Industrial-grade isopropanol azeotropic distillation dehydration method

Abstract

The invention belongs to the technical field of azeotropic distillation and dehydration of isopropanol, particularly relates to an azeotropic distillation and dehydration method of industrial-grade isopropanol, and aims to solve the problems that the energy consumption of separation of isopropanol and solvents is high, the energy consumption is low and the like due to the fact that solvents such as benzene and cyclohexane are adopted for azeotropic distillation and dehydration in the conventional isopropanol dehydration process, but the boiling points of benzene and cyclohexane are close to those of isopropanol. In order to solve the problems that when diethyl ether is used as an azeotropic agent, the solvent is easily enriched at the tower top to form potential safety hazards, and when the solvents are used for azeotropic distillation, the requirements of electronic chemicals cannot be met, the following scheme is provided: the method comprises the following steps: S1, adding an industrial-grade isopropanol raw material into an azeotropic distillation tower; the azeotropic dehydrating agent disclosed by the invention is small in boiling point, high in ignition point, non-corrosive, low in price, good in safety and low in separation energy consumption, and has excellent application value and application prospect in industrial production and experiments, the used device is simple and easy to operate, the yield is high, and automatic production can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of isopropanol azeotropic distillation dehydration, in particular to an industrial-grade isopropanol azeotropic distillation dehydration method. Background Art

[0002] Isopropyl alcohol is an important organic compound and solvent, and is an isomer of n-propyl alcohol. It has a low boiling point, is volatile, and is miscible with water, making it widely used in pharmaceuticals, cosmetics, plastics, fragrances, and coatings. Especially in recent years, with the development of the electronic information industry, it has important applications in integrated circuits, flat panel displays, circuit board printing, photovoltaics, and batteries. It can act as a cleaning agent. Isopropyl alcohol used for integrated circuits and circuit board printing needs to meet ultra-clean and high-purity requirements. It belongs to the field of wet electronic chemicals. The product quality of electronic-grade isopropyl alcohol seriously affects the yield of integrated circuits, flat panel displays, and circuit boards. When isopropyl alcohol contains trace amounts of water and metal elements, it is easy to cause integrated circuits or semiconductor components to be broken down, thereby affecting the product life. For this reason, electronic-grade isopropyl alcohol products must undergo a strict dehydration procedure.

[0003] In the prior art, isopropyl alcohol is dehydrated by azeotropic distillation using solvents such as benzene and cyclohexane. However, the boiling points of benzene and cyclohexane are close to those of isopropyl alcohol, resulting in high energy consumption for separating isopropyl alcohol from the solvent. When ether is used as an azeotropic agent, the solvent is easily enriched at the top of the tower, forming a potential safety hazard. Moreover, when these solvents are used for azeotropic distillation, the water content in isopropyl alcohol can only reach 0.3%-0.5%, which is far from meeting the requirements of electronic chemicals. Similarly, extractive distillation using ethylene glycol can also achieve isopropyl alcohol dehydration. Although the azeotropic point can be broken and the number of theoretical plates can be reduced, the water content in isopropyl alcohol reaches -0.2%. Adsorption distillation has also been used for isopropyl alcohol dehydration. Although there have been studies, no industrial reports have been seen. Summary of the invention

[0004] The invention aims to solve the problem that in the prior art, isopropyl alcohol dehydration uses solvents such as benzene and cyclohexane for azeotropic distillation dehydration, but the boiling points of benzene and cyclohexane are close to that of isopropyl alcohol, resulting in high energy consumption for separating isopropyl alcohol from the solvent, and when ether is used as an azeotropic agent, the solvent is easily enriched at the top of a tower to form a potential safety hazard, and the azeotropic distillation using these solvents cannot meet the requirements of electronic chemicals, and an industrial-grade isopropyl alcohol azeotropic distillation dehydration method is proposed.

[0005] The present application provides an industrial-grade isopropanol azeotropic distillation dehydration method using the following technical solution: An industrial-grade isopropanol azeotropic distillation dehydration method comprises the following steps: S1: adding industrial grade isopropyl alcohol raw material into an azeotropic distillation column; S2: taking out an azeotrope consisting of solvent and water from the top of the tower and cooling it; S3: The supercondensed liquid enters the three-phase separator to form a water phase and an oil phase; S4: Separate the water phase from the oil-water separator, and send the oil phase to the adsorption tower to remove water from the solvent; S5: After the solvent is adsorbed by the molecular sieve, it is sent to the azeotropic distillation tower for distillation.

[0006] Furthermore, in S1, the operating pressure of the azeotropic distillation tower is 1-3 atm, with the increase of pressure, the molar purity of dichloromethane shows a downward trend, and its entrainment capacity for water is enhanced, but the relative volatility between the materials is reduced, the distillation separation effect is reduced, resulting in a decrease in the molar purity of isopropyl alcohol at the bottom of the tower, so the separation effect is best under normal pressure, the tower bottom temperature is 84-100 ° C, the tower top temperature is 38-60 ° C, the number of plates of the azeotropic distillation tower is 20-50, the feed position is the 3rd to 10th theoretical plate, preferably the 5th plate, the operation flooding rate of the azeotropic distillation tower is between 75% and 85%, and the optimal operation flooding rate is 80%, the azeotropic distillation entrainer is dichloromethane, based on the mass of industrial-grade isopropyl alcohol, the amount of dichloromethane is 26-50% of isopropyl alcohol, the amount of dichloromethane is 30% of isopropyl alcohol, the isopropyl alcohol raw material is industrial isopropyl alcohol of GB / T national mandatory standard, and the distillation tower packing type is a structured wire mesh packing and a structured orifice plate corrugated packing.

[0007] Furthermore, in S2, the azeotrope is cooled to a supercooled state by a condenser, the condensate temperature is controlled at 25-35°C, the optimal supercooling temperature of the condensate is 30°C, the liquid phase reflux logistics of the azeotropic distillation tower is dichloromethane after dehydration, the reflux amount is controlled to be 1 / 3-1 / 2 of the total solvent amount, and the reflux temperature is 30°C.

[0008] Furthermore, in S3, the residence time of the condensate in the three-phase separator is 5-20 minutes, preferably 10 minutes.

[0009] Furthermore, in S4, the oil phase flows out from the oil outlet at the lower end of the three-phase separator and is sent to the adsorption tower, and the water phase flows out from the water outlet of the separator and is sent to the sewage pool. The adsorbent types in the adsorption tower are 5A molecular sieve and silica gel, and the water content in the solvent after adsorption is preferably 0.05%.

[0010] Furthermore, in S5, the water content of the solvent is controlled between 0.001% and 0.1%, a portion of the supercooled solvent is fed into the tower from the first plate at the top of the distillation tower as reflux, and another portion of the supercooled solvent is directly fed into the isopropanol feed plate, and the solvent dichloromethane is fed from the first plate of the distillation tower and the isopropanol feed plate. The ratio of the amount of solvent entering the top of the tower to the amount of solvent entering the isopropanol feed plate is 0.5-2, preferably 1.0, and the water content of the finally obtained isopropanol product is less than 20 ppm.

[0011] In summary, the present application includes at least one of the following beneficial technical effects: 1. The azeotropic dehydrating agent used in this scheme can form the lowest azeotrope with water, and has strong dehydration ability. Its azeotropic temperature is only 38.1°C. The trace water in the solution and the low-boiling-point dichloromethane take away the water in the form of an azeotrope. The water content in the azeotropic solution is 1.5%, thereby achieving the effect of efficient dehydration. The density of dichloromethane is 1.325g / cm3, which is higher than that of water. After separation, it will sink to the lower layer, which is easier to achieve the purpose of separation. The solubility of dichloromethane in water is very small. After separation, the organic matter content in the water is extremely low, no organic wastewater is generated, and the environmental pollution is small; 2. The azeotropic dehydrating agent of this scheme has a low boiling point, a high ignition point, is non-corrosive, low in price, good in safety, and low in separation energy consumption, and has excellent application value and application prospects in industrial production and experiments; 3. The azeotropic dehydrating agent separated out in the form of azeotropy in this scheme is transferred back to the azeotropic distillation tower, which not only continues to take away the water in the isopropanol in the form of azeotropy, thereby allowing the reaction to proceed in a positive direction and improving the conversion rate of the reaction, but also achieves the purpose of energy conservation, emission reduction, and recycling and reuse. The azeotropic agent used is a mixed solution, which has the characteristics of easy absorption and good separation effect; 3. The adsorbent used in this scheme is 5A zeolite molecular sieve or silica gel, which has the characteristics of high adsorption and fast adsorption speed. Since isopropanol has a strong water absorption capacity, it is difficult to remove the water by conventional azeotropic distillation method. The adsorption tower in the present invention can deeply remove the water in the oil phase, and the water content in the oil phase returning to the distillation tower can reach a minimum of 10ppm.

[0012] The azeotropic dehydrating agent of the present invention has a low boiling point, a high ignition point, is non-corrosive, low in price, good in safety, and low in separation energy consumption, and has excellent application value and application prospects in industrial production and experiments. The device used is simple and easy to operate, has a high yield, and can realize automated production. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a flow chart of the azeotropic distillation dehydration of isopropanol in Example 1 of the present invention; Figure 2 This is a flow chart of the azeotropic distillation dehydration of isopropanol in Example 2 of the present invention. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Embodiment 1

[0015] Reference Figure 1 , an industrial-grade isopropanol azeotropic distillation dehydration method, comprising the following steps: S1: adding industrial grade isopropyl alcohol raw material into an azeotropic distillation column; S2: taking out an azeotrope consisting of solvent and water from the top of the tower and cooling it; S3: The supercondensed liquid enters the three-phase separator to form a water phase and an oil phase; S4: Separate the water phase from the oil-water separator, and send the oil phase to the adsorption tower to remove water from the solvent; S5: After the solvent is adsorbed by the molecular sieve, it is sent to the azeotropic distillation tower for distillation.

[0016] In this embodiment, in S1, the operating pressure of the azeotropic distillation tower is 1-3 atm, with the increase of pressure, the molar purity of dichloromethane shows a downward trend, and its entrainment capacity for water is enhanced, but the relative volatility between the materials is reduced, the distillation separation effect is reduced, resulting in a decrease in the molar purity of isopropyl alcohol at the bottom of the tower, so the separation effect is best under normal pressure, the tower bottom temperature is 84-100°C, the tower top temperature is 38-60°C, the number of plates of the azeotropic distillation tower is 20-50, the feed position is the 3rd to 10th theoretical plates, preferably the 5th plate, the operation flooding rate of the azeotropic distillation tower is between 75% and 85%, and the optimal operation flooding rate is 80%, the azeotropic distillation entrainer is dichloromethane, based on the mass of industrial-grade isopropyl alcohol feed, the amount of dichloromethane is 26-50% of isopropyl alcohol, the amount of dichloromethane is 30% of isopropyl alcohol, the isopropyl alcohol raw material is industrial isopropyl alcohol of GB / T national mandatory standard, and the filling types of the distillation tower are structured wire mesh filler and structured orifice plate corrugated filler.

[0017] In this embodiment, in S2, the azeotrope is cooled to a supercooled state by a condenser, the condensate temperature is controlled at 25-35°C, the optimal supercooling temperature of the condensate is 30°C, the liquid phase reflux logistics of the azeotropic distillation tower is dichloromethane after dehydration, the reflux amount is controlled to be 1 / 3-1 / 2 of the total solvent amount, and the reflux temperature is 30°C.

[0018] In this embodiment, in S3, the residence time of the condensate in the three-phase separator is 5-20 minutes, preferably 10 minutes.

[0019] In this embodiment, in S4, the oil phase flows out from the oil outlet at the lower end of the three-phase separator and is sent to the adsorption tower, and the water phase flows out from the water outlet of the separator and is sent to the sewage pool. The adsorbent types in the adsorption tower are 5A molecular sieve and silica gel, and the water content in the solvent after adsorption is preferably 0.05%.

[0020] In this embodiment, in S5, the water content of the solvent is controlled between 0.001% and 0.1%, a portion of the supercooled solvent is fed into the tower from the first plate at the top of the distillation tower as reflux, and another portion of the supercooled solvent is directly fed into the isopropanol feed plate, and the solvent dichloromethane is fed from the first plate of the distillation tower and the isopropanol feed plate. The ratio of the amount of solvent entering the top of the tower to the amount of solvent entering the isopropanol feed plate is 0.5-2, preferably 1.0, and the water content of the finally obtained isopropanol product is less than 20ppm.

[0021] The implementation principle in this embodiment is: the solution to be separated is added to the azeotropic distillation tower, and azeotropic dichloromethane is added at the same time, and the amount of each is 30% of isopropyl alcohol. The isopropyl alcohol raw material is selected as industrial isopropyl alcohol with a mass fraction of 99.5%, the feed temperature is 26°C, the operating pressure in the azeotropic distillation tower is 1atm, the tower top temperature is 38°C, the tower bottom temperature is 86°C, the theoretical number of plates of the azeotropic distillation tower is 2 isopropyl alcohol, the feed position is the 10th theoretical plate, the feed flow rate is 100 kg / hr, the adsorbent is 5A zeolite molecular sieve, the azeotrope after condensation is layered in the oil-water separator, the oil phase enters the adsorption tower, and the water phase is discharged, and the adsorbed oil phase is re-added to the azeotropic distillation tower from the first theoretical plate and the tenth theoretical plate for distillation, wherein the amount added from the first plate is 10 kg / hr, and the amount added from the tenth plate is 20 kg / hr, in a cyclic operation, after which the dehydrated isopropanol solution obtained from the bottom of the tower has a moisture content of 15 ppm. Embodiment 2

[0022] Reference Figure 2 , an industrial-grade isopropanol azeotropic distillation dehydration method, comprising the following steps: S1: adding industrial grade isopropyl alcohol raw material into an azeotropic distillation column; S2: taking out an azeotrope consisting of solvent and water from the top of the tower and cooling it; S3: The supercondensed liquid enters the three-phase separator to form a water phase and an oil phase; S4: Separate the water phase from the oil-water separator, and send the oil phase to the adsorption tower to remove water from the solvent; S5: After the solvent is adsorbed by the molecular sieve, it is sent to the azeotropic distillation tower for distillation.

[0023] In this embodiment, in S1, the operating pressure of the azeotropic distillation tower is 1-3 atm, with the increase of pressure, the molar purity of dichloromethane shows a downward trend, and its entrainment capacity for water is enhanced, but the relative volatility between the materials is reduced, the distillation separation effect is reduced, resulting in a decrease in the molar purity of isopropyl alcohol at the bottom of the tower, so the separation effect is best under normal pressure, the tower bottom temperature is 84-100°C, the tower top temperature is 38-60°C, the number of plates of the azeotropic distillation tower is 20-50, the feed position is the 3rd to 10th theoretical plates, preferably the 5th plate, the operation flooding rate of the azeotropic distillation tower is between 75% and 85%, and the optimal operation flooding rate is 80%, the azeotropic distillation entrainer is dichloromethane, based on the mass of industrial-grade isopropyl alcohol feed, the amount of dichloromethane is 26-50% of isopropyl alcohol, the amount of dichloromethane is 30% of isopropyl alcohol, the isopropyl alcohol raw material is industrial isopropyl alcohol of GB / T national mandatory standard, and the filling types of the distillation tower are structured wire mesh filler and structured orifice plate corrugated filler.

[0024] In this embodiment, in S2, the azeotrope is cooled to a supercooled state by a condenser, the condensate temperature is controlled at 25-35°C, the optimal supercooling temperature of the condensate is 30°C, the liquid phase reflux logistics of the azeotropic distillation tower is dichloromethane after dehydration, the reflux amount is controlled to be 1 / 3-1 / 2 of the total solvent amount, and the reflux temperature is 30°C.

[0025] In this embodiment, in S3, the residence time of the condensate in the three-phase separator is 5-20 minutes, preferably 10 minutes.

[0026] In this embodiment, in S4, the oil phase flows out from the oil outlet at the lower end of the three-phase separator and is sent to the adsorption tower, and the water phase flows out from the water outlet of the separator and is sent to the sewage pool. The adsorbent types in the adsorption tower are 5A molecular sieve and silica gel, and the water content in the solvent after adsorption is preferably 0.05%.

[0027] In this embodiment, in S5, the water content of the solvent is controlled between 0.001% and 0.1%, a portion of the supercooled solvent is fed into the tower from the first plate at the top of the distillation tower as reflux, and another portion of the supercooled solvent is directly fed into the isopropanol feed plate, and the solvent dichloromethane is fed from the first plate of the distillation tower and the isopropanol feed plate. The ratio of the amount of solvent entering the top of the tower to the amount of solvent entering the isopropanol feed plate is 0.5-2, preferably 1.0, and the water content of the finally obtained isopropanol product is less than 20ppm.

[0028] The implementation principle in this embodiment is: the solution to be separated is added to the azeotropic distillation tower, and the azeotropic dehydrating agent dichloromethane is added at the same time, and the amount added is 40% of the amount of isopropyl alcohol. The isopropyl alcohol raw material is selected as industrial isopropyl alcohol with a mass fraction of 99.5%. The feed temperature is 26°C, the operating pressure in the azeotropic distillation tower is 1atm, the tower top temperature is 38.1°C, the tower bottom temperature is 86°C, the azeotropic distillation tower has 35 theoretical plates, the feed position is the 10th theoretical plate, the feed flow rate is 100 kg / hr, the adsorbent is 5A zeolite molecular sieve, the azeotrope after condensation is layered in the oil-water separator, the oil phase enters the adsorption tower, the water phase is discharged, and the adsorbed oil phase is re-added to the azeotropic distillation tower from the 1st theoretical plate and the 10th theoretical plate, respectively, wherein the amount added from the 1st plate is 15 kg / hr, and the amount added from the 10th plate is 25 The circulation operation was carried out at 4000 kg / hr. After the operation was completed, the water content of the dehydrated isopropanol solution obtained from the bottom of the tower was 10 ppm.

[0029] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An industrial grade isopropanol azeotropic distillation dehydration method, characterized in that: The following steps are involved: S1: adding industrial grade isopropyl alcohol raw material into an azeotropic distillation column; S2: taking out an azeotrope consisting of solvent and water from the top of the tower and cooling it; S3: The supercondensed liquid enters the three-phase separator to form a water phase and an oil phase; S4: Separate the water phase from the oil-water separator, and send the oil phase to the adsorption tower to remove water from the solvent; S5: After the solvent is adsorbed by the molecular sieve, it is sent to the azeotropic distillation tower for distillation.

2. A method for dehydrating industrial-grade isopropanol by azeotropic distillation according to claim 1, characterized in that: In S1, the operating pressure of the azeotropic distillation tower is 1-3 atm, the bottom temperature is 84-100° C., the top temperature is 38-60° C., the number of plates of the azeotropic distillation tower is 20-50, and the operating flooding rate of the azeotropic distillation tower is between 75% and 85%.

3. A method for dehydrating industrial-grade isopropanol by azeotropic distillation according to claim 2, characterized in that: In S1, the azeotropic distillation entrainer is dichloromethane. The amount of dichloromethane added is 26-50% of the isopropyl alcohol based on the mass of the industrial-grade isopropyl alcohol feed. The isopropyl alcohol raw material is industrial isopropyl alcohol in accordance with the GB / T national mandatory standard.

4. A method for dehydrating industrial-grade isopropanol by azeotropic distillation according to claim 3, characterized in that: In S2, the azeotrope is cooled to a supercooled state by a condenser, and the condensate temperature is controlled at 25-35°C.

5. A method for dehydrating industrial-grade isopropanol by azeotropic distillation according to claim 4, characterized in that: In S4, the oil phase flows out from the oil outlet at the lower end of the three-phase separator and is sent to the adsorption tower, and the water phase flows out from the water outlet of the separator and is sent to the sewage pool.

6. A method for dehydrating industrial-grade isopropanol by azeotropic distillation according to claim 5, characterized in that: In S5, the water content of the solvent is controlled between 0.001% and 0.1%, a portion of the supercooled solvent is fed into the tower from the first plate at the top of the distillation tower as reflux, and another portion of the supercooled solvent is directly fed into the isopropanol feed plate.

7. A method for dehydrating industrial-grade isopropanol by azeotropic distillation according to claim 6, characterized in that: In S1, the packing types of the distillation tower are structured wire mesh packing and structured perforated plate corrugated packing.

8. An industrial-grade isopropanol azeotropic distillation dehydration method according to claim 7, characterized in that: In S3, the residence time of the condensate in the three-phase separator is 5-20 minutes.

9. The method for dehydrating an industrial-grade isopropanol by azeotropic distillation according to claim 8, characterized in that: In S4, the adsorbent types in the adsorption tower are 5A molecular sieve and silica gel.

10. The industrial-grade isopropanol azeotropic distillation dehydration method according to claim 9, characterized in that: In S5, the ratio of the amount of solvent entering the tower top to the amount of solvent entering the isopropanol feed plate is 0.5-2.

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