Ethylene glycol and polyester

Abstract

To provide ethylene glycol which is produced from carbon monoxide gas or carbon dioxide gas through microbial fermentation or reduction by an electrolytic cell and can reduce an environmental load, and to provide a polyester using the ethylene glycol.SOLUTION: The ethylene glycol of the present disclosure is characterized in that at least one gas selected from the group consisting of carbon monoxide and carbon dioxide is used as a raw material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to ethylene glycol and polyesters. [Background technology]

[0002] Ethylene glycol is widely used in various applications, such as as a raw material for polymers and as a moisturizing agent. Ethylene glycol is industrially produced from ethylene, which is obtained from petroleum, a fossil fuel. For example, ethylene oxide is produced from ethylene by the chlorohydrin method or a silver-catalyzed oxidation method, and then ethylene glycol is produced by hydrolyzing the ethylene oxide.

[0003] In recent years, with growing calls for the creation of a recycling-oriented society, there has been a desire to move away from fossil fuels in the materials sector, just as there is in energy, and the use of raw materials other than fossil fuels, such as biomass, is being considered. Biomass is a non-exhaustible resource, an industrial resource derived from the constituent substances of living organisms. The carbon contained in biomass comes from carbon dioxide absorbed from the atmosphere through photosynthesis during the growth process of living organisms. Therefore, even if carbon dioxide is emitted when biomass is burned, it is thought that the amount of carbon dioxide in the atmosphere does not increase overall. For this reason, biomass is attracting attention as a carbon-neutral renewable energy source. Recently, the practical application of ethylene glycol made from biomass has progressed rapidly, and attempts have been made to produce resins such as polyester from ethylene glycol made from biomass (biomass ethylene glycol) (for example, Patent Documents 1 and 2). By using biomass ethylene glycol instead of ethylene glycol produced from fossil fuel-derived raw materials, it becomes possible to reduce the amount of fossil fuel used and reduce the environmental burden.

[0004] Bioethanol, which is used to produce biomass ethylene glycol, can be produced by sugar fermentation from the molasses of sugarcane, a non-edible raw material. However, it is known from experience that the yield of crops such as sugarcane is greatly affected by weather factors. Therefore, there are concerns that climate change will make it difficult to stably procure sugarcane, the raw material for bioethanol. To address these concerns, organic compounds such as ethanol have been produced from resources that are neither fossil fuels nor biomass. For example, ethanol has been produced by microbial fermentation using carbon monoxide, which is present in exhaust gases emitted from steel mills and factories, as a raw material (see, for example, Patent Document 3). Carbon dioxide has also been reduced using an electrolytic cell to produce hydrocarbons such as ethane and ethylene (see, for example, Patent Document 4). Using these organic compounds instead of organic compounds produced using fossil fuel-derived raw materials can also reduce the amount of fossil fuel used and reduce the environmental impact. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2011-527348 [Patent Document 2] Special Publication No. 2012-519748 [Patent Document 3] Special Publication No. 2011-512869 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-112001 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present disclosure is to provide ethylene glycol, which can reduce the environmental impact, produced from carbon monoxide gas or carbon dioxide gas through microbial fermentation or reduction in an electrolytic cell. Another object of the present disclosure is to provide a polyester using the ethylene glycol. [Means for solving the problem]

[0007] The present inventors have discovered that ethylene glycol can be produced from ethanol produced by microbial fermentation using carbon monoxide gas as a raw material. The present inventors have also found that ethylene glycol can be produced by reducing carbon dioxide gas through electrolysis. The present disclosure has been completed based on these findings and through further investigation.

[0008] The present disclosure is solved by the following embodiments. <1> Ethylene glycol produced using at least one gas selected from the group consisting of carbon monoxide and carbon dioxide as a raw material. <2> The carbon dioxide molecule content is 2.2 x 10 18 pcs / g or more 1.5×10 19 pieces / g or less, <1> The ethylene glycol described in <3> The Kjeldahl nitrogen content is 700 μg / g or less. <1> or <2> The ethylene glycol described in <4> A polyester consisting of diol units and dicarboxylic acid units, The diol unit is <1> ~ <3> The polyester is an ethylene glycol according to any one of the above. <5> The dicarboxylic acid unit is at least one selected from the group consisting of terephthalic acid derived from a fossil fuel, terephthalic acid derived from biomass, and terephthalic acid derived from carbon dioxide gas. <4> The polyester according to claim 1. [Effects of the Invention]

[0009] The present disclosure can provide ethylene glycol that can reduce the environmental impact. The present disclosure can also provide a polyester using the ethylene glycol. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a reduction catalyst used in the production of ethylene glycol according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing in detail an example of the configuration of the reduction catalyst of FIG. 1. [Figure 3] FIG. 1 is a cross-sectional view showing the structure of a photochemical reaction cell used for producing ethylene glycol according to the present disclosure. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the operating principle of the photochemical reaction cell of FIG. [Figure 5] 4 is a cross-sectional view showing another example of the operating principle of the photochemical reaction cell of FIG. 3. FIG. [Figure 6] FIG. 1 is a perspective view showing the structure of a chemical reaction apparatus used for producing ethylene glycol according to the present disclosure. [Figure 7] FIG. 1 is a cross-sectional view showing the structure of a chemical reaction apparatus used for producing ethylene glycol according to the present disclosure. [Figure 8] FIG. 1 is a cross-sectional view showing another example of the structure of a chemical reaction apparatus used for producing ethylene glycol according to the present disclosure. [Figure 9] FIG. 1 is a cross-sectional view showing another example of the structure of a chemical reaction apparatus used for producing ethylene glycol according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Ethylene glycol] In this disclosure, "ethylene glycol" does not mean pure ethylene glycol as a compound (ethylene glycol represented by the chemical formula: HOCH2CH2OH), but rather means a composition containing impurities (contaminant components) that are inevitably contained in ethylene glycol produced through synthesis or purification.

[0012] The ethylene glycol according to the present disclosure is produced from at least one gas selected from the group consisting of carbon monoxide and carbon dioxide. By using the ethylene glycol according to the present disclosure instead of conventional ethylene glycol derived from fossil fuels, the amount of fossil fuel used can be reduced, thereby easing the environmental burden.

[0013] The Kjeldahl nitrogen content of the ethylene glycol according to the present disclosure tends to be lower than that of ethylene glycol derived from conventional fossil fuels. For example, the Kjeldahl nitrogen content of the ethylene glycol according to the present disclosure is preferably 700 μg / g or less, more preferably 560 μg / g or less, and even more preferably 330 μg / g or less. Furthermore, the Kjeldahl nitrogen content of the ethylene glycol according to the present disclosure is 0 μg / g or more, practically 10 μg / g or more, and more practically 30 μg / g or more. In the present disclosure, Kjeldahl nitrogen is nitrogen quantified in accordance with JIS K0102:2019 44.1 (Kjeldahl method) and 44.2 (indophenol blue absorptiometry). The specific method for measuring the Kjeldahl nitrogen content is measured by the method described in the Examples below.

[0014] Furthermore, the carbon dioxide molecule content in the ethylene glycol according to the present disclosure tends to be higher than that of conventional ethylene glycol derived from fossil fuels. For example, the carbon dioxide molecule content in the ethylene glycol according to the present disclosure is 2.2 × 10 18 It is preferable that the number of particles is 2.8×10 18 More preferably, it is 3.8 × 10 18 The carbon dioxide molecule content in the ethylene glycol of the present disclosure is more preferably 1.5×10 19 It is preferable that the number of particles is less than 1.2 × 10 19 It is more preferable that the number of particles is 1.0×10 19 It is more preferable that the number is not more than 1 / g. The content of carbon dioxide molecules in ethylene glycol is measured by thermal desorption mass spectrometry (TDS-MS), specifically by the method described in the Examples below.

[0015] Among the ethylene glycols disclosed herein, ethylene glycol made from carbon monoxide gas as a raw material can be produced from ethanol made from carbon monoxide gas as a raw material. Below, we will explain each of ethanol made from carbon monoxide gas as a raw material, ethylene glycol made from carbon monoxide gas as a raw material, and ethylene glycol made from carbon dioxide gas as a raw material.

[0016] [Ethanol made from carbon monoxide gas] Ethanol can be produced from carbon monoxide gas by microbial fermentation. Hereinafter, a method for producing ethanol from carbon monoxide gas by microbial fermentation will be described.

[0017] <Microbial fermentation> Microbial fermentation is carried out, for example, in a fermenter filled with a culture solution containing water and microorganisms. A feed gas containing carbon monoxide gas is supplied into the fermenter, and the carbon monoxide gas is converted into ethanol inside the fermenter. The feed gas may contain carbon dioxide, nitrogen, oxygen, etc. in addition to carbon monoxide.

[0018] The fermenter is preferably a continuous fermentation apparatus, and may be any of agitation type, airlift type, bubble column type, loop type, open bond type, and photobio type. The raw material gas and the culture solution may be continuously supplied to the fermenter, but it is not necessary to supply the raw material gas and the culture solution simultaneously, and the raw material gas may be supplied to a fermenter to which the culture solution has been previously supplied. The raw material gas is generally blown into the fermenter through a sparger or the like.

[0019] The culture medium is not particularly limited as long as it has an appropriate composition for culturing microorganisms, but is a liquid containing water as the main component and nutrients (e.g., vitamins, phosphoric acid, etc.) dissolved or dispersed in this water.

[0020] The temperature of the fermenter is preferably controlled to 40° C. or less. By controlling the temperature to 40° C. or less, the microorganisms in the fermenter do not die, and ethanol is efficiently produced by the raw material gas coming into contact with the microorganisms. The temperature of the fermenter is more preferably 38°C or lower, and in order to enhance the activity of the microorganisms, is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher.

[0021] The microorganism (species) that ferments the feed gas is not particularly limited as long as it can produce ethanol by microbial fermentation of the feed gas using carbon monoxide as the main feedstock. For example, the microorganism (species) is preferably one that produces ethanol from the feed gas through the fermentation action of gas-utilizing bacteria. Among gas-utilizing bacteria, the genus Clostridium is preferred, and Clostridium autoethanogenum is more preferred, from the viewpoints of gas utilization and culture stability. Examples are provided in more detail below.

[0022] Gas-utilizing bacteria include both eubacteria and archaebacteria. Examples of true bacteria include bacteria of the genus Clostridium, Moorella, Acetobacterium, Carboxydocella, Rhodopseudomonas, Eubacterium, Butyribacterium, Oligotropha, Bradyrhizobium, and the aerobic hydrogen-oxidizing bacteria Larsotonia.

[0023] On the other hand, examples of archaea include bacteria of the genus Methanobacterium, bacteria of the genus Methanobrevibacter, bacteria of the genus Methanocalculus, bacteria of the genus Methanococcus, bacteria of the genus Methanosarcina, bacteria of the genus Methanosphaera, bacteria of the genus Methanothermobacter, Metha Examples include bacteria of the genus Nothrix, bacteria of the genus Methanoculleus, bacteria of the genus Methanofollis, bacteria of the genus Methanogenium, bacteria of the genus Methanospirillium, bacteria of the genus Methanosaeta, bacteria of the genus Thermococcus, bacteria of the genus Thermofilum, bacteria of the genus Arcaheoglobus, and the like. Among these, as archaea, bacteria of the genus Methanosarcina, bacteria of the genus Methanococcus, bacteria of the genus Methanothermobacter, bacteria of the genus Methanothrix, bacteria of the genus Thermococcus, bacteria of the genus Thermofilum, and bacteria of the genus Archaeoglobus are preferred.

[0024] Furthermore, due to their excellent ability to assimilate carbon monoxide and carbon dioxide, archaea are preferably bacteria of the genus Methanosarcina, Methanothermobactor, or Methanococcus, with Methanosarcina or Methanococcus being particularly preferred. Specific examples of Methanosarcina bacteria include Methanosarcina barkeri, Methanosarcina mazei, and Methanosarcina acetivorans.

[0025] Among the gas-utilizing bacteria listed above, it is preferable to select and use bacteria with high ethanol production capacity, such as Clostridium autoethanogenum, Clostridium ljungdahlii, Clostridium aceticum, Clostridium carboxidivorans, Moorella thermoacetica, and Acetobacterium woodii.

[0026] Ethanol produced by microbial fermentation is obtained, for example, as an ethanol-containing liquid mixed with a culture solution. Ethanol can be separated from this ethanol-containing liquid using a separation device. Examples of separation devices include solid-liquid separators, distillation devices, and separation membranes, but it is preferable to use a solid-liquid separator and a distillation device in combination. Below, we will specifically explain the separation process performed using a solid-liquid separator and a distillation device in combination.

[0027] The ethanol-containing liquid obtained by microbial fermentation is separated in a solid-liquid separation device into a solid component mainly composed of microorganisms and a liquid component containing ethanol. The ethanol-containing liquid obtained by microbial fermentation contains, in addition to the target ethanol, microorganisms contained in the fermenter and their dead bodies as solid components, so solid-liquid separation is performed to remove these. Examples of solid-liquid separation devices include filters, centrifuges, and devices that use solution precipitation. The solid-liquid separation device may also be a device (e.g., a heat drying device) that evaporates the liquid component containing ethanol from the ethanol-containing liquid and separates it from the solid component. In this case, the liquid component containing the target ethanol may be entirely evaporated, or the liquid component may be partially evaporated so that the target ethanol is preferentially evaporated.

[0028] The liquid component separated by solid-liquid separation is further distilled in a distillation apparatus to separate the target product, ethanol. Separation by distillation allows for the production of large amounts of highly purified ethanol through simple operations. When distillation is performed, a known distillation apparatus such as a distillation column may be used. Furthermore, the distillation is performed, for example, so that the distillate contains the target product, ethanol, at a high purity, while the bottoms (i.e., the distillation residue) contains water as the main component (for example, 70% by mass or more, preferably 90% by mass or more). By performing the distillation in this manner, the target product, ethanol, and water can be largely separated.

[0029] The temperature inside the distillation apparatus during ethanol distillation is not particularly limited, but is preferably 100° C. or lower, more preferably 95° C. or lower, and preferably 70° C. or higher. By setting the temperature inside the distillation apparatus within the above range, ethanol can be reliably separated from other components such as water. The pressure inside the distillation apparatus during ethanol distillation may be normal pressure, but is preferably less than atmospheric pressure, more preferably 60 kPa or more and 150 kPa or less (gauge pressure). By setting the pressure inside the distillation apparatus within this range, the ethanol separation efficiency can be improved, and the ethanol yield can be increased.

[0030] [Ethylene glycol made from carbon monoxide gas] Ethylene glycol, which is produced from carbon monoxide gas as a raw material, can be produced from ethanol, which is also produced from carbon monoxide gas. For example, the ethanol obtained as described above is heated in the presence of a catalyst to produce ethylene through an intramolecular dehydration reaction. Next, ethylene is oxidized by a gas-phase catalytic reaction of ethylene using a silver catalyst to produce a gas containing ethylene oxide. It is known that the gas-phase catalytic reaction of ethylene produces not only ethylene oxide but also small amounts of organic acids such as formic acid and acetic acid, and aldehyde compounds such as formaldehyde and acetaldehyde as by-products. Therefore, the gas produced by the gas-phase catalytic reaction of ethylene contains organic acids and aldehyde compounds in addition to ethylene oxide. The produced gas is washed with water, and the ethylene oxide is absorbed in the water to separate the ethylene oxide from the produced gas. The resulting aqueous ethylene oxide solution is fed to a distillation column to strip the ethylene oxide, and a high-concentration aqueous ethylene oxide solution is recovered as the overhead distillate.

[0031] The high-concentration aqueous ethylene oxide solution is then sent to a reactor. The reaction to produce ethylene glycol from ethylene oxide is typically carried out at a reaction temperature of 150°C to 180°C and a reaction pressure of 2.5 MPa or less. The amount of water in the aqueous ethylene oxide solution is adjusted appropriately. It is generally preferable to use an ethylene oxide concentration of 9% by mass to 13% by mass. The water content of the produced aqueous ethylene glycol solution is removed in a dehydration tower or the like.

[0032] Next, vacuum distillation is carried out to separate ethylene glycol from diethylene glycol, triethylene glycol, etc., to obtain ethylene glycol from carbon monoxide gas as a raw material. A vacuum distillation column is used for vacuum distillation. The temperature during fractional distillation of ethylene glycol is preferably 125°C or higher, more preferably 135°C or higher, and preferably 225°C or lower, more preferably 195°C or lower. The pressure during fractional distillation of ethylene glycol is preferably 10 hPa or higher, more preferably 15 hPa or higher, and preferably 550 hPa or lower, more preferably 79 hPa or lower. Within the above temperature and pressure ranges, ethylene glycol can be efficiently purified by fractional distillation.

[0033] [Ethylene glycol made from carbon dioxide gas] Ethylene glycol can be obtained from carbon dioxide gas as a raw material by electrolysis using a chemical reaction device that uses a specific reduction catalyst. First, the reduction catalyst will be explained.

[0034] <Reduction catalyst> The reduction catalyst comprises a current collector having a metal layer on its surface, and an organic molecule bound to the surface of the metal layer and containing a quaternary nitrogen cation, represented by any one of the following general formulas I to V:

[0035] [ka] In the general formulas I to V, R1 is a primary, secondary, or tertiary amino group. R2 and R3 may be the same or different and each independently represent H or a primary, secondary, or tertiary amino group. p, q, r, and n each independently represent an integer of 1 to 12. Y is a reactive functional group, and X - indicates a counter anion.

[0036] A reduction catalyst according to a first embodiment will be described below with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing the configuration of the reduction catalyst 1, and FIG. 2 is a diagram showing an example of the configuration of the reduction catalyst 1 in detail. As shown in FIG. 1, the reduction catalyst 1 includes a current collector 101 and organic molecules 112 containing quaternary nitrogen cations. The current collector 101 has a metal layer 102 on its surface. The organic molecules 112 containing quaternary nitrogen cations are bonded to the metal layer 102 to form a monolayer (self-assembled monolayer: SAM). Hereinafter, the organic molecules containing quaternary nitrogen cations will be referred to as modified organic molecules.

[0037] The current collector 101 is made of an electrically conductive material and may be, for example, a stainless steel substrate.

[0038] The metal layer 102 on the surface of the current collector 101 contains at least one metal selected from the group consisting of Au, Ag, Cu, Zn, Pt, Fe, Ti, Ni, Sn, In, and Bi. The metal layer 102 may contain components other than metals, but is preferably made of metal only. The metal layer 102 and the current collector 101 may be made of the same material. In this case, the metal that makes up the metal layer 102 may also serve as the current collector 101.

[0039] The metal contained in the metal layer 102 functions as a catalyst that activates the reduction reaction. To improve catalytic activity, the metal contained in the metal layer 102 is preferably in the form of fine particles.

[0040] The average particle size of the metal particles contained in the metal layer 102 is preferably 1 nm or more and 300 nm or less. If the average particle size is 300 nm or less, the catalytic activity efficiency can be increased. Furthermore, it is difficult to manufacture metal particles with an average particle size of less than 1 nm. It is more preferable that the average particle size of the metal particles is 150 nm or less, as this further improves the catalytic activity efficiency. The metal particles may be primary particles with an average particle size of 50 nm or less, or may be secondary particles formed by agglomeration of such primary particles.

[0041] The modified organic molecule 112 has a skeleton 110 containing a quaternary nitrogen cation, a reactive functional group 109 located at one end, and an amino group 111 located at the other end. The quaternary nitrogen cation contained in the modified organic molecule 112 is at least one cation selected from an alkylammonium cation, a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, and an imidazolium cation. As described below, the quaternary nitrogen cation is preferably an imidazolium cation because of its high effect of improving reduction activity.

[0042] The skeleton 110 is composed of a quaternary nitrogen cation and an alkyl group that is a substituent of the cation. The number of carbon atoms in the alkyl group corresponds to p, q, r, and n in the general formulae I to V, and each is independently an integer of 1 to 12. In the general formulae I to V, when p, q, r, and n are 1 to 12, the distance between the quaternary nitrogen cation and the amino group, and between the quaternary nitrogen cation and the metal layer 102, is not too great, and as will be described later, the quaternary nitrogen cation can have the effect of improving the reduction efficiency. It is more preferable that p, q, r, and n are integers of 2 to 6.

[0043] The reactive functional group 109 corresponds to Y in the general formulae I to V. The reactive functional group 109 has affinity for the metal layer 102 and chemically bonds to the metal layer 102. This immobilizes the modified organic molecule 112 to the metal layer 102. The reactive functional group 109 is preferably a functional group capable of covalently bonding with the metal layer 102, and is preferably selected from, for example, a thiol group, a disulfide group, and a thiocyanate group. A thiol group is more preferable because of its excellent bonding strength.

[0044] The amino group 111 corresponds to R1 and optionally R2 and R3 in the general formulae I to V. The amino group 111 may be a primary, secondary, or tertiary amino group. When the amino group is a secondary or tertiary amino group, its substituents may be one or two C1-C 12 Preferably, the alkyl group is an alkyl group having the above carbon atoms. If the alkyl group has 12 or less carbon atoms, the distance between the quaternary nitrogen cation and the amino group is not too great, and as will be described later, the amino group can have the effect of improving reduction efficiency. More preferably, the alkyl group has 2 or more and 6 or less carbon atoms. The amino group 111 may form a salt with hydrofluoric acid, hydrochloric acid, hydrobromic acid, iodic acid, sulfuric acid, nitric acid, phosphoric acid, or the like.

[0045] The modified organic molecule 112 is represented by the general formulas I to V, where X - Specifically, it forms an ammonium salt, a piperidinium salt, a pyrrolidinium salt, a pyridinium salt, or an imidazolium salt. Note that the counter anion is omitted in Figure 1. In Figure 2, a bromide ion is shown as the counter anion.

[0046] Counter anions include, but are not limited to, fluoride, chloride, bromide, iodide, and HCO3 - , BF4 - , PF6 - , CF3COO - , CF3SO3 - , NO3 - , SCN - , N(CN)2 -, C(CN)3 - (CF3SO2)3C - , bis(trifluoromethoxysulfonyl)imide anion, bis(trifluoromethoxysulfonyl)imide anion, bis(perfluoroethylsulfonyl)imide anion, and the like.

[0047] Examples of the modified organic molecule 112 include the following molecules: 1-(2-mercaptoethyl)-3-aminomethylimidazolium bromide, 1-(3-mercaptopropyl)-3-aminomethylimidazolium bromide, 1-(4-mercaptobutyl)-3-aminomethylimidazolium bromide, 1-(5-mercaptopentyl)-3-aminomethylimidazolium bromide, 1-(6-mercaptohexyl)-3-aminomethylimidazolium bromide, imidazolium bromide, 1-(8-mercaptooctyl)-3-aminomethylimidazolium bromide, 1-(9-mercaptononyl)-3-aminomethylimidazolium bromide, 1-(10-mercaptodecyl)-3-aminomethylimidazolium bromide, 1-(11-mercaptoundecyl)-3-aminomethylimidazolium bromide, 1-(12-mercaptododecyl)-3-aminomethylimidazolium bromide, 1-(2-mercaptoethyl)-3-(2-aminoethyl)imidazolium bromide, 1-(2-mercaptoethyl)-3-(3-aminopropyl)imidazolium bromide, 1-(2-mercaptoethyl)-3-(4-aminobutyl)imidazolium bromide, 1-(2-mercaptoethyl)-3-(5-aminopentyl)imidazolium bromide, 1-(2-mercaptoethyl)-3-(6-aminohexyl)imidazolium bromide, 1-(2-mercaptoethyl)-3-(8-aminooctyl)imidazolium bromide, 1-(2-mercaptoethyl)-3-(9-aminononyl)imidazolium bromide imidazolium bromide, 1-(2-mercaptoethyl)-3-(10-aminodecyl)imidazolium bromide, 1-(2-mercaptoethyl)-3-(11-aminoundecyl)imidazolium bromide, 1-(2-mercaptoethyl)-3-(12-aminododecyl)imidazolium bromide, 1-(4-mercaptobutyl)-3-(2-methylaminoethyl)imidazolium bromide, 1-(6-mercaptohexyl)-3-(3-dimethylaminopropyl)imidazolium bromide, 1-(8-mercaptohexyl)-3-(4-ethylmethylaminobutyl)imidazolium bromide, 1-(2-mercaptoethyl)-4-aminomethylpyridinium bromide, 1-(3-mercaptopropyl)-4-aminomethylpyridinium bromide, 1-(4-mercaptobutyl)-4-aminomethylpyridinium bromide, 1-(5-mercaptopentyl)-4-aminomethylpyridinium bromide, 1-(6-mercaptohexyl)-4-aminomethylpyridinium bromide, 1-(8-mercaptooctyl)-4-aminomethylpyridinium bromide 1-(9-mercaptononyl)-4-aminomethylpyridinium bromide, 1-(10-mercaptodecyl)-4-aminomethylpyridinium bromide, 1-(11-mercaptoundecyl)-4-aminomethylpyridinium bromide, 1-(12-mercaptododecyl)-4-aminomethylpyridinium bromide, 1-(2-mercaptoethyl)-4-(2- 1-(2-mercaptoethyl)-4-(3-aminopropyl)pyridinium bromide, 1-(2-mercaptoethyl)-4-(4-aminobutyl)pyridinium bromide, 1-(2-mercaptoethyl)-4-(5-aminopentyl)pyridinium bromide, 1-(2-mercaptoethyl)-4-(6-aminohexyl)pyridinium bromide, 1-(2-mercaptoethyl)-4-(6-aminohexyl)pyridinium bromide 1-(2-mercaptoethyl)-4-(8-aminooctyl)pyridinium bromide, 1-(2-mercaptoethyl)-4-(9-aminononyl)pyridinium bromide, 1-(2-mercaptoethyl)-4-(10-aminodecyl)pyridinium bromide, 1-(2-mercaptoethyl)-4-(11-aminoundecyl)pyridinium bromide, 1-(2-mercaptoethyl)-4-(12-aminododecyl)pyridinium bromide, 1-(5-mercaptopentyl)-4-(3-methylaminopropyl)pyridinium bromide, 1-(9-mercaptononyl)-4-(4-dimethylaminobutyl)pyridinium bromide, 1-(11-mercaptoundecyl)-4-(6-ethylmethylaminohexyl)pyridinium bromide, 1-(2-mercaptoethyl)-1-aminomethylpyrrolidinium bromide, 1-(3-mercaptopropyl)-1-aminomethylpyrrolidinium bromide, 1-(4-mercaptobutyl)-1-aminomethylpyrrolidinium bromide, 1-(5-mercaptopentyl)-1-aminomethylpyrrolidinium bromide, 1-(6-mercaptohexyl)-1-aminomethylpyrrolidinium bromide, 1-(8-mercaptooctyl)-1-aminomethylpyrrolidinium bromide , 1-(9-mercaptononyl)-1-aminomethylpyrrolidinium bromide, 1-(10-mercaptodecyl)-1-aminomethylpyrrolidinium bromide, 1-(11-mercaptoundecyl)-1-aminomethylpyrrolidinium bromide, 1-(12-mercaptododecyl)-1-aminomethylpyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(2-aminoethyl)pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(3-aminopropyl)pyrrolidinium bromide )pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(4-aminobutyl)pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(6-aminohexyl)pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(8-aminooctyl)pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(9-aminononyl)pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(10-aminodecyl)pyrrolidinium bromide, 1- (2-mercaptoethyl)-1-(11-aminoundecyl)pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(12-aminododecyl)pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-(4-methylaminobutyl)pyrrolidinium bromide, 1-(3-mercaptopropyl)-1-(8-dimethylaminooctyl)pyrrolidinium bromide, 1-(4-mercaptobutyl)-1-(9-ethylmethylaminononyl)pyrrolidinium bromide, 1-(2-mercaptoethyl)-1-aminomethylpiperidinium bromide, 1-(3-mercaptopropyl)-1-aminomethylpiperidinium bromide, 1-(4-mercaptobutyl)-1-aminomethylpiperidinium bromide, 1-(5-mercaptopentyl)-1-aminomethylpiperidinium bromide, 1-(6-mercaptohexyl)-1-aminomethylpiperidinium bromide, 1-(8-mercaptooctyl)-1-aminomethylpiperidinium bromide, 1-(9-Mercaptononyl)-1-aminomethylpiperidinium bromide, 1-(10-mercaptodecyl)-1-aminomethylpiperidinium bromide, 1-(11-mercaptoundecyl)-1-aminomethylpiperidinium bromide, 1-(12-mercaptododecyl)-1-aminomethylpiperidinium bromide, 1-(2-mercaptoethyl)-1-(2-aminoethyl)piperidinium bromide, 1-(2-mercaptoethyl)-1-(3-aminopropyl)piperidine 1-(2-mercaptoethyl)-1-(4-aminobutyl)piperidinium bromide, 1-(2-mercaptoethyl)-1-(6-aminohexyl)piperidinium bromide, 1-(2-mercaptoethyl)-1-(8-aminooctyl)piperidinium bromide, 1-(2-mercaptoethyl)-1-(9-aminononyl)piperidinium bromide, 1-(2-mercaptoethyl)-1-(10-aminodecyl)piperidinium bromide, 1-(2-mercaptoethyl)-1-(10-aminodecyl)piperidinium bromide 1-(2-mercaptoethyl)-1-(11-aminoundecyl)piperidinium bromide, 1-(2-mercaptoethyl)-1-(12-aminododecyl)piperidinium bromide, 1-(10-mercaptodecyl)-1-(9-methylaminononyl)piperidinium bromide, 1-(11-mercaptoundecyl)-1-(10-dimethylaminodecyl)piperidinium bromide, 1-(12-mercaptododecyl)-1-(12-ethylmethylaminododecyl)piperidinium bromide, 2-mercaptoethyl-(aminomethyl)dimethylammonium bromide, 3-mercaptopropyl-(aminomethyl)dimethylammonium bromide, 4-mercaptobutyl-(aminomethyl)dimethylammonium bromide, 5-mercaptopentyl-(aminomethyl)dimethylammonium bromide, 6-mercaptohexyl-(aminomethyl)dimethylammonium bromide, 8-mercaptooctyl-(aminomethyl)dimethylammonium bromide, 9-mercaptononyl-(aminomethyl)dimethylammonium bromide, 10-mercaptodecyl-(aminomethyl)dimethylammonium bromide, 11-mercaptoundecyl-(aminomethyl)dimethylammonium bromide, 12-mercaptododecyl-(aminomethyl)dimethylammonium bromide, 2-mercaptoethyl-(3-aminopropyl)dimethylammonium bromide, 2-mercaptoethyl-(4-aminobutyl)dimethylammonium bromide, 2-mercaptoethyl-(5-aminopentyl)dimethylammonium bromide, 2-mercaptoethyl-(6-aminohexyl)dimethylammonium bromide, 2-mercaptoethyl-(8-aminooctyl)dimethylammonium bromide, 2-mercaptoethyl-(9-aminononyl)dimethylammonium bromide, 2-mercaptoethyl-(10-aminodecyl)dimethylammonium bromide, 2-mercaptoethyl-(11-aminoundecyl)dimethylammonium bromide, 2-mercaptoethyl-(12-aminododecyl)dimethylammonium bromide, 5-mercaptopentyl-(8-methylaminononyl)ethylmethylammonium bromide, 6-mercaptohexyl-(6-dimethylaminohexyl)methylpropylammonium bromide, and 8-mercaptooctyl-(4-ethylmethylaminobutyl)butylhexylammonium bromide.

[0048] Next, a method for producing the reduction catalyst 1 will be described. First, the metal layer 102 is formed on the surface of the current collector 101. As a method for this, a known vacuum film formation method such as a sputtering method, a vapor deposition method, or an ALD (Atomic Layer Deposition) method can be used.

[0049] Next, the reactive functional groups 109 are bonded to the metal layer 102, thereby immobilizing the modified organic molecules 112 on the metal layer 102. Known methods can be used for this. For example, a method of bringing the current collector 101 provided with the metal layer 102 into contact with a solution in which the modified organic molecules 112 are dissolved, a method of evaporating the modified organic molecules 112 in a high vacuum to form a film on the surface of the current collector 101, a method of spraying the modified organic molecules 112 onto the surface of the current collector 101 with a spray or the like can be used.

[0050] In the method using a solution in which the modified organic molecules 112 are dissolved, the modified organic molecules 112 chemically adsorbed to the metal layer 102 spontaneously form aggregates due to the van der Waals forces and hydrophobic interactions between the adsorbed molecules. The dense aggregation of the adsorbed molecules then forms a monolayer with uniform orientation.

[0051] Any solvent capable of dissolving organic molecules may be used as the solvent for dissolving the modified organic molecules 112. For example, the solvent may be selected from alcohols such as ethanol, and aromatic or aliphatic organic solvents such as toluene and hexane. Ethanol is preferred because it has high solubility for the modified organic molecules 112 and is easy to handle.

[0052] An example of a method for immobilizing the modified organic molecules 112 on the metal layer 102 will now be described in more detail. First, a preparation solution in which the modified organic molecules 112 are dissolved is prepared. Next, the current collector 101 on which the metal layer 102 has been formed is immersed in this preparation solution. The immersion time is from several minutes to several hours. This fixes the modified organic molecules 112 to the surface of the metal layer 102. Conditions such as the concentration of the modified organic molecules 112, the immersion time, and the immersion temperature can be appropriately changed depending on the structure of the modified organic molecules 112, etc. These conditions affect the state of formation of a monolayer made of the modified organic molecules 112.

[0053] If the concentration of the preparation solution is too low, it takes a long time to form a monolayer. On the other hand, if the concentration is too high, there is a risk that further molecules will be adsorbed onto the monolayer, forming a laminated film. For this reason, the concentration of the modified organic molecules 112 is preferably 0.1 mM or more and 100 mM or less, and more preferably 1 mM or more and 10 mM or less.

[0054] The immersion time is preferably sufficient to form a dense and uniformly oriented monolayer, and is preferably from 1 minute to 100 hours, and more preferably from 12 hours to 72 hours.

[0055] The temperature of the preparation solution during immersion affects the formation of a dense, uniformly oriented monolayer. Therefore, taking into consideration the vapor pressure and boiling point of the solvent, it is desirable to keep the temperature between room temperature (25°C) and 60°C.

[0056] The immobilization of the modified organic molecules 112 on the surface of the metal layer 102 can be confirmed by known electrochemical or surface analysis methods. Cyclic voltammetry can be used as an electrochemical method. A specific example is described below. First, a 0.2 M potassium chloride (KCl) aqueous solution containing 1 mM potassium hexacyanoferrate (III) (K3[Fe(CN)6]) or 1 mM hexaammineruthenium (III) chloride ([Ru(NH3)6]Cl3) is prepared. In this aqueous solution, the electrochemical response of the current collector 101 is measured before and after the process of adsorbing the modified organic molecules 112, and the results are compared.

[0057] As an electrochemical response, the reaction current due to the electrochemical redox reaction of hexacyanoiron(III) anions or hexaammineruthenium(III) cations is measured. The reaction current for the current collector 101 to which the modified organic molecules 112 are immobilized is reduced compared to the reaction current for the current collector 101 to which the modified organic molecules 112 are not immobilized. This is because the immobilization of the modified organic molecules 112 on the metal layer 102 inhibits the redox reaction of the hexacyanoiron(III) anions or hexaammineruthenium(III) cations. Thus, by measuring the reaction current, it is possible to indirectly confirm that the modified organic molecules 112 have been immobilized.

[0058] A Fourier transform infrared spectrophotometer (FT-IR) using the reflectance method can be used as a surface analysis method. This method allows for highly sensitive measurement of the infrared spectra of the thin film and molecular adsorbates on the surface of the current collector 101. This means that information on the structure of the organic molecules, particularly the functional groups, can be obtained. X-ray photoelectron spectroscopy (XPS) can also be used as a surface analysis method. This method allows for measurement of the modified organic molecules 112 and, if the modified organic molecules 112 have anions, the composition of the anions. Furthermore, a contact angle meter can be used to determine the presence or absence of the modified organic molecules 112 based on differences in water wettability.

[0059] Next, we will explain the reduction reaction of CO2 in reduction catalyst 1 using an example. In the elementary reaction of the CO2 reduction reaction, CO2 undergoes a one-electron reduction reaction to become a CO2 radical anion. This reaction requires a large overvoltage. This overvoltage results in energy loss and reduces the energy conversion efficiency. In addition, along with the CO2 reduction reaction, a reduction reaction of water and hydrogen ions occurs as a side reaction, generating hydrogen. This side reaction reduces the faradaic efficiency of the CO2 reduction reaction. However, reduction catalyst 1 is capable of achieving high reduction efficiency.

[0060] In the reduction catalyst 1, the quaternary nitrogen cation forms a reaction intermediate with CO2. This contributes to the generation and stabilization of CO2 radical anions. Therefore, the reduction catalyst 1 can initiate a CO2 reduction reaction with low energy. As a result, the energy conversion efficiency of the reduction catalyst can be improved. Furthermore, the quaternary nitrogen cation has the effect of inhibiting water and hydrogen ions from approaching the metal layer 102. Therefore, the quaternary nitrogen cation can impart reaction selectivity to the reduction reaction in the metal layer 102. In other words, it can suppress the generation of hydrogen due to side reactions and improve the faradaic efficiency.

[0061] Furthermore, the amino groups of the modified organic molecules 112 react with CO2 molecules to form carbonates. This allows them to attract the CO2 molecules necessary for the reduction reaction and supply them to the quaternary nitrogen cations and the metal layer 102. The amino groups also form salts with carboxylic acids (e.g., formic acid, acetic acid, oxalic acid, etc.) generated by CO2 reduction. This has the effect of promoting multi-electron reduction reactions in which reduction occurs continuously. As a result, it is possible to improve the reduction efficiency.

[0062] The reduction catalyst 1 can use carbon dioxide as the reduction raw material. The reduction products vary depending on the interaction between the quaternary nitrogen cation, the metal layer 102, and the reduction raw material. For example, when CO2 is used as the raw material, carbon monoxide (CO), formic acid (HCOOH), formaldehyde (HCHO), methanol (CH3OH), acetic acid (CH3COOH), acetaldehyde (CH3CHO), ethanol (CH3CH2OH), oxalic acid ((COOH)2), glycolic acid (C2H2O3), glycolaldehyde (C2H2O2), and ethylene glycol (HOCH2CH2OH) may be produced. However, the reduction catalyst 1 can produce ethylene glycol with high selectivity.

[0063] <Photochemical reaction cell> Next, the photochemical reaction cell provided in the chemical reaction device will be described with reference to FIGS.

[0064] The photochemical reaction cell includes an oxidation catalyst layer, a reduction catalyst layer containing a reduction catalyst, and a power supply element connected to the oxidation catalyst layer and the reduction catalyst layer. The power supply element preferably includes a semiconductor layer that separates charges using light energy, and a solar cell, for example, can be used. The semiconductor layer is preferably disposed between the oxidation catalyst layer and the reduction catalyst layer.

[0065] Fig. 3 is a cross-sectional view showing the structure of a photochemical reaction cell 30. As shown in Fig. 3, the photochemical reaction cell 30 is a laminate in which a reduction catalyst layer 20, a substrate 11, a reflective layer 12, a reduction electrode layer 13, a multi-junction solar cell 17, an oxidation electrode layer 18, and an oxidation catalyst layer 19 are laminated in this order. In the photochemical reaction cell 30, the side with the reduction catalyst layer 20 is the back surface, and the side with the oxidation catalyst layer 19 is the surface onto which light is incident.

[0066] The substrate 11 is provided to support the photochemical reaction cell and increase its mechanical strength. The substrate 11 is made of a conductive material. For example, it can be made of a metal plate made of a metal selected from the group consisting of Au, Ag, Cu, Pt, Zn, Fe, Ti, Sn, In, Bi, and Ni, or an alloy plate containing at least one of these metals. An alloy plate such as SUS can be used as the alloy plate. Alternatively, the substrate 11 can be made of a conductive resin or the like. The substrate 11 can also be made of a semiconductor substrate such as Si or Ge. The substrate 11 can also be made of an ion exchange membrane.

[0067] The reflective layer 12 is formed on the surface of the substrate 11. The reflective layer 12 is made of a material capable of reflecting light. For example, it can be made of a metal layer or a distributed Bragg reflector layer made of a semiconductor multilayer film. The reflective layer 12 is disposed between the substrate 11 and the multi-junction solar cell 17. Therefore, it can reflect light that is not absorbed in the multi-junction solar cell 17 and allow it to enter the multi-junction solar cell 17 again. This can improve the light absorption rate of the multi-junction solar cell 17.

[0068] The reduction electrode layer 13 is disposed on the reflective layer 12 and is sandwiched between the reflective layer 12 and an n-type semiconductor layer (an n-type amorphous silicon layer 14a described later) of the multi-junction solar cell 17. Therefore, the reduction electrode layer 13 is preferably made of a material capable of forming ohmic contact with the n-type semiconductor layer. The reduction electrode layer 13 is made of, for example, a metal such as Ag, Au, Al, or Cu, or an alloy containing at least one of these metals. Alternatively, the reduction electrode layer 13 is made of a transparent conductive oxide such as ITO (indium tin oxide), zinc oxide (ZnO), FTO (fluorine-doped tin oxide), AZO (aluminum-doped zinc oxide), or ATO (antimony-doped tin oxide). The reduction electrode layer 13 may also have, for example, a laminated structure of a metal and a transparent conductive oxide, a composite structure of a metal and another conductive material, or a composite structure of a transparent conductive oxide and another conductive material.

[0069] The multi-junction solar cell 17 is disposed on the reduction electrode layer 13. Starting from the reduction electrode layer 13, a first solar cell 14, a second solar cell 15, and a third solar cell 16 are stacked in this order. All of these solar cells use pin junction semiconductors. The first solar cell 14, the second solar cell 15, and the third solar cell 16 each have different light absorption wavelengths. By stacking these solar cells in a planar configuration, the multi-junction solar cell 17 can absorb sunlight over a wide range of wavelengths. This allows for more efficient use of solar energy. Furthermore, because the solar cells are connected in series, a high open-circuit voltage can be obtained.

[0070] The first solar cell 14 includes, in order from the reduction electrode layer 13 side, an n-type amorphous silicon (a-Si) layer 14a, an intrinsic amorphous silicon germanium (a-SiGe) layer 14b, and a p-type microcrystalline silicon (μc-Si) layer 14c. The a-SiGe layer 14b is a layer that absorbs light in the short wavelength region of about 400 nm. Therefore, in the first solar cell 14, charge separation occurs due to light energy in the short wavelength region.

[0071] The second solar cell 15 includes, in order from the reduction electrode layer 13 side, an n-type a-Si layer 15a, an intrinsic a-SiGe layer 15b, and a p-type μc-Si layer 15c. The a-SiGe layer 15b is a layer that absorbs light in the intermediate wavelength region of about 600 nm. Therefore, in the second solar cell 15, charge separation occurs due to light energy in the intermediate wavelength region.

[0072] The third solar cell 16 includes, in order from the reduction electrode layer 13 side, an n-type a-Si layer 16a, an intrinsic a-Si layer 16b, and a p-type μc-Si layer 16c. The a-Si layer 16b is a layer that absorbs light in the long wavelength region of about 700 nm. Therefore, in the third solar cell 16, charge separation occurs due to light energy in the long wavelength region.

[0073] Charge separation occurs in the multi-junction solar cell 17 due to light of each wavelength region. That is, holes are separated to the positive electrode side (front side) and electrons are separated to the negative electrode side (back side). This causes an electromotive force to be generated in the multi-junction solar cell 17.

[0074] While the multi-junction solar cell 17 constructed with a stacked structure of three solar cells has been described as an example, the present invention is not limited thereto, and a multi-junction solar cell constructed with a stacked structure of two or four or more solar cells may also be used. Alternatively, a single solar cell may be used instead of the multi-junction solar cell 17. Furthermore, while the solar cell using a pin junction semiconductor has been described, a solar cell using a pn junction semiconductor may also be used. Furthermore, a semiconductor layer made of, for example, GaAs, GaInP, AlGaInP, CdTe, CuInGaSe, or the like may also be used. Furthermore, various forms such as single crystal, polycrystalline, and amorphous may be used as the semiconductor layer.

[0075] The oxide electrode layer 18 is disposed on the multi-junction solar cell 17 and is sandwiched between the p-type semiconductor layer of the multi-junction solar cell 17 and the oxidation catalyst layer 19. The oxide electrode layer 18 is preferably made of a transparent material capable of making ohmic contact with the p-type semiconductor layer. The oxide electrode layer 18 is made of a transparent conductive oxide such as ITO (indium tin oxide), zinc oxide (ZnO), FTO (fluorine-doped tin oxide), AZO (aluminum-doped zinc oxide), or ATO (antimony-doped tin oxide). The oxide electrode layer 18 may also have a structure in which a metal and a transparent conductive oxide are stacked, a structure in which a metal and another conductive material are combined, or a structure in which a transparent conductive oxide and another conductive material are combined, for example.

[0076] The oxidation catalyst layer 19 is disposed on the positive electrode side of the multi-junction solar cell 17 and is formed on the oxidation electrode layer 18. When the pH of the electrolyte is lower than 7 (pH<7), the oxidation catalyst layer 19 oxidizes HO to O and H. + On the other hand, if the pH of the electrolyte is greater than 7 (pH>7), OH - to generate O and H. For this reason, the oxidation catalyst layer 19 is made of a material that reduces the activation energy for the oxidation reaction. - It is made of a material that reduces the overvoltage that occurs when the reaction involves oxidizing and extracting electrons.

[0077] Examples of such materials include binary metal oxides such as manganese oxide (Mn-O), iridium oxide (Ir-O), nickel oxide (Ni-O), cobalt oxide (Co-O), iron oxide (Fe-O), tin oxide (Sn-O), indium oxide (In-O), and ruthenium oxide (Ru-O); ternary metal oxides such as Ni-Co-O, La-Co-O, Ni-La-O, and Sr-Fe-O; quaternary metal oxides such as Pb-Ru-Ir-O and La-Sr-Co-O; and metal complexes such as Ru complexes and Fe complexes.

[0078] The form of the oxidation catalyst layer 19 is not limited to a thin film, but may be a lattice, particle, or wire shape.

[0079] In the photochemical reaction cell 30, irradiated light passes through the oxidation catalyst layer 19 and the oxidation electrode layer 18 to reach the multi-junction solar cell 17. Therefore, the oxidation electrode layer 18 and the oxidation catalyst layer 19 arranged on the light-irradiated side are optically transparent to the irradiated light. More specifically, the transmittance of the oxidation electrode layer 18 and the oxidation catalyst layer 19 on the irradiated side is at least 10% or more, and more preferably 30% or more, of the amount of irradiated light.

[0080] The reduction catalyst layer 20 is disposed on the negative electrode side of the multi-junction solar cell 17 and is formed on the back surface of the substrate 11. The reduction catalyst layer 20 reduces a reduction raw material such as CO2 to produce carbon compounds (e.g., carbon monoxide, formic acid, formaldehyde, methane, methanol, acetic acid, acetaldehyde, ethanol, ethylene glycol, etc.). For this reason, the reduction catalyst layer 20 is made of a material that reduces the activation energy required to reduce the reduction raw material.

[0081] The reduction catalyst 1 described above is applied as such a reduction catalyst layer 20. That is, the reduction catalyst layer 20 includes a current collector 101 and organic molecules 112 containing quaternary nitrogen cations. The current collector 101 may be used as a substrate 11.

[0082] A conductive protective layer may be disposed on the surface of the multi-junction solar cell 17 or between the electrode layer and catalyst layer on the light-irradiated side (between the oxidation electrode layer 18 and the oxidation catalyst layer 19 in the photochemical reaction cell 30). The protective layer prevents corrosion of the multi-junction solar cell 17 during oxidation-reduction reactions, thereby extending the life of the multi-junction solar cell 17. The protective layer may also be optically transparent, as required. Examples of the protective layer include thin dielectric films made of TiO2, ZrO2, Al2O3, SiO2, or HfO2. The thickness of the protective layer is preferably 10 nm or less, more preferably 5 nm or less, to achieve conductivity through the tunneling effect.

[0083] 4 and 5 are cross-sectional views for explaining the operating principle of the photochemical reaction cell 30. In these figures, the reflective layer 12, the reduction electrode layer 13, and the oxidation electrode layer 18 are omitted.

[0084] As shown in Figures 4 and 5, when light L is incident from the front side (the oxidation electrode layer 18 side), the incident light passes through the oxidation catalyst layer 19 (and the oxidation electrode layer 18) and reaches the multi-junction solar cell 17. When the multi-junction solar cell 17 absorbs light, photoexcited electrons and their corresponding holes are generated, and then they are separated. Specifically, in each solar cell (the first solar cell 14, the second solar cell 15, and the third solar cell 16), the photoexcited electrons move to the n-type semiconductor layer side (the reduction catalyst layer 20 side), and the holes generated as pairs of the photoexcited electrons move to the p-type semiconductor layer side (the oxidation catalyst layer 19 side). In other words, charge separation occurs. This causes an electromotive force to be generated in the multi-junction solar cell 17.

[0085] Photoexcited electrons generated in the multi-junction solar cell 17 are used in a reduction reaction in the reduction catalyst layer 20, which is the negative electrode, and holes are used in an oxidation reaction in the oxidation catalyst layer 19, which is the positive electrode.

[0086] An example in which the electrolyte is an acidic solution with a pH of less than 7 is shown in FIG. 4. In the vicinity of the oxidation catalyst layer 19, the reaction of the following formula (1) occurs. That is, H2O is oxidized to O2 and H + and electrons are generated. + moves to the reduction catalyst layer 20 side through an ion migration path, which will be described later. In the vicinity of the reduction catalyst layer 20, the reaction of the following formula (2) occurs. That is, CO2 reacts with the H + and electrons to produce carbon monoxide (CO) and H2O. 2H2O → 4H + +O2+4e - ···(1) 2CO2+4H + +4e - → 2CO+2H2O (2) On the other hand, an example in which the electrolyte is a basic solution with a pH greater than 7 is shown in FIG. 5. In the vicinity of the oxidation catalyst layer 19, the reaction of the following formula (3) occurs: OH -is oxidized to generate O2, H2O, and electrons. In the vicinity of the reduction catalyst layer 20, the reaction of the following formula (4) occurs. That is, CO2 undergoes a reduction reaction in which it receives electrons together with H2O, and carbon monoxide (CO) and OH - The OH generated on the reduction catalyst layer 20 side is - moves to the oxidation catalyst layer 19 side via an ion migration path that will be described later. 4OH - → O2 + 2H2O + 4e - ···(3) 2CO2+2H2O+4e - → 2CO+4OH - ···(4) The multi-junction solar cell 17 must have an open-circuit voltage equal to or greater than the potential difference between the standard redox potential of the oxidation reaction occurring in the oxidation catalyst layer 19 and the standard redox potential of the reduction reaction occurring in the reduction catalyst layer 20. For example, when the pH of the reaction solution is 0, the standard redox potential of the oxidation reaction in equation (1) is +1.23 [V], and the standard redox potential of the reduction reaction in equation (2) is -0.1 [V]. Therefore, the open-circuit voltage of the multi-junction solar cell 17 must be 1.33 [V] or greater.

[0087] More preferably, the open-circuit voltage needs to be equal to or greater than the potential difference including the overvoltage. More specifically, for example, when the overvoltages of the oxidation reaction in formula (1) and the reduction reaction in formula (2) are each 0.2 [V], the open-circuit voltage is preferably 1.73 [V] or greater.

[0088] The reduction reactions in the above formulas (2) and (4) show the reduction reaction from CO2 to CO, but are not limited to this, and reduction reactions from CO2 to HCOOH, HCHO, CH4, CH3OH, C2H5OH, HOCH2CH2OH, etc. may also occur. + Consume or OH - Therefore, H generated in the oxidation catalyst layer 19 + When the OH produced in the reduction catalyst layer 20 cannot move to the reduction catalyst layer 20 of the counter electrode, -When H cannot move to the oxidation catalyst layer 19 of the counter electrode, the overall reaction efficiency decreases. + Or OH - By providing an ion transfer path for the transfer of H + Or OH - Therefore, high photoreaction efficiency can be achieved.

[0089] <Chemical reactor> Next, a chemical reaction device using the above-mentioned photochemical reaction cell will be described with reference to Figures 6 to 9. Here, the oxidation-reduction reaction (the above formulas (1) and (2)) in the case of an acidic solution in which the electrolyte has a pH of less than 7 will be described as an example. In the case of a basic solution in which the electrolyte has a pH of more than 7, the oxidation-reduction reaction according to the above formulas (3) and (4) occurs.

[0090] FIG. 6 is a perspective view showing the structure of a chemical reaction device 200 according to this embodiment. FIG. 7 is a cross-sectional view showing the structure of the chemical reaction device 200. The chemical reaction device 200 comprises a photochemical reaction cell 30, an electrolytic cell 31 that houses the photochemical reaction cell, and an electrolytic cell flow path 41 that is connected to the electrolytic cell 31 as an ion migration path. Note that the ion migration path is omitted in FIG. 6. As described above, the photochemical reaction cell 30 comprises a stack of an oxidation catalyst layer 19, a reduction catalyst layer 20, a multi-junction solar cell 17 formed therebetween, and a substrate 11.

[0091] The electrolytic bath 31 includes an oxidation reaction electrolytic bath 31a in which an oxidation catalyst layer 19 is disposed, and a reduction reaction electrolytic bath 31b in which a reduction catalyst layer 20 is disposed. In the oxidation reaction electrolytic bath 31a, H2O is oxidized by the oxidation catalyst layer 19 to produce O2 and H +is produced. In the reduction reaction electrolytic cell 31b, CO2 is reduced by the reduction catalyst layer 20 to produce CO and HO. These two electrolytic cells are separated into two by the substrate 11 of the photochemical reaction cell 30. In this example, the end of the substrate 11 protrudes beyond the ends of the multi-junction solar cell 17, the oxidation catalyst layer 19, and the reduction catalyst layer 20, but this is not limiting, and the substrate 11, the multi-junction solar cell 17, the oxidation catalyst layer 19, and the reduction catalyst layer 20 may be flat plates with the same area.

[0092] Separate electrolytes can be supplied to the oxidation reaction electrolytic bath 31a and the reduction reaction electrolytic bath 31b. An electrolytic bath flow path 41, which allows ions to move, connects the oxidation reaction electrolytic bath 31a and the reduction reaction electrolytic bath 31b.

[0093] In this way, with the configuration including the electrolytic cell flow path 41, H generated on the oxidation catalyst layer 19 side + can be transferred to the reduction catalyst layer 20, and this H + This allows carbon dioxide to be decomposed on the reduction catalyst layer 20 side, thereby achieving high photoreaction efficiency.

[0094] The electrolytic cell flow path 41 will be described in more detail. The electrolytic cell flow path 41 is provided, for example, on the side of the electrolytic cell 31. One end of the electrolytic cell flow path 41 is connected to the electrolytic cell 31a for the oxidation reaction, and the other end is connected to the electrolytic cell 31b for the reduction reaction. In other words, the electrolytic cell flow path 41 connects the electrolytic cell 31a for the oxidation reaction and the electrolytic cell 31b for the reduction reaction. This allows ions to move between the oxidation catalyst layer 19 and the reduction catalyst layer 20.

[0095] An ion exchange membrane 43 is filled in a portion of the electrolytic cell flow path 41, and only specific ions are allowed to pass through the ion exchange membrane 43. This allows only specific ions to move between the electrolytic cell 31a for oxidation reaction and the electrolytic cell 31b for reduction reaction while separating the electrolyte.

[0096] The ion exchange membrane 43 is a proton exchange membrane, and is used to exchange H generated in the oxidation reaction electrolytic cell 31a. +can be moved to the reduction reaction electrolytic cell 31b side. Examples of the proton exchange membrane include a cation exchange membrane such as Nafion or Flemion, and an anion exchange membrane such as Neosepta or Selemion.

[0097] Instead of the ion exchange membrane 43, a material such as agar that allows ions to move and separates the electrolyte may be used. For example, a salt bridge may be used. In general, the use of a proton-exchange solid polymer membrane, such as Nafion, can improve ion migration performance.

[0098] Furthermore, a circulation mechanism 42 such as a pump may be provided in the electrolytic cell flow path 41. By promoting the circulation of the electrolyte by the circulation mechanism 42, ions (H + ) can be improved. Alternatively, two electrolytic cell flow paths 41 may be provided, and a circulation mechanism 42 provided in at least one of them may be used to move ions from the electrolytic cell 31a for the oxidation reaction to the electrolytic cell 31b for the reduction reaction via one electrolytic cell flow path 41, and from the electrolytic cell 31b for the reduction reaction to the electrolytic cell 31a for the oxidation reaction via the other electrolytic cell flow path 41. Alternatively, multiple circulation mechanisms 42 may be provided. Alternatively, multiple (three or more) electrolytic cell flow paths 41 may be provided to reduce ion diffusion and circulate ions more efficiently.

[0099] By creating a liquid flow using the circulation mechanism 42, it is possible to prevent the generated gas bubbles from remaining on the electrode surface or the surface of the electrolytic cell, thereby suppressing the decrease in efficiency and light intensity distribution caused by the scattering of sunlight by the bubbles.

[0100] Furthermore, light irradiation can generate heat on the surface of the multi-junction solar cell 17. This heat can generate a temperature difference in the electrolyte, which can be used to generate convection and circulate ions more efficiently. In this case, ion migration can be promoted more than ion diffusion.

[0101] A temperature adjustment mechanism 44 for adjusting the temperature of the electrolyte may be provided in the electrolytic cell flow path 41 or the electrolytic cell 31. By controlling the temperature using the temperature adjustment mechanism 44, it is possible to control the solar cell performance and catalyst performance. For example, by making the temperature of the reaction system uniform, it is possible to stabilize and improve the performance of the solar cell and catalyst. It is also possible to prevent temperature rise for the sake of system stability. Temperature control can change the selectivity of the solar cell and catalyst, and also control the products produced.

[0102] The oxidation reaction electrolytic bath 31a is filled with an electrolytic solution containing an arbitrary electrolyte. The oxidation catalyst layer 19 is immersed in this electrolytic solution. The electrolytic solution is preferably one that promotes the oxidation reaction of HO. For example, a liquid containing HO is used.

[0103] The reduction reaction electrolytic cell 31b is filled with an arbitrary electrolyte. The reduction catalyst layer 20 is immersed in this electrolyte. The electrolyte preferably contains a CO2 absorbent that lowers the reduction potential of CO2, has high ionic conductivity, and absorbs CO2. For example, a liquid containing CO2 is used.

[0104] An example of the electrolyte filling the reduction reaction electrolytic cell 31b is a solution containing a cation such as an imidazolium ion or a pyridinium ion and BF4 - or PF6 -Examples of the amine include ionic liquids or aqueous solutions thereof, which are composed of salts with anions such as methylamine, imidazole, or pyridine and remain in a liquid state over a wide temperature range. Furthermore, examples of the amine include solutions of amines such as ethanolamine, imidazole, or pyridine, or aqueous solutions thereof. The amine may be a primary amine, secondary amine, or tertiary amine. Examples of primary amines include methylamine, ethylamine, propylamine, butylamine, pentylamine, and hexylamine. In any of the primary amines, secondary amines, and tertiary amines, the hydrocarbon group substituting the amine may be an alcohol group or may be substituted with a halogen. Examples of these include methanolamine, ethanolamine, and chloromethylamine. The hydrocarbon group substituting the amine may have an unsaturated bond.

[0105] Examples of secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dimethanolamine, diethanolamine, dipropanolamine, methylethylamine, and methylpropylamine.

[0106] Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trimethanolamine, triethanolamine, tripropanolamine, tributanolamine, tripropanolamine, trihexanolamine, methyldiethylamine, and methyldipropylamine.

[0107] Ions such as imidazolium ions and pyridinium ions can be used as cations in ionic liquids. Examples of imidazolium ions include 1-ethyl-3-methylimidazolium ion, 1-methyl-3-propylimidazolium ion, 1-butyl-3-methylimidazole ion, 1-methyl-3-pentylimidazolium ion, and 1-hexyl-3-methylimidazolium ion. These imidazolium ions may be substituted at the 2-position, and examples thereof include 1-ethyl-2,3-dimethylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1-butyl-2,3-dimethylimidazolium ion, 1,2-dimethyl-3-pentylimidazolium ion, and 1-hexyl-2,3-dimethylimidazolium ion. Examples of pyridinium ions include methylpyridinium, ethylpyridinium, propylpyridinium, butylpyridinium, pentylpyridinium, and hexylpyridinium, etc. In both imidazolium ions and pyridinium ions, the alkyl group may be substituted, and an unsaturated bond may be present.

[0108] The anions of ionic liquids include fluoride ions, chloride ions, bromide ions, iodide ions, and BF4 - , PF6 - , CF3COO - , CF3SO3 - , NO3 - , SCN - , (CF3SO2)3C - , bis(trifluoromethoxysulfonyl)imide, bis(trifluoromethoxysulfonyl)imide, bis(perfluoroethylsulfonyl)imide, etc. Also usable are zwitterions in which the cation and anion of an ionic liquid are linked by a hydrocarbon.

[0109] The temperatures of the electrolytic solution filling the oxidation reaction electrolytic bath 31a and the electrolytic solution filling the reduction reaction electrolytic bath 31b may be the same or different depending on the environment in which they are used. For example, an amine absorption solution containing CO2 discharged from a factory may be used as the electrolytic solution used in the reduction reaction electrolytic bath 31b. In this case, the temperature of the electrolytic solution is higher than the atmospheric temperature, for example, from 30°C to 150°C, more specifically from 40°C to 120°C.

[0110] The reduction catalyst 1 in the first embodiment is used as the reduction catalyst layer 20. A reduction potential is applied to the metal layer 102 of the reduction catalyst. As a result, ions containing CO2 (e.g., bicarbonate ions) among the electrolyte components or physically dissolved CO2 are subjected to electrostatic attraction in the vicinity of the metal layer 102 and the quaternary nitrogen cations contained in the modified organic molecules 112 fixed to its surface. As a result, an electric double layer is formed at the catalyst / electrolyte interface by the CO2, the metal layer 102, and the quaternary nitrogen cations.

[0111] At this interface, a CO2 reduction reaction due to a charge transfer reaction proceeds. In the reduction reaction electrolytic cell 31b, CO2 is reduced by the reduction catalyst layer 20 to produce carbon compounds. Specifically, CO2 is converted into carbon monoxide (CO), formic acid (HCOOH), formaldehyde (HCHO), methanol (CH3OH), acetic acid (CH3COOH), acetaldehyde (CH3CHO), ethanol (CH3CH2OH), and ethylene glycol (HOCH2CH2OH). In addition, as a side reaction, water (HO) may be reduced to produce hydrogen (H2).

[0112] When carbon dioxide undergoes a two-electron reduction reaction, formic acid is produced in addition to carbon monoxide. When formic acid undergoes a two-electron reduction reaction, formaldehyde is produced. Furthermore, when formaldehyde undergoes a two-electron reduction reaction, methanol is produced. When methanol is produced using the reduction catalyst 1, formic acid or formaldehyde may be selected as the reduction raw material in addition to carbon dioxide. Therefore, it is desirable that the electrolyte in the reduction reaction electrolytic cell 31b has absorbed therein at least one reduction raw material selected from carbon dioxide, formic acid, and formaldehyde. For example, the electrolyte in the reduction reaction electrolytic cell 31b may be a sodium bicarbonate solution.

[0113] Furthermore, when carbon dioxide undergoes a two-electron reduction reaction, oxalic acid may be produced. When oxalic acid undergoes a two-electron reduction reaction, glycolic acid is produced. When glycolic acid undergoes a two-electron reduction reaction, glyoxal or glycolic acid is produced. When glyoxal or glycolic acid undergoes a two-electron reduction reaction, glycolaldehyde is produced. When glycolaldehyde undergoes a two-electron reduction reaction, ethylene glycol is produced. When ethylene glycol is produced using the reduction catalyst 1, oxalic acid, glycolic acid, or glycolaldehyde may be selected as the reduction raw material in addition to carbon dioxide. Therefore, the electrolyte in the reduction reaction electrolytic cell 31b may have absorbed therein at least one reduction raw material selected from oxalic acid, glycolic acid, or glycolaldehyde.

[0114] When carbon dioxide undergoes an eight-electron reduction reaction, acetic acid may be produced. When acetic acid undergoes an eight-electron reduction reaction, acetaldehyde is produced. Furthermore, when acetaldehyde undergoes an eight-electron reduction reaction, ethanol is produced. When ethanol is produced using the reduction catalyst 1, acetic acid or acetaldehyde may be selected as the reduction raw material in addition to carbon dioxide. Therefore, the electrolyte in the reduction reaction electrolytic cell 31b may have absorbed therein at least one reduction raw material selected from carbon dioxide, acetic acid, and acetaldehyde.

[0115] As described above, the reaction in which carbon dioxide is reduced to produce formic acid, formaldehyde, and methanol, the reaction in which carbon dioxide is reduced to produce oxalic acid, glycolic acid, glyoxal or glycolic acid, glycolaldehyde, and ethylene glycol, and the reaction in which carbon dioxide is reduced to produce acetic acid, acetaldehyde, and ethanol depend on the density of the modified organic molecules 112 in the reduction catalyst 1. For example, when the density of the modified organic molecules 112 relative to the metal layer 102 is 1×10 11 atoms / cm 2 In the following cases, a reaction occurs in which formic acid, formaldehyde, and methanol are mainly produced. On the other hand, when the density of the modified organic molecules 112 is 1×10 12 atoms / cm 2 Over 10 15 atoms / cm 2 In the following case, a reaction occurs in which acetic acid, acetaldehyde, and ethanol are produced in addition to formic acid, formaldehyde, and methanol. In particular, when the density of the modified organic molecule 112 is 1×10 13 atoms / cm 2 Over 10 15 atoms / cm 2 In the following cases, reactions occur that produce mainly acetic acid, acetaldehyde, and ethanol.

[0116] The bonding state and molecular density of the modified organic molecules 112 can be calculated based on the analysis results of X-ray photoelectron spectroscopy (XPS). The analysis conditions can be as follows: The detection angle refers to the angle between the normal to the sample and the axis of the detector input lens. Model used: PHI Quantera-SXM Irradiation X-ray source Single crystal spectroscopic AlKα ray Output: 50W Analysis area φ200μm Pass Energy Wide Scan-280.0eV (1.0eV / Step) Narrow Scan-69.0eV(0.125eV / Step) Detection angle 45° Charge neutralization electron gun Ar +,e - Used together As a charge correction (horizontal axis energy correction), the C—C / H bond component of the C1s spectrum is adjusted to 284.80 eV.

[0117] The bond density (molecular density) of the modified organic molecules 112 is calculated by the following formula (6) using the number of Au atoms per unit area estimated by the following formula (5) and the number of S atoms (S / Au) normalized by the number of Au atoms from the semi-quantitative analysis results.

[0118] Au(atoms / cm 2 ) =density(g / cm 3 ) × detection depth (nm) × N / Mw (5) Molecular density (atoms / cm 2 ) = Au(atoms / cm 2 ) × S / Au (atomic ratio) (6) Here, the density is 19.3 g / cm 3 , the detection depth is 5 nm, N is Avogadro's number (atoms / mol), and Mw is 197 g / mol.

[0119] The reduction catalyst 1 selectively reduces carbon dioxide to ethylene glycol via oxalic acid, glycolic acid, or glycolaldehyde by maintaining the electrode at a reduction potential. This reaction, in other words, allows the modified organic molecules 112 to be uniformly oriented, resulting in the reaction of ethylene glycol. The electrolysis conditions for maintaining the electrode at a reduction potential are as follows: a three-electrode cell is used, with the electrode substrate as the working electrode, silver / silver chloride as the reference electrode, and platinum as the counter electrode. A potential of −0.8 V to −1.3 V is applied to the working electrode for at least 5 hours, preferably for at least 3 hours, and more preferably for at least 1 hour. The orientation of the modified organic molecules 112 can be observed using a scanning tunneling microscope (STM).

[0120] Next, modified examples of the chemical reaction device according to this embodiment will be described. Fig. 8 is a cross-sectional view showing the structure of a chemical reaction device 210. Fig. 9 is a cross-sectional view showing the structure of a chemical reaction device 220. Below, structures different from the above-described chemical reaction device 200 will be described.

[0121] As shown in FIG. 8, the chemical reaction device 210 includes a photochemical reaction cell 30, an electrolytic cell 31 containing the photochemical reaction cell 30, and an opening 51 formed in the substrate 11 as an ion migration path.

[0122] The opening 51 is provided so as to penetrate the end of the substrate 11 from the electrolytic bath 31a for oxidation reaction to the electrolytic bath 31b for reduction reaction. An ion exchange membrane 43 is filled in a part of the opening 51, and the electrolytic bath 31a for oxidation reaction and the electrolytic bath 31b for reduction reaction are separated by the substrate 11 and the ion exchange membrane 43. The ion exchange membrane 43 allows only specific ions to pass through.

[0123] With this configuration, only specific ions can be transferred through the ion exchange membrane 43 while the electrolyte is separated between the oxidation reaction electrolytic bath 31a and the reduction reaction electrolytic bath 31b.

[0124] 9, the chemical reaction device 220 includes a photochemical reaction cell 30, an electrolytic cell 31 containing the photochemical reaction cell 30, and an opening 52 formed as an ion migration path. The opening 52 is provided so as to penetrate the reduction catalyst layer 20, the substrate 11, the multi-junction solar cell 17, and the oxidation catalyst layer 19 from the oxidation reaction electrolytic cell 31a side to the reduction reaction electrolytic cell 31b side.

[0125] An ion exchange membrane 43 is filled in a part of the opening 52, and the electrolytic bath 31a for the oxidation reaction and the electrolytic bath 31b for the reduction reaction are separated by the substrate 11 and the ion exchange membrane 43. The ion exchange membrane 43 allows only specific ions to pass through.

[0126] With this configuration, only specific ions can be transferred through the ion exchange membrane 43 while the electrolyte is separated between the oxidation reaction electrolytic bath 31a and the reduction reaction electrolytic bath 31b.

[0127] In the chemical reaction device 220 of FIG. 9, the ion exchange membrane 43 is installed only in a part of the opening 52, but the ion exchange membrane 43 may be installed over the entire opening 52.

[0128] [Uses of ethylene glycol] The ethylene glycol according to the present disclosure can be used as a solvent or antifreeze, and can also be used as a raw material for producing ethylene glycol compound derivatives or polyesters. Hereinafter, polyester will be described as an example of the use of ethylene glycol according to the present disclosure.

[0129] [polyester] The polyester according to the present disclosure is composed of diol units and dicarboxylic acid units, and is obtained by a polycondensation reaction using ethylene glycol according to the present disclosure as the diol units and dicarboxylic acid as the dicarboxylic acid units. That is, in the polyester according to the present disclosure, the diol units are ethylene glycol produced from at least one gas selected from the group consisting of carbon monoxide and carbon dioxide.

[0130] The dicarboxylic acid unit of the polyester according to the present disclosure may be, for example, a dicarboxylic acid derived from a fossil fuel, and the fossil fuel-derived dicarboxylic acid may include, without limitation, an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or a derivative thereof. Examples of aromatic dicarboxylic acids include terephthalic acid and isophthalic acid, and examples of derivatives of aromatic dicarboxylic acids include lower alkyl esters of aromatic dicarboxylic acids, specifically methyl esters, ethyl esters, propyl esters, butyl esters, etc. Among these, terephthalic acid is preferred, and dimethyl terephthalate is preferred as a derivative of aromatic dicarboxylic acid. Specific examples of aliphatic dicarboxylic acids include linear or alicyclic dicarboxylic acids typically having 2 to 40 carbon atoms, such as oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, and cyclohexanedicarboxylic acid. Derivatives of aliphatic dicarboxylic acids include lower alkyl esters of the above aliphatic dicarboxylic acids, such as methyl esters, ethyl esters, propyl esters, and butyl esters, as well as cyclic acid anhydrides of the above aliphatic dicarboxylic acids, such as succinic anhydride. Among these, adipic acid, succinic acid, dimer acid, or a mixture thereof is preferred, with those containing succinic acid as the main component being particularly preferred. More preferred derivatives of aliphatic dicarboxylic acids include methyl esters of adipic acid and succinic acid, or a mixture thereof.

[0131] Furthermore, the dicarboxylic acid used in the dicarboxylic acid unit may be a dicarboxylic acid derived from biomass. Examples of biomass-derived dicarboxylic acids that can be used include aliphatic dicarboxylic acids obtained from plant materials such as renewable plant-derived oils such as soybean oil, linseed oil, tung oil, coconut oil, palm oil, and castor oil, as well as regenerated oils obtained by recycling waste cooking oils containing these oils as a main component. Examples of biomass-derived aliphatic dicarboxylic acids include sebacic acid, succinic acid, phthalic acid, adipic acid, glutaric acid, and dimer acid. For example, sebacic acid is produced by alkaline pyrolysis of ricinoleic acid obtained from castor oil, with heptyl alcohol as a by-product. Furthermore, biomass-derived aromatic dicarboxylic acids can be produced by, for example, producing isobutanol from corn, sugars, or wood, converting the isobutanol into isobutylene, dimerizing the isobutane to produce isooctene, synthesizing p-xylene through radical cleavage, recombination, and cyclization, and then oxidizing the resulting p-xylene (WO 2009 / 079213). When a biomass-derived dicarboxylic acid is used as the dicarboxylic acid unit, in the present disclosure, it is particularly preferable to use biomass-derived terephthalic acid.

[0132] The dicarboxylic acid used for the dicarboxylic acid unit may be a dicarboxylic acid produced from carbon dioxide gas. Terephthalic acid produced from carbon dioxide gas as a raw material can be used as a dicarboxylic acid produced from carbon dioxide gas. Terephthalic acid produced from carbon dioxide gas as a raw material can be produced, for example, by producing p-xylene from carbon dioxide gas and hydrogen gas as raw materials using a composite catalyst containing chromium oxide and a specific H-ZSM-5 zeolite, and then oxidizing the p-xylene (Japanese Patent Laid-Open Publication No. 2019-205969).

[0133] These dicarboxylic acids can be used alone or in combination of two or more.

[0134] The polyester may be a copolymerized polyester containing the diol unit and dicarboxylic acid unit, as well as a third copolymerization component. Specific examples of the copolymerization component include a bifunctional oxycarboxylic acid, and at least one polyfunctional compound selected from the group consisting of a trifunctional or higher polyhydric alcohol, a trifunctional or higher polycarboxylic acid and / or its anhydride, and a trifunctional or higher oxycarboxylic acid for forming a crosslinked structure. Among these copolymerization components, bifunctional and / or trifunctional or higher oxycarboxylic acids are particularly preferred because they tend to facilitate the production of copolymerized polyesters with a high degree of polymerization. Among these, the use of trifunctional or higher oxycarboxylic acids is most preferred because a very small amount of the oxycarboxylic acid can easily produce a polyester with a high degree of polymerization without the need for a chain extender, as described below.

[0135] The polyester may also be a high-molecular-weight polyester obtained by chain-extending (coupling) these copolymer polyesters. Chain extenders such as carbonate compounds and diisocyanate compounds can also be used, but the amount thereof is usually 10 mol % or less, preferably 5 mol % or less, and more preferably 3 mol % or less of carbonate bonds and urethane bonds relative to 100 mol % of all monomer units constituting the polyester.

[0136] Specific examples of carbonate compounds include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylene carbonate, diamyl carbonate, dicyclohexyl carbonate, etc. In addition, carbonate compounds derived from hydroxy compounds such as phenols and alcohols, and composed of the same or different hydroxy compounds, can also be used.

[0137] Specific examples of the diisocyanate compound include known diisocyanates such as 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0138] The polyester according to the present disclosure can be obtained by a conventionally known method of polycondensing the above-mentioned diol unit and dicarboxylic acid unit. Specifically, the polyester can be produced by a general melt polymerization method in which an esterification reaction and / or transesterification reaction between the above-mentioned diol unit and dicarboxylic acid unit is carried out, followed by a polycondensation reaction under reduced pressure, or by a known solution heating dehydration condensation method using an organic solvent.

[0139] The amount of diol used in producing the polyester is substantially equimolar to 100 moles of the dicarboxylic acid or its derivative. However, since distillates are generally produced during the esterification and / or transesterification reaction and / or polycondensation reaction, the diol is generally used in an excess of 0.1 mol % or more and 20 mol % or less.

[0140] The polycondensation reaction is preferably carried out in the presence of a polymerization catalyst. The timing of adding the polymerization catalyst is not particularly limited as long as it is before the polycondensation reaction, and the catalyst may be added when the raw materials are charged or when pressure reduction is initiated.

[0141] Polymerization catalysts generally include compounds containing metal elements from Groups 1 to 14 of the periodic table, excluding hydrogen and carbon. Specific examples include compounds containing organic groups, such as carboxylates, alkoxy salts, organic sulfonates, or β-diketonate salts, containing at least one metal selected from the group consisting of titanium, zirconium, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium, strontium, sodium, and potassium, as well as inorganic compounds, such as oxides and halides, of the aforementioned metals, and mixtures thereof. Among these, metal compounds containing titanium, zirconium, germanium, zinc, aluminum, magnesium, and calcium, and mixtures thereof, are preferred, with titanium compounds, zirconium compounds, and germanium compounds being particularly preferred. Furthermore, because the polymerization rate increases when the catalyst is in a molten or dissolved state during polymerization, compounds that are liquid during polymerization or soluble in ester oligomers or polyesters are preferred.

[0142] The titanium compound is preferably a tetraalkyl titanate, specifically tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-t-butyl titanate, tetraphenyl titanate, tetracyclohexyl titanate, tetrabenzyl titanate, and mixed titanates thereof. Titanium (oxy)acetylacetonate, titanium tetraacetylacetonate, titanium (diisoproxide)acetylacetonate, titanium bis(ammonium lactate)dihydroxide, titanium bis(ethylacetoacetate)diisopropoxide, titanium (triethanolamine)isopropoxide, polyhydroxytitanium stearate, titanium lactate, titanium triethanolamine, butyl titanate dimer, and the like are also preferably used. Furthermore, titanium oxide and composite oxides containing titanium and silicon are also preferably used. Among these, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, titanium(oxy)acetylacetonate, titanium tetraacetylacetonate, titanium bis(ammonium lactate) dihydroxide, polyhydroxytitanium stearate, titanium lactate, butyl titanate dimer, titanium oxide, and titania / silica composite oxide (for example, product name: C-94 manufactured by Acordis Industrial Fibers) are preferred, and tetra-n-butyl titanate, polyhydroxytitanium stearate, titanium(oxy)acetylacetonate, titanium tetraacetylacetonate, and titania / silica composite oxide (for example, product name: C-94 manufactured by Acordis Industrial Fibers) are particularly preferred.

[0143] Specific examples of zirconium compounds include zirconium tetraacetate, zirconium acetate hydroxide, zirconium tris(butoxy)stearate, zirconyl diacetate, zirconium oxalate, zirconyl oxalate, potassium zirconium oxalate, polyhydroxyzirconium stearate, zirconium ethoxide, zirconium tetra-n-propoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide, zirconium tetra-t-butoxide, zirconium tributoxyacetylacetonate, and mixtures thereof. Zirconium oxide and composite oxides containing, for example, zirconium and silicon may also be used. Among these, zirconyl diacetate, zirconium tris(butoxy)stearate, zirconium tetraacetate, zirconium acetate hydroxide, ammonium zirconium oxalate, potassium zirconium oxalate, polyhydroxyzirconium stearate, zirconium tetra-n-propoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide, and zirconium tetra-t-butoxide are preferred.

[0144] Specific examples of germanium compounds include inorganic germanium compounds such as germanium oxide and germanium chloride, and organic germanium compounds such as tetraalkoxygermanium. From the viewpoints of cost and availability, germanium oxide, tetraethoxygermanium, and tetrabutoxygermanium are preferred, with germanium oxide being particularly preferred.

[0145] When a metal compound is used as a polymerization catalyst, the amount of catalyst used, expressed as the amount of metal relative to the polyester produced, is usually 5 ppm or more, preferably 10 ppm or more, and the upper limit is usually 30,000 ppm or less, preferably 1,000 ppm or less, more preferably 250 ppm or less, and particularly preferably 130 ppm or less. If the amount of catalyst used is too large, not only is it economically disadvantageous but the thermal stability of the polymer is reduced, while if the amount is too small, the polymerization activity is reduced, which makes it more likely that the polymer will decompose during polymer production. As for the amount of catalyst used here, the method of reducing the amount of catalyst used is a preferred embodiment, because the amount of terminal carboxyl groups in the polyester produced is reduced as the amount of catalyst used is reduced.

[0146] The reaction temperature for the esterification reaction and / or transesterification reaction between diol units and dicarboxylic acid units is usually in the range of 150°C to 260°C, and the reaction atmosphere is usually an inert gas atmosphere such as nitrogen or argon. The reaction pressure is usually normal pressure to 10 kPa, and the reaction time is usually 1 hour to 10 hours.

[0147] In the above-mentioned production process, a chain extender (coupling agent) may be added to the reaction system. After the polycondensation is completed, the chain extender is added to the reaction system in a homogeneous molten state without a solvent, and reacted with the polyester obtained by polycondensation.

[0148] High-molecular-weight polyesters using these chain extenders (coupling agents) can be produced using known techniques. After polycondensation is complete, the chain extender is added to the reaction system in a homogeneous, molten state without a solvent and reacted with the polyester obtained by polycondensation. Specifically, a polyester with a higher molecular weight can be obtained by reacting the chain extender with a polyester prepolymer obtained by catalytically reacting a diol with a dicarboxylic acid, which has substantially hydroxyl end groups and a mass-average molecular weight (Mw) of 20,000 or more, preferably 40,000 or more. A prepolymer with a mass-average molecular weight of 20,000 or more can be produced with the use of a small amount of coupling agent without being affected by residual catalyst, even under harsh conditions such as a molten state, and therefore without forming gel during the reaction. [Example]

[0149] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0150] [Example 1] A medium containing the following components in 1 L of distilled water was prepared as a medium for microbial fermentation. (Medium composition) 0.5g MgCl2 6H2O 0.2g NaCl 100mM sodium phosphate buffer, pH 6.0, 160mL 0.6g NH4Cl 0.05mL of 85% H3PO4 0.15g KCl ·Trace metal complex solution (LS06) 10mL Vitamin B Complex Solution (LS03) 10mL 1000mg / L resazurin 1mL 0.0025g FeCl3 Cysteine ​​HCl monohydrate 0.75g 15g agarose 100 mM sodium phosphate buffer solution is prepared by dissolving 13.2 g of NaH2PO4 and 1.1 g of Na2HPO4·7H2O in 1 L of water.

[0151] A Clostridium autoethanogenum culture was prepared for microbial fermentation. The Clostridium autoethanogenum culture was obtained from the German Resource Centre for Biological Material (DSMZ) and has the accession number DSMZ10061.

[0152] A 5 L continuous stirred tank reactor was charged with 4.9 L of the above medium. The headspace gas in the continuous stirred tank reactor was switched to 95% CO, 5% CO at atmospheric pressure. 100 mL of Clostridium autoethanogenum culture was inoculated. The continuous stirred tank reactor was maintained at 37°C and agitated at 200 rpm at the beginning of the culture and 400 rpm during the growth phase. During agitation, the pH of the culture was maintained at 5.5 by automatic addition of 5 M NaOH.

[0153] A 234 mL sterile serum bottle was purged three times with steel mill waste gas (composition: 53% CO, 18% CO2, 26% N2, 3% H2) and then evacuated to a vacuum of -5 psi. 50 mL of the above culture medium was directly transferred into the serum bottle. While maintaining the reaction temperature at 37°C using a shaking incubator, the headspace of the serum bottle was filled with the above waste gas and pressurized to 25 psig. The culture medium was incubated at 37°C with shaking. After 5 hours, the ethanol concentration in the culture medium was 1.675 g / L, confirming the production of ethanol by microbial fermentation.

[0154] After microbial fermentation, the culture solution was separated into solid and liquid components using a solid-liquid separation filter device under conditions of a culture solution introduction pressure of 200 kPa or more. The liquid component was then introduced into a distillation apparatus equipped with a heater using steam at 170°C. After the temperature at the bottom of the distillation column was raised to 101°C within 15 minutes, the liquid component was introduced into the middle of the distillation column, and during continuous operation, the column was operated continuously under conditions of 101°C at the bottom, 99°C at the middle, and 91°C at the top, at a rate of 15 seconds / L, to purify ethanol.

[0155] Purified ethanol was supplied at 10 L / Hr to a multi-tube, externally heated, isothermal reactor packed with 1.5 L of γ-AlO catalyst (3 mmΦ x 3 mmH) under a pressure of 10 kg / cm. 2 G. The reaction was carried out at 370°C for 500 hours, and ethylene was produced by intramolecular dehydration of ethanol.

[0156] The produced ethylene was introduced into an ethylene oxidation reactor and catalytically oxidized in gas phase with a molecular oxygen-containing gas in the presence of a silver catalyst to obtain a reaction product gas containing ethylene oxide. The reaction product gas containing ethylene oxide was supplied to the bottom of the ethylene oxide absorber, and water was introduced from the top of the ethylene oxide absorber and brought into countercurrent contact with the reaction product gas, causing the ethylene oxide in the reaction product gas to be absorbed by the water. Unabsorbed gas near the top of the ethylene oxide absorber was circulated to the ethylene oxidation reactor. The bottom liquid of the ethylene oxide absorber was supplied to the top of the ethylene oxide stripper, which had a top pressure of 0.045 MPa (gauge) and a bottom temperature of 115°C. A portion of the bottom liquid of the ethylene oxide absorber was circulated to the ethylene oxide absorber. The vapor stripped near the top of the ethylene oxide stripper was condensed in a condenser, a portion of which was refluxed to the ethylene oxide stripper and a portion of which was supplied to the ethylene oxide dehydration tower. The vapor near the top of the ethylene oxide dehydration tower was condensed in a condenser, a portion of the condensate was refluxed to the dehydration tower, and the remainder of the condensate was supplied to the light fraction separation tower. The vapor near the top of the light fraction separation column was sent to a condenser, and the condensate was refluxed to the light fraction separation column. The bottom liquid of the light fraction separation column was supplied to the ethylene oxide fractionator. Ethylene oxide vapor near the top of the ethylene oxide rectification column was condensed in a condenser, a portion of which was refluxed to the ethylene oxide rectification column, and the remainder was withdrawn as ethylene oxide.

[0157] The extracted ethylene oxide was added to the bottom liquid of the ethylene oxide dehydration column and supplied to a hydration reactor. The reaction was carried out at a pressure of 1.8 MPa gage and a reaction temperature of 150°C to obtain a 15.2% by mass aqueous ethylene glycol solution. The aqueous ethylene glycol solution was supplied to a first evaporator operated at a top pressure of 0.41 MPa (gauge) and a bottom temperature of 153°C. The bottom liquid from the first evaporator was supplied to a second evaporator operated at a top pressure of 0.17 MPa (gauge) and a bottom temperature of 136°C. The bottom liquid from the second evaporator was supplied to a third evaporator operated at a top pressure of 0.07 MPa (gauge) and a bottom temperature of 124°C. The bottom liquid from the third evaporator was supplied to a fourth evaporator operated at a top pressure of -0.03 MPa (gauge) and a bottom temperature of 105°C. The bottom liquid from the fourth evaporator was supplied to an ethylene glycol dehydration column to remove water, and then supplied to an ethylene glycol distillation column. Ethylene glycol was separated from the top of the ethylene glycol distillation column. In this way, the ethylene glycol of Example 1 was obtained.

[0158] [Example 2] A stainless steel substrate (150 mm × 250 mm, 150 μm thick) was used as a current collector, and a metal layer made of Au was formed on its surface by sputtering. The metal layer had a uniform thickness of 100 nm in the surface direction. The current collector on which the metal layer was formed was immersed in 10 mL of an ethanol solution containing 1 mM of 1-(2-mercaptoethyl)-4-(3-aminopropyl)-pyridinium bromide for 48 hours, thereby immobilizing the modified organic molecules on the surface of the metal layer. A three-electrode cell was constructed using the reduction catalyst prepared in this way. Specifically, the reduction catalyst was used as the working electrode, an Ag / AgCl electrode as the reference electrode, and a Pt electrode as the counter electrode, and a three-electrode cell was constructed using an H-shaped cell. The Pt electrode was placed in a cell separated by a glass filter.

[0159] Next, 100% CO2 gas was bubbled into a 5% NaHCO3 aqueous solution, and CO2 was dissolved until the CO2 concentration absorbed by the solution reached saturation. The concentrations of CO2 gas absorbed by the 5% NaHCO3 aqueous solution were measured at the inlet and outlet, and when they reached the same concentration, the concentration in the aqueous solution was determined to have reached saturation. The 5% NaHCO3 aqueous solution prepared in this way was used as a CO2 absorbent and an electrolyte for CO2 reduction in a three-electrode cell.

[0160] In a three-electrode cell, constant-current electrolysis was performed so that the potential applied to the working electrode was -1.2 V vs. Ag / AgCl. The electrolysis time was 60 minutes. During electrolysis, 100% CO2 gas was bubbled into the electrolysis chamber of the working electrode, and the solution was stirred at a stirring speed of 800 rpm using a magnetic stirrer.

[0161] The ethylene glycol produced by constant-current electrolysis was then purified. Specifically, the electrolyte was removed from the three-electrode cell and supplied to a first evaporator operated at a top pressure of 0.41 MPa (gauge) and a bottom temperature of 153°C. The bottom liquid from the first evaporator was supplied to a second evaporator operated at a top pressure of 0.17 MPa (gauge) and a bottom temperature of 136°C. The bottom liquid from the second evaporator was supplied to a third evaporator operated at a top pressure of 0.07 MPa (gauge) and a bottom temperature of 124°C. The bottom liquid from the third evaporator was supplied to a fourth evaporator operated at a top pressure of −0.03 MPa (gauge) and a bottom temperature of 105°C. The bottom liquid from the fourth evaporator was supplied to an ethylene glycol dehydration column to remove moisture, and then supplied to an ethylene glycol distillation column. Ethylene glycol was separated from the top of the ethylene glycol distillation column. In this way, ethylene glycol of Example 2 was obtained.

[0162] [Comparative Example 1] An aqueous solution of ethylene oxide derived from fossil fuel was diluted with water to prepare an aqueous solution of ethylene oxide with a mass ratio of ethylene oxide to water of 10:1. The aqueous solution of ethylene oxide was charged into a reactor and heated at a temperature of 200°C and a pressure of approximately 35 kg / cm. 2Ethylene oxide and water were reacted under the conditions of G to obtain an approximately 15% aqueous ethylene glycol solution. The resulting aqueous ethylene glycol solution was concentrated and completely dehydrated, and then charged into a distillation column. Nitrogen gas was introduced into the top of the distillation column at a pressure of 15 Nm 2 Ethylene glycol was separated and purified under a reduced pressure of 20 mmHg while blowing in the mixture at a flow rate of 10,000 kg / Hr. Ethylene glycol of Comparative Example 1 was obtained at a distillation rate of about 10,000 kg / Hr.

[0163] [Kjeldahl nitrogen content measurement] The Kjeldahl nitrogen content of the ethylene glycols of Examples 1 and 2 and Comparative Example 1 was measured according to JIS K0102:2019 44.1 (Kjeldahl method) and 44.2 (indophenol blue absorptiometry). The results are shown in Table 1.

[0164] [Measurement of carbon dioxide molecular content] For each of the ethylene glycols in Examples 1 and 2 and Comparative Example 1, 35 mg was weighed on a SiC stage to prepare a sample. The carbon dioxide content of the sample was measured by thermal desorption mass spectrometry (TDS-MS) under the following conditions. The results are shown in Table 1. (Measurement conditions) ·Device name: Denshi Kagaku EMD-WA1000S / W type Heating the sample on the SiC stage Ionization method: Electron Ionization (EI) Measurement mode: SCAN mode Measurement mass range (m / z): 1 to 200 ·Heating conditions: 50℃~100℃ Heating rate: 10℃ / min Holding temperature and holding time: 100°C for 30 minutes

[0165] [Table 1]

[0166] As is clear from Table 1 above, ethylene glycol made from carbon monoxide gas or carbon dioxide gas has a lower Kjeldahl nitrogen content than ethylene glycol derived from fossil fuels. It is also clear that ethylene glycol made from carbon monoxide gas or carbon dioxide gas contains a larger amount of carbon dioxide molecules than ethylene glycol derived from fossil fuels. [Explanation of symbols]

[0167] 1. Reduction catalyst 11 Circuit Board 12 Reflective layer 13 Reduction electrode layer 14 1st solar cell 14a n-type a-Si layer 14b Intrinsic a-SiGe layer 14c p-type μc-Si layer 15 2nd solar cell 15a n-type a-Si layer 15b Intrinsic a-SiGe layer 15c p-type μc-Si layer 16 Third solar cell 16a n-type a-Si layer 16b Intrinsic a-Si layer 16c p-type μc-Si layer 17 Multijunction solar cell 18 Oxidized electrode layer 19 Oxidation catalyst layer 20 Reduction catalyst layer 30 Photochemical reaction cell 31 Electrolytic cell 31a Electrolytic cell for oxidation reaction 31b Electrolytic cell for reduction reaction 41 Electrolyzer flow path 42 Circulation mechanism 43 Ion exchange membrane 44 Temperature adjustment mechanism 51 Opening 52 Opening 100 spacer organic molecular layer 101 Current collector 102 Metal layer 109 Reactive Functional Groups 110 Skeleton 111 Amino group 112 Organic molecules containing quaternary nitrogen cations (modified organic molecules) 200 Chemical Reactor 210 Chemical Reaction Apparatus 220 Chemical Reactor L light

Claims

1. Ethylene glycol produced using at least one gas selected from the group consisting of carbon monoxide and carbon dioxide as a raw material.

2. The carbon dioxide molecule content is 2.2 x 10 １８ pieces / g or more 1.5×10 １９ The ethylene glycol according to claim 1, wherein the molecular weight of the ethylene glycol is 1 / g or less.

3. 3. The ethylene glycol according to claim 1 or 2, having a Kjeldahl nitrogen content of 700 μg / g or less.

4. A polyester consisting of diol units and dicarboxylic acid units, The polyester according to claim 1 or 2, wherein the diol unit is ethylene glycol.

5. The polyester according to claim 4, wherein the dicarboxylic acid unit is at least one selected from the group consisting of terephthalic acid derived from a fossil fuel, terephthalic acid derived from biomass, and terephthalic acid derived from carbon dioxide gas.

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