Long-term stable carbon dioxide absorbent as well as preparation method and application thereof

Abstract

The invention relates to a long-term stable carbon dioxide absorbent and a preparation method and application thereof, preparation raw materials of the carbon dioxide absorbent comprise a quaternary ammonium salt hydrogen bond acceptor, an amine compound, an alcohol hydrogen bond donor and a reinforcing agent, and the reinforcing agent comprises sorbitol, boric acid or nano silicon dioxide. The carbon dioxide absorbent disclosed by the invention not only has excellent absorption and desorption effects, but also is creatively added with the reinforcing agent. By adding the reinforcing agent, the long-term operation stability of the absorbent under an oxygen-containing condition can be remarkably improved on the premise that the original excellent CO2 absorption and desorption performance is not influenced basically, and oxidative degradation of amine components is effectively inhibited. The composition is simple to prepare and controllable in cost, and is suitable for efficiently and stably capturing CO2 from gas mixtures such as industrial flue gas.

Description

Technical Field

[0001] The invention belongs to the field of chemical engineering and environmental technology, and relates to a long-term stable carbon dioxide absorbent and a preparation method and application thereof. Background Art

[0002] Global climate change is a serious challenge facing humanity today, primarily driven by the dramatic increase in atmospheric concentrations of greenhouse gases such as carbon dioxide. Carbon capture, utilization, and storage (CCUS) technology is a key approach to addressing climate change and achieving carbon neutrality. Among various CO2 capture technologies, post-combustion capture (CCUS) based on chemical absorption has attracted widespread attention due to its relative maturity and ease of retrofitting into existing industrial facilities.

[0003] Currently, the most commonly used chemical absorbent in industry is an aqueous solution of an alcoholamine, such as a 30 wt% aqueous solution of monoethanolamine (MEA). However, conventional MEA solutions have numerous drawbacks, including high energy consumption during regeneration, solvent loss due to volatilization, environmental impact, equipment corrosion, and susceptibility to oxidative degradation in oxygen-containing flue gases (industrial flue gases typically contain 3-15% O₂). Oxidative degradation not only reduces CO₂ absorption performance and increases solvent replenishment costs, but also generates heat-stable salts and corrosive byproducts, impacting the long-term stability of the device.

[0004] In recent years, deep eutectic solvents (DESs), a novel green solvent platform, have shown great potential in CO2 capture. DESs are typically formed by hydrogen bonding between a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD). They offer advantages such as extremely low vapor pressure, flexible design, simple preparation, relatively low cost, and generally environmental friendliness. However, even these basic DES systems, which offer excellent performance, still face challenges in improving their oxidative stability under oxygen-containing conditions that simulate long-term operation.

[0005] Therefore, there is an urgent need in this field to develop a new type of CO2 absorbent that can have significantly enhanced antioxidant stability while maintaining high absorption capacity, high regeneration efficiency and low energy consumption potential to meet the needs of long-term stable operation of the industry. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention aims to provide a long-term stable carbon dioxide absorbent, its preparation method, and its application. Specifically, the present invention aims to provide a novel amine-based deep eutectic solvent carbon dioxide absorbent composition. By incorporating a specific oxidative stability-enhancing additive, this composition significantly improves its resistance to oxidative degradation and extends its service life, without substantially compromising its already excellent CO₂ absorption and desorption performance. The present invention also provides a preparation method for this absorbent composition and its application in CO₂ capture.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a long-term stable carbon dioxide absorbent, wherein the raw materials for preparing the carbon dioxide absorbent include a quaternary ammonium salt hydrogen bond acceptor, an amine compound, an alcohol hydrogen bond donor and an enhancer, wherein the enhancer includes sorbitol, boric acid or nano-silica.

[0009] The main purpose of the present invention is to solve the technical problem that the long-term stability of high-performance amine-functionalized deep eutectic solvents (such as ChCl / MEA / PG systems) under oxygen-containing conditions is still insufficient. Specifically, the present invention introduces amine compounds with high CO2 reactivity (such as MEA) into the DES system to construct a DES with both physical and chemical absorption capabilities, which is expected to overcome some of the shortcomings of traditional amine aqueous solutions. The ternary DES system composed of quaternary ammonium salts HBA (such as choline chloride, ChCl), primary amine compounds (such as monoethanolamine, MEA) and diols HBD (such as 1,2-propylene glycol, PG) exhibits excellent CO2 capture performance, which far exceeds the CO2 absorption capacity of traditional MEA aqueous solutions and has high regeneration efficiency. The addition of an enhancer can significantly improve the long-term stability of the absorbent and significantly inhibit the oxidative degradation of the MEA component under oxygen-containing conditions. This improved stability is achieved without substantially changing the original excellent CO2 absorption capacity and desorption performance. This suggests that the additive's primary function in the specific DES system of the present invention is not as an additional absorbent or absorption / desorption accelerator, but rather through unique synergistic interactions with the DES system, selectively enhancing the antioxidant capacity of MEA through mechanisms such as modulation of the microscopic hydrogen bond network (sorbitol), dynamic chemical interactions or network regulation (boric acid), or physical shielding / interfacial anchoring (nanosilica). This "functional decoupling" and selective stabilization effect is difficult to foresee in prior art.

[0010] The long-term stability means that the carbon dioxide absorbent prepared by the present invention has no significant change in its carbon dioxide absorption rate when stored at around 55° C. for 9 days.

[0011] Preferably, the molar ratio of the quaternary ammonium salt hydrogen bond acceptor, the amine compound, and the alcohol hydrogen bond donor is (0.2-4):(2-8):(2-6).

[0012] The specific point values ​​in (0.2-4) can be selected from 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, etc. The specific point values ​​in (2-8) can be selected from 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, etc. The specific point values ​​in (2-6) can be selected from 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, etc. Other specific point values ​​within the above numerical range can be selected, so they will not be listed here one by one.

[0013] Preferably, the molar ratio of sorbitol to quaternary ammonium salt hydrogen bond acceptor is (0.01-1):1.

[0014] The specific point values ​​in (0.01-1) can be selected as 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc. Other specific point values ​​within the above numerical range can be selected, and they will not be listed here one by one.

[0015] Preferably, the molar ratio of the boric acid to the quaternary ammonium salt hydrogen bond acceptor is (0.01-1):1.

[0016] The specific point values ​​in (0.01-1) can be selected as 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc. Other specific point values ​​within the above numerical range can be selected, and they will not be listed here one by one.

[0017] Preferably, the mass of the nano-silica is 0.1-5% of the total mass of the quaternary ammonium salt hydrogen bond acceptor, amine and alcohol hydrogen bond donor, for example, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. Other specific values ​​within the above numerical range can be selected, and they will not be repeated here.

[0018] Preferably, the quaternary ammonium salt hydrogen bond acceptor comprises choline chloride.

[0019] Preferably, the amine compound includes monoethanolamine.

[0020] Preferably, the alcohol hydrogen bond donor includes at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, diethylene glycol or triethylene glycol, or a combination thereof.

[0021] In a second aspect, the present invention provides a method for preparing the long-term stable carbon dioxide absorbent according to the first aspect of the present invention, the preparation method comprising: physically mixing a quaternary ammonium salt hydrogen bond acceptor, an amine compound, an alcohol hydrogen bond donor, and an enhancer to obtain the product.

[0022] The mixing is carried out until a uniform transparent liquid or a stable dispersion system is formed.

[0023] Preferably, the temperature of the physical mixing is 20-100°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc. Other specific point values ​​within the above numerical range can be selected and will not be described here one by one.

[0024] In a third aspect, the present invention provides use of the long-term stable carbon dioxide absorbent according to the first aspect of the present invention in capturing CO2 from a mixture.

[0025] Preferably, the mixture comprises industrial waste gas, more specifically, flue gas from a coal-fired power plant, flue gas from a gas-fired power plant, kiln gas from a cement plant, blast furnace gas from a steel plant, natural gas, synthesis gas or biogas.

[0026] The carbon dioxide absorbent prepared by the present invention can be regenerated after use by heating (such as raising the temperature to 80-120° C.) and / or reducing the pressure to release enriched CO2, which can be recycled.

[0027] Preferably, the use specifically comprises: mixing the long-term stable carbon dioxide absorbent with the mixture.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The CO2 absorbent prepared by the present invention has strong oxidative stability. By introducing a specially selected enhancer (sorbitol, boric acid or nano-silica) into an optimized DES system that already has excellent performance, the oxidative degradation of the MEA components under oxygen-containing conditions can be significantly inhibited, and the attenuation rate of the absorption performance during long-term operation can be greatly reduced. This stability improvement effect is significant and unexpected. More importantly, this stability improvement is achieved without substantially changing the original excellent CO2 absorption capacity and desorption performance. This shows that the main role of the enhancer in the specific DES system of the present invention is not as an additional absorbent or absorption / desorption promoter, but through a unique synergistic effect with the DES system, such as through the regulation of the microscopic hydrogen bond network (sorbitol), dynamic chemical action or network regulation (boric acid), or providing physical shielding / interface anchoring (nano-silica), etc., to selectively enhance the antioxidant capacity of MEA. This "functional decoupling" and selective stabilization effect are difficult to foresee in the prior art.

[0030] (2) The absorbent composition of the present invention fully retains the high CO2 absorption capacity, good absorption kinetics, high regeneration efficiency (e.g., 90-92%) and cyclic stability of the DES system, as well as the low theoretical regeneration energy consumption potential (absorption enthalpy of about -45 kJ / mol).

[0031] (3) The absorbent composition of the present invention has a simple preparation method. The selected additives (sorbitol, boric acid, and fumed silica) are all common or readily available industrial raw materials with relatively low costs, which makes the absorbent of the present invention economical and environmentally friendly. The basic DES components (ChCl, PG) and some additives (sorbitol) have good biodegradability and low toxicity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the CO2 absorption kinetics curve of DES1 of the present invention.

[0033] Figure 2 This is the thermogravimetric analysis diagram of DES1 of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0035] The sources of the functional ingredients contained in the products involved in the following examples and comparative examples are as follows (only the functional ingredients are reflected, and the necessary auxiliary ingredients contained in other commercially available raw materials are not repeated):

[0036] Hydrophilic fumed nanosilica (Fumed Silica, brand 200).

[0037] CO2 (purity ≥ 99.9%) and N2 (purity ≥ 99.9%) gas cylinders.

[0038] The specific embodiments of the present invention use 1,2-propylene glycol as a hydrogen bond donor for illustration, but those skilled in the art will appreciate that other diols or polyols as described in the claims, such as ethylene glycol, glycerol, etc., can also be used to constitute the deep eutectic solvent system of the present invention, and similar beneficial effects are expected to be achieved.

[0039] CO2 absorption capacity test method:

[0040] Place 10g of absorbent in a precisely weighed reaction flask with a gas inlet and outlet and a magnetic stirrer, and place it in a constant temperature water bath at 35±0.1°C. Pass a mixed gas of 15% CO2 / 85% N2 (v / v) at a flow rate of 100mL / min while stirring at 500rpm. Regularly weigh the total mass of the reaction flask using a balance (accuracy 0.01g) until the mass changes by less than 0.01g within 30 minutes, which is considered to have reached absorption saturation. Calculate the CO2 absorption capacity at this time and record it as the saturated CO2 absorption capacity.

[0041]

[0042] Regeneration performance and cycle stability test methods:

[0043] After saturation (15% CO2, 35°C), place the absorbent in an oil bath at 100±1°C and purge with N2 at a flow rate of 100 mL / min for desorption while stirring until the mass no longer decreases significantly (approximately 2-3 hours). This completes one absorption-desorption cycle. Repeat the absorption-desorption cycle. Record the saturated absorption capacity at the end of each cycle and calculate the desorption efficiency.

[0044]

[0045] Oxidation stability test method:

[0046] Approximately 20 g of absorbent was placed in a beaker and maintained at 55°C in air using a hot plate for 216 hours (9 days). After aging, the absorbent sample was removed and its saturated CO2 absorption capacity was re-measured at 35°C under 15% CO2 / 85% N2 conditions.

[0047] Preparation Example 1

[0048] This preparation example provides a carbon dioxide absorbent, and the preparation method of the carbon dioxide absorbent includes:

[0049] ChCl (8.38 g, 0.06 mol), MEA (22.00 g, 0.36 mol) and PG (13.70 g, 0.18 mol) were weighed in a molar ratio of 1:6:3 and added to a 100 mL three-necked flask with a magnetic rod. The mixture was heated and stirred in an oil bath at 60°C for 1 hour to form a uniform, transparent, colorless liquid. After cooling to room temperature, the obtained product was obtained and recorded as DES1 absorbent.

[0050] At 35°C and 100% CO2, the saturated CO2 absorption capacity of DES1 absorbent was measured to be 16.43 wt%.

[0051] Preparation Example 2

[0052] This preparation example provides a carbon dioxide absorbent, and the preparation method of the carbon dioxide absorbent includes:

[0053] ChCl (8.38 g, 0.06 mol), MEA (22.00 g, 0.36 mol), and PG (18.27 g, 0.24 mol) were weighed in a molar ratio of 1:6:4 and added to a 100 mL three-necked flask with a magnetic rod. The mixture was heated and stirred in a 60°C oil bath for about 1 hour to form a uniform, transparent, colorless liquid. After cooling to room temperature, the obtained product was recorded as DES1a absorbent.

[0054] At 35°C and 100% CO2, the saturated CO2 absorption capacity of DES1a absorbent was measured to be 15.24 wt%.

[0055] Preparation Example 3

[0056] This preparation example provides a carbon dioxide absorbent, and the preparation method of the carbon dioxide absorbent includes:

[0057] ChCl (4.19 g, 0.03 mol), MEA (22.00 g, 0.36 mol), and PG (18.27 g, 0.24 mol) were weighed in a molar ratio of 0.5:6:4 and added to a 100 mL three-necked flask with a magnetic rod. The mixture was heated and stirred in a 60°C oil bath for about 1 hour to form a uniform, transparent, colorless liquid. After cooling to room temperature, the obtained product was recorded as DES1b absorbent.

[0058] At 35°C and 100% CO2, the saturated CO2 absorption capacity of DES1b absorbent was measured to be 15.41 wt%.

[0059] Preparation Example 4

[0060] This preparation example provides a carbon dioxide absorbent, and the preparation method of the carbon dioxide absorbent includes:

[0061] ChCl (8.38 g, 0.06 mol), MEA (22.00 g, 0.36 mol) and PG (9.14 g, 0.12 mol) were weighed in a molar ratio of 1:6:2 and added to a 100 mL three-necked flask with a magnetic rod. The mixture was heated and stirred in a 60°C oil bath for about 1 hour to form a uniform, transparent, colorless liquid. After cooling to room temperature, the obtained product was recorded as DES1c absorbent.

[0062] At 35°C and 100% CO2, the saturated CO2 absorption capacity of the DES1c absorbent was measured to be 16.91wt%, but the solution viscosity was too high after saturation, which was not conducive to pipeline transportation.

[0063] Test 1

[0064] Taking into account factors such as CO2 absorption capacity and system viscosity, the ChCl:MEA:PG system with a molar ratio of 1:6:3 showed a good balance in various performance indicators and was therefore selected as the basic formula for subsequent research.

[0065] Further testing of the DES1 absorbent

[0066] 1. CO2 absorption capacity: 10 wt% deionized water was pre-added to the absorbent DES1, and then tested at 35°C and 15% CO2 / 85% N2. The saturated CO2 absorption capacity was still 16.43 wt% (excluding the weight of water).

[0067] 2. CO2 absorption kinetics: Under the conditions of 35℃, 15% CO2 / 85% N2 (150mL / min), the absorption amount was recorded over time by timed weighing method. The results showed that the absorption rate was fast, reaching more than 95% of the saturated absorption capacity in about 60 minutes. Comparison of the kinetic curves at 25℃ and 45℃ ( Figure 1 ), 35℃ is the optimal operating temperature for taking both absorption rate and equilibrium capacity into consideration.

[0068] 3. Regeneration Performance and Cyclic Stability: After saturation (15% CO2, 35°C), place the absorbent DES1 in an oil bath at 100±1°C. Purge and desorb the absorbent with N2 at a flow rate of 100 mL / min while stirring until the mass no longer significantly decreases (approximately 2-3 hours). This completes one absorption-desorption cycle. Repeat this cycle five times. Record the saturated absorption capacity at the end of each cycle and calculate the desorption efficiency for that cycle.

[0069] 1st cycle: absorption capacity 16.43wt%, desorption efficiency 89.25%

[0070] Second cycle: absorption capacity 16.30 wt%, desorption efficiency 89.90%

[0071] 3rd cycle: absorption capacity 16.51wt%, desorption efficiency 90.00%

[0072] 4th cycle: absorption capacity 16.19wt%, desorption efficiency 91.26%

[0073] 5th cycle: absorption capacity 16.51wt%, desorption efficiency 92.38%

[0074] The results show that the absorbent DES1 has excellent cyclic stability (the absorption capacity is basically stable at around 16.4% after 5 cycles) and high regeneration efficiency (average of about 90.56%).

[0075] 4. Thermal stability (TGA): Using a thermogravimetric analyzer, heat from 30°C to 400°C at a heating rate of 10°C / min in a N2 atmosphere (flow rate 50 mL / min). The results are as follows Figure 2As shown, the sample begins to experience slight weight loss at approximately 80°C, with the main weight loss occurring between approximately 100°C and 180°C, corresponding to the volatilization / initial decomposition of MEA and PG. The maximum weight loss rate peak (DTG peak) is located at approximately 128°C. A second distinct DTG peak appears at approximately 312°C, corresponding to the decomposition of ChCl. This indicates that the absorbent has good thermal stability within the typical absorption (35°C) and desorption (100-120°C) temperature ranges.

[0076] 5. Absorption enthalpy change (ΔH): The equilibrium absorption capacity of absorbent DES1 at 15% CO2 partial pressure was measured at 25°C, 35°C, 45°C, and 55°C, and the corresponding reaction equilibrium constant, K, was calculated. A Van't Hoff plot of lnK versus 1 / T was plotted and a linear fit was performed. Based on the slope (-ΔH / R), the absorption enthalpy change, ΔH, was calculated to be approximately -44.97 kJ / mol.

[0077] 6. Oxidative Stability: Approximately 20 g of absorbent DES1 was placed in a beaker and maintained at 55°C in air on a hot plate for 216 hours (9 days). After aging, a sample of the absorbent was removed and its saturated CO2 absorption capacity was re-measured at 35°C under 15% CO2 / 85% N2 conditions. The result was 14.80 wt%. This represents a 10.3% loss in absorption capacity compared to 16.43 wt% before aging.

[0078] Example 1

[0079] This example provides a long-term stable carbon dioxide absorbent. The preparation method of the absorbent comprises: weighing ChCl (8.38 g, 0.06 mol), MEA (22.00 g, 0.36 mol), PG (13.70 g, 0.18 mol), and sorbitol (1.09 g, 0.006 mol) in a molar ratio of 1:6:3:0.1. The mixture is stirred in a 60°C oil bath for approximately 1 hour to form a homogeneous, transparent, colorless liquid, designated absorbent DES2.

[0080] CO2 absorption capacity: At 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity was 16.35 wt%, which was essentially unchanged compared to DES1 (16.43 wt%).

[0081] Regeneration Performance: Two absorption-desorption cycles were performed, with the first absorption capacity reaching 16.35 wt% and the second absorption capacity reaching 16.30 wt%. The first desorption efficiency was 91.5%, and the second was 91.6%. This indicates that the addition of sorbitol did not affect the absorption and regeneration performance.

[0082] Oxidation stability test: After aging, the saturated CO2 absorption capacity was measured to be 15.88 wt%. The absorption capacity loss rate was only 2.9%, which was significantly improved compared to the 10.3% loss rate of DES1.

[0083] Example 2

[0084] This example provides a long-term stable carbon dioxide absorbent. The preparation method of the absorbent includes weighing ChCl (8.38 g, 0.06 mol), MEA (22.00 g, 0.36 mol), PG (13.70 g, 0.18 mol), and sorbitol (3.28 g, 0.018 mol) in a molar ratio of 1:6:3:0.3. The mixture is stirred in a 60°C oil bath for approximately 1 hour to form a homogeneous, transparent, colorless liquid, designated as absorbent DES3.

[0085] CO2 absorption capacity: At 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity was 16.05 wt%, which is slightly lower than that of DES1 but still at a similar level.

[0086] Oxidation stability test: After aging, the saturated CO2 absorption capacity was measured to be 15.50wt%, and the absorption capacity loss rate was only 3.4%. Compared with DES1, the oxidation stability was significantly improved, but it was lower than that of DES2, indicating that increasing the amount of sorbitol will reduce the stability.

[0087] Example 3

[0088] This example provides a long-term stable carbon dioxide absorbent. The preparation method of the absorbent comprises: weighing ChCl (8.38 g, 0.06 mol), MEA (22.00 g, 0.36 mol), PG (13.70 g, 0.18 mol), and boric acid (0.19 g, 0.003 mol) in a molar ratio of 1:6:3:0.05. The mixture is stirred in a 60°C oil bath for approximately 1 hour to form a homogeneous, transparent, colorless liquid, designated as absorbent DES4.

[0089] CO2 absorption capacity: At 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity was 16.41 wt%, which is basically the same as that of DES1.

[0090] Regeneration Performance: After two absorption-desorption cycles, the absorption capacity in the first cycle was 16.41 wt%, and the second cycle was 16.38 wt%. The desorption efficiency in the first cycle was 92.0%, indicating that the absorption and regeneration performance were not affected and even slightly improved.

[0091] Oxidation stability test: After aging, the saturated CO2 absorption capacity was measured to be 15.95wt%, with an absorption capacity loss rate of only 2.7%. Compared with DES1, the oxidation stability is significantly improved.

[0092] Example 4

[0093] This example provides a long-term stable carbon dioxide absorbent. The preparation method of the absorbent comprises: weighing ChCl (8.38 g, 0.06 mol), MEA (22.00 g, 0.36 mol), PG (13.70 g, 0.18 mol), and boric acid (0.74 g, 0.012 mol) in a molar ratio of 1:6:3:0.2. The mixture is stirred in a 60°C oil bath for approximately 1 hour to form a homogeneous, transparent, colorless liquid, designated as absorbent DES5.

[0094] CO2 absorption capacity: At 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity was 16.28 wt%, which is basically the same as that of DES1.

[0095] Oxidative stability testing: After aging, the saturated CO2 absorption capacity was measured to be 15.84 wt%. The absorption capacity loss was only 2.7%. Compared to DES1, the oxidative stability was significantly improved and comparable to DES4.

[0096] Example 5

[0097] This example provides a long-term stable carbon dioxide absorbent. The preparation method of the absorbent comprises: stirring 73.44 g of DES1 and 0.74 g of hydrophilic fumed nanosilica (1 wt% of the mass of DES1) at 8000 rpm for 15 minutes at room temperature to form a uniform and stable translucent dispersion system, which is recorded as absorbent DES6.

[0098] CO2 absorption capacity: At 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity was 16.33 wt%, which was essentially unchanged compared to DES1.

[0099] Regeneration Performance: After two absorption-desorption cycles, the absorption capacity in the first cycle was 16.33 wt%, and the absorption capacity in the second cycle was 16.34 wt%. The desorption efficiency in the first cycle was 91.1%, indicating that the absorption and regeneration performance were not affected.

[0100] Oxidation stability test: After aging, the saturated CO2 absorption capacity was measured to be 15.56 wt%. The absorption capacity loss rate was only 4.7%. Compared with DES1, the oxidation stability was significantly improved.

[0101] Example 6

[0102] This example provides a long-term stable carbon dioxide absorber. The preparation method of the absorber comprises: stirring 73.44 g of DES1 and 2.2 g of hydrophilic fumed nano-silica (3 wt% of the mass of DES1) at 8000 rpm for 15 minutes at room temperature to form a uniform and stable translucent dispersion system, which is labeled as absorber DES7.

[0103] CO2 absorption capacity: At 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity was 16.22 wt%, which was essentially unchanged compared to DES1.

[0104] Oxidative stability testing: After aging, the saturated CO2 absorption capacity was measured to be 15.44 wt%. The absorption capacity loss was 4.8%. Compared to DES1, oxidative stability was still significantly improved, but the effect was not further enhanced compared to the 1 wt% addition.

[0105] Comparative Example 1

[0106] This comparative example provides a CO2 absorption liquid, and the preparation method of the absorption liquid comprises:

[0107] 30.0 g of MEA (analytical grade) was dissolved in 70.0 g of deionized water, mixed well, and labeled as absorbent Comp1.

[0108] CO2 absorption capacity: Under the conditions of 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity of absorbent Comp1 was measured to be 10.31 wt%.

[0109] Oxidation stability test: After aging, the CO2 absorption capacity was measured again (35°C, 15% CO2 / 85% N2), and the result was 9.07 wt%. The calculated absorption capacity loss rate was 12%.

[0110] Comparative Example 2

[0111] This comparative example provides a CO2 absorption liquid, and the preparation method of the absorption liquid comprises:

[0112] Dissolve 30.0 g of MEA (analytical grade) in 70.0 g of deionized water and mix thoroughly to obtain 100.0 g of MEA aqueous solution. Add 1.0 g of sorbitol (equivalent to 1 wt% of the total weight of the MEA aqueous solution) to the MEA aqueous solution. Stir thoroughly until the sorbitol is completely dissolved to obtain absorbent Comp2.

[0113] CO2 absorption capacity: At 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity of absorbent Comp2 was 10.22 wt%, which was essentially unchanged compared to a 30 wt% MEA aqueous solution without sorbitol (Comparative Example 1).

[0114] Oxidation stability test: After aging, the CO2 absorption capacity was measured again (35°C, 15% CO2 / 85% N2), and the result was 9.14 wt%, with an absorption capacity loss rate of 11.3%.

[0115] Comparative conclusion: Compared with the 30 wt % MEA aqueous solution without additives (Comparative Example 1), the oxidation stability of the MEA aqueous solution is almost not improved after adding sorbitol.

[0116] Comparative Example 3

[0117] This comparative example provides a CO2 absorption liquid, and the preparation method of the absorption liquid comprises:

[0118] Dissolve 30.0 g of MEA (analytical grade) in 70.0 g of deionized water and mix thoroughly to obtain 100.0 g of MEA aqueous solution. Add 0.5 g of boric acid (equivalent to 0.5 wt% of the total weight of the MEA aqueous solution) to the MEA aqueous solution. Stir thoroughly until the boric acid is completely dissolved to obtain absorbent Comp3.

[0119] CO2 absorption capacity: Under the conditions of 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity of absorbent Comp3 was measured to be 10.39 wt %, which was substantially unchanged compared with Comparative Example 1.

[0120] Oxidation stability test: After aging, the CO2 absorption capacity was measured again, and the result was 9.00 wt%. The calculated absorption capacity loss rate was 13.4%.

[0121] Comparative conclusion: Compared with the 30 wt % MEA aqueous solution without additives (Comparative Example 1), the oxidation stability of the MEA aqueous solution was not improved after adding boric acid.

[0122] Comparative Example 4

[0123] This comparative example provides a CO2 absorption liquid, and the preparation method of the absorption liquid comprises:

[0124] 30.0 g of MEA (analytical grade) was dissolved in 70.0 g of deionized water and mixed thoroughly to obtain 100.0 g of MEA aqueous solution. 1.0 g of hydrophilic fumed nanosilica (equivalent to 1 wt% of the total weight of the MEA aqueous solution) was added to the MEA aqueous solution. The mixture was stirred at 8000 rpm for 15 minutes at room temperature until a uniform and stable dispersion was formed, thereby obtaining absorbent Comp4.

[0125] CO2 absorption capacity: Under the conditions of 35°C and 15% CO2 / 85% N2, the initial saturated CO2 absorption capacity of absorbent Comp4 was measured to be 10.14 wt %, which was substantially unchanged compared with Comparative Example 1.

[0126] Oxidation stability test: After aging, the CO2 absorption capacity was measured again and found to be 8.86 wt %. The absorption capacity loss rate was calculated to be 12.63%.

[0127] Comparative conclusion: Compared with the 30 wt% MEA aqueous solution without additives (Comparative Example 1), the oxidation stability of the MEA aqueous solution was not improved after the addition of nano-silica.

[0128] In summary, the carbon dioxide absorbent prepared in this application is based on a deep eutectic solvent, comprising a specific enhancer and an amine functionalized absorbent, and its absorption effect on carbon dioxide is better than the alcoholamine aqueous solution commonly used in industry, but without the addition of an enhancer, its stability is poor. Continuing for 9 days at 55 ° C will cause its absorption capacity to lose about 10%. After adding an enhancer thereto, after treatment under the same conditions, its capacity loss is less than 5%, proving that the addition of the enhancer greatly improves the stabilizing effect. The enhancer added in this application has this effect of improving stability in a specific system, and it does not have the enhancing effect as described in this application for traditional alcoholamine aqueous solutions.

[0129] The applicant states that while the above-described embodiments illustrate a long-term, stable carbon dioxide absorbent, its preparation method, and its application, the present invention is not limited to these embodiments. This does not necessarily mean that the present invention must rely on these embodiments for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for raw materials in the present invention, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

[0130] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0131] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A long-term stable carbon dioxide absorbent, characterized in that: The raw materials for preparing the carbon dioxide absorbent include quaternary ammonium salt hydrogen bond acceptors, amine compounds, alcohol hydrogen bond donors and enhancers. The enhancer includes sorbitol, boric acid or nano silicon dioxide.

2. The long-term stable carbon dioxide absorbent according to claim 1, characterized in that The molar ratio of the quaternary ammonium salt hydrogen bond acceptor, the amine compound and the alcohol hydrogen bond donor is (0.2-4):(2-8):(2-6).

3. The long-term stable carbon dioxide absorber according to claim 1 or 2, characterized in that The molar ratio of the sorbitol to the quaternary ammonium salt hydrogen bond acceptor is (0.01-1):

1.

4. The long-term stable carbon dioxide absorber according to claim 1 or 2, characterized in that The molar ratio of the boric acid to the quaternary ammonium salt hydrogen bond acceptor is (0.01-1):

1.

5. The long-term stable carbon dioxide absorber according to claim 1 or 2, characterized in that The mass of the nano-silicon dioxide is 0.1-5% of the total mass of the quaternary ammonium salt hydrogen bond acceptor, the amine compound and the alcohol hydrogen bond donor.

6. The long-term stable carbon dioxide absorber according to any one of claims 1 to 5, characterized in that The quaternary ammonium salt hydrogen bond acceptor includes choline chloride; Preferably, the amine compound comprises monoethanolamine; Preferably, the alcohol hydrogen bond donor includes at least one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, diethylene glycol or triethylene glycol, or a combination thereof.

7. The method for preparing a long-term stable carbon dioxide absorbent according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: physically mixing a quaternary ammonium salt hydrogen bond acceptor, an amine compound, an alcohol hydrogen bond donor and an enhancer to obtain the product.

8. The method for preparing a long-term stable carbon dioxide absorbent according to claim 7, characterized in that: The temperature of the physical mixing is 20-100°C.

9. Use of the long-term stable carbon dioxide absorbent according to any one of claims 1 to 6 in capturing CO2 from a mixture.

10. The use according to claim 9, characterized in that The application specifically includes: mixing the long-term stable carbon dioxide absorbent with the mixture.

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