METHOD FOR THE COUPLED PRODUCTION OF POLYURETHANES WITH REDUCED CO2 FOOTPRINT

Abstract

A method for the coupled production of polyurethanes. Polyurethane can be produced with a reduced CO.sub.2 footprint via an energetic combination of the polyurethane synthesis with preceding process steps.

Claims

1. A method for the production of polyurethane, the method comprising: recovering atmospheric CO.sub.2 in a first method step; producing a diol compound from the recovered atmospheric CO.sub.2 in a second method step; and polycondensating the diol compound to form polyurethane in a third method step, wherein the third method step is energetically coupled with the second method step and/or the first method step.

2. The method according to claim 1, wherein the first method step includes the sorption and desorption of the atmospheric CO.sub.2.

3. The method according to claim 1, wherein the first method step is designed as a direct air capture process.

4. The method according to claim 1, wherein polyethylenimine is used as sorbent material.

5. The method according to claim 1, wherein the diol compound according to the second method step includes at least one compound selected from 2,3-furandiol, propylene glycol, and/or monoethylene glycol.

6. The method according to claim 1, wherein the production of the diol compound from the recovered atmospheric CO.sub.2 takes place via electrochemical reduction.

7. The method according to claim 1, wherein in a further method step the production of an isocyanate compound takes place with reduction of the CO.sub.2 recovered in the first method step.

8. The method according to claim 1, wherein the third method step is energetically coupled with the further method step, which includes the production of the isocyanate compound.

9. The method according to claim 7, wherein the isocyanate compound in the third method step is used to prepare the polyurethane.

10. The method according to claim 7, wherein the reduction of the atmospherically recovered CO.sub.2 takes place by transition metal catalysis.

11. The method according to claim 7, wherein the reduction of the atmospherically recovered CO.sub.2 takes place electrochemically.

12. The method according to claim 1, wherein the obtained polyurethane is incorporated as a material in a motor vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0064] FIG. 1a shows a second method step for forming diol compounds, in particular 2,3-furandiol, by electrochemical reduction of CO.sub.2,

[0065] FIG. 1b shows a subordinate second method step for forming isocyanate from CO.sub.2, and

[0066] FIG. 2 shows a third method step for forming polyurethanes by a polymerization reaction of the diol compounds, to be condensed to form polyols, with diisocyanates.

DETAILED DESCRIPTION

[0067] FIG. 1a shows how, after separation of the CO.sub.2 in the first method step, a diol compound, in the present case 2,3-furandiol, is obtained in a second method step by electrochemical reduction of the atmospheric CO.sub.2.

[0068] From a mechanistic standpoint, it is assumed that the CO.sub.2 reduction takes place by catalysis via the illustrated mechanism. In substep 1, CO.sub.2 is inserted into a surface hybrid bond to produce an adsorbed formate species. It is assumed that this is the potential-determining step (PDS).

[0069] In substep 2, the absorbed formate is protonated and attacked by a second hydride. Formaldehyde is formed after hydroxide splits off. Formaldehyde is not detected, since the formaldehyde that forms is highly reactive.

[0070] Two successive thermodynamically preferred aldehyde condensation reactions are then postulated for the production of glyceraldehyde. The keto-enol tautomerization presumably has the highest energy barrier, and thus explains the accumulation of the methylglyoxal precursor. This step is followed by a further condensation of aldehyde with formaldehyde on the catalyst. The cyclization forms the stable five-membered ring by intramolecular condensation of an alcohol and an aldehyde. The hydride abstraction, the reaction to form the end product, is driven by the stability of the aromatic furan ring.

[0071] FIG. 1b shows a subordinate method step for forming isocyanate from CO.sub.2. This step is referred to here as a subordinate second method step because this step, the same as the reaction step shown in FIG. 1a, takes place after the first method step, i.e., the recovery of CO.sub.2 from the atmosphere, but before the third method step, i.e., the polyurethane formation. This step may take place concurrently with, before, or after the diol synthesis step.

[0072] The same as the reaction step for diol production shown in FIG. 1a, the CO.sub.2 recovered from the atmosphere is also used for the isocyanate synthesis in FIG. 1b.

[0073] The production of formaldehyde from atmospheric CO.sub.2 is initiated by a reduction of atmospheric carbon dioxide, using hydrogen, to give a carbon monoxide intermediate which forms the methanol via further reduction steps with hydrogen. This reaction may take place via transition metal catalysis, or by direct electrochemical means using suitable electrocatalysts, without forming a carbon dioxide intermediate. Suitable catalysts include Ni, Fe, Ag, and Cu-based phosphorus compounds. Subsequent oxidation of the compound results in formaldehyde.

[0074] The production of the isocyanate initially takes place via the reaction of aniline with the CO.sub.2-based formaldehyde in acidic medium to give diaminophenylmethane, which is subsequently reacted with phosgene to give diphenylmethane-4,4-diisocyanate.

[0075] FIG. 2 shows the subsequent polyurethane formation. In this third method step for forming polyurethanes, a polymerization reaction of the diol compounds, created in the second step, with diisocyanates is carried out. Corresponding polyols are initially formed, which then react with the diisocyanates. In addition to 2,3-furandiol, as shown in FIG. 1a, propylene glycol and monoethylene glycol may likewise be synthesized using an analogous catalytic process. The synthesized monomer products all contain two hydroxide groups, which in the process step shown in FIG. 2 may be used for the synthesis of polyurethanes. The selection of the appropriate monomer structure is significant in determining the material properties of the polyurethane. Monoethylene glycol results in a soft polymer having a low glass transition temperature, whereas 2,3-furandiol produces a hard, brittle material having a high glass transition temperature. In the property profiles described above, the propylene glycol is between monoethylene glycol and 2,3-furandiol.

[0076] For this purpose, the diol structures are crosslinked via a polycondensation reaction to form the required polyols, and are used as a starting material for the polymer synthesis.

[0077] The polymerization of the polyols and isocyanates takes place as a polycondensation under relatively mild reaction conditions. By use of the previously synthesized polyols and diisocyanates, the polyurethane structures and the polymeric network are subsequently built via polyaddition reactions and the formation of a urethane group. The polyurethane formation proceeds in a stepwise manner, wherein a bifunctional molecule having an isocyanate group and a hydroxide group is initially formed from a diol/polyol and a diisocyanate. In further synthesis steps, oligomeric structures are built from the bifunctional molecule, using further monomers. In a manner analogous to the conventional polyurethane systems, crosslinking of the polymer chains takes place, for example forming allophanate structures from a reaction of an isocyanate with a urethane group, via multiple use of amines and trimerization reactions of isocyanate structures to give isocyanurates. The synthesis of the polyurethane formation proceeds in a strongly exothermic reaction at a temperature that is generally greatly above 100 C. This heat of reaction is utilized in the described process chain for the sorption, desorption, and monomer synthesis from the first method step and/or the second method step in the sense of energetic coupling.

[0078] Whether or not the polyurethane has been obtained using atmospheric CO.sub.2 according to method steps 1 and 2 may be characterized analytically by isotope measurement. In isotope measurement, the ratio of two different types of carbon atoms that may occur in CO.sub.2 molecules is determined: .sup.13C and .sup.12C, where the index number characterizes the mass of the atom. Atmospheric CO.sub.2 has a higher .sup.13C to .sup.12C ratio, so that the .sup.13C and .sup.12C isotope distribution represents a type of fingerprint for forming the product from atmospheric CO.sub.2.

[0079] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.