A process for separating C6 cyclic hydrocarbons

Abstract

This application provides a method for separating C6-cyclic hydrocarbons, relating to the field of mixture separation technology. The method for separating C6-cyclic hydrocarbons provided by this application includes: mixing a C6-cyclic hydrocarbon mixture, including at least two substances selected from benzene, cyclohexane, and cyclohexene, with an adsorbent, and then separating to obtain a single component; the C6-cyclic hydrocarbon mixture is in a gaseous or liquid state. By utilizing the different affinities of the adsorbent material for the components in the C6-cyclic hydrocarbon mixture, the separation selectivity is improved, achieving efficient separation of the C6-cyclic hydrocarbon mixture and easily obtaining a single component with higher purity. This solves the problems of high energy consumption, large investment, and cumbersome processes in existing technologies for separating C6-cyclic hydrocarbon mixtures.

Description

Technical Field

[0001] This invention belongs to the field of separation technology, and in particular relates to a method for separating C6 cyclic hydrocarbons. Background Technology

[0002] Benzene, cyclohexane, and cyclohexene are three structurally similar but widely used basic chemical raw materials. In industrial production, they often exist as mixtures. For example, in the selective hydrogenation of benzene to cyclohexene, the product inevitably contains unreacted benzene and cyclohexane generated by excessive hydrogenation. To obtain high-purity target products, their binary and ternary mixtures must be effectively separated.

[0003] Current technologies have limited ability to recognize these three molecules, which are very similar in structure and polarity, resulting in poor separation effects. Therefore, there is an urgent need to develop novel and efficient adsorbents and new adsorption methods to achieve economical and efficient separation of C6 cyclic hydrocarbon mixtures.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for separating C6 cyclic hydrocarbons to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This application provides a method for separating C6 cyclic hydrocarbons, the method comprising: mixing a mixture of C6 cyclic hydrocarbons, including at least two substances selected from benzene, cyclohexane and cyclohexene, with an adsorbent, and then separating to obtain a single component; The C6 cyclic hydrocarbon mixture is in a gaseous or liquid state.

[0007] Preferably, the C6 cyclic hydrocarbon mixture further includes any one or more of toluene, ethylbenzene, styrene, o-xylene, m-xylene, and p-xylene.

[0008] Optionally, the adsorbent comprises a metal-organic framework material synthesized from metal ions and organic ligands; The pore size of the metal-organic framework material is 5 Å or larger; Preferably, the pore size of the metal-organic framework material is 5-7 Å.

[0009] Preferably, the metal ion is selected from transition metal ions and / or alkaline earth metal ions; The organic ligand is formic acid.

[0010] Preferably, the system used for separation includes a feeding device, an adsorption device, and a collecting device connected in sequence; The feeding device is used to temporarily store the C6 cyclic hydrocarbon mixture and to pass the C6 cyclic hydrocarbon mixture into the adsorption device at a certain flow rate; The adsorbent is fixedly disposed inside the adsorption device; The collection device generally includes multiple collectors, each used to collect the single component obtained after the separation of the C6 cyclic hydrocarbon mixture.

[0011] More preferably, the flow rate is 3-50 mL / min / g adsorbent.

[0012] More preferably, the adsorption device includes: a primary adsorption device A and a secondary adsorption device connected in series. Optionally, each set of primary adsorption devices A and secondary adsorption devices connected in series constitutes a unit, and the adsorption device may include multiple units, that is, the adsorption device may be composed of multiple sets of primary adsorption devices A and secondary adsorption devices connected in series; Preferably, when the C6 cyclic hydrocarbon mixture contains three components: benzene, cyclohexane, and cyclohexene, the secondary adsorption device further includes a secondary adsorption device B and a secondary adsorption device C connected in parallel.

[0013] Preferably, the separation step includes: S1: The C6 cyclic hydrocarbon mixture is fed into the primary adsorption device A by the feeding device, and the pressure of the primary adsorption device A is adjusted to perform primary adsorption, thereby obtaining the primary adsorption residue. S2: The primary adsorption residue obtained in S1 is fed into the secondary adsorption device B. The pressure of the secondary adsorption device B is adjusted to perform secondary adsorption. The resulting adsorption residue is cyclohexane, which is fed into the corresponding collector. Then, the components adsorbed by the secondary adsorption device B are desorbed to obtain cyclohexene, which is fed into the corresponding collector. S3: The components adsorbed by the primary adsorption device A after step S1 are desorbed, and the desorbed material is passed into the secondary adsorption device C. The pressure of the secondary adsorption device C is adjusted to perform secondary adsorption. The resulting adsorption residue is cyclohexene, which is passed into the corresponding collector. Then, the components adsorbed by the secondary adsorption device C are desorbed to obtain benzene, which is passed into the corresponding collector.

[0014] More preferably, the method satisfies one or more of the following conditions: a. In step S1, regulating the pressure of the primary adsorption device A includes: first increasing the pressure of the primary adsorption device A from 0 to 180-220 mbar, and then maintaining it at 180-220 mbar for adsorption; b. In step S2, adjusting the pressure of the secondary adsorption device B includes: first increasing the pressure of the secondary adsorption device B from 0 to 180-220 mbar, and then maintaining it at 180-220 mbar for secondary adsorption; c. In step S2, the pressure of the desorption treatment is 0 mbar; d. In step S3, the pressure of the desorption treatment is 0 mbar; e. In step S3, adjusting the pressure of the secondary adsorption device C includes: first increasing the pressure of the secondary adsorption device C from 0 to 80-120 mbar, and then maintaining the pressure at 80-120 mbar; f. Set the temperature of the primary adsorption device A to 70-100℃; g. Set the temperature of the secondary adsorption device B to 30-60℃; h. Set the temperature of the secondary adsorption device C to 70-100℃.

[0015] The adsorbent used in this application is a metal-organic framework material synthesized by a solvothermal reaction of metal ions and organic ligands. The specific synthesis steps are as follows: 3 grams of MgCl2 are dissolved in 50 ml of N,N-dimethylformamide, and then 5 ml of formic acid is added; the above mixture is subjected to a solvothermal reaction at a temperature of 60–140 °C for 10–60 hours. After the reaction, the obtained product [Mg3(HCOO)6] is filtered and washed with methanol; finally, it is vacuum activated at 25–100 °C for 2–24 hours to obtain the activated [Mg3(HCOO)6] material, which is the adsorbent used in this application.

[0016] The adsorption material provided in this application is a one-dimensional channel. Due to the abundance of negative potential points of the formic acid ligand, the local polarity of the channel environment is enhanced, thereby exhibiting different adsorption affinities for benzene, cyclohexene, and cyclohexane molecules. The difference in affinity results in significantly different diffusion rates for the three types of molecules, thus achieving efficient separation.

[0017] The beneficial effects of this invention are: The adsorption separation method provided in this application has simple and controllable conditions, and exhibits excellent adsorption capacity and separation selectivity in benzene-cyclohexane, benzene-cyclohexene, and cyclohexane-cyclohexene two-component mixed systems, especially in benzene-cyclohexane-cyclohexene three-component mixed systems, and has good prospects for industrial application. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the separation system provided in Example 1; Figure 2 The liquid NMR spectrum of the components separated in Example 2; Figure 3 The gas chromatogram of the cyclohexene fraction obtained in Example 3 is shown below. Figure 4 The images show the appearance of the components separated in Example 4; Figure 5 The image shows the test results for Comparative Example 1.

[0020] Reference numerals: 1-Feeding device; 2-Adsorption device; 3-Collection device. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that in the industrial production of selective hydrogenation of benzene, the C6 cyclic hydrocarbon product is usually composed of benzene, cyclohexene and cyclohexane in a molar ratio of 50:41:9. In order to better reflect the actual production conditions, the composition of the C6 cyclic hydrocarbon separated in the embodiments of the present invention is this ratio.

[0023] Example 1 This embodiment provides a separation system used in a method for adsorption separation of C6-ring hydrocarbons, such as... Figure 1 As shown: The separation system includes a feeding device 1, an adsorption device 2, and a collecting device 3 connected in sequence; wherein, the feeding device 1 is used to temporarily store the C6 cyclic hydrocarbon mixture to be separated and to pass the C6 cyclic hydrocarbon mixture into the adsorption device 2 at a certain flow rate; the adsorption device 2 is a fixed bed, and the bed adsorption zone of the fixed bed is filled with the adsorbent provided in this application; optionally, the collecting device 3 includes multiple collectors, which are used to collect the single components obtained after the separation of the C6 cyclic hydrocarbon mixture; The adsorption device includes two adsorption devices connected in series: a primary adsorption device A, a secondary adsorption device B, and a secondary adsorption device C. The secondary adsorption devices B and C are respectively connected to the primary adsorption device A, but are not connected to each other. At the same time, the secondary adsorption devices B and C are respectively connected to the collection device 3.

[0024] Example 2 This embodiment uses the separation system provided in Example 1 to perform adsorption separation of C6 cyclic hydrocarbons. The specific steps are as follows: S1: The C6 cyclic hydrocarbon mixture temporarily stored in the feed device 1 is fed into the primary adsorption device A at a flow rate of 20 mL / min / g. The pressure of the primary adsorption device A is first increased from 0 to 200 mbar, and then maintained at a pressure of 200 mbar and a temperature of 90°C for primary adsorption to obtain the primary adsorption residue. S2: The primary adsorption residue obtained in S1 is continued to be fed into the secondary adsorption unit B. The pressure of the secondary adsorption unit B is first increased from 0 to 200 mbar and then maintained at 200 mbar and 90°C for secondary adsorption. The resulting adsorption residue is cyclohexane, which is fed into the cyclohexane collector in the collection unit 3. Then, the pressure of the secondary adsorption unit B is reduced to 0 mbar, and the adsorbed components are desorbed. The desorption yields cyclohexene, which is fed into the cyclohexene collector in the collection unit 3. S3: After step S1, the pressure of the primary adsorption device A is reduced to 0 mbar, and the adsorbed components are desorbed. The desorbed material is then introduced into the secondary adsorption device C at a flow rate of 20 mL / min / g. The pressure of the secondary adsorption device C is first increased from 0 to 100 mbar and then maintained at 100 mbar and 90°C for secondary adsorption. The adsorbed residue is cyclohexene, which is then introduced into the cyclohexene collector in the collection device 3. Then, the pressure of the secondary adsorption device C is reduced to 0 mbar, and the adsorbed components are desorbed to obtain benzene, which is then introduced into the benzene collector in the collection device 3.

[0025] The liquid NMR spectra of the separated components are as follows: Figure 2 As shown.

[0026] Example 3 This embodiment uses the separation system provided in Example 1 to perform adsorption separation of C6 cyclic hydrocarbons. The specific steps are as follows: S1: The C6 cyclic hydrocarbon mixture temporarily stored in the feed device 1 is fed into the primary adsorption device A at a flow rate of 20 mL / min / g. The pressure of the primary adsorption device A is first increased from 0 to 200 mbar, and then maintained at a pressure of 200 mbar and a temperature of 80 °C for primary adsorption to obtain the primary adsorption residue. S2: The primary adsorption residue obtained in S1 is continued to be fed into the secondary adsorption unit B. The pressure of the secondary adsorption unit B is first increased from 0 to 200 mbar, and then maintained at 200 mbar and 80 °C for secondary adsorption. The resulting adsorption residue is cyclohexane, which is fed into the cyclohexane collector in the collection unit 3. Then, the pressure of the secondary adsorption unit B is reduced to 0 mbar, and the adsorbed components are desorbed. The desorption yields cyclohexene, which is fed into the cyclohexene collector in the collection unit 3. S3: After step S1, the pressure of the primary adsorption device A is reduced to 0 mbar, and the adsorbed components are desorbed. The desorbed material is then introduced into the secondary adsorption device C at a flow rate of 20 mL / min / g. The pressure of the secondary adsorption device C is first increased from 0 to 100 mbar and then maintained at 100 mbar and 80 °C for secondary adsorption. The adsorbed residue is cyclohexene, which is then introduced into the cyclohexene collector in the collection device 3. Then, the pressure of the secondary adsorption device C is reduced to 0 mbar, and the adsorbed components are desorbed to obtain benzene, which is then introduced into the benzene collector in the collection device 3.

[0027] The gas chromatogram of the separated cyclohexene fraction is shown below. Figure 3 As shown.

[0028] Example 4 This embodiment uses the separation system provided in Example 1 to perform adsorption separation of C6 cyclic hydrocarbons. The specific steps are as follows: S1: The C6 cyclic hydrocarbon mixture temporarily stored in the feed device 1 is fed into the primary adsorption device A at a flow rate of 20 mL / min / g. The pressure of the primary adsorption device A is first increased from 0 to 200 mbar, and then maintained at a pressure of 200 mbar and a temperature of 80 °C for primary adsorption to obtain the primary adsorption residue. S2: The primary adsorption residue obtained in S1 is continued to be fed into the secondary adsorption unit B. The pressure of the secondary adsorption unit B is first increased from 0 to 200 mbar, and then maintained at 200 mbar and 80 °C for secondary adsorption. The resulting adsorption residue is cyclohexane, which is fed into the cyclohexane collector in the collection unit 3. Then, the pressure of the secondary adsorption unit B is reduced to 0 mbar, and the adsorbed components are desorbed. The desorption yields cyclohexene, which is fed into the cyclohexene collector in the collection unit 3. S3: After step S1, the pressure of the primary adsorption device A is reduced to 0 mbar, and the adsorbed components are desorbed. The desorbed material is then introduced into the secondary adsorption device C at a flow rate of 20 mL / min / g. The pressure of the secondary adsorption device C is first increased from 0 to 100 mbar and then maintained at 100 mbar and 80 °C for secondary adsorption. The adsorbed residue is cyclohexene, which is then introduced into the cyclohexene collector in the collection device 3. Then, the pressure of the secondary adsorption device C is reduced to 0 mbar, and the adsorbed components are desorbed to obtain benzene, which is then introduced into the benzene collector in the collection device 3.

[0029] The appearance diagrams of the separated components are as follows: Figure 4 As shown, the left, middle, and right bottles contain benzene, cyclohexene, and cyclohexane, respectively, and the proportions of the separated products are close to the feed ratio.

[0030] Comparative Example 1 This comparative example uses a traditional method of switching elution times according to the adsorption curve to separate a mixture of C6 ring hydrocarbons. Specifically, the C6 ring hydrocarbon mixture flows directly through a fixed bed packed with the adsorbent provided in this application at atmospheric pressure. Due to the different adsorption behaviors of the adsorbent on each component of the mixture, the elution times of different components vary. Figure 5 This is the effect achieved by this testing method.

[0031] Depend on Figure 5 It is known that the purification efficiency of the traditional method of switching effluent time is not ideal, and high-purity products can only be obtained for a very short time range for cyclohexene and cyclohexane.

[0032] Therefore, this invention features a unique dual-bed pressure swing adsorption (PSA) mode, which can obtain high-purity benzene, cyclohexene, and cyclohexane through pressure swing operation, making it more valuable for practical applications.

[0033] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for separating C6 cyclic hydrocarbons, characterized in that, The method includes: mixing a mixture of C6 cyclic hydrocarbons, including at least two of benzene, cyclohexane and cyclohexene, with an adsorbent, and then separating to obtain a single component; The C6 cyclic hydrocarbon mixture is in a gaseous or liquid state.

2. The method according to claim 1, characterized in that, The C6 cyclic hydrocarbon mixture further includes any one or more of toluene, ethylbenzene, styrene, o-xylene, m-xylene, and p-xylene.

3. The method according to claim 1, characterized in that, The adsorbent includes metal-organic framework materials synthesized from metal ions and organic ligands; The pore size of the metal-organic framework material is 5 Å or larger; Preferably, the pore size of the metal-organic framework material is 5-7 Å.

4. The method according to claim 3, characterized in that, The metal ions are selected from transition metal ions and / or alkaline earth metal ions. The organic ligand is formic acid.

5. The method according to any one of claims 1-4, characterized in that, The separation system includes a feeding device, an adsorption device, and a collection device connected in sequence. The feeding device is used to temporarily store the C6 cyclic hydrocarbon mixture and to pass the C6 cyclic hydrocarbon mixture into the adsorption device at a certain flow rate; The adsorbent is fixedly disposed inside the adsorption device; The collection device generally includes multiple collectors, each used to collect the single component obtained after the separation of the C6 cyclic hydrocarbon mixture.

6. The method according to claim 5, characterized in that, The specific flow rate is 3-50 mL / min / g of adsorbent.

7. The method according to claim 5, characterized in that, The adsorption device includes a primary adsorption device A and a secondary adsorption device connected in series.

8. The method according to claim 7, characterized in that, When the C6 cyclic hydrocarbon mixture contains three components: benzene, cyclohexane, and cyclohexene, the secondary adsorption device further includes a secondary adsorption device B and a secondary adsorption device C connected in parallel.

9. The method according to claim 8, characterized in that, The separation steps include: S1: The C6 cyclic hydrocarbon mixture is fed into the primary adsorption device A by the feeding device, and the pressure of the primary adsorption device A is adjusted to perform primary adsorption, thereby obtaining the primary adsorption residue. S2: The primary adsorption residue obtained in S1 is fed into the secondary adsorption device B. The pressure of the secondary adsorption device B is adjusted to perform secondary adsorption. The resulting adsorption residue is cyclohexane, which is fed into the corresponding collector. Then, the components adsorbed by the secondary adsorption device B are desorbed to obtain cyclohexene, which is fed into the corresponding collector. S3: The components adsorbed by the primary adsorption device A after step S1 are desorbed, and the desorbed material is passed into the secondary adsorption device C. The pressure of the secondary adsorption device C is adjusted to perform secondary adsorption. The resulting adsorption residue is cyclohexene, which is passed into the corresponding collector. Then, the components adsorbed by the secondary adsorption device C are desorbed to obtain benzene, which is passed into the corresponding collector.

10. The method according to claim 9, characterized in that, The method satisfies one or more of the following conditions: a. In step S1, regulating the pressure of the primary adsorption device A includes: first increasing the pressure of the primary adsorption device A from 0 to 180-220 mbar, and then maintaining it at 180-220 mbar for adsorption; b. In step S2, adjusting the pressure of the secondary adsorption device B includes: first increasing the pressure of the secondary adsorption device B from 0 to 180-220 mbar, and then maintaining it at 180-220 mbar for secondary adsorption; c. In step S2, the pressure of the desorption treatment is 0 mbar; d. In step S3, the pressure of the desorption treatment is 0 mbar; e. In step S3, adjusting the pressure of the secondary adsorption device C includes: first increasing the pressure of the secondary adsorption device C from 0 to 80-120 mbar, and then maintaining the pressure at 80-120 mbar; f. Set the temperature of the primary adsorption device A to 70-100℃; g. Set the temperature of the secondary adsorption device B to 30-60℃; h. Set the temperature of the secondary adsorption device C to 70-100℃.

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