JPWO2018135408A1 - Isopropyl alcohol composition and method for producing isopropyl alcohol - Google Patents

Abstract

An isopropyl alcohol composition comprising isopropyl alcohol and impurities, wherein a dissolved oxygen concentration is 0.1% or less with respect to an oxygen saturation solubility at 25 ° C. in the atmosphere, and a concentration of an organic acid as an impurity Provides an isopropyl alcohol composition having a mass basis of 20 ppb or less. Moreover, the manufacturing method of isopropyl alcohol which can obtain such an isopropyl alcohol composition is provided.

Description

  The present invention relates to an isopropyl alcohol composition and a method for producing isopropyl alcohol.

  In general, a semiconductor device is manufactured by a method of forming elements and wiring by repeating a film forming process, an etching process, and the like. In recent years, miniaturization and high integration of elements and wirings have been increasingly progressed while higher performance of semiconductor devices is required. Along with this, the influence of the quality of chemicals used for film formation, etching, etc. on the yield of semiconductor devices cannot be ignored, and there is a strong demand for improving the quality of chemicals.

  For example, isopropyl alcohol (also referred to as 2-propanol) used as a cleaning liquid or a drying liquid in a semiconductor device manufacturing process is strongly demanded to improve the quality as in the case of ultrapure water. Isopropyl alcohol is subjected to advanced purification in the production process, filled in a canister can, and further shipped and delivered with nitrogen gas sealed.

  However, the concentration of the organic acid contained as an impurity increases with time when isopropyl alcohol is stored or transported even if it is highly purified as described above and sealed with nitrogen gas sealed. This problem has been confirmed by the present inventors.

  Since an organic acid contained as an impurity in isopropyl alcohol is assumed to cause various problems such as surface corrosion of a semiconductor device, it is necessary to suppress a change in concentration over time.

  This invention is made | formed in view of such a conventional situation, and makes it a subject to provide the manufacturing method of the isopropyl alcohol composition by which the raise of the density | concentration of an organic acid with time is suppressed, and isopropyl alcohol. .

  As a result of intensive studies to solve the above problems, the present inventors have found that when the concentration of dissolved oxygen in isopropyl alcohol and the concentration of organic acids contained as impurities exceed a certain range, isopropyl alcohol is nitrogenated. Even when encapsulated with gas, the inventors have found that the concentration of organic acid increases during storage or transportation.

  As a result of further investigation based on the above knowledge, not only the concentration of dissolved oxygen in isopropyl alcohol is reduced but also the concentration of organic acids contained as impurities in isopropyl alcohol in a specific range in the isopropyl alcohol production process. By adjusting to, it succeeded in suppressing the increase in the concentration of organic acid over time very effectively, and completed the present invention.

  That is, according to the present invention, an isopropyl alcohol composition comprising isopropyl alcohol and impurities, wherein a dissolved oxygen concentration is 0.1% or less with respect to an oxygen saturation solubility at 25 ° C. in the atmosphere, and An isopropyl alcohol composition in which the concentration of the organic acid as an impurity is 20 ppb or less on a mass basis is provided.

  The isopropyl alcohol composition has a boiling point higher than that of isopropyl alcohol, and the concentration of the high boiling point compound as an impurity having 4 or more carbon atoms excluding the organic acid is 20 ppb on a mass basis. The following is preferable.

  The isopropyl alcohol composition preferably has a concentration of moisture as an impurity of 20 ppm or less on a mass basis.

Further, according to the present invention, a method for producing isopropyl alcohol, wherein isopropyl alcohol is produced by directly hydrating water with propylene,
A raw material supply step of supplying propylene and water having an acid catalyst dissolved therein and a pH adjusted to 2.5 to 4.5 to the reactor;
A reaction step of reacting propylene and water in the reactor;
A recovery step of separating unreacted propylene from the reaction mixture obtained in the reaction step and recovering a reaction mixture containing isopropyl alcohol;
A first distillation step of distilling the reaction mixture recovered in the recovery step in a distillation column to remove a low-boiling compound having a boiling point lower than that of isopropyl alcohol;
A second distillation step of distilling the reaction mixture from which the low-boiling compounds have been removed in the first distillation step in a distillation column to remove water to obtain isopropyl alcohol,
In the first distillation step, a method for producing isopropyl alcohol is provided in which the oxygen partial pressure in the bottom gas phase of the distillation column is controlled to 50 to 500 Pa.

  Among the above production methods, in the first distillation step, the top of the distillation column has a condensing part that condenses the gas and returns a part thereof to the distilling column, and the gas present in the gas phase of the condensing part is Using a distillation tower having a structure provided with a vent pipe for discharging, supplying an inert gas to the vent pipe so that the linear velocity in the discharge direction is 0.01 to 3.0 m / sec. Is a preferred embodiment for further suppressing the production of organic acid.

  The isopropyl alcohol composition of the present invention exhibits extremely good storage stability that there is almost no change (increase) in the organic acid concentration over time even during long-term storage for 30 days or longer. It can be suitably used as a drying liquid.

  Although the mechanism by which the isopropyl alcohol composition of the present invention exhibits good storage stability is not clear, the present inventors set the organic acid concentration within a specific range corresponding to the dissolved oxygen of isopropyl alcohol. Therefore, it is presumed that the reaction in which an organic acid is generated from dissolved oxygen and unavoidable impurities can be prevented, and the generation of a new organic acid is prevented.

It is a schematic diagram which shows an example of the manufacturing method of the isopropyl alcohol of this indication. It is a figure which shows the time-dependent change of the density | concentration of an organic acid about the isopropyl alcohol of Examples 1-3 and the comparative example 1. FIG.

<Isopropyl alcohol composition>
The isopropyl alcohol composition of the present disclosure is a high-purity isopropyl alcohol composition composed of isopropyl alcohol and impurities (unavoidable impurities, trace impurities), and the dissolved oxygen concentration is an oxygen saturation solubility at 25 ° C. in the atmosphere. And the concentration of the organic acid as an impurity is 20 ppb or less on a mass basis.

  In the present disclosure, the dissolved oxygen concentration (%) of the isopropyl alcohol composition was measured by measuring the oxygen partial pressure corresponding to the dissolved oxygen present in the solution at 25 ° C. of the isopropyl alcohol composition to be measured. The value obtained by dividing the oxygen partial pressure by the oxygen partial pressure at 25 ° C. in the atmosphere is expressed in%.

  Here, under air means under an air composition of 1 atm. In addition, the oxygen partial pressure at 25 ° C. in the atmosphere means the oxygen partial pressure in air at 25 ° C. and 1 atm, and is 21 kPa. In the present disclosure, the oxygen saturation solubility at 25 ° C. in the atmosphere is the oxygen concentration when the dissolved oxygen is in an equilibrium state in an atmosphere of 1 atm and an oxygen partial pressure of 21 kPa.

  The oxygen partial pressure corresponding to the dissolved oxygen concentration of the isopropyl alcohol composition can be measured using an oxygen concentration meter (ORBISPHERE 510 gas analyzer (trade name) manufactured by Hack Ultra, Inc.) described later.

  In the present disclosure, the dissolved oxygen concentration of the isopropyl alcohol composition is not displayed as an absolute value, but as described above, the dissolved oxygen concentration is displayed as a relative value when the oxygen saturation solubility is 100%. Can be displayed accurately. In addition, when oxygen saturation solubility is confirmed by literature, various different values are shown by literature. From this, it is understood that when the dissolved oxygen concentration is displayed as an absolute value, the dissolved oxygen concentration cannot be accurately displayed.

  It is important that the isopropyl alcohol composition of the present disclosure has a dissolved oxygen concentration of 0.1% or less with respect to an oxygen saturation solubility at 25 ° C. in the atmosphere. By adjusting the dissolved oxygen concentration to the above range, it is possible to effectively suppress the change with time of the concentration of the organic acid as an impurity by working together with the adjustment of the concentration of the organic acid described later. The dissolved oxygen concentration is preferably 0.075% or less with respect to the oxygen saturation solubility at 25 ° C. in the air, and more preferably 0.05% with respect to the oxygen saturation solubility at 25 ° C. in the air. It is as follows.

  Moreover, in this indication, the density | concentration of the organic acid in an isopropyl alcohol composition is a density | concentration of the total amount of the organic acid identified by the ion chromatography method shown by the Example. For example, in the examples described later, formic acid, acetic acid, and propionic acid are identified as organic acids, and the concentration of the organic acid is indicated by the total amount of the identified organic acids.

  In the present disclosure, the concentration of the organic acid as an impurity is 20 ppb or less, preferably 5 ppb or less on a mass basis. The lower limit is not particularly limited, and may be, for example, 0.1 ppb or more. As described above, by adjusting the organic acid to a specific range, it is possible to effectively reduce the change over time in the concentration of the organic acid as an impurity by acting together with the reduction of dissolved oxygen.

  In this disclosure, the mechanism by which the change with time of the organic acid is suppressed is not clear, but the reaction of generating the organic acid from dissolved oxygen and inevitable impurities can be prevented, and the generation of a new organic acid is effective. It is estimated that the That is, this is an effect exhibited by adjusting not only the dissolved oxygen but also the organic acid to a specific range, and there has been no isopropyl alcohol composition that exhibits such an effect.

In addition, the isopropyl alcohol composition of the present disclosure includes a high-boiling compound as an impurity having a boiling point higher than that of isopropyl alcohol and having the carbon number of 4 or more excluding the organic acid in the production process ( Hereinafter, it is simply referred to as “high boiling point compound”). When the high boiling point compound is contained in a large amount, when used as a cleaning liquid or a drying liquid for a semiconductor device, the high boiling point compound may remain or adhere to the surface of the semiconductor device, thereby reducing the yield of the semiconductor device. Therefore, it is preferable that the concentration of such a high boiling point compound is 20 ppb or less on a mass basis.
In the present disclosure, the concentration of the high boiling point compound is a value measured using a gas chromatography method as shown in Examples, and the detection lower limit of each high boiling point compound is 20 ppb.

  High boiling compounds that may be present in the isopropyl alcohol composition of the present disclosure include 2-methyl-3-pentanone, 3-methyl-2-pentanone, 4-methyl-2-pentanone, 2-hexanone, 3 , 3-dimethyl-2-butanol, 2,3-dimethyl-2-butanol, 2-methyl-2-pentanol, 3-methyl-3-pentanol, 2-methyl-3-pentanol, 3-hexanol, 4-methyl-2-pentanol, 3-methyl-2-pentanol, 2,2-dimethyl-1-butanol, 2-hexanol, 2-ethyl-1-pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 1-hexanol, 4-methyl-1-pentanol, 1,2-propanediol, 2-methyl-2,4-pentanedio Le, and the like. In particular, the concentrations of 4-methyl-2-pentanol, 2-methyl-3-pentanone, and 4-methyl-2-pentanone are preferably 20 ppb or less on a mass basis.

  Furthermore, in the isopropyl alcohol composition of the present disclosure, the concentration of moisture as an impurity is preferably 20 ppm or less on a mass basis. Since the moisture contained in the isopropyl alcohol composition as well as the high boiling point compound may reduce the yield of the semiconductor device, the moisture concentration is preferably 20 ppm or less on a mass basis.

  The isopropyl alcohol composition of the present disclosure has excellent storage stability since the dissolved oxygen concentration and the organic acid concentration are reduced. If the isopropyl alcohol composition of the present disclosure is filled in an airtight container and sealed with an inert gas (generally nitrogen gas), for example, even if it is left for 30 days, dissolved oxygen and organic acid change with time is extremely small. The isopropyl alcohol composition of the present disclosure is excellent in transportability and storage properties, and can be suitably used as a cleaning liquid or a drying liquid for semiconductor devices.

<Method for producing isopropyl alcohol>
The method for producing isopropyl alcohol of the present disclosure (hereinafter also referred to as “the method of production of the present disclosure”) is a method for producing isopropyl alcohol by directly hydrating water to propylene. As shown in FIG. It comprises a supply step, a reaction step, a recovery step, a first distillation step, and a second distillation step. Hereinafter, each step will be described in detail.

[Raw material supply process]
The raw materials used in the production method of the present disclosure are propylene and water. As shown in FIG. 1, propylene as a raw material is received in a recovery tank, mixed with propylene separated in the recovery process, and supplied to the reactor. Similarly, the raw material water is received in the recovery tank, and the water recovered in the second distillation step is mixed in the recovery tank and supplied to the reactor.

  In the production method of the present disclosure, propylene having a purity of 95% by mass or more that is generally available as an industrial product can be used as propylene as a raw material. When unsaturated hydrocarbon compounds such as ethylene, butene, pentene, hexene and the like are contained in propylene, they undergo hydration reaction in the reaction step and become impurities. Therefore, it is preferable that the purity of propylene as a raw material is high.

  In the production method of the present disclosure, the concentration of dissolved oxygen contained in propylene and water as raw materials is not particularly limited. Even if dissolved oxygen was contained in the raw material propylene and water up to the saturated dissolved oxygen concentration at each temperature and pressure, as described later, it was provided below the supply stage of the distillation column in the first distillation step. This is because by supplying the inert gas from the inert gas supply nozzle, the dissolved oxygen is discharged out of the system, and the dissolved oxygen contained in the reaction product isopropyl alcohol is controlled to a low concentration.

  In the raw material supply step, an acid catalyst required in the reaction step is added in advance to the raw material water and supplied to the reactor. Examples of the acid catalyst include acid catalysts of various polyanions such as a molybdenum-based inorganic ion exchanger and a tungsten-based inorganic ion exchanger. An acid catalyst may be used individually by 1 type, and may use 2 or more types together. Among these acid catalysts, at least one selected from the group consisting of phosphotungstic acid, silicotungstic acid, and silicomolybdic acid is preferable from the viewpoint of reaction activity.

  The addition amount of the acid catalyst is adjusted so that the pH of the raw material water is confirmed with a pH meter and the pH at 25 ° C. is 2.5 to 4.5. When the measured pH is less than 2.5, the pH can be easily adjusted by adding an alkali such as sodium hydroxide. Moreover, when pH exceeds 4.5, pH can be easily adjusted by adding an acid catalyst.

  If an acid catalyst is added so that the pH of the raw material water is in the range of 2.5 to 4.5, it is optimal for obtaining a high selectivity to isopropyl alcohol while maintaining a high conversion of propylene. It becomes possible to set it as reaction conditions, and it becomes reaction conditions with few production | generation of impurities, especially an organic acid and a high boiling point compound. Moreover, since it can suppress the corrosion of the piping and reactor by an acid if it adjusts to such a pH range, the density | concentration of the metal ion contained in isopropyl alcohol can also be suppressed.

[Reaction process]
The direct hydration reaction of propylene in the reaction step can be represented by the following formula. The following reaction is performed in the reactor to obtain a reaction mixture.
C ₃ H ₆ + H ₂ O → CH ₃ CH (OH) CH ₃

  As reaction conditions, for example, the reaction pressure is preferably 150 to 250 atm and the reaction temperature is preferably 200 to 300 ° C. When the reaction conditions satisfy this range, the yield of industrial production and the durability of the acid catalyst tend to be compatible while suppressing the production of by-products.

  In the direct hydration reaction of propylene in the reaction step, 1 mol of isopropyl alcohol is generated from 1 mol of propylene and 1 mol of water, as shown in the above chemical reaction formula. For this reason, normally, propylene and water may be equivalent amounts, but in the production method of the present disclosure, it is preferable to make water excessive with respect to propylene. Specifically, it is preferable to make water 1300-2100 mass parts with respect to 100 mass parts of propylene. By making the ratio of propylene and water in the reactor within the above range, the production of propylene oligomers can be suppressed and the yield of isopropyl alcohol tends to be increased. In addition, the production efficiency of isopropyl alcohol tends to be increased. The amount of water relative to 100 parts by mass of propylene is more preferably 1500 to 2000 parts by mass.

  Further, in the production method of the present disclosure, in order to improve both the concentration and purity of isopropyl alcohol in the reaction mixture obtained by the reaction step, the residence time of water in the reactor is more than 20 minutes and 50 minutes or less. It is preferable. The water staying time is more preferably 25 to 40 minutes, and further preferably 30 to 40 minutes.

In addition, the residence time of water in the present disclosure is a time defined by the following formula, and can be appropriately changed by changing the supply amount of water as a raw material and the volume of the reactor.
Water residence time (min) = reactor volume (m ³ ) ÷ water supply (m ³ / min)

  Since the reaction in the reactor in the present disclosure is performed under high temperature and high pressure, the density of water is unknown. For this reason, the supply amount of water is calculated on the basis of the flow rate of water (110 ° C. in the examples described later) supplied into the reactor.

[Recovery process]
The isopropyl alcohol produced | generated at said reaction process is extracted from a reactor in the state melt | dissolved in the water phase. Then, in the recovery step, the pressure and temperature are lowered, unreacted propylene dissolved in the aqueous phase is separated as a gas, and the reaction mixture containing isopropyl alcohol is recovered. A known technique established as a separator for unreacted propylene can be applied to this step. The separated propylene is re-introduced into the propylene recovery tank in the raw material supply step and reused as a raw material.

[First distillation step]
In the first distillation step, distillation is performed for the purpose of removing low-boiling compounds having a boiling point lower than that of isopropyl alcohol from the reaction mixture containing isopropyl alcohol obtained in the recovery step and reducing dissolved oxygen. Perform the operation.

  The production method of the present disclosure is characterized in that, in the first distillation step, the oxygen partial pressure in the bottom gas phase part of the distillation column is controlled to 50 to 500 Pa. Here, the column bottom gas phase portion is a gas phase portion in equilibrium with the column bottom liquid of the distillation column, and refers to a gas phase portion from the column bottom liquid to the first stage shelf. Moreover, the bottom liquid of the distillation column in the first distillation step is a bottom liquid from which a low boiling point compound of 50 ° C. or less has been removed by distillation operation.

  When the partial pressure of oxygen in the gas phase at the bottom exceeds 500 Pa, oxygen is taken into the bottom liquid, and dissolved oxygen is brought into the steps after the second distillation step. It tends to be difficult to reduce. On the other hand, if the oxygen partial pressure in the gas phase at the bottom of the column is less than 50 Pa, it is possible to reduce the oxygen taken into the bottom liquid, but it is inactive to reduce the oxygen partial pressure in the distillation column. A large amount of gas must be supplied. When a large amount of inert gas is supplied, the gas load of the distillation column in the first distillation step increases. An increase in gas load leads to a decrease in the stable operation area of the distillation column and a decrease in the processing capacity of the condenser with the accumulation of inert gas in the condenser that cools the top gas. Since the capacity is reduced, it is not preferable from the viewpoint of economic efficiency.

  It should be noted that dissolved oxygen in isopropyl alcohol can be reduced by controlling the oxygen partial pressure in the bottom gas phase of the distillation column to 50 to 500 Pa, but the oxygen partial pressure in the bottom gas phase of the distillation tower is 50. By controlling to ~ 200 Pa, dissolved oxygen can be further reduced.

  In order to control the oxygen partial pressure in the gas phase section at the bottom of the distillation column to 50 to 500 Pa, for example, an inert gas supply nozzle is provided below the supply stage of the distillation tower, preferably at the bottom of the tower, An inert gas may be supplied to control the oxygen partial pressure in the tower bottom gas phase.

More specifically, the inert gas is supplied from an inert gas supply nozzle provided at the bottom of the distillation column to 0.05 to 5 Nm ³ -inert gas / m ³ -liquid load, preferably ^{3 to 5} Nm ^3-. By supplying with an inert gas / m ³ -liquid load, it becomes possible to control the oxygen partial pressure in the bottom gas phase part of the distillation column to 50 to 500 Pa, preferably 50 to 200 Pa.

  In the present disclosure, the inert gas is a gas other than oxygen that does not react with isopropyl alcohol and does not liquefy at the refrigerant temperature used in the condensing unit, and examples thereof include hydrogen, nitrogen, helium, and argon. Among these inert gases, nitrogen, helium, and argon having low reactivity are preferable from the viewpoint of safety, and nitrogen is more preferable from the viewpoint of economy.

Here, the liquid load in the distillation tower is the sum of the liquid volume (m ³ / hour) supplied to the distillation tower and the reflux liquid volume (m ³ / hour) refluxed to the top of the tower. The amount of the supply liquid and the amount of the reflux liquid vary depending on the production amount and the set reflux ratio of the distillation tower. However, even if the amount of the supply liquid and the amount of the reflux liquid varies, the amount of the inert gas supplied is 0.05 to 5 Nm. ³ - inert gas / m 3 ^- is controlled so that the liquid load, the oxygen partial pressure of the bottom gas phase portion of the distillation column can be controlled to 50 to 500 Pa.

  The oxygen partial pressure in the gas phase at the bottom of the column is calculated from the dissolved oxygen concentration by measuring the dissolved oxygen concentration in the bottom liquid of the distillation column. According to Henry's law, the dissolved oxygen concentration in the bottom liquid is proportional to the partial pressure in the gas phase, so as described above, the dissolved oxygen is converted into the partial pressure of oxygen in the gas phase in equilibrium with the liquid phase. it can. And since the gas phase in equilibrium with the tower bottom liquid is the tower bottom gas phase part, the oxygen partial pressure measured by converting dissolved oxygen in the tower bottom liquid is the oxygen partial pressure in the tower bottom gas phase part. Can be considered the same. For example, if the measurement result obtained by converting the dissolved oxygen concentration of the column bottom liquid into an oxygen partial pressure is 21 Pa, the oxygen partial pressure in the column bottom gas phase is 21 Pa.

  Further, in the production method of the present disclosure, in the first distillation step, the top of the distillation column has a condensing part that condenses gas and returns a part thereof to the distilling column, and a vent pipe is provided in the gas phase of the condensing part Is preferably used so that the linear velocity in the discharge direction in the vent pipe is 0.01 to 3.0 m / sec. In the vent pipe provided in the condensing part of the distillation tower. May supply an inert gas so that it may become 0.04-2.5 m / sec. By setting the supply amount of such an inert gas, the condensing unit becomes negative pressure due to a disturbance such as a rapid temperature change of the refrigerant used in the condensing unit and a rapid increase in the amount of liquid supplied to the distillation column. Even when it becomes, it becomes possible to prevent the outside air containing oxygen from flowing back through the vent pipe. Thereby, oxygen contained in the outside air is not dissolved in the reaction mixture containing isopropyl alcohol, and an increase in the dissolved oxygen concentration of isopropyl alcohol can be prevented.

  The condensing unit has a condenser that condenses the column top gas provided at the top of the distillation column and a reflux tank that receives the condensed liquid. Known condensation conditions can be used in the condensing section. Generally, if the condensation temperature in the condenser is about 5 ° C. lower than the top temperature of the distillation tower, It can be judged that it is fully condensed. For example, if the tower top temperature is 35 ° C., the condensation temperature may be set to 30 ° C. Since the reflux ratio hardly affects the dissolved oxygen concentration of isopropyl alcohol, the liquid composition of the reaction mixture containing isopropyl alcohol obtained in the distillation column may be set based on the target purity.

  The vent pipe is a degassing pipe for preventing a pressure rise inside the distillation tower provided at the top of the distillation tower, and is a pipe provided in the gas phase of the condensation section of the distillation tower. The vent pipe connects the inside of the distillation tower and the outside air outside the distillation tower, and through the vent pipe, gases such as inert gas and low-boiling-point compounds staying at the top of the distillation tower are discharged out of the system.

  The present inventors assume the following mechanism as a reason for controlling the oxygen partial pressure in the bottom gas phase of the distillation column. In the first distillation step, the reaction mixture is extracted from the bottom of the column and supplied to the second distillation step. In the second distillation step, the reaction mixture containing isopropyl alcohol is further purified. Therefore, in order to reduce the dissolved oxygen concentration in the reaction mixture obtained from the bottom of the distillation column in the first distillation step, the oxygen partial pressure in the bottom gas phase in equilibrium with the bottom liquid in the bottom is reduced. What is necessary is just to control to a specific range.

  As a means for controlling the oxygen partial pressure in the gas phase at the bottom of the column to a specific range, an operation of supplying an inert gas below the supply stage of the distillation column, preferably from the column bottom can be mentioned. The supply of the inert gas is considered to replace the oxygen in the bottom gas phase with the supplied inert gas. Furthermore, by controlling the oxygen partial pressure within the above-described range, all of them can be achieved without substantially reducing the yield of the reaction mixture, reducing the capacity of the condensing unit, and increasing the gas load in the distillation column. Is considered possible.

  In addition, in order to control the oxygen partial pressure of the bottom gas phase part of the first distillation step to 50 to 500 Pa, it is inert to a part other than the lower part than the supply stage of the distillation tower, for example, the top part of the distillation tower or the condensing part. Although it is possible to adjust the partial pressure of oxygen in the gas phase at the bottom of the column by supplying gas, it is not preferable because it is separated from the bottom of the column and the efficiency of substitution with an inert gas is low.

[Second distillation step]
In the second distillation step, a distillation operation is performed for the purpose of removing water from the reaction mixture from which the low-boiling compounds have been removed in the first distillation step to obtain isopropyl alcohol. The azeotropic temperature of water and isopropyl alcohol is 80.1 ° C., and in the second distillation step, water is removed from the reaction mixture obtained from the bottom liquid of the first distillation step to obtain about 12% by mass of water. The operation of extracting isopropyl alcohol containing sucrose is performed. The isopropyl alcohol containing water extracted from the top of the second distillation step is further dehydrated as necessary. On the other hand, water is extracted from the bottom of the tower and collected.

  In the water recovered in the second distillation step, the low boiling point compound having a lower boiling point than that of isopropyl alcohol is removed in the first distillation step of the previous step, and can be suitably used as a raw material for isopropyl alcohol. The recovered water is reintroduced into the water recovery tank in the raw material supply step and reacted with propylene, whereby isopropyl alcohol with reduced impurities can be produced.

  In the second distillation step, it is preferable to control the oxygen partial pressure in the gas phase at the bottom of the distillation column because dissolved oxygen introduced into the product can be further reduced. Also in the second distillation step, dissolved oxygen can be reduced similarly to the first distillation step by controlling the oxygen partial pressure in the bottom gas phase part of the distillation column.

  In the second distillation step, an inert gas may be supplied to the vent pipe as in the first distillation step. Also in the second distillation step, it is possible to suppress an increase in dissolved oxygen in the manufacturing process by adopting the same conditions as in the first distillation step.

[Other processes]
The isopropyl alcohol with reduced impurities obtained in the second distillation step can be made into isopropyl alcohol with further reduced impurities as well as dissolved oxygen through a dehydration step and a purification step. In addition to dehydration and purification, metals and inorganic particles may be removed by a filter process, or metal ions may be removed by an ion exchange resin tower. By removing impurities other than organic compounds after distillation, isopropyl alcohol that can be suitably used as a cleaning agent for electronic devices and the like can be produced.

  When transporting the produced isopropyl alcohol to a closed container such as a canister can, it can be stored more stably by carrying it out in an inert gas atmosphere such as nitrogen gas. Can be increased. Moreover, it is preferable to enclose the sealed container after the transfer with an inert gas such as nitrogen gas. In the isopropyl alcohol produced by the production method of the present disclosure, dissolved oxygen and organic acid are reduced in the production process. By adopting a method of filling and storing such a sealed container, dissolved oxygen and organic acid are used. Isopropyl alcohol can be stored in a state where the acid is reduced and the change with time is small.

  According to the above production method, not only dissolved oxygen but also organic acid can be reduced, and furthermore, isopropyl alcohol with little change with time of the organic acid can be industrially produced.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the following description, “%”, “ppm”, “ppb”, and “ppt” representing concentrations are all based on mass.

<Measurement method of dissolved oxygen>
In the present disclosure, the dissolved oxygen concentration of isopropyl alcohol and the partial pressure of oxygen in the gas phase at the bottom of the column are ORBISPHERE 510 gas analyzer O ₂ meter (trade name: sensor model 2952A DO2 measurement range ₂ ppb to 80 ppm, manufactured by Hack Ultra Co., Ltd. , PO2 measurement range 5 Pa to 200 kPa).

  Since the measured value is displayed as an oxygen partial pressure converted from dissolved oxygen in the solution, as described above, the measured value of the column bottom liquid is the same as the measured value of the column bottom liquid. The oxygen partial pressure of the part was adopted.

  Further, the dissolved oxygen concentration (%) of isopropyl alcohol was measured for the sampled isopropyl alcohol by measuring the partial pressure of oxygen corresponding to dissolved oxygen at 25 ° C. using the above apparatus, and the measurement result was 1 atm and 25 ° C. The value divided by 21 kPa, which is the oxygen partial pressure in the air, was calculated by displaying in%.

<Measurement method of organic acid>
In the present disclosure, the organic acid contained in isopropyl alcohol was measured by the ion chromatography method under the following measurement conditions.
-Measurement conditions-
Device name: ICS2100 (manufactured by Thermo Fisher Scientific) Anion analysis detector: Conductivity detector Column: IonPacAS18
Flow rate: 1 mL / min Temperature condition: 30 ° C
Gradient conditions: 2 mM, KOH → 15 min, 5 mM, KOH → 25 min, 40 mM, KOH → 40 min, 40 mM, KOH
Concentration column: UTAC-LP2
Injection volume: 20 mL
Detection lower limit: 100ppt

  In addition, as a compound used as the measuring object of organic acid, a compound other than the compound corresponding to the retention time of formic acid, acetic acid, propionic acid, butyric acid, and isobutyric acid was not detected in both Examples and Comparative Examples. Therefore, formic acid, acetic acid, propionic acid, butyric acid, and isobutyric acid were quantified from the chart obtained by measurement.

<Method for measuring moisture content>
In the present disclosure, moisture contained in isopropyl alcohol was measured using a coulometric titration type Karl Fischer moisture meter MKC-510 (moisture measurement range: 10 μg to 100 mg) manufactured by Kyoto Electronics Industry Co., Ltd.
(Anolyte: Hydronal Coulomat AG, Catholyte: Hydronal Coulomat CG)

<Measurement method of acetone>
In the present disclosure, acetone contained in isopropyl alcohol was measured by the gas chromatography method under the following measurement conditions.
-Measurement conditions-
Device name: Agilent 890B GC system (manufactured by Agilent Technologies)
Inlet temperature: 200 ° C
Column: DB-WAX (inner diameter 0.25 mm, length 30 m, film thickness 0.25 μm)
Detector: Mass spectrometer transfer line Temperature: 240 ° C
SIM monitor ion: 58
Oven temperature: 35 ° C. Fixed injection volume: 1 μL
Split ratio: 10: 1

<Measurement method of high boiling point compound>
[Qualitative analysis]
In the present disclosure, the high boiling point compound contained in isopropyl alcohol was measured by the gas chromatography method under the following measurement conditions.
-Measurement conditions-
Device name: 7890A / 5975C (manufactured by Agilent Technologies)
Analytical column: SUPELCO WAX-10 (inner diameter 0.25 mm, length 60 m, film thickness 0.25 μm)
Column temperature: 35 ° C. (2 minutes hold) → Temperature rise at 5 ° C./min→100° C. → Temperature rise at 10 ° C./min→240° C. (hold 6 minutes)
Carrier gas: Helium carrier gas Flow rate: 2 mL / min Inlet temperature: 240 ° C
Sample injection method: Pulse pressure during pulsed splitless injection: 90 psi (2 minutes)
Split vent flow: 50 mL / min (2 min)
Use gas saver: 20 mL / min (5 min)
Transfer line temperature: 240 ° C
Ion source, quadrupole temperature: 230 ° C, 150 ° C
Scan ion: m / Z = 25-250

[Quantitative analysis]
When a peak was confirmed in the chart obtained according to the above qualitative analysis method, a library search was performed from the mass spectrum of the peak, and the structure was specified. Next, a standard substance of the specified high boiling point compound is prepared, and the concentration of the high boiling point compound detected in the qualitative analysis is selected by the selected ion detection method (SIM) by comparing with the peak area of the standard substance quantified in advance. ).
-SIM monitor ion-
Group 1 Start time: 12.7 minutes, m / Z: 31, 43, 75 (Dwell 60)
Group 2 Start time: 13.5 minutes, m / Z: 45, 56, 75, 59 (Dwell 45)
Group 3 Start time: 16.0 minutes, m / Z: 42, 43, 56 (Dwell 60)
Group 4 Start time: 22.0 minutes, m / Z: 45, 56, 59, 72 (Dwell 45)

<Concentration method>
Since the isopropyl alcohol of the present disclosure has reduced impurities, it is necessary to concentrate the isopropyl alcohol to be measured as necessary to improve the analysis accuracy. Although the concentration method is shown below, if necessary, the following operation may be repeated to change the concentration ratio. As a concentration condition of the high-boiling compounds, for example, distillation is performed for 24 hours with a precision distillation apparatus at a column top temperature of about 82 ° C. The number of theoretical plates in the precision distillation apparatus is 2 to 30. If the number of plates is within this range, distillation and concentration can be performed.

  In addition, it can be concentrated 76 times by distilling at about 82 ° C. for 24 hours. Further, in order to prevent the oxidation of the analysis object, it is preferable that nitrogen be circulated in advance in the precision distillation apparatus to create an inert atmosphere. Further, during the distillation, it is preferable that nitrogen be circulated also in a liquid pool portion for storing the distillate after distillation and distilled in an inert atmosphere.

<Example 1>
[Production of isopropyl alcohol]
As a raw material propylene, what contained 39972 ppm propane, 20 ppm ethane, 8 ppm butene, 0.1 ppm or less pentene, and 0.1 ppm or less hexene as impurities was prepared. Moreover, as raw material water, water whose pH was adjusted to 3.0 by adding phosphotungstic acid as an acid catalyst was prepared.
According to the production process shown in FIG. 1, a reactor having an internal volume of 10 L is supplied with water heated to 110 ° C. at a supply rate of 18.4 kg / hour (since the density is 920 kg / m ³ , 20 L / hour). At the same time, propylene was added at a supply rate of 1.2 kg / hour (raw material supply step).

  The residence time of water in the reactor at this time is 30 minutes, and 1500 parts by mass of water is supplied to 100 parts by mass of propylene. Propylene and water were reacted at a reaction temperature in the reactor of 280 ° C. and a reaction pressure of 250 atm to obtain isopropyl alcohol (reaction step).

  Next, the reaction product containing isopropyl alcohol generated in the reaction step is cooled to 140 ° C., and the pressure is reduced to 18 atm, whereby propylene dissolved in water contained in the reaction product is recovered as a gas (recovery). Process). The recovered propylene was put into a propylene recovery tank for reuse as a raw material.

  At this time, the conversion rate of the supplied propylene was 84.0%, the selectivity of propylene to isopropyl alcohol was 99.2%, and the isopropyl alcohol concentration in the obtained reaction mixture was 7.8%.

Subsequently, the low boiling point compound which has a boiling point lower than the boiling point of isopropyl alcohol was removed from the reaction mixture after propylene collection | recovery using the distillation tower (1st distillation process). During the distillation, nitrogen was supplied from an inert gas supply nozzle provided at the bottom of the distillation column so that 4.0 Nm ³ -inert gas / m ³ -liquid load. After supplying nitrogen, the dissolved oxygen concentration in the bottom liquid of the distillation tower was measured, and the partial pressure of oxygen in the gas phase at the bottom was calculated to be 56 Pa. After supplying nitrogen, nitrogen, which is an inert gas, was further supplied at a rate of 2.5 m / sec from a vent pipe provided in the condensing part of the distillation column.

Next, the reaction mixture was extracted from the bottom of the distillation column and separated into water and isopropyl alcohol using the distillation column (second distillation step).
The water extracted from the bottom of the column and recovered was placed in a water recovery tank for reuse as a raw material under conditions of a temperature of 110 ° C. and a pressure of 1.5 atm. Further, phosphotungstic acid was added and adjusted so that the pH of the recovered water was maintained at 3.0.
On the other hand, since isopropyl alcohol extracted from the top of the column contains about 12% of water, a distillation step for dehydration and a distillation step for purifying isopropyl alcohol were performed to obtain isopropyl alcohol.

[Measurement of dissolved oxygen]
The dissolved oxygen of the obtained isopropyl alcohol was measured according to the method described above. That is, the dissolved oxygen was measured at regular intervals using a dissolved oxygen meter, and the dissolved oxygen contained in the obtained isopropyl alcohol was quantified. The results are shown in Table 1. As shown in Table 1, the dissolved oxygen concentration of the obtained isopropyl alcohol was 0.02% with respect to the saturated solubility of dissolved oxygen.

[Measurement of organic acids]
The organic acid contained in the obtained isopropyl alcohol was measured according to the method described above. Organic acid was detected from the obtained chart, and the total amount of organic acid contained in isopropyl alcohol was quantified from each retention time. The results are shown in Table 2. As shown in Table 2, formic acid, acetic acid, and propionic acid were identified and the total amount was 4 ppb.

[Measurement of acetone]
Acetone contained in the obtained isopropyl alcohol was measured according to the method described above. The results are shown in Table 2. As shown in Table 2, acetone contained in isopropyl alcohol was 0.3 ppm.

[Measurement of moisture]
The moisture contained in the obtained isopropyl alcohol was measured according to the method described above. The results are shown in Table 2. As shown in Table 2, the moisture contained in isopropyl alcohol was 15 ppm.

[Measurement of high boiling point compounds]
When analyzed according to the qualitative analysis method described above, no peak was detected in a region where the retention time was longer than that of isopropyl alcohol. Next, the high boiling point compounds in isopropyl alcohol concentrated according to the above-described concentration method were analyzed by the above-described qualitative analysis method. Furthermore, in order to perform more detailed quantification on the peaks detected by qualitative analysis, analysis was performed according to the above-described quantitative analysis method using non-concentrated isopropyl alcohol. As a result, the concentrations of 4-methyl-2-pentanol, 2-methyl-3-pentanone, and 4-methyl-2-pentanone were all 20 ppb or less, which is the lower limit of detection.

  Other high boiling point compounds include 3-methyl-2-pentanone, 2-hexanone, 3,3-dimethyl-2-butanol, 2,3-dimethyl-2-butanol, 2-methyl-2-pentanol, 3-methyl-3-pentanol, 2-methyl-3-pentanol, 3-hexanol, 3-methyl-2-pentanol, 2,2-dimethyl-1-butanol, 2-hexanol, 2-ethyl-1- Pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 1-hexanol, 4-methyl-1-pentanol, 1,2-propanediol, and 2-methyl-2,4- As a result of analyzing pentanediol, it was 20 ppb or less, which is the lower limit of detection.

  As described above, in the isopropyl alcohol of Example 1 obtained by the production method of the present disclosure, not only dissolved oxygen but also organic acids were reduced. Furthermore, the isopropyl alcohol of Example 1 was allowed to stand for 30 days in a nitrogen atmosphere that is an inert gas, and then the organic acid, acetone, and moisture were measured. The results are shown in Table 3 and FIG. As shown in Table 3 and FIG. 2, the isopropyl alcohol of Example 1 did not change the concentration of organic acid, acetone, and moisture even after being left for 30 days.

<Example 2>
In the first distillation step, nitrogen is supplied from an inert gas supply nozzle provided at the bottom of the distillation column so that the load is 0.1 Nm ³ -inert gas / m ³ -liquid, and is supplied to the condensing part of the distillation column. Isopropyl alcohol was produced in the same manner as in Example 1 except that nitrogen, which was an inert gas, was supplied at a rate of 0.04 m / sec from the provided air pipe.

  In addition, after supplying nitrogen, the dissolved oxygen concentration of the column bottom liquid of the distillation column was measured, and when the oxygen partial pressure of the column bottom gas phase part was calculated, it was 300 Pa.

[Measurement of dissolved oxygen]
The dissolved oxygen of the obtained isopropyl alcohol was measured according to the method described above. That is, the dissolved oxygen was measured at regular intervals using a dissolved oxygen meter, and the dissolved oxygen contained in the obtained isopropyl alcohol was quantified. The results are shown in Table 1. As shown in Table 1, the dissolved oxygen concentration of the obtained isopropyl alcohol was 0.07% with respect to the saturated solubility of dissolved oxygen.

[Measurement of organic acids]
The organic acid contained in the obtained isopropyl alcohol was measured according to the method described above. Organic acid was detected from the obtained chart, and the total amount of organic acid contained in isopropyl alcohol was quantified from each retention time. The results are shown in Table 2. As shown in Table 2, formic acid, acetic acid, and propionic acid were identified and the total amount was 12 ppb.

[Measurement of acetone]
Acetone contained in the obtained isopropyl alcohol was measured according to the method described above. The results are shown in Table 2. As shown in Table 2, acetone contained in isopropyl alcohol was 0.2 ppm.

[Measurement of moisture]
The moisture contained in the obtained isopropyl alcohol was measured according to the method described above. The results are shown in Table 2. As shown in Table 2, the moisture contained in isopropyl alcohol was 15 ppm.

[Measurement of high boiling point compounds]
When analyzed according to the qualitative analysis method described above, no peak was detected in a region where the retention time was longer than that of isopropyl alcohol. Next, the high boiling point compounds in isopropyl alcohol concentrated according to the above-described concentration method were analyzed by the above-described qualitative analysis method. Furthermore, in order to perform more detailed quantification on the peaks detected by qualitative analysis, analysis was performed according to the above-described quantitative analysis method using non-concentrated isopropyl alcohol. As a result, the concentrations of 4-methyl-2-pentanol, 2-methyl-3-pentanone, and 4-methyl-2-pentanone were all 20 ppb or less, which is the lower limit of detection.

  Other high boiling point compounds include 3-methyl-2-pentanone, 2-hexanone, 3,3-dimethyl-2-butanol, 2,3-dimethyl-2-butanol, 2-methyl-2-pentanol, 3- Methyl-3-pentanol, 2-methyl-3-pentanol, 3-hexanol, 3-methyl-2-pentanol, 2,2-dimethyl-1-butanol, 2-hexanol, 2-ethyl-1-pentanol 2-methyl-1-pentanol, 3-methyl-1-pentanol, 1-hexanol, 4-methyl-1-pentanol, 1,2-propanediol, and 2-methyl-2,4-pentanediol As a result of the analysis, all were 20 ppb or less, which is the lower limit of detection.

  As described above, in the isopropyl alcohol of Example 2 obtained by the production method of the present disclosure, not only dissolved oxygen but also organic acids were reduced. Furthermore, the isopropyl alcohol of Example 2 was allowed to stand for 30 days in a nitrogen atmosphere that is an inert gas, and then the organic acid, acetone, and moisture were measured. The results are shown in Table 3 and FIG. As shown in Table 3 and FIG. 2, the isopropyl alcohol of Example 2 slightly increased the organic acid and acetone concentrations, but the organic acid did not exceed the target upper limit of 20 ppb even after being left for 30 days.

<Example 3>
In the first distillation step, isopropyl alcohol was produced in the same manner as in Example 2 except that the inert gas was not supplied from the vent pipe provided in the condensing part of the distillation column.

  In addition, after supplying nitrogen, the dissolved oxygen concentration of the column bottom liquid of a distillation column was measured, and when the oxygen partial pressure of the column bottom gas phase part was computed, it was 480 Pa.

[Measurement of dissolved oxygen]
The dissolved oxygen of the obtained isopropyl alcohol was measured according to the method described above. That is, the dissolved oxygen was measured at regular intervals using a dissolved oxygen meter, and the dissolved oxygen contained in the obtained isopropyl alcohol was quantified. The results are shown in Table 1. As shown in Table 1, the dissolved oxygen concentration of the obtained isopropyl alcohol was 0.09% with respect to the saturated solubility of dissolved oxygen.

[Measurement of organic acids]
The organic acid contained in the obtained isopropyl alcohol was measured according to the method described above. Organic acid was detected from the obtained chart, and the total amount of organic acid contained in isopropyl alcohol was quantified from each retention time. The results are shown in Table 2. As shown in Table 2, formic acid, acetic acid, and propionic acid were identified and the total amount was 15 ppb.

[Measurement of acetone]
Acetone contained in the obtained isopropyl alcohol was measured according to the method described above. The results are shown in Table 2. As shown in Table 2, acetone contained in isopropyl alcohol was 0.3 ppm.

[Measurement of moisture]
The moisture contained in the obtained isopropyl alcohol was measured according to the method described above. The results are shown in Table 2. As shown in Table 2, the moisture contained in isopropyl alcohol was 15 ppm.

[Measurement of high boiling point compounds]
When analyzed according to the qualitative analysis method described above, no peak was detected in a region where the retention time was longer than that of isopropyl alcohol. Next, the high boiling point compounds in isopropyl alcohol concentrated according to the above-described concentration method were analyzed by the above-described qualitative analysis method. Furthermore, in order to perform more detailed quantification on the peaks detected by qualitative analysis, analysis was performed according to the above-described quantitative analysis method using non-concentrated isopropyl alcohol. As a result, the concentrations of 4-methyl-2-pentanol, 2-methyl-3-pentanone, and 4-methyl-2-pentanone were all 20 ppb or less, which is the lower limit of detection.

  Other high boiling point compounds include 3-methyl-2-pentanone, 2-hexanone, 3,3-dimethyl-2-butanol, 2,3-dimethyl-2-butanol, 2-methyl-2-pentanol, 3- Methyl-3-pentanol, 2-methyl-3-pentanol, 3-hexanol, 3-methyl-2-pentanol, 2,2-dimethyl-1-butanol, 2-hexanol, 2-ethyl-1-pentanol 2-methyl-1-pentanol, 3-methyl-1-pentanol, 1-hexanol, 4-methyl-1-pentanol, 1,2-propanediol, and 2-methyl-2,4-pentanediol As a result of the analysis, all were 20 ppb or less, which is the lower limit of detection.

  As described above, in the isopropyl alcohol of Example 2 obtained by the production method of the present disclosure, not only dissolved oxygen but also organic acids were reduced. Further, the isopropyl alcohol of Example 3 was allowed to stand for 30 days in a nitrogen atmosphere that is an inert gas, and then the organic acid, acetone, and moisture were measured. The results are shown in Table 3 and FIG. As shown in Table 3 and FIG. 2, the concentration of the organic acid and acetone of the isopropyl alcohol of Example 3 slightly increased, but the organic acid did not exceed the target upper limit of 20 ppb even after being left for 30 days.

<Comparative Example 1>
Example 1 in the first distillation step, except that the inert gas nitrogen was not supplied from the inert gas supply nozzle provided at the bottom of the distillation column and the vent pipe provided at the condensing part of the distillation column. In the same manner, isopropyl alcohol was produced.

  In addition, it was 670 Pa when the dissolved oxygen concentration of the tower bottom liquid of a distillation tower was measured and the oxygen partial pressure of the tower bottom vapor phase part was computed.

[Measurement of dissolved oxygen]
The dissolved oxygen of the obtained isopropyl alcohol was measured according to the method described above. That is, the dissolved oxygen was measured at regular intervals using a dissolved oxygen meter, and the dissolved oxygen contained in the obtained isopropyl alcohol was quantified. The results are shown in Table 1. As shown in Table 1, the dissolved oxygen concentration of the obtained isopropyl alcohol was 0.13% with respect to the saturated solubility of dissolved oxygen.

[Measurement of organic acids]
The organic acid contained in the obtained isopropyl alcohol was measured according to the method described above. Organic acid was detected from the obtained chart, and the total amount of organic acid contained in isopropyl alcohol was quantified from each retention time. The results are shown in Table 2. As shown in Table 2, formic acid, acetic acid, and propionic acid were identified and the total amount was 26 ppb.

[Measurement of acetone]
Acetone contained in the obtained isopropyl alcohol was measured according to the method described above. The results are shown in Table 2. As shown in Table 2, acetone contained in isopropyl alcohol was 0.3 ppm.

[Measurement of moisture]
The moisture contained in the obtained isopropyl alcohol was measured according to the method described above. The results are shown in Table 2. As shown in Table 2, the moisture contained in isopropyl alcohol was 16 ppm.

[Measurement of high boiling point compounds]
When analyzed according to the qualitative analysis method described above, no peak was detected in a region where the retention time was longer than that of isopropyl alcohol. Next, the high boiling point compounds in isopropyl alcohol concentrated according to the above-described concentration method were analyzed by the above-described qualitative analysis method. Furthermore, in order to perform more detailed quantification on the peaks detected by qualitative analysis, analysis was performed according to the above-described quantitative analysis method using non-concentrated isopropyl alcohol. As a result, the concentrations of 4-methyl-2-pentanol, 2-methyl-3-pentanone, and 4-methyl-2-pentanone were all 20 ppb or less, which is the lower limit of detection.

  Other high boiling point compounds include 3-methyl-2-pentanone, 2-hexanone, 3,3-dimethyl-2-butanol, 2,3-dimethyl-2-butanol, 2-methyl-2-pentanol, 3- Methyl-3-pentanol, 2-methyl-3-pentanol, 3-hexanol, 3-methyl-2-pentanol, 2,2-dimethyl-1-butanol, 2-hexanol, 2-ethyl-1-pentanol 2-methyl-1-pentanol, 3-methyl-1-pentanol, 1-hexanol, 4-methyl-1-pentanol, 1,2-propanediol, and 2-methyl-2,4-pentanediol As a result of the analysis, all were 20 ppb or less, which is the lower limit of detection.

  As described above, in Comparative Example 1, acetone and moisture could be reduced to the same extent as in Examples 1 to 3, but dissolved oxygen was 0.1% or less with respect to the saturation solubility at 25 ° C. I couldn't. Also, the organic acid concentration could not be reduced to 20 ppb or less.

  Furthermore, the isopropyl alcohol of Comparative Example 1 was allowed to stand for 30 days in a nitrogen atmosphere that is an inert gas, and then the organic acid, acetone, and moisture were measured. The results are shown in Table 3 and FIG. As shown in Table 3 and FIG. 2, when the isopropyl alcohol of Comparative Example 1 was allowed to stand for 30 days, the concentrations of organic acid and acetone increased greatly.

  The disclosure of Japanese application 2017-9605 filed on January 23, 2017 is incorporated herein by reference in its entirety.

Claims (5)

An isopropyl alcohol composition comprising isopropyl alcohol and impurities,
An isopropyl alcohol composition having a dissolved oxygen concentration of 0.1% or less with respect to an oxygen saturation solubility at 25 ° C. in the atmosphere, and an organic acid concentration as an impurity of 20 ppb or less on a mass basis.   The concentration of the high boiling point compound as an impurity having a boiling point higher than that of isopropyl alcohol and excluding the organic acid and having 4 or more carbon atoms is 20 ppb or less on a mass basis. The isopropyl alcohol composition described.   The isopropyl alcohol composition according to claim 1 or 2, wherein the concentration of moisture as an impurity is 20 ppm or less on a mass basis. A method for producing isopropyl alcohol in which water is directly hydrated into propylene to produce isopropyl alcohol,
A raw material supply step of supplying propylene and water having an acid catalyst dissolved therein and a pH adjusted to 2.5 to 4.5 to the reactor;
A reaction step of reacting propylene and water in the reactor;
A recovery step of separating unreacted propylene from the reaction mixture obtained in the reaction step and recovering a reaction mixture containing isopropyl alcohol;
A first distillation step of distilling the reaction mixture recovered in the recovery step in a distillation column to remove a low-boiling compound having a boiling point lower than that of isopropyl alcohol;
A second distillation step of distilling the reaction mixture from which the low-boiling compounds have been removed in the first distillation step in a distillation column to remove water to obtain isopropyl alcohol,
In the first distillation step, a method for producing isopropyl alcohol, wherein an oxygen partial pressure in a gas phase part at the bottom of a distillation column is controlled to 50 to 500 Pa.   In the first distillation step, a vent pipe for discharging a gas existing in the gas phase of the condensing part, having a condensing part at the top of the distillation tower for condensing the gas and returning a part thereof to the distillation tower The inert gas is supplied to the vent pipe so that the linear velocity in the discharge direction of the vent pipe is 0.01 to 3.0 m / sec. The manufacturing method of isopropyl alcohol of description.

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