A method for separating a mixed gas containing xenon and carbon dioxide

Abstract

The present invention relates to the technical field of gas separation, and discloses a method for separating a mixed gas containing xenon and carbon dioxide. The method includes: contacting the mixed gas containing xenon and carbon dioxide with a gas adsorbent to obtain a purified xenon-containing gas; the gas adsorbent is prepared by the following method: in the presence of a solvent, mixing and reacting zinc hydroxycarbonate, oxalic acid and 3-methyl-1,2,4-triazole to obtain the gas adsorbent; the mass ratio of the amounts of the zinc hydroxycarbonate, the oxalic acid and the 3-methyl-1,2,4-triazole is 1:0.8-1.2:4.0-4.5. The method provided by the present invention can have a high adsorption capacity and high selectivity for carbon dioxide and / or water vapor in the mixed gas containing xenon and carbon dioxide at room temperature, and can realize one-step adsorption of CO<subgt;2< / subgt; and water vapor from the exhaled medical anesthesia exhaust gas, and has good application prospects for the online recycling of medical anesthesia xenon.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and particularly relates to a method for separating a mixed gas containing xenon and carbon dioxide. Background Art

[0002] Nearly 60 years ago, the anesthetic properties of xenon on the human body were first described. Xenon is an ideal anesthetic, and compared with the commonly used anesthetic gas nitrous oxide at present, it has many medical and environmental advantages. For example, the anesthetic induction is fast, the recovery is fast, it is not easily affected by biotransformation, and it is currently the anesthetic with the least impact on the cardiovascular system. However, the biggest problem in introducing xenon into the clinical medical system is the increase in medical costs. Xenon is expensive (about 30,000 - 60,000 US dollars per standard cubic meter), and can only be obtained by cryogenic separation of air, with relatively high process energy consumption. Xenon exists in the atmosphere at a very low concentration (0.0000087%), and the market supply is extremely limited. While patients exhale anesthetic xenon, they also continuously exhale carbon dioxide. Therefore, carbon dioxide will continuously accumulate in the closed-loop system, and when it reaches a certain concentration, it will cause carbon dioxide poisoning. Therefore, it is necessary to remove the carbon dioxide in the closed-loop system in a timely manner.

[0003] WO1998 / 018718A1 discloses a method for cryogenic recovery of xenon from anesthetic tail gas. First, carbon dioxide is absorbed by using a 5 - 30% potassium hydroxide acetone solution, and then cryogenic separation is carried out. The xenon recovery rate is 90 - 92%. RU2238113C1 discloses a method for cryogenic recovery of xenon. Praxair Technology Inc in the United States and UWS Ventures LTD in the United Kingdom optimize the cryogenic process and recover xenon from cryogenic liquids or gas streams (US20040096147A1) and a two-stage cryogenic coupling method (WO2004 / 060459A1) respectively. Although xenon recovery can be achieved by utilizing the different phase change temperatures of xenon and other gas components, there are problems such as complex separation process flow and high operation cost.

[0004] Adsorption separation technology can usually obtain high-purity products, does not involve phase transformation, can significantly reduce the energy consumption of xenon recycling, and the operation is also simpler. It is a more economical and reliable technical route. As a new generation of porous materials, metal-organic framework materials (MOF) have great potential in solving current challenges related to energy and environmental sustainability due to their highly designable and adjustable pore sizes and chemical properties. Summary of the Invention

[0005] The object of the present invention is to provide a method that can have a high adsorption capacity and high selectivity for carbon dioxide and / or water vapor in a mixed gas containing xenon and carbon dioxide at normal temperature.

[0006] In order to achieve the above object, the present invention provides a method for separating a mixed gas containing xenon and carbon dioxide, the method comprising:

[0007] contacting and adsorbing a xenon-containing gas and carbon dioxide mixed gas with a gas adsorbent to obtain a purified xenon-containing gas;

[0008] The gas adsorbent is prepared by the following method:

[0009] In the presence of a solvent, basic zinc carbonate, oxalic acid and 3-methyl-1,2,4-triazole are mixed and reacted to obtain the gas adsorbent; the mass ratio of the basic zinc carbonate, the oxalic acid and the 3-methyl-1,2,4-triazole is 1:0.8-1.2:4.0-4.5.

[0010] The gas adsorbent provided by the present invention is an ideal separation material for separating mixed gases containing xenon and carbon dioxide. It has high selectivity, high adsorption capacity and long-term stability for carbon dioxide, and can greatly improve the separation efficiency.

[0011] The present invention preferably uses gas adsorbents in medical anesthetic exhaust gas containing xenon. The gas adsorbent provided by the present invention can remove carbon dioxide and water vapor from the anesthetic exhaust gas, while the unadsorbed xenon, nitrogen and oxygen can be directly recycled. It can achieve one-step adsorption of CO2 and water vapor from the exhaled medical anesthetic exhaust gas, significantly reducing equipment investment and floor space, and has good application prospects for the online recycling of medical anesthetic xenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 1 is the XRD pattern of the gas adsorbent CUPMOF-5 in Preparation Example 1 of the present invention under different states;

[0013] Figure 2 This is a comparison of the adsorption capacity of CO2, N2, O2 and Xe by NbOFFIVE-1-Ni and CUPMOF-5;

[0014] Figure 3 is the isothermal adsorption curve of water vapor on CUPMOF-5;

[0015] Figure 4 is the penetration curve of CUPMOF-5 for mixed gas;

[0016] Figure 5 is the desorption curve of CUPMOF-5 after adsorption of mixed gas;

[0017] Figure 6 This is the five-cycle breakthrough curve of CUPMOF-5 for mixed gas. DETAILED DESCRIPTION

[0018] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0019] The normal temperature referred to in the present invention means 10 - 30 °C.

[0020] As described above, the present invention provides a method for separating a mixed gas containing xenon and carbon dioxide, and the method includes:

[0021] Bringing the mixed gas containing xenon and carbon dioxide into contact adsorption with a gas adsorbent to obtain a purified xenon-containing gas;

[0022] The gas adsorbent is prepared by the following method:

[0023] In the presence of a solvent, zinc hydroxycarbonate, oxalic acid, and 3-methyl-1,2,4-triazole are mixed and reacted to obtain the gas adsorbent; the mass ratio of the amounts used of zinc hydroxycarbonate, oxalic acid, and 3-methyl-1,2,4-triazole is 1:0.8 - 1.2:4.0 - 4.5.

[0024] Preferably, the molecular formula of the zinc hydroxycarbonate is 3Zn(OH)2·2ZnCO3. The inventors of the present invention have found in the research that the gas adsorbent prepared by using zinc hydroxycarbonate with this molecular formula has more efficient carbon dioxide adsorption and separation performance and better selectivity.

[0025] Preferably, the temperature of the contact adsorption is 10 - 30 °C, and the pressure is 1 - 3 bar.

[0026] Preferably, the window diameter of the gas adsorbent is

[0027] The window diameter of the gas adsorbent referred to in the present invention refers to the size of the window on the pore of the gas adsorbent.

[0028] Preferably, the adsorption amount of the gas adsorbent for carbon dioxide at 298 K and 1 bar is ≥ 70.1 cm 3 / g, and more preferably ≥ 75.5 cm 3 / g.

[0029] Preferably, the adsorption amount of the gas adsorbent for carbon dioxide at 298 K and 0.05 bar is ≥ 54 cm 3 / g.

[0030] Preferably, at 298K and 100kPa, the selectivity of the gas adsorbent for carbon dioxide in the mixture of xenon and carbon dioxide is above 1.8×10 7 and more preferably above 2.2×10 8 .

[0031] The selectivity described in the present invention refers to the characteristic that the same adsorbent has different adsorption capacities for different adsorbates under the same conditions. The data of the selectivity in the present invention are calculated according to the Ideal Adsorbed Solution Theory (IAST).

[0032] According to a preferred specific embodiment, the volume ratio of xenon to carbon dioxide in the mixture of xenon and carbon dioxide is 51 - 84:5, preferably 62 - 67:5, and more preferably 64 - 65:5.

[0033] Preferably, the mixture of xenon and carbon dioxide further contains water vapor, and the gas adsorbent can adsorb the water vapor.

[0034] Preferably, at 25°C and 100kPa, the partial pressure of the water vapor in the mixture of xenon and carbon dioxide is 0.5 - 1.5kPa.

[0035] The gas adsorbent provided by the present invention can be used for the removal of both carbon dioxide and water vapor simultaneously, and the water vapor does not affect the adsorption capacity and selectivity of the gas adsorbent for carbon dioxide.

[0036] According to another preferred specific embodiment, the mixture of xenon and carbon dioxide is the medical anesthesia exhaust gas containing xenon, and the medical anesthesia exhaust gas contains: 62 - 67v% of xenon, 24 - 28v% of oxygen, 2 - 4v% of nitrogen, 4 - 6v% of carbon dioxide, and 0.5 - 1.5v% of water vapor.

[0037] The gas adsorbent provided by the present invention has a high carbon dioxide adsorption capacity and high selectivity in the on-line recycling of medical anesthesia exhaust gas, so that the recovery rate of xenon is above 99.8%, and it can maintain stable operation for a long time. The gas adsorption and separation method provided by the present invention has good application prospects in the field of on-line recycling of medical anesthesia xenon.

[0038] Preferably, the conditions of the mixed reaction satisfy: the temperature is 150 - 180°C and the time is 24 - 48h.

[0039] The preparation method of the gas adsorbent described in the present invention also includes conventional post-treatment means such as methanol washing, suction filtration, vacuum drying, and inert gas purging. Those skilled in the art can select according to the known technical means in the art, and the present invention will not elaborate here. Those skilled in the art should not understand it as a limitation to the present invention.

[0040] Preferably, the solvent is water and / or ethanol.

[0041] More preferably, the solvent is a combination of water and ethanol with a volume ratio of 1:0.8 - 1.2. The inventors of the present invention found in the research that the gas adsorbent obtained under this preferred condition has more excellent separation efficiency and better selectivity.

[0042] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are all commercially available products. The room temperature all represents 25 ± 2 °C.

[0043] Preparation Example 1

[0044] Zinc hydroxycarbonate (100 mg, 3Zn(OH)2 - 2ZnCO3), oxalic acid (100 mg, H2C2O4) and 3 - methyl - 1,2,4 - triazole (420 mg) were added to a mixed solvent (5 mL of water and 5 mL of ethanol), and the reaction was carried out at 180 °C for 36 h, and then post - treatment operations such as methanol washing, suction filtration and vacuum drying were carried out to prepare the gas adsorbent CUPMOF - 5.

[0045] Preparation Example 2

[0046] Zinc hydroxycarbonate (100 mg, ZnCO3 - 2Zn(OH)2 - H2O), oxalic acid (100 mg, H2C2O4) and 3 - methyl - 1,2,4 - triazole (420 mg) were added to a mixed solvent (5 mL of water and 5 mL of ethanol), and the reaction was carried out at 170 °C for 36 h, and then post - treatment operations such as methanol washing, suction filtration and vacuum drying were carried out to prepare the gas adsorbent CUPMOF - 6.

[0047] Preparation Example 3

[0048] The same procedure as in Preparation Example 1 was adopted, except that the mixed solvent of 5 mL of water and 5 mL of ethanol was replaced with 10 mL of water, and the rest remained unchanged;

[0049] The gas adsorbent CUPMOF - 7 was prepared.

[0050] Comparative Preparation Example 1

[0051] The same procedure as in Preparation Example 1 was adopted, except that zinc hydroxycarbonate (3Zn(OH)2 - 2ZnCO3) was replaced with an equal mass of zinc carbonate (ZnCO3), and the rest remained unchanged;

[0052] The gas adsorbent DMOF - 1 was prepared.

[0053] Comparative Preparation Example 2

[0054] A mixture of ZnCO3 (0.125 g), oxalic acid (0.09 g), 3-methyl-1,2,4-triazole (0.415 g), water (4 mL) and butanol (2 mL) was placed in a 20 mL Teflon autoclave, stirred at room temperature for 30 min, and then heated in a convection oven at 180 °C for 3 days. The gas adsorbent DMOF-2 was prepared.

[0055] Example 1: Single-component gas adsorption

[0056] The gas adsorbents obtained from the above Preparation Examples and Comparative Preparation Examples were tested.

[0057] NbOFFIVE-1-Ni is a gas adsorbent reported in the literature (Zeng J, Fu Y, Wu Y, et al. Absolute CO2 / Xenon separation in ultramicropore MOF for anesthetic gases regeneration[J]. Angewandte Chemie International Edition, 2023, 62(42): e202310235.). [[ID= twelfth]]

[0058] Test methods and conditions: 100 mg of the sample was activated under dynamic vacuum at 100 °C for 12 h. The following gas adsorption instrument was used to collect the adsorption isotherm: Microtrac’s BEL BELSORP-max II analyzer. The gases used were: Xe (99.999%), O2 (99.999%), N2 (99.99%), CO2 (99.99%).

[0059] The selectivities of CO2 / Xe (5 / 65, v / v), CO2 / N2 (5 / 3, v / v), and CO2 / O2 (5 / 27, v / v) at 298 K and 100 kPa were calculated according to the Ideal Adsorbed Solution Theory (IAST).

[0060] [[ID= nineteeth]]The results are shown in Tables 1 and 2.

[0061] Table 1

[0062]

[0063] Table 2

[0064] <![CDATA[CO2 / Xe selectivity]]> <![CDATA[CO2 / N2 selectivity]]> <![CDATA[CO2 / O2 selectivity]]> CUPMOF-5 <![CDATA[2.2×10 8 > <![CDATA[1×10 7 > <![CDATA[3.9×10 6 > CUPMOF-6 <![CDATA[2.1×10 7 > <![CDATA[1.7×10 6 > <![CDATA[3.8×10 5 > CUPMOF-7 <![CDATA[1.8×10 7 > <![CDATA[2.1×10 6 > <![CDATA[4.1×10 5 > DMOF-1 3500 2900 4890 DMOF-2 3149 2198 3500 NbOFFIVE-1-Ni 285 207 5317

[0065] As can be seen from the data in Table 1 and Table 2, the gas adsorbent prepared by the technical solution provided by the present invention has an extremely strong CO2 capture ability, extremely low adsorption amounts of Xe, N2, and O2, and excellent selective adsorption performance.

[0066] Figure 1 Figure shows the XRD patterns of the gas adsorbent CUPMOF-5 prepared in Example 1 of the present invention under different states, where a is the theoretically simulated XRD pattern, b is the XRD pattern of the as-synthesized CUPMOF-5, c is the XRD pattern of CUPMOF-5 after adsorbing gas, d is the XRD pattern of CUPMOF-5 after adsorbing water vapor, and e is the XRD pattern of CUPMOF-5 after the cyclic breakthrough experiment. As can be seen from Figure 1 this, the gas adsorbent CUPMOF-5 has extremely high stability.

[0067] Figure 2 Figure

[0066] shows the comparison of the adsorption amounts of CO2, N2, O2, and Xe on NbOFFIVE-1-Ni and CUPMOF-5 at 298K. As can be seen from the figure, the CO2 saturated adsorption amount of CUPMOF-5 (75.5 cm 3 / g) is nearly twice that of the previously reported best adsorbent NbOFFIVE-1-Ni (44.8 cm 3 / g). CUPMOF-5 shows a steep CO2 adsorption curve in the low-pressure region and extremely low adsorption amounts of Xe, N2, and O2. Especially when the partial pressure of CO2 in the actual exhaled anesthetic gas mixture is 5 kPa, the CO2 adsorption amount of CUPMOF-5 (54 cm 3 / g) is significantly higher than that of the best-performing material NbOFFIVE-1-Ni (38.4 cm 3 / g), indicating its extremely strong CO2 capture ability in the low-pressure region. In contrast, the window diameter of CUPMOF-5 is smaller, which is [[ID=l9]] completely blocking the entry of Xe, N2, and O2 molecules. At 298K and 100 kPa, the adsorption amounts of CUPMOF-5 for Xe, N2, and O2 are extremely low (1.17, 0.172, and 1.02 cm 3 / g), respectively, which are much lower than the adsorption amounts of NbOFFIVE-1-Ni (4.26, 2.74, and 2.75 cm 3 / g). Therefore, the gas adsorbent provided by the present invention will be an ideal adsorption separation material for CO2 / Xe separation. Based on the high selectivity and high CO2 adsorption capacity of the gas adsorbent of the present invention, the separation efficiency will be greatly improved.

[0068] Figure 3It is the isothermal adsorption curve of water vapor on CUPMOF-5 under the condition of 298K. It can be seen from the figure that CUPMOF-5 can adsorb water vapor, and the adsorption of water vapor does not affect the adsorption of CO2. Therefore, by using the gas adsorbent provided by the present invention, it is possible to adsorb CO2 and water vapor in one step from the exhaled medical anesthesia waste gas containing xenon, which can significantly reduce the equipment investment and floor area, and has good application prospects for the on-line recycling of medical anesthesia xenon.

[0069] Example 2: Dynamic breakthrough experiment

[0070] In order to simulate the separation performance under the actual conditions of medical anesthesia xenon recycling, a dynamic breakthrough experiment was carried out. The present invention exemplarily provides the dynamic breakthrough experiment effect data of CUPMOF-5 obtained in Preparation Example 1.

[0071] Before the breakthrough experiment, a mass spectrometer (HIDEN HPR-20EGA) was calibrated using a mixed gas (Xe / O2 / N2 / CO2 / water vapor, volume ratio 65 / 26 / 3 / 5 / 1). The CUPMOF-5 material obtained in Example 1 was filled into a breakthrough tube (inner diameter 10 cm, length 13 cm), and the filling mass was 10 g. First, it was purged with helium at 373K for 14h, and the flow rate was 20 mL / min. When the temperature dropped to room temperature, a mixed gas (Xe / O2 / N2 / CO2 / water vapor, volume ratio 65 / 26 / 3 / 5 / 1) was introduced into the breakthrough tube at a flow rate of 8 mL / min. The outlet gas concentration was detected using a mass spectrometer (HIDEN HPR-20EGA). The breakthrough curve is as Figure 4 shown. Secondly, at 323K, it was purged with helium (20 mL / min) for desorption, and the gas concentration at the outlet of the breakthrough tube was monitored using a mass spectrometer. The desorption curve is as Figure 5 shown.

[0072] Figure 4 It is the breakthrough curve of CUPMOF-5 for the mixed gas at 298K and 1 bar; it can be seen from the figure that Xe, N2 and O2 break through immediately, while CO2 has a longer residence time (145 min / g). Water vapor does not affect the CO2 capture amount and gas screening ability of CUPMOF-5. Using CUPMOF-5 can remove CO2 and water vapor in the anesthesia xenon recycling closed-loop system in one step, showing great potential for the efficient and practical recycling of anesthesia xenon.

[0073] Figure 5 It is the desorption curve of CUPMOF-5 after adsorbing the mixed gas under the condition of purging with helium at 323K and 20 mL / min; at 323K, the desorption performance of CUPMOF-5 in the breakthrough column was measured by purging with helium with a flow rate of 20 mL / min. As Figure 5As shown, within 1.5 min / g, only the CO2 and H2O signals are dominant, which further proves that Xe, N2, and O2 are hardly adsorbed in the bed. The yield of the desorbed gas indicates that only 0.2% of Xe is retained in the breakthrough column, meaning that 99.8% of Xe is recovered during the adsorption step.

[0074] Figure 6 is the breakthrough curve of the mixed gas by CUPMOF-5 for five cycles under the conditions of 298K and 1 bar; then the cyclic stability of CUPMOF-5 was tested, and five consecutive adsorption-desorption breakthrough experiments were carried out. It can be seen from the figure that CUPMOF-5 has excellent regenerability and stability.

[0075] In summary, CUPMOF-5 has great application potential in the field of separating the mixed gas containing xenon and carbon dioxide, especially in removing CO2 and water vapor from exhaled anesthetic gas mixtures.

[0076] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for separating a mixed gas containing xenon and carbon dioxide, characterized in that, The method includes: Contact and adsorb a mixture of xenon and carbon dioxide with a gas adsorbent to obtain a purified xenon-containing gas; the window diameter of the gas adsorbent is The gas adsorbent has an adsorption capacity for carbon dioxide of ≥ 70.1 cm 3 / g at 298 K and 1 bar; The gas adsorbent is prepared by the following method: In the presence of a solvent, zinc hydroxycarbonate, oxalic acid, and 3-methyl-1,2,4-triazole are mixed and reacted to obtain the gas adsorbent; the mass ratio of the zinc hydroxycarbonate, the oxalic acid, and the 3-methyl-1,2,4-triazole is 1:0.8 - 1.2:4.0 - 4.5; The solvent is a combination of water and ethanol with a volume ratio of 1:0.8 - 1.

2.

2. The method according to claim 1, characterized in that The temperature of the contact adsorption is 10 - 30 °C, and the pressure is 1 - 3 bar.

3. The method according to claim 1 or 2, characterized in that, The gas adsorbent has a carbon dioxide adsorption capacity of ≥ 54 cm 3 / g at 298K and 0.05 bar.

4. The method according to claim 1 or 2, characterized in that Under the conditions of 298K and 100 kPa, the selectivity of the gas adsorbent for carbon dioxide in the mixed gas containing xenon and carbon dioxide is above 1.8×10 7 above.

5. The method according to claim 1 or 2, characterized in that, The volume ratio of xenon to carbon dioxide in the xenon- and carbon dioxide-containing mixed gas is 51 - 84:

5.

6. The method according to claim 1 or 2, characterized in that The xenon- and carbon dioxide-containing mixed gas further contains water vapor, and the gas adsorbent can adsorb the water vapor.

7. The method according to claim 1 or 2, characterized in that The xenon- and carbon dioxide-containing mixed gas is medical anesthesia exhaust gas containing xenon, and the medical anesthesia exhaust gas contains: 62 - 67 v% of xenon, 24 - 28 v% of oxygen, 2 - 4 v% of nitrogen, 4 - 6 v% of carbon dioxide, and 0.5 - 1.5 v% of water vapor.

8. The method according to claim 1 or 2, characterized in that The conditions of the mixed reaction are satisfied: the temperature is 150 - 180 °C, and the time is 24 - 48 h.

Images