Heat exchange medium and method for manufacturing the same

Abstract

To reduce CO2 emissions associated with the manufacture of heat exchange media. [Solution] The heat exchange medium is an intermediate product in the process of producing ethylene oxide using a catalytic reaction of ethylene and oxygen, and contains a high-boiling fraction in which ethylene oxide is absorbed into water. Here, the content of the high-boiling fraction is 20% by mass or more and 100% by mass or less, and the content of ethylene glycol due to the high-boiling fraction is 5% by mass or more and 65% by mass or less. The heat exchange medium may contain formic acid and / or formate. The pH of the heat exchange medium may be 6.0 to 10. The heat exchange medium may contain phosphoric acid and / or phosphate. The heat exchange medium may contain diethylene glycol and / or triethylene glycol.

Description

Technical Field

[0001] The present invention relates to a heat exchange medium capable of reducing CO2 emissions associated with production and a method for producing this heat exchange medium.

Background Art

[0002] As a heat exchange medium used for temperature control of various devices, a mixture of water and glycol-based compounds is widely used because of its low cost and excellent thermal stability. On the other hand, Patent Document 1 describes a method for purifying ethylene glycol discharged from the production process of ethylene oxide.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, commercially available glycol-based compounds are used as heat exchange media. The inventor of the present application has found that by using an intermediate product obtained in the production process of ethylene oxide, a heat exchange medium having no inferior performance to a heat exchange medium using a commercially available glycol-based compound can be obtained, and the present invention has been completed.

[0005] When using a commercially available glycol-based compound, CO2 is emitted in the production process of the glycol-based compound. Here, a heat exchange medium that can produce a heat exchange medium without manufacturing the glycol-based compound itself and can reduce the CO2 emissions from the production of the glycol-based compound to the production of the heat exchange medium is required.

Means for Solving the Problems

[0006] The heat exchange medium according to the first invention of this application is an intermediate product in the process of producing ethylene oxide using a catalytic reaction of ethylene and oxygen, and contains a high-boiling fraction in which ethylene oxide is absorbed into water. Here, the content of the high-boiling fraction is 20% by mass or more and 100% by mass or less, and the content of ethylene glycol resulting from the high-boiling fraction is 5% by mass or more and 65% by mass or less.

[0007] The heat exchange medium may contain formic acid and / or formate salts. The pH of the heat exchange medium may be 6.0 to 10. Here, the heat exchange medium may contain phosphoric acid and / or phosphate salts. The heat exchange medium may contain diethylene glycol and / or triethylene glycol.

[0008] The second invention of this application is a method for producing a heat exchange medium, which is the first invention of this application, wherein a high-boiling-point fraction is obtained in the process of producing ethylene oxide using a catalytic reaction of ethylene and oxygen, and a heat exchange medium is produced using this high-boiling-point fraction.

[0009] Here, ion exchange treatment can be performed on the high-boiling-point fraction, and a heat exchange medium can be produced using the ion-exchanged high-boiling-point fraction. In the ion exchange treatment, ion exchange treatment can be performed using one of the cation exchange resins or anion exchange resins, and then ion exchange treatment can be performed using the other ion exchange resin. [Effects of the Invention]

[0010] According to the present invention, by using a high-boiling fraction, which is an intermediate product in the ethylene oxide production process, CO2 emissions associated with the production of the heat exchange medium can be reduced compared to the case where a commercially available compound equivalent to the high-boiling fraction is used. [Modes for carrying out the invention]

[0011] The heat exchange medium of the present invention utilizes a high-boiling fraction obtained as an intermediate product in the production process of ethylene oxide using a catalytic reaction of ethylene and oxygen. This high-boiling fraction is obtained after ethylene oxide is absorbed into water and the low-boiling fraction of ethylene oxide is released, and mainly contains ethylene glycol and water. By producing the heat exchange medium using the high-boiling fraction, it is possible to produce a heat exchange medium containing ethylene glycol without producing ethylene glycol itself, thereby reducing CO2 emissions from the production of ethylene glycol to the production of the heat exchange medium.

[0012] The industrial production method for ethylene glycol involves the following five steps (1) to (5).

[0013] (1) Ethylene oxide is produced by reacting ethylene and oxygen using a catalyst such as silver. (2) The mixture containing ethylene oxide is absorbed into an absorbent solution (main component: water). (3) Release ethylene oxide, a low-boiling fraction, from the absorbent solution. (4) The released ethylene oxide is reacted with water to produce ethylene glycol. (5) Ethylene glycol is separated and purified by distillation to obtain ethylene glycol.

[0014] Ethylene glycol is obtained from the intermediate products when ethylene oxide is produced by steps (1) to (5) above. The high-boiling fraction used as the heat exchange medium in this embodiment is obtained in step (3) above.

[0015] In the heat exchange medium, the content of high-boiling fractions should be between 20% by mass and 100% by mass. Furthermore, the content of ethylene glycol resulting from the high-boiling fractions should be between 5% by mass and 65% by mass. By satisfying these compositional requirements, a heat exchange medium with performance comparable to commercially available heat exchange mediums using ethylene glycol can be obtained. Preferably, the content of ethylene glycol resulting from the high-boiling fractions should be 10% by mass or more.

[0016] High-boiling fractions can be used as a heat exchange medium on their own, or a mixture of high-boiling fractions and water (different from the water contained in the high-boiling fractions) can be used as a heat exchange medium. Furthermore, a heat exchange medium can be constructed by mixing high-boiling fractions with commercially available compounds identical to those contained in the high-boiling fractions. Examples of compounds found in high-boiling fractions include glycol compounds (ethylene glycol, diethylene glycol, triethylene glycol), formic acid, and formate salts.

[0017] Here, the higher the content of the high-boiling-point fraction, the lower the CO2 emissions obtained for the heat exchange medium. The content of the high-boiling-point fraction is preferably 50% by mass or more, and more preferably 70% by mass or more.

[0018] When adding water to a high-boiling fraction, the amount of water to be added can be determined as appropriate. For example, if the high-boiling fraction is 100% by mass, 3 to 100% by mass (extra) of water can be added. Furthermore, while there are no particular limitations on the type of water to be added to the high-boiling fraction, ion-exchanged water with an electrical conductivity of 1 [μS / cm] (= 0.1 [mS / m] (25℃)) or less, obtained by ion exchange treatment, can be used.

[0019] As described above, the ethylene glycol content due to the high-boiling fraction should be 5% by mass or more and 65% by mass or less, preferably 10% by mass or more and 60% by mass or less, more preferably 13% by mass or more and 60% by mass or less, even more preferably 15% by mass or more and 60% by mass or less, and particularly preferably 20% by mass or more and 55% by mass or less. Any high-boiling fraction containing ethylene glycol that satisfies this content should be used.

[0020] When obtaining a high-boiling fraction, measure the content of ethylene glycol. If this content is 5% by mass or more and 65% by mass or less, this high-boiling fraction can be used as a heat exchange medium. When the content of ethylene glycol due to the high-boiling fraction is less than 5% by mass, commercially available ethylene glycol must be added in order to be used as a heat exchange medium, and the effect of reducing CO2 emissions becomes poor. Also, when the content of ethylene glycol is higher than 65% by mass, the viscosity of the heat exchange medium tends to become excessively high, and it becomes difficult to handle the heat exchange medium as it is. Here, when the viscosity of the heat exchange medium is excessively high, the viscosity can be adjusted by appropriately diluting it with water.

[0021] In addition to water and ethylene glycol, the heat exchange medium may contain other components. Glycol-based compounds other than ethylene glycol may be included, and examples of such glycol-based compounds include diethylene glycol and triethylene glycol.

[0022] The heat exchange medium can include at least one of formic acid and formate. The above-mentioned high-boiling fraction may contain formic acid or formate, and formic acid or formate contained in the high-boiling fraction can be used. Examples of formates include sodium formate and potassium formate. A plurality of types of formates can also be used in combination. In the heat exchange medium, the total content of formic acid and formate can be 0.01 to 2.0% by mass.

[0023] Rust inhibitors can be added to the heat exchange medium. Examples of rust inhibitors include triethanolamine, benzotriazole, sodium benzoate, sodium nitrate, and sebacic acid. The content of triethanolamine can be 0.3 to 1.0% by mass. The content of benzotriazole can be 0.10% by mass or less. The content of sodium benzoate can be 2.0% by mass or less. The content of sodium nitrate can be 1.0% by mass or less. The content of sebacic acid can be 0.5% by mass or less. One type of rust inhibitor can be used, or multiple types of rust inhibitors can be used in combination.

[0024] The high-boiling fraction can be used as the heat exchange medium as it is, or a heat exchange medium obtained by performing ion exchange treatment on the high-boiling fraction can also be used. In the ion exchange treatment, a cation exchange resin or an anion exchange resin can be used. Either only cation exchange or only anion exchange can be performed, or both can be performed. As the ion exchange resin, a gel-type resin or a macroporous-type resin can be used, and it is preferable to use a macroporous-type resin. The ion exchange treatment includes column treatment (continuous treatment) and batch treatment.

[0025] A pH buffer can be added to the heat exchange medium. Examples of pH buffers include phosphoric acid, phosphates, metal hydroxides, and amine compounds. Examples of metal hydroxides include sodium hydroxide and potassium hydroxide. The content of the metal hydroxide can be 1.5% by mass or less. Here, one type of pH buffer can be used alone, or multiple types of pH buffers can be used in combination. The pH buffer can be added after the ion exchange treatment.

[0026] Examples of phosphates include potassium phosphate and sodium phosphate. Examples of potassium phosphate include potassium phosphate, potassium hydrogen phosphate, and dipotassium hydrogen phosphate. Examples of sodium phosphate include sodium phosphate, sodium hydrogen phosphate, and dipotassium hydrogen phosphate. One type of phosphate can be used, or multiple types of phosphates can be used in combination.

[0027] The pH of the heat exchange medium can be set to 6.0 to 10. Here, the pH is preferably 6.0 to 9.0, and more preferably 6.5 to 8.8.

[0028] An antifoaming agent can be added to the heat exchange medium. Examples of antifoaming agents include silicone. Types of silicone include emulsion type, self-emulsifying type, oil type, oil compound type, powder type, solution type, and solid type, with emulsion type and self-emulsifying type being preferred. One type of antifoaming agent can be used, or multiple types of antifoaming agents can be used in combination. [Examples]

[0029] Examples of the present invention will be described below. However, the present invention is not limited to the examples described below.

[0030] First, ethylene was oxidized in the gas phase with oxygen in the presence of a silver catalyst to produce a reaction gas containing ethylene oxide. This reaction gas was then treated with water to produce ethylene oxide. The high-boiling fraction, obtained by separating the ethylene oxide from the low-boiling fraction of the water containing ethylene oxide, was used. Three types of high-boiling fractions were prepared. Table 1 below shows the composition and pH of the three types of high-boiling fractions.

[0031] [Table 1]

[0032] High-boiling fractions A, B, and C contained ethylene glycol and diethylene glycol as glycol compounds. In high-boiling fraction A, the glycol compound content was 32% by mass; in high-boiling fraction B, the glycol compound content was 57% by mass; and in high-boiling fraction C, the glycol compound content was 37 parts by weight.

[0033] (Example 1) In Example 1, the heat exchange medium used was only the high-boiling fraction C shown in Table 1 above. That is, the content of high-boiling fraction C was 100% by mass.

[0034] (Example 2) For Example 2, a mother liquor was prepared by adding water to the high-boiling fraction A shown in Table 1 above. Here, the amount of water added was 3% by mass (external) per 100% by mass of the high-boiling fraction A, and the water used was ion-exchanged water whose electrical conductivity was 1 [μS / cm] (= 0.1 [mS / m] (25℃)) or less by ion exchange. To adjust the pH of the heat exchange medium to 7.5, 0.6% by mass of phosphoric acid, 1.5% by mass of phosphate, and 1.2% by mass of sodium hydroxide were added to the mother liquor. In addition, to give the heat exchange medium a rust-preventive function, 0.7% by mass of triethanolamine was added to the mother liquor to produce the heat exchange medium of this example.

[0035] Here, sodium phosphate and potassium phosphate were used as phosphates. For the sodium phosphate (total 0.7% by mass), 0.2% by mass of monosodium dihydrogen phosphate and 0.5% by mass of disodium hydrogen phosphate were used. For the potassium phosphate (total 0.8% by mass), 0.6% by mass of potassium dihydrogen phosphate and 0.2% by mass of dipotassium hydrogen phosphate were used.

[0036] (Example 3) In this embodiment, when preparing the mother liquor of the heat exchange medium, the amount of water added was 100% by mass (external number) relative to 100% by mass of the high-boiling fraction A. The water used was ion-exchanged water, in which the electrical conductivity was reduced to 1 [μS / cm] (= 0.1 [mS / m] (25℃)) or less by ion exchange. To adjust the pH of the heat exchange medium to 7.5, 0.6% by mass of phosphoric acid, 1.5% by mass of phosphate, and 1.2% by mass of sodium hydroxide were added to the mother liquor. Furthermore, in order to give the heat exchange medium a rust-preventive function, 0.7% by mass of triethanolamine was added to the mother liquor to produce the heat exchange medium of this embodiment.

[0037] Here, sodium phosphate and potassium phosphate were used as phosphates. For the sodium phosphate (total 0.7% by mass), 0.2% by mass of monosodium dihydrogen phosphate and 0.5% by mass of disodium hydrogen phosphate were used. For the potassium phosphate (total 0.8% by mass), 0.6% by mass of potassium dihydrogen phosphate and 0.2% by mass of dipotassium hydrogen phosphate were used.

[0038] (Example 4) As the mother liquor for the heat exchange medium of Example 4, high-boiling fraction B shown in Table 1 above was prepared. To adjust the pH of the heat exchange medium to 8.0, 0.6% by mass of phosphoric acid, 1.8% by mass of phosphate, and 1.2% by mass of sodium hydroxide were added to the mother liquor. In addition, to give the heat exchange medium a rust-preventive function, 0.1% by mass of benzotriazole was added to the mother liquor to produce the heat exchange medium of this example.

[0039] Here, sodium phosphate and potassium phosphate were used as phosphates. For the sodium phosphate (total 1.0 mass%), 0.5 mass% monosodium dihydrogen phosphate and 0.5 mass% disodium hydrogen phosphate were used. For the potassium phosphate (total 0.8 mass%), 0.6 mass% potassium dihydrogen phosphate and 0.2 mass% dipotassium hydrogen phosphate were used.

[0040] (Example 5) The heat exchange medium of Example 5 was produced by performing an ion exchange treatment on the high-boiling fraction A shown in Table 1 above. Here, a cation exchange resin was used for the ion exchange treatment. Specifically, a styrene-based macroporous cation exchange resin with a water retention capacity of 47% and a sulfonic acid group (strong acid) as a functional group was used. The high-boiling fraction A was allowed to remain in the ion exchange resin for 30 minutes, and then filtered. Here, the amount of ion exchange resin was 5% by mass relative to 100% by mass of the high-boiling fraction A.

[0041] The heat exchange medium described in this embodiment was produced by adding additives to the filtrate. The additives included a rust inhibitor, a pH buffer, and an antifoaming agent. Triethanolamine, benzotriazole, sodium nitrate, sebaciic acid, and sodium benzoate were used as rust inhibitors. Phosphoric acid, phosphates (sodium phosphate and potassium phosphate), and sodium hydroxide were used as pH buffers. Silicone was used as an antifoaming agent.

[0042] (Example 6) The mother liquor of the heat exchange medium, which is Example 6, was produced by performing ion exchange treatment on the high-boiling fraction A shown in Table 1 above. In this ion exchange treatment, both ion exchange treatment using a cation exchange resin and ion exchange treatment using an anion exchange resin were performed.

[0043] As the cation exchange resin, a styrene-based macroporous type with a water retention capacity of 47% and a sulfonic acid group (strongly acidic) as a functional group was used. The high-boiling fraction A was allowed to remain in the cation exchange resin for 30 minutes, and then filtered. Here, the cation exchange resin was 5% by mass relative to 100% by mass of the high-boiling fraction A.

[0044] Next, the filtrate was allowed to remain in the anion exchange resin for 30 minutes. Here, the amount of anion exchange resin was 5% by mass relative to 100% by mass of the filtrate. The anion exchange resin used was an acrylic gel type with a water retention capacity of 58% and a dimethylamine group as a functional group.

[0045] Next, a heat exchange medium, which is the basis of Example 6, was produced by adding additives to the mother liquor obtained by ion exchange treatment. Here, the additives included a rust inhibitor, a pH buffer, and an antifoaming agent. Triethanolamine, benzotriazole, sodium nitrate, sebaic acid, and sodium benzoate were used as rust inhibitors. Phosphoric acid, phosphates (sodium phosphate and potassium phosphate), and sodium hydroxide were used as pH buffers. Silicone was used as an antifoaming agent. In Example 6, the amounts of sodium phosphate and sodium hydroxide added were different from those in Example 5.

[0046] (Comparative Example 1) Comparative Example 1 was prepared using commercially available ethylene glycol and deionized water to have a composition equivalent to that of the heat exchange medium in Example 1. Here, the ethylene glycol content was 37% by mass, and the deionized water content was 63% by mass. As the deionized water, deionized water with an electrical conductivity of 1 [μS / cm] (= 0.1 [mS / m] (25℃)) or less was used.

[0047] (Comparative Example 2) A heat exchange medium, which is Comparative Example 2, was prepared by mixing commercially available compounds with water, ethylene glycol, and diethylene glycol to obtain a composition equivalent to that of Example 2. In Comparative Example 2, sodium formate contained in high-boiling fraction A was omitted, and 1.0% by mass of triethanolamine was added as a rust inhibitor. In addition, ion-exchanged water was used, in which the electrical conductivity was reduced to 1 [μS / cm] (= 0.1 [mS / m] (25℃)) or less by ion exchange.

[0048] (Comparative Example 3) A heat exchange medium, which is Comparative Example 3, was prepared by mixing commercially available compounds with water, ethylene glycol, diethylene glycol, and sodium formate to obtain a composition equivalent to that of Example 2. In Comparative Example 3, phosphoric acid, phosphates (potassium phosphate and sodium phosphate), and sodium hydroxide contained in the heat exchange medium of Example 2 were omitted, and 0.7% by mass of triethanolamine was added as a rust inhibitor. In addition, ion-exchanged water with an electrical conductivity of 1 [μS / cm] (= 0.1 [mS / m] (25℃)) or less was used as the water.

[0049] (Comparative Example 4) A heat exchange medium, which is Comparative Example 4, was prepared by mixing commercially available compounds with water, ethylene glycol, and diethylene glycol to obtain a composition equivalent to that of Example 3. In Comparative Example 4, sodium formate, phosphoric acid, phosphates (potassium phosphate and sodium phosphate), and sodium hydroxide, which are contained in the heat exchange medium of Example 3, were omitted. In addition, ion-exchanged water with an electrical conductivity of 1 [μS / cm] (= 0.1 [mS / m] (25℃)) or less was used as the water.

[0050] (Comparative Example 5) A heat exchange medium, which is Comparative Example 5, was prepared by mixing commercially available compounds to have a composition equivalent to that of the heat exchange medium in Example 6, excluding diethylene glycol and sodium formate. In Comparative Example 5, diethylene glycol and sodium formate, which are contained in the heat exchange medium of Example 6, were omitted. In addition, ion-exchanged water with an electrical conductivity of 1 [μS / cm] (= 0.1 [mS / m] (25℃)) or less was used as the water.

[0051] (Corrosion test) Corrosion tests were conducted using the heat exchange media described in Examples 1-6 and Comparative Examples 1-5. In the corrosion tests, the mass change C, as described later, was determined, and the corrosion state on the surface of the test specimens was visually evaluated.

[0052] In the corrosion tests for Example 1 and Comparative Example 1, bright-finished steel plates (SPCC-B) as specified in JIS G3141 were used as test specimens, and the tests were conducted by immersing the test specimens in a heat exchange medium in accordance with the provisions of JIS K2234 (Metal Corrosivity). Multiple conditions were set for the temperature of the heat exchange medium (immersion temperature) and the time the test specimens were immersed in the heat exchange medium (immersion time).

[0053] The mass m1 of the test specimen before immersion in the heat exchange medium and the mass m2 of the test specimen after immersion in the heat exchange medium were measured, and the change in mass C of the test specimen was determined. The change in mass C is expressed by the following equation (1).

[0054]

number

[0055] In equation (1) above, C is the change in mass [mg / cm²]. 2 ], where m1 is the mass of the test specimen before immersion in the heat exchange medium [mg], m2 is the mass of the test specimen after immersion in the heat exchange medium [mg], and S is the total surface area of ​​the test specimen before immersion in the heat exchange medium [cm²]. 2 ] When the test specimen corrodes, the mass m2 decreases to less than the mass m1, so the mass change C becomes a negative value.

[0056] In the corrosion tests for Examples 2-6 and Comparative Examples 2-5, the tensile strength of the tensile test was 180 [N / mm²] as specified in JIS H5202. 2 Aluminum alloy castings (AC2A-F) with a rating of ] or higher were used as test specimens, and the test was conducted by immersing the test specimens in a heat exchange medium in accordance with the provisions of JIS K2234 (Metal Corrosion Resistance). The temperature of the heat exchange medium (immersion temperature) was set to 88 [°C], and the immersion time of the test specimens in the heat exchange medium (immersion time) was set to 336 [hr]. Then, as described above, the mass change C of the test specimens was determined.

[0057] The visual inspection of the corrosion condition was evaluated in three stages, A, B, and C, based on the following criteria. Evaluation A: No corrosion was observed on the entire surface of the test specimen. Evaluation B: Corrosion is observed on less than 2% of the total surface area of ​​the test specimen. Evaluation C: Corrosion is observed on more than 2% of the total surface area of ​​the test specimen.

[0058] The results of the corrosion tests are shown in Tables 2-4 below. Tables 2-4 also show the solidification temperature (measured value) and pH of the heat exchange media used in Examples 1-6 and Comparative Examples 1-5.

[0059] [Table 2]

[0060] [Table 3]

[0061] [Table 4]

[0062] First, in Comparative Examples 1-4, commercially available compounds were used, resulting in CO2 generation during the manufacturing process of each compound. On the other hand, in Examples 1-6, high-boiling fractions A and B were used, and commercially available compounds were not used, thus reducing the CO2 generated during the manufacturing of commercially available compounds.

[0063] Next, as can be seen from Table 2 above, Example 1, which used high-boiling fraction C, showed less weight change and superior performance in visual evaluation compared to Comparative Example 1. Furthermore, as can be seen from Table 3 above, Examples 2-4, which used high-boiling fraction A or high-boiling fraction B, showed superior performance in visual evaluation compared to Comparative Examples 2-4.

[0064] Furthermore, as can be seen from Table 4 above, in Examples 5 and 6, which used high-boiling fraction A, comparable effects were obtained in terms of weight change and visual evaluation compared to Comparative Example 5. Comparative Example 5 is a heat exchange medium with excellent corrosion performance due to the addition of a pH buffer, rust inhibitor, and defoamer, but it was confirmed that Examples 5 and 6 are heat exchange mediums that are comparable to Comparative Example 5.

Claims

1. An intermediate product in the process of producing ethylene oxide using a catalytic reaction of ethylene and oxygen, comprising a high-boiling fraction in which ethylene oxide is absorbed into water, The content of the aforementioned high-boiling fraction is 20% by mass or more and 100% by mass or less. A heat exchange medium characterized in that the ethylene glycol content resulting from the high-boiling fraction is 5% by mass or more and 65% by mass or less.

2. The heat exchange medium according to claim 1, characterized by containing formic acid and / or formate salt.

3. The heat exchange medium according to claim 1, characterized in that the pH of the heat exchange medium is 6.0 to 10.

4. The heat exchange medium according to claim 1, characterized by containing phosphoric acid and / or phosphate.

5. The heat exchange medium according to claim 1, characterized by comprising diethylene glycol and / or triethylene glycol.

6. A method for manufacturing a heat exchange medium according to claim 1, In the process of producing ethylene oxide using a catalytic reaction between ethylene and oxygen, the high boiling point fraction is obtained. A method for producing a heat exchange medium, characterized by producing the heat exchange medium using the high-boiling point fraction.

7. The aforementioned high-boiling point fraction is subjected to ion exchange treatment. The method for producing a heat exchange medium according to claim 6, characterized in that the heat exchange medium is produced using the high-boiling point fraction that has undergone the ion exchange treatment.

8. The method for producing a heat exchange medium according to claim 7, characterized in that, in the ion exchange treatment, an ion exchange treatment is performed using one of the cation exchange resins and anion exchange resins, and then an ion exchange treatment is performed using the other ion exchange resin.

Images