Method for the coupled production of polyurethanes with reduced co2-footprint

Abstract

The invention relates to a method for the coupled production of polyurethanes. Polyurethane can be produced with a reduced CO2 footprint by means of the energetic combination of the polyurethane synthesis with preceding process steps.

Description

[0001] Description

[0002] Process for the coupled production of polyurethanes with reduced CC>2 footprint

[0003] The invention relates to a process for the coupled production of polyurethanes with a reduced CC>2 footprint for use in a motor vehicle.

[0004] The use of renewable raw materials is a promising lever for improving the overall CO2 footprint of vehicles. Sustainable polymer solutions are becoming increasingly important in the automotive industry.

[0005] Essentially, the following strategies can be mentioned: polymers based on renewable raw materials and polymers that are recovered as recycled plastics

[0006] Polymers based on renewable raw materials, i.e., bio-based polymers, are known to keep the carbon footprint low over the entire product life cycle compared to petrochemical alternatives. According to the second alternative, polymers from recycled processes are used to keep the carbon footprint low through a closed material cycle.

[0007] However, these two polymer classes are not suitable for use in applications with demanding requirements, since neither the bio-based approaches nor the recycled plastics allow for control of the molecular weight and thus the physical, mechanical and chemical properties, on the one hand due to natural synthesis processes and on the other hand due to degradation effects in the recycling process.

[0008] The object of the invention is to provide processes for the production of polymers which are sustainable and have an advantageous property profile.

[0009] The problem is solved by a process for producing polyurethane comprising:

[0010] (1) in a first process step, the extraction of atmospheric CO2;

[0011] (2) in a second process step, the production of a diol compound (diol monomer) from the obtained atmospheric CO2; (3) in a third process step, the polycondensation of the diol compound to form polyurethane; wherein the third process step is energetically coupled with the second process step and / or the first process step.

[0012] The polymers based on atmospherically bound CO2 obtained by the process according to the invention advantageously possess a defined molecular weight and a defined molecular weight distribution. This allows for the creation of a property profile specific to the respective application, which is chemically indistinguishable from petrochemical plastics formulations, but exhibits a negative CO2 balance compared to petrochemical polymer solutions.

[0013] Overall, the process according to the invention makes it possible to produce thermoplastic polymers based on bound CO2 which, in addition to the properties of easy processability in the form of forming processes, also have a property profile specific to the respective application and have an improved CO2 balance over the product life cycle.

[0014] US 2020 / 0291901 A1 and WO 2019 / 161114 A1 describe ways to capture atmospheric CO2. This CO2 can be used for synthesis purposes.

[0015] Extracting atmospheric CO2 for synthesis purposes is energy-intensive. Extracting one ton of CO2 typically requires large amounts of electrical and thermal energy.

[0016] The second step, the production of a diol compound (in particular a polymerizable diol monomer) from the extracted atmospheric CO2, also proceeds endergonic and requires the supply of energy.

[0017] The process according to the invention advantageously provides for coupling the thermodynamic driving force of polyurethane formation with the first and / or the second process step, i.e. the preparation of the diol compound, and / or particularly preferably with the recovery of atmospheric CO2.

[0018] The energetic coupling of the steps can be achieved either directly by supplying the thermal energy generated in the third step and / or by converting it into other forms of energy, particularly electrical energy. In particular, the energetic coupling can be achieved directly by supplying the thermal energy generated in the third step, i.e., thermally coupling the steps through a combined process involving heat exchange. This form of coupling is preferred because the thermal energy can be used directly to extract the CO2 from the air.

[0019] Alternatively, conversion into other forms of energy, particularly electrical energy, is possible. The conversion of thermal energy into electrical energy can be achieved, for example, by turbines or thermoelectric generators. The thermal energy obtained in the third process step can first be converted into electrical energy and then used for the electrochemical synthesis of the diol and / or isocyanate, or, in particular, for the recovery of CO2.

[0020] According to a particularly preferred embodiment, the energy coupling occurs both through direct thermal coupling and through conversion into electrical energy. This particularly advantageously allows the DAC (Direct Air Capture) process, which requires both thermal and electrical energy, to be implemented in an optimal combined process.

[0021] The feature that the third process step is energetically coupled with the second process step and / or the first process step represents a particular advantage of the process according to the invention. In this way, polymer production can be carried out on the basis of the CO2 contained in the atmosphere without these advantages being offset by the increased energy expenditure which results in the first process step for the extraction of the atmospheric CO2 and / or in the second process step for the synthesis of the diol compound.

[0022] According to a preferred embodiment, a method is described, wherein the first method step comprises the removal / extraction of CO2 from ambient air.

[0023] According to a preferred embodiment, a method is further described, wherein the first method step is designed as a “direct air capture method”.

[0024] According to a preferred embodiment, a process is further described wherein the diol compound according to the second process step comprises at least one compound selected from 2,3-furandiol, propylene glycol and / or monoethylene glycol, wherein 2,3-furandiol is preferred.

[0025] According to a preferred embodiment, a process is further described wherein the preparation of the diol compound from the obtained atmospheric CO2 is preferably carried out by electrochemical reduction.

[0026] Since the energetic coupling of the steps can be achieved by converting the heat energy generated in the third step into electrical energy, an electrochemical reaction in the second step is advantageous, as this enables a process-efficient energetic coupling of the processes.

[0027] According to a preferred embodiment, a process is further described wherein the preparation of the diol compound from the obtained atmospheric CO2 is carried out using a catalyst, preferably a transition metal catalyst, particularly preferably a nickel catalyst.

[0028] According to a preferred embodiment, a process is further described wherein the polyurethane obtained is incorporated as a material into a motor vehicle.

[0029] The first process step, which relates to the extraction of CO2 from the atmosphere, is described in more detail below:

[0030] This step involves the extraction of carbon dioxide from the atmosphere. This process cycle is preferably divided into the substeps of sorption and desorpion.

[0031] For this purpose, the ambient air with the resulting CO2 content is first passed through a filter unit and the carbon dioxide is separated from the ambient air using suitable sorbents.

[0032] This is followed by thermal desorption. This is preferably carried out at temperatures between 70 °C and 180 °C and serves to separate the bound carbon dioxide from the sorbent.

[0033] The first process step described here for extracting atmospheric CO2 requires energy. The energy analysis considers both process steps of the sorption cycle. Sorption of one ton of CO2 typically requires several hundred kWh of electrical energy, and often several times that amount of thermal energy for extraction.

[0034] In particular, the described process uses the "Direct Air Capture" (DAC) method. For this purpose, the ambient air, preferably with 400 ppm CO2, is first passed through a filter unit of the DAC system, and the carbon dioxide is separated from the ambient air using suitable sorbent materials. Both physisorption and chemisorption processes can be used to separate the carbon dioxide from the ambient air. Thermal desorption then occurs, preferably at 100 °C, to separate the bound carbon dioxide from the sorbent. Both process steps of the sorption cycle are considered in the energy analysis.

[0035] The sorption of one ton of CO2 typically requires 350 kWh of electrical energy and 1,720–3,350 kWh of thermal energy for the process steps. In particular, the electrical energy required for this can preferably be obtained by energy coupling with the third process step.

[0036] With regard to thermal energy, the energetic coupling can be achieved directly by supplying the thermal energy generated in the third step, meaning thermal coupling of the steps through a combined process with heat exchange. This form of coupling is advantageous because the thermal energy can be used directly to extract the CO2 from the air. Electrical energy can be generated by partially converting the thermal energy. The thermal energy generated in the third process step can first be converted into electrical energy and then used to provide the electrical energy required in the sorption process. In this respect, the process represents an optimal combined process.

[0037] According to a highly preferred embodiment, the process is described wherein polyethyleneimine is used as the sorbent material in the DAC process. It has been found that polyethyleneimine has precisely tailored thermal conductivity properties for the described energetic coupling of the process steps.

[0038] The separated carbon dioxide preferably has a purity of > 98% and is used for monomer synthesis in the second process step. The second process step, which relates to monomer synthesis, is described below.

[0039] The monomers comprise two hydroxide groups. According to a further preferred embodiment, the monomer comprises at least one selected from 2,3-furandiol, propylene glycol, and / or monoethylene glycol.

[0040] The starting materials are prepared under mild reaction conditions and voltages < 20 mV. Propylene glycol and monoethylene glycol can also be synthesized using an analogous catalytic process.

[0041] According to a further preferred embodiment, a process for producing polyurethane is described, wherein, in a second process step, a diol compound, for example, 2,3-furandiol, is obtained by reducing CO2. Thus, the 2,3-furandiol is advantageously produced from a non-fossil carbon source.

[0042] According to a further preferred embodiment, a process for producing polyurethane is described, wherein the CO2 is atmospheric CO2. The described thermoplastic polymers therefore advantageously have a reduced or even negative CO2 footprint over the product life cycle. The described process thus contributes to improving the overall CO2 footprint of vehicles. The resulting polymers are sustainable polymers from the biosphere cycle, which are becoming increasingly important in the automotive industry. This is achieved by the polymer described according to this embodiment.

[0043] According to a further preferred embodiment, a process for producing polyurethane is described, wherein the second process step (monomer synthesis) is carried out electrochemically.

[0044] In particular, the electrical energy required for this purpose can preferably be obtained by energetic coupling with the third process step.

[0045] The electrochemical reduction of carbon dioxide using water as a hydrogen source can therefore enable sustainable production of polymers from renewable energy sources. According to a further preferred embodiment, a process for producing polyurethane is described, wherein the second process step is carried out using a catalyst. Overall, the reaction process can be advantageously significantly accelerated by means of transition metal catalysis. A heterogeneous catalytic mode of action of the transition metal is assumed.

[0046] According to a further preferred embodiment, a process for producing polyurethane is described, wherein the second process step further comprises:

[0047] (a) placing a catalyst-coated cathode in an electrolyte together with an anode;

[0048] (b) placing the anode and the cathode in conductive contact with an external power source;

[0049] (c) providing a carbon dioxide source for the cathode; and

[0050] (d) Using the external electricity source to drive an electrolysis reaction at the cathode in which hydrocarbon products, carbon dioxide products, or both are produced. Reference is made to US 10,676,833 B2.

[0051] The third process step, which relates to polymer synthesis, is described below.

[0052] Since the synthesized monomer products contain two hydroxide groups, they can be used in the third process step for the synthesis of polyurethanes.

[0053] The choice of the appropriate monomer structure significantly determines the material properties of the polyurethane. Monoethylene glycol results in a soft polymer with a low glass transition temperature, whereas 2,3-furandiol produces a hard, brittle material with a high glass transition temperature.

[0054] In the property profiles described above, propylene glycol lies between monoethylene glycol and 2,3-furandiol.

[0055] For this purpose, the diol structures are crosslinked to the required polyols using a polycondensation reaction and serve as the starting material for polymer synthesis. Subsequently, the monomers are referred to as polyols due to the described end groups, regardless of their chemical structure. The polyurethane structures and the polymer network are then constructed from the previously synthesized polyols and diisocyanates via polyaddition reactions and the formation of a urethane group. The synthesis of polyurethane formation is highly exothermic (temperature usually well above 100 °C). This reaction heat is used in the described process chain for sorption, desorption, and monomer synthesis.

[0056] According to a preferred embodiment, the process is described wherein, in a further process step, an isocyanate compound is produced by reducing the CO2 obtained in the first process step. According to a further preferred embodiment, the process is described wherein the reduction of the atmospherically obtained CO2 is carried out under transition metal catalysis or electrochemically.

[0057] According to a preferred embodiment, the process is described wherein the third process step is energetically coupled to the further process step which comprises the preparation of the isocyanate compound.

[0058] According to a preferred embodiment, the process is described wherein the isocyanate compound is used in the third process step to prepare the polyurethane.

[0059] Overall, the invention describes a process for producing polyurethane, where the CO2 is atmospheric CO2. Whether the polyurethane was obtained using atmospheric CO2 can be characterized analytically. Isotope measurement, in particular, determines the ratio of two different types of carbon atoms that can occur in CO2 molecules: 13C and 12C, where the number characterizes the mass of the atom. Fossil fuels, for example, are characterized by a low ratio between 13C and 12C. Atmospheric CO2, on the other hand, has a higher ratio between 13C and 12C. The 13C and 12C isotope distribution thus represents a kind of fingerprint for the formation of the product from atmospheric CO2.

[0060] According to a further aspect of the invention, the use of polyurethane in a motor vehicle is described.

[0061] Further preferred embodiments of the invention emerge from the remaining features mentioned in the subclaims.

[0062] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless otherwise stated in individual cases. The invention is explained below in exemplary embodiments with reference to the accompanying drawings. They show:

[0063] Figure 1a shows a second process step for the formation of diol compounds, in particular 2,3-furandiol, by electrochemical reduction of CO2,

[0064] Figure 1b shows a secondary second process step for the formation of isocyanate from Ges and

[0065] Figure 2 shows a third process step for the formation of polyurethanes by polymerization reaction of the diol compounds condensed to polyols with diisocyanates.

[0066] Figure 1a shows how, after the separation of the CO2 in the first process step, a diol compound, here 2,3-furandiol, is obtained in a second process step by electrochemical reduction of the atmospheric CO2.

[0067] Mechanistically, the CC>2 reduction is assumed to occur catalytically via the mechanism shown. In substep 1, CO2 is inserted into a surface hydride bond to generate an adsorbed formate species. This is believed to be the potential-determining step (PDS).

[0068] In step 2, the absorbed formate is profaned and attacked by a second hydride. This hydride forms formaldehyde after cleavage of hydroxide. Formaldehyde is not detected because the resulting formaldehyde is highly reactive.

[0069] Two consecutive, thermodynamically favored aldehyde condensation reactions are then postulated to generate glyceraldehyde. The keto-enol tautomerization is expected to have the highest energy barrier, thus explaining the accumulation of the methylglyoxal precursor. This step is followed by further condensation of aldehyde with formaldehyde on the catalyst. The cyclization forms the stable five-membered ring through intramolecular condensation of an alcohol and an aldehyde. The hydride abstraction, the reaction leading to the formation of the final product, is driven by the stability of the aromatic furan ring. Figure 1b shows a secondary process step for the formation of isocyanate from CO2.This step is referred to here as a "secondary process step" because, like the reaction step shown in Figure 1a, it occurs after the first process step, i.e., the extraction of CC^ from the atmosphere, but before the third process step, i.e., polyurethane formation. This step can occur simultaneously, before, or after the diol synthesis step.

[0070] As in the reaction step for diol production shown in Figure 1a, the isocyanate synthesis in Figure 1b also uses CO2 obtained from the atmosphere.

[0071] The production of formaldehyde from atmospheric CO2 is initiated by the reduction of atmospheric carbon dioxide with hydrogen to an intermediate carbon monoxide, which, through further reduction steps with hydrogen, forms methanol. This reaction can be carried out either with transition metal catalysis or directly electrochemically with suitable electrocatalysts, without forming an intermediate carbon dioxide. Suitable catalysts include Ni, Fe, Ag, and Cu-based phosphorus compounds. Subsequent oxidation of the compound results in formaldehyde.

[0072] The isocyanate is initially produced by reacting aniline with CO2-based formaldehyde in an acidic medium to form diaminophenylmethane. This is then converted to diphenylmethane-4,4'-diisocyanate using phosgene.

[0073] Figure 2 shows the subsequent polyurethane formation. In this third process step for the formation of polyurethanes, a polymerization reaction of the diol compounds produced in the second step is carried out with diisocyanates. This initially forms corresponding polyols, which then react with the diisocyanates. In addition to 2,3-furandiol, as shown in Figure 1a, propylene glycol and monoethylene glycol can also be synthesized using an analogous catalytic process. The synthesized monomer products all contain two hydroxide groups, which can be used in the process step shown in Figure 2 for the synthesis of polyurethanes. The choice of the appropriate monomer structure significantly determines the material properties of the polyurethane.Monoethylene glycol results in a soft polymer with a low glass transition temperature, whereas 2,3-furandiol produces a hard, brittle material with a high glass transition temperature. Propylene glycol lies between monoethylene glycol and 2,3-furandiol in the property profiles described above. To this end, the diol structures are crosslinked using a polycondensation reaction to form the required polyols, which serve as the starting material for polymer synthesis.

[0074] The polymerization of polyols and isocyanates occurs as a polycondensation under relatively mild reaction conditions. The polyurethane structures and the polymer network are constructed from the previously synthesized polyols and diisocyanates through polyaddition reactions and the formation of a urethane group. Polyurethane formation occurs stepwise, with a diol / polyol and a diisocyanate initially forming a bifunctional molecule with an isocyanate group and a hydroxide group. In subsequent synthesis steps, oligomeric structures are constructed from the bifunctional molecular structures with additional monomers. Analogous to classic polyurethane systems, crosslinking of the polymer chains occurs, for example, through the formation of allophanate structures from a reaction of an isocyanate with a urethane group, with multiple amines, or through trimerization reactions of isocyanate structures to form isocyanurates.The synthesis of polyurethane formation is highly exothermic, with a temperature that is usually well above 100°C. This reaction heat is used in the described process chain for sorption, desorption, and monomer synthesis from the first process step and / or the second process steps in the sense of energetic coupling.

[0075] Whether the polyurethane was obtained using atmospheric CO2, according to process steps 1 and 2, can be analytically characterized by isotope measurement. This involves determining the ratio of two different types of carbon atoms that can occur in CO2 molecules: 13C and 12C, where the index characterizes the mass of the atom. Atmospheric CO2 has a higher ratio between 13C and 12C, meaning that the 13C and 12C isotope distribution represents a kind of fingerprint for the formation of the product from atmospheric CO2.

Claims

Patent claims 1. A process for the production of polyurethane comprising: in a first process step the extraction of atmospheric CO2; in a second process step the production of a diol compound from the extracted atmospheric CO2; in a third process step the polycondensation of the diol compound to form polyurethane; wherein the third process step is energetically coupled with the second process step and / or the first process step.

2. The method of claim 1, wherein the first process step comprises the sorption and desorption of atmospheric CO2.

3. Method according to one of the preceding claims, wherein the first method step is designed as a Direct Air Capture method.

4. Method according to the preceding claim, wherein polyethyleneimine is used as the sorbent material.

5. A method according to any of the preceding claims, wherein the diol compound according to the second process step comprises at least one compound selected from 2,3-furandiol, propylene glycol and / or monoethylene glycol.

6. A method for producing polyurethane according to one of the preceding claims, characterized in that the diol compound is produced from the obtained atmospheric CO2 by means of electrochemically carried out reduction.

7. A process for producing polyurethane according to one of the preceding claims, characterized in that in a further process step an isocyanate compound is produced by reducing the CO2 obtained in the first process step.

8. A process for producing polyurethane according to the preceding claim, wherein the third process step is energetically coupled with the further process step comprising the production of the isocyanate compound.

9. A process for producing polyurethane according to the two preceding claims, characterized in that the isocyanate compound is used in the third process step to produce the polyurethane.

10. A process for the production of polyurethane according to the preceding claims 7 to 9, characterized in that the reduction of the atmospherically obtained CO2 is catalyzed by transition metals.

11. A process for producing polyurethane according to the preceding claims 7 to 9, characterized in that the reduction of the atmospherically obtained CO2 is carried out electrochemically.

12. Method according to one of the preceding claims, wherein the polyurethane obtained is incorporated as a material into a motor vehicle.

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