TWI812945B - Isopropanol composition and method for producing isopropanol - Google Patents

Abstract

The present invention provides an isopropyl alcohol composition, which is composed of isopropyl alcohol and impurities. The dissolved oxygen concentration of the isopropyl alcohol composition is less than 0.1% in the atmosphere relative to the saturated solubility of oxygen at 25°C, and , the concentration of organic acids as impurities is 20 ppb or less on a mass basis. Furthermore, the present invention also provides a method for producing isopropyl alcohol, which can obtain isopropyl alcohol as described above.

Description

Isopropyl alcohol composition and method for producing isopropyl alcohol

The invention relates to an isopropyl alcohol composition and a manufacturing method of isopropyl alcohol.

Semiconductor devices can generally be manufactured by repeating film formation processes, etching processes, etc. to form elements and circuits. In recent years, in the process of seeking higher performance of semiconductor devices, the miniaturization and high integration of components and circuits have also been gradually developed. Therefore, the impact of the quality of chemicals used in film formation processes, etching processes, etc. on the yield of semiconductor devices cannot be ignored, and therefore there is a strong desire to improve the quality of chemicals.

For example, in the manufacturing steps of semiconductor devices, isopropyl alcohol (also known as 2-propanol) used as a cleaning liquid or drying liquid is strongly expected to be upgraded to a quality similar to ultrapure water. Isopropyl alcohol, which is currently highly refined for its manufacturing steps, is filled into stainless steel bottles and further sealed with nitrogen gas before being shipped and transported.

[Problem to be solved by the invention] However, the inventors of the present invention have confirmed that even if the above-mentioned high-level purification and sealing of nitrogen gas are carried out for sealed storage, the concentration of organic acids contained as impurities will still change when isopropyl alcohol is stored or transported. The question of rising time and place.

Organic acids contained as impurities in isopropyl alcohol are expected to cause various problems such as surface corrosion of semiconductor devices, so it is necessary to suppress changes in concentration over time.

In view of such previous situation, the problem to be solved by the present invention is to provide an isopropyl alcohol composition and a method for producing isopropyl alcohol in which an increase in the concentration of an organic acid over time is suppressed. [Technical means to solve problems]

In order to solve the above-mentioned problems, the present inventors have diligently conducted research and obtained the following findings: When the concentration of dissolved oxygen in isopropyl alcohol and the concentration of organic acids contained as impurities exceed a certain range, even if nitrogen gas is used, To seal isopropyl alcohol, the concentration of organic acids will still increase when stored or transported.

Furthermore, as a result of further research based on the above knowledge, it was found that in the production step of isopropyl alcohol, by not only reducing the concentration of dissolved oxygen in isopropyl alcohol, but also adjusting the concentration of organic acids contained as impurities to Within a specific range, it is possible to extremely effectively and successfully suppress an increase in the concentration of organic acids over time, leading to the completion of the present invention.

That is, according to the present invention, an isopropyl alcohol composition can be provided, which is composed of isopropyl alcohol and impurities. The dissolved oxygen concentration of the isopropyl alcohol composition in the atmosphere relative to the saturated solubility of oxygen at 25°C is 0.1% or less, and the concentration of organic acids as impurities is 20 ppb or less on a mass basis.

The above isopropyl alcohol composition preferably has a higher boiling point than the boiling point of isopropyl alcohol, and the concentration of high boiling point compounds as impurities, excluding the above organic acid, is 20 ppb or less on a mass basis. The high boiling point The number of carbon atoms in the compound is 4 or more.

Furthermore, in the isopropyl alcohol composition, the concentration of water as an impurity is preferably 20 ppm or less on a mass basis.

Furthermore, according to the present invention, a method for producing isopropyl alcohol can be provided, which involves directly hydrating water with propylene to produce isopropyl alcohol. The method includes the following steps: The raw material supply step supplies propylene and water into the reactor, the water has an acid catalyst dissolved and the pH has been adjusted to 2.5 to 4.5; A reaction step, which reacts propylene and water in the above-mentioned reactor; a recovery step that separates unreacted propylene from the reaction mixture obtained in the above reaction step and recovers the reaction mixture containing isopropyl alcohol; A first distillation step, which distills the reaction mixture recovered in the above recovery step in a distillation column to remove low-boiling compounds, which have a boiling point lower than the boiling point of isopropyl alcohol; and, In a second distillation step, the reaction mixture from which low-boiling compounds have been removed in the first distillation step is distilled in a distillation column to remove water and obtain isopropyl alcohol; and, In the above-mentioned first distillation step, the oxygen partial pressure in the gas phase portion at the bottom of the distillation tower is controlled to 50 to 500 Pa.

Among the above-mentioned production methods, in order to further suppress the generation of organic acids, a preferred aspect is to use the following distillation tower in the above-mentioned first distillation step, and the linear velocity in the conventional discharge direction is 0.01 to 3.0 m/sec. In this way, inert gas is supplied to the vent pipe; the distillation tower has a condensation part at the top of the distillation tower and has a structure equipped with a vent pipe; the condensation part condenses the gas and sends a part of the condensed gas back to the distillation tower ; The vent pipe is used to discharge the gas existing in the gas phase of the condensation part. [Effects of the invention]

The isopropyl alcohol composition of the present invention shows excellent storage stability with almost no change (increase) in the organic acid concentration over time even after long-term storage of 30 days or more. Therefore, it is suitable for use in the manufacturing steps of semiconductor devices. Suitable for use as a cleaning fluid or drying fluid.

Furthermore, although the mechanism by which the isopropyl alcohol composition of the present invention exhibits good storage stability is not yet clear, the inventors speculate that the reason is as follows: by setting the organic acid concentration to a specific value by dissolving oxygen corresponding to isopropyl alcohol. Within the range, it is possible to prevent the reaction of organic acids produced by dissolved oxygen and unavoidable impurities, thereby preventing the generation of new organic acids.

〈Isopropyl alcohol composition〉 The isopropyl alcohol composition of the present invention is a high-purity isopropyl alcohol composition, which is composed of isopropyl alcohol and impurities (inevitable impurities, trace impurities). The dissolved oxygen concentration of the isopropyl alcohol composition is The saturated solubility with respect to oxygen at 25° C. in the atmosphere is 0.1% or less, and the concentration of organic acids as impurities is 20 ppb or less on a mass basis.

In this specification, the dissolved oxygen concentration (%) of the isopropyl alcohol composition is expressed as the following value in percentage (%). This value is measured when the isopropyl alcohol composition as the measurement object exists at 25°C. The partial pressure of oxygen corresponding to the dissolved oxygen in the solution is then divided by the partial pressure of oxygen at 25°C in the atmosphere.

Here, under the atmosphere means under the air composition of 1 atmospheric pressure. Furthermore, the partial pressure of oxygen in the atmosphere at 25°C means the partial pressure of oxygen in air at 25°C and 1 atmosphere, which is 21 kPa. In addition, in this specification, the saturated solubility of oxygen at 25°C in the atmosphere refers to the oxygen concentration when the dissolved oxygen reaches an equilibrium state in an atmosphere with a pressure of 1 atmosphere and a partial pressure of oxygen 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 Hach Co., Ltd.) described below.

In this specification, the dissolved oxygen concentration of the isopropyl alcohol composition is not expressed as an absolute value, but as a relative value when the oxygen saturated solubility is set to 100%, as mentioned above, so the dissolved oxygen concentration can be accurately expressed. oxygen concentration. Furthermore, if the oxygen saturation concentration is confirmed based on literature, various values will be shown depending on the literature. From this, it can be understood that when the dissolved oxygen concentration is expressed as an absolute value, the dissolved oxygen concentration cannot be accurately expressed.

A very important point about the isopropyl alcohol composition of the present invention is that its dissolved oxygen concentration is less than 0.1% relative to the saturated solubility of oxygen at 25°C in the atmosphere. By adjusting the dissolved oxygen concentration to the above range and functioning together with the adjustment of the organic acid concentration described below, it is possible to effectively suppress changes in the concentration of the organic acid as an impurity over time. The concentration of dissolved oxygen is preferably 0.075% or less relative to the saturated solubility of oxygen at 25°C in the atmosphere, and more preferably 0.05% or less relative to the saturated solubility of oxygen at 25°C in the atmosphere.

In addition, in this specification, the concentration of the organic acid in the isopropyl alcohol composition is the concentration of the total amount of organic acids identified by the ion chromatography shown in the Examples. For example, in the examples described below, formic acid, acetic acid, and propionic acid are identified as organic acids, and the concentration of the organic acid is expressed as the total amount of the identified organic acids.

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

In this specification, the mechanism by which the change with time of organic acids is suppressed is not clear, but it is speculated that the reaction of organic acids produced by dissolved oxygen and unavoidable impurities can be prevented, thereby effectively suppressing new organic acids. Acid production. That is, this is an effect achieved by adjusting not only the dissolved oxygen but also the organic acid to a specific range. Conventionally, there is no isopropyl alcohol composition that can exert such an effect.

In addition, the isopropyl alcohol composition of the present invention has a higher boiling point than the boiling point of isopropyl alcohol in the production process, and in addition to the above-mentioned organic acid, high-boiling point compounds (hereinafter, as impurities) are inevitably present. Only called "high boiling point compounds"), the carbon number of the high boiling point compound is 4 or more. If the above-mentioned high boiling point compound is contained in a large amount, when used as a cleaning liquid or drying liquid for semiconductor devices, the high boiling point compound will remain or adhere to the surface of the semiconductor device, so there is a concern that the yield of the semiconductor device will be reduced. Therefore, the concentration of the high boiling point compound is preferably 20 ppb or less on a mass basis. Furthermore, in this specification, the concentration of high boiling point compounds is a value measured using gas chromatography, as shown in the examples, and the detection lower limit of each high boiling point compound is 20 ppb.

Examples of high-boiling compounds that may be present in the isopropyl alcohol composition of the present invention include: 2-methyl-3-pentanone, 3-methyl-2-pentanone, and 4-methyl-2-pentanone. , 2-hexanone, 3,3-dimethyl-2-butanol, 2,3-dimethyl-2-butanol, 2-methyl-2-pentanol, 3-methyl-3-pentanol Alcohol, 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-pentanediol, etc. In particular, it is preferable that the concentrations of 4-methyl-2-pentanol, 2-methyl-3-pentanone and 4-methyl-2-pentanone are all 20 ppb or less on a mass basis.

Furthermore, in the isopropyl alcohol composition of the present invention, it is preferable that the concentration of water as an impurity is 20 ppm or less on a mass basis. Like high-boiling compounds, moisture contained in the isopropyl alcohol composition may cause a decrease in the yield of semiconductor devices, so the concentration of moisture is preferably 20 ppm or less on a mass basis.

The isopropyl alcohol composition of the present invention has excellent storage stability because the concentration of dissolved oxygen and the concentration of organic acids are reduced. As long as the isopropyl alcohol composition of the present invention is filled into an airtight container and sealed with an inert gas (generally nitrogen gas), even if it is left for 30 days, there will be very little change over time in dissolved oxygen and organic acids. The isopropyl alcohol composition of the present invention is also excellent in transportability and storage properties, and can be suitably used as a cleaning liquid or drying liquid for semiconductor devices.

〈How to make isopropyl alcohol〉 The production method of isopropyl alcohol of the present invention (hereinafter also referred to as the "production method of the present invention") is a method of producing isopropyl alcohol by directly hydrating water with propylene. As shown in Figure 1, it includes raw materials It consists of a supply step, a reaction step, a recovery step, a first distillation step and a second distillation step. Each step is explained in detail below.

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

In the production method of the present invention, propylene used as a raw material can generally be propylene with a purity of 95% by mass or more that is commercially available as an industrial product. If propylene contains unsaturated hydrocarbon compounds such as ethylene, butene, pentene, and hexene, these compounds will undergo hydration reactions during the reaction step and become impurities. Therefore, it is preferable that the purity of the propylene used as the raw material is relatively high.

In the production method of the present invention, the concentration of dissolved oxygen contained in propylene and water used as raw materials is not particularly limited. Even if the propylene and water used as raw materials contain dissolved oxygen up to the saturated dissolved oxygen concentration at their respective temperatures and pressures, as will be described later, in the first distillation step, the distillation tower is disposed further than the supply section of the distillation column. The downstream inert gas nozzle supplies inert gas, so that the dissolved oxygen can be discharged out of the system, so the dissolved oxygen contained in the reaction product, that is, isopropyl alcohol, can still be controlled to a low concentration.

In the raw material supply step, the acid catalyst required in the reaction step is added to the raw material water in advance and supplied to the reactor. Examples of acid catalysts include various polyvalent anion (polyanion) acid catalysts such as molybdenum-based inorganic ion exchangers and tungsten-based inorganic ion exchangers. One type of acid catalyst may be used alone, or two or more types may be used in combination. Among these acid catalysts, from the viewpoint of reactivity, at least one selected from the group consisting of phosphotungstic acid, silicododecanoic acid, and siloxymolybdic acid is preferred.

The amount of the acid catalyst to be added is adjusted so that the pH of the raw material water becomes 2.5 to 4.5 at 25° C. after checking the pH value with a pH meter. When the measured pH is less than 2.5, the pH can be easily adjusted by adding a base such as sodium hydroxide. In addition, when the pH is greater than 4.5, the pH value can be easily adjusted by adding an acid catalyst.

As long as the acid catalyst is added so that the pH of the raw material water falls within the range of 2.5 to 4.5, a high propylene conversion rate can be maintained and a high isopropyl alcohol selectivity can be obtained, so it is optimal. Reaction conditions that produce less impurities, especially organic acids and high-boiling compounds. Furthermore, by adjusting the pH to such a range, corrosion of pipelines and reactors due to acid can be suppressed, and therefore the concentration of metal ions contained in isopropyl alcohol can also be suppressed.

[Reaction Step] The direct hydration reaction of propylene in the reaction step can be expressed by the following chemical reaction formula. The reaction mixture can be obtained by carrying out the following reaction in the reactor. C ₃ H ₆ +H ₂ O→CH ₃ CH(OH)CH ₃

As reaction conditions, for example, it is preferable to set the reaction pressure to 150 to 250 atm and the reaction temperature to 200 to 300°C. When the reaction conditions satisfy this range, the production of by-products can be suppressed, and the yield that can be used for industrial production and the durability of the acid catalyst tend to be balanced.

The direct hydration reaction of propylene in the reaction step, as shown in the above chemical reaction formula, can generate 1 mol of isopropyl alcohol from 1 mol (mol) of propylene and 1 mol of water. Therefore, it is usually sufficient to have equal amounts of propylene and water. However, in the production method of the present invention, it is preferable to use an excess amount of water relative to propylene. Specifically, it is preferable to set the water content to 1,300 to 2,100 parts by mass relative to 100 parts by mass of propylene. By setting the ratio of propylene and water in the reactor within the above range, the generation of propylene oligomers can be suppressed, and the yield of isopropyl alcohol tends to be increased. In addition, there is a tendency to increase the production efficiency of isopropyl alcohol. The amount of water relative to 100 parts by mass of propylene is more preferably 1,500 to 2,000 parts by mass.

In addition, the production method of the present invention can increase the concentration and purity of isopropyl alcohol in the reaction mixture obtained by the reaction step, so the residence time of water in the reactor is preferably set to more than 20 minutes and Under 50 minutes. The residence time of water is more preferably 25 to 40 minutes, further preferably 30 to 40 minutes.

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

Because the reaction in the reactor in this specification is carried out under high temperature and high pressure, the density of water is not clear. Therefore, the supply amount of water is calculated based on the flow rate of water (110° C. in Examples to be described later) supplied into the reactor.

[Recycling steps] The isopropyl alcohol produced in the above reaction step is taken out from the reactor in a state of being dissolved in the water phase. Furthermore, in the recovery step, the pressure and temperature are lowered, propylene dissolved in the water phase and unreacted is separated as a gas, and the reaction mixture containing isopropyl alcohol is recovered. In this step, a well-established and well-known technology as an unreacted propylene separator can be applied. The separated propylene can be put back into the propylene recovery tank in the raw material supply step and reused as raw material.

[First distillation step] The first distillation step is a distillation operation performed for the purpose of removing low-boiling-point compounds and reducing dissolved oxygen from the reaction mixture containing isopropanol obtained in the recovery step. Propanol has a lower boiling point.

The greatest feature of the manufacturing method of the present invention is that in the first distillation step, the oxygen partial pressure in the gas phase portion at the bottom of the distillation tower is controlled to 50 to 500 Pa. Here, the bottom gas phase portion means a gas phase portion that is in equilibrium with the bottom liquid of the distillation column, and is the gas phase portion from the bottom liquid to the first-stage tray. In addition, the so-called bottom liquid of the distillation tower in the first distillation step is the bottom liquid from which low-boiling point compounds of 50° C. or lower have been removed by the distillation operation.

When the oxygen partial pressure in the gas phase at the bottom of the tower is greater than 500Pa, it will be difficult to reduce the dissolved oxygen in isopropyl alcohol because oxygen will be dissolved in the bottom liquid and will cause dissolved oxygen in the steps after the second distillation step. Oxygen tendency. On the other hand, when the oxygen partial pressure in the gas phase at the bottom of the tower is less than 50 Pa, although the oxygen dissolved in the bottom liquid can be reduced, the oxygen partial pressure in the distillation tower will be reduced, so a large amount of inert gas must be supplied. If a large amount of inert gas is supplied, the gas load of the distillation tower in the first distillation step will be increased. The increase in gas load, along with the reduction of the stable operation area of the distillation tower and the accumulation of inert gas in the condenser that cools the tower gas, will cause the processing capacity of the condenser to decrease, which will in turn reduce the distillation capacity of the distillation tower. So it’s not good from an economic efficiency perspective.

Furthermore, as long as the oxygen partial pressure at the bottom gas phase of the distillation tower is controlled at 50 to 500 Pa, the dissolved oxygen in isopropyl alcohol can be reduced. However, by controlling the oxygen partial pressure at the bottom gas phase of the distillation tower at 50~200Pa can further reduce the dissolved oxygen.

In order to control the oxygen partial pressure in the gas phase part at the bottom of the distillation tower to 50 to 500 Pa, for example, the inert gas supply nozzle is provided further downstream than the supply section of the distillation tower, preferably at the bottom of the tower, and then from This nozzle only needs to supply inert gas to control the oxygen partial pressure in the gas phase at the bottom of the tower.

More specifically ^, the liquid load is 0.05 to 5 Nm ³ -inert gas/m 3 -, preferably 3 to 5 Nm ³ -inert gas/m ³ - from an inert gas supply nozzle provided at the bottom of the distillation tower. By supplying inert gas with a liquid load, the oxygen partial pressure at the bottom gas phase of the distillation tower can be controlled to 50 to 500 Pa, preferably 50 to 200 Pa.

In this specification, the so-called inert gas refers to a gas other than oxygen that does not react with isopropyl alcohol and does not liquefy at the temperature of the refrigerant used in the condensation part. Examples thereof include: hydrogen, nitrogen, helium, Argon etc. Among these inert gases, nitrogen gas, helium gas, and argon gas with low reactivity are preferred from the viewpoint of safety, and nitrogen gas is more preferred from the viewpoint of economy.

Here, the liquid load in the distillation column is the sum of the supply liquid amount (m ³ /time) supplied to the distillation column and the reflux liquid amount (m ³ /time) returned to the top of the column. The supply liquid volume and the reflux liquid volume will vary depending on the output and the set reflux ratio of the distillation tower. However, even if the supply liquid volume and the reflux liquid volume change, as long as the inert gas supply volume is 0.05 to 5Nm ³ - By controlling the inert gas/m ³ -liquid load method, the oxygen partial pressure in the gas phase at the bottom of the distillation tower can be controlled to 50 to 500 Pa.

Furthermore, the oxygen partial pressure in the gas phase part at the bottom of the tower can be calculated based on the dissolved oxygen concentration of the bottom liquid of the distillation tower by measuring the dissolved oxygen concentration. According to Henry's law, the concentration of dissolved oxygen in the bottom liquid is proportional to the partial pressure in the gas phase. Therefore, as mentioned above, the dissolved oxygen can be converted into the oxygen partial pressure of the gas phase in equilibrium with the liquid phase. Furthermore, the gas phase in equilibrium with the tower bottom liquid is the tower bottom gas phase part, so the oxygen partial pressure measured by converting the dissolved oxygen in the tower bottom liquid can be considered to be the same as the oxygen partial pressure of the tower bottom gas phase part. For example, if the measurement result of converting the dissolved oxygen concentration of the tower bottom liquid into oxygen partial pressure is 21 Pa, the oxygen partial pressure of the gas phase part at the bottom of the tower is 21 Pa.

Furthermore, the manufacturing method of the present invention uses the following distillation tower in the first distillation step, and the vent pipe provided in the condensation part of the distillation tower can have a linear speed of 0.01 to 3.0 m in the discharge direction of the vent pipe. / second, preferably 0.04 to 2.5 m/second; the distillation tower has a condensation part at the top of the distillation tower, and has a vent pipe provided in the gas phase of the condensation part In this structure, the condensation part condenses the gas and sends a part of the condensed gas back to the distillation tower. By setting the supply amount of the inert gas to such a level, even if the condensation section becomes negative due to external disturbances such as a sudden temperature change of the refrigerant used in the condensation section and a sudden increase in the amount of liquid supplied to the distillation column, When the pressure is high, it can still prevent the backflow of external gas containing oxygen through the breather tube. This prevents oxygen contained in the external air from being dissolved in the reaction mixture containing isopropyl alcohol, thereby preventing the concentration of dissolved oxygen in isopropyl alcohol from increasing.

Furthermore, the condensation part has a condenser and a reflux tank. The condenser is installed at the top of the distillation tower and can condense the top gas. The reflux tank can accommodate the condensed liquid. Well-known condensation conditions can be used in the condensation section. Generally speaking, as long as the condensation temperature in the condenser is set to a temperature about 5°C lower than the top temperature of the distillation tower, it can be judged that the top gas is sufficiently condensation. For example, as long as the tower top temperature is 35°C, the distillation tower can be set so that the condensation temperature becomes 30°C. Since the reflux ratio has little effect on the dissolved oxygen concentration of isopropyl alcohol, it may be set based on the target purity of the liquid composition of the reaction mixture containing isopropyl alcohol obtained in the distillation column.

In addition, the so-called vent pipe is provided at the top of the distillation column and is an exhaust line for preventing an increase in pressure inside the distillation column. It is also a line provided in the gas phase of the condensation section of the distillation column. The vent pipe connects the outside air inside the distillation tower and outside the distillation tower. Through the vent pipe, gases such as inert gas and low-boiling point compounds remaining at the top of the distillation tower are discharged out of the system.

The present inventors speculate that the following mechanism is the reason why the oxygen partial pressure in the bottom gas phase portion of the distillation column can be controlled. In the first distillation step, the reaction mixture is taken out from the bottom of the tower and supplied to the second distillation step. In the second distillation step, the reaction mixture containing isopropyl alcohol is further refined. Therefore, in order to reduce the dissolved oxygen concentration in the reaction mixture obtained from the bottom of the distillation tower in the first distillation step, it is only necessary to control the oxygen partial pressure of the gas phase portion at the bottom of the tower that is in equilibrium with the bottom liquid at the bottom of the tower to a specific value. range is enough.

As a means of controlling the oxygen partial pressure in the gas phase part at the bottom of the tower within a specific range, there is an operation of supplying an inert gas downstream of the supply section of the distillation tower, preferably from the bottom of the tower. By supplying the inert gas, it is considered that the oxygen in the gas phase portion at the bottom of the tower can be replaced by the supplied inert gas. Furthermore, it is considered that by controlling the oxygen partial pressure within the above range, not only will the yield of the reaction mixture be reduced, the capacity of the condensation section be reduced, and the gas load in the distillation tower be increased, but all of these will be taken into consideration. advantages.

Furthermore, in order to control the oxygen partial pressure in the gas phase portion at the bottom of the tower in the first distillation step to 50 to 500 Pa, it is also possible to control the oxygen partial pressure at locations other than the supply section of the distillation tower downstream, such as the top and bottom of the distillation tower. The condensation section supplies inert gas to adjust the oxygen partial pressure in the gas phase section at the bottom of the tower. However, since it is far from the bottom of the tower, the replacement efficiency with the inert gas is low, so it is not good.

[Second distillation step] The second distillation step is carried out for the purpose of obtaining isopropanol by removing water from the reaction mixture after the low boiling point compounds have been removed in the first distillation step. The azeotrope temperature of water and isopropyl alcohol is 80.1°C. In the second distillation step, water is removed from the reaction mixture obtained from the bottom liquid of the first distillation step, and water containing approximately 12% by mass is taken out. of isopropyl alcohol. The isopropyl alcohol containing moisture taken out from the top of the tower in the second distillation step can be further dehydrated as needed. On the other hand, water is taken out from the bottom of the tower and recycled.

The water recovered in the second distillation step can be suitably used as a raw material for isopropyl alcohol because low-boiling-point compounds lower than the boiling point of isopropyl alcohol have been removed in the first distillation step of the previous step. This recovered water is put back into the water recovery tank in the raw material supply step and reacts with propylene, thereby producing isopropyl alcohol with reduced impurities.

Furthermore, even in the second distillation step, it is preferable to control the oxygen partial pressure in the gas phase portion at the bottom of the distillation tower, so that the dissolved oxygen dissolved in the product can be further reduced. Even in the second distillation step, by controlling the oxygen partial pressure in the gas phase portion at the bottom of the distillation column, the dissolved oxygen can be reduced in the same manner as in the first distillation step.

Moreover, in the second distillation step, the inert gas may be supplied to the vent pipe in the same manner as in the first distillation step. Even in the second distillation step, by using the same conditions as those in the first distillation step, the increase in dissolved oxygen in the manufacturing step can be suppressed.

[Additional steps] The isopropyl alcohol with reduced impurities obtained in the second distillation step can be further subjected to a dehydration step and a purification step to produce isopropyl alcohol with not only reduced dissolved oxygen but also further reduced impurities. In addition, in addition to the dehydration and purification steps, a filtration step can be used to remove metal and inorganic particles, and an ion exchange resin tower can also be used to remove metal ions. By removing impurities other than organic compounds after distillation, it is possible to produce isopropyl alcohol that can be suitably used as a cleaning agent for electronic devices and the like.

When pouring the produced isopropyl alcohol into a sealed container such as a stainless steel bottle, the storage stability can be further improved by performing the pouring operation under an atmosphere of an inert gas such as nitrogen gas. In addition, the sealed container after filling is preferably sealed with an inert gas such as nitrogen gas. Although the isopropyl alcohol produced by the production method of the present invention can reduce dissolved oxygen and organic acids in the production step, by filling and storing it in such a sealed container, the dissolved oxygen and organic acids can be reduced, and , can store isopropyl alcohol in a state that changes less over time.

Through the above production method, not only the dissolved oxygen but also the organic acid can be reduced, and further, it is possible to industrially produce isopropyl alcohol with little change in the organic acid over time. [Example]

Hereinafter, the present invention will be further explained in detail using examples, but the present invention is not limited to these examples. Furthermore, in the following explanation, "%", "ppm", "ppb" and "ppt" indicating concentration are all based on mass.

<Measurement method of dissolved oxygen> In this manual, the dissolved oxygen concentration of isopropyl alcohol and the oxygen partial pressure of the gas phase part at the bottom of the tower are measured using the ORBISPHERE 510 gas analyzer O ₂ meter manufactured by Hach Co., Ltd. (trade name: Sensing Instrument model 2952A; DO ₂ measuring range: 2ppb ~ 80ppm; PO ₂ measuring range: 5Pa ~ 200kPa) to measure.

Since the above measured value is expressed as the oxygen partial pressure converted from the dissolved oxygen in the solution, as for the oxygen partial pressure in the gas phase part at the bottom of the tower, as mentioned above, the measured value of the bottom liquid is used as the oxygen partial pressure in the gas phase part at the bottom of the tower. Oxygen partial pressure.

Furthermore, the dissolved oxygen concentration (%) of isopropyl alcohol is obtained by measuring the oxygen partial pressure corresponding to the dissolved oxygen at 25°C using the above device for the sampled isopropyl alcohol, and dividing the measurement result by 21 kPa. The value is calculated as a percentage, and 21 kPa is the partial pressure of oxygen in the air at 1 atmosphere and 25°C.

〈Method for determination of organic acids〉 In this specification, the organic acid contained in isopropyl alcohol is measured by ion chromatography under the following measurement conditions. [Measurement conditions] Device name: ICS2100 (manufactured by Thermo Fisher Scientific) anion analysis Detector: conductivity detector Column: IonPacAS18 Flow: 1mL/min Temperature conditions: 30℃ Gradient conditions: 2mM KOHà15 minutes/5mM KOHà25 minutes/40mM KOHà40 minutes/40mM KOH Concentration column: UTAC-LP2 Injection volume: 20mL Detection lower limit: 100ppt

Furthermore, as compounds to be measured for organic acids, in both the Examples and the Comparative Examples, only compounds corresponding to the retention times of formic acid, acetic acid, propionic acid, butyric acid, and isobutyric acid were detected. Therefore, from the graph obtained by the measurement, the quantification of formic acid, acetic acid, propionic acid, butyric acid, and isobutyric acid was performed.

〈Measurement method of moisture content〉 In this specification, the moisture contained in isopropyl alcohol is measured using a Karl Fischer Moisture Analyzer MKC-510 (moisture content measurement range: 10 μg to 100 mg) manufactured by Kyoto Electronics Co., Ltd. using a coulometric titration method. (Anolyte: HYDRANAL-Coulomat AG; Catholyte: HYDRANAL-Coulomat CG)

〈Measurement method of acetone〉 In this specification, acetone contained in isopropyl alcohol is measured using gas chromatography under the measurement conditions shown below. [Measurement conditions] Device name: Agilent 890B GC system (manufactured by Agilent Technologies Co., Ltd.) Injection port temperature: 200℃ Column: DB-WAX (inner diameter 0.25mm, length 30m, film thickness 0.25μm) Detector: mass analysis device Transmission line temperature: 240℃ SIM ion detection: 58 Oven temperature: fixed temperature is 35℃ Injection volume: 1μL Split ratio: 10:1

〈Measurement method of high boiling point compounds〉 [Qualitative analysis] In this specification, the high boiling point compound contained in isopropyl alcohol is measured by gas chromatography under the following measurement conditions. [Measurement conditions] Device name: 7890A/5975C (manufactured by Agilent Technologies, Inc.) Analysis column: SUPELCO WAX-10 (inner diameter 0.25mm, length 60m, film thickness 0.25μm) Column temperature: 35°C (hold for 2 minutes) → heat up at a rate of 5°C/min → 100°C → heat up at a rate of 10°C/min → 240°C (hold for 6 minutes) Carrier gas: helium Carrier gas flow: 2mL/min Injection port temperature: 240℃ Sample injection method: Pulse splitless injection method Pulse pressure during injection: 90psi (2 minutes) Split port flow: 50mL/minute (2 minutes) Use gas-saving mode: 20mL/minute (5 minutes) Transmission line temperature: 240℃ Ion source, quadrupole temperature: 230℃, 150℃ Ion scan: m/Z=25～250

[Quantitative analysis] When a peak is confirmed in the chart obtained by the above-mentioned qualitative analysis method, a database search of the peak is performed using a mass spectrometer to identify the structure. Then, a standard material of the specified high-boiling point compound is prepared, and is quantitatively detected in a qualitative analysis by comparing it with the peak area of a pre-quantified standard material using the selected ion detection method (SIM). The concentration of high boiling point compounds. [SIM ion detection] 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 (retention 45) Group 3 (start time: 16.0 minutes; m/Z: 42, 43, 56 (retention 60) Group 4 (start time: 22.0 minutes; m/Z: 45, 56, 59, 72 (retention 45)

〈Concentration method〉 In order to reduce impurities in the isopropyl alcohol of the present invention, the isopropyl alcohol to be measured must be concentrated as necessary to improve the analysis accuracy. The concentration method is shown below, but the concentration rate can be changed by repeating the following operations as needed. As a condition for concentrating high boiling point compounds, for example, in a precision distillation apparatus, the top temperature of the distillation tower can be set to about 82° C., and distillation can be performed for 24 hours. The number of theoretical plates in a precision distillation device is 2 to 30. As long as the number of plates is within this range, distillation and concentration can be carried out.

Furthermore, by performing distillation at about 82°C for 24 hours, it can be concentrated to 76 times. In addition, in order to prevent the oxidation of the analysis target substance, it is preferable to circulate nitrogen gas in advance in the precision distillation device to create an inert atmosphere. Furthermore, it is preferable that during the distillation process, nitrogen gas is allowed to flow to a liquid storage part, and distillation is performed under a nitrogen atmosphere, and the liquid storage part can store the distillate after distillation.

<Example 1> [Production of isopropyl alcohol] Propylene as a raw material was prepared containing the following components as impurities: 39972 ppm of propane, 20 ppm of ethane, 8 ppm of butene, 0.1 ppm or less of pentene and 0.1 Hexene below ppm. In addition, water as a raw material was prepared by adding phosphotungstic acid as an acid catalyst and adjusting the pH to 3.0. According to the manufacturing steps shown in Figure 1, water heated to 110°C is poured into a container with an internal volume of 10L at a supply rate of 18.4kg/hour (20L/hour because the density is 920kg/m ³ ). into the reactor, and pour propylene at a supply rate of 1.2 kg/hour (raw material supply step).

At this time, the residence time of water in the reactor was 30 minutes, and 1,500 parts by mass of water was supplied relative to 100 parts by mass of propylene. The reaction temperature in the reactor was set to 280° C. and the reaction pressure was set to 250 atm, and propylene and water were reacted to obtain isopropyl alcohol (reaction step).

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

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

Next, a distillation column is used to remove low-boiling-point compounds having a lower boiling point than the boiling point of isopropyl alcohol from the reaction mixture after recovering propylene (first distillation step). During distillation, nitrogen gas is supplied at a load of 4.0 Nm ³ -inert gas/m ³ -liquid through an inert gas supply nozzle provided at the bottom of the distillation tower. After supplying nitrogen, the concentration of dissolved oxygen in the bottom liquid of the distillation tower was measured, and the partial pressure of oxygen in the gas phase portion at the bottom of the tower was calculated to be 56 Pa. After the nitrogen gas is supplied, an inert gas, that is, nitrogen gas, is further supplied at a rate of 2.5 m/sec through a vent pipe provided in the condensation part of the distillation tower.

Next, the reaction mixture is taken out from the bottom of the distillation tower and separated into water and isopropanol using the distillation tower (second distillation step). The water taken out and recovered from the bottom of the tower is adjusted to a temperature of 110°C and a pressure of 1.5 atm, and poured into a water recovery tank for reuse as raw material. In order to maintain the pH of the recovered water at 3.0, phosphotungstic acid is added for adjustment. On the other hand, since the isopropyl alcohol taken out from the top of the tower contains about 12% of water, a distillation step for dehydration is performed, and a distillation step for purifying the isopropyl alcohol is further performed to obtain isopropyl alcohol.

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

[Measurement of organic acids] The organic acid contained in the obtained isopropyl alcohol was measured according to the above method. Organic acids were detected from the obtained graph, and the total amount of organic acids contained in isopropanol 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 their total amount was 4 ppb.

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

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

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

In addition, the results of the analysis of other high-boiling point compounds also show that the detection limit is below 20 ppb. These high-boiling point compounds are: 3-methyl-2-pentanone, 2-hexanone, 3,3-di Methyl-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 mentioned above, the isopropyl alcohol of Example 1 obtained by the manufacturing method of the present invention can not only reduce dissolved oxygen, but also reduce organic acids. Furthermore, the isopropyl alcohol of Example 1 was placed in an inert gas, that is, nitrogen atmosphere, for 30 days. After being placed, the organic acid, acetone, and moisture were measured. The results are shown in Table 3 and Figure 2. As shown in Table 3 and Figure 2, even if the isopropyl alcohol of Example 1 is left for 30 days, the concentrations of organic acids, acetone and moisture do not change.

<Example 2> Regarding the first distillation step, in addition to the inert gas supply nozzle provided at the bottom of the distillation tower, nitrogen was supplied in a manner of 0.1Nm ³ -inert gas/m ³ -liquid load, and was Isopropyl alcohol was produced in the same manner as in Example 1, except that an inert gas, that is, nitrogen was supplied to the vent pipe provided in the condensation section of the distillation column at 0.04 m/sec.

Furthermore, after supplying nitrogen, the concentration of dissolved oxygen in the bottom liquid of the distillation tower was measured, and the partial pressure of oxygen in the gas phase portion at the bottom of the tower was calculated to be 300 Pa.

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

[Measurement of organic acids] The organic acid contained in the obtained isopropyl alcohol was measured according to the above method. Organic acids were detected from the obtained graph, and the total amount of organic acids contained in isopropanol 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 could be identified, with a total amount of 12 ppb.

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

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

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

The results of the analysis of other high-boiling point compounds also show that the detection limit is below 20 ppb. These high-boiling point compounds are: 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 alcohol, 3-methyl-1-pentanol, 1-hexanol, 4-methyl-1-pentanol, 1,2-propanediol and 2-methyl-2,4-pentanediol.

As mentioned above, the isopropyl alcohol of Example 2 obtained by the manufacturing method of the present invention can not only reduce dissolved oxygen, but also reduce organic acids. Furthermore, the isopropyl alcohol of Example 2 was placed in an inert gas, that is, nitrogen atmosphere, for 30 days. After being placed, the organic acid, acetone, and moisture were measured. The results are shown in Table 3 and Figure 2. As shown in Table 3 and Figure 2, in the isopropyl alcohol of Example 2, although the concentration of organic acid and acetone increased slightly, the organic acid did not exceed the target upper limit of 20 ppb even if it was left for 30 days.

<Example 3> In the first distillation step, isopropanol was produced in the same manner as in Example 2 except that the inert gas was not supplied through the vent pipe provided in the condensation section of the distillation tower.

Furthermore, after supplying nitrogen, the concentration of dissolved oxygen in the bottom liquid of the distillation tower was measured, and the oxygen partial pressure in the gas phase portion at the bottom of the tower was calculated to be 480 Pa.

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

[Measurement of organic acids] The organic acid contained in the obtained isopropyl alcohol was measured according to the above method. Organic acids were detected from the obtained graph, and the total amount of organic acids contained in isopropanol 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 can be identified, with a total amount of 15 ppb.

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

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

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

The results of the analysis of other high-boiling point compounds also show that the detection limit is below 20 ppb. These high-boiling point compounds are: 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 alcohol, 3-methyl-1-pentanol, 1-hexanol, 4-methyl-1-pentanol, 1,2-propanediol and 2-methyl-2,4-pentanediol.

As mentioned above, the isopropyl alcohol of Example 3 obtained by the manufacturing method of the present invention can not only reduce dissolved oxygen, but also reduce organic acids. Furthermore, the isopropyl alcohol of Example 3 was placed in an inert gas, that is, nitrogen atmosphere, for 30 days. After being placed, the organic acid, acetone, and moisture were measured. The results are shown in Table 3 and Figure 2. As shown in Table 3 and Figure 2, in the isopropyl alcohol of Example 3, although the concentration of organic acid and acetone increased slightly, the organic acid did not exceed the target upper limit of 20 ppb even if it was left for 30 days.

<Comparative example 1> The first distillation step was performed in the same manner as in Example 1 except that the inert gas, that is, nitrogen, was not supplied from the inert gas supply nozzle provided at the bottom of the distillation tower and the vent pipe provided at the condensation section of the distillation tower. Operate to make isopropyl alcohol.

Furthermore, when the dissolved oxygen concentration of the bottom liquid of the distillation tower was measured and the oxygen partial pressure of the gas phase part at the bottom of the tower was calculated, it was 670 Pa.

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

[Measurement of organic acids] The organic acid contained in the obtained isopropyl alcohol was measured according to the above method. Organic acids were detected from the obtained graph, and the total amount of organic acids 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 could be identified, with a total amount of 26 ppb.

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

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

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

The results of the analysis of other high-boiling point compounds also show that the detection limit is below 20 ppb. These high-boiling point compounds are: 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 alcohol, 3-methyl-1-pentanol, 1-hexanol, 4-methyl-1-pentanol, 1,2-propanediol and 2-methyl-2,4-pentanediol.

As described above, in Comparative Example 1, acetone and water content can be reduced to the same level as Examples 1 to 3, but the dissolved oxygen content cannot be reduced to 0.1% or less relative to the saturated solubility at 25°C. Furthermore, the organic acid concentration cannot be lower than 20 ppb.

Furthermore, the isopropyl alcohol of Comparative Example 1 was left in an inert gas, that is, nitrogen atmosphere for 30 days, and after being left, the organic acid, acetone, and moisture were measured. The results are shown in Table 3 and Figure 2. As shown in Table 3 and Figure 2, after the isopropyl alcohol of Comparative Example 1 was left for 30 days, the concentrations of organic acids and acetone increased significantly.

[Table 1] Oxygen partial pressure in the gas phase at the bottom of the first distillation step [Pa] Saturated solubility of dissolved oxygen in isopropyl alcohol relative to dissolved oxygen at 25°C [%] Example 1 56 0.02 Example 2 300 0.07 Example 3 480 0.09 Comparative example 1 670 0.13

[Table 2] Total amount of organic acids [ppb] Acetone [ppm] Moisture [ppm] Example 1 4 0.3 15 Example 2 12 0.2 15 Example 3 15 0.3 15 Comparative example 1 26 0.3 16

[table 3] Total organic acid concentration after 30 days of storage [ppb] Acetone after 30 days [ppm] Moisture content after 30 days [ppm] Example 1 4 0.3 15 Example 2 16 0.3 15 Example 3 20 0.4 15 Comparative example 1 35 0.6 16

The entire specification of Japanese Application No. 2017-9605 filed on January 23, 2017 is incorporated into this specification by reference.

without

Fig. 1 is a schematic diagram showing an example of the production method of isopropyl alcohol according to the present invention. Fig. 2 is a graph showing changes over time in the organic acid concentration of isopropyl alcohol in Examples 1 to 3 and Comparative Example 1.

Domestic storage information (please note in order of storage institution, date and number) without

Overseas storage information (please note in order of storage country, institution, date, and number) without

Claims (1)

A method for producing isopropyl alcohol, which directly hydrates water with propylene to produce isopropyl alcohol. The method includes the following steps: a raw material supply step, which supplies propylene and water to a reactor, and the water An acid catalyst is dissolved and the pH has been adjusted to 2.5~4.5; a reaction step, which reacts propylene and water in the aforementioned reactor; a recovery step, which removes unreacted propylene from the reaction mixture obtained in the aforementioned reaction step Propylene is separated, and the reaction mixture containing isopropyl alcohol is recovered; the first distillation step is to distill the reaction mixture recovered in the aforementioned recovery step in a distillation tower to remove low-boiling point compounds, which have A lower boiling point than the boiling point of isopropanol; and, a second distillation step in which the reaction mixture after removing low-boiling compounds in the aforementioned first distillation step is distilled in a distillation tower to remove water and obtain isopropyl alcohol. alcohol; and in the first distillation step, the following distillation tower is used, inert gas is supplied to the vent tube so that the linear velocity in the discharge direction of the vent tube becomes 0.01 to 3.0 m/second, and the distillation column is The oxygen partial pressure in the gas phase part at the bottom of the tower is controlled at 50~500Pa. The distillation tower has a condensation part at the top of the distillation tower and a structure equipped with a vent pipe. The condensation part condenses the gas and releases part of the condensed gas. Returned to the distillation tower, the vent pipe It is used to discharge the gas existing in the gas phase of the condensation part.