Acrylonitrile butadiene rubber (NBR) made from CO2

Abstract

This document discloses a process for the production of acrylonitrile butadiene rubber comprising the steps of introducing CO2, converting the CO2 to methylglyoxal, converting the methylglyoxal to acrylonitrile, and copolymerizing the acrylonitrile with 1,3-butadiene to form acrylonitrile butadiene rubber. Furthermore, acrylonitrile butadiene rubber and its uses are described.

Description

[0001] The invention relates to a process for producing acrylonitrile-butadiene rubber, acrylonitrile-butadiene rubber and the use of acrylonitrile-butadiene rubber.

[0002] The use of sustainable materials is an effective lever for improving the overall CO2 footprint of vehicles. Sustainable polymer solutions are 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.

[0003] A variety of bio-based polymers (PLA, PHB, etc.) are already known in the literature to minimize the carbon footprint over the entire product life cycle compared to petrochemical alternatives. Furthermore, thermoplastic polymers from recycled processes are increasingly being used to minimize the carbon footprint through a closed material cycle. However, these two polymer classes are not suitable for use in applications with demanding requirements, as neither the bio-based approaches nor the recycled plastics can achieve a defined molecular weight, due to natural synthesis processes on the one hand, and degradation effects in the recycling process on the other. This results in variability in the physical, mechanical, and chemical properties.

[0004] Thermoplastic polymers based on CO2 possess a defined molecular weight distribution and thus a property profile specific to the respective application. Chemically, they are generally indistinguishable from petrochemical polymer solutions. Their greatest advantage over petrochemical polymer solutions is a better CO2 footprint.

[0005] Acrylonitrile butadiene rubber (NBR) is a synthetic elastomer with properties similar to natural elastomers. Acrylonitrile butadiene rubber, also called nitrile rubber, is a copolymer of acrylonitrile and 1,3-butadiene.

[0006] Calvinho et al. describe various nickel phosphides that can be used to convert CO2 in aqueous solution into C3-C4 compounds, such as 2,3-furandiol (C4) and the byproduct methylglyoxal (C3) (Calvinho et al., Energy Environ. Sci., 2018, 11, 2550-2559).

[0007] US 2020 / 0347502 A1 also describes nickel phosphides for the electrochemical reduction of CO2 to hydrocarbons using nickel phosphide nanoparticles.

[0008] Lopez et al. describe the electrochemical Corey-Winter elimination reaction using trimethyl phosphite or triethyl phosphite or the well-known Corey-Winter reagent (Lopez et al., Beilstein H. Org. Chem. 2018, 14, 547-552).

[0009] The production of n-butane using a transition metal-catalyzed reaction is also disclosed in the literature (Fujimoto et al. Direct synthesis of propane / butane from synthesis gas. In: Studies in surface science and catalysis. Elsevier, 2007. pp. 349-354).

[0010] The production of 1,3-butadiene from petrochemical sources as well as the conversion of n-butane from CO2 via alternative catalytic synthesis routes is described, among others, in (Hua, Yani, et al. Electrochemical CO2 conversion towards syngas: Recent catalysts and improving strategies for ratio-tunable syngas. Journal of Power Sources, 2022, vol. 535, p. 231453).

[0011] The production of methylglyoxal from propylene glycol by oxidative dehydrogenation is disclosed, among others, in Ai et al., Appl. Catal. A Geberal 2003, 246(1), 97-102.

[0012] The object of the present invention is to provide a process for producing acrylonitrile butadiene rubber, acrylic butadiene rubber and the use of acrylic butadiene rubber which at least partially overcomes the above-mentioned disadvantages.

[0013] This object is achieved by the inventive method according to claim 1, acrylic butadiene rubber according to claim 7 and the use according to claim 8.

[0014] Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred embodiments of the present invention.

[0015] A process according to the invention for producing acrylonitrile butadiene rubber comprises the steps: - Providing CO2, - Conversion of CO2 to methylglyoxal, - converting methylglyoxal to acrylonitrile, and - Copolymerization of acrylonitrile with 1,3-butadiene to form acrylonitrile-butadiene rubber.

[0016] In a process according to the invention, the CO2 can be introduced in an appropriate form. The CO2 can be in solid, liquid, or gaseous form.

[0017] The CO2 can be from petrochemical deposits or from natural sources. The CO2 can be extracted from petrochemical processes, from waste gases, from point sources, from sustainable sources, or from the atmosphere. CO2 extracted in this way can be reused and used as a chemical building block in various reactions. CO2 from petrochemical deposits can, for example, originate as a byproduct from the thermal / catalytic cracking of crude oil.

[0018] The formation of polymer structures from fossil resources has the disadvantage of incorporating limited resources into polymer structures and of being dependent on global petroleum sources.

[0019] In particular, the CO2 balance can be reduced through the use of CO2 from the atmosphere or from sustainable sources, such as the thermal utilization of biogenic waste streams.

[0020] In a preferred embodiment, the CO2 in a process according to the invention is CO2 from the atmosphere. Compared to the use of CO2 from fossil raw materials, the use of CO2 from the atmosphere results in a lower CO2 footprint of the process product, i.e., the acrylonitrile butadiene rubber.

[0021] A method according to the invention may further comprise the step of isolating CO2 from the atmosphere.

[0022] In one embodiment, the conversion of CO2 to methylglyoxal takes place by means of catalysis. Preferably, the conversion takes place in an electrochemical reduction of CO2 using a catalyst. Transition metals or transition metal compounds are possible catalysts.

[0023] The transition metals can be nickel, iron, copper, or molybdenum. The transition metal compounds can be suitable compounds such as phosphides, sulfides, or oxides. Examples of transition metal compounds that can act as catalysts are nickel phosphide (Ni2P) or iron phosphide (Fe2P).

[0024] The use of a mixture of nickel phosphide (Ni-P) and iron phosphide (Fe-P) as the catalyst is preferred. The use of a mixture of Ni2P with Fe2P as the catalyst is particularly preferred. The mass ratio of Ni2P:Fe2P is between 99:1 wt% and 1:99 wt%, preferably between 95:5 wt% and 5:95 wt%, particularly preferably between 90:10 wt% and 10:90 wt%, and most preferably between 25:75 wt% and 75:25 wt%.

[0025] In one embodiment, the conversion of methylglyoxal to acrylonitrile occurs via propene as an intermediate. The conversion of methylglyoxal can occur, for example, via a hydride exchange and a Corey-Winter rearrangement. The hydride exchange can be carried out using suitable reagents. Examples of reagents are LiBH4 or NaBH4.

[0026] 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.

[0027] The reaction can be an electrochemical Corey-Winter elimination or a wet chemical Corey-Winter elimination.

[0028] In an electrochemical Corey-Winter elimination, instead of the Corey-Winter reagent trimethyl phosphite at 111°C, 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.

[0029] A process according to the invention preferably involves a wet-chemical Corey-Winter elimination. In the wet-chemical Corey-Winter elimination, the so-called Corey-Hopkins reagent (1,3-dimethyl-2-phenyl-1,3,2-diazaphospholidine) is preferably used for the conversion of the reactants.

[0030] The propene can be converted to acrylonitrile through a suitable reaction. An exemplary state-of-the-art process is the Sohio process. The large-scale production of acrylonitrile using the Sohio process is a two-step process: In the first step, acrylonitrile, including the resulting byproducts hydrogen cyanide (HCN) and acetonitrile (C2H3N), is synthesized, and in the second step, it is purified.

[0031] Preferably, the propene is reacted with ammonia to form acrylonitrile in a process according to the invention.

[0032] In one embodiment, the propene is converted to acrylonitrile using catalysis. The catalyst can be a metal or a metal compound.

[0033] The metals can be iron, bismuth, or molybdenum. The metal compounds can be suitable compounds such as phosphides, sulfides, or oxides of the respective metals.

[0034] A process according to the invention can further comprise the step of converting carbon dioxide to 1,3-butadiene. The carbon dioxide can come from various sources. If the carbon dioxide originates, for example, from the atmosphere, the CO2 balance of the resulting products can be advantageously influenced.

[0035] The conversion of carbon dioxide to 1,3-butadiene can be carried out using common processes known from the state of the art.

[0036] In one embodiment, the process for producing acrylonitrile butadiene rubber comprises the step of isolating CO2 from the atmosphere. Generally, the CO2 can come from various sources. The CO2 can be of petrochemical origin or from sustainable sources or the atmosphere. If the CO2 comes from sustainable sources or the atmosphere, the carbon footprint of the final products can be improved.

[0037] The isolation of CO2 from the atmosphere can be achieved using common methods such as sorption processes.

[0038] A process according to the invention comprises the step of copolymerizing acrylonitrile and 1,3-butadiene. The copolymerization can be carried out by known polymerization processes. For example, the polymerization can be a free-radical polymerization.

[0039] The copolymerization of acrylonitrile and 1,3-butadiene can be carried out in a specific ratio. The proportion of acrylonitrile is preferably in the range of 10 wt.% to 70 wt.%, more preferably in the range of 15 wt.% to 60 wt.%, and even more preferably in the range of 16 wt.% to 55 wt.%, based on the total weight of the acrylonitrile-1,3-butadiene mixture.

[0040] In a preferred embodiment, an electrocatalytic large-scale conversion of atmospheric CO2 to methylglyoxal takes place, which is then converted to propene by wet-chemical Corey-Winter elimination. The propene can then be reacted with ammonia in upstream reactor systems, as well as with 1,3-butadiene, which can be synthesized from atmospheric CO2 via synthesis gas using downstream oxidative dehydrogenation. The downstream polymerization to NBR can then take place.

[0041] Furthermore, the present invention relates to acrylonitrile butadiene rubber produced by a process according to the invention.

[0042] An acrylonitrile butadiene rubber (NBR) according to the invention has a lower CO2 footprint when using CO2 from the atmosphere than NBR produced from educts from petrochemical sources.

[0043] Furthermore, the present invention relates to the use of acrylonitrile butadiene rubber according to the present invention in the automotive industry.

[0044] An acrylonitrile butadiene rubber according to the invention can be used in media-carrying lines, hydraulic hoses, seals, corrosion-reducing coatings for metal surfaces and dirt-trapping mats, pneumatic and hydraulic seals, O-rings, radial shaft seals, drive and spinning belts, technical rollers, as a base material for laboratory and surgical gloves, chemical-resistant finishing of textiles, sole material, stators in technical systems, hoses in flexible media lines for gases and liquids, as well as in all related plastics manufacturing, plastics processing industries and other end applications not explicitly mentioned.

[0045] By using CO2 from the atmosphere or from sustainable sources, the CO2 footprint of manufactured products can be reduced.

[0046] Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 schematically shows an embodiment of a method according to the invention, Fig. 2 schematically shows the conversion of naphtha to acrylonitrile and 1,3-butadiene, Fig. 3 schematically shows the conversion of CO2 to acrylonitrile, Fig. 4 schematically shows the conversion of CO2 to 1,3-butadiene, and Fig. 5 schematically shows the copolymerization of acrylonitrile and 1,2-butadiene.

[0047] Fig. Figure 1 schematically shows an embodiment of a process 100 for producing acrylonitrile-butadiene rubber. First, CO2 is introduced 101. The CO2 is converted to methylglyoxal 102, and the methylglyoxal is further converted to acrylonitrile 103. In a further step, the acrylonitrile is copolymerized with 1,3-butadiene to form acrylonitrile-butadiene rubber 104.

[0048] Fig. Figure 2 schematically shows the production of acrylonitrile and 1,3-butadiene from naphtha and thus from petrochemical sources. Naphtha is converted to propene, which is then catalytically reacted with ammonia to form acrylonitrile. Butadiene can also be obtained from naphtha via butane using state-of-the-art reactions.

[0049] Fig. Figure 3 schematically shows a process for the production of acrylonitrile from CO2. In a first step, CO2 is catalytically converted to methylglyoxal in an electrochemical reaction. The electrochemical reduction of CO2 is initiated by the addition of CO2 via the oxygen atoms, accompanied by simultaneous hydride bonding, to the catalytically active Ni2P surface. Protonation of this species generates formaldehyde as an intermediate. This formaldehyde then reacts with two other formaldehyde species via CC coupling reactions at the catalytically active electrode surface via a glycoaldehyde to form glyceraldehyde (2,3-dihydroxypropanal).

[0050] By cleavage of the hydroxide group, the reaction product (methylglyoxal, 2-oxopropanal) is obtained.

[0051] The hydride exchange can be carried out on methylglyoxal using lithium borohydride, in which four methylglyoxal molecules attach to the boron atom via the oxygen atoms of the keto group, resulting in hydrogenation of the carbonyl carbon. In an acidic medium, the boric acid can then be cleaved off to form hydroxyacetone (1-hydroxypropan-2-one). A further reaction of the sodium borohydride leads to the formation of propylene glycol as a reaction product.

[0052] 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 at the sulfur atom occurs, forming a carbanion. The thiophosphoric acid ester is eliminated to form a cyclic carbene, which, with the release of CO2, forms propene as the reaction product.

[0053] The reaction of the CO2-based propene with ammonia can then be carried out on an industrial scale using known processes (e.g., the Sohio process). The industrial-scale production of acrylonitrile proceeds in two steps: In the first step, acrylonitrile, including the resulting by-products hydrogen cyanide (HCN) and acetonitrile (C2H3N), is synthesized, and in the second step, it is purified. For example, in a fluidized-bed reactor, propene, ammonia, and air are added to a fluidized bed of catalyst (Bi compounds). The reaction is highly exothermic, although the reactor temperature can be kept constant using water cooling units. In the second step, the product gases and the remaining air components are passed into an absorber, where they are separated. What remains is a mixture of water, acrylonitrile, hydrogen cyanide, and acetonitrile, which can be fed into the distillation column for fractional distillation.Acrylonitrile can then be obtained as a colorless liquid.

[0054] Fig. Figure 4 schematically shows the conversion of CO2 to 1,3-butadiene. The conversion of carbon dioxide to n-butane can be achieved using transition-metal-catalyzed reactions. In the first step, CO2 reduction to carbon monoxide can be carried out using state-of-the-art technology (Hua, Yani, et al. "Electrochemical CO2 conversion towards syngas: Recent catalysts and improving strategies for ratio-tunable syngas." Journal of Power Sources, 2022, Vol. 535, p. 231453). The preferred variant consists of a gas diffusion electrode with an electrocatalyst consisting of at least one of the following elements: Zn, Co, Cr, Ni, Cu, and Fe. In the second step, the synthesis gas can be passed in a defined ratio (Ar:H2:CO = 3:65:32) onto a Pd / Cr-Zn catalyst at 2.1 MPa and 375-400 °C and the n-butane can be separated.

[0055] 1,3-Butadiene can be produced from n-butane using oxidative dehydrogenation. In this process, hydrogen is released from the hydrocarbon using platinum or chromium-based catalysts. The reaction typically takes place at elevated temperatures of 700-800°C, and the reaction product can be collected as a colorless gas.

[0056] Fig. Figure 5 schematically shows the copolymerization of acrylonitrile and 1,3-butadiene. Acrylonitrile-butadiene rubber can be produced by free-radical copolymerization of 1,3-butadiene and acrylonitrile in an aqueous emulsion. A distinction is made between warm and cold polymerization based on the polymerization temperature. Acrylonitrile can be copolymerized with butadiene in any ratio, with the acrylonitrile content typically being between 18 and 51 wt.%. Example 1 1.) Electrochemical reduction on the Ni2P catalyst: The electrochemical reduction of CO2 is initiated by the addition of carbon dioxide via the oxygen atoms, accompanied by simultaneous hydride bonding, to the catalytically active Ni2P surface. Protonation of this species generates formaldehyde as an intermediate. The formaldehyde then reacts with two other formaldehyde species via CC coupling reactions at the catalytically active electrode surface, forming a glycoaldehyde to form glyceraldehyde (2,3-dihydroxypropanal). Cleavage of the hydroxide group yields the reaction product of the first step (methylglyoxal, 2-oxopropanal). 2.) Hydride exchange with sodium borohydride in EtOH: The hydride exchange occurs on methylglyoxal with the aid of sodium borohydride, in which four methylglyoxal molecules attach to the boron atom via the oxygen atoms of the keto group, resulting in hydrogenation of the carbonyl carbon. Subsequently, the boric acid is cleaved in an acidic medium to form hydroxyacetone (1-hydroxypropan-2-one). A further reaction of the sodium borohydride leads to the formation of propylene glycol as the reaction product. 3.) Corey-Winter elimination: The Corey-Winter elimination leads to the formation of propylene and is initiated by a nucleophilic attack of the diol oxygens at the thiocarbonyl carbon atom. The cyclic thiocarbonate is formed with the elimination of hydrogen chloride. Subsequently, a nucleophilic attack of the Corey-Hopkins reagent at the sulfur atom occurs, forming a carbanion. The thiophosphoric acid ester is eliminated to form a cyclic carbene, which, with the elimination of CO2 (cyclic use as the reactant in step 1), forms propene as the reaction product. 4.) Polymerization: The polymerization of propene to acrylonitrile is carried out using the Sohio process. Example 2 1. Electrochemical reduction on a Ni2P catalyst. (exp. 11.17 kWh / kg methylglyoxal) 2. Hydride exchange on sodium borohydride in EtOH 0°C -> RT, 65 min, (DOI: 10.15227 / orgsyn.091.0185) 3. Corey-Winter elimination (DOI: 10.3762 / bjoc.14.41): → either via trimethoxyphosphite at 111°C → or via Corey-Hopkins reagent [1,3-dimethyl-2-phenyl-1,3,2-diazaphospholidine] at 40°C → or via potentiostatic electrolysis at -1.45 V vs. Ag / AgCl, 2.2 F / mol, RVC cathode, 1.5 h 4. Polymerization (Sohio process) List of reference symbols 100 Process for the production of acrylonitrile butadiene rubber 101 Submission of CO2 102 Conversion of CO2 to methylglyoxal 103 Conversion of methylglyoxal to acrylonitrile 104 Copolymerization of acrylonitrile with 1,3-butadiene to acrylonitrile-butadiene rubber QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2020 / 0347502 A1

[0007] Cited non-patent literature

[0000] Calvinho et al., Energy Environ. Sci., 2018, 11, 2550-2559

[0006] Lopez et al., Beilstein H. Org. Chem. 2018, 14, 547-552

[0008] Fujimoto et. al. Direct synthesis of propane / butane from synthesis gas. In: Studies in surface science and catalysis. Elsevier, 2007. pp. 349-354

[0009] Hua, Yani, et al. Electrochemical CO2 conversion towards syngas: Recent catalysts and improving strategies for ratio-tunable syngas. Journal of Power Sources, 2022, 535. Jg., S. 231453 [0010, 0054] Appl. Catal. A Geberal 2003, 246(1), 97-102

[0011]

Claims

[1] A process for producing acrylonitrile butadiene rubber comprising the steps of: - Providing CO2, - Conversion of CO2 to methylglyoxal, - converting methylglyoxal to acrylonitrile, and - Copolymerization of acrylonitrile with 1,3-butadiene to form acrylonitrile-butadiene rubber. [2] A process for producing acrylonitrile butadiene rubber according to claim 1, wherein the CO2 comes from the atmosphere. [3] A process for producing acrylonitrile-butadiene rubber according to one of claims 1 or 2, wherein the conversion of CO2 to methylglyoxal is carried out by means of catalysis. [4] A process for producing acrylonitrile-butadiene rubber according to any one of claims 1 to 3, wherein the conversion of methylglyoxal to acrylonitrile takes place via propene as an intermediate stage. [5] A process for producing acrylonitrile-butadiene rubber according to claim 4, further comprising the step of converting propene to acrylonitrile by catalysis. [6] A process for producing acrylonitrile-butadiene rubber according to any one of claims 1 to 5, further comprising the step of: - Conversion of carbon dioxide to 1,3-butadiene. [7] A process for producing acrylonitrile-butadiene rubber according to any one of claims 1 to 6, further comprising the step of: - Isolation of CO2 from the atmosphere. [8] Acrylonitrile-butadiene rubber produced by a process according to claims 1 to 7. [9] Use of acrylonitrile butadiene rubber according to claim 8 in the automotive industry. [10] Use of acrylonitrile butadiene rubber according to claim 8 in media-carrying lines, hydraulic hoses, seals, corrosion-reducing coatings for metal surfaces and dirt-trapping mats, pneumatic and hydraulic seals, O-rings, radial shaft seals, drive and spinning belts and technical rollers.

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