A capturing agent for separating propylene-propane mixed gas, a preparation method thereof, and a method for separating propylene-propane mixed gas

Abstract

The application provides a kind of propylene propane mixed gas separation trapping agent and its preparation method and propylene propane mixed gas separation method.The trapping agent includes solid adsorbent and organic solvent;The solid adsorbent is CALF-20;With the total mass of the trapping agent as 100%, the content of the solid adsorbent is 5wt%-45wt%, and the content of the organic solvent is 55wt%-95wt%.The MOF slurry trapping agent provided by the application has excellent effect on gas separation, with high propylene adsorption capacity, high propylene / propane selectivity, short equilibrium time, fast desorption speed, high regeneration performance and other advantages.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation, specifically relating to a collector for separating propylene and propane mixed gas, its preparation method, and a method for separating propylene and propane mixed gas. Background Technology

[0002] Propylene is one of the three basic raw materials for synthetic materials, and it has a wide range of industrial applications, including the production of various polymers and plastics, acrylic acid and its esters, and blended gasoline, as well as fuels and catalysts. Currently, the main method for obtaining propylene is through the distillation of naphtha or dry gas, but this method produces impurities that need to be removed to produce high-purity polymer-grade propylene. To meet the demand for high-purity propylene, cryogenic distillation is commonly used industrially to separate propylene and propane. Cryogenic distillation is an equilibrium separation process that requires thermal energy to achieve different distribution ratios of propylene and propane molecules between the equilibrium gas and liquid phases, thereby achieving separation. However, due to the similarity in kinetic diameters and physical properties of propane and propylene, as well as their small difference in condensability, the entire separation process requires a large distillation column with 120-180 trays and a high reflux ratio to obtain high-purity propylene. Therefore, this separation method faces the problems of high energy consumption and high cost, making the development of low-energy, high-efficiency propylene / propane separation methods of great significance.

[0003] Adsorption separation based on solid adsorbents has attracted much attention due to its advantages such as easy recycling and low operating costs. In adsorption separation, the selection of adsorbents requires simultaneous consideration of adsorption capacity and adsorption selectivity. To date, a large number of adsorbents have been used for propylene / propane separation, including activated carbon, carbon molecular sieves, and zeolite molecular sieves. However, these materials suffer from poor stability and poor regeneration reproducibility, making it difficult to meet the standards for propylene / propane separation. Traditional porous materials face some challenges in separating propylene / propane mixtures because they cannot tune the pore environment at the molecular scale. However, metal-organic frameworks (MOFs) offer new opportunities for the separation of propylene / propane mixtures due to their numerous active sites, large active surface area, high porosity, and controllable pore shape.

[0004] MOFs are a class of crystalline materials with periodic network topologies that can be self-assembled through organic ligands and inorganic centers. Studies have found that MOFs are more efficient than traditional porous adsorbents, and some MOFs can even simultaneously possess high adsorption capacity and high selectivity within an adsorbent. However, MOF materials themselves are finely powdered solids that are easily dispersed upon contact with gases, thus they cannot be directly used for gas capture.

[0005] Therefore, how to make MOF materials better suited for gas capture in order to achieve higher and faster separation selectivity is an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a trapping agent for separating propylene-propane mixed gases, its preparation method, and a method for separating propylene-propane mixed gases. The trapping agent is prepared by dispersing CALF-20 in an organic solvent to form a porous slurry, exhibiting higher separation selectivity and capable of separating propylene-propane mixed gases.

[0007] To achieve the above objectives, the present invention provides a trapping agent for separating propylene and propane mixed gases, wherein the trapping agent comprises a solid adsorbent and an organic solvent; the solid adsorbent is CALF-20; the content of the solid adsorbent is 5wt%-45wt% based on the total mass of the trapping agent as 100%; and the content of the organic solvent is 55wt%-95wt%.

[0008] In some specific embodiments, preferably, the content of the solid adsorbent is 20wt%-40wt% based on the total mass of the trapping agent as 100%, specifically it can be 5%, 20%, 30%, 35%, 40%, 45%, etc.

[0009] In some specific embodiments, preferably, the content of the organic solvent is 60wt%-80wt% based on the total mass of the trapping agent as 100%, specifically it can be 55%, 65%, 75%, 80%, 90%, 95%, etc.

[0010] In some specific embodiments, preferably, the trapping agent does not contain water.

[0011] In some specific embodiments, preferably, the trapping agent consists of a solid adsorbent and an organic solvent.

[0012] The inventors of this invention discovered that the metal-organic framework material CALF-20 is hydrophilic. When combined with water, water occupies the pores of CALF-20, reducing its adsorption effect. Therefore, this invention uses an organic solvent to compound CALF-20 to obtain a MOF slurry. In this invention, the organic solvent and CALF-20 can produce a synergistic effect, significantly increasing the absorption rate of propylene by the trapping agent. Compared with MOF slurries containing other metal-organic framework materials, the trapping agent containing CALF-20 in this invention exhibits a faster adsorption rate and higher selectivity for propylene within approximately the same adsorption time.

[0013] According to a specific embodiment of the present invention, preferably, the organic solvent includes one or a combination of two or more of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolinone (DMI), N,N-dimethylpropenylurea (DMPU), isoamyl alcohol, sulfolane, o-xylene, and ethylene glycol.

[0014] The present invention also provides a method for preparing the above-mentioned trapping agent for separating propylene and propane mixed gas, wherein the preparation method includes: mixing a solid adsorbent and an organic solvent, stirring evenly until a stable MOF slurry is formed, thereby obtaining the trapping agent for separating propylene and propane mixed gas.

[0015] The present invention also provides a method for separating a propylene-propane mixture, wherein the method utilizes the aforementioned propylene-propane mixture separation trap to separate propylene and propane from the propylene-propane mixture.

[0016] According to a specific embodiment of the present invention, preferably, the volume ratio (initial gas-liquid ratio) of the propylene-propane mixture to the trapping agent is (5-50):1. The volume of the propylene-propane mixture refers to its volume under standard conditions.

[0017] According to a specific embodiment of the present invention, preferably, in the propylene-propane mixture, the propylene content is 5 mol%-80 mol%, based on the total molar amount of propylene and propane being 100%.

[0018] According to a specific embodiment of the present invention, preferably, the adsorption temperature for propylene-propane separation is 273.15K-313.15K.

[0019] According to a specific embodiment of the present invention, preferably, the adsorption time for propylene-propane separation is 5-50 min.

[0020] According to a specific embodiment of the present invention, preferably, the separation method further includes: desorbing the adsorbed gas trap under vacuum heating conditions, and then recycling it.

[0021] According to a specific embodiment of the present invention, preferably, the heating temperature is 323.15K-343.15K.

[0022] According to a specific embodiment of the present invention, preferably, the vacuuming pressure is below 2 kPa.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) The MOF slurry collector provided by the present invention has excellent gas separation effect, with advantages such as high propylene adsorption capacity, high propylene / propane selectivity, short equilibrium time, fast desorption speed and high regeneration performance. At the same time, it can realize continuous operation and thermal integration, providing diversified options for slurry separation of propane and propylene in industrial applications.

[0025] (2) After the gas-absorbing agent provided by the present invention is saturated, the gas can be desorbed by heating and vacuuming to achieve slurry regeneration and reuse. The regeneration temperature of this agent is mild, the regeneration time is short, the energy consumption is low, the slurry reuse performance is excellent, and the regeneration performance is good. Attached Figure Description

[0026] Figure 1 The adsorption kinetics curves of the MOF slurry collector prepared in Example 1 of the present invention when adsorbing pure propylene and pure propane are shown.

[0027] Figure 2 This is an adsorption kinetic curve of the solid trapping agent in Comparative Example 1 of the present invention when adsorbing pure propylene and pure propane.

[0028] Figure 3 This is a graph showing the changes in the separation effect of the propylene / propane mixture at different adsorption times, as measured in Test Example 2 of this invention. Detailed Implementation

[0029] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0030] The small-scale experimental apparatus of this invention is the apparatus described in paragraphs 23 and 24 of the specification of CN102389686A (ZL201110284360.5), and is used for thermodynamic and kinetic experiments of pure gas and gas mixture.

[0031] The gas composition in the adsorbed phase is obtained based on the material balance of the components during the adsorption process. The data processing and calculation process for the relevant gas solubility experiments and separation experiments is as follows:

[0032] In the following calculations, z1 refers to the mole fraction of C3H6 in the feed gas before separation; y1 refers to the mole fraction of C3H6 in the mixed gas phase at the adsorption time; x1 refers to the mole fraction of C3H6 adsorbed by the adsorbent; similarly, z2, y2, and x2 refer to the mole fractions of C3H8 in the feed gas before separation, in the mixed gas phase at the adsorption time, and adsorbed by the adsorbent, respectively. T refers to the system temperature; P E P1 refers to the equilibrium pressure inside the sapphire reactor; P2 and P1 refer to the initial pressure and the pressure after gas inlet, respectively; R is the gas constant.

[0033] Initial intake molar number n of sapphire reactor t Calculated by the following formula:

[0034]

[0035] In the formula, V t The total effective volume of the balance vessel and connecting pipelines; the compressibility factors Z1 and Z2 corresponding to the initial pressure of the balance vessel and the pressure after air intake are calculated by the BWRS equation of state (Benedict-Webb-Rubin-Starling).

[0036] The amount of total gaseous substance n in the sapphire reactor at equilibrium E Calculated by the following formula:

[0037]

[0038] In the formula, V g Z represents the volume of the gas phase inside the sapphire reactor after adsorption equilibrium. E It is the compressibility factor corresponding to the temperature and pressure inside the sapphire reactor.

[0039] t refers to the adsorption time for propylene-propane separation; n is the total amount of gaseous matter in the sapphire reactor when the specified adsorption time t is reached. t1 Calculated by the following formula:

[0040]

[0041] In the formula, p t1 Z represents the pressure inside the sapphire reactor when the specified adsorption time t is reached. t1 It is the compressibility factor of the sapphire reactor at this temperature and pressure; V g n is the volume of the gas phase inside the sapphire reactor. t1 The total amount of gaseous matter in the sapphire reactor at the specified adsorption time t.

[0042] The total molar amounts of C3H6(n1) and C3H8(n2) gases adsorbed by the adsorbent are calculated using the following formula:

[0043] n1 = n t ×z1-n t1 ×y1;n2=n t ×z2-n t1 ×y2;

[0044] The molar fractions of C3H6 (x1) and C3H8 (x2) adsorbed by the adsorbent are calculated using the following formulas:

[0045]

[0046] Sv This refers to solubility; the solubility S of C3H6 v Defined as:

[0047] V S =h×π×r 2 ;

[0048] In the formula, V S The volume of the adsorbent is calculated from its height h in the sapphire reactor; r is the inner diameter of the sapphire reactor; and h is the height of the adsorbent in the sapphire reactor.

[0049] Φ refers to the initial gas-liquid ratio, which is calculated using the following formula;

[0050]

[0051] β refers to the separation factor of C3H6 relative to C3H8, calculated using the following formula:

[0052]

[0053] All gas composition analyses were performed using an HP7890B chromatograph.

[0054] The synthesis process of the solid adsorbent CALF-20 used in the embodiments and comparative examples of the present invention is as follows:

[0055] A mixed solution was prepared by mixing water and methanol in a mass ratio of 1:4. Then, basic zinc carbonate, anhydrous oxalic acid, and 1,2,4-triazole were dissolved in the mixed solution in a mass ratio of 12:7:60. The mixture was then reacted in a high-pressure hydrothermal reactor at 453 K for 48 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting white precipitate was washed with water and methanol and dried in air to obtain the solid adsorbent CALF-20.

[0056] Example 1

[0057] This embodiment provides a trapping agent for separating propylene and propane mixed gases. The preparation method of the trapping agent is as follows:

[0058] CALF-20 and DMI are mixed and stirred until a stable MOF slurry is formed. The content of CALF-20 is 40 wt% based on the total mass of the trapping agent as 100%. The trapping agent for propylene-propane mixed gas separation is denoted as CALF-20(40wt%) / DMI slurry.

[0059] Example 2

[0060] This embodiment provides a trapping agent for separating propylene and propane mixed gases. The difference between this trapping agent and that of Example 1 is that the organic solvent is replaced with NMP, while other parameters are the same as in Example 1, resulting in a trapping agent for separating propylene and propane mixed gases, denoted as CALF-20 (40wt%) / NMP slurry.

[0061] Comparative Example 1

[0062] This comparative example provides a trapping agent for separating a propylene-propane mixed gas. The difference between this trapping agent and Example 1 is that it uses solid CALF-20 as the trapping agent without adding organic solvents to form an MOF slurry.

[0063] The following tests were conducted on the propylene-propane separation performance of the trapping agents in Example 1 and Comparative Example 1, as detailed below:

[0064] Test Example 1

[0065] This test example uses the small-scale experimental apparatus of the present invention, taking the trapping agents in Example 1 and Comparative Example 1 as test objects, to determine the kinetic curves of pure propylene and pure propane. The specific process and results are as follows:

[0066] At an adsorption temperature of 293.15 K and an inlet pressure of 150 kPa, the kinetic curves of the trapping agent in Example 1 for pure propylene and pure propane are as follows: Figure 1 As shown. From Figure 1 As can be seen, there are significant differences in both the adsorption capacity and adsorption rate between the two gases. When the adsorption time is 10 min, propylene reaches 87.6% of the maximum pressure drop, while propane only reaches 58.2%. When the adsorption time is 15 min, the CALF-20 (40 wt%) / DMI slurry reaches equilibrium for propylene, while propane requires more than 25 min to reach equilibrium. These results demonstrate that the collector in Example 1 exhibits significant thermodynamic and kinetic differences in the adsorption of pure propylene and pure propane, providing feasibility for separating propylene / propane mixtures using this collector.

[0067] Furthermore, at an adsorption temperature of 293.15 K and an inlet pressure of 150 kPa, the kinetic curves of pure propylene and pure propane were determined using the trapping agent (solid CALF-20) from Comparative Example 1 as the test object. The results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the adsorption behaviors of propylene and propane on solid CALF-20 are different.

[0068] Will Figure 1 and Figure 2A comparison reveals that in Comparative Example 1, using solid CALF-20 alone as the trapping agent resulted in insufficient adsorption of propylene gas, failing to efficiently separate the propylene / propane mixture. In contrast, in Example 1, a stable MOF slurry was prepared by mixing solid CALF-20 with an organic solvent. Since solvent molecules could not penetrate the suspended particles, a semi-permeable membrane was formed on the particle surface. This membrane exhibited excellent selectivity for gas molecules bound to liquid molecules. This selectivity resulted in propylene passing through the membrane in a shorter time compared to propane, thus highlighting the difference in adsorption rates between propylene and propane when using the CALF-20 / DMI slurry. Furthermore, the solubility of propane in the CALF-20 / DMI slurry was much lower than that of propylene. Therefore, the trapping agent prepared in Example 1 could perform kinetic separation of the propylene / propane mixture, making the propylene / propane separation process more efficient.

[0069] Test Example 2

[0070] This test example uses the small-scale experimental apparatus of the present invention, with the trapping agent prepared in Example 2 as the test object, to determine the effect of different adsorption times on the propylene / propane separation effect. The specific process and results are as follows:

[0071] In kinetic separation experiments, adsorption time is also an important factor to consider. In this test example, the adsorption temperature was 293.15 K, the initial gas-liquid ratio was approximately 36, and the concentrations of propylene / propane in the feed gas before separation were 51.4 mol% / 48.6 mol%. The separation effect of the CALF-20 (40 wt%) / NMP slurry trap provided in Example 2 on the propylene / propane mixture at different adsorption times is as follows: Figure 3 As shown, the specific results are recorded in Table 1. From Figure 3 As shown in Table 1, the concentration of propylene in the gas phase (y1) first decreases and then increases, while the separation factor β first increases and then decreases. Comparative experimental results indicate that the 20-30 min time range is the optimal time for kinetic separation of propylene / propane, within which the separation factor reaches above 14. When the adsorption time is 27 min, the separation factor is 15.3, and the propylene concentration in the gas phase decreases to 21.41 mol%, thus proving that the trapping agent prepared in Example 2 can achieve efficient separation of the propylene / propane mixture.

[0072] Table 1. Experimental results of separating C3H6 / C3H8 mixtures at different adsorption times at 293.15 K.

[0073] 2 35.68 2.56 0.26 47.78 69.60 2.5 3 37.26 2.19 0.47 42.51 73.96 3.9 5 38.09 2.02 0.60 38.12 70.54 5.0 8 36.63 1.90 0.60 36.93 75.82 5.5 11 37.10 1.79 0.69 34.87 77.61 6.5 14 36.01 1.73 0.76 30.55 77.12 7.6 17 37.36 1.67 0.76 26.42 81.03 11.8 22 35.06 1.61 0.74 23.97 81.64 14.1 27 34.72 1.50 0.79 21.41 80.62 15.3 30 37.66 1.44 0.91 19.74 78.52 14.9 40 37.00 1.40 0.90 21.86 76.21 11.4 50 35.30 1.35 0.85 27.21 74.72 7.9

[0074] Test Example 3

[0075] This test example uses the small-scale experimental apparatus of the present invention, with the trapping agent prepared in Example 2 as the test object, to conduct separation experiments on propylene / propane mixtures with different feed gas ratios. The specific process and results are as follows:

[0076] In practical industrial applications, multi-stage separation is often required to achieve efficient separation of propylene / propane, thus necessitating further separation operations for propylene / propane mixtures with different compositions. In this test example, the adsorption temperature was 293.15 K, the initial gas-liquid ratio was approximately 36, and the adsorption time was 27 min. Table 2 shows the separation results of the CALF-20 (40 wt%) / NMP slurry collector provided in Example 2 for propylene / propane mixtures under different feed gas ratios. As can be seen from Table 2, even after changing the molar fraction (z1) of C3H6 in the feed gas before separation, the CALF-20 / NMP slurry still exhibits good separation performance for propylene / propane mixtures with different feed gas ratios, with separation factors all above 12.7. Furthermore, the separation effect is even better for feed gases with lower initial propylene concentrations (below 8 mol%), where the molecular factor can reach 16.7.

[0077] Table 2. Experimental results of separating C3H6(1) / C3H8(2) mixtures with different feed gas ratios at 293.15 K.

[0078] 51.42 37.66 1.44 0.91 19.72 78.45 14.9 38.21 34.73 1.86 0.55 16.54 75.78 15.8 19.44 35.13 1.98 0.49 6.98 48.41 12.7 16.32 35.59 2.08 0.47 5.53 42.71 12.8 7.22 37.25 2.30 0.40 1.72 22.62 16.7 5.78 36.74 2.39 0.35 1.54 19.99 16.5

[0079] Test Example 4

[0080] This test example uses the small-scale experimental apparatus of the present invention to test the regeneration performance of the trapping agent prepared in Example 2. The specific process and results are as follows:

[0081] In practical applications, the regeneration performance of the trap is one of the key factors in evaluating its performance. Therefore, to further verify whether the trap of the present invention has good regeneration performance, the CALF-20 (40wt%) / NMP slurry trap provided in Example 2 was subjected to multiple absorption-desorption cycles. Separation and regeneration experiments were conducted to examine the separation and regeneration performance of the trap. The adsorption temperature was 293.15 K, the initial gas-liquid ratio was approximately 37, the adsorption time was 27 min, and the concentrations of propylene / propane in the raw gas before separation were 51.4 mol% / 48.6 mol%. The regeneration conditions were vacuum desorption at 343.15 K for 30 min. This treatment method aims to remove gas molecules adsorbed in the slurry to the greatest extent possible so that its adsorption capacity can be restored in the next experiment. The regeneration performance results of the trap provided in Example 2 are shown in Table 3. "Repeated 0 times" refers to using fresh liquid trap to absorb the mixed gas; "repeated 1 time" refers to using fresh liquid for absorption and desorption once, followed by repeated absorption, and so on. As can be seen from Table 3, the separation factor remained above 14 as the number of experiments gradually increased, indicating that the trapping agent maintained a very high level of separation selectivity even after multiple uses.

[0082] Table 3. Repeated experimental results of C3H6 / C3H8 mixture separation by CALF-20 / NMP slurry at 293.15 K.

[0083] 0 36.31 1.46 0.80 20.13 78.04 14.1 1 37.66 1.44 0.91 19.72 78.51 14.9 2 35.24 1.47 0.83 20.38 79.44 15.0 3 37.10 1.41 0.89 19.81 78.35 14.6 4 38.80 1.46 0.95 19.32 78.01 14.8 5 36.55 1.40 0.87 19.67 78.23 15.2

[0084] Test Example 5

[0085] To investigate the effect of different organic solvents used to prepare MOF slurries on the separation effect of propylene / propane mixed gases, this test example used the small-scale experimental apparatus of the present invention. The mass content of the solid adsorbent CALF-20 was kept constant at 40 wt%. Different organic solvents were mixed with CALF-20 to prepare MOF slurry collectors, and propylene / propane mixed gas separation experiments were conducted. The adsorption time was 33 min, and the concentrations of propylene / propane in the feed gas before separation were 51.4 mol% / 48.6 mol%. The test results are shown in Table 4. Table 4 shows that the MOF slurry collectors prepared using organic solvents such as NMP, DMI, dimethyl sulfoxide, and sulfolane all exhibited good separation effects on propylene / propane mixed gases.

[0086] Table 4. Effect of organic solvents on the separation efficiency of C3H6 / C3H8 mixed gas

[0087] NMP 35.94 293.15 1.76 0.75 31.62 7.1 DMI 31.51 293.15 1.49 0.71 29.51 7.0 Dimethyl sulfoxide 35.90 293.15 1.62 0.73 35.54 5.0 Sulfolane 31.74 303.15 1.88 0.51 36.47 8.2

[0088] The test examples 1-5 above demonstrate that the liquid trap provided by this invention has a good separation effect on propylene / propane mixed gas, with high propylene adsorption capacity, high separation selectivity, and good regeneration performance.

Claims

1. A collector for separating a propylene-propane mixture, wherein, The trapping agent comprises a solid adsorbent and an organic solvent, and the trapping agent does not contain water; The solid adsorbent is CALF-20; Based on the total mass of the collecting agent as 100%, the content of the solid adsorbent is 20wt%-40wt%, and the content of the organic solvent is 60wt%-80wt%. The organic solvent is any one of N-methylpyrrolidone, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolinone, and sulfolane.

2. The method for preparing the precipitant for separating propylene and propane mixed gases according to claim 1, wherein, The preparation method includes: mixing a solid adsorbent and an organic solvent, stirring until a stable MOF slurry is formed, and obtaining a collector for separating propylene and propane mixed gas.

3. A method for separating a propylene-propane mixture, wherein, This method uses the propylene-propane mixture separation trapping agent described in claim 1 to separate propylene and propane from the propylene-propane mixture.

4. The separation method according to claim 3, wherein, The volume ratio of the propylene-propane mixture to the trapping agent is (5-50):

1.

5. The separation method according to claim 3, wherein, In the propylene-propane mixture, the propylene content is 5 mol%-80 mol, with the total molar amount of propylene and propane being 100%.

6. The separation method according to claim 3, wherein, The adsorption temperature for the separation of propylene and propane is 273.15 K-313.15 K.

7. The separation method according to claim 3, wherein, The adsorption time for the separation of propylene and propane is 5-50 min.

8. The separation method according to claim 3, wherein, The separation method further includes the step of desorbing the adsorbed gas trap under vacuum heating conditions, and then recycling it.

9. The separation method according to claim 8, wherein, The heating temperature is 323.15 K-343.15 K.

10. The separation method according to claim 8, wherein, The vacuum pressure is below 2 kPa.

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