A method for preparing high-purity normal hexane

Abstract

The present invention provides a method for preparing high-purity n-hexane, comprising: adding analytical grade sulfuric acid to industrial grade n-hexane, stirring, and standing to separate the n-hexane; further removing impurities from the n-hexane through a modified molecular sieve; and finally adsorbing the n-hexane using long-wave ultraviolet light modified activated carbon. The industrial grade n-hexane removed impurities by adsorption of analytical grade sulfuric acid is successively subjected to a water vapor modified molecular sieve removal treatment and a long-wave ultraviolet light modified activated carbon adsorption treatment to directly obtain chromatographic grade high-purity n-hexane with a purity of not less than 99.99% and a 215nm ultraviolet transmittance of not less than 98%. The method is simple, easy to operate, stable in operation, and suitable for industrial purification applications.

Description

Technical Field

[0001] The invention relates to the technical field of n-hexane purification, and specifically provides a method for preparing high-purity n-hexane. Background Art

[0002] Hexane is an organic compound reagent with the chemical formula C6H 14 , molecular weight 86.17, national standard number 31005, CAS number 110-54-3, English name n-hexane, or hexyl hydride, is a colorless volatile liquid with a faint special odor, melting point -95 ° C, boiling point 68.74 ° C, belongs to straight-chain saturated aliphatic hydrocarbons, insoluble in water, soluble in ethanol, ether, acetone, chloroform and most other organic solvents, mainly used as solvents, chromatographic analysis reference substances, paint thinners, polymerization reaction media, etc., can also be used in organic synthesis.

[0003] n-Hexane includes industrial grade, environmental grade, chromatographic grade, etc. Among them, industrial grade n-hexane contains impurities such as benzene, olefins, isomers, etc., and its purity is only 78-86%, which is difficult to meet the requirements of the analytical field; and the use of multiple distillation methods to purify can increase the purity to 97%, but it still cannot meet the purity requirements of the chromatographic grade; the purity of n-hexane produced by advanced purification methods such as molecular sieve pressure swing adsorption has reached 99%, but its purification method is complicated and costly, making it difficult to apply industrially.

[0004] The prior art includes a Chinese invention patent application with a publication number of CN105085140A, which discloses a method for purifying n-hexane for liquid chromatography-mass spectrometry, wherein the specific scheme includes adding an oxidant to the n-hexane raw material and then distilling it, adsorbing the distilled n-hexane with modified activated carbon with ethylenediaminetetraacetic acid, aluminum oxide, triethanolamine or aluminum hydroxide attached to the surface, and finally performing ion exchange treatment to obtain n-hexane for liquid chromatography-mass spectrometry with a purity of ≥99.99%. However, the purification method has complicated steps, a wide variety of reagents, and the introduction of metal compound-type oxidants and aluminum-modified activated carbon during the purification process may cause some impurities such as metal ions or compounds to be mixed into the n-hexane, thereby making the n-hexane poorly transparent, affecting the application of chromatography-mass spectrometry.

[0005] The above-mentioned record of background technical knowledge is intended to help ordinary technicians in this field understand the existing technologies that are relatively close to the present invention, and at the same time facilitate the understanding of the inventive concept and technical solution of the present invention. It should be clear that in the absence of clear evidence that the above-mentioned content has been disclosed before the filing date of this patent application, the above-mentioned background technology should not be used to evaluate the novelty of the technical solution of this application. Summary of the invention

[0006] Technical issues

[0007] In order to solve the above problems, the purpose of the present invention is to provide a method for preparing chromatographic grade high-purity n-hexane which is simple, easy to operate, stable in operation, and can directly obtain a purity of not less than 99.99% and a 215nm ultraviolet transmittance of not less than 98%.

[0008] Technical Solution

[0009] In order to achieve the above objectives, the present application provides the following technical solutions.

[0010] A method for preparing high-purity n-hexane, comprising:

[0011] Step 1), add industrial grade n-hexane to analytical grade sulfuric acid, stir, and stand to separate the n-hexane;

[0012] Step 2) The n-hexane in step 1) is further impurity-removed by a modified molecular sieve;

[0013] Step 3), finally, long-wave ultraviolet light is used to modify the activated carbon for adsorption to obtain high-purity n-hexane;

[0014] In step 2), the modified molecular sieve is a molecular sieve modified by nitrogen / water vapor, and the partial pressure percentage of water vapor in the nitrogen / water vapor is not less than 90%.

[0015] First, analytical grade sulfuric acid is used to adsorb and remove water, olefins, benzene and other impurities from industrial grade n-hexane, and then a water vapor-modified molecular sieve is used to further remove residual water, acidic substances and oxygen-containing functional group impurities in the sulfuric acid. Finally, long-wave ultraviolet light-modified activated carbon is used to adsorb the n-hexane to adsorb and remove other impurities such as metal ions remaining in the n-hexane, thereby obtaining chromatographic grade n-hexane with a purity of not less than 99.99% and a 215nm ultraviolet transmittance of not less than 98%. The purification method of the present application is simple, easy to operate, stable in operation, and suitable for industrial purification applications.

[0016] As a further preference for the technical solution of the present invention, in the step 1), the purity of industrial-grade n-hexane is 95-98%.

[0017] As a further optimization of the technical solution of the present invention, in the step 1), the volume ratio of industrial-grade n-hexane to analytical-grade sulfuric acid is 100:0.1-0.5. The use of high-concentration analytical-grade sulfuric acid (95-98%) to fully stir the industrial-grade n-hexane can avoid the introduction of new impurities and remove excess water, olefins, benzene and other impurities in the n-hexane. The single stirring time is appropriately extended to 1.5-5h, preferably 2.5-4h, and more preferably 3-3.5h. A small amount or even a trace amount of analytical-grade sulfuric acid is used in combination with water vapor modified molecular sieves and long-wave ultraviolet light modified activated carbon adsorption to achieve the overall purification and turbidity reduction effect, reduce the cost caused by the amount of sulfuric acid, simplify the procedure for processing a large amount of sulfuric acid, and lay the foundation for obtaining high-purity and high-transparency n-hexane.

[0018] As a further preference for the technical solution of the present invention, in the step 2), the modified molecular sieve is specifically modified by the following steps: nitrogen / water vapor with a water vapor partial pressure percentage of not less than 90% is introduced into the molecular sieve at 150-200°C for at least 2 hours, and after being taken out, it is rinsed with distilled water for at least 3 times and then dried at 40-60°C to constant weight.

[0019] As a further preference for the technical solution of the present invention, in the step 2), the molecular sieve is selected from one of 5A molecular sieve, 13X molecular sieve and β molecular sieve.

[0020] Modification of the molecular sieve with nitrogen / water vapor helps to stabilize the skeleton structure of the molecular sieve, adjust the surface acidity so that the acid centers are evenly distributed, and the modification causes the molecular sieve to undergo dealumination. The molecular sieve may undergo recrystallization and structural rearrangement, thereby changing its pore size distribution and acidic properties. Filtration of n-hexane with the water vapor-modified molecular sieve can further remove moisture, acidic substances and oxygen-containing functional group impurities in the n-hexane. In addition, the inventors have found that, compared with modification of the molecular sieve with nitrogen / water vapor at a low water vapor partial pressure, modification of the molecular sieve with nitrogen / water vapor with a water vapor partial pressure percentage of not less than 90% can significantly reduce the turbidity of n-hexane, and can help increase the 215nm ultraviolet transmittance of n-hexane to a level of not less than 96% without other more cumbersome adsorption operations.

[0021] As a further preference for the technical solution of the present invention, in the step 3), the long-wave ultraviolet light modified activated carbon is specifically obtained by irradiating the activated carbon with long-wave ultraviolet rays of 400 to 315 nm for 2.5 to 5 hours. The surface properties of the activated carbon can be optimized without introducing foreign chemical reagents by modifying the activated carbon with long-wave ultraviolet light. The inventors of the present application have confirmed through ultraviolet irradiation experiments of relevant wavelengths that, compared with short-wave ultraviolet irradiation of 285 to 254 nm, irradiation of activated carbon with long-wave ultraviolet rays of 400 to 315 nm can give the activated carbon a better performance of adsorbing impurities in n-hexane. With the same irradiation treatment time, the activated carbon irradiated with long-wave ultraviolet rays of 400 to 315 nm can further improve the high purity and high transparency of n-hexane, and increase the transmittance of 215 nm ultraviolet rays to a chromatographic level of not less than 98%.

[0022] Provided is a n-hexane purification system, comprising a feed unit, a sulfuric acid adsorption unit, a molecular sieve impurity removal unit, a modified activated carbon adsorption unit and a discharge unit, which are arranged in sequence.

[0023] The feed raw material of the feed unit is industrial grade n-hexane.

[0024] The molecular sieve impurity removal unit comprises: using a molecular sieve modified by nitrogen / water vapor to remove impurities from n-hexane that has completed the sulfuric acid adsorption unit;

[0025] The modified activated carbon adsorption unit comprises: using activated carbon modified by irradiation with long-wave ultraviolet rays of 400 to 315 nm to adsorb normal hexane that has completed the molecular sieve impurity removal unit;

[0026] The purity of n-hexane discharged from the discharging unit is not less than 99.99%, and the transmittance of 215nm ultraviolet rays is not less than 98%.

[0027] The present invention provides a n-hexane purification system, the core of which includes a sulfuric acid adsorption unit, a molecular sieve impurity removal unit, and a modified activated carbon adsorption unit. The above-mentioned units are applicable to the corresponding schemes in each step of the above-mentioned preparation method of high-purity n-hexane. The purification system can obtain high-purity and high-transparency n-hexane with a purity of not less than 99.99% and a 215nm ultraviolet light transmittance of not less than 98% after adsorption of analytical pure sulfuric acid, nitrogen / water vapor modified molecular sieve impurity removal, and long-wave ultraviolet light modified activated carbon adsorption, which can meet the high purity requirements of chromatographic grade and expand the scope of application. In addition, the purification system has a simple structure, the purification medium is easy to recycle, the system operates stably, and is suitable for industrial production.

[0028] Based on the common knowledge in this field, the above-mentioned preferred conditions can be combined with each other to obtain a specific implementation method.

[0029] The raw materials and reagents involved in the present invention are all common commercially available products, and the operations involved are all routine operations in the art unless otherwise specified.

[0030] Beneficial Effects

[0031] According to the present invention, chromatographic grade n-hexane with a purity of not less than 99.99% and a 215nm ultraviolet transmittance of not less than 98% can be directly obtained by successively subjecting industrial grade n-hexane that has been subjected to analytical grade sulfuric acid adsorption and impurity removal treatment through a water vapor modified molecular sieve and a long-wave ultraviolet light modified activated carbon adsorption treatment. The purification method is simple, easy to operate, stable in operation, and suitable for industrial purification applications.

[0032] The present invention adopts the above technical solution to achieve the above purpose, which makes up for the shortcomings of the prior art and has reasonable design and convenient operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to make the above and / or other purposes, features, advantages and examples of the present invention more obvious and easy to understand, the drawings required for use in the specific implementation of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A flow chart showing a system for purifying n-hexane provided by the present invention;

[0035] Figure 2 Infrared spectrum showing activated carbon fiber treated with long-wave ultraviolet radiation;

[0036] Figure 3 The purity statistical result of the purified n-hexane of the present invention is shown;

[0037] Figure 4 The figure shows the statistical result of the 215nm ultraviolet transmittance of the purified n-hexane of the present invention. DETAILED DESCRIPTION

[0038] Those skilled in the art can refer to the content of this article and appropriately replace and / or modify the process parameters to achieve the same. However, it should be particularly noted that all similar replacements and / or modifications are obvious to those skilled in the art and are considered to be included in the present invention. The products and preparation methods described in the present invention have been described through preferred examples. It is obvious that relevant personnel can modify or appropriately change and combine the products and preparation methods described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0039] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. The present invention uses the methods and materials described herein; however, other suitable methods and materials known in the art may also be used. The materials, methods, and examples described herein are illustrative only and are not intended to be limiting. All publications, patent applications, patents, provisional applications, database entries, and other references mentioned herein are incorporated herein by reference in their entirety. In the event of a conflict, the present specification, including definitions, shall prevail.

[0040] Unless otherwise specified, all percentages, parts, ratios, etc. are by weight; otherwise specified, including but not limited to, "%", "wt%", "mass%" means weight percentage, "mol%" means molar percentage, and "vol%" means volume percentage.

[0041] When a quantity, concentration or other numerical value or parameter is given as a range, a preferred range or a series of upper preferred values ​​and lower preferred values, it should be understood that it specifically discloses all ranges formed by any pair of numerical values ​​of any larger range limit or preferred value and any smaller range limit or preferred value, regardless of whether the range is disclosed separately. For example, when describing a range of "1 to 5 (1-5)", the described range should be understood to include a range of "1 to 4 (1-4)", "1 to 3 (1-3)", "1 to 2 (1-2)", "1 to 2 (1-2) and 4 to 5 (4-5)", "1 to 3 (1-3) and 5", etc. Unless otherwise stated, where a numerical range is described herein, the range includes the range end values ​​and all integers and fractions within the range.

[0042] Unless specifically stated, the materials, methods, and examples described herein are illustrative only and not limiting. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are still described herein.

[0043] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. At the same time, the embodiments in this application and the features in the embodiments can be combined with each other without conflict.

[0044] Summary of the Invention

[0045] The invention aims to provide a method for preparing high-purity n-hexane with simple steps, no metal ions or compounds involved, and reusable purification medium. The invention uses industrial-grade n-hexane as a raw material, and adopts three steps including adsorption of analytical-grade sulfuric acid, impurity removal by modified molecular sieves, and adsorption by long-wave ultraviolet light-modified activated carbon to complete the purification of industrial-grade n-hexane. Chromatographic-grade n-hexane with a purity of not less than 99.99% and a 215nm ultraviolet transmittance of not less than 98% is obtained by simple steps.

[0046] Regarding the adsorption and impurity removal of analytical grade sulfuric acid, sulfuric acid has strong water absorption and can absorb water from n-hexane to form hydrated sulfuric acid, which helps to remove water from n-hexane, because water may affect the purity of n-hexane and subsequent use effects. In addition, sulfuric acid can react with certain impurities in n-hexane, such as polar impurities such as alcohols and ketones. These impurities may form sulfates under the action of sulfuric acid, thereby separating from non-polar n-hexane. The dehydration and purification effect of sulfuric acid can significantly improve the purity of n-hexane to reach analytical grade. The n-hexane purified by sulfuric acid has better chemical and physical properties, such as lower viscosity and better fluidity, and is suitable for laboratory analysis and high-precision chemical experiments.

[0047] Regarding the removal of impurities by water vapor modified molecular sieve, water vapor treatment of molecular sieve at high temperature can not only stabilize the skeleton structure of molecular sieve, but also adjust the surface acidity so that the acid center is evenly distributed. After water vapor contacts the molecular sieve, the first water molecule is adsorbed on the acidic site on the surface of the molecular sieve, weakening the Al-O bond, causing the Al-O bond to elongate, and then more water molecules participate in the reaction, further promoting the dealumination process. After dealumination, the molecular sieve may undergo recrystallization and structural rearrangement, thereby changing its pore size distribution and acidic properties. Using water vapor modified molecular sieve to filter n-hexane can further remove moisture, acidic substances and oxygen-containing functional group impurities in n-hexane; in addition, the inventors have found that compared with the modification of molecular sieves with nitrogen / water vapor at low water vapor partial pressure, the modification of molecular sieves with nitrogen / water vapor with a water vapor partial pressure percentage of not less than 90% can significantly reduce the turbidity of n-hexane, without other more cumbersome adsorption operations, which helps to increase the 215nm ultraviolet transmittance of n-hexane to a level of not less than 96%.

[0048] It should be understood that the molecular sieve is passed through nitrogen / water vapor with a water vapor partial pressure percentage of not less than 90% at 150-200° C. for at least 2 hours, and after being taken out, it is rinsed with distilled water at least 3 times and dried at 40-60° C. to constant weight. The molecular sieve selected from 5A molecular sieve, 13X molecular sieve, and β molecular sieve obtained by the above steps can be applied to the method for purifying n-hexane in the present application, and the method for obtaining the water vapor partial pressure percentage is not particularly limited, for example but not limited to, it can be obtained in the following manner: first determine the total pressure of the mixed steam, such as the total pressure is 1.1 atmospheres (atm), Then the water vapor partial pressure percentage is 90%, which is 0.99atm, and the nitrogen partial pressure percentage is 0.11atm. Then calculate the mole fraction of water vapor and the mole fraction of nitrogen. The water vapor source can be generated by heating distilled water, and the nitrogen source can be obtained from a gas supplier. Finally, use a gas mixer or mass flow controller (MFC) to accurately mix water vapor and nitrogen. The flow rate of each gas can be accurately controlled to ensure the correct ratio and partial pressure. During the mixing process, use a pressure regulator to ensure that the total pressure of the mixed gas is maintained at the required level, and then input the mixed steam into the container where the molecular sieve is placed.

[0049] Regarding long-wave ultraviolet light modified activated carbon adsorption, this patent uses long-wave ultraviolet light with a wavelength of about 400 to 315 nm to modify the activated carbon, which can change the surface properties of the activated carbon without introducing any foreign chemical reagents. Possible modification results include: leading to the generation of new functional groups such as carboxyl, hydroxyl, etc., thereby improving the adsorption capacity and catalytic degradation capacity of specific pollutants; leading to micro-adjustments of the pore structure of activated carbon, such as an increase in the ratio of micropores and mesopores, thereby affecting adsorption and selectivity; changing the charge distribution on the surface of activated carbon and thus affecting the adsorption of charged substances; introducing new photocatalytic active centers, thereby improving the photocatalytic degradation of organic pollutants; and enhancing the physical and chemical stability of activated carbon. Specifically in the application process, the inventors of the present application found that compared with short-wave ultraviolet irradiation of 254nm, irradiation treatment of activated carbon with long-wave ultraviolet rays of 400-315nm can give the activated carbon a better performance in adsorbing impurities in n-hexane. With the same irradiation treatment time, activated carbon treated with long-wave ultraviolet rays of 400-315nm can further improve the high purity and high transparency of n-hexane, and increase the transmittance of 215nm ultraviolet rays to a chromatographic level of not less than 98%.

[0050] like Figure 1 As shown, the present application provides a n-hexane purification system, comprising a feed unit, a sulfuric acid adsorption unit, a molecular sieve impurity removal unit, a modified activated carbon adsorption unit and a discharge unit, which are arranged in sequence.

[0051] The feed raw material of the feed unit is industrial grade n-hexane.

[0052] The sulfuric acid adsorption unit comprises: adding analytical grade sulfuric acid to industrial grade n-hexane, stirring, standing to separate n-hexane, and repeating the adsorption 3 to 4 times;

[0053] The molecular sieve impurity removal unit comprises: using a molecular sieve modified by nitrogen / water vapor to remove impurities from n-hexane that has completed the sulfuric acid adsorption unit;

[0054] The modified activated carbon adsorption unit comprises: using activated carbon modified by irradiation with long-wave ultraviolet rays of 400 to 315 nm to adsorb normal hexane that has completed the molecular sieve impurity removal unit;

[0055] The purity of n-hexane discharged from the discharging unit is not less than 99.99%, and the transmittance of 215nm ultraviolet rays is not less than 98%.

[0056] The present invention is described in detail below

[0057] Embodiment 1:

[0058] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0059] Step 1), take industrial grade n-hexane (purity 97%, the same below) and add analytical grade sulfuric acid, mix 0.2 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir at 45r / min for 2h, then stand to separate n-hexane, and repeat the adsorption twice according to the above system to obtain preliminarily purified n-hexane;

[0060] Step 2), take 5A molecular sieve, pass nitrogen / water vapor at 160°C and 90% water vapor partial pressure for 4 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 55°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 100mL / min;

[0061] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 365nm for 4 hours, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0062] The infrared spectrum of the activated carbon fiber treated with long-wave ultraviolet radiation in step 3) is as follows: Figure 2 As shown by Figure 2 It can be seen that 1076~1200cm -1 There are obvious characteristic peaks of carbon-oxygen single bonds in the range of 1570-1710cm -1 The interval peak indicates that the carbon-carbon double bond is not damaged, 1997cm -1There is an inconspicuous absorption peak near it, which may be due to the presence of a carbon-nitrogen triple bond, 2046-2130cm -1 Obvious stretching vibration characteristic peaks of carbon-carbon triple bonds appeared in the interval, indicating that carbon-carbon triple bonds appeared after long-wave ultraviolet light irradiation. The above peaks show that modification of activated carbon fibers with long-wave ultraviolet light helps to change the content of oxygen-containing groups, nitrogen-containing groups and unsaturated groups, which may help the efficient adsorption of activated carbon fibers.

[0063] Embodiment 2:

[0064] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0065] Step 1), add industrial-grade n-hexane to analytical-grade sulfuric acid, mix 0.1 volume of analytical-grade sulfuric acid for every 100 volumes of n-hexane raw material, stir at 60 r / min for 4 hours, and then stand to separate the n-hexane, and then repeat the adsorption three times according to the above system to obtain preliminarily purified n-hexane;

[0066] Step 2), take 13X molecular sieve, pass nitrogen / water vapor at 150°C and 92% water vapor partial pressure for 3 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 60°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 80mL / min;

[0067] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 395nm for 2.5h, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0068] Embodiment 3:

[0069] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0070] Step 1), add industrial grade n-hexane to analytical grade sulfuric acid, mix 0.5 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir at 45r / min for 3h, let stand to separate n-hexane, and repeat adsorption twice according to the above system to obtain preliminarily purified n-hexane;

[0071] Step 2), take 5A molecular sieve, pass nitrogen / water vapor at 175°C and 95% water vapor partial pressure for 2 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 50°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 60mL / min;

[0072] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 356nm for 3h, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0073] Embodiment 4:

[0074] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0075] Step 1), take industrial grade n-hexane (purity 97%) and add analytical grade sulfuric acid, mix 0.15 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir once for 3 hours and then stand to separate the n-hexane, and then repeat the adsorption three times according to the above system to obtain preliminarily purified n-hexane;

[0076] Step 2), take one of the 5A molecular sieves, pass nitrogen / water vapor at 175°C and 95% water vapor partial pressure for 3.5 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 55°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 100 mL / min;

[0077] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 315nm for 4 hours, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0078] Embodiment 5:

[0079] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0080] Step 1), take industrial grade n-hexane (purity 97%, the same below) and add analytical grade sulfuric acid, mix 0.2 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir at 45r / min for 2h, then stand to separate n-hexane, and repeat the adsorption twice according to the above system to obtain preliminarily purified n-hexane;

[0081] Step 2), take 5A molecular sieve, pass nitrogen / water vapor at 160°C and 88% water vapor partial pressure for 4 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 55°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 100mL / min;

[0082] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 365nm for 4 hours, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0083] Embodiment 6:

[0084] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0085] Step 1), add industrial-grade n-hexane to analytical-grade sulfuric acid, mix 0.1 volume of analytical-grade sulfuric acid for every 100 volumes of n-hexane raw material, stir at 60 r / min for 4 hours, and then stand to separate the n-hexane, and then repeat the adsorption three times according to the above system to obtain preliminarily purified n-hexane;

[0086] Step 2), take 13X molecular sieve, pass nitrogen / water vapor at 150°C and 85% water vapor partial pressure for 3 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 60°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 80mL / min;

[0087] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 395nm for 2.5h, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0088] Embodiment 7:

[0089] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0090] Step 1), add industrial grade n-hexane to analytical grade sulfuric acid, mix 0.5 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir at 45r / min for 3h, let stand to separate n-hexane, and repeat adsorption twice according to the above system to obtain preliminarily purified n-hexane;

[0091] Step 2), take 5A molecular sieve, pass nitrogen / water vapor at 175°C and 80% water vapor partial pressure for 2 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 50°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 60mL / min;

[0092] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 356nm for 3h, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0093] Embodiment 8:

[0094] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0095] Step 1), take industrial grade n-hexane (purity 97%) and add analytical grade sulfuric acid, mix 0.15 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir once for 3 hours and then stand to separate the n-hexane, and then repeat the adsorption three times according to the above system to obtain preliminarily purified n-hexane;

[0096] Step 2), take one of the 5A molecular sieves, pass nitrogen / water vapor at 175°C and 75% water vapor partial pressure for 3.5 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 55°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 100mL / min;

[0097] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 315nm for 4 hours, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0098] Embodiment 9:

[0099] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0100] Step 1), take industrial grade n-hexane (purity 97%, the same below) and add analytical grade sulfuric acid, mix 0.2 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir at 45r / min for 2h, then stand to separate n-hexane, and repeat the adsorption twice according to the above system to obtain preliminarily purified n-hexane;

[0101] Step 2), take 5A molecular sieve, pass nitrogen / water vapor at 160°C and 90% water vapor partial pressure for 4 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 55°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 100mL / min;

[0102] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 405nm for 4 hours, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0103] Embodiment 10:

[0104] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0105] Step 1), add industrial-grade n-hexane to analytical-grade sulfuric acid, mix 0.1 volume of analytical-grade sulfuric acid for every 100 volumes of n-hexane raw material, stir at 60 r / min for 4 hours, and then stand to separate the n-hexane, and then repeat the adsorption three times according to the above system to obtain preliminarily purified n-hexane;

[0106] Step 2), take 13X molecular sieve, pass nitrogen / water vapor at 150°C and 92% water vapor partial pressure for 3 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 60°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 80mL / min;

[0107] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 285nm for 2.5h, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0108] Embodiment 11:

[0109] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0110] Step 1), add industrial grade n-hexane to analytical grade sulfuric acid, mix 0.5 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir at 45r / min for 3h, let stand to separate n-hexane, and repeat adsorption twice according to the above system to obtain preliminarily purified n-hexane;

[0111] Step 2), take 5A molecular sieve, pass nitrogen / water vapor at 175°C and 95% water vapor partial pressure for 2 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 50°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 60mL / min;

[0112] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 265nm for 3 hours, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0113] Embodiment 12:

[0114] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0115] Step 1), take industrial grade n-hexane (purity 97%) and add analytical grade sulfuric acid, mix 0.15 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir once for 3 hours and then stand to separate the n-hexane, and then repeat the adsorption three times according to the above system to obtain preliminarily purified n-hexane;

[0116] Step 2), take one of the 5A molecular sieves, pass nitrogen / water vapor at 175°C and 95% water vapor partial pressure for 3.5 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 55°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 100 mL / min;

[0117] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 254nm for 4 hours, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0118] Embodiment 13:

[0119] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0120] Step 1), take industrial grade n-hexane (purity 97%, the same below) and add analytical grade sulfuric acid, mix 0.2 volume of analytical grade sulfuric acid for every 100 volume of n-hexane raw material, stir at 45r / min for 2h, then stand to separate n-hexane, and repeat the adsorption twice according to the above system to obtain preliminarily purified n-hexane;

[0121] Step 2), take 5A molecular sieve, pass nitrogen / water vapor at 160°C and 88% water vapor partial pressure for 4 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 55°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 100mL / min;

[0122] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 285nm for 4 hours, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0123] Embodiment 14:

[0124] Provided is a method for preparing high-purity n-hexane, comprising the following steps:

[0125] Step 1), add industrial-grade n-hexane to analytical-grade sulfuric acid, mix 0.1 volume of analytical-grade sulfuric acid for every 100 volumes of n-hexane raw material, stir at 60 r / min for 4 hours, and then stand to separate the n-hexane, and then repeat the adsorption three times according to the above system to obtain preliminarily purified n-hexane;

[0126] Step 2), take 13X molecular sieve, pass nitrogen / water vapor at 150°C and 85% water vapor partial pressure for 3 hours, take it out and rinse it with distilled water for 3 times, and then dry it at 60°C to constant weight. The n-hexane initially purified in step 1) is further removed by the modified molecular sieve, and the flow rate is controlled at 80mL / min;

[0127] Step 3), take PACFOG-7A activated carbon fiber, irradiate the activated carbon with a long-wave ultraviolet LED lamp with a main wavelength of 265nm for 2.5h, and filter the n-hexane obtained in step 2) through an activated carbon fiber adsorption column to obtain high-purity n-hexane.

[0128] Verification Example 1:

[0129] 1 L of purified n-hexane in Examples 1 to 14 was used as a verification sample, respectively, and verification was performed according to Q / CDKLHX1669-2017A. The verification results are shown in Table 1.

[0130] Table 1. Verification results

[0131]

[0132] As can be seen from Table 1 above, all specific embodiments of the preparation method of the present invention can obtain high-purity n-hexane with a purity of not less than 98%, a colorless and transparent appearance, a moisture content of not more than 0.05%, an evaporation residue of not more than 0.001%, and a transmittance of not less than 90% at 225 nm, which can fully meet the requirements of national standards for n-hexane, indicating that the purification method of the present invention can be used to produce high-purity n-hexane, and the purification method of the present invention is simple, the purified materials can be repeatedly recycled, and the purification cost is low.

[0133] Verification Example 2:

[0134] The purity and 215nm ultraviolet transmittance of each n-hexane verification sample in Examples 1 to 14 in Verification Example 1 were statistically analyzed. The statistical results are as follows: Figure 3 and Figure 4 shown.

[0135] Figure 3 The purity of the n-hexane samples in each example is shown by Figure 3It can be seen that the purity of n-hexane in the preferred embodiments 1 to 4 of the technical scheme of the present application is not less than 99.99%. Compared with the partial pressure percentage of water vapor of 90% in Example 1, the partial pressure percentage of water vapor in nitrogen / water vapor when the molecular sieve in the purification scheme of Example 5 is modified is 88%, and the purity of n-hexane after purification in Example 5 is 99.92%. Similarly, the purity of n-hexane after purification in Example 6 is 99.86%, the purity of n-hexane after purification in Example 7 is 99.34%, and the purity of n-hexane after purification in Example 8 is 99.10%. Comparative analysis of Examples 1 to 4 and Examples 5 to 8 shows that modifying the molecular sieve with nitrogen / water vapor having a water vapor partial pressure percentage of not less than 90% is crucial to improving the purity of the final n-hexane.

[0136] Further analysis Figure 3 In Examples 9 to 12, the wavelength of the ultraviolet light used to modify the activated carbon in Example 9 is 405 nm. It can be seen that the purity of the n-hexane obtained in its scheme is 99.95%. By comparing and analyzing Examples 10 to 12, it can be seen that the purity of the n-hexane after purification in Example 10 is 99.88%, the purity of the n-hexane after purification in Example 11 is 99.80%, and the purity after purification in Example 12 is 99.56%. Therefore, it can be clearly concluded that modifying the activated carbon with long-wave ultraviolet light of a suitable wavelength, such as 400 to 315 nm, is beneficial to the purification of n-hexane. The change in wavelength may affect the activity of the activated carbon and is not conducive to obtaining a very high-purity n-hexane product.

[0137] Figure 3 In the schemes of Example 13 and Example 14, when purifying n-hexane, the water vapor partial pressure percentage and the ultraviolet light wavelength are both outside the scheme defined by the technical scheme of the present application. As a result, it can be seen that the purity of n-hexane in Example 13 is 99.02%, and the purity of n-hexane in Example 14 is 99.06%. Although both are higher than 99% purity, they are still far from the extremely pure purity of 99.99%, indicating that the water vapor partial pressure when modifying the molecular sieve and the ultraviolet light wavelength when modifying the activated carbon have different and important influences on the purification effect.

[0138] Figure 4 The 215nm UV transmittance of n-hexane is shown by Figure 4It can be seen that the 215nm ultraviolet transmittance of n-hexane in the preferred embodiments 1 to 4 of the technical solution of the present application is not less than 98%. The high purity and high transmittance make the purified n-hexane suitable for chromatographic analysis, chromatographic separation, chromatographic preparation and other fields, expanding the scope of application. Compared with Examples 1 to 4, the partial pressure percentage of water vapor in nitrogen / water vapor when the molecular sieve in the purification scheme of Example 5 is modified is 88%, and the 215nm ultraviolet transmittance of n-hexane after purification in Example 5 is 95.8%. Similarly, the 215nm ultraviolet transmittance of n-hexane after purification in Example 6 is 95.2%, the 215nm ultraviolet transmittance of n-hexane after purification in Example 7 is 95.7%, and the 215nm ultraviolet transmittance of n-hexane after purification in Example 8 is 95.3%. Comparative analysis of Examples 1 to 4 and Examples 5 to 8 shows that compared with the modification of molecular sieves with nitrogen / water vapor at a low water vapor partial pressure, the modification of molecular sieves with nitrogen / water vapor having a water vapor partial pressure percentage of not less than 90% can significantly reduce the turbidity of n-hexane, which helps to improve the 215nm ultraviolet transmittance of n-hexane.

[0139] Further analysis Figure 4 In Examples 9 to 12, the wavelength of the ultraviolet light used to modify the activated carbon in Example 9 is 405 nm. It can be seen that the 215 nm ultraviolet transmittance of the n-hexane obtained by the scheme is 96.2%. By comparing and analyzing Examples 10 to 12, it can be seen that the 215 nm ultraviolet transmittance of the n-hexane purified in Example 10 is 96.6%, the 215 nm ultraviolet transmittance of the n-hexane purified in Example 11 is 96.4%, and the 215 nm ultraviolet transmittance of the n-hexane purified in Example 12 is 96.0%. It can be seen that compared with short-wave ultraviolet irradiation of 285-254nm, irradiation treatment of activated carbon with long-wave ultraviolet rays of 400-315nm can give activated carbon a better performance in adsorbing impurities in n-hexane. With the same irradiation treatment time, activated carbon treated with long-wave ultraviolet rays of 400-315nm can further improve the high purity and high transparency of n-hexane, and can further increase the 215nm ultraviolet transmittance to a chromatographic level of not less than 98% on the basis of the nitrogen / water vapor modified molecular sieve.

[0140] Figure 4In the schemes of Example 13 and Example 14, when purifying n-hexane, the water vapor partial pressure percentage and the ultraviolet wavelength are both outside the scheme defined by the technical scheme of the present application. As a result, it can be seen that the 215nm ultraviolet transmittance of n-hexane in Example 13 is only 94%, and the 215nm ultraviolet transmittance of n-hexane in Example 14 is only 93.6%, which is still far from the excellent 215nm ultraviolet transmittance of 98%. This shows that modifying the molecular sieve with nitrogen / water vapor with a water vapor partial pressure percentage of not less than 90% combined with irradiating the activated carbon with long-wave ultraviolet rays of 400-315nm can increase the 215nm ultraviolet transmittance of n-hexane to an extremely high transparency of not less than 98%, which is conducive to the chromatographic grade application of n-hexane.

[0141] Verification Example 3:

[0142] The inventors of the present application found in further research on chromatographic grade n-hexane that, based on the technical solution of the present application, by directly placing the molecular sieve modified by nitrogen / water vapor in room temperature, 6-10% analytical grade ammonia water for at least 5 hours, taking it out and drying it, and continuing the subsequent operation, it is possible that no impurity peak appears in the purified n-hexane, thereby providing n-hexane with high chromatographic purity. The possible reason is that the alkaline environment of ammonia water helps to change the acidic characteristics of the molecular sieve, and the NH3 in ammonia water + Ions may interact with cations in the molecular sieve (such as H + ) undergoes an exchange reaction, thereby changing the cationic composition and acidic properties of the molecular sieve, which may have different effects on the pore structure and acidic properties of the molecular sieve. The macroscopic manifestation of this effect is that the impurities in the adsorption system are adsorbed to a greater extent, so that no impurity peaks appear in the n-hexane after chemical reaction, thereby providing n-hexane of chromatographic purity.

[0143] The conventional techniques in the above embodiments are prior arts known to those skilled in the art, and thus will not be described in detail here.

[0144] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0145] Although the present invention has been described in detail and some specific embodiments have been cited, it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

[0146] Although the above-mentioned specific embodiments have been shown, described and pointed out the novel features applied to various embodiments, it should be understood that various omissions, substitutions and changes can be made to the form and details of the described device or method without departing from the spirit of the present disclosure. In addition, the above-mentioned various features and methods can be used independently of each other, or can be combined in various ways. All possible combinations and sub-combinations are intended to fall within the scope of the present disclosure. Many of the above-mentioned embodiments include similar components, and therefore, these similar components are interchangeable in different embodiments. Although the present invention has been disclosed in the context of certain embodiments and examples, it should be understood by those skilled in the art that the present invention can extend beyond the specifically disclosed embodiments to other alternative embodiments and / or applications and obvious modifications and equivalents thereof. Therefore, the present invention is not intended to be limited by the specific disclosure of the preferred embodiments herein.

[0147] Matters not covered in the present invention are all known technologies.

Claims

1. A method for preparing n-hexane, characterized in that include: Step 1), add industrial grade n-hexane to analytical grade sulfuric acid, stir, and stand to separate the n-hexane; Step 2) The n-hexane in step 1) is further impurity-removed by a modified molecular sieve; Step 3), finally, using 400-315nm long-wave ultraviolet light to modify the activated carbon to adsorb n-hexane; In the step 2), the modified molecular sieve is a molecular sieve modified by nitrogen / water vapor, and the partial pressure percentage of water vapor in the nitrogen / water vapor is not less than 90%; the molecular sieve is selected from one of 5A molecular sieve and 13X molecular sieve.

2. The method for preparing n-hexane according to claim 1, characterized in that: In the step 1), the purity of industrial grade n-hexane is 95-98%.

3. The method for preparing n-hexane according to claim 1, characterized in that: In the step 1), the volume ratio of industrial grade n-hexane to analytical grade sulfuric acid is 100:0.1-0.

5.

4. The method for preparing n-hexane according to claim 1, characterized in that: In the step 1), the stirring time is 1.5 to 5 hours.

5. The method for preparing n-hexane according to claim 1, characterized in that: In the step 2), the modified molecular sieve is specifically modified by the following steps: nitrogen / water vapor with a water vapor partial pressure percentage of not less than 90% is introduced into the molecular sieve at 150-200° C. for at least 2 hours, and after being taken out, it is rinsed with distilled water for at least 3 times and then dried at 40-60° C. to constant weight.

6. The method for preparing n-hexane according to claim 1, characterized in that: In the step 3), the long-wave ultraviolet light modified activated carbon is obtained by irradiating the activated carbon with long-wave ultraviolet rays of 400 to 315 nm for 2.5 to 5 hours.

7. A n-hexane purification system, characterized in that: It includes a feed unit, a sulfuric acid adsorption unit, a molecular sieve impurity removal unit, a modified activated carbon adsorption unit and a discharge unit, which are arranged in sequence. The feed raw material of the feed unit is industrial grade n-hexane; The molecular sieve impurity removal unit comprises: using a molecular sieve modified by nitrogen / water vapor to remove impurities from n-hexane that has completed the sulfuric acid adsorption unit; the partial pressure percentage of water vapor in the nitrogen / water vapor is not less than 90%; the molecular sieve is selected from one of 5A molecular sieve and 13X molecular sieve; The modified activated carbon adsorption unit comprises: using activated carbon modified by irradiation with long-wave ultraviolet rays of 400 to 315 nm to adsorb normal hexane that has completed the molecular sieve impurity removal unit; The purity of n-hexane discharged from the discharging unit is not less than 99.99%, and the transmittance of 215nm ultraviolet rays is not less than 98%.

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