Use of zif-8 material for separating c5 hydrocarbons

Abstract

The application belongs to the field of material and chemical process research, and is characterized in that it relates to application of ZIF-8 material in separation of C5 hydrocarbon compounds. The ZIF-8 material has simple manufacturing steps, can be synthesized on a large scale, and uses deionized water as a solvent, so that green synthesis can be realized. The ZIF-8 material and its composite material realize purification of isoprene in steam and liquid phase C5 mixture. The ZIF-8 material is very easy to regenerate after adsorption and can be recycled.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of material and chemical process research, and is characterized by involving the application of ZIF-8 material in separating C5 hydrocarbons. BACKGROUND

[0002] C5 fraction is an important and potentially valuable chemical raw material. The yield, composition and content of the cracked C5 fraction mainly depend on the composition of the cracking raw material. The lighter the cracking raw material, the lower the C5 yield. The C5 fraction contains more than twenty components with close boiling points, mainly including dienes (isoprene and piperonalene, etc.), mono-olefins (1-pentene and 2-pentene, etc.) and alkanes (n-pentane and isopentane). Among them, isoprene has higher utilization value and higher content. Isoprene is mainly used to produce polyisoprene rubber with performance close to natural rubber, and is also the second monomer of butyl rubber and styrene-isoprene block polymer (SIS) thermoplastic elastomer. Isoprene is an extremely important carbon five diene, which is an important monomer for synthetic rubber, mainly used for the synthesis of isoprene rubber, and its production ranks the third among synthetic rubbers, only next to butadiene-styrene rubber and cis-butadiene rubber. In recent years, due to the rapid rise in the price of natural rubber, the production of isoprene rubber has increased, providing opportunities for the application of isoprene in the field of rubber. Isoprene can also be used as a co-monomer for the synthesis of butyl rubber to improve the vulcanization performance of butyl rubber.

[0003] The C5 fraction has a complex composition, the components have close boiling points, the relative volatility is small, they are easy to form azeotropes with each other, and the dienes are easy to polymerize, so it is difficult to separate high-purity isoprene products. At present, the method commonly used in industry is multi-step extractive distillation and azeotropic distillation to obtain pure components for polymerization. The methods of extractive distillation or azeotropic distillation generally have the problems of high energy consumption, large equipment investment, complex operation process, large solvent consumption, environmental unfriendliness, etc.

[0004] Adsorption separation technology is considered as a potential separation technology due to its convenient operation, economical equipment cost and low production energy consumption. Traditional adsorption materials such as porous polymers, molecular sieves and activated carbon have been widely used in the field of adsorption separation, but these materials generally have the limitations of difficulty in controlling pore size and insufficient molecular recognition ability for slightly different size molecules.

[0005] Metal-organic framework materials have been widely used in the research field of low carbon hydrocarbon adsorption separation. In recent years, many studies have reported the adsorption separation of gaseous carbon hydrocarbons such as ethylene / ethane and propylene / propane, and the adsorption separation of liquid carbon hydrocarbons such as C6-C8 has also been very mature, but the study of carbon five compounds is very few. For example, Michael Maes et al. first reported the selective adsorption separation of cis / trans-piperylene by using MIL-96, chabazite and 5A molecular sieve, but the adsorption separation selectivity is not high. Huabin Xing et al. used ion hybrid microporous material ZU-62 and TIFSIX-2-Cu-i for the separation of isoprene, although the regeneration performance of the material is good, but at 0.1 bar (298k), there is still a large adsorption amount of isoprene, which cannot achieve the effect of screening, and the separation selectivity is not high. Zongbi Bao's group used zeolite 5A and gallic acid MOF in combination to realize the separation of C5 dienes, although the study has high selectivity, but cannot realize one-step separation.

[0006] Therefore, for the separation application of metal-organic framework materials in multi-component C5 carbon hydrocarbons, it is of great significance to develop new separation materials and separation methods to realize the screening separation of isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane five-component mixed system. SUMMARY

[0007] Based on the research in the field, the application provides an application of ZIF-8 material in separating five C5 carbon hydrocarbons, and specifically relates to the screening of C5 carbon hydrocarbons by using ZIF-8 material in steam and liquid phase separation.

[0008] The application is realized by the following technical scheme:

[0009] The application provides a preparation method of ZIF-8 material in a crystal form, which comprises the following steps:

[0010] Dissolve zinc nitrate hexahydrate in methanol to form transparent solution A; dissolve 2-methylimidazole (2-MIm) in methanol to form transparent solution B; then pour transparent solution B into transparent solution A; stir the mixed solution at room temperature for 6-30 hours at a speed of 500-1000 revolutions / minute, and then stand for 1-24 hours; centrifuge and wash several times with methanol, and then dry at 50-100°C.

[0011] Further, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:4; the addition amount of methanol in transparent solution A is 75mL of methanol corresponding to 0.01mmol of Zn(NO3)2·6H2O; and the volume ratio of methanol in transparent solution A and transparent solution B is 1:1.

[0012] The application further provides a green mass production method of the ZIF-8 material, comprising the following steps: dissolving zinc acetate dihydrate and 2-methylimidazole in deionized water respectively to form two clear solutions; then quickly pouring the zinc acetate dihydrate solution into the 2-methylimidazole solution, quickly stirring for 30 minutes, and standing for 24 hours; after centrifugation, washing three times with methanol, then soaking in methanol for 48 hours, replacing the fresh methanol 3-6 times during the period, and vacuum drying at 100 DEG C to obtain the ZIF-8 material.

[0013] Further, the molar ratio of the zinc acetate dihydrate to the 2-methylimidazole is 1:8, the amount of the deionized water added in the preparation of the zinc acetate dihydrate is limited to 1.8 L of deionized water corresponding to 0.34 mol of the zinc acetate dihydrate, and the volume ratio of the deionized water of the two clear solutions is 1:1.

[0014] Further, the ZIF-8 material activation method is to heat the sample under vacuum, and the temperature of the vacuum drying is 30-120 DEG C and the time is 6-24 hours.

[0015] The application further provides the application of the ZIF-8 material in separating C5 hydrocarbons.

[0016] Further, the C5 hydrocarbons include isoprene and at least one of 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane.

[0017] Further, the ZIF-8 material realizes the screening of C5 hydrocarbon steam and liquid.

[0018] Further, the ZIF-8 material can be recycled, and the regeneration method is to heat the ZIF-8 material to 30-120 DEG C under vacuum or inert gas atmosphere for 6-24 hours, and the inert gas is nitrogen or helium.

[0019] The application further provides the application of the ZIF-8 composite material in separating five kinds of C5 hydrocarbons.

[0020] Further, the preparation method of the ZIF-8 composite material is to add a binder CMC and activated carbon to the dried ZIF-8 material sample to obtain ZIF-8 composite material particles by extrusion molding. The content of the binder CMC is 0.5%-30%, and the content of the activated carbon is 0%-30%.

[0021] Compared with the prior art, the application has the following beneficial effects.

[0022] (1) The ZIF-8 material preparation step is simple, can be synthesized on a large scale, and uses deionized water as a solvent, which can achieve green synthesis. The MOF material can be combined with a binder and extruded into a composite material. The obtained composite material overcomes the shortcomings of powder adsorbents blocking the pipeline and being difficult to recover. The ZIF-8 material prepared by a green and large-scale method and the composite material prepared by combining ZIF-8 and a binder both exhibit similar sieving effects.

[0023] (2) The ZIF-8 material and its composite material achieve the sieving separation of five kinds of C5 mixtures.

[0024] (3) The ZIF-8 material can be used for the purification of isoprene in vapor and liquid phases.

[0025] (4) The ZIF-8 material is very easy to regenerate after adsorption and can be recycled. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 PXRD of ZIF-8 crystal sample, green large-scale synthesis sample and simulated powder X-ray diffraction pattern.

[0027] Figure 2 N2 adsorption isotherm of ZIF-8 material at 77 K.

[0028] Figure 3 Schematic diagram of fixed penetration device.

[0029] Figure 4 Fixed bed penetration diagram of ZIF-8 material at 273 K bubbling and 298 K testing.

[0030] Figure 5 Adsorption isotherm of ZIF-8 material at 298 K for isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane.

[0031] Figure 6 Adsorption isotherm of ZIF-8 material at 308 K for isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane.

[0032] Figure 7 Adsorption isotherm of ZIF-8 material at 318 K for isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane.

[0033] Figure 8 Adsorption rate test device diagram.

[0034] Figure 9Adsorption rate curves for ZIF-8 material at 298 K for isoprene, 1-pentene, cis-2-pentene, trans-2-pentene, and n-pentane.

[0035] Figure 10 Adsorption rate curves for ZIF-8 material at 308 K for isoprene, 1-pentene, cis-2-pentene, trans-2-pentene, and n-pentane.

[0036] Figure 11 Adsorption rate curves for ZIF-8 material at 318 K for isoprene, 1-pentene, cis-2-pentene, trans-2-pentene, and n-pentane.

[0037] Figure 12 Fixed bed breakthrough 5-cycle plot for ZIF-8 material at 273 K for bubbling.

[0038] Figure 13 Plot of concentration change of various components in liquid phase adsorption experiments for ZIF-8 material.

[0039] Figure 14 N2 adsorption isotherm at 77 K for ZIF-8 composite material after extrusion for Example 3 and Example 4.

[0040] Figure 15 Adsorption rate curves for ZIF-8 / CMC2 prepared in Example 3 at 298 K for isoprene, and n-pentane.

[0041] Figure 16 Adsorption rate curves for ZIF-8 / CMC2-AC1 prepared in Example 4 at 298 K for isoprene, and n-pentane.

[0042] Figure 17 Fixed bed breakthrough plot for ZIF-8 / CMC2 prepared in Example 3 at 273 K for bubbling, tested at 298 K.

[0043] Figure 18 Fixed bed breakthrough plot for ZIF-8 / CMC2-AC1 prepared in Example 4 at 273 K for bubbling, tested at 298 K.

[0044] Figure 19 Liquid phase breakthrough experiment results plot for ZIF-8 / CMC2-AC1 prepared in Example 4 at 298 K.

[0045] Figure 20 Breakthrough plot for various components in C5 fraction in simulated industrial production. DETAILED DESCRIPTION

[0046] The application will be further described in connection with the following examples, but the application is not limited to the following examples.

[0047] Example 1 Synthesis of ZIF-8 crystal sample

[0048] First step: Zn (NO3) 2·6H2O (5.95 g, 0.02 mol) was dissolved in 150 mL methanol to form a transparent solution A;

[0049] 2-methylimidazole (2-MeIm; 6.16 g, 0.08 mol) was dissolved in 150 mL methanol to form a transparent solution B;

[0050] Then, the transparent solution B was poured into the transparent solution A; the mixed solution was stirred at room temperature for 6-30 hours at a speed of 500-1000 revolutions per minute, and then was left to stand for 1-12 hours to obtain a ZIF-8 crystal sample.

[0051] Second step: In order to remove the solvent molecules in the channels of the ZIF-8 crystal sample, the crystal sample obtained above was washed with high-purity methanol and then was immersed in a methanol solvent, and the solvent exchange was continued for 3-6 times, and the exchanged crystal sample was transferred to a fresh methanol solvent.

[0052] Example 2 Large-scale synthesis of ZIF-8 sample

[0053] First step: Zinc acetate dihydrate (0.34 mol) and 2-methylimidazole (2.72 mol) were dissolved in 1.8 L deionized water to form two clear solutions respectively. Then, the zinc acetate dihydrate solution was quickly poured into the 2-methylimidazole solution, and was quickly stirred for 30 minutes, and was left to stand for 24 hours.

[0054] Second step: In order to remove the solvent molecules in the channels of the ZIF-8 sample material, the ZIF-8 sample obtained above was washed with high-purity methanol and then was immersed in a methanol solvent, and the solvent exchange was continued for 3-6 times. The exchanged ZIF-8 sample was transferred to a fresh methanol solvent.

[0055] Powder X-ray diffraction characterization test

[0056] The ZIF-8 samples prepared in Example 1 and Example 2 were subjected to powder X-ray diffraction characterization test, and the test results are shown in Figure 1 As can be seen, the PXRD of ZIF-8 and ZIF-8-H2O synthesized in methanol or deionized water is consistent with each peak of the simulated XRD of ZIF-8, indicating that both methods can successfully prepare ZIF-8 samples, i.e. the ZIF-8 samples have been successfully synthesized.

[0057] Separation performance test

[0058] Prior to performing the adsorption isotherm test, the methanol suspension of the sample from the second step of Example 1 and Example 2 was centrifuged at 5000 rpm for 5 minutes, the supernatant was discarded, and the material was desolvated by degassing at 80 °C for 12 hours to obtain the desolvated dry sample. 50-100 mg of the desolvated dry sample was loaded into the adsorption tube and connected to the adsorption instrument to perform the adsorption isotherm test.

[0059] (1) Nitrogen adsorption test

[0060] Prior to the test, vacuum degassing was performed, and after the degassing was completed, nitrogen adsorption at 77 K was tested. The test results of the samples obtained from Example 1 and Example 2 were the same, as shown in Figure 2 The material showed a reversible typical Type I N2 adsorption isotherm, with the adsorption and desorption branches closed, without hysteresis, indicating its inherent microporosity characteristics.

[0061] (2) Adsorption isotherm test of isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane

[0062] The test results of the samples obtained from Example 1 and Example 2 were the same, as shown in Figures 5-7 , Figure 5 , Figure 6 , Figure 7 Adsorption isotherms of isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane at 298 K, 308 K and 318 K for the samples obtained from Example 1 and Example 2. The adsorption amount of ZIF-8 for isoprene at 298 K and 0.1 bar was 0.01 mmol / g, while the adsorption amounts for 1-pentene, trans-2-pentene, cis-2-pentene and n-pentane were 3.8593 mmol / g, 4.1306 mmol / g, 3.8539 mmol / g, 3.2717 mmol / g, respectively. By comparing the adsorption isotherms at various temperatures, it can be seen that the adsorption amount of isoprene is significantly lower than that of the other four molecules, indicating that the ZIF-8 sample has the potential to separate isoprene from C5 hydrocarbons.

[0063] (3) Fixed bed breakthrough test of mixed isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane (v / v / v / v / v = 1 / 1 / 1 / 1 / 1)

[0064] Prior to performing the breakthrough test, the methanol suspension of the sample from the second step of Example 1 and Example 2 was centrifuged at 5000 rpm for 5 minutes, the supernatant was discarded, and the material was desolvated by degassing at 80 °C for 12 hours to obtain the desolvated dry sample. 300-1000 mg of the desolvated dry sample was loaded into the breakthrough column and connected to the breakthrough device to perform the test Figure 3). The breakthrough test results of the samples obtained from Example 1 and Example 2 are the same (see Figure 4 ), Figure 4 The breakthrough plot of ZIF-8 material at 273 K for bubbling and 298 K for fixed bed testing. The calculated results show that when mixed steam passes through the ZIF-8 material breakthrough column, the signal of isoprene is detected immediately at the outlet, and the dynamic adsorption amounts of 1-pentene, trans-2-pentene, cis-2-pentene and n-pentane are 1.25 mmol / g, 1.11 mmol / g, 1.12 mmol / g, 1.05 mmol / g, respectively.

[0065] The recycling of adsorbents is of great significance in practical industrial applications. In order to prove the recyclability of ZIF-8 material for the separation of C5 compounds, the fixed bed breakthrough experiment was continuously carried out for 5 times. The regeneration method of ZIF-8 material is to heat ZIF-8 material to 30-120°C for 6-24 hours under vacuum or inert gas atmosphere, and the inert gas is nitrogen or helium. As shown in Figure 12 , the retention time of the adsorbent for C5 hydrocarbons is almost the same. It shows that ZIF-8 has good cycle performance and regeneration ability.

[0066] Adsorption rate test

[0067] Before carrying out the adsorption rate test, the methanol suspension liquid of the sample in the second step of Example 1 and Example 2 was centrifuged at a speed of 5000 rpm for 5 minutes, the supernatant was poured off, and the material was desolvated in a 60°C oven for 6 hours. 3-8 mg of the powder was loaded into a crucible, and a device modified from a thermogravimetric analyzer was used to carry out the adsorption rate test (TGA Q500, TA Instruments, USA). Figure 8 ).

[0068] The adsorption rate test results of the samples obtained from Example 1 and Example 2 are the same (see Figures 9-11 ),, Figure 9 , Figure 10 and Figure 11 The adsorption rate curves of ZIF-8 sample for isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane at 298 K, 308 K and 318 K. By comparison, it is found that under dynamic conditions, ZIF-8 reaches equilibrium with 1-pentene, cis / trans-2-pentene and n-pentane within 10 minutes, while isoprene is almost not adsorbed, which indicates that isoprene cannot enter the pores of ZIF-8 under dynamic conditions.

[0069] Liquid phase adsorption experiment

[0070] To demonstrate the utility of ZIF-8, liquid adsorption experiments were performed on the ZIF-8 samples obtained from Example 1 and Example 2. The procedure was as follows: in a 1.5 mL liquid chromatography vial, 25 mg of activated ZIF-8 was added, followed by 1 mL of liquid isoprene, and 4 μL each of 1-pentene, cis-2-pentene, trans-2-pentene, and n-pentane. Using a microsyringe, 3 μL of liquid was sampled every hour for gas chromatography testing. The content of C5 hydrocarbons was determined by analyzing the peak areas at different retention times. The results are shown in FIGS. 1-3. Figure 13 , Figure 13 The concentration changes of various components in the liquid adsorption experiments are shown in FIGS. 1-3. It can be seen that ZIF-8 can be used to adsorb trace impurities in isoprene to obtain high-purity isoprene.

[0071] Example 3 Preparation of ZIF-8 composite without activated carbon

[0072] Step 1: Dissolve zinc acetate dihydrate (0.34 mmol) and 2-methylimidazole (2.72 mmol) in 1.8 L of deionized water, respectively, to form two clear solutions; then quickly pour the zinc acetate dihydrate solution into the 2-methylimidazole solution, quickly stir for 15 minutes, and stand for 24 hours.

[0073] Step 2: To remove solvent molecules in the pores of the material, the crystalline sample obtained above is washed with high-purity methanol and then soaked in methanol solvent. The solvent exchange is repeated 3-6 times. The exchanged crystalline sample is transferred to fresh methanol solvent.

[0074] Step 3: Centrifuge the methanol suspension of the sample in Step 2 at a speed of 5000 rpm for 5 minutes, discard the supernatant, and degas at 80 °C for 12 hours to obtain a dry sample of the material after solvent removal;

[0075] Step 4: Take 1 g of the dry sample obtained in Step 3, add 20 mg of CMC, mix well, then slowly add 1.2 mL of deionized water while stirring to obtain a paste before shaping.

[0076] Step 5: Extrude the paste of Step 4 into a long strip with a diameter of 3 mm, then extrude it into small balls with a diameter of 3 mm (ZIF-8 / CMC2) using an instrument, and dry it in an oven at 80 °C for 3 h.

[0077] Example 4 Preparation of ZIF-8 composite with activated carbon

[0078] First step: Dissolve zinc acetate dihydrate (0.34 mmol) and 2-methylimidazole (2.72 mmol) in 1.8 L deionized water respectively, forming two clear solutions; then pour the zinc acetate dihydrate solution into the 2-methylimidazole solution quickly, stir quickly for 15 minutes, and stand for 24 hours.

[0079] Second step: To remove the solvent molecules in the material pores, the crystalline sample obtained above is washed with high-purity methanol and then immersed in methanol solvent. The solvent exchange is continued for 3-6 times. The exchanged crystalline sample is transferred to fresh methanol solvent.

[0080] Third step: Centrifuge the methanol suspension of the sample in the second step at a speed of 5000 rpm for 5 minutes, discard the supernatant, and degas at 80°C for 12 hours to obtain a desolvated dry sample of the material.

[0081] Fourth step: Take 1 g of the sample obtained in the third step, add 20 mg of CMC and 10 mg of activated carbon, mix uniformly, slowly add 1.2 mL of deionized water, and stir while adding to obtain a paste before shaping.

[0082] Fifth step: Extrude the paste of the fourth step into a 3 mm diameter strip, then extrude it into a 3 mm diameter ball through the instrument (ZIF-8 / CMC2-AC1), and dry it in an 80°C oven for 3 hours.

[0083] Example 5

[0084] First step: Dissolve zinc acetate dihydrate (0.34 mmol) and 2-methylimidazole (2.72 mmol) in 1.8 L deionized water respectively, forming two clear solutions; then pour the zinc acetate dihydrate solution into the 2-methylimidazole solution quickly, stir quickly for 30 minutes, and stand for 24 hours.

[0085] Second step: To remove the solvent molecules in the material pores, the crystalline sample obtained above is washed with high-purity methanol and then immersed in methanol solvent. The solvent exchange is continued for 3-6 times. The exchanged crystalline sample is transferred to fresh methanol solvent.

[0086] Third step: Centrifuge the methanol suspension of the sample in the second step at a speed of 5000 rpm for 5 minutes, discard the supernatant, and dry in a 60°C oven for 6 hours to obtain a desolvated dry sample of the material.

[0087] Fourth step: Take 200 g of the sample obtained in the third step, add 20 g of CMC and 10 g of activated carbon, mix uniformly, slowly add 50 mL of deionized water, and stir while adding to obtain a paste before shaping.

[0088] Fifth step: extrude the paste of the fourth step into a long strip with a diameter of 3 mm, then extrude into small balls with a diameter of 3 mm (ZIF-8 / CMC2-AC1), and dry in an 80 ℃ oven for 3 h.

[0089] Example 6

[0090] The difference between Example 6 and Example 4 is:

[0091] Fourth step: take 100 g of the sample obtained in the third step, add 20 g of CMC and 10 g of activated carbon, mix uniformly, then slowly add 50 mL of deionized water while stirring, to obtain the pre-molding paste.

[0092] The rest of the steps are all the same.

[0093] Example 7

[0094] The difference between Example 7 and Example 4 is:

[0095] Fourth step: take 100 g of the sample obtained in the third step, add 0.5 g of CMC and 30 g of activated carbon, mix uniformly, then slowly add 50 mL of deionized water while stirring, to obtain the pre-molding paste.

[0096] The rest of the steps are all the same.

[0097] The performance test results for C5 hydrocarbons obtained in Examples 5-7 are the same as in Example 4.

[0098] Nitrogen adsorption test

[0099] The extruded ZIF-8 / CMC2 and ZIF-8 / CMC2-AC1 balls prepared in Example 3 and Example 4 were subjected to nitrogen adsorption testing. Before testing, vacuum degassing was performed, and after degassing was complete, nitrogen adsorption at 77 K was tested. The results are shown in Figure 14 , Figure 14 The N2 adsorption isotherm of the extruded ZIF-8 / CMC2 and ZIF-8 / CMC2-AC1 at 77 K. The results show that the N2 adsorption of ZIF-8 / CMC2 and ZIF-8 / CMC2-AC1 did not decrease significantly, indicating that the extruded ZIF-8 / CMC2 and ZIF-8 / CMC2-AC1 still maintained the inherent microporosity characteristics.

[0100] Adsorption rate test

[0101] The pellets of ZIF-8 / CMC2 and ZIF-8 / CMC2-AC1 prepared in Example 3 and Example 4 were taken and the adsorption rate test was performed using a device modified from a thermogravimetric analyzer. The activation step was achieved by heating to 100 °C for 30 min with N2purging on the thermogravimetric analyzer. The results are shown in Figures 15-16 , Figure 15 The adsorption rate curves of ZIF-8 / CMC2 for isoprene and n-pentane at 298 K are shown in Figure 6. It can be seen that the adsorption rate of ZIF-8 / CMC2 is significantly reduced compared with the pure ZIF-8 material, while the adsorption capacity does not decrease significantly, indicating that the mass transfer performance of the ZIF-8 composite after molding has decreased. Figure 16 The adsorption rate curves of ZIF-8 / CMC2-AC1 for isoprene and n-pentane at 298 K are shown in Figure 7. The adsorption rate of ZIF-8 / CMC2-AC1 is almost the same as that of ZIF-8 powder. It is proved that the addition of activated carbon can improve the mass transfer rate.

[0102] Dynamic breakthrough experiment

[0103] The pellets of ZIF-8 / CMC2 and ZIF-8 / CMC2-AC1 prepared in Example 3 and Example 4 were dried in the test tube at 100 °C under vacuum for 12 h. In order to test the actual C5 separation performance of the synthesized material, a dynamic breakthrough experiment was carried out by bubbling a mixture of isoprene / 1-pentene / cis-2-pentene / trans-2-pentene / n-pentane (1 / 1 / 1 / 1 / 1, v / v / v / v / v) at 0 °C. The results are shown in Figure 17 and Figure 18 , Figure 17 and Figure 18 The fixed bed breakthrough plots of ZIF-8 / CMC2 and ZIF-8 / CMC2-AC1 prepared in Example 3 and Example 4, respectively, are shown in Figure 8. From the breakthrough curves, it can be seen that isoprene will immediately pass out of the ZIF-8 / CMC2 and ZIF-8 / CMC2-AC1 breakthrough columns, while the retention times of 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane in the ZIF-8 / CMC2 are significantly reduced compared with the ZIF-8 powder breakthrough column. In the ZIF-8 / CMC2-AC1 breakthrough column, the retention times of 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane are slightly greater than those of the ZIF-8 powder breakthrough column, which is due to the addition of activated carbon which also has a small amount of adsorption of isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane.

[0104] Liquid phase breakthrough experiment

[0105] ZIF-8 / CMC2-AC1 prepared in Example 4 was dried in a vacuum oven at 100 °C for 12 h, then quickly transferred to a liquid breakthrough column, and a mixture of five C5s was passed through the breakthrough column at a flow rate of 10 ml / min using a digital pump. After the liquid flowed out of the upper end of the breakthrough column, a sample was taken every 3 min, and 3 μL of the liquid was measured for the content of each C5 hydrocarbon using a microsyringe. The results are shown in Figure 19 , Figure 19 Figure 2 is a graph of the results of the liquid breakthrough experiment for ZIF-8 / CMC2-AC1 at 298 K. It can be calculated that 750 ml of pure isoprene can be obtained in one liquid breakthrough.

[0106] Practical application test

[0107] The ratio of C5 fraction in industry is isoprene / 1-pentene / cis-2-pentene / trans-2-pentene / n-pentane = 28.71 / 4.20 / 3.09 / 1.70 / 8.76 (w% / w% / w% / w% / w%). Dry N2 was added to the mixed C5s (isoprene / 1-pentene / cis-2-pentene / trans-2-pentene / n-pentane = 28.71 / 4.20 / 3.09 / 1.70 / 8.76 (w% / w% / w% / w% / w%), a total of 30 mL) at a rate of 20 mL / min at room temperature to form a mixed C5 gas. 24.8977 g of ZIF-8 / CMC2-AC1 prepared in Example 4 was taken, and the breakthrough curve of the C5 mixture was measured at 298 K. A gas chromatograph and a flame ionization detector (FID) were used to monitor the outlet gas of the chromatographic column. After the breakthrough experiment, the sample was regenerated at a N2 flow rate of 50 mL·min -1 at room temperature for 6 h. The experimental results are shown in Figure 20 After integration, 2.81 mmol / g of pure isoprene can be obtained in one fixed bed breakthrough experiment.

[0108] In summary, ZIF-8 has the ability to purify isoprene, and ZIF-8 exhibits high performance in the adsorption capacity of 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane, while the adsorption amount of isoprene can be ignored. In addition, ZIF-8 also has excellent recycling performance.

Claims

1. Use of a ZIF-8 material for separating C5 hydrocarbons, characterized in that: The C5 hydrocarbons are one of isoprene, 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane, and the ZIF-8 material can separate isoprene from at least one of 1-pentene, cis-2-pentene, trans-2-pentene and n-pentane.

2. Use of the ZIF-8 material according to claim 1 for the separation of C5 hydrocarbons, characterized in that: The ZIF-8 material realizes purification of isoprene in vapor and liquid phase.

3. Use of the ZIF-8 material according to claim 1 for separating C5 hydrocarbons, characterized in that: The ZIF-8 material can be recycled, and the regeneration method is to heat the ZIF-8 material to 30-120°C under vacuum or inert gas atmosphere for 6-24 hours, and the inert gas is nitrogen or helium.

4. Use of the ZIF-8 material of claim 1 for separating C5 hydrocarbons, characterized by: A preparation method of the ZIF-8 material in a crystal form, comprising the following steps: Dissolve zinc nitrate hexahydrate in methanol to form a transparent solution A; dissolve 2-methylimidazole in methanol to form a transparent solution B; then pour the transparent solution B into the transparent solution A; stir the mixed solution at room temperature for 6-30 hours at a speed of 500-1000 revolutions per minute, and then stand for 1-12 hours; centrifuge and wash with methanol for several times, and then dry at 50-100°C; The molar ratio of the zinc nitrate hexahydrate to the 2-methylimidazole is 1:4; the addition amount of methanol in the transparent solution A is 75 mL of methanol corresponding to 0.01 mmol of Zn(NO3)2·6H2O; and the volume ratio of methanol in the transparent solution A to that in the transparent solution B is 1:

1.

5. Use of the ZIF-8 material of claim 1 for separating C5 hydrocarbons, characterized by: A green large-scale preparation method of the ZIF-8 material, characterized in that comprising the following steps: dissolve zinc acetate dihydrate and 2-methylimidazole in deionized water respectively to form two clear solutions; then quickly pour the zinc acetate dihydrate solution into the 2-methylimidazole solution, quickly stir for 5 minutes, stand for 12 hours; after centrifugation, wash with methanol for three times, then soak in methanol for 48 hours, replace the fresh methanol for 3-6 times during the period, and vacuum dry at 100°C to obtain the ZIF-8 material; The molar ratio of the zinc acetate dihydrate to the 2-methylimidazole is 1:8, and the addition amount of the deionized water in the preparation of the zinc acetate dihydrate is limited to 1 L of deionized water corresponding to 0.11 mol of zinc acetate dihydrate, and the volume ratio of the deionized water of the two clear solutions is 1:

1.

6. A ZIF-8 composite material, characterized by: The composite material comprises the ZIF-8 material according to any one of claims 1-5, further comprising a binder CMC and activated carbon.

7. The ZIF-8 composite of claim 6, wherein: The mass content of the binder CMC in the composite material is 0.5%-30%, the mass content of the activated carbon is 0%-30%, and the rest is the ZIF-8 material.

8. Use of the ZIF-8 composite material according to claim 7 in separating five C5 hydrocarbons.

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