obtain a catalyst mixed solution;
s3, carrying out pressurization treatment on carbon dioxide, blending with a mixed solution of a reaction solvent 1 and a catalyst, continuously adding propylene oxide, and then stirring and reacting for 2-3 hours;
s4, adding a terminator after the reaction is finished, stirring, mixing and cooling, extruding and granulating the obtained polymer to obtain the polypropylene carbonate;
s5, condensing waste liquid and gas generated in the reaction process, and then recycling;
the carbon dioxide which participates in the reaction in the step S3 is supercritical carbon dioxide.
Preferably, the reaction solvent 1 comprises one or a combination of more of dichloromethane, ethyl acetate, acetone and dichloroethylene; the reaction solvent 2 comprises one or a combination of more of dichloromethane and acetone.
Preferably, the addition amount of the modified catalyst is 1 to 3% of the mass of the propylene oxide.
Preferably, the reaction pressure of the stirring reaction in the step S3 is 2.5-10 MPa; the reaction temperature of the stirring reaction in the step S3 is 50-110 ℃.
More preferably, the reaction pressure of the stirring reaction in the step S3 is 3.5-9 MPa; the reaction temperature of the stirring reaction in the step S3 is 60-90 ℃.
Preferably, in the step S3, the mass ratio of carbon dioxide to propylene oxide is (4.5-45): 8.
preferably, the mass ratio of the reaction solvent 1 to propylene oxide is (0.5 to 4): 1.
preferably, the temperature of the extrusion granulation process in the step S4 is 95-185 ℃ and the vacuum degree is 3-120 kPa.
More preferably, the temperature of the extrusion granulation process in the step S4 is 110 to 165 ℃ and the vacuum degree is 10 to 80kPa.
Preferably, the terminator is ethylboronic acid; the addition amount of the terminator is 0.1-0.2% of the addition amount of the propylene oxide.
The carbon dioxide adopted in the process of preparing the polypropylene carbonate by the reaction of the carbon dioxide and the propylene oxide is supercritical carbon dioxide, the acting force between supercritical carbon dioxide fluid is between gas and liquid, the property between gas and liquid is realized, the heat transfer rate and the mass transfer rate are high, by adopting the technical scheme, the carbon dioxide raw material for preparing the polypropylene carbonate is replaced by the supercritical carbon dioxide, on the one hand, the supercritical carbon dioxide has the property of liquid and has stable chemical property and can serve as a part of a reaction solvent, so that the polypropylene carbonate product is diluted, the problem of high viscosity of the polypropylene carbonate in the later stage of the preparation process is solved, the heat generated in the preparation process of the polypropylene carbonate can be timely dissipated instead of accumulating in the polypropylene carbonate, and the mass accumulation of the heat can lead to the degradation of the heat-sensitive polypropylene carbonate, so that the conversion rate of the propylene oxide is reduced; on the other hand, when the supercritical carbon dioxide is mixed with the propylene oxide in a liquid state, the reaction probability of the carbon dioxide and the propylene oxide can be obviously increased, and under the action of the modified catalyst, the reaction of the carbon dioxide and the propylene oxide can be accelerated and is full.
In the process of blending the modified catalyst and the reaction solvent 2, the air in the container can influence the polymerization reaction process, so that carbon dioxide is needed to replace the air, the modified catalyst and the reaction solvent 2 are blended in the carbon dioxide atmosphere, the next polymerization reaction is not influenced, and the modified catalyst is firstly blended with the reaction solvent 2, so that the dispersibility of the modified catalyst in the polymerization reaction process can be improved, the catalytic efficiency of the modified catalyst is improved, and the conversion rate of propylene oxide is improved; the continuous addition of the propylene oxide also enables the polymerization reaction of the polypropylene carbonate to be continuously carried out, improves the self-polymerization reaction caused by the over high concentration of the propylene oxide in the system, reduces the generation of byproducts and improves the conversion rate of the propylene oxide, and simultaneously, the heat generated by the reaction is not increased abruptly, so that the heat removal of the reaction can be quickened.
Preferably, the modified catalyst is a molecular sieve supported metal carboxylate catalyst.
Preferably, the molecular sieve supported metal carboxylate catalyst comprises the following raw materials in mass ratio (1.4-2): (1.8-2.2): 1, organic ligands and modified molecular sieves.
Preferably, the metal salt comprises one or a combination of several of zinc nitrate, zinc sulfate, copper nitrate, copper sulfate and aluminum sulfate; the organic ligand comprises one or a combination of several of ethylenediamine tetraacetic acid and 3- [ (1-carboxynaphthalen-2-yl) oxy ] phthalic acid.
By adopting the technical scheme, the molecular sieve is a crystalline compound, and a pore canal and cavity system with the molecular size is formed by connecting silicon oxygen tetrahedron or aluminum oxygen tetrahedron through oxygen bridging, so that the molecular sieve has the advantages of large specific surface area and high thermal stability, and is a good carrier material; the metal carboxylate catalyst can form a coordination complex with epoxy groups in epoxypropane to carry out catalytic polymerization reaction in the prior reaction, carboxylate anions generated by dissociation can continue to carry out catalytic polymerization reaction when the heat of the system is increased in the later reaction, the metal carboxylate catalyst is loaded on a molecular sieve, the active center of the catalyst is changed, the catalytic efficiency of the catalyst can be increased, the catalyst can be adapted to the processing conditions of high temperature and high pressure in the application, and the catalytic efficiency is reduced due to difficult inactivation. Meanwhile, supercritical carbon dioxide is adopted as carbon dioxide, so that the mass transfer rate is high, and the problem of pore blocking caused by large polymer volume can not be easily generated, thereby limiting the transmission of raw materials and the catalysis effect of the catalyst.
Preferably, the modified molecular sieve is modified by an aminosilane oligomer.
Preferably, the aminosilane oligomer is prepared as follows:
adding an aminosilane coupling agent into a solvent, uniformly mixing to obtain a mixed solution, adding a catalyst into the mixed solution, heating to 40-60 ℃, adding deionized water, stirring, heating to 90-110 ℃, and reacting for 3-5 hours to obtain an aminosilane oligomer.
Preferably, the aminosilane coupling agent further comprises one or a combination of a plurality of gamma-aminopropyl triethoxysilane, gamma-aminopropyl trimethoxysilane, N- (2-aminoethyl) -3-aminopropyl methyl diethoxysilane, gamma-glycidyl ether oxypropyl trimethoxysilane, gamma-glycidyl ether oxypropyl triethoxysilane, gamma-glycidyl ether oxypropyl methyl dimethoxy silane and gamma-glycidyl ether oxypropyl methyl diethoxy silane.
Preferably, the solvent comprises one or more of methanol and ethanol; the catalyst comprises dimethyl sulfoxide.
In the application, because the carbon dioxide is supercritical carbon dioxide, in order to maintain the state, larger pressure and temperature are required to be provided in the processing process, and by adopting the technical scheme, the molecular sieve is easy to collapse and deactivate in the high-temperature high-pressure or hydrothermal environment, so that in order to strengthen the structure of the molecular sieve, the molecular sieve needs to be modified before the metal carboxylate catalyst is loaded; the amino silane oligomer contains terminal amino groups, can form crosslinking with silicon hydroxyl groups on the surface of the molecular sieve, has low molecular weight, does not belong to macromolecular substances, and can gradually form a crosslinked reticular membrane in a pore channel of the molecular sieve after crosslinking, so that the strength of the molecular sieve is enhanced, the molecular sieve is not easy to collapse due to high-temperature and high-pressure environment, the catalyst is deactivated, and the catalytic efficiency of the reaction is reduced. And does not affect the subsequent complex reaction of the molecular sieve with the metal carboxylate catalyst.
Preferably, the modified catalyst is prepared according to the following method:
modification of molecular sieves: activating the molecular sieve at 160-180 ℃ for 4-6 hours, then adding the molecular sieve into toluene, adding an aminosilane oligomer, heating to 120-140 ℃ in nitrogen atmosphere, stirring and reacting for 40-48 hours, and cooling, filtering, washing and drying to obtain the modified molecular sieve;
preparation of modified catalyst: adding the obtained modified molecular sieve into a metal salt aqueous solution, stirring and reacting for 4-6 hours, washing with deionized water after the reaction is finished, adding the obtained modified molecular sieve into an organic solvent, adding an organic ligand, uniformly mixing to obtain a mixture, adding the mixture into a stainless steel autoclave with a polytetrafluoroethylene lining, reacting for 65-75 hours at 140-160 ℃, and washing, drying and calcining after the reaction is finished to obtain the modified catalyst.
Preferably, the organic solvent comprises one or a combination of several of N, N-dimethylformamide, acetone and isopropyl ether.
Preferably, the mass ratio of the aminosilane coupling agent to the molecular sieve is (0.3-0.5): 1.
through adopting above-mentioned technical scheme, metal ion can enter into the aperture of modified molecular sieve, through carrying out the complexation with the silicon hydroxyl and the terminal amino on modified molecular sieve surface and metal ion, fix the metal ion in the aperture of molecular sieve, then add organic ligand, react with the metal ion of fixing on the molecular sieve, form metal carboxylate, the metal carboxylate size that produces often is greater than the aperture size of molecular sieve for metal carboxylate catalyst is difficult for coming off in the polymerization's in-process from the molecular sieve, thereby further promote the catalytic efficiency of catalyst.
In summary, the application has the following beneficial effects:
1. the application provides a synthesis process of polypropylene carbonate, wherein carbon dioxide in a supercritical state is adopted as a carbon dioxide raw material, so that a polypropylene carbonate product can be diluted, the problem of high viscosity of the polypropylene carbonate in the later stage of the preparation process is solved, heat generated in the preparation process of the polypropylene carbonate can be timely dissipated due to high heat transfer rate, a large amount of heat accumulation is prevented, the heat-sensitive polypropylene carbonate is degraded, the reaction probability with propylene oxide and a catalyst can be increased, and the conversion rate of the reaction is increased.
2. The catalyst adopted in the application is a molecular sieve supported metal carboxylate catalyst, so that the active center of the catalyst is changed, the catalytic efficiency of the catalyst can be increased, and meanwhile, the catalyst can be adapted to the processing conditions of high temperature and high pressure in the application, and the catalyst is not easy to deactivate to reduce the catalytic efficiency. The molecular sieve is modified by the aminosilane oligomer, so that the strength of the molecular sieve is enhanced, the molecular sieve is not easy to collapse due to high-temperature and high-pressure environment, and the catalytic efficiency of the catalyst is further improved.
Drawings
FIG. 1 is a flow chart of the overall synthesis process of example 1.
FIG. 2 is a schematic illustration of the catalyst addition portion of the synthesis process of example 1.
Reference numerals illustrate:
1. a solvent storage tank; 2. a catalyst feed tank; 3. a carbon dioxide storage tank; 4. a propylene oxide storage tank; 5. a pressure increasing valve; 6. a polymerization reaction kettle; 7. a polymer storage tank; 8. a twin screw extruder; 9. a catalyst feeding pipe; 10. a high pressure condenser; 11. a low pressure condenser; 12. a low molecular recovery tank; 13. and a tail gas recovery tower.
Detailed Description
Preparation of aminosilane oligomer
Preparation example 1-1, an aminosilane oligomerization, was prepared as follows:
90g of gamma-aminopropyl triethoxysilane is added into 14g of methanol, stirred and mixed, 4g of dimethyl sulfoxide is added, 10g of deionized water is added after the temperature is increased to 50 ℃, the temperature is increased to 100 ℃, and the aminosilane oligomer is obtained after stirring and reacting for 4 hours under the condition that the temperature is kept unchanged.
Preparation example of modified catalyst
Preparation example 2-1, a modified catalyst, was prepared as follows:
taking 100g of molecular sieve, activating for 5 hours at 180 ℃, then adding the molecular sieve into 500ml of toluene, adding 40g of aminosilane oligomer prepared in preparation example 1-1, heating to 120 ℃ in nitrogen atmosphere, stirring and reacting for 42 hours, and cooling, filtering, washing and drying to obtain the modified molecular sieve;
adding 18g of zinc sulfate into 250ml of deionized water, stirring and dissolving, adding 10g of molecular sieve, continuously stirring and reacting for 6 hours, washing with deionized water after the reaction is finished, filtering, adding into 250ml of N, N-dimethylformamide, adding 20g of ethylenediamine tetraacetic acid, uniformly mixing to obtain a mixture, adding the mixture into a stainless steel autoclave with a polytetrafluoroethylene lining, reacting for 70 hours at 150 ℃, washing, drying and calcining after the reaction is finished to obtain the modified catalyst.
Preparation example 2-2, a modified catalyst, differed from preparation example 2-1 only in that the aminosilane oligomer obtained in preparation example 1-1 was added in an amount of 30g.
Preparation example 2-3, a modified catalyst, differed from preparation example 2-1 only in that the aminosilane oligomer obtained in preparation example 1-1 was added in an amount of 50g.
Preparation examples 2-4, a modified catalyst, differed from preparation example 2-1 only in that the amount of zinc sulfate added was 14g and that of ethylenediamine tetraacetic acid was 18g.
Preparation examples 2-5, a modified catalyst, differed from preparation example 2-1 only in that the amount of zinc sulfate added was 20g and that of ethylenediamine tetraacetic acid was 22g.
Preparation examples 2-6, a modified catalyst, differed from preparation example 2-1 only in that the aminosilane oligomer obtained in preparation example 1-1 was added in an amount of 20g.
Preparation examples 2-7, a modified catalyst, differed from preparation example 2-1 only in that the aminosilane oligomer obtained in preparation example 1-1 was added in an amount of 60g.
Preparation examples 2-8, a modified catalyst, differed from preparation example 2-1 only in that ethylenediamine tetraacetic acid was added in an amount of 16g.
Preparation examples 2-9, a modified catalyst, differed from preparation example 2-1 only in that ethylenediamine tetraacetic acid was added in an amount of 24g.
Preparation examples 2-10, a modified catalyst, differed from preparation example 2-1 only in that the molecular sieve was not subjected to the modification treatment of the aminosilane oligomer obtained in preparation example 1-1.
Preparation examples 2-11, a modified catalyst, were prepared as follows:
18g of zinc sulfate, 250ml of N, N-dimethylformamide and 20g of ethylenediamine tetraacetic acid are uniformly mixed to obtain a mixture, the mixture is added into a stainless steel autoclave with a polytetrafluoroethylene lining, the reaction is carried out for 70 hours at 150 ℃, and after the reaction is finished, the modified catalyst is obtained through washing, drying and grinding.
Examples
Example 1 a process for the synthesis of polypropylene carbonate, with reference to fig. 1 and 2, comprises the following process steps:
s1, conveying 160kg of dehydrated dichloromethane from a solvent storage tank 1 to a polymerization reaction kettle 6;
s2, adding 10kg of dichloromethane and 1.6kg of the modified catalyst prepared in the preparation example 2-1 into a catalyst feeding tank 2, replacing air in the catalyst feeding tank 2 by carbon dioxide gas, uniformly mixing the dichloromethane and the modified catalyst, and conveying the mixture into a polymerization reaction kettle 6 through a catalyst feeding pipe 9;
s3, conveying the carbon dioxide gas in the 250kg carbon dioxide storage tank 3 to the polymerization reaction kettle 6 through the pressure increasing valve 5, and continuously conveying (maintaining the conveying speed of 6.4 kg/h) the propylene oxide (the water content is less than 100 ppm) in the 80kg propylene oxide storage tank 4 to the polymerization reaction kettle 6; raising the temperature in the polymerization reaction kettle 6 to 75 ℃, increasing the pressure to 6.5MPa, and continuing stirring for reaction for 3 hours after conveying is finished;
s4, after the reaction is finished, conveying the polymer obtained in the polymerization reaction kettle 6 into a polymer storage tank 7, adding 0.33kg of ethylboronic acid, stirring and mixing, and cooling to room temperature; conveying the cooled polymer into a double-screw extruder 8 for extrusion granulation to obtain polypropylene carbonate; wherein the temperature of the twin-screw extruder 8 is set to 125-155 ℃ and the vacuum degree is 20kPa.
S5, waste liquid generated in the polymerization reaction kettle 6 and the polymer storage tank 7 and gas generated by devolatilization of the double-screw extruder 8 enter a tail gas recovery tower 13 through a high-pressure condenser 10, a low-pressure condenser 11 and a low-molecular recovery tank 12 for recovery treatment.
Example 2 a process for the synthesis of polypropylene carbonate comprising the following process steps:
s1, conveying 120kg of dehydrated dichloromethane from a solvent storage tank 1 to a polymerization reaction kettle 6;
s2, adding 15kg of dichloromethane and 1.6kg of the modified catalyst prepared in the preparation example 2-2 into a catalyst feeding tank 2, replacing air in the catalyst feeding tank 2 by carbon dioxide gas, uniformly mixing the dichloromethane and the modified catalyst, and conveying the mixture into a polymerization reaction kettle 6 through a catalyst feeding pipe 9;
s3, conveying 200kg of carbon dioxide gas in a carbon dioxide storage tank 3 to a polymerization reaction kettle 6 through a pressure increasing valve 5, and continuously conveying (maintaining the conveying speed of 6.4 kg/h) 80kg of propylene oxide (with the water content less than 100 ppm) in a propylene oxide storage tank 4 to the polymerization reaction kettle 6; raising the temperature in the polymerization reaction kettle 6 to 60 ℃, increasing the pressure to 4MPa, and continuing stirring and reacting for 3 hours after conveying is finished;
s4, after the reaction is finished, conveying the polymer obtained in the polymerization reaction kettle 6 into a polymer storage tank 7, adding 0.33kg of ethylboronic acid, stirring and mixing, and cooling to room temperature; conveying the cooled polymer into a double-screw extruder 8 for extrusion granulation to obtain polypropylene carbonate; wherein the temperature of the twin-screw extruder 8 is set to 125-155 ℃ and the vacuum degree is 20kPa.
S5, waste liquid generated in the polymerization reaction kettle 6 and the polymer storage tank 7 and gas generated by devolatilization of the double-screw extruder 8 enter a tail gas recovery tower 13 through a high-pressure condenser 10, a low-pressure condenser 11 and a low-molecular recovery tank 12 for recovery treatment.
Example 3 a process for the synthesis of polypropylene carbonate comprising the following process steps:
s1, conveying 240kg of dehydrated dichloromethane from a solvent storage tank 1 to a polymerization reaction kettle 6;
s2, adding 10kg of dichloromethane and 1.6kg of the modified catalyst prepared in the preparation examples 2-3 into a catalyst feeding tank 2, replacing air in the catalyst feeding tank 2 with carbon dioxide gas, uniformly mixing the dichloromethane and the modified catalyst, and conveying the mixture into a polymerization reaction kettle 6 through a catalyst feeding pipe 9;
s3, conveying 300kg of carbon dioxide gas in a carbon dioxide storage tank 3 to a polymerization reaction kettle 6 through a pressure increasing valve 5, and continuously conveying (maintaining the conveying speed of 6.4 kg/h) 80kg of propylene oxide (with the water content less than 100 ppm) in a propylene oxide storage tank 4 to the polymerization reaction kettle 6; raising the temperature in the polymerization reaction kettle 6 to 85 ℃, increasing the pressure to 8MPa, and continuing stirring and reacting for 3 hours after conveying is finished;
s4, after the reaction is finished, conveying the polymer obtained in the polymerization reaction kettle 6 into a polymer storage tank 7, adding 0.33kg of ethylboronic acid, stirring and mixing, and cooling to room temperature; conveying the cooled polymer into a double-screw extruder 8 for extrusion granulation to obtain polypropylene carbonate; wherein the temperature of the twin-screw extruder 8 is set to 125-155 ℃ and the vacuum degree is 20kPa.
S5, waste liquid generated in the polymerization reaction kettle 6 and the polymer storage tank 7 and gas generated by devolatilization of the double-screw extruder 8 enter a tail gas recovery tower 13 through a high-pressure condenser 10, a low-pressure condenser 11 and a low-molecular recovery tank 12 for recovery treatment.
Example 4, a process for synthesizing polypropylene carbonate, was different from example 1 only in that the modified catalyst obtained in preparation example 2-1 was added in an amount of 0.8kg.
Example 5 a process for synthesizing polypropylene carbonate differs from example 1 only in that the modified catalyst obtained in preparation example 2-1 was added in an amount of 2.4kg.
Example 6, a process for synthesizing polypropylene carbonate, differs from example 1 only in that the amount of carbon dioxide added is 150kg; and the modified catalyst prepared in preparation example 2-1 was replaced with the modified catalyst prepared in preparation example 2-4 in equal amount.
Example 7, a process for synthesizing polypropylene carbonate, differs from example 1 only in that the amount of carbon dioxide added is 400kg; and the modified catalyst obtained in preparation example 2-1 was replaced with the modified catalyst obtained in preparation example 2-5.
Example 8, a process for the synthesis of polypropylene carbonate, differs from example 1 only in that the modified catalyst obtained in preparation 2-1 was replaced with the modified catalyst obtained in preparation 2-6 in equal amounts.
Example 9, a process for the synthesis of polypropylene carbonate, differs from example 1 only in that the modified catalyst obtained in preparation 2-1 was replaced with the modified catalyst obtained in preparation 2-7 in an equivalent amount.
Example 10, a process for the synthesis of polypropylene carbonate, differs from example 1 only in that the modified catalyst obtained in preparation 2-1 was replaced with the modified catalyst obtained in preparation 2-8 in equal amounts.
Example 11 a process for the synthesis of polypropylene carbonate differs from example 1 only in that the modified catalyst obtained in preparation 2-1 is replaced by the modified catalyst obtained in preparation 2-9 in equal amounts.
Example 12 a process for the synthesis of polypropylene carbonate differs from example 1 only in that the modified catalyst obtained in preparation 2-1 is replaced by the modified catalyst obtained in preparation 2-10 in equal amounts.
Example 13, a process for the synthesis of polypropylene carbonate, differs from example 1 only in that the modified catalyst obtained in preparation 2-1 was replaced with the modified catalyst obtained in preparation 2-11 in equal amounts.
Comparative example
Comparative example 1, a process for the synthesis of polypropylene carbonate, differs from example 1 only in that S3 is carried out according to the following process steps: delivering 250kg of carbon dioxide gas in a carbon dioxide storage tank 3 to a polymerization reaction kettle 6, and simultaneously continuously delivering 80kg of propylene oxide (with a water content of less than 100 ppm) in a propylene oxide storage tank 4 to the polymerization reaction kettle 6 (maintaining a delivery rate of 6.4 kg/h); and raising the temperature in the polymerization reaction kettle 6 to 40 ℃, increasing the pressure to 2MPa, and continuing stirring and reacting for 3 hours after conveying.
Performance test
1. Raw material conversion test: the mass of the obtained polypropylene carbonate was weighed, and the conversion of the raw material was calculated according to the following formula:
wherein m is 1 Is the mass of carbon dioxide added; m is m 2 Is the mass of propylene oxide added.
2. Molecular weight test: the weight average molecular weight of the obtained polypropylene carbonate was tested by GPC (gel permeation chromatography).
3. Tensile property test: determination of tensile Properties of plastics according to GB/T1040.2-2022 part 2: test conditions for molding and extrusion of plastics the tensile strength of the resulting polypropylene carbonate was tested.
The specific test results are shown in Table one.
Table test results of polypropylene carbonate
From Table I, in combination with examples 1 to 7, it can be seen that the raw material conversion rates of examples 2 to 7 are not significantly different from example 1, the weight average molecular weight and tensile strength of the polypropylene carbonate obtained in examples 2 to 7 are not significantly changed from those of the polypropylene carbonate obtained in example 1, and it is demonstrated that the raw material conversion rates of examples 2 to 7 are similar to example 1, and the mechanical properties of the polypropylene carbonate obtained are similar to example 1. The reason for this may be that examples 2 to 7 merely changed the ratio of the raw materials, the ratio of the raw materials in the preparation process of the modified catalyst, and the related process parameters of the polypropylene carbonate within the required range, which means that the raw material ratio and the conversion rate of the raw materials of the polypropylene carbonate and the properties of the obtained polypropylene carbonate were not significantly affected by the change of the raw material ratio and the process parameters within the required range.
In combination with examples 1, 8, 9 and 12, it can be seen that the conversion of the raw materials in examples 8 and 9 is reduced compared with example 1, and the conversion in example 12 is significantly reduced; the weight average molecular weight and tensile strength of the polypropylene carbonates obtained in examples 8, 9 and 12 were reduced compared to example 1, indicating a reduction in the conversion of examples 8 and 9, and a more pronounced reduction in example 12, and a reduction in the properties of the polypropylene carbonates obtained. The reason for this may be that the modified catalyst employed in example 8 was reduced in the amount of aminosilane oligomer added during the preparation, the protective film attached to the molecular sieve surface was reduced, the functional material reinforcing the molecular sieve structure was reduced, so that the molecular sieve collapsed due to the inability to withstand the polymerization conditions of high temperature and high pressure during the reaction, the modified catalyst was deactivated, the catalytic efficiency was lowered, the conversion of the raw material was lowered, the molecular weight obtained was lowered, and the performance was also lowered; the modified catalyst in example 12 was free of aminosilane oligomer during the preparation process, and the number of molecular sieve collapse was increased, resulting in a more significant decrease in conversion and a decrease in performance. The modified catalyst used in example 9 had an increased amount of aminosilane oligomer added during the preparation, and on the one hand, the binding force between the metal ion and the modified molecular sieve was decreased during the coordination, and on the other hand, excessive aminosilane oligomer resulted in blocking of the pore diameter in the molecular sieve, and metal carboxylate was difficult to form in the molecular sieve, resulting in a decrease in the catalytic efficiency, and further, in a decrease in the conversion rate and a decrease in the molecular weight, and the properties of the obtained polypropylene carbonate were decreased.
In combination with examples 1, 10 and 11, it can be seen that the raw material conversion of examples 10 and 11 was reduced as compared with example 1, and the weight average molecular weight and tensile strength of the polypropylene carbonate obtained in examples 10 and 11 were reduced as compared with example 1; illustrating the reduced conversion in examples 10 and 11, the resulting polypropylene carbonate had reduced performance. The reason for this may be that the modified catalyst employed in example 10 was reduced in the amount of the organic ligand added during the preparation, the metal carboxylate formed was reduced, the catalytic efficiency was lowered, and further the conversion of the raw material was lowered, the molecular weight of the obtained polypropylene carbonate was reduced, and the performance was lowered; the modified catalyst used in example 11 increased the amount of organic ligand added during the preparation process, and too much metal carboxylate formed in the pore diameter of the modified molecular sieve, blocked the pore diameter of the molecular sieve, reduced the mass transfer efficiency of the raw material, and reduced the catalytic efficiency, thus resulting in a decrease in the conversion rate of the raw material, and also in the performance of the obtained polypropylene carbonate.
In combination with example 1 and example 13, it can be seen that example 13 has a reduced conversion of the raw material, a reduced weight average molecular weight of the obtained polypropylene carbonate and a reduced tensile strength compared to example 1, indicating that the conversion of example 13 and the properties of the obtained polypropylene carbonate have been reduced compared to example 1. The reason for this is probably that the metal carboxylate catalyst in example 13 was not supported on the molecular sieve, and the metal carboxylate catalyst was difficult to exert its catalytic action under the processing environment of high temperature and high pressure, resulting in a decrease in catalytic efficiency, and thus a decrease in conversion of the raw material, and also a decrease in the performance of the obtained polypropylene carbonate.
In combination with example 1 and comparative example 1, it can be seen that comparative example 1 has a significant decrease in the conversion of the raw material, the weight average molecular weight and the tensile strength of the obtained polypropylene carbonate as compared with example 1, indicating a significant decrease in the conversion of comparative example 1 and the properties of the obtained polypropylene carbonate as compared with example 1. The reason for this is probably that the carbon dioxide raw material used in comparative example 1 was not subjected to the pressure boosting treatment to form a supercritical state, the temperature and pressure were lowered during the polymerization reaction, the carbon dioxide in a gaseous state was not able to act as a solvent like supercritical carbon dioxide, the increase in viscosity at the latter stage of the reaction was prevented, the polymerization probability with propylene oxide was lowered, the heat transfer efficiency was also lowered, and the formed polypropylene carbonate was easily degraded, resulting in a significant decrease in the conversion of the raw material of comparative example 1, and the properties of the obtained polypropylene carbonate were also significantly lowered.
The present embodiment is merely illustrative of the present application and is not intended to be limiting, and those skilled in the art, after having read the present specification, may make modifications to the present embodiment without creative contribution as required, but is protected by patent laws within the scope of the claims of the present application.

Claims (10)

1. The synthesis process of the polypropylene carbonate is characterized by comprising the following steps of:
s1, dehydrating the reaction solvent 1;
s2, mixing the reaction solvent 2 with the modified catalyst in the carbon dioxide atmosphere to obtain a catalyst mixed solution;
s3, carrying out pressurization treatment on carbon dioxide, blending with a mixed solution of a reaction solvent 1 and a catalyst, continuously adding propylene oxide, and then stirring and reacting for 2-3 hours;
s4, adding a terminator after the reaction is finished, stirring, mixing and cooling, extruding and granulating the obtained polymer to obtain the polypropylene carbonate;
s5, condensing waste liquid and gas generated in the reaction process, and then recycling;
the carbon dioxide which participates in the reaction in the step S3 is supercritical carbon dioxide.
2. The process for synthesizing polypropylene carbonate according to claim 1, wherein the reaction solvent 1 comprises one or a combination of several of dichloromethane, ethyl acetate, acetone and ethylene dichloride; the reaction solvent 2 comprises one or a combination of more of dichloromethane and acetone.
3. The process for synthesizing polypropylene carbonate according to claim 1, wherein the modified catalyst is a molecular sieve supported metal carboxylate catalyst.
4. The process for synthesizing polypropylene carbonate according to claim 3, wherein the raw materials of the molecular sieve supported metal carboxylate catalyst comprise (1.4-2) by mass ratio: (1.8-2.2): 1, organic ligands and modified molecular sieves.
5. The process for synthesizing polypropylene carbonate according to claim 4, wherein the metal salt comprises one or a combination of several of zinc nitrate, zinc sulfate, copper nitrate, copper sulfate and aluminum sulfate; the organic ligand comprises one or a combination of several of ethylenediamine tetraacetic acid and 3- [ (1-carboxynaphthalen-2-yl) oxy ] phthalic acid.
6. The process for synthesizing polypropylene carbonate according to claim 4, wherein the modified molecular sieve is subjected to an aminosilane oligomer modification treatment.
7. The process for synthesizing polypropylene carbonate according to claim 4, wherein the modified catalyst is prepared by the following method:
modification of molecular sieves: activating the molecular sieve at 160-180 ℃ for 4-6 hours, then adding the molecular sieve into toluene, adding an aminosilane oligomer, heating to 120-140 ℃ in nitrogen atmosphere, stirring and reacting for 40-48 hours, and cooling, filtering, washing and drying to obtain the modified molecular sieve;
preparation of modified catalyst: adding the obtained modified molecular sieve into a metal salt aqueous solution, stirring and reacting for 4-6 hours, washing with deionized water after the reaction is finished, adding the obtained modified molecular sieve into an organic solvent, adding an organic ligand, uniformly mixing to obtain a mixture, adding the mixture into a stainless steel autoclave with a polytetrafluoroethylene lining, reacting for 65-75 hours at 140-160 ℃, and washing, drying and calcining after the reaction is finished to obtain the modified catalyst.
8. The process for synthesizing polypropylene carbonate according to claim 1, wherein the amount of the modified catalyst added is 1 to 3% by mass of the propylene oxide.
9. The process for synthesizing polypropylene carbonate according to claim 1, wherein the reaction pressure of the stirring reaction in the step S3 is 2.5 to 10MPa; the reaction temperature of the stirring reaction in the step S3 is 50-110 ℃.
10. The process for synthesizing polypropylene carbonate according to claim 1, wherein the mass ratio of carbon dioxide to propylene oxide in the step S3 is (4.5 to 45): 8.
CN202311346291.5A 2023-10-17 2023-10-17 Synthesis process of polypropylene carbonate Pending CN117247532A (en)

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