A zeolite for gas separation and its application

Abstract

The present application relates to the technical field of zeolite modification and gas separation, and specifically discloses a zeolite for gas separation and its application. The present application adopts zeolite composition with different specific particle size distributions, and has excellent gas separation performance. The zeolite has a short gas diffusion path and a hierarchical pore structure, so that the adsorption sites are fully exposed and the gas mass transfer diffusion resistance is reduced; when the zeolite is applied to gas separation, especially nitrogen / methane separation, carbon dioxide / methane separation and nitrogen / methane / carbon dioxide separation, the separation effect is significantly improved, which is of great significance to the utilization and recovery of methane.

Description

Technical Field

[0001] The present application relates to the technical field of zeolite modification and gas separation, and in particular to a zeolite for gas separation and its application. Background Art

[0002] Methane is the second largest greenhouse gas caused by human activities. Its greenhouse effect is 28 times that of carbon dioxide (100 years). At the same time, methane is also an efficient clean fuel and an important chemical raw material. Therefore, research on the recovery and utilization of methane has significant economic and environmental effects.

[0003] The adsorption separation method using zeolite as adsorbent to separate methane and other gases has the characteristics of low energy consumption and flexible operation, and has broad development prospects. However, synthetic zeolites and natural zeolites are usually large in size and have a single particle size distribution, which has the problem of limited gas mass transfer rate, resulting in insufficient zeolite utilization and poor gas separation effect. Although the particle size distribution can be adjusted or the hierarchical pore structure can be introduced by adding templates, surfactants or acid / base post-treatment to improve the gas dynamic diffusion performance of zeolites, its high cost and complex process limit its large-scale application.

[0004] Currently, amplifying the differences in the kinetic diffusion rates of gases in zeolites to achieve efficient gas separation has become a research focus in the field of zeolite modification and gas separation. Summary of the invention

[0005] The purpose of the present application is to overcome the deficiencies of the above-mentioned prior art and provide a zeolite for gas separation and its application. The zeolite of the present application has excellent gas separation performance and can achieve efficient separation of mixed gases.

[0006] To achieve the above purpose, the technical solution adopted by this application is:

[0007] The present application provides a zeolite for gas separation, the zeolite comprising a first zeolite, a second zeolite and a third zeolite having different particle size distributions;

[0008] The average particle size of the first zeolite is A, A ≤ 200 nm;

[0009] The average particle size of the second zeolite is B, 200 nm

[0010] The average particle size of the third zeolite is C, 600nm <C≤5μm。

[0011] ​After extensive research and experiments, the inventors of the present application discovered that by compounding the first zeolite, the second zeolite and the third zeolite within the above-mentioned specific average particle size range, the compounded zeolite of the present application is obtained. The zeolite has excellent gas separation performance and can achieve efficient separation of mixed gases based on gas diffusion kinetics.

[0012] When the first zeolite, the second zeolite and the third zeolite do not adopt the above average particle size range, the difference in the kinetic diffusion rate of the zeolite is small, and the screening of methane and other gases cannot be achieved, or the separation performance is poor.

[0013] The zeolite with excellent gas separation performance in the present application has a short gas diffusion path and a hierarchical pore structure, so that the adsorption sites are fully exposed and the gas mass transfer diffusion resistance is reduced; when the zeolite is applied to gas separation, the separation effect is significantly improved, which is of great significance to methane utilization and recovery.

[0014] As a preferred embodiment of the zeolite for gas separation described in the present application, the types of the first zeolite, the second zeolite and the third zeolite include at least one of clinoptilolite, mordenite, 4A zeolite, ZSM-5 zeolite and PHI zeolite. Clinoptilolite and mordenite are usually natural zeolites and synthetic zeolites, and 4A zeolite, ZSM-5 zeolite and PHI zeolite are usually synthetic zeolites.

[0015] As a preferred embodiment of the zeolite for gas separation described in the present application, the mass ratio of the first zeolite, the second zeolite and the third zeolite is (5-8):(1-4):1.

[0016] When the first zeolite, the second zeolite, and the third zeolite of the present application adopt the above mass ratio, the compounded zeolite has a more excellent gas separation performance, and the effect of separating gas is significant, which is of great significance to the utilization and recovery of methane. If the mass of the first zeolite is lower than this interval, it is difficult to screen or efficiently screen the methane and the separated gas; if the mass of the first zeolite is higher than this interval, it will cause a great pressure drop in the adsorption tower.

[0017] As a preferred embodiment of the zeolite for gas separation described in the present application, the pore volume of the first zeolite is 0.1-0.2 cm 3 / g.

[0018] As a preferred embodiment of the zeolite for gas separation described in the present application, the pore volume of the second zeolite is 0.05~0.1cm 3 / g.

[0019] As a preferred embodiment of the zeolite for gas separation described in the present application, the pore volume of the third zeolite is 0.01-0.05 cm 3 / g.

[0020] When the first zeolite, the second zeolite and the third zeolite of the present application adopt the above-mentioned pore volume range, the zeolite has a hierarchical pore structure and a shorter gas diffusion path, so that the adsorption sites are fully exposed and the gas mass transfer diffusion resistance is reduced to better separate the gas; the zeolite whose pore volume is not within this range will have problems such as diffusion limitation, low adsorption capacity or poor nitrogen / methane selectivity, and cannot separate the gas.

[0021] As a preferred embodiment of the zeolite for gas separation described in the present application, a first zeolite, a second zeolite and a third zeolite with different particle size distributions are prepared by ball milling a zeolite with a particle size greater than 20 μm;

[0022] The mass ratio of the zeolite to the ball milling beads is 1:(3-30);

[0023] The ball mill beads include small beads with a particle size of 1 mm, medium beads with a particle size of 5 mm and large beads with a particle size of 10 mm; the weight ratio of the small beads, medium beads and large beads is (5-7): (2-3): (1-2).

[0024] The small beads, medium beads and large beads of the present application adopt the above weight ratio, and can be ball-milled to obtain the first zeolite, the second zeolite and the third zeolite with the above specific particle size distribution to obtain more excellent gas separation performance.

[0025] In some specific embodiments, the ball milling is dry milling or wet milling;

[0026] Preferably, the ball milling is wet milling, the solvent used includes at least one of ethanol, methanol and water, and the mixing ratio of zeolite to solvent is 25-100 g / L.

[0027] The present application also provides application of the above zeolite in gas separation.

[0028] The present application also provides a gas separation method, which comprises using the zeolite to separate gases, wherein the gases comprise at least one of methane and a separation gas having the same kinetic diameter and characteristics as methane.

[0029] As a preferred embodiment of the gas separation method described in the present application, the separated gas includes carbon dioxide and nitrogen;

[0030] For nitrogen / methane separation and carbon dioxide / methane separation, the volume ratio of methane and separation gas is 1:1, and the total flow rate of methane flow rate and separation gas flow rate is 2~20 sccm (standard cubic centimeters per minute); if it is nitrogen / methane / carbon dioxide separation, the volume ratio of nitrogen / methane / carbon dioxide is 5:30:65, and the total flow rate is 5~10 sccm; the purge gas is one of argon and helium, and the flow rate is 5~30 sccm.

[0031] When the zeolite with excellent gas separation performance of the present application is used in gas separation, especially nitrogen / methane separation, carbon dioxide / methane separation and nitrogen / methane / carbon dioxide separation, the separation effect is significantly improved, which is of great significance to methane utilization and recovery.

[0032] Compared with the prior art, this application has the following beneficial effects:

[0033] The present application provides a zeolite for gas separation and its application. The present application adopts zeolites with different specific particle size distributions to form the zeolite with excellent gas separation performance of the present application. The zeolite has a short gas diffusion path and a hierarchical pore structure, so that the adsorption sites are fully exposed and the gas mass transfer diffusion resistance is reduced. When the zeolite is applied to gas separation, especially nitrogen / methane separation, carbon dioxide / methane separation and nitrogen / methane / carbon dioxide separation, the separation effect is significantly improved, which is of great significance to the utilization and recovery of methane. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a scanning electron microscope image (SEM) of the zeolite of Example 1;

[0035] Figure 2 This is a graph showing the separation performance of the zeolite of Example 1 in a nitrogen / methane mixed gas;

[0036] Figure 3 This is a graph showing the separation performance of the zeolite of Example 1 in a nitrogen / methane / carbon dioxide mixed gas. DETAILED DESCRIPTION

[0037] In order to better illustrate the purpose, technical solutions and advantages of the present application, the present application will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0038] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0039] Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention.

[0040] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0041] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0042] In the following examples and comparative examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified, and the components and raw materials used in each parallel experiment are of the same type.

[0043] In the following examples and comparative examples:

[0044] Synthesis of mordenite: The raw materials tetraethyl silicate: aluminum sulfate: sodium hydroxide: water were mixed in a mass ratio of 14:1.4:1:20, magnetically stirred for 24 h, transferred into a polytetrafluoroethylene reactor, reacted at 180°C for 6 days, and washed and dried after the reaction to obtain mordenite.

[0045] Example 1

[0046] This embodiment provides a zeolite for gas separation:

[0047] 1. Add mordenite and ball milling beads into a ball mill. The weight ratio of small beads (1 mm): medium beads (5 mm): large beads (10 mm) is 6:3:1. The mass ratio of mordenite to ball milling beads is 1:20. The ball milling time is 4 hours and the ball mill speed is 600 rpm.

[0048] 2. Recover the ball-milled sample, collect the first zeolite, the second zeolite and the third zeolite to form the zeolite for gas separation in the embodiment of the present application, the particle size of the first zeolite is A, 80 nm ≤A ≤ 150 nm; the particle size of the second zeolite is B, 400 nm ≤B ≤ 520 nm; the particle size of the third zeolite is C, 1 μm ≤C ≤2 μm, the mass ratio of the first zeolite, the second zeolite and the third zeolite is 6:3:1, and the pore volume of the first zeolite is 0.2 cm 3 / g, the pore volume of the second zeolite is 0.1cm 3 / g, and the pore volume of the third zeolite is 0.05cm 3 / g.

[0049] The scanning electron microscope (SEM) image of the zeolite for gas separation obtained in Example 1 above is as follows: Figure 1 shown.

[0050] Example 2

[0051] This embodiment provides a zeolite for gas separation:

[0052] 1. Add mordenite and ball milling beads into a ball mill. The weight ratio of small beads (1 mm): medium beads (5 mm): large beads (10 mm) is 5:3:2. The mass ratio of mordenite to ball milling beads is 1:20. The ball milling time is 5 h and the ball mill speed is 600 rpm.

[0053] 2. Recover the ball-milled sample, collect the first zeolite, the second zeolite and the third zeolite to form the zeolite for gas separation in the embodiment of the present application, the particle size of the first zeolite is A, 120 nm ≤A ≤ 180 nm; the particle size of the second zeolite is B, 450 nm ≤B ≤ 500 nm; the particle size of the third zeolite is C, 1.2 μm ≤C ≤1.8 μm, the mass ratio of the first zeolite, the second zeolite and the third zeolite is 5:4:1, and the pore volume of the first zeolite is 0.14 cm 3 / g, and the pore volume of the second zeolite is 0.07 cm 3 / g, and the pore volume of the third zeolite is 0.03 cm 3 / g.

[0054] Example 3

[0055] 1. Add mordenite and ball milling beads into a ball mill. The weight ratio of small beads (1 mm): medium beads (5 mm): large beads (10 mm) is 7:2:1. The mass ratio of mordenite to ball milling beads is 1:20. The ball milling time is 4 hours and the ball mill speed is 600 rpm.

[0056] 2. Recover the ball-milled sample, collect the first zeolite, the second zeolite and the third zeolite to form the zeolite for gas separation of the embodiment of the present application, the particle size of the first zeolite is A, 80 nm ≤ A ≤ 120 nm; the particle size of the second zeolite is B, 380 nm ≤ B ≤ 450 nm; the particle size of the third zeolite is C, 600 nm ≤ C ≤ 1.5 μm, the mass ratio of the first zeolite, the second zeolite and the third zeolite is 7:2:1, and the pore volume of the first zeolite is 0.18 cm 3 / g, and the pore volume of the second zeolite is 0.09 cm 3 / g, and the pore volume of the third zeolite is 0.04 cm 3 / g.

[0057] Example 4

[0058] 1. Add mordenite and ball milling beads into a ball mill. The weight ratio of small beads (1 mm): medium beads (5 mm): large beads (10 mm) is 6:3:1. The mass ratio of mordenite and ball milling beads is 1:5. The ball milling time is 4 hours and the ball mill speed is 600 rpm.

[0059] 2. Recover the ball-milled sample, collect the first zeolite, the second zeolite and the third zeolite to form the zeolite for gas separation in the embodiment of the present application, the particle size of the first zeolite is A, 150nm ≤A ≤200 nm; the particle size of the second zeolite is B, 480nm ≤B ≤600 nm; the particle size of the third zeolite is C, 3μm ≤C ≤5μm, the mass ratio of the first zeolite, the second zeolite and the third zeolite is 5:4:1, and the pore volume of the first zeolite is 0.13cm 3 / g, and the pore volume of the second zeolite is 0.06cm 3 / g, and the pore volume of the third zeolite is 0.03 cm 3 / g. .

[0060] Example 5

[0061] 1. Add mordenite and ball milling beads into a ball mill. The weight ratio of small beads (1 mm): medium beads (5 mm): large beads (10 mm) is 6:3:1. The mass ratio of mordenite and ball milling beads is 1:5. The ball milling time is 4 hours and the ball mill speed is 600 rpm.

[0062] 2. Recover the ball-milled sample, collect the first zeolite, the second zeolite and the third zeolite to form the zeolite for gas separation of the embodiment of the present application, the particle size of the first zeolite is A, 80nm ≤A ≤120 nm; the particle size of the second zeolite is B, 350nm ≤B ≤500 nm; the particle size of the third zeolite is C, 800nm ​​≤C ≤1.5μm, the mass ratio of the first zeolite, the second zeolite and the third zeolite is 6:3:1, and the pore volume of the first zeolite is 0.17cm 3 / g, and the pore volume of the second zeolite is 0.09 cm 3 / g, and the pore volume of the third zeolite is 0.01cm 3 / g.

[0063] Example 6

[0064] 1. Add mordenite and ball milling beads into a ball mill. The weight ratio of small beads (1 mm): medium beads (5 mm): large beads (10 mm) is 6:3:1. The mass ratio of mordenite to ball milling beads is 1:30. The ball milling time is 4 hours and the ball mill speed is 600 rpm.

[0065] 2. Recover the ball-milled sample, collect the first zeolite, the second zeolite and the third zeolite to form the zeolite for gas separation of the embodiment of the present application, the particle size of the first zeolite is A, 80nm ≤A ≤150 nm; the particle size of the second zeolite is B, 300nm ≤B ≤400 nm; the particle size of the third zeolite is C, 700nm ≤C ≤1.4μm, the mass ratio of the first zeolite, the second zeolite and the third zeolite is 8:1:1, and the pore volume of the first zeolite is 0.1cm 3 / g, and the pore volume of the second zeolite is 0.05cm 3 / g, and the pore volume of the third zeolite is 0.01cm 3 / g.

[0066] Comparative Examples 1 to 8

[0067] Compared with Example 1, the difference between Comparative Examples 1 to 8 is that Table 1 is different;

[0068] Table 1

[0069]

[0070] Compared with Example 1, the difference is that the ball milling speed used in Comparative Example 1 is 200 rpm, and the other parameters are the same as those in Example 1.

[0071] Compared with Example 1, the difference is that the ball milling time used in Comparative Example 2 is 3 hours, and the other parameters are the same as those in Example 1.

[0072] Compared with Example 1, the difference is that the mass ratio of ball milling beads to zeolite used in Comparative Example 3 is 35:1, and the other parameters are the same as those in Example 1.

[0073] Compared with Example 1, the difference is that the weight ratio of small beads (1 mm): medium beads (5 mm): large beads (10 mm) used in Comparative Example 4 is 3:5:2, and the other parameters are the same as those in Example 1.

[0074] Compared with Example 1, the difference is that the weight ratio of small beads (1 mm): medium beads (5 mm): large beads (10 mm) used in Comparative Example 5 is 1:8:1, and the other parameters are the same as those in Example 1.

[0075] Compared with Example 1, the difference is that the ball milling time of Comparative Example 6 is 2 h, and the other parameters are the same as those of Example 1.

[0076] Compared with Example 1, the difference is that the ball milling time used in Comparative Example 7 is 15 h, and the other parameters are the same as those in Example 1.

[0077] Compared with Example 1, the difference is that Comparative Example 8 uses water as the ball milling medium, the mixing ratio of zeolite and water is 100 g / L, and the other parameters are the same as those of Example 1.

[0078] The zeolites of the test examples, embodiments 1 to 6 and comparative examples 1 to 8 are used in nitrogen / methane gas separation applications

[0079] The zeolites prepared in Examples 1 to 6 and Comparative Examples 1 to 8 were loaded into a gas penetration column. The specific testing method was as follows: first, the zeolites were vacuum activated at an activation temperature of 300°C for 10 h; then, gas distribution was performed, with a gas volume composition of nitrogen:methane = 1:1, a total flow rate of 2 mL, and argon as a reference gas; the mixed gas was passed into the penetration column, and online mass spectrometry was used at the end to obtain a multi-component penetration curve.

[0080] The results are shown in Table 2.

[0081] Table 2

[0082]

[0083] The results are shown in Table 2;

[0084] The test results of Example 1 show that the purity of methane can be increased from 50% to 75%. Figure 2 .

[0085] The test results of Example 2 show that the methane purity can be increased from 50% to 70%.

[0086] The test results of Example 3 show that the methane purity can be increased from 50% to 78%.

[0087] The test results of Example 4 show that the methane purity can be increased from 50% to 72%.

[0088] The test results of Example 5 show that the methane purity can be increased from 50% to 70%.

[0089] The test results of Example 6 show that the methane purity can be increased from 50% to 65%.

[0090] The ball milling speed of Comparative Example 1 is slow, and the particle size distribution of the first zeolite, the second zeolite, and the third zeolite is 5 μm-20 μm. The other parameters are the same as those of Example 1. Due to the large particle size, methane and nitrogen penetrate at the same time, and the purity of methane is almost not improved.

[0091] The ball milling time of Comparative Example 2 is shorter than that of Example 1. The particle sizes of the first zeolite, the second zeolite, and the third zeolite are 400 nm ≤A≤500nm, 400 nm ≤A≤500nm, and 800nm ​​≤C≤1μm, respectively. The other parameters are the same as those of Example 1. There is still mass transfer limitation, methane and nitrogen penetrate at the same time, and the purity of methane is almost not improved.

[0092] The mass ratio of the ball mill beads and zeolite used in Comparative Example 3 is 35:1. The particle sizes of the first zeolite, the second zeolite, and the third zeolite are very narrow, namely 80nm ≤A≤150nm, 80nm ≤B≤150nm, and 800nm ​​≤C≤1μm, respectively. The other parameters are the same as those in Example 1. There is a large pressure drop when penetrating the column, and methane and nitrogen penetrate almost simultaneously, and the purity of methane is only slightly improved.

[0093] The ball mill beads in Comparative Example 4 have a high proportion of beads, the mass ratio of the first zeolite, the second zeolite, and the third zeolite is 1:1:1, and the other parameters are the same as those in Example 1. There is still a mass transfer limitation, and methane and nitrogen penetrate at the same time, and the purity of methane is almost not improved.

[0094] The ball mill beads of Comparative Example 5 are mainly medium beads, and the mass ratio of the first zeolite, the second zeolite, and the third zeolite is 1:8:1. The other parameters are the same as those of Example 1. There is a mass transfer limitation, and methane and nitrogen penetrate almost simultaneously, and the purity of methane is only slightly improved.

[0095] The ball milling time of Comparative Example 6 was insufficient, and the pore volume of the first zeolite was 0.08 cm 3 / g, and the other parameters are the same as those in Example 1. The adsorption sites are not fully exposed, and methane and nitrogen penetrate at the same time, and the purity of methane is only slightly improved.

[0096] Comparative Example 7: The ball milling time was too long, and the pore volume of the second zeolite was 0.02 cm 3 / g, and the other parameters are the same as those in Example 1. There is a problem of poor zeolite crystallinity, and methane and nitrogen penetrate at the same time, and the purity of methane is almost not improved.

[0097] Comparative Example 8 uses water as the ball milling medium, and the pore volume of the third zeolite is 0.15 cm 3 / g, the zeolite loses its nitrogen-methane selectivity, methane and nitrogen penetrate simultaneously, and the methane purity is almost not improved.

[0098] Similarly, the separation performance of the zeolite of Example 1 in a nitrogen / methane / carbon dioxide mixture is as follows: Figure 3 shown.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application rather than to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present application.

Claims

1. A zeolite for gas separation, characterized in that: The zeolite includes a first zeolite, a second zeolite and a third zeolite with different particle size distributions; The average particle size of the first zeolite is A, A ≤ 200 nm; The average particle size of the second zeolite is B, 200 nm. The average particle size of the third zeolite is C, 600 nm. <C ≤5μm; The types of the first zeolite, the second zeolite and the third zeolite include at least one of clinoptilolite, mordenite, 4A zeolite, ZSM-5 zeolite and PHI zeolite; The mass ratio of the first zeolite, the second zeolite and the third zeolite is (5-8):(1-4):1; The first zeolite, the second zeolite and the third zeolite with different particle size distributions are prepared by ball milling zeolite with a particle size greater than 20 μm; The pore volume of the first zeolite is 0.1-0.2 cm 3 / g; The pore volume of the second zeolite is 0.05-0.1 cm 3 / g; The pore volume of the third zeolite is 0.01-0.05 cm 3 / g.

2. The zeolite for gas separation according to claim 1, characterized in that The mass ratio of the zeolite to the ball milling beads is 1:(3-30); The ball milling beads include small beads with a particle size of 1 mm, medium beads with a particle size of 5 mm, and large beads with a particle size of 10 mm; The weight ratio of the small beads, the medium beads and the large beads is (5-7): (2-3): (1-2).

3. Use of the zeolite as claimed in claim 1 or 2 in gas separation. The gas separation method comprises using the zeolite according to claim 1 or 2 to separate gases, wherein the gases comprise methane and a separation gas having the same kinetic diameter and characteristics as methane.

4. A gas separation method, characterized in that: The separated gas includes carbon dioxide and / or nitrogen; 5. The gas separation method according to claim 4, characterized in that: In the case of nitrogen / methane separation or carbon dioxide / methane separation, the volume ratio of methane to separation gas is 1:1, and the total flow rate of methane flow rate and separation gas flow rate is 2~20 sccm; in the case of nitrogen / methane / carbon dioxide separation, the volume ratio of nitrogen / methane / carbon dioxide is 5:30:65, and the total flow rate is 5~10 sccm; the purge gas is one of argon and helium, and the flow rate is 5~30 sccm. ​

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