Preparation method and preparation system of ultra-pure isopropanol

Abstract

The invention relates to a preparation method and a preparation system of ultra-high-purity isopropanol. The method comprises the following steps: enabling an isopropanol raw material to pass through a nanofiltration device to obtain ultra-high-purity isopropanol; the molecular weight cutoff of a nanofiltration membrane of the nanofiltration device is 100 to 150Da; under the condition that the pH is 7-8, the membrane surface Zeta potential of the nanofiltration membrane is-45 to-20 mV. According to the preparation method provided by the invention, residual organic impurities, metal ion impurities and anion impurities in the isopropanol can be efficiently and quickly removed, the standard of SEMI C12 (G5) is met, and the purity of the isopropanol is more than 99.999%.

Description

Technical Field

[0001] The present invention relates to the field of preparation of ultrapure and high-purity chemicals for electronic information industry, and in particular to a preparation method and a preparation system of ultra-high-purity isopropyl alcohol. Background Art

[0002] With the rapid development of semiconductor technology, the requirements for ultra-high purity reagents are getting higher and higher. In the processing of integrated circuits (ICs), ultra-high purity reagents are mainly used for cleaning and etching the surface of chips and silicon rounds. Their purity and cleanliness have a very significant impact on the yield, performance and reliability of integrated circuits. As an important microelectronic chemical, ultra-high purity isopropyl alcohol has been widely used in cleaning and drying in the processing of semiconductors and large-scale integrated circuits. Isopropyl alcohol for integrated circuits has strict requirements on the content of trace organic impurities, metal cation impurities, particle size and number, and anion impurity content. In particular, as the processing size of integrated circuits enters the nano era, higher requirements are put forward for the high-purity ultra-clean isopropyl alcohol that matches it. In terms of purity, it is necessary to meet the SEMI C12 (G5) standard formulated by the International Semiconductor Equipment and Materials Organization, in which the metal impurity content is less than 10ppt; the purity of isopropyl alcohol also needs to reach more than 99.999%. At present, electronic grade isopropyl alcohol is usually made of industrial grade isopropyl alcohol as raw material, and is processed through multiple process steps such as distillation, molecular sieve adsorption, and ion exchange resin treatment. Not only are the process steps long, but also, due to the presence of azeotropes, organic impurities with a boiling point close to that of isopropyl alcohol produced during the production of isopropyl alcohol cannot be removed by distillation to a high degree, so that the purity of isopropyl alcohol cannot reach more than 99.999%. Based on the above analysis, it is still necessary to develop a simpler purification method that can efficiently remove organic impurities and ionic impurities in isopropyl alcohol to achieve the preparation of ultra-high purity isopropyl alcohol. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and provide a method for preparing ultra-high purity isopropyl alcohol by only using a nanofiltration system and optimizing the nanofiltration membrane of the nanofiltration system. The method provided by the present invention is simple and efficient, and in particular, can efficiently remove organic impurities, metal ion impurities and anion impurities in isopropyl alcohol, thereby producing high-quality electronic grade isopropyl alcohol.

[0004] Solutions for solving problems

[0005] One of the purposes of the present invention is to provide a method for preparing ultra-high purity isopropyl alcohol, the method comprising: passing an isopropyl alcohol raw material through a nanofiltration device to obtain the ultra-high purity isopropyl alcohol;

[0006] The molecular weight cut-off of the nanofiltration membrane of the nanofiltration device is 100 to 150 Da;

[0007] Under the condition of pH 7 to 8, the Zeta potential of the membrane surface of the nanofiltration membrane is -45 to -20 mV.

[0008] Preferably, when the pH value is 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -40 to -25 mV, preferably -40 to -30 mV.

[0009] Preferably, the molecular weight cut-off of the nanofiltration membrane is 100-130 Da.

[0010] Preferably, the operating pressure of the nanofiltration device is 15-55 bar, and the feed temperature is 20-25°C.

[0011] Preferably, the nanofiltration membrane is a polyamide composite membrane.

[0012] Preferably, the method comprises sequentially passing the isopropyl alcohol raw material through N-stage nanofiltration devices to obtain the ultra-high isopropyl alcohol, where N is greater than or equal to 1.

[0013] Preferably, N is 1, 2 or 3, more preferably, N is 2.

[0014] Another object of the present invention is a system for preparing ultra-high purity isopropanol, the preparation system comprising N stages of nanofiltration systems connected in series, each stage of the nanofiltration system being provided with a nanofiltration membrane, wherein the molecular weight cutoff of the nanofiltration membrane is 100 to 150 Da; and under the condition of pH 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -45 to -20 mV.

[0015] Preferably, each stage of the nanofiltration system comprises a storage device for storing the raw material liquid, a nanofiltration device for filtering the raw material liquid connected to the storage device, and a concentrated liquid circulation system;

[0016] One end of the concentrated liquid circulation system is connected to the nanofiltration device at this stage, and the other end is connected to the storage device at this stage; or,

[0017] One end of the concentrated liquid circulation system is connected to the nanofiltration device at this stage, and the other end is connected to the feed inlet end of the nanofiltration device at this stage.

[0018] Preferably, when the pH value is 7 to 8, the Zeta potential of the membrane surface of the nanofiltration membrane is -40 to -25 mV.

[0019] Preferably, the molecular weight cut-off of the nanofiltration membrane is 100-130 Da.

[0020] Preferably, the nanofiltration membrane is a polyamide composite membrane.

[0021] Preferably, N is greater than or equal to 1, preferably 1, 2 or 3, and more preferably 2.

[0022] Preferably, the recovery rate of each stage of the nanofiltration system is not higher than 95%.

[0023] Effects of the Invention

[0024] Compared with the multi-step removal method in the prior art, the present invention can simultaneously and efficiently remove organic impurities, metal ion impurities and anion impurities in industrial-grade isopropyl alcohol by only one-step nanofiltration system and optimizing the nanofiltration membrane of the nanofiltration system, and prepare ultra-high-purity isopropyl alcohol, which has the advantages of being simple, efficient, more economical and convenient; specifically, the present invention controls the molecular weight cut-off and the Zeta potential of the nanofiltration membrane in the nanofiltration system (specifically the nanofiltration device) so that the two produce a synergistic effect to achieve excellent removal of organic impurities, metal ion impurities and anion impurities. The preparation method provided by the present invention has a high effect on organic impurities, metal ion impurities and anion impurities, and even for isopropyl alcohol with a higher purity (more than 99.98%), trace organic impurities, metal ions and anion impurities can still be further removed. The method provided by the present invention can produce high-quality electronic-grade isopropyl alcohol, and the purity of the obtained isopropyl alcohol can reach more than 99.999%, wherein the content of single metal ion impurities is less than 10ppt (especially less than 3ppt), and the total content of anionic impurities is less than 2ppb, which can meet the SEMI C12 (G5) standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The process flow chart of the method for purifying ultra-high isopropyl alcohol using an intermittent nanofiltration system in an embodiment of the present invention;

[0026] Figure 2 The present invention is a process flow chart of a method for purifying ultra-high isopropyl alcohol using a continuous nanofiltration system in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical solutions and beneficial effects of the present invention more clearly understandable, the following is a detailed description by listing specific embodiments. The drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly show the details of the local features; unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which this application belongs.

[0028] The experimental methods in the following examples of the present invention, where no specific conditions are specified, are usually carried out under conventional conditions or under conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0029] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products or equipment.

[0031] The "multiple" mentioned in the present invention refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. After extensive research, the inventors have proposed a simpler and more efficient purification method for removing organic impurities and ionic impurities in isopropanol to achieve the preparation of ultra-high purity isopropanol. Furthermore, the inventors use a nanofiltration system and optimize the nanofiltration membrane in the nanofiltration membrane assembly in the nanofiltration system, and then propose a method for preparing ultra-high purity isopropanol, especially using a nanofiltration membrane with a specific molecular weight cutoff and a Zeta potential on the membrane surface to produce a synergistic effect, which can efficiently and conveniently remove organic impurities and ionic impurities in isopropanol. Based on this, the present invention is completed.

[0032] One of the purposes of the present invention is to provide a method for preparing ultra-high purity isopropyl alcohol, the method comprising: passing an isopropyl alcohol raw material through a nanofiltration device to obtain the ultra-high purity isopropyl alcohol;

[0033] A nanofiltration membrane is arranged in the nanofiltration device, and the molecular weight cutoff of the nanofiltration membrane is 100-150Da (e.g., 100Da, 110Da, 120Da, 130Da, 140Da, 150Da, etc.);

[0034] Under the condition of pH 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -45 to -20 mV (for example, -45 mV, -42 mV, -40 mV, -38 mV, -35 mV, -32 mV, -30 mV, -28 mV, -25 mV, -22 mV, -20 mV, etc.).

[0035] In certain embodiments, at a pH of 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -40 to -25 mV.

[0036] In certain embodiments, at a pH of 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -40 to -30 mV.

[0037] In certain specific and preferred embodiments, at a pH of 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -40 mV, -35 mV or -25 mV.

[0038] In certain embodiments, the molecular weight cut-off of the nanofiltration membrane is 100-130 Da.

[0039] In certain embodiments, the molecular weight cutoff of the nanofiltration membrane is 100 Da or 130 Da.

[0040] In the present invention, the "nanofiltration device" is a partial component or unit in the preparation system of ultra-high purity isopropyl alcohol, in which a nanofiltration membrane is provided. The component or unit is a component or unit for nanofiltration purification of the raw material isopropyl alcohol. The present invention has a wide range of structural selection for the nanofiltration device, as long as the above-mentioned purpose can be achieved.

[0041] In certain embodiments, the operating pressure of the nanofiltration device is 15 to 55 bar (e.g., 15 bar, 20 bar, 25 bar, 30 bar, 35 bar, 40 bar, 45 bar, 50 bar, 55 bar, etc.), and the feed temperature is 20 to 25°C (e.g., 21°C, 22°C, 23°C, 24°C, 25°C, etc.).

[0042] In certain embodiments, the operating pressure of the nanofiltration device is 30 to 55 bar.

[0043] In certain embodiments, the feed temperature of the nanofiltration device is 22-25°C.

[0044] In certain embodiments, the nanofiltration membrane is a polyamide composite membrane.

[0045] In the present invention, in order to avoid the nanofiltration membrane from swelling easily in the organic solvent during the filtration process, resulting in a decrease in separation performance, the nanofiltration membrane used is an organic solvent resistant nanofiltration membrane. In the present invention, there is no restriction on the polyamide composite membrane, as long as the above-mentioned purpose can be achieved, for example, it can be synthesized by conventional commercial or known methods. In the present invention, the polyamide composite membrane is prepared by interfacial polymerization, and an aqueous phase solution containing amine monomers and an oil phase solution containing acyl chloride monomers are coated on a polysulfone-based membrane. After the two-phase reaction, the polyamide composite membrane can be obtained through post-treatment processes such as washing and drying. The polyamide composite membrane is not limited to aromatic polyamide membranes and polypiperazineamide membranes.

[0046] In certain embodiments, the method comprises sequentially passing the isopropyl alcohol raw material through N-stage nanofiltration devices to obtain the ultra-high isopropyl alcohol, where N is greater than or equal to 1.

[0047] In certain embodiments, N is 1, 2, or 3.

[0048] In certain embodiments, N is 2.

[0049] Another object of the present invention is a system for preparing ultra-high purity isopropanol, the preparation system comprising N-stage nanofiltration systems connected in series, each stage of the nanofiltration system being provided with a nanofiltration membrane, wherein the molecular weight cutoff of the nanofiltration membrane is 100 to 150 Da (e.g., 100 Da, 110 Da, 120 Da, 130 Da, 140 Da, 150 Da, etc.); under the condition of pH 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -45 to -20 mV (e.g., -45 mV, -42 mV, -40 mV, -38 mV, -35 mV, -32 mV, -30 mV, -28 mV, -25 mV, -22 mV, -20 mV, etc.).

[0050] In certain embodiments, each stage of the nanofiltration system includes a storage device for storing a raw liquid, a nanofiltration device for filtering a feed liquid connected to the storage device, and a concentrated liquid circulation system;

[0051] One end of the concentrated liquid circulation system is connected to the nanofiltration device at this stage, and the other end is connected to the storage device at this stage; or,

[0052] One end of the concentrated liquid circulation system is connected to the nanofiltration device at this stage, and the other end is connected to the feed inlet end of the nanofiltration device at this stage.

[0053] In certain embodiments, N is greater than or equal to one.

[0054] In certain embodiments, N is 1, 2, or 3.

[0055] In certain embodiments, N is 2.

[0056] Among them, the nanofiltration system can include one-stage, two-stage, three-stage or more-stage nanofiltration systems. The higher the number of stages, the better the purification effect. The specific level of nanofiltration system can be selected according to the required product purity standard.

[0057] In certain embodiments, the nanofiltration system is a two-stage nanofiltration system.

[0058] In certain embodiments, the nanofiltration system comprises a primary nanofiltration system and a secondary nanofiltration system connected in sequence. Figure 1 and Figure 2As shown, the nanofiltration system includes a primary storage device for storing raw liquid, a primary nanofiltration device connected to the primary storage device and used to filter the raw liquid, a secondary storage device connected to the primary nanofiltration device and used to store the primary product liquid generated by the primary nanofiltration system, and a secondary nanofiltration device connected to the secondary storage device and used to filter the primary product liquid.

[0059] In a specific and preferred embodiment, the nanofiltration system further comprises a concentrate circulation system for conveying concentrate to the storage device or mixing concentrate with feed liquid, which is connected to the storage device at the same level or to the conveying pipeline connecting the storage device at the same level and the nanofiltration device at the same level. Specifically, for example, a primary concentrate circulation system for conveying primary concentrate to the primary storage device, a secondary concentrate circulation system for conveying secondary concentrate to the secondary storage device (such as the process flow Figure 1 ); or, for example, a primary concentrate circulation system in which the primary concentrate is transported to a pipeline connecting a primary storage device and a primary nanofiltration device so that the primary concentrate is mixed with the raw liquid, and a secondary concentrate circulation system in which the secondary concentrate is transported to a pipeline connecting a secondary storage device and a secondary nanofiltration device so that the secondary concentrate is mixed with the primary product liquid (such as a process flow Figure 2 ). In some embodiments, the concentrate circulation system further comprises a secondary concentrate circulation system that connects a downstream nanofiltration device (e.g., a secondary nanofiltration device) with an upstream storage device (e.g., a primary storage device) and is used to transport at least a portion of the concentrate produced by the downstream nanofiltration to the upstream storage device, so as to achieve continuous production and be suitable for industrialization.

[0060] The nanofiltration system includes an intermittent production nanofiltration system (such as a process flow Figure 1 ) or continuous production nanofiltration system (such as process flow Figure 2 Among them, the intermittent nanofiltration system can be used for small-scale isopropanol production (production scale is less than one ton), and the continuous production nanofiltration system can be used for large-scale isopropanol production (production scale is greater than 1t / h).

[0061] Specifically, the raw material isopropanol in the storage device is passed into the primary nanofiltration system for primary nanofiltration to obtain primary product liquid and primary concentrated water; the primary product liquid is passed into the secondary nanofiltration system for secondary nanofiltration to obtain secondary product liquid and secondary concentrated water, the primary concentrated water is nanofiltered again through the primary concentrated liquid circulation system, and the secondary concentrated water is nanofiltered again through the secondary concentrated liquid circulation system. In some embodiments, at least a portion of the secondary concentrated water is nanofiltered again through the secondary concentrated liquid circulation system.

[0062] Each stage of the nanofiltration device contains a nanofiltration membrane, which includes a disc-tube nanofiltration membrane assembly and a roll-type nanofiltration membrane assembly. In order to prevent the nanofiltration membrane from swelling in an organic solvent during the nanofiltration process, resulting in a decrease in separation performance, an organic solvent-resistant nanofiltration membrane is used in the nanofiltration membrane assembly.

[0063] In certain embodiments, at a pH of 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -40 to -25 mV.

[0064] In certain embodiments, the molecular weight cut-off of the nanofiltration membrane is 100-130 Da.

[0065] In certain embodiments, the nanofiltration membrane is a polyamide composite membrane.

[0066] In certain embodiments, the recovery rate of each stage of the nanofiltration system is no higher than 95%.

[0067] In the present invention, the raw material isopropyl alcohol is industrial grade isopropyl alcohol, and there is no limitation on the industrial grade isopropyl alcohol, which can be synthesized by conventional commercially available or known methods. For example, in the present invention, industrial isopropyl alcohol can be prepared by propylene hydration method, which comprises the steps of using propylene and water as raw materials and preparing industrial grade isopropyl alcohol under the action of a catalyst.

[0068] In the present invention, the metal cation concentration is determined by ICP-MS; the anion concentration is determined by ion chromatograph; and the isopropanol content is determined by gas chromatography.

[0069] The present invention is further described below by specific examples. Unless otherwise specified herein, "%" represents mass percentage. The materials and reagents in the following examples, unless otherwise specified, are all commonly used materials or reagents in the art, and can be obtained from commercial sources or synthesized by known methods. The experimental methods for which the conditions are not specified in the following implementation cases are usually carried out according to conventional experimental conditions or the conditions recommended by the manufacturers of the relevant reagents (kits).

[0070] Example 1

[0071] This embodiment provides a method for purifying ultra-high purity isopropyl alcohol, using industrial-grade isopropyl alcohol as a raw material. The method uses a multi-stage nanofiltration system to process the raw material, and each stage of the nanofiltration system removes organic impurities, metal ion impurities, and anion impurities.

[0072] Specifically, combined with the process Figure 1 As shown, the method includes:

[0073] Industrial isopropyl alcohol (purity 99.7%) is passed into the primary stock liquid tank, and the isopropyl alcohol stock liquid is passed into the primary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the primary stock liquid tank, and the obtained product liquid is the primary nanofiltration product liquid. The primary nanofiltration product liquid is passed into the secondary nanofiltration device stock liquid tank, and the primary nanofiltration product liquid in the stock liquid tank is passed into the secondary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the secondary stock liquid tank, and the obtained product liquid is ultra-pure electronic grade isopropyl alcohol, and the product indicators are shown in Table 1. Among them, the operating pressure of each nanofiltration system is 40 bar, the temperature is 22-25 ° C, and the recovery rate is 80%. The primary and secondary nanofiltration devices use disc-tube nanofiltration membrane assemblies, and further the disc-tube nanofiltration membrane assemblies use organic solvent-resistant nanofiltration membranes, the cut-off molecular weight of the nanofiltration membrane is 100 Da, and the Zeta potential is -40 mV (at pH 7-8).

[0074] Example 2

[0075] This embodiment provides a method for purifying ultra-high purity isopropyl alcohol, using industrial-grade isopropyl alcohol as a raw material. The method uses a multi-stage nanofiltration system to process the raw material, and each stage of the nanofiltration system removes organic impurities, metal ion impurities, and anion impurities.

[0076] Specifically, combined with the process Figure 1 As shown, the method includes:

[0077] Industrial isopropyl alcohol (purity 99.7%) is passed into the primary stock liquid tank, and the isopropyl alcohol stock liquid is passed into the primary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the primary stock liquid tank, and the obtained product liquid is the primary nanofiltration product liquid. The primary nanofiltration product liquid is passed into the secondary nanofiltration device stock liquid tank, and the primary nanofiltration product liquid in the stock liquid tank is passed into the secondary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the secondary stock liquid tank, and the obtained product liquid is ultra-pure electronic grade isopropyl alcohol. The product indicators are shown in Table 1. Among them, the operating pressure of each nanofiltration system is 40 bar, the temperature is 22-25 ° C and the recovery rate is 80%. The primary and secondary nanofiltration devices use disc-tube nanofiltration membrane assemblies, and further the disc-tube nanofiltration membrane assemblies use organic solvent-resistant nanofiltration membranes, the cut-off molecular weight of the nanofiltration membrane is 150 Da, and the Zeta potential is -25 mV (at pH 7-8).

[0078] Example 3

[0079] This embodiment provides a method for purifying ultra-high purity isopropyl alcohol, using industrial-grade isopropyl alcohol as a raw material. The method uses a multi-stage nanofiltration system to process the raw material, and each stage of the nanofiltration system removes organic impurities, metal ion impurities, and anion impurities.

[0080] Specifically, combined with the process Figure 1 As shown, the method includes:

[0081] Industrial isopropyl alcohol (purity 99.7%) is passed into the primary stock liquid tank, and the isopropyl alcohol stock liquid is passed into the primary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the primary stock liquid tank, and the obtained product liquid is the primary nanofiltration product liquid. The primary nanofiltration product liquid is passed into the secondary nanofiltration device stock liquid tank, and the primary nanofiltration product liquid in the stock liquid tank is passed into the secondary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the secondary stock liquid tank, and the obtained product liquid is ultra-pure electronic grade isopropyl alcohol. The product indicators are shown in Table 1. Among them, the operating pressure of each nanofiltration system is 40 bar, the temperature is 22-25 ° C and the recovery rate is 80%. The primary and secondary nanofiltration devices use disc-tube nanofiltration membrane assemblies, and further the disc-tube nanofiltration membrane assemblies use organic solvent-resistant nanofiltration membranes, the cut-off molecular weight of the nanofiltration membrane is 130 Da, and the Zeta potential is -30 mV (at pH 7-8).

[0082] Example 4

[0083] This embodiment provides a method for purifying ultra-high purity isopropyl alcohol, using high purity isopropyl alcohol as a raw material. The method constructs a multi-stage nanofiltration system to process the raw material, and each stage of the nanofiltration system removes organic impurities, metal ion impurities and anion impurities.

[0084] Specifically, combined with the process Figure 1 As shown, the method includes:

[0085] High-purity isopropyl alcohol (purity 99.98%) is passed into the primary stock liquid tank, and the isopropyl alcohol stock liquid is passed into the primary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the primary stock liquid tank, and the obtained product liquid is the primary nanofiltration product liquid. The primary nanofiltration product liquid is passed into the secondary nanofiltration device stock liquid tank, and the primary nanofiltration product liquid in the stock liquid tank is passed into the secondary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the secondary stock liquid tank, and the obtained product liquid is ultra-pure electronic grade isopropyl alcohol. The product indicators are shown in Table 1. Among them, the operating pressure of each nanofiltration system is 40 bar, the temperature is 22-25°C, and the recovery rate is 80%. The primary and secondary nanofiltration devices use disc-tube nanofiltration membrane assemblies, and further the disc-tube nanofiltration membrane assemblies use organic solvent-resistant nanofiltration membranes, the molecular weight cutoff of the nanofiltration membrane is 100Da, and the Zeta potential is -40mV (at pH 7-8).

[0086] Example 5

[0087] This embodiment provides a method for purifying ultra-high purity isopropyl alcohol, using industrial-grade isopropyl alcohol as a raw material. The method uses a multi-stage nanofiltration system to process the raw material, and each stage of the nanofiltration system removes organic impurities, metal ion impurities, and anion impurities.

[0088] Specifically, combined with the process Figure 2 As shown, the method includes:

[0089] Industrial isopropyl alcohol (purity 99.7%) is passed into the primary stock liquid tank, and the isopropyl alcohol stock liquid is passed into the primary nanofiltration device by a high-pressure pump, and a part of the concentrated liquid is refluxed to the feed port of the primary nanofiltration device by a circulating pump, and the obtained liquid product is the primary nanofiltration liquid product. The primary nanofiltration liquid product is passed into the secondary nanofiltration device stock liquid tank, and the primary nanofiltration liquid product in the stock liquid tank is passed into the secondary nanofiltration device by a high-pressure pump, and a part of the concentrated liquid is refluxed to the feed port of the secondary nanofiltration device by a circulating pump, and the other part of the concentrated liquid is directly refluxed to the primary stock liquid tank, and the obtained liquid product is ultra-pure electronic grade isopropyl alcohol. The product indicators are shown in Table 1. Among them, the operating pressure of each stage of the nanofiltration system is 40 bar, the temperature is 22-25 ° C and the recovery rate is 80%. The primary and secondary nanofiltration devices both use disc-tube nanofiltration membrane assemblies. Furthermore, the disc-tube nanofiltration membrane assemblies use organic solvent-resistant nanofiltration membranes with a molecular weight cutoff of 100 Da and a Zeta potential of -40 mV (at pH 7-8).

[0090] Comparative Example 1

[0091] This comparative example provides a method for purifying ultra-high purity isopropyl alcohol, using industrial-grade isopropyl alcohol as a raw material. The method adopts a multi-stage nanofiltration system to process the raw material, and each stage of the nanofiltration system removes organic impurities, metal ion impurities and anion impurities.

[0092] Specifically, combined with the process Figure 1 As shown, the method includes:

[0093] Industrial isopropanol (purity 99.7%) is passed into a primary stock liquid tank, and the isopropanol stock liquid is passed into a primary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the primary stock liquid tank, and the obtained product liquid is a primary nanofiltration product liquid. The primary nanofiltration product liquid is passed into a secondary nanofiltration device stock liquid tank, and the primary nanofiltration product liquid in the stock liquid tank is passed into a secondary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the secondary stock liquid tank. The various indicators of the obtained isopropanol product liquid are shown in Table 1. Among them, the operating pressure of each level of the nanofiltration system is 40 bar, the temperature is 22-25°C, and the recovery rate is 80%. The primary and secondary nanofiltration devices use disc-tube nanofiltration membrane assemblies, and further the disc-tube nanofiltration membrane assemblies use organic solvent-resistant nanofiltration membranes, the cut-off molecular weight of the nanofiltration membrane is 200Da, and the Zeta potential is -40mV (at pH 7-8).

[0094] Comparative Example 2

[0095] This comparative example provides a method for purifying ultra-high purity isopropyl alcohol, using industrial-grade isopropyl alcohol as a raw material. The method adopts a multi-stage nanofiltration system to process the raw material, and each stage of the nanofiltration system removes organic impurities, metal ion impurities and anion impurities.

[0096] Specifically, combined with the process Figure 1 As shown, the method includes:

[0097] Industrial isopropanol (purity 99.7%) is passed into a primary stock liquid tank, and the isopropanol stock liquid is passed into a primary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the primary stock liquid tank, and the obtained product liquid is a primary nanofiltration product liquid. The primary nanofiltration product liquid is passed into a secondary nanofiltration device stock liquid tank, and the primary nanofiltration product liquid in the stock liquid tank is passed into a secondary nanofiltration device by a high-pressure pump, and the obtained concentrated solution is refluxed to the secondary stock liquid tank. The various indicators of the obtained isopropanol product liquid are shown in Table 1. Among them, the operating pressure of each level of the nanofiltration system is 40 bar, the temperature is 22-25°C, and the recovery rate is 80%. The primary and secondary nanofiltration devices use disc-tube nanofiltration membrane assemblies, and further the disc-tube nanofiltration membrane assemblies use organic solvent-resistant nanofiltration membranes, the cut-off molecular weight of the nanofiltration membrane is 100Da, and the Zeta potential is -10mV (at pH 7-8).

[0098] Table 1

[0099] Detection items unit Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Isopropyl alcohol content wt% 99.9994 99.9991 99.9992 99.9995 99.9994 99.9982 99.9983 Organic impurities ppm 2 4 3 1 2 150 15 Anions ppb 0.6 2 1 0.5 0.6 47 255 Li ppt 2.4 2.7 2.6 2.0 2.6 186.2 176.2 Be ppt 0.0 0.3 0.2 0.0 0.0 79.0 76.0 Mg ppt 2.5 2.7 2.7 2.3 2.3 195.3 190.3 Al ppt 2.3 2.4 2.5 2.2 2.3 177.4 167.4 K ppt 1.3 1.6 1.5 1.3 1.3 104.4 105.5 Ca ppt 0.8 1.1 1.1 0.6 0.7 63.4 66.2 Ti ppt 0.4 0.6 0.4 0.3 0.4 31.2 30.2 V ppt 2.1 2.4 2.2 2.1 2.1 165.8 165.0 Cr ppt 2.4 2.5 2.4 2.4 2.5 197.2 195.4 Mn ppt 0.3 0.4 0.3 0.2 0.3 28.4 25.4 Fe ppt 0.2 0.2 0.2 0.2 0.2 19.6 20.6 Co ppt 0.4 0.7 0.5 0.3 0.4 36.2 35.2 Ni ppt 0.3 0.8 0.5 0.3 0.3 23.4 23.5 Cu ppt 0.5 0.9 0.7 0.5 0.4 40.0 40.4 Zn ppt 0.4 0.7 0.6 0.4 0.4 31.2 32.2 Ga ppt 0.3 0.6 0.5 0.3 0.3 23.4 23.5 Ge ppt 0.2 0.4 0.4 0.0 0.2 15.6 16.6 Sr ppt 0.1 0.4 0.3 0.1 0.1 7.8 7.9 Zr ppt 0.0 0.2 0.2 0.0 0.0 5.6 4.6 Nb ppt 0.3 0.6 0.5 0.2 0.3 23.4 21.4 Mo ppt 0.4 0.5 0.5 0.3 0.3 31.2 33.1 Pd ppt 0.1 0.4 0.2 0.1 0.1 8.9 7.9 Ag ppt 0.0 0.3 0.1 0.0 0.0 8.6 8.7 Cd ppt 0.0 0.3 0.2 0.0 0.0 8.1 8.1 In ppt 0.1 0.4 0.3 0.1 0.1 9.1 10.1 Sn ppt 0.0 0.3 0.2 0.0 0.0 7.9 8.9 Sb ppt 0.1 0.4 0.3 0.1 0.1 8.8 8.4 Ba ppt 0.0 0.3 0.2 0.0 0.0 6.9 6.9 Ta ppt 0.0 0.4 0.2 0.0 0.0 6.7 6.4 W ppt 0.2 0.6 0.4 0.1 0.1 15.6 13.6 Pt ppt 0.0 0.3 0.2 0.0 0.0 7.7 8.7 Au ppt 0.1 0.4 0.3 0.1 0.1 10.2 11.2 Tl ppt 0.0 0.5 0.2 0.0 0.0 9.1 8.1 Pb ppt 0.0 0.3 0.2 0.0 0.1 8.2 8.7 Bi ppt 0.1 0.3 0.3 0.1 0.1 11.3 11.8

[0100] It can be seen from the above examples that the purity of the isopropyl alcohol prepared in Examples 1 to 5 of the present invention is above 99.999%, which is higher than the isopropyl alcohol prepared in Comparative Examples 1 and 2 (99.998%). The isopropyl alcohol obtained by the method of the present invention meets the SEMI C12 (G5) standard (greater than 99.99%).

[0101] The total amount of anionic impurities in the isopropyl alcohol prepared in Examples 1 to 5 of the present invention is less than 2 ppb, and the content of organic impurities is less than 4 ppm, which is much lower than the isopropyl alcohol prepared in Comparative Examples 1 and 2. For example, taking Example 2 of the present invention and Comparative Example 1 as examples, the total amount of anionic impurities in the isopropyl alcohol prepared in Comparative Example 1 is 23 times the total amount of anionic impurities in the isopropyl alcohol prepared in Example 2, and the content of organic impurities in the isopropyl alcohol prepared in Comparative Example 1 is more than 37 times the content of organic impurities in the isopropyl alcohol prepared in Example 2.

[0102] In Comparative Examples 1 and 2, the content of single metal ion impurities is greater than 4 ppt, and even reaches 197.2 ppt, which cannot meet the SEMI C12 (G5) standard (less than 100 ppt). However, the content of single metal ion impurities in the isopropanol prepared in Examples 1 to 5 of the present invention is less than 3 ppt, which is much higher than that in the comparative examples. The isopropanol obtained by the method of the present invention meets the SEMI C12 (G5) standard.

[0103] Therefore, the present invention controls the retention amount and Zeta potential of the nanofiltration membrane in the nanofiltration device, and the two produce a synergistic effect to prepare a high-purity isopropanol product that exceeds the SEMI C12 (G5) standard.

[0104] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementations included in the claims. Various modifications and changes may be made on the basis of the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments only express several implementations of the present invention and do not limit the scope of protection of the patent of the present invention.

Claims

1. A method for preparing ultra-high purity isopropyl alcohol, characterized in that: The method comprises: passing an isopropyl alcohol raw material through a nanofiltration device to obtain the ultra-high purity isopropyl alcohol; A nanofiltration membrane is arranged in the nanofiltration device, and the molecular weight cut-off of the nanofiltration membrane is 100 to 150 Da; Under the condition of pH 7 to 8, the Zeta potential of the membrane surface of the nanofiltration membrane is -45 to -20 mV.

2. The method according to claim 1, characterized in that When the pH value is 7 to 8, the Zeta potential of the nanofiltration membrane surface is -40 to -25 mV, preferably -40 to -30 mV.

3. The method according to claim 1, characterized in that The molecular weight cut-off of the nanofiltration membrane is 100-130 Da.

4. The method according to claim 1, characterized in that: The operating pressure of the nanofiltration device is 15-55 bar, and the feed temperature is 20-25°C; Preferably, the nanofiltration membrane is a polyamide composite membrane.

5. The method according to any one of claims 1 to 4, characterized in that: The method comprises sequentially passing an isopropyl alcohol raw material through N-stage nanofiltration devices to obtain the ultra-high isopropyl alcohol, where N is greater than or equal to 1; Preferably, N is 1, 2 or 3, more preferably, N is 2.

6. A system for preparing ultra-high purity isopropyl alcohol, characterized in that: The preparation system comprises N-stage nanofiltration systems connected in series, wherein a nanofiltration membrane is arranged in each stage of the nanofiltration system, wherein the molecular weight cutoff of the nanofiltration membrane is 100 to 150 Da; and under the condition of pH 7 to 8, the membrane surface Zeta potential of the nanofiltration membrane is -45 to -20 mV.

7. The preparation system according to claim 6, characterized in that: Each stage of the nanofiltration system includes a storage device for storing raw liquid, a nanofiltration device for filtering the feed liquid connected to the storage device, and a concentrated liquid circulation system; One end of the concentrated liquid circulation system is connected to the nanofiltration device at this stage, and the other end is connected to the storage device at this stage; or, One end of the concentrated liquid circulation system is connected to the nanofiltration device at this stage, and the other end is connected to the feed inlet end of the nanofiltration device at this stage.

8. The preparation system according to claim 6, characterized in that: When the pH value is 7 to 8, the Zeta potential of the membrane surface of the nanofiltration membrane is -40 to -25 mV.

9. The preparation system according to claim 6, characterized in that: The molecular weight cut-off of the nanofiltration membrane is 100-130 Da.

10. The preparation system according to any one of claims 6 to 9, characterized in that: The nanofiltration membrane is a polyamide composite membrane; Preferably, N is greater than or equal to 1, preferably 1, 2 or 3, and more preferably 2.

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