Method for capturing CO2 from diluted CO2 streams of varying humidity, including natural gas combined cycle waste stream and ambient air stream, using KAUST-7-based physical adsorbents

Abstract

A method for capturing carbon dioxide (CO2) from a moist gas stream is provided. In certain embodiments, the gas stream is a humid natural gas combined cycle (NGCC) waste stream. In certain embodiments, the gas stream is a moist air stream. The moist gas stream comprises CO2 and oxygen (O2). In the method, the moist gas stream is contacted with a metal organic framework (MOF) material KAUST-7. The CO2 from the moist gas stream is captured with the KAUST-7MOF material to produce a CO2 concentrated gas stream comprising about 1 to 30% CO2.

Description

Technical Field

[0001] The present disclosure relates to methods for capturing CO2 from gas streams, and in particular to methods for capturing CO2 from gas streams with different humidities that contain low CO2 concentrations (such as natural gas combined cycle waste streams and ambient air). Background Art

[0002] Reducing carbon dioxide (CO2) emissions into the atmosphere remains a top priority in the fight against global warming. The concentration of CO2 in the atmosphere has recently reached approximately 415 ppm and is continuously increasing at a rate of 2 - 3 ppm per year. These increases in atmospheric CO2 concentration over the last century (mainly due to industrial and vehicle CO2 emissions) are directly related to global warming. Without halting or drastically reducing CO2 emissions, the world will soon cross the critical point of 450 ppm CO2 concentration, which could lead to a series of environmental disasters.

[0003] Since the world is likely to remain dependent on fossil fuels for the next few decades, CO2 capture is an important technology for mitigating CO2 emissions. Many efforts have been made in recent years to develop materials and technologies for capturing CO2 from flue gas (industrial emissions) as well as directly from air (direct air capture). For example, CO2 capture from flue gas is currently carried out at 10 - 15% CO2 concentration, and there are several emerging technologies for this purpose.

[0004] However, direct air capture is more complex because it requires capturing CO2 from a gas (air) with a CO2 concentration of 400 ppm (more than 200 times lower than flue gas). The advantage of direct air capture is that the capture can be carried out anywhere in the world, and it can handle emissions from diffuse sources such as the transportation sector. Among the materials studied, liquid amines and other amine-based chemisorbents have shown promise for both applications. However, these chemisorbent materials require very high energy for regeneration (100 - 120 kJ / mol), which effectively offsets the positive impact of CO2 capture. Moreover, amine-based materials are prone to degradation and produce toxic decomposition products, which may have an adverse impact on the environment.

[0005] Another approach is to use physical adsorbent materials, where the driving force for CO2 adsorption is the non-bonding interaction between the physical adsorbent material and CO2. Metal-organic frameworks (MOFs) are a relatively new class of adsorbents that have recently received a lot of attention, mainly due to their crystalline and modular nature, which can be used for a variety of applications such as separation, storage, catalysis, sensors, electrochemistry, and so on. In the past few years, many MOF materials have shown significant CO2 capture properties.

[0006] CO2 capture from natural gas combined cycle (NGCC) power plants is another challenging CO2 capture application. NGCC is more efficient and environmentally friendly than traditional coal-based power plants, and thus, most future fossil fuel-based power plants are expected to use natural gas. Therefore, technologies capable of capturing CO2 from NGCC equipment are needed. However, there are currently no materials that can reliably and economically capture CO2 from NGCC flue gases (e.g., 4% CO2, 10 - 13% O2). The main difficulties in NGCC CO2 capture are the low CO2 concentration and high oxygen content in the flue gas stream. Most materials do not meet the combined requirements of adequate CO2 capacity at 4% CO2 concentration in the presence of moisture (humidity) and good oxygen stability at high temperatures.

[0007] Regarding the above background information, the present disclosure aims to provide a technical solution for capturing CO2. Summary of the Invention

[0008] According to a first aspect, a method for capturing CO2 from a humid natural gas combined cycle (NGCC) waste stream is provided. In the method, the humid NGCC waste stream is contacted with a metal-organic framework (MOF) material KAUST-7. The humid NGCC waste stream contains approximately 1 - 5% CO2 and approximately 10 - 13% oxygen (O2). Then, the MOF material KAUST-7 is used to capture CO2 from the humid NGCC waste stream to produce a CO2-enriched gas stream containing approximately 1 - 30% CO2, wherein the relative humidity of the humid NGCC waste stream is approximately 45 - 75% at 20 - 85 °C. In another aspect, the relative humidity of the humid NGCC waste stream is approximately 50 - 70% at 20 - 85 °C. In another aspect, the relative humidity of the humid NGCC waste stream is approximately 55 - 65% at 20 - 85 °C. In another aspect, the balance of the humid NGCC waste stream is N2. In another aspect, CO2 is captured with the MOF material KAUST-7 at a temperature in the range of approximately 20 - 85 °C and a pressure in the range of approximately 1 - 5 bar.

[0009] In a second aspect, a method for capturing CO2 from a humid air stream is provided. In the method, the humid air stream is contacted with a metal-organic framework (MOF) material, KAUST-7. The humid air stream contains about 400 - 1000 ppm of CO2 and about 20 - 25% of O2. Then, the CO2 from the humid air stream is captured with the MOF material KAUST-7 to produce a CO2-enriched gas stream containing about 1 - 30% CO2. The relative humidity of the humid air stream is about 5 - 75% at 0 - 55 °C. In another aspect, the humid air stream contains about 400 - 800 ppm of CO2. In another aspect, the relative humidity of the humid air stream is about 50 - 70% at 0 - 55 °C. In another aspect, the relative humidity of the humid air stream is about 55 - 65% at 0 - 55 °C. In another aspect, the balance of the humid air stream is N2 and O2. In another aspect, the CO2 is captured with the MOF material KAUST-7 at a temperature in the range of about 0 - 55 °C and a pressure in the range of about 1 - 5 bar.

[0010] In certain embodiments, the MOF material KAUST-7 is in the form of pellets, laminates, or other structured forms. In certain embodiments, the MOF material KAUST-7 is pretreated at a temperature in the range of about 60 - 150 °C under dynamic vacuum or dry inert gas to remove any previously adsorbed molecules. In certain embodiments, the MOF material KAUST-7 contains an organic binder or an inorganic binder.

[0011] Any combination of the various embodiments and implementations disclosed herein may be used. These and other aspects and features can be understood from the following description of certain embodiments, as well as the drawings and the claims. Description of the Drawings

[0012] The processes of the present disclosure will be described in more detail below with reference to the drawings.

[0013] Figure 1 A bar graph is shown which illustrates that the CO2 adsorption capacity of the KAUST-7 MOF remains the same after 10 oxygen exposure cycles at high temperature, indicating the high oxygen stability of the material according to one or more embodiments. Each cycle includes exposing the sample to hot air at 110 °C for 60 minutes.

[0014] Figure 2 A flow chart is shown which illustrates the steps of a method for capturing CO2 from a humid gas stream using the KAUST-7 MOF physical adsorbent according to one or more embodiments.

[0015] Figures 3A - 3BShows the breakthrough experiment of KAUST-7 (3A) with 10% CO2 (balance N2) and humidity (65% RH) at a flow rate of 5 cc / min and the results of (3B) the corresponding TPD after CO2 breakthrough.

[0016] Figures 4A - 4B Shows the breakthrough experiment of KAUST-7 (4A) with 10% CO2 (balance N2) and humidity (65% RH) at a flow rate of 5 cc / min (stopped between CO2 and H2O breakthrough), and the results of (4B) the corresponding TPD between CO2 and H2O breakthrough.

[0017] Figures 5A - 5B Shows the breakthrough experiment of KAUST-7 (5A) with 10% CO2 (balance N2) and humidity (65% RH) at a flow rate of 5 cc / min (stopped after H2O breakthrough), and the results of (5B) the corresponding TPD after H2O breakthrough.

[0018] Figures 6A - 6B Shows the breakthrough experiment of KAUST-7 (6A) with 1% CO2 (balance N2) at a flow rate of 25 cc / min under dry conditions at 298K, and the results of (6B) the corresponding TPD after the CO2 breakthrough experiment under dry conditions.

[0019] Figures 7A - 7B Shows the breakthrough experiment of KAUST-7 (7A) with 1% CO2 (balance N2) at a flow rate of 25 cc / min in the presence of humidity (50% RH) at 298K, and the corresponding TPD after water breakthrough. Detailed Description

[0020] Disclosed herein are methods for capturing CO2 from gas streams having different humidities and containing low CO2 concentrations (400 ppm to 5% CO2). A metal-organic framework (MOF) material, specifically the KAUST-7 (NbOFFIVE-1-Ni) physical adsorbent, is used to physically adsorb CO2 from the humid gas stream. In the method, the MOF KAUST-7 effectively captures CO2 from gas streams having different humidities, and the captured CO2 can thereby be recovered in the form of a concentrated CO2 stream (e.g., approximately 1 - 30% CO2). In the method, for example, the gas stream can be a natural gas combined cycle (NGCC) waste stream or an ambient air stream, or a humid air stream having different humidities.

[0021] Direct air CO2 capture and CO2 capture from NGCC waste are considered to be very difficult compared to capturing CO2 (10 - 15% CO2) from flue gas streams. Further, capturing CO2 from humid gas streams generally causes further difficulties because moisture from H2O molecules typically interferes with the capture ability of conventional capture methods and other physical sorbents. For example, liquid or solid - loaded amines have previously been used in CO2 capture methods, but they are prone to degradation with increasing oxygen levels, which can lead to corrosion. Similarly, zeolites and other physical sorbents are used in some conventional CO2 capture methods but can be susceptible to interference from water, which can affect their capture ability. However, the present method using the KAUST - 7 physical sorbent results in surprisingly efficient CO2 capture from NGCC waste streams and air streams, even when the streams are humid gas streams. Thus, the present method can further expand the scope of CO2 capture technologies and accelerate efforts to mitigate the increase in atmospheric CO2 concentration and the accompanying global warming.

[0022] These and other aspects of the present system and method are described in further detail below. Further, as used in this application, when used in conjunction with a numerical value, the term "about" refers to any number within approximately 5%, 3%, or 1% of the recited numerical value, including the recited numerical value.

[0023] As described above, according to one or more embodiments, the CO2 capture portion of the method of the present application is carried out using the MOF material KAUST - 7 (NbOFFIVE - 1 - Ni; CAS: 1973399 - 07 - 3). KAUST - 7 exhibits excellent O2 stability at high temperatures, as presented in the examples of Figure 1 Figure 1 A bar graph is shown that depicts the results of an experiment evaluating the CO2 adsorption capacity of KAUST - 7 MOF upon repeated exposure to O2 at high temperatures. In the experiment, the KAUST - 7 MOF was subjected to 10 cycles of O2 exposure at high temperature, where each cycle consisted of exposing the KAUST - 7 MOF sample to hot air at 110 °C for 60 minutes. As shown in the bar graph of Figure 1 KAUST - 7 exhibited a consistent CO2 adsorption capacity after 10 cycles of oxygen exposure at high temperature, indicating the high oxygen stability of the KAUST - 7 MOF material.

[0024] Moreover, unlike many other physical sorbents, the moisture interference in CO2 capture by KAUST - 7 MOF is negligible, which allows KAUST - 7 MOF to be particularly suitable for capturing CO2 from humid NGCC waste streams and other humid gas streams.

[0025] In one or more embodiments, the KAUST-7MOF material is in the form of pellets, laminates, or other structured forms of the MOF (e.g., monoliths or any other structured form that holds the MOF particles in a specific shape). The KAUST-7MOF material may also include one or more suitable binders (e.g., organic or inorganic binders). In at least one embodiment, the one or more binders may include, but are not limited to, one or more of the following: organic polymers (e.g., polyethylene, polystyrene, polyethylene glycol, polyvinyl alcohol, polysulfone, polymethyl methacrylate) and inorganic binders (e.g., kaolinite, gypsum). The KAUST-7 and binder composition may be in the range of 95:5 to 70:30. In at least one embodiment, cylindrical pallets may be prepared with a composition having 90% KAUST-7 and 10% polymethyl methacrylate type binder.

[0026] In one or more embodiments, the KAUST-7MOF material of the method may be in a closed module that includes the KAUST-7MOF material and a binder. In at least one embodiment, the closed module may include one or more gas valves configured to manipulate the flow of the gas stream within the module.

[0027] Figure 2 A flowchart according to one or more embodiments is provided, which shows the steps of a method for capturing CO2 from a humid gas stream using the KAUST-7MOF physical adsorbent of the present invention. Now refer to Figure 2 the flowchart of, the method 100 begins at step S105, where the KAUST-7MOF material is pretreated under an air stream, vacuum, or other method at a suitable temperature. In one or more embodiments, prior to introducing the gas stream into the KAUST-7MOF material, the pretreatment of the KAUST-7MOF material removes any previously adsorbed molecules (e.g., H2O) and other guest molecules. The pretreatment of the KAUST-7MOF material may improve its ability to adsorb target molecules (e.g., CO2) in its adsorption pores. In one or more embodiments, during the pretreatment, the KAUST-7MOF material is subjected to a temperature in the range of about 60 - 150 °C under a dynamic vacuum or a dry inert gas (e.g., N2, O2, Ar, He, or air) stream. In embodiments where the KAUST-7MOF material used in the method is in a closed module, the pretreated KAUST-7MOF material is incorporated into the closed module together with, for example, a binder. In one or more embodiments, the pretreatment of the KAUST-7MOF material is carried out after the KAUST-7MOF material has been incorporated into the closed module.

[0028] In one or more embodiments, the pretreatment of the KAUST-7MOF material is optional, and the as-made KAUST-7MOF material can be loaded into a closed module.

[0029] Continuing with reference Figure 2 , in step S110, a humid gas stream is introduced into the KAUST-7MOF material. In one or more embodiments, the humid gas stream is a humid NGCC waste stream containing approximately 1% to 5% CO2 and approximately 10 - 13% O2. In at least one embodiment, the humid NGCC waste stream contains approximately 1 - 10% CO2 and approximately 10 - 13% O2. In one or more embodiments, the remainder or balance of the humid NGCC waste stream is N2 (e.g., approximately 77% to approximately 89% of the NGCC waste stream). In one or more embodiments, the humid NGCC waste stream contains approximately 400 ppm - 4%, 400 ppm - 3%, 400 ppm - 2%, 400 ppm - 1%, 1 - 5% or 4% CO2. In one or more embodiments, the relative humidity (RH) of the humid NGCC waste stream is approximately 45 - 75%, 45 - 70%, 50 - 70%, 50 - 65%, 50 - 60% or 55 - 65% at 20 - 85 °C. In at least one embodiment, the relative humidity of the humid NGCC waste stream is approximately 50% at 20 - 85 °C. In at least one embodiment, the relative humidity of the humid NGCC waste stream is approximately 65% at 20 - 85 °C. In one or more embodiments, the NGCC exhaust gas stream further contains 2 - 10% H2O vapor. In one or more embodiments, the NGCC exhaust gas may include other components, such as small proportions of SO2 and NO x .

[0030] In one or more embodiments, the humid gas stream can be first cooled to a suitable temperature (approximately 0 - 55 °C) before contacting the KAUST-7MOF material. In at least one embodiment, the temperature during the adsorption (capture) of the KAUST-7MOF material is also within the same temperature range (e.g., approximately 0 - 55 °C), and the temperature of the incoming gas stream helps to maintain a similar temperature.

[0031] In one or more embodiments, the humid gas stream is a humid air stream containing about 400 - 1000 ppm, 400 - 900 ppm, 400 - 800 ppm, 400 - 700 ppm, 400 - 600 ppm, or 400 - 500 ppm of CO2 and about 20 - 25% of O2. In one or more embodiments, the balance of the humid air stream is N2 and O2. In one or more embodiments, the humid air stream contains about 400 ppm of CO2. In one or more embodiments, at 0 - 55 °C, the relative humidity of the humid air stream is about 5 - 75%, 10 - 75%, 15 - 75%, 20 - 75%, 25 - 75%, 30 - 75%, 35 - 75%, 40 - 75%, 45 - 75%, 50 - 70%, 50 - 60%, or 55 - 65%. In at least one embodiment, the relative humidity of the humid air stream is about 50% at 0 - 55 °C. In at least one embodiment, the relative humidity of the humid air stream is about 65% at 0 - 55 °C. In one or more embodiments, the humid air stream can be breathable air (e.g., atmospheric air), which can include one or more of nitrogen (N2), oxygen (O2), and argon (Ar) in addition to CO2.

[0032] In one or more embodiments, the flow rate of the humid gas stream (e.g., humid air stream, humid NGCC waste stream) depends on the capacity of the equipment (e.g., NGCC equipment) and can thus be any flow rate of, for example, NGCC waste.

[0033] Once the humid gas stream contacts the KAUST - 7MOF material, in step S115, CO2 in the humid gas stream is captured by the KAUST - 7MOF material. In one or more embodiments, the capture of CO2 includes physical adsorption of CO2 by the KAUST - 7MOF material. In one or more embodiments, the KAUST - 7MOF material has a CO2 adsorption capacity in the range of about 0.5 wt% - 10 wt%. In one or more embodiments, the KAUST - 7MOF material also becomes water - saturated under the humid conditions of the humid gas stream (humid NGCC waste stream, humid air stream).

[0034] In one or more embodiments, CO2 is captured from the humid NGCC waste stream by the KAUST - 7MOF material at a temperature in the range of about 20 - 85 °C. In one or more embodiments, CO2 is captured from the humid air stream by the KAUST - 7MOF material at a temperature in the range of about 0 - 55 °C.

[0035] In one or more embodiments, CO2 is captured from the humid gas stream by the KAUST-7MOF material at a pressure in the range of about 1 - 5 bar.

[0036] In one or more embodiments, capturing the CO2 may include fully or partially containing CO2 within the pores of the KAUST-7MOF material.

[0037] In one or more embodiments, such as embodiments of the KAUST-7MOF in a closed module, the capture of the CO2 results in the generation of a CO2-free (or substantially CO2-free) stream (i.e., the residue of the gas stream from which CO2 is captured) in the KAUST-7-based closed module, and once the KAUST-7MOF material is saturated with CO2, the CO2-free gas stream can be discharged from the closed module to the atmosphere or optionally subjected to additional treatment, e.g., to remove other components such as SO2 and NO x 。

[0038] In one or more embodiments, the captured CO2 in the KAUST-7MOF material can be provided later as a CO2-rich stream (CO2-enriched gas stream). In one or more embodiments, hot air, hot nitrogen, vacuum, or other suitable methods or combinations thereof can be used to recover the adsorbed CO2 from the KAUST-7MOF material to produce the CO2-rich gas stream. In one or more embodiments, the resulting CO2-rich stream contains about 1 - 30% CO2. In one or more embodiments, the resulting CO2-rich stream contains about 5 - 30% CO2, 10 - 30% CO2, 15 - 30% CO2, 20 - 30% CO2, 1 - 20% CO2, 5 - 20% CO2, or 10 - 20% CO2. In at least one embodiment, the resulting CO2-rich stream can be directly purified later (CO2 purification), or can be mixed with another industrial waste stream having a similar CO2 concentration before purification. In one or more embodiments, the resulting CO2-rich stream is subsequently purified to produce a pure or substantially pure (at least 90%) CO2 stream. The purification of the CO2-rich stream can be carried out via a CO2 purification unit or via other techniques known in the art.

[0039] In at least one embodiment, the resulting CO2-rich stream is not subsequently purified and can be used as such for future applications, e.g., in a greenhouse to obtain better agricultural product yields.

[0040] By capturing CO2 via adsorption, the KAUST-7MOF material becomes saturated. In at least one embodiment, once the MOF material is saturated with CO2, the humid gas stream is stopped from contacting the KAUST-7MOF material. In at least one embodiment, for example, when the KAUST-7MOF material is part of an enclosed module, the enclosed module may include one or more gas valves for receiving and dispersing the gas stream. The gas valves are configured to manipulate the flow of the gas stream within the enclosed module. For example, in one or more embodiments, when the KAUST-7MOF material is saturated, the gas stream is stopped from entering the enclosed module by closing one or more valves of the enclosed module. In at least one embodiment, the gas stream is prevented from entering the enclosed module by closing one or more valves of the NGCC waste unit.

[0041] Finally, in step S120, the method ends. In one or more embodiments, the cycle time length of the CO2 capture method of the present application can vary from about 1 minute to about 30 minutes. However, it should be understood that in at least one embodiment, the time length can vary even beyond the above range based on many factors (such as the amount of KAUST-7 material used, flow rate, etc.).

[0042] Referring to FIGS. 3-7, the foregoing features and aspects of the present system and method are described in further embodiments below. These embodiments utilize the exemplary MOF material KAUST-7 of the present system and method. As illustrated in FIGS. 3-7, KAUST-7 provides excellent CO2 capture from humid streams and excellent oxygen stability.

[0043] Examples

[0044] To understand the H2O / CO2 co-adsorption by KAUST-7, a humid CO2 breakthrough experiment was conducted, and then temperature-programmed desorption (TPD) experiments were used for the adsorption phase analysis. Humid gas streams with 10% and 1% CO2 concentrations were used for the experiments. The results show that for gas streams with 1-10% CO2 concentration, even after water breakthrough (saturating the column with water vapor), humidity has a minimal effect on the CO2 capture ability of the KAUST-7MOF material. Therefore, it can be concluded that humidity has a minimal effect on the CO2 capture performance of KAUST-7, and KAUST-7 maintains good CO2 capture performance under NGCC waste conditions (e.g., humid gas containing about 4% CO2).

[0045] Experiments conducted at 65% RH with 10% CO2 (balance N2) (FIGS. 3-5)

[0046] A breakthrough experiment was conducted on KAUST-7 with a gas composition of 10% CO2 (balance N2) and humidity (65% RH) at a flow rate of 5 cc / min at 298 K. The breakthrough curve shows that CO2 breaks through at 94 min / g, corresponding to 2.0 mmol / g, and water breaks through at 526 min / g, corresponding to 2.5 mmol / g. To gain more insight into the adsorbed phase composition and if CO2 remains adsorbed after the water breakthrough, temperature-programmed desorption (TPD) was carried out at different stages of the breakthrough experiment: 1) after CO2 breakthrough, 2) between CO2 and H2O breakthroughs, and 3) after H2O breakthrough.

[0047] 1) After CO2 breakthrough ( Figures 3A - 3B )

[0048] Figures 3A - 3B Shows the ( Figure 3A ) breakthrough experiment of KAUST-7 carried out with 10% CO2 (balance N2) and humidity (65% RH) at a flow rate of 5 cc / min and the ( Figure 3B ) corresponding results of TPD after CO2 breakthrough. The breakthrough experiment was stopped immediately after CO2 breakthrough (≈94 min / g, ≈2.0 mmol / g). The TPD experiment was carried out immediately afterwards, and the adsorbed phase contained ≈2.0 mmol / g CO2 and ≈0.5 mmol / g H2O.

[0049] 2) Between CO2 and H2O breakthroughs ( Figures 4A - 4B )

[0050] Figures 4A - 4B Shows the ( Figure 4A ) breakthrough experiment of KAUST-7 carried out with 10% CO2 (balance N2) and humidity (65% RH) at a flow rate of 5 cc / min stopped between CO2 and H2O breakthroughs and the ( Figure 4B ) corresponding results of TPD between CO2 and H2O breakthroughs. The breakthrough experiment was stopped between CO2 and H2O breakthroughs after a normalized time of 250 min / g. The TPD experiment was carried out immediately afterwards, and the adsorbed phase contained ≈2.0 mmol / g CO2 and ≈1.3 mmol / g H2O.

[0051] 3) After H2O breakthrough ( Figures 5A - 5B )

[0052] Figures 5A - 5B Shows the ( Figure 5A ) breakthrough experiment of KAUST-7 carried out with 10% CO2 (balance N2) and humidity (65% RH) at a flow rate of 5 cc / min stopped after H2O breakthrough and the ( Figure 5B)The corresponding results of TPD after H2O breakthrough. The breakthrough experiment was stopped at the normalized time of 660 min / g after H2O breakthrough (526 min / g, ≈2.5 mmol / g). Immediately after that, a TPD experiment was carried out, and the adsorbed phase contained ≈1.8 mmol / g CO2 and ≈2.67 mmol / g H2O (Figure 4).

[0053] It is evident from these experiments that under the above conditions (10% CO2 in the presence of 65% RH humidity), even after water breakthrough, the CO2 concentration in the adsorbed phase is minimally affected by water.

[0054] Experiments were carried out with 1% CO2 (balance N2) under dry and humid conditions (50% RH)

[0055] Similar experiments were also carried out with a gas containing 1% CO2 (balance N2) under dry and humid conditions (50% RH).

[0056] 1) 1% CO2 breakthrough and corresponding TPD under dry conditions

[0057] Figures 6A - 6B showed ( Figure 6A ) the breakthrough experiment of KAUST-7 with 1% CO2 (balance N2) at a flow rate of 25 cc / min at 298 K under dry conditions, and ( Figure 6B ) the corresponding results of TPD after the CO2 breakthrough experiment under dry conditions, where CO2 breakthrough occurred at the normalized time of 170 g / min, corresponding to 1.9 mmol / g CO2 absorption. The TPD experiment was carried out after the breakthrough experiment.

[0058] 2) 1% CO2 breakthrough experiment and corresponding TPD in the presence of humidity (50% RH)

[0059] Figures 7A - 7B showed ( Figure 7A ) the breakthrough experiment of KAUST-7 with 1% CO2 (balance N2) at a flow rate of 25 cc / min at 298 K in the presence of humidity (50% RH), and ( Figure 7B ) the corresponding TPD after water breakthrough, where CO2 breakthrough occurred at the normalized time of 135 min / g (≈1.5 mmol / g CO2), and H2O breakthrough occurred at the normalized time of 155 min / g (≈2.6 mmol / g H2O). The breakthrough experiment was well stopped after H2O breakthrough (normalized time 260 min / g) and TPD was carried out. The TPD experiment showed that the adsorbed phase contained ≈1.4 mmol / g CO2 and ≈2.85 mmol / g H2O.

[0060] It can be clearly seen from the above experiments (where the CO2 concentration in the gas ranges from 10% to 1% in the presence of humidity) that the CO2 absorption at saturation (after water penetration) decreases as the CO2 concentration decreases. However, even for 1% CO2 (50% RH), the adsorbed phase contains 1.4 mmol / g of CO2 after water penetration, which is surprising because in most physical adsorbents, water replaces most of the CO2 at this concentration. These experiments show that for gases with a low CO2 concentration of 1%, KAUST-7MOF exhibits good CO2 absorption in the presence of humidity.

[0061] The results of the experiments also show that even after water penetration (saturating the column with water vapor) between 1% and 10% CO2 concentration, humidity has a minimal impact on the CO2 capture ability of KAUST-7MOF, indicating that the CO2 capture performance of KAUST-7 is maintained under NGCC waste conditions (e.g., 4% CO2 humid gas).

[0062] As exemplified by the above experiments, the present method provides significant CO2 capture ability for humid gas streams. Therefore, the present method is effective for capturing CO2 from NGCC waste streams, which results in positive environmental impacts. Specifically, NGCC is more efficient and environmentally friendly than traditional coal-based power plants and may replace many coal-based power plants in the near future. Therefore, technologies for capturing CO2 from NGCC facilities are needed. Prior to the present method, conventional methods and materials have not been able to reliably and economically capture CO2 from NGCC waste gases. However, as shown in the present application, the present method using KAUST-7MOF exhibits excellent CO2 capture properties for NGCC conditions and even oxygen stability at high temperatures.

[0063] It should be understood that the same numbers in the drawings represent the same elements (components) in several drawings, and not all embodiments or arrangements require all the components (assemblies) and / or steps described and illustrated in the drawings. Further, the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It will be further understood that the terms "comprises", "comprising", or "has", "containing", "involving" and variations thereof as used herein, specify the presence of the stated feature, integer, step, operation, element (component) and / or component, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements (components), components and / or groups thereof.

[0064] It should be noted that the use of ordinal terms such as "first", "second", "third", etc. in a claim to modify the claim element itself does not mean any precedence, priority or order of one claim element relative to another or in a temporal order of performing the acts of the method, but is only used as a label to distinguish one claim element having a particular name from another element having the same name (but using the said ordinal term) to distinguish the claim elements.

[0065] It is noted that the above figures and examples are not intended to limit the scope of the present disclosure to a single embodiment, since other embodiments are possible by interchanging some or all of the elements (components) described or shown. Also, in cases where certain elements (components) of the present disclosure can be implemented, in part or in whole, using known components, only those parts of such known components that are necessary to understand the present disclosure are described, and detailed descriptions of other parts of such known components are omitted so as not to obscure the present disclosure. In this specification, unless explicitly stated otherwise herein, an embodiment showing a single component does not necessarily limit other embodiments to include a plurality of the same components, and vice versa. Also, the applicant does not intend to ascribe any uncommon or special meaning to any term in the specification or claims, unless explicitly so set forth. Further, the present disclosure covers current and future known equivalents of the known components mentioned herein by way of illustration.

[0066] The foregoing description of the specific embodiments will so fully disclose the general nature of the present disclosure that others can, by applying knowledge within the skill of the relevant art, readily modify and / or adapt such specific embodiments for various applications without undue experimentation, without departing from the general concept of the present disclosure. Accordingly, such adaptations and modifications are intended to fall within the meaning and scope of the equivalents of the disclosed embodiments. It should be understood that the language or terminology herein is for the purpose of description and not of limitation, such that the terminology or wording of this specification will be interpreted by those skilled in the art in light of the teachings and guidance presented herein, in conjunction with the knowledge of those skilled in the relevant art. It should be understood that the dimensions discussed or shown are of the figures of one example and other dimensions may be used without departing from the present disclosure.

[0067] The above subject matter is provided by way of illustration only and should not be construed as limiting. Various modifications and changes can be made to the subject matter described herein without following the example embodiments and applications shown and described, and without departing from the true spirit and scope of the invention covered by the present disclosure, which is defined by the set of statements in the appended claims and the equivalent structures and functions or steps thereto.

Claims

1. A method for capturing CO2 from a humid natural gas combined cycle (NGCC) waste stream, comprising: contacting the humid NGCC waste stream with a metal-organic framework (MOF) material KAUST-7, wherein the humid NGCC waste stream contains approximately 1-5% CO2 and approximately 10-13% O2; and capturing CO2 from the humid NGCC waste stream with the MOF material KAUST-7 to produce a CO2-enriched gas stream containing approximately 10-30% CO2, wherein the relative humidity of the humid NGCC waste stream is approximately 45-75% at 20-85 °C.

2. The method according to claim 1, wherein the relative humidity of the humid NGCC waste stream is approximately 50-70% at 20-85 °C.

3. The method according to claim 1, wherein the relative humidity of the humid NGCC waste stream is approximately 55-65% at 20-85 °C.

4. The method according to claim 1, wherein the balance of the humid NGCC waste stream is N2.

5. The method according to claim 1, wherein CO2 is captured with the MOF material KAUST-7 at a temperature in the range of approximately 20 °C to 85 °C and a pressure in the range of approximately 1 bar to 5 bar.

6. The method according to claim 1, wherein the MOF material KAUST-7 is in the form of pellets, laminates or other structured forms.

7. The method according to claim 1, wherein the MOF material KAUST-7 is pretreated at a temperature in the range of approximately 60 °C to 150 °C under dynamic vacuum or dry inert gas to remove any previously adsorbed molecules.

8. The method according to claim 1, wherein the MOF material KAUST-7 contains an organic binder or an inorganic binder.

9. A method for capturing CO2 from a humid air stream, comprising: contacting the humid air stream with a metal-organic framework (MOF) material KAUST-7, wherein the humid air stream contains approximately 400-1000 ppm CO2 and approximately 20% to 25% O2; and capturing CO2 from the humid air stream with the MOF material KAUST-7 to produce a CO2-enriched gas stream containing approximately 1-30% CO2, wherein the relative humidity of the humid air stream is approximately 5-75% at 0-55 °C.

10. The method according to claim 9, wherein the humid air stream contains approximately 400-800 ppm CO2.

11. The method according to claim 9, wherein the relative humidity of the humid air stream is approximately 50-70% at 0-55 °C.

12. The method according to claim 9, wherein the relative humidity of the humid air stream is approximately 55-65% at 0-55 °C.

13. The method according to claim 9, wherein the balance of the humid air stream is N2 and O2.

14. The method according to claim 9, wherein CO2 is captured with the MOF material KAUST-7 at a temperature in the range of about 0 °C to 55 °C and a pressure in the range of about 1 bar to 5 bar.

15. The method according to claim 9, wherein the MOF material KAUST-7 is in the form of pellets, laminates or other structured forms.

16. The method according to claim 9, wherein the MOF material KAUST-7 is pretreated at a temperature in the range of about 60 °C to 150 °C under dynamic vacuum or dry inert gas to remove any previously adsorbed molecules.

17. The method according to claim 9, wherein the MOF material KAUST-7 contains an organic binder or an inorganic binder.

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