Polyethylene from co2
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-29
- Publication Date
- 2026-03-11
AI Technical Summary
Current sustainable polymer solutions, such as bio-based and recycled plastics, struggle to achieve defined molecular weight and consistent physical, mechanical, and chemical properties, limiting their suitability for demanding applications, whereas CO2-based polymers offer a specific property profile similar to petrochemical alternatives with improved carbon footprint.
A process involving the electrochemical reduction of CO2 to form monethylene glycol, followed by Corey-Winter elimination to produce ethylene, which is then polymerized into polyethylene, using catalysts like Ni2P/Fe2P, enabling the production of polyethylene with a defined molecular weight distribution and reduced carbon footprint.
This process produces polyethylene with a specific property profile suitable for various applications, enhancing the carbon balance and sustainability of manufactured products, expanding the range of environmentally friendly materials in industries like automotive and construction.
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Abstract
Description
[0001] Description
[0002] Polyethylene from CO2
[0003] The invention relates to a process for producing polyethylene from CO2, polyethylene produced from CO2 and the use of polyethylene from CO2.
[0004] Polyethylene is a plastic produced by the polymerization of ethylene with the general formula -(CH2-CH2)n-. Polyethylene is used, among other things, for the production of films, bottles, pipes, etc. Polyethylene can be produced by several processes. For example, polyethylene can be produced using a high-pressure process at 200°C and 1000 to 2000 bar in the presence of oxygen and free-radical generators. Low-pressure polyethylene with a crystalline structure can be produced using a low-pressure process under the exclusion of air and moisture in the presence of Ziegler-Natta catalysts.
[0005] The use of sustainable materials is an effective lever for improving the overall carbon footprint of vehicles. Sustainable polymer solutions are therefore becoming increasingly important in the automotive industry. The three most relevant raw material sources for sustainable polymers include bio-based approaches based on renewable resources, recycled plastics, and CO2-based polymer approaches. A variety of bio-based polymers (PLA, PHB, etc.) are already known in the literature to keep the carbon footprint low over the entire product life cycle compared to petrochemical alternatives. Furthermore, thermoplastic polymers from recycled processes are increasingly being used to keep the carbon footprint low through a closed material cycle.However, these two polymer classes are not suitable for use in applications with demanding requirements, since both the bio-based approaches and the recycled plastics often cannot achieve a defined molecular weight due to natural synthesis processes on the one hand and degradation effects in the recycling process on the other, and thus a variance in the physical, mechanical and chemical properties occurs.
[0006] Thermoplastic polymers based on CO2 possess a defined molecular weight distribution and thus a property profile specific to the respective application. They are chemically identical to petrochemical polymer solutions. Their greatest advantage over petrochemical polymer solutions is a better carbon dioxide balance.
[0007] EP2711385 A1 discloses a process for producing polyethylene carbonate using zinc glutarate / MAO and zinc itaconate / MAO as catalysts.
[0008] CN 108623813 A discloses an amphiphilic aliphatic polycarbonate-G-polyethylene glycol graft polymer and a process for producing the same.
[0009] The electrochemical selective reduction of CO2 to C3 and C4 is described in Calvinho et al., Energy Environ. Sci. 2018, 11 , 2550-2559.
[0010] The use of CO2 in chemical processes is described, among others, in Alper et al., Petroleum 2017, 3, 109-126.
[0011] The object of the present invention is to provide a process for producing polyethylene, polyethylene and the use of polyethylene according to the invention which at least partially overcomes the above-mentioned disadvantages.
[0012] This object is achieved by the inventive method according to claim 1, a polyethylene according to claim 7 and the use of polyethylene according to claim 8.
[0013] Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred embodiments of the present invention.
[0014] A process for producing polyethylene may comprise the steps:
[0015] - Providing CO2,
[0016] - electrochemical reduction of CO2 to form monoethylene glycol,
[0017] - Conversion of monoethylene glycol to ethylene, and
[0018] - Polymerization of ethylene to polyethylene.
[0019] A process according to the invention for producing polyethylene comprises the steps:
[0020] - Providing CO2,
[0021] - electrochemical reduction of CO2 to monoethylene glycol,
[0022] - Converting the monoethylene glycol to ethylene under Corey-Winter elimination, and
[0023] - Polymerizing the ethylene to polyethylene. The CO2 can be introduced in an appropriate form in a process according to the invention.
[0024] The CO2 can be in liquid or gaseous form.
[0025] The CO2 can be CO2 from petrochemical processes or from natural sources. The CO2 can originate as a main or byproduct of petrochemical processes, from exhaust gases, or from the atmosphere.
[0026] By using CO2 from the atmosphere, the carbon footprint can be significantly reduced and a sustainable process can be provided.
[0027] In a further step of the process according to the invention, the CO2 is electrochemically reduced to form monoethylene glycol. In electrochemical reduction, the CO2 is reduced by supplying electrical energy.
[0028] The electrochemical reduction of CO2 is preferably a catalytic electrochemical reduction. This process uses a catalyst to reduce the energy required for the electrochemical reduction. The catalyst can be a heterogeneous or homogeneous catalyst.
[0029] The electrochemical reduction of CO2 occurs primarily through the addition of CO2 via the oxygen atoms, accompanied by a simultaneous hydride bond, to a catalytically active surface. Protonation of this species can generate formaldehyde as an intermediate. The resulting formaldehyde can then react with another formaldehyde species via a CC coupling reaction at the catalytically active electrode surface to form a glycoaldehyde. This glycoaldehyde can react with reduction via hydride bonding to form the intermediate alkoxide species, which can subsequently form monoethylene glycol (MEG) in aqueous solution.
[0030] The catalytically active surface is preferably the surface of a heterogeneous catalyst. This can be a classic heterogeneous catalyst, such as those used in electrochemical reductions. Depending on the catalyst design, a co-catalyst may also be present in the reaction. Typically, the catalyst or co-catalyst is a transition metal catalyst. The transition metal catalyst is preferably a nickel or iron phosphide catalyst.
[0031] In a preferred embodiment, the catalyst for catalytic electrochemical reduction comprises Ni2P. More preferably, the catalyst for catalytic electrochemical reduction comprises a combination of catalyst and co-catalyst, e.g., Ni2P / Fe2P.
[0032] For electrochemical reduction, it is conceivable that a variety of electrodes could be used. Examples of electrodes include redox electrodes, ion-selective electrodes, gas diffusion electrodes, etc. A gas diffusion electrode is particularly advantageously used in a process according to the invention.
[0033] Furthermore, a process according to the invention comprises the conversion of monoethylene glycol to ethylene. The conversion of monoethylene glycol to ethylene takes place via Corey-Winter elimination. This can be an electrochemical Corey-Winter elimination or a wet-chemical Corey-Winter elimination.
[0034] In an electrochemical Corey-Winter elimination, a potentiostatic electrolysis at -1.45 V vs Ag / AgCl, 2.2 F / mol, RVC (Reticulated Vitreous Carbons = glassy carbon) cathode, for 1.5 hours is used instead of the Corey-Winter reagent trimethyl phosphite at 111°C.
[0035] A process according to the invention preferably involves a wet-chemical Corey-Winter elimination.
[0036] Corey-Winter elimination, also known as Corey-Winter fragmentation, is an olefin synthesis by eliminating vicinal diols. For example, in a wet-chemical Corey-Winter elimination, a diol is reacted with thiophosgene in the presence of 4-dimethylaminopyridine (DMAP) to form a cyclic thionocarbonate. The thionocarbonate can then be converted into an olefin in the presence of a trivalent phosphorus compound. The trivalent phosphorus compound can be trimethyl phosphite. In a further step of the process according to the invention, ethylene is polymerized to polyethylene. This can be done using conventional polymerization processes, such as suspension, bulk, or gas-phase polymerization processes.
[0037] Furthermore, the present invention provides polyethylene produced by a process according to the invention as disclosed herein. The polyethylene preferably has the formula -[CH2-CH2] n - on. Index "n" preferably has a value < 6 million, more preferably < 5 million, most preferably a value in the range < 4 million.
[0038] Polyethylene, as described herein and preferably produced by a process according to the invention, comprises, in particular, carbon from the atmosphere. Thus, polyethylene can be described as a particularly sustainable polymer that can contribute to improving the CO2 balance of the manufactured products.
[0039] Polyethylene can be used in a wide variety of areas, expanding the range of materials that are particularly sustainable and environmentally friendly. Polyethylene produced using a process according to the invention exhibits a reduced carbon footprint of the products manufactured from it, thus improving the carbon footprint over the product's lifetime.
[0040] The present invention therefore also relates to the use of polyethylene as a plastic component.
[0041] Polyethylene is preferably used in the automotive industry.
[0042] The plastic components can be used in the automotive industry or other industrial sectors, such as the construction or electrical industries. Polyethylene according to the invention can also be used in household applications.
[0043] In principle, the polyethylene described herein can be used in the same fields as polyethylene produced by prior art processes.
[0044] Examples in which polyethylene can be used are fuel tanks, washer water tanks, side panels in the automotive industry, packaging in production / logistics, cling film, carrier bags, agricultural films, milk carton coatings, garbage bags, shrink films, sealing media in composite films, cable sheathing, as a dielectric in coaxial cables, films for industrial packaging, bottles for cleaning agents, beverage bottles, household goods, films for hydraulic engineering and landfill construction, geogrids and geotextiles for landfill construction, pump parts, gears, sliding bushings, implants, surfaces of endoprostheses, insulation material for medium and high voltage cables, etc.
[0045] In one embodiment, the plastic component is a fuel tank, a washer fluid tank, a side panel, or packaging in the automotive industry.
[0046] Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:
[0047] Fig. 1 schematically shows an embodiment of a process according to the invention, Fig. 2a and Fig. 2b schematically show the conversion of CO2 to polyethylene,
[0048] Fig. 3 is a detailed overview of an embodiment of a method according to the invention, Fig. 4 is a flow-oriented profile of a gas diffusion electrode and
[0049] Fig. 5 shows a flow-oriented profile of a gas diffusion electrode.
[0050] Fig. 1 schematically shows a process 100 according to the invention for producing polyethylene. First, CO2 is introduced 101. In a subsequent step 102, the introduced CO2 is electrochemically reduced to form monoethylene glycol. The resulting monoethylene glycol is converted to ethylene 103. The ethylene is then polymerized to polyethylene 104.
[0051] Fig. 2a and Fig. 2b schematically show the conversion of CO2 to polyethylene. In a first step, CO2 is converted to monoethylene glycol using a Ni2P / Fe2P catalyst. The conversion preferably takes place under electrochemical reduction using a Ni2P / Fe2P catalyst. The monoethylene glycol is subsequently converted to ethylene in a Corey-Winter elimination using CCl2S and P(OCH3)3 at, for example, 111 °C (Fig. 2a). As an alternative to the wet-chemical Corey-Winter elimination, an electrochemical Corey-Winter elimination can be performed (Fig. 2b). Instead of CCl2S and P(OCH3)3, potentiostatic electrolysis is carried out at -1.45 V vs. Ag / AgCl, 2.2 F / mol, RVC cathode, 1.5 h (see, for example, Löpez-Löpez et al., Beilstein J. Org. Chem. 2018, 14, 547-552). In a polymerization reaction, the ethylene is polymerized to polyethylene.The polymerization reaction can be a suspension polymerization, a bulk polymerization, or a gas-phase polymerization. The index "n" in Fig. 2a and Fig. 2b can depend on the chosen polymerization method.
[0052] Fig. 3 provides a detailed overview of one embodiment of a process according to the invention. The electrochemical reduction of CO2 is initiated by the addition of carbon dioxide via the oxygen atoms with simultaneous hydride bonding to the catalytically active Ni2P surface (the catalytically active Ni2P surface is not shown). Protonation of this species generates formaldehyde as an intermediate. This formaldehyde then reacts with another formaldehyde species via a CC coupling reaction at the catalytically active electrode surface to form a glycoaldehyde. The glycoaldehyde reacts with the reduction by hydride bonding to form the intermediate alcoholate species, which subsequently forms monoethylene glycol (MEG) when dissolved in aqueous solution.
[0053] The Corey-Winter elimination leads to the formation of the olefin and is initiated by a nucleophilic attack of the diol oxygens at the thiocarbonyl carbon atom, forming the cyclic thiocarbonate with the elimination of hydrogen chloride. Subsequently, a nucleophilic attack of the Corey-Hopkins reagent (1,3-dimethyl-2-phenyl-1,3,2-diazaphospholidine) at the sulfur atom occurs, forming a carbanion. The thiophosphoric acid ester is eliminated with the formation of a cyclic carbene, which, with the release of CO2, forms ethene as the reaction product of the second step. The CO2 can be recycled and reused as a starting material for the electrochemical reduction to monoethylene glycol.
[0054] The polymerization of ethene to polyethylene proceeds using known industrial synthesis processes (suspension, bulk or gas phase polymerization processes).
[0055] Example
[0056] 1. Electrochemical reduction on the Ni2P catalyst
[0057] A. Manufacturing the electrolysis cell:
[0058] For the electrochemical reduction of CO2 in monoethylene glycol, a gas diffusion electrode is preferred due to the comparatively slow diffusion processes and the low solubility of CO2 in water. The base frame can be made of titanium or stainless steel alloys with a typical thickness of 2 mm, in which flow-adapted grooves with a depth of 0.8 mm are introduced. An exemplary flow-adapted profile is shown in Fig. 4 and Fig. 5:
[0059] Maximum speed (m / s): 3,717
[0060] Average speed (m / s): 1 ,592
[0061] Flow uniformity (umax / uavg): 2.3
[0062] Loss of active surface: 32%
[0063] Number of grooves: 35, I = 78 mm, b = 1 mm
[0064] The reaction preferably takes place in a flow cell using 1 M KOH as the anolyte and 0.5 M KHCO3 as the catholyte. The separator membrane can be made of, for example, Nafion™.
[0065] B. Production of electrocatalysts:
[0066] The catalyst material was synthesized in a muffle furnace under a defined temperature-time profile. The elements were weighed stoichiometrically according to their respective proportions and heated in sealed quartz glass ampoules under argon. As an example, to prepare the compound Ni2P, 3.956 g of Ni and 1.060 g of P were weighed, ground in a mortar and mixed, and filled into the evacuated ampoule under protective gas. The ampoule was then sealed and heated in the muffle furnace. The temperature program can be structured as follows: RT -> 350 °C -> 450 °C -> 550 °C -> 700 °C. Heating rate: 0.5 °C / min.
[0067] Each stage was held for 6 h and the final temperature was maintained for 24 h.
[0068] The excess Ni was then removed by stirring in 10% HCl under N2 and then washed with distilled water. Phase purity was determined by PXRD (powder diffraction).
[0069] The prepared catalyst materials were applied to the support material using a suitable binder. C. Electrochemical synthesis:
[0070] The electrochemical synthesis was carried out with an initial screening of the catalyst using cyclic voltammetry and electrochemical impedance spectroscopy. The detected required voltage was then applied and maintained potentiostatically, and the electrochemical flow cell was purified by pulsing with increased voltage within a defined time window. The synthesized product mixture consists of monoethylene glycol (MEG), water, and other impurities. The MEG was subsequently purified and separated by electrodeionization and distillation.
[0071] Amount of CO2 per g MEG: 2.8 g, pressure and flow rate depend on cell size
[0072] 2. Corey Winter Elimination
[0073] For the Corey-Winter elimination, 1.0 eq. of MEG was dissolved in dichloromethane (DCM) and 2.4 eq. of 4-dimethylaminopyridine (4-DMAP) at 0 °C. 1.2 eq. of thiophosgene was then added to the solution, and the reaction mixture was stirred for one hour. The reaction product was then isolated by column chromatography on SiO2, and the solvent was distilled off. The thiocarbonate was then reacted with trimethylphosphide in tetrahydrofuran (THF) at 111 °C for 24 h. The reaction product (ethylene) was passed through a gas scrubber and collected.
[0074] 3. Polymerization
[0075] For polymerization, the ethylene was dissolved in n-hexane, cyclohexane, or toluene and polymerized in an autoclave at 70 bar above 130 °C. The solvent was then distilled off.
[0076] List of reference symbols Process for the production of polyethylene Introduction of CO2 Electrochemical reduction of CO2 Conversion of monoethylene glycol to ethylene Polymerization of ethylene to polyethylene
Claims
Patent claims 1. A process for producing polyethylene comprising the steps: - Providing CO2, - electrochemical reduction of CO2 to monoethylene glycol, - Converting the monoethylene glycol to ethylene under Corey-Winter elimination, and - Polymerizing the ethylene to polyethylene.
2. The method according to claim 1, wherein the electrochemical reduction of the CO2 is a catalytic electrochemical reduction.
3. The process of claim 2, wherein the catalytic electrochemical reduction catalyst comprises ^P.
4. The method of claim 1, wherein the Corey-Winter elimination is a wet chemical Corey-Winter elimination.
5. The method of claim 1, wherein the Corey-Winter elimination is an electrochemical Corey-Winter elimination.
6. Polyethylene produced according to at least one of claims 1 to 5.
7. Use of polyethylene according to claim 6 as a plastic component.
8. Use according to claim 7 in the automotive industry.
9. Use according to claim 7 or 8, wherein the plastic component is a fuel tank, a washer fluid tank, a side panel, or a packaging.