A process suitable for the production of chromatographic grade cyclohexane
By combining fuming sulfuric acid with molecular sieves and alumina adsorption filtration, the problem of substandard optical properties of chromatographic grade cyclohexane in existing technologies has been solved, achieving efficient and low-cost production of chromatographic grade cyclohexane.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHENGDU KELONG CHEM CO LTD
- Filing Date
- 2022-10-18
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies are insufficient to produce cyclohexane that meets the high optical performance requirements of chromatographic grade, and the preparation process is complex, costly, and contains high levels of impurities, making it difficult to meet market demand.
A method combining fuming sulfuric acid with molecular sieve and alumina adsorption filtration was adopted. Fuming sulfuric acid was used to remove impurities, followed by washing with pure water. Then, activated alumina and 10X molecular sieve were used for deep adsorption filtration. Finally, chromatographic grade cyclohexane with optical properties superior to existing technologies was obtained by distillation.
The production of chromatographic grade cyclohexane with high optical performance has been achieved. The process is simple, requires less auxiliary agent, and has controllable costs, meeting market demands.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of cyclohexane purification technology, and in particular to a method for producing chromatographic grade cyclohexane. Background Technology
[0002] Cyclohexane is an organic compound with the chemical formula C6H12H2O. 12 It is a colorless liquid with a pungent odor, insoluble in water, but soluble in most organic solvents such as ethanol, ether, benzene, and acetone. Its density is 0.79 g / cm³. 3 Cyclohexane has a boiling point of 80.7℃ and is relatively stable to acids and alkalis. It does not react with moderately concentrated nitric acid or mixed acids at low temperatures. Cyclohexane is mainly used as a solvent for rubber and coatings. Due to its low toxicity, it is often used to replace benzene for degreasing, delubrication, and paint removal. It can also be used as an analytical reagent, such as a standard substance for chromatographic analysis. In industrial production, cyclohexane is mainly produced by the benzene hydrogenation process. Therefore, the cyclohexane raw material often contains a certain amount of impurities such as benzene, cyclohexanol, and cyclohexanone, which cannot meet the purity requirement of not less than 99.9% for chromatographic analysis (mainly optical requirements). To obtain chromatographic-grade cyclohexane, the cyclohexane raw material needs to be purified to remove impurities. The usual method is a combination of decolorization, adsorption, and distillation. This not only leads to a long preparation cycle, high energy consumption and cost, but also results in insufficient purity of the purified cyclohexane, with high impurity content and poor optical properties, making it difficult to meet chromatographic-grade requirements.
[0003] Chinese patent CN107522588A discloses a method and system for preparing chromatographic grade cyclohexane. The method uses cyclohexane as a raw material, first reacting it with concentrated sulfuric acid, then neutralizing and washing it with water and sodium carbonate. The cyclohexane is then adsorbed through a 4A molecular sieve and activated silica gel, followed by the addition of phosphorus pentoxide and distillation. However, the chromatographic grade cyclohexane prepared by this method exhibits maximum absorbances of 0.033-0.035, 0.14-0.15, 0.045-0.050, 0.021-0.022, and 0.013 at ultraviolet wavelengths of 220nm, 230nm, 240nm, 250nm, and 260nm, respectively. While these values meet the basic optical requirements for chromatographic grade cyclohexane, their optical properties are poor and cannot satisfy the high demands of the market for chromatographic grade cyclohexane products.
[0004] Chinese patent CN106854134A discloses a method for preparing chromatographic grade cyclohexane. Under ice bath conditions, 105% sulfuric acid is added to cyclohexane, stirred, and the sulfuric acid layer is removed by separation. Then, it is washed with 10% sodium hydroxide, dried with a drying agent, dehydrated, and fractionated to obtain the final product. The ultraviolet transmittance of the chromatographic grade cyclohexane prepared by this patent is 0.556 (absorbance 0.255) at 220nm, 0.821 (absorbance 0.0856) at 230nm, 0.944 (absorbance 0.0250) at 240nm, and 0.994 (absorbance 0.0026) at 250nm. However, the optical properties of the chromatographic grade cyclohexane prepared by the inventor according to Example 1 of this patent are as follows: the maximum absorbance at ultraviolet wavelengths of 202nm, 205nm, 210nm, 250nm, and 254nm are 1.012, 0.920, 0.726, 0.004, and 0.005, respectively. These optical properties do not meet the relevant requirements and cannot satisfy the high requirements of market customers for chromatographic grade cyclohexane products. Summary of the Invention
[0005] The purpose of this invention is to provide a production method suitable for chromatographic grade cyclohexane, addressing the aforementioned problems. This invention uses fuming sulfuric acid, combined with molecular sieves and alumina adsorption filtration, to obtain chromatographic grade cyclohexane products with optical properties that meet market customer requirements. The preparation process is not complicated, the consumption of auxiliary agents is low, and the cost is within a controllable range, overcoming the shortcomings of existing chromatographic grade cyclohexane production processes.
[0006] The technical solution adopted in this invention is as follows: A method for producing chromatographic grade cyclohexane, comprising the following steps:
[0007] A. Take cyclohexane raw material, add fuming sulfuric acid to the cyclohexane raw material, stir and let stand, then separate cyclohexane;
[0008] B. Add pure water to the cyclohexane obtained in step A, stir and let stand, then separate the cyclohexane.
[0009] C. Add activated alumina and 10X molecular sieve to the cyclohexane obtained in step B, stir and let stand, then filter.
[0010] D. Distill the cyclohexane obtained in step C to obtain chromatographic grade cyclohexane.
[0011] In the production method of this invention, fuming sulfuric acid is mainly used to remove impurities from cyclohexane. Its impurity removal effect is related to its usage and the content of sulfur trioxide. Experiments have shown that a volume ratio of cyclohexane to fuming sulfuric acid of 180-220:1 is suitable, for example, 180:1, 185:1, 188:1, 190:1, 192:1, 195:1, 200:1, 210:1, 220:1, etc., preferably 200:1. The sulfur trioxide content in the fuming sulfuric acid is suitable to be 18-22 wt%, for example, 18 wt%, 18.5 wt%, 19 wt%, 19.5 wt%, 20 wt%, 21 wt%, 22 wt%, etc., preferably 20 wt%. If the volume ratio of cyclohexane to fuming sulfuric acid is too small, the impurity removal effect is poor; conversely, if the volume ratio is too large, the reaction is too vigorous, producing other impurities that affect absorbance. Correspondingly, if the sulfur trioxide content in fuming sulfuric acid is less than 18%, the impurity removal effect will be poor; conversely, if the sulfur trioxide content is higher than 22%, other impurities that affect absorbance will be generated during the impurity removal process.
[0012] Furthermore, in step B, after the fuming sulfuric acid purification treatment, this invention does not use alkali to neutralize the remaining sulfuric acid, but directly adds a certain amount of pure water for washing. This satisfies the acid removal requirements while avoiding the introduction of new impurities, ensuring the effectiveness of the sulfuric acid purification. In this invention, the amount of pure water added is 1 / (10-20) of the volume of the cyclohexane raw material in step A, which can be 1 / 10, 1 / 12, 1 / 13, 1 / 15, 1 / 16, 1 / 17, 1 / 18, 1 / 20, etc., preferably 1 / 15.
[0013] Furthermore, in step C, after washing with pure water, the product is directly adsorbed and filtered using activated alumina and 10X molecular sieve. Activated alumina is mainly used to adsorb residual pure water, while 10X molecular sieve can not only further remove water but also further adsorb impurities in the product. In this invention, activated alumina and 10X molecular sieve are used in combination to achieve excellent deep adsorption and filtration effects. Experiments have shown that the amount of each significantly affects the adsorption effect, resulting in substantial variations in the optical properties of the chromatographic grade cyclohexane. By examining the range of amounts of activated alumina and 10X molecular sieve used, the inventors determined that, based on the amount of cyclohexane used in step A, the appropriate amount of activated alumina is 15-25 g / L, such as 15 g / L, 16 g / L, 18 g / L, 20 g / L, 22 g / L, or 25 g / L, with 20 g / L being preferred. The appropriate amount of 10X molecular sieve is 2-4 g / L, such as 2 g / L, 2.2 g / L, 2.5 g / L, 3 g / L, 3.2 g / L, 3.33 g / L, 3.5 g / L, 3.6 g / L, or 4 g / L, with 3.33 g / L being preferred. Correspondingly, if the amount of activated alumina and 10X molecular sieve used is too high, they will adsorb too much cyclohexane product, resulting in a decrease in product yield.
[0014] Further, in step D, the product is collected by distillation at 80-81°C to obtain chromatographic grade cyclohexane.
[0015] Furthermore, during the distillation process in step D, after total reflux for 2 hours, the product is collected at 80-81°C by re-distillation.
[0016] In summary, due to the adoption of the above technical solutions, the beneficial effects of this invention are as follows: This invention uses fuming sulfuric acid cyclohexane as raw material for impurity removal, then washes it directly with pure water, and after washing, combines molecular sieves and alumina for adsorption filtration. Finally, it is distilled to obtain chromatographic grade cyclohexane products with optical properties that meet the needs of market customers. The optical properties are superior to those of chromatographic grade cyclohexane obtained in the prior art. The preparation process of this invention is not complicated, the consumption of auxiliary agents is low, and the cost is within a controllable range. It achieves the goal of industrial production of chromatographic grade cyclohexane with high optical properties and overcomes the shortcomings of existing chromatographic grade cyclohexane production processes. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0018] Example 1
[0019] A method for producing chromatographic grade cyclohexane includes the following steps:
[0020] S1. Accurately weigh 30L of cyclohexane raw material (analytical grade) into a three-necked flask, add 150mL of fuming sulfuric acid with a SO3 mass fraction of 20% into the three-necked flask, stir for 3h, and then let it stand to separate into layers.
[0021] S2. Add 2L of pure water to the extracted cyclohexane, stir for 3 hours, and let stand to separate the layers.
[0022] S3. Add 600g of activated alumina and 100g of 10X molecular sieve to the cyclohexane separated in step S2, stir for 5 hours, and let stand and filter.
[0023] S4. Transfer the cyclohexane obtained in step S3 into a three-necked flask for distillation. After total reflux for 2 hours, collect the product at 80-81℃ to obtain chromatographic grade cyclohexane.
[0024] Example 2
[0025] A method for producing chromatographic grade cyclohexane includes the following steps:
[0026] S1. Take 1L of the same cyclohexane raw material as in Example 1 and transfer it into a three-necked flask. Add 5mL of fuming sulfuric acid with a SO3 mass fraction of 20% to the three-necked flask, stir for 2 hours, and then let it stand to separate the acid layer.
[0027] S2. Add 70 mL of pure water to the obtained cyclohexane, stir for 2 hours, and let stand to separate the water layer.
[0028] S3. Add 21g of activated alumina and 3.5g of 10X molecular sieve to the cyclohexane obtained in step S2, stir for 4 hours, and let stand and filter.
[0029] S4. Transfer the cyclohexane obtained in step S3 into a three-necked flask for distillation. After total reflux for 2 hours, collect the product at 80-81℃ to obtain chromatographic grade cyclohexane.
[0030] Example 3
[0031] A method for producing chromatographic grade cyclohexane includes the following steps:
[0032] S1. Take 1L of the same cyclohexane raw material as in Example 1 and transfer it into a three-necked flask. Add 6mL of fuming sulfuric acid with a SO3 mass fraction of 19% to the three-necked flask, stir for 2 hours, and then let it stand to separate the acid layer.
[0033] S2. Add 65 mL of pure water to the obtained cyclohexane, stir for 2 hours, and let stand to separate the water layer.
[0034] S3. Add 22g of activated alumina and 3g of 10X molecular sieve to the cyclohexane obtained in step S2, stir for 4 hours, and let stand and filter.
[0035] S4. Transfer the cyclohexane obtained in step S3 into a three-necked flask for distillation. After total reflux for 2 hours, collect the product at 80-81℃ to obtain chromatographic grade cyclohexane.
[0036] Comparative Example 1
[0037] Using Example 1 as a comparison, 30L of cyclohexane with the same raw material was placed in a three-necked flask. 150mL of fuming sulfuric acid with a SO3 mass fraction of 20% was added to the three-necked flask. After stirring for 3 hours, the mixture was allowed to stand and separate into layers. Then, 2L of pure water was added to the cyclohexane that was taken out. After stirring for 3 hours, the mixture was allowed to stand and separate into layers. Finally, the cyclohexane washed with pure water was transferred to a three-necked flask for distillation. After total reflux for 2 hours, the product was collected at 80-81℃.
[0038] Comparative Example 2
[0039] Using Example 1 as a comparison, 30L of cyclohexane with the same raw material was placed in a three-necked flask, 2L of pure water was added, and the mixture was stirred for 3 hours and allowed to stand for separation. Then, 600g of activated alumina and 100g of 10X molecular sieve were added to the cyclohexane washed with pure water, and the mixture was stirred for 5 hours and allowed to stand for filtration. Finally, the obtained cyclohexane was transferred to a three-necked flask for distillation. After total reflux for 2 hours, the product was collected at 80-81℃.
[0040] Comparative Example 3
[0041] Taking Example 1 of Patent 106854134A as an example:
[0042] (1) Under ice-water bath conditions, take 1L of cyclohexane (analytical grade) with the same raw material as in Example 1 into a three-necked flask, keep the temperature between 20-25℃, add 40mL of 105% sulfuric acid under stirring, continue stirring for 1h, and separate the sulfuric acid layer.
[0043] (2) Add 500 mL of 10% sodium hydroxide solution to a three-necked flask, stir for 1 h, after washing, separate the aqueous layer, then add 50 g of anhydrous sodium sulfate, and let stand to dry for 1 h.
[0044] (3) Transfer the dried cyclohexane into a three-necked flask for distillation. After total reflux for 2 hours, collect the product at 80-81℃.
[0045] Comparative Example 4
[0046] Comparative Example 4 is the same as Example 1, except that the mass fraction of SO3 in the fuming sulfuric acid is 30%.
[0047] Comparative Example 5
[0048] Comparative Example 5 is the same as Example 1, except that the 10X molecular sieve is replaced with 4A molecular sieve.
[0049] Comparative Example 6
[0050] Comparative Example 5 is the same as Example 1, except that the activated alumina is replaced with anhydrous sodium sulfate.
[0051] The cyclohexane products obtained in Examples 1-3 and Comparative Examples 1-6 were tested. The optical parameters were measured using a RAYLEIGH UV-1801 UV / Vis spectrophotometer. The results are shown in Table 1.
[0052] Table 1. Detection results of the examples and comparative samples.
[0053]
[0054] Table 1 shows that the optical properties of the chromatographic grade cyclohexane obtained in Examples 1-3 are superior to those of the chromatographic grade cyclohexane obtained in Comparative Examples 1-6. Furthermore, the test results of Comparative Example 1 show that when activated alumina and 10X molecular sieve filtration adsorption were not performed, the optical properties of the obtained chromatographic grade cyclohexane were very poor and did not meet the requirements. The test results of Comparative Example 2 show that when fuming sulfuric acid was not used for treatment, although the optical properties of the obtained chromatographic grade cyclohexane were similar to those of the chromatographic grade cyclohexane in Example 1, the difference in absorbance increased with increasing wavelength. Therefore, its optical properties still could not meet the high standards of the market. This indicates that the use of fuming sulfuric acid can further purify the chromatographic grade cyclohexane, enabling its optical properties to meet high standards. The test results of Comparative Example 3 show that existing proprietary... The method for preparing chromatographic grade cyclohexane disclosed in CN106854134A does not have the optical properties described. At wavelengths of 250 nm and 254 nm, the absorbance of the chromatographic grade cyclohexane is higher than that of the chromatographic grade cyclohexane in Examples 1-3 of this invention. This indicates that the method of this invention is superior to the patented technology. The test results of Comparative Example 4 show that when the sulfur trioxide content is higher than 22%, impurities affecting absorbance are generated in the cyclohexane, resulting in substandard optical properties. The test results of Comparative Examples 5 and 6 show that when activated alumina and 10X molecular sieve are replaced respectively, the optical properties of the obtained chromatographic grade cyclohexane do not meet the high standard requirements. This indicates that the use of activated alumina and 10X molecular sieve has achieved unexpected technical effects and can be used to produce high-standard chromatographic grade cyclohexane products.
[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for producing chromatographic grade cyclohexane, characterized in that, Includes the following steps: A. Take cyclohexane as raw material, add fuming sulfuric acid to the cyclohexane raw material, stir and let stand, then separate the cyclohexane; the volume ratio of the cyclohexane raw material to the fuming sulfuric acid is 180-220:1, and the sulfur trioxide content in the fuming sulfuric acid is 18-22% wt%. B. Add pure water to the cyclohexane obtained in step A, stir and let stand, then separate the cyclohexane. C. Add activated alumina and 10X molecular sieve to the cyclohexane obtained in step B, stir and let stand, then filter; based on the amount of cyclohexane raw material used in step A, the amount of activated alumina added is 15-25 g / L, and the amount of 10X molecular sieve added is 2-4 g / L. D. Distill the cyclohexane obtained in step C to obtain chromatographic grade cyclohexane.
2. The method for producing chromatographic grade cyclohexane as described in claim 1, characterized in that, The volume ratio of the cyclohexane feedstock to the fuming sulfuric acid is 200:1, and the sulfur trioxide content in the fuming sulfuric acid is 20w.
3. The method for producing chromatographic grade cyclohexane as described in claim 1, characterized in that, In step B, the amount of pure water added is 1 / (10-20) of the amount of cyclohexane raw material used in step A.
4. The method for producing chromatographic grade cyclohexane as described in claim 3, characterized in that, In step B, the amount of pure water added is 1 / 15 of the volume of the cyclohexane feedstock in step A.
5. The method for producing chromatographic grade cyclohexane as described in claim 1, characterized in that, In step C, based on the amount of cyclohexane raw material used in step A, the amount of activated alumina added is 20 g / L, and the amount of 10X molecular sieve added is 3.33 g / L.
6. The method for producing chromatographic grade cyclohexane as described in claim 1, characterized in that, In step D, the product is collected by distillation at 80-81°C to obtain chromatographic grade cyclohexane.
7. The method for producing chromatographic grade cyclohexane as described in claim 1, characterized in that, During the distillation process in step D, after total reflux for 2 hours, the product is collected at 80-81℃ by re-distillation.
8. The method for producing chromatographic grade cyclohexane as described in claim 1, characterized in that, The stirring time is 2-6 hours.