Carbon dioxide capture adsorbent

Abstract

The present invention provides (A) a polyalkyleneimine or an alkoxylated polyalkyleneimine; and (B) an inorganic solid support for the polyalkyleneimine or alkoxylated polyalkyleneimine (A) a sorbent for absorbing carbon dioxide from a gas or gas mixture, comprising: wherein the alkoxylated polyalkyleneimine (A) is disposed on an inorganic solid support (B); The adsorbent contains more than 2% by weight of water, based on the total weight of the adsorbent. The invention also provides methods for preparing such adsorbents, as well as methods for using the adsorbents to capture carbon dioxide from gas mixtures such as air.

Description

[Technical Field]

[0001] The present invention relates to a solid adsorbent for capturing carbon dioxide. The present invention is useful for capturing carbon dioxide from a mixture of gases (containing carbon dioxide), such as waste gases (e.g., from a combustion process) or air. The present invention provides an adsorbent comprising: (A) a polyalkyleneimine or an alkoxylated polyalkyleneimine; and (B) an inorganic solid support for the polyalkyleneimine or alkoxylated polyalkyleneimine. [Background technology]

[0002] Rising atmospheric concentrations of greenhouse gases have attracted growing global attention due to their predicted impact on climate change, particularly with regard to rising carbon dioxide concentrations. It is widely recognized that even current atmospheric carbon dioxide concentrations are causing dramatic environmental changes, including droughts, floods, and ecosystem disruption around the world. If carbon dioxide concentrations continue to rise, it is predicted that average atmospheric and ocean temperatures will rise significantly, accelerating the melting of polar and glacial ice, and leading to rising sea levels and the inevitable inundation of low-lying areas. Rising atmospheric temperatures are also expected to increase the likelihood of powerful cyclonic storms worldwide.

[0003] Many governments are seeking to act through legislation aimed at reducing greenhouse gas emissions, particularly carbon dioxide, and ultimately limiting global warming. Many countries have adopted the Paris Agreement, a legally binding international treaty on climate change, whose goal is to limit global warming to well below 2°C, and preferably 1.5°C, above pre-industrial levels.

[0004] In recent years, significant efforts have been made to develop technologies to achieve the goal of reducing carbon dioxide concentrations in the atmosphere and / or from gas emissions. Capturing carbon dioxide at its source is generally considered the most cost-effective approach. Such sources include large-scale carbon-based energy facilities that use fossil fuels, natural gas processing, synthetic fuel plants, carbon-intensive industries such as steel and cement manufacturing, and hydrogen production plants.

[0005] One of the major carbon capture technologies is carbon dioxide absorption or sequestration. It is known to use certain amine compounds for carbon dioxide absorption. Representative amines used for this purpose include alkanolamines, such as monoethanolamine, diethanolamine, diisopropanolamine, pentaethylenehexamine, tetraethylenepentamine, triethylenetetramine, tetraethylenetetramine, bis(2-hydroxypropyl)amine, N,N'-bis(2-hydroxyethyl)ethylenediamine, alkylamines, methylamines, linear polyethyleneimine, branched polyethyleneimine, dimethylamine, diethylamine, methyldiethanolamine, methylethanolamine, polyethylenepolyamines, diethylenetriamine, and N,N'-bis-(3-aminopropyl)ethylenediamine.

[0006] U.S. Patent No. 7,795,175 B2 describes a supported amine adsorbent comprising an amine or an amine / polyol composition deposited on a nanostructured support, such as nanosilica. The adsorbent is said to be structurally intact, providing high selectivity and enhancing its ability to efficiently capture carbon dioxide from gas mixtures, including air. The adsorbent is regenerative, capable of multiple absorption-desorption cycles. The nanostructured support can have a primary particle size of less than about 100 nm and can be fumed or precipitated oxides, calcium silicate, carbon nanotubes, or mixtures thereof. The amine can be a primary, secondary, or tertiary amine, or an alkanolamine, aromatic amine, mixed amine, or combinations thereof. In one example, the amine is present in an amount of about 25% to 75% by weight of the adsorbent. The polyol can be selected from, for example, glycerol, oligomers of ethylene, polyethylene glycol, polyethylene oxide, and ethers, modifications, and mixtures thereof. These can be provided in an amount of about 25% by weight or less of the adsorbent.

[0007] U.S. Patent No. 9,084,960 B2 discloses a method for reducing the CO2 content of a gas mixture by contacting the gaseous effluent to be treated with an absorbent containing a CO2 capture agent impregnated on a substrate made of a solid composite material (M) comprising a polymer (P) and a compound (C) selected from mineral oxides, silicoaluminates, and activated carbon. The CO2 capture agent according to this disclosure may include monoamines (especially secondary amines such as diethanolamine), polyamines, monoguanidines, and polyguanidines, and mixtures of these compounds. The material (M) is said to have an average particle size (D50) of at least 100 μm, more preferably at least 150 μm. However, this average particle size is generally indicated to be 2000 μm or less. The pore volume (Vd1) formed by pores with diameters between 3.6 and 1000 nm is at least 0.2 cm3. 3 / g, preferably at least 0.4 cm 3 / g.

[0008] U.S. Patent No. 9,533,250 B2 discloses an adsorbent for reducing CO2 from indoor air from enclosed spaces. In some embodiments, the adsorbent is said to include a solid support and an amine-based compound supported on the support. The disclosure states that the adsorbent captures at least a portion of the CO2 in the indoor air. The amine-based compound is proposed to include any suitable amine, such as a primary or secondary amine, or a combination thereof. According to this disclosure, the amine-based compound ranges from simple single molecules such as ethanolamine to high molecular weight amine polymers such as polyethyleneimine. Suggested in this specification are any of a number of polyamines, such as monoethanolamine, ethanolamine, methylamine, branched polyethyleneimine, linear polyethyleneimine, diethanolamine, dimethylamine, diethylamine, diisopropanolamine, tetraethylenepentamine, methyldiethanolamine, methylethanolamine, and polyethyleneimine, or combinations thereof. The adsorbent includes a solid support and an amine-based compound supported on the support. The support can include a porous solid material or a particulate solid material. It is also suggested that the carrier comprises clay. It is further suggested that such a carrier can comprise a plurality of particles, such particles having an average diameter size within the range of 0.1 to 10 mm, 0.2 to 3 mm, or 0.3 to 1 mm.

[0009] U.S. Patent No. 11,229,897 B2 discloses carbon dioxide and VOC adsorbents containing a porous support impregnated with an amine compound. These adsorbents are said to include a gas adsorbent material coated on a porous support. The gas adsorbent material includes a polyamine produced using a process that does not contain formaldehyde as a reaction product and / or reactant. The disclosure describes a method for preparing the adsorbent by preparing a reaction solution of a first amine compound and a reactant. The reactant is said to include a carbonate ester compound or a ketone compound. The first amine compound reacts with the reactant to produce a second amine compound. The second amine compound is then impregnated into a porous support to produce the adsorbent. Various porous supports, including clay, are proposed. Other materials proposed include a diverse list of materials, including silica, zeolite, fumed silica, and activated carbon. The porous support is pre-treated for 50 minutes before being impregnated with the second amine compound. 2 It is said to have a surface area of ​​more than 0.2 cm3 / g. 3 / g super 0.8cm 3 / g or less, 0.1cm 3 / g super 3.0cm 3 An embodiment is shown in which the porous carrier is in the form of granules having a diameter in the range of about 0.25 mm to about 5 mm.

[0010] Kim, JY et al., "Laboratory-Scale Continuous Testing of Silica-PEI Adsorbents in a Bubbling Fluidized Bed System," International Journal of Greenhouse Gas Control, 82 (2019), pp. 184-191, describe a large-scale bubbling fluidized bed system (TBS) used to continuously test the CO adsorption performance of a silica-PEI adsorbent containing 40% PEI by mass. The TBS included a bubbling-bed adsorption / desorption reactor, a riser for pneumatic transport of solids from the adsorption reactor to the desorption reactor, and a cyclone for solid-gas separation. The adsorbent was prepared using PEI with a molecular weight of 800 (S.PEI-0.8K). To analyze the CO removal efficiency in the adsorption reactor and the dynamic adsorption capacity of the adsorbent, preliminary tests were conducted for approximately 24 hours under predetermined operating conditions, varying the inlet adsorbent / CO mass ratio in the adsorption system. Subsequently, a 180-hour continuous test was conducted under various experimental conditions, such as water concentration, reaction temperature, solid layer height, reaction gas flow rate, and inlet adsorbent / CO2 mass ratio in an adsorption device using a PEI (S.PEI-5K) absorbent with a molecular weight of 5000. It is said that a CO2 removal efficiency of over 80% and a dynamic adsorption capacity of over 6.0 mass% were achieved.

[0011] Zhang, W. et al., "Post-combustion CO2 Capture Process Simulation for Coal-Fired and Natural Gas-Fired Power Plants Using Polyethyleneimine / Silica Adsorbent," International Journal of Greenhouse Gas Control, 58 (2017), pp. 276-289, first describes the evaluation of the regeneration heat of a polyethyleneimine (PEI) / silica adsorbent-based carbon capture system and its impact on the efficiency penalty of a coal-fired or natural gas-fired power plant. Process simulations were conducted to evaluate the net plant efficiency of specific supercritical pressure 550 MWe pulverized coal (PC) and 555 MWe natural gas combined cycle (NGCC) power plants integrating a conceptually designed capture system using a fluidized bed and PEI / silica adsorbent. The solid adsorbent used in this study was synthesized by impregnating an inorganic mesoporous silica support with 40% PEI by mass. The PEI was highly branched and had a molecular weight of 1800.

[0012] Zhang, W. et al., "Evaluation of the Cycling Performance of Polyethyleneimine / Silica Adsorbent with Steam Regeneration Function Using Simulated NGCC Exhaust Gas and Actual Exhaust Gas from a Gas Boiler in a Bubbling Fluidized Bed Reactor," International Journal of Greenhouse Gas Control, 95 (2020), p. 102975, describes a study on the cycling performance of a kg-scale polyethyleneimine / silica adsorbent in a laboratory-scale bubbling fluidized bed reactor. A high-concentration steam mixture of 80-90% by volume of N2 and CO2 was used as the stripping gas in a typical temperature swing adsorption cycle. The adsorbent used in this study had a BET specific surface area of ​​approximately 250 m2. 2 The inorganic mesoporous silica support, with a pore volume of 1.7 cc / g and an average pore diameter of approximately 20 nm, was impregnated with 40% by mass of polyethyleneimine (PEI). The PEI was highly branched and had a molecular weight of 1800.

[0013] Kim, JY et al., "Performance of Silica-Polyethyleneimine Adsorbents for Post-Combustion CO2 Capture at a 100 kg Scale in a Fluidized Bed Continuous System," Chemical Engineering Journal 407 (2021) p. 127209, described a polyethyleneimine (PEI) / silica adsorbent for post-combustion CO2 capture in a 150-hour continuous test using a 100 kg silica-PEI sample in a fluidized bed continuous system. The CO2 removal efficiency and dynamic adsorption capacity were continuously evaluated by varying many variables. Two types of silica-PEI with different PEI molecular weights were used to prepare silica-PEI adsorbents for CO2 capture performance evaluation.

[0014] Choi, W. et al., Epoxy functionalization of polyethyleneimine for the synthesis of carbon dioxide adsorbents stable in temperature swing adsorption, Nature Communications, 7(1), pp. 1–8, 2016, demonstrated a large work load (2.2 mmol g) in practical temperature swing adsorption processes. -1This paper describes the scalable synthesis of functionalized PEI / silica adsorbents that simultaneously exhibit high thermal conductivity and long-term stability. This paper demonstrates that functionalizing PEI with 1,2-epoxybutane reduces heat absorption during regeneration and enhances carbon dioxide desorption (over 99%) compared to unmodified PEI (76%). Table 1 shows the results for 0.15, 0.37, and 0.54 epoxybutane PEI / SiO2 adsorbents.

[0015] Le, M.U.T. et al., "Preparation and Characterization of PEI-Supported MCM-41 for CO2 Capture," International Journal of Hydrogen Energy 39 (2014), pp. 12340-12346, discloses the preparation of PEI-supported MCM-41 by first preparing the molecular sieve MCM-41 using tetraethoxysilane and cetyltrimethylammonium bromide. Using a wet impregnation method, mesoporous silicate MCM-41 was modified with various weight amounts of polyethyleneimine (PEI) to increase its CO2 adsorption capacity. PEI (MW = 25,000)-impregnated adsorbents were prepared by the wet impregnation method. The desired amount of PEI was dissolved in 6 mL of methanol and stirred for 15 minutes. Then, calcined MCM-41 (0.5 g) was added to the amine-methanol solution, and the slurry mixture was stirred at room temperature for 3 hours. The final product was dried at 80 °C under reduced pressure for 8 hours.

[0016] Lie, K. et al., "Effect of Polyethyleneimine Type and Molecular Weight on the CO2 Capture Performance of PEI Nanosilica Adsorbents," Applied Energy, 136 (2014), 750-755, describes amine-silica adsorbents as an alternative to aqueous amine solutions, traditionally used to capture carbon dioxide (CO2) from flue gases, due to their high thermal stability. In this study, the effects of PEI type (branched or linear) and molecular weight on the CO2 capture performance of PEI-silica adsorbents were investigated. The molecular weight of PEI is known to affect the thermal stability of PEI-silica adsorbents, but for molecular weights of at least 1200 Da, the increased stability was negligible in the temperature range of 25–160 °C. Branched PEI was found to achieve a higher CO2 saturated sorption capacity than linear PEI. Linear PEI was also found to be more stable than branched PEI during CO2 adsorption-desorption cycles. PEI-nanosilica adsorbents were prepared by dissolving PEI in methanol, adding nanosilica, adding more methanol, and drying.

[0017] Li K et al., "Polyethyleneimine-Nanosilica Composite: A Low-Cost, Promising Adsorbent for CO2 Capture," Journal of Materials Chemistry A, 2015, 3, 2166-75, describes a nanosilica-based adsorbent for CO2 capture, synthesized by impregnating nanosilica with polyethyleneimine. This study observed that the impregnation of PEI into nanosilica with pores of 2-40 nm plays an important role in the adsorbent synthesis process. Furthermore, it was revealed that the PEI loading, adsorption temperature, and CO2 partial pressure affect the CO2 adsorption capacity and PEI utilization efficiency. The PEI-nanosilica adsorbent was prepared by dissolving PEI in methanol, adding dried nanosilica, adding more methanol, and then drying.

[0018] Park, S. et al., "Epoxy-functionalized poly(ethyleneamine)-loaded silica / polymer modules for sustainable CO2 capture via rapid thermal swing adsorption," Industrial & Engineering Chemistry Research, 2018, 57, pp. 13923-13931, describes the formation of PAI / SiO2 / 0.37EB-PEI and PAI / SiO2 / PEI. Polyethyleneimine was modified with 1,2-epoxybutane (EB), and EB was added dropwise to PEI dissolved in methanol to form 0.37EB-PEI. PAI / SiO2 was then impregnated with the resulting methanol solution mixture and dried.

[0019] U.S. Patent No. 10,010,861 B2 relates to a carbon dioxide adsorbent comprising a polymeric amine and a porous support on which the polymeric amine is supported. The polymeric amine is said to consist of a polymeric backbone containing nitrogen atoms and branched chains attached to the nitrogen atoms of the polymeric backbone. Each branched chain contains at least one nitrogen atom, and the polymeric amine is modified by substituting at least one nitrogen atom of the polymeric backbone or branched chain with a hydroxyl group-containing carbon chain. The disclosure states that the porous support may be silica, mesoporous silica, heteroelement-doped silica, alumina, heteroelement-doped alumina, activated carbon, or a carbon-based support. Example 1 describes the synthesis of polyethyleneimine modified by partial substitution with butylene oxide. This synthesis involves dissolving polyethyleneimine (Mn=1200, 19 mmol N / g) in methanol. This disclosure reveals that different amounts of butylene oxide were added to a polyethyleneimine / methanol solution to achieve molar ratios of butylene oxide to nitrogen atoms present in the polyethyleneimine of 0.15:1, 0.37:1, and 0.54:1. This disclosure reveals that the solvent was removed by heating the modified polyethyleneimine solution in a vacuum oven. This disclosure further teaches the use of similar modified polyethyleneimine to form modified polyethyleneimine-supported silica. Example 2 discloses the impregnation of fumed silica with the modified polyethyleneimine, and Example 3 discloses the impregnation of borosilicate. In Example 2, the preparation involves adding different amounts of fumed silica, 2.48 g, 3.20 g, and 3.92 g, to a methanol solution of modified polyethyleneimine. The mixture was stirred for 2 hours to allow the modified polyethyleneimine to fill the pores of the fumed silica. The mixture was reportedly heated in a vacuum oven at 50°C for 12 hours to remove the solvent. In Example 3, modified polyethyleneimine was added to a borosilicate support. It is disclosed that 2.96 g of borosilicate was added to a methanol solution of modified polyethyleneimine. The mixture was reportedly stirred for 2 hours to allow the modified polyethyleneimine solution to fully fill the pores of the borosilicate.The mixture was heated in a vacuum oven at 50° C. for 12 hours and the solvent was removed.

[0020] U.S. Patent No. 10,751,689 B2, derived from WO / 2016 / 114991A1, relates to a regenerable solid adsorbent for absorbing carbon dioxide from gas mixtures containing air. This is allegedly achieved using an adsorbent comprising a modified polyamine and a solid support. The modified polyamine is the reaction product of an amine and an epoxide. Example 1 discloses the preparation of a modified polyamine species based on pentaethylenehexamine (PEHA) and propylene oxide (PO). This preparation involves dissolving 10 g of PEHA in 40 mL of water, adding 5 g of PO to the PEHA solution, and then stirring at room temperature for 20 hours. The temperature of the reaction mixture was gradually increased to 60°C and maintained for 2 hours. The water was removed using a rotary evaporator, followed by overnight storage at a vacuum of less than 1 mmHg. This disclosure reveals that a supported polyamine sorbent was prepared from this modified polyamine by dissolving 3 g of the modified polyamine in 10 mL of water and suspending 2 g of Sipernat 50S in 40 mL of water. The modified polyamine solution was then slowly added to the Sipernat 50S suspension under stirring, followed by further stirring at room temperature for 20 hours. The mixture was then rotary evaporated and subjected to a vacuum (<1 mmHg) overnight. The resulting supported polyamine sorbent was a white solid that was reportedly crushed and sieved to produce a solid with a uniform particle size distribution. Example 2 also contains a similar disclosure. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] U.S. Patent No. 7,795,175 B2 [Patent Document 2] U.S. Patent No. 9,084,960 B2 [Patent Document 3] U.S. Patent No. 9,533,250 B2 [Patent Document 4] US Patent No. 11,229,897 B2 [Patent Document 5] U.S. Patent No. 10,010,861 B2 [Patent Document 6] WO / 2016 / 114991A1 [Patent Document 7] US Patent No. 10,751,689 B2 [Non-patent literature]

[0022] [Non-Patent Document 1] Kim, JY et al., Laboratory-scale continuous testing of silica-PEI adsorbent in a fluidized bed system, International Journal of Greenhouse Gas Control, 82 (2019), pp. 184-191 [Non-patent document 2] Zhang, W. et al., Simulation of post-combustion CO2 capture process in coal-fired and natural gas-fired power plants using polyethyleneimine / silica adsorbent, International Journal of Greenhouse Gas Control, 58 (2017), pp. 276-289 [Non-patent document 3] Zhang, W. et al., Cycling Performance Evaluation of Polyethyleneimine / Silica Adsorbent with Steam Regeneration Function Using Simulated NGCC Exhaust Gas and Actual Exhaust Gas from a Gas Boiler in a Bubbling Fluidized Bed Reactor, International Journal of Greenhouse Gas Control, 95(2020), p.102975 [Non-patent document 4] Kim, JY et al., Performance of silica-polyethyleneimine adsorbent for post-combustion CO2 capture at 100 kg scale in a fluidized bed continuous reactor, Chemical Engineering Journal 407 (2021) p. 127209 [Non-patent document 5] Choi, W. et al., Epoxy functionalization of polyethyleneimine for the synthesis of carbon dioxide adsorbents stable in temperature swing adsorption, Nature Communications, 7(1), pp. 1-8, 2016 [Non-patent document 6] Le, MUT et al., Preparation and Characterization of PEI-Supported MCM-41 for CO2 Capture, International Journal of Hydrogen Energy 39 (2014) pp. 12340-12346 [Non-Patent Document 7] Lie, K. et al., Effect of Polyethyleneimine Type and Molecular Weight on CO2 Capture Performance of PEI Nanosilica Adsorbent, Applied Energy, 136(2014), 750-755 [Non-patent document 8] Li K et al., Polyethyleneimine-nanosilica composite: a low-cost and promising adsorbent for CO2 capture, Journal of Materials Chemistry A, 2015, 3, 2166-75 [Non-Patent Document 9] Park, S. et al., Epoxy-functionalized poly(ethyleneamine)-supported silica / polymer module enabling sustainable CO2 capture by rapid thermal swing adsorption, Industrial & Engineering Chemistry Research, 2018, 57, pp. 13923-13931 Summary of the Invention [Problem to be solved by the invention]

[0023] It is an object of the present invention to provide a solid sorbent for CO in an efficient and environmentally friendly manner, and to provide a CO sorbent having desirable CO capture properties, such as desirable CO adsorption rate and / or CO loading capacity and / or oxidative stability and / or processability. [Means for solving the problem]

[0024] According to one aspect of the present invention, there is provided an adsorbent suitable for absorbing carbon dioxide from a gas mixture, the adsorbent comprising: (A) a polyalkyleneimine or an alkoxylated polyalkyleneimine; and (B) an inorganic solid support; Including, The polyalkyleneimine or alkoxylated polyalkyleneimine (A) is disposed on an inorganic solid support (B), wherein the adsorbent contains more than 2% by weight of water based on the total weight of the adsorbent.

[0025] The adsorbent is typically provided in the form of particles, with free-flowing particles being particularly preferred, although the adsorbent particles may also be in the form of a powder.

[0026] The present application also provides a method for preparing the above-mentioned adsorbent, the method comprising: A step of supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting step comprising contacting (A) with (B) in the presence of water, and then obtaining an adsorbent. Includes.

[0027] In other words, there is provided a method for preparing an adsorbent suitable for absorbing carbon dioxide from a gas mixture, the adsorbent comprising: (A) a polyalkyleneimine or an alkoxylated polyalkyleneimine; and (B) an inorganic solid support; Including, The polyalkyleneimine or alkoxylated polyalkyleneimine (A) is disposed on an inorganic solid support (B), This method: a step of supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting step comprising contacting (A) with (B) in the presence of water, and thereafter obtaining an adsorbent product; Including, wherein the adsorbent contains more than 2% by weight of water based on the total weight of the adsorbent.

[0028] The adsorbent prepared by this method is suitably as defined above or according to any embodiment of the adsorbent of the invention herein.

[0029] In the above-described method, once A is supported on B, the resulting adsorbent can be obtained by any conventional means, such as filtration and / or water removal, depending on the amount of water to be removed. Thus, the step of obtaining the adsorbent may include water removal. Water removal can be achieved by any conventional drying means, such as air drying, centrifugation, under reduced pressure and / or heat (e.g., in an oven such as a vacuum oven), if desired or necessary. According to the above-described embodiment, the resulting adsorbent contains more than 2% by weight of water, based on the total weight of the adsorbent. This water content can be achieved by appropriately controlling the drying conditions so as not to dry the adsorbent below this water content.

[0030] In another aspect, the present application provides a method for preparing a sorbent suitable for absorbing carbon dioxide from a gas mixture, the method comprising: a step of supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting step comprising contacting (A) with (B) in the presence of water, and thereafter obtaining an adsorbent product; Including, wherein the mass ratio of the aqueous solvent to the inorganic carrier (B) in the supported mixture does not exceed 5:1; The method further includes obtaining an adsorbent from the supported mixture, the adsorbent comprising a polyalkyleneimine or alkoxylated polyalkyleneimine (A) supported on an inorganic solid support (B).

[0031] Advantageously, the method of the present invention utilizes a relatively small amount of aqueous solvent (e.g., water) as the solvent. In a preferred embodiment, the weight ratio of aqueous solvent (e.g., water) to inorganic support (B) in the loading mixture does not exceed 3:1, or 2:1, or 1.5:1, 1:1, 0.5:1, or 0.2:1. After the loading step, the adsorbent can be obtained by filtration and / or removal of the aqueous solvent. Removal of the aqueous solvent can be carried out by any conventional drying means, such as air drying, centrifugal drying, optionally under reduced pressure and / or heat (e.g., in an oven such as a vacuum oven).

[0032] According to a preferred embodiment of the above process, the resulting adsorbent contains more than 2% by weight of water based on the total weight of the adsorbent, which can be achieved by appropriately controlling the drying conditions, in particular so as not to dry the adsorbent below this water content.

[0033] In embodiments where the weight ratio of aqueous solvent to inorganic support (B) in the loading mixture is relatively low (e.g., 3:1 or less, e.g., 2:1 or less, or 1.5:1 or less, or 1:1 or less, e.g., 0.5:1 or less), the adsorbent can be obtained directly in a suitable usable form, i.e., without the need for an aqueous solvent removal step such as drying. In certain embodiments, the aqueous solvent content in the loading mixture is sufficiently low so that the inorganic support remains a powder throughout the loading process. The resulting adsorbent can be further dried if necessary, but preferably is not dried to a moisture content of 2% by weight or less, based on the total weight of the adsorbent.

[0034] The present invention also provides an adsorbent obtained or obtainable according to any of the inventive methods described herein.

[0035] In another aspect, the present application provides a method for preparing a sorbent suitable for absorbing carbon dioxide from a gas mixture, the method comprising: a step of supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting step comprising contacting (A) with (B) in the presence of water, and thereafter obtaining an adsorbent product; Including, wherein the ratio of the total mass of the liquid in the support mixture to the mass of the inorganic support (B) in the support mixture does not exceed 10:1; The method further includes obtaining an adsorbent from the supported mixture, the adsorbent comprising a polyalkyleneimine or alkoxylated polyalkyleneimine (A) supported on an inorganic solid support (B).

[0036] Desirably, in the above aspects, the mass ratio calculation is based on the total mass of the liquid components of the mixture relative to the inorganic support (B). It will be understood that in typical embodiments, the liquid component of the loading mixture comprises, and in embodiments, consists of, an aqueous solvent (e.g., water) combined with the PEI or alkoxylated PEI component (A). Such components typically combine to form a liquid solution. The inventors have found that keeping the total liquid component relative to the inorganic component low is practically advantageous. This is useful for improving loading efficiency, allowing materials to be more easily processed during the loading process, and reducing the practical need for solvent removal after the loading process is complete. For example, it helps ensure that a small amount of excess liquid remains after the pores of the inorganic support (B) are filled with liquid. In preferred embodiments, the mass ratio of liquid to inorganic support (B) in the loading mixture does not exceed 6:1, or 4:1, or 3:1, 2:1, or 1:1, or 0.5:1. After the loading step, the adsorbent can be obtained by filtration and / or removal of the aqueous solvent, which can be done by any conventional drying means, such as air drying, centrifugation drying, optionally under reduced pressure and / or heat (e.g., in an oven such as a vacuum oven).

[0037] According to a preferred embodiment of the method, the resulting adsorbent contains more than 2% by weight of water, based on the total weight of the adsorbent. This water content can be achieved by appropriately controlling the drying conditions, in particular by not drying the adsorbent below this water content.

[0038] In embodiments where the mass ratio of the liquid in the loading mixture to the inorganic support (B) in the loading mixture is relatively low (e.g., 6:1 or less, e.g., 4:1 or less, or 3:1 or less, or 2:1 or less, e.g., 1:1 or less, e.g., 0.5:1 or less), the adsorbent can be obtained directly in a suitable usable form, i.e., without the need for an aqueous solvent removal step such as drying. In certain embodiments, the liquid content in the loading mixture is sufficiently low so that the inorganic support remains a powder throughout the loading process. The resulting adsorbent can be further dried if necessary, but is preferably not dried to less than 2% by weight moisture, based on the total weight of the adsorbent.

[0039] The present invention also encompasses the use of the adsorbent defined according to the invention, for example for recovering carbon dioxide from a gas mixture. The use method for recovering carbon dioxide can include a subsequent step of desorbing the captured carbon dioxide. This is advantageous in the context of CO2 transportation. It also has the advantage that the adsorbent can be reused to adsorb more CO2, allowing for reuse of the adsorbent. Desorption can be preferably carried out by heating. Due to the significantly improved oxidative stability of the product according to the invention, it is desirable to recycle it in this way multiple times, for example, each use cycle comprising both adsorption and subsequent desorption of carbon dioxide.

[0040] The adsorbent of the present invention comprises a polyalkyleneimine or alkoxylated polyalkyleneimine (A) supported on an inorganic solid support (B). In embodiments where the inorganic solid support is porous, the supporting step can suitably include impregnating the solid support with a polymer. When the terms impregnation, impregnated, or impregnating are used herein, these therefore refer to supporting a polymer on a porous support. [Brief explanation of the drawings]

[0041] [Figure 1] Figure 1 is an image of a Greaves VS-1 laboratory mixer mixing a polyethyleneimine / water solution in a 10 L bucket. [Figure 2] FIG. 2 graphically depicts the nitrogen adsorption isotherm for silica 1 impregnated with PEI 1 (MW 800) to obtain a loading of 30-50% w / w. [Figure 3] Figure 3 graphically shows the N2 adsorption isotherms for silica 1 impregnated with PEI2 (MW 5000 g / mol) to obtain loadings of 30-50% w / w. [Figure 4] Figure 4 graphically shows the CO2 uptake of silica 1 impregnated with PEI 1 (MW 800 g / mol) to obtain 30-50% w / w loading. [Figure 5] Figure 5 graphically shows the CO2 uptake of silica 3 impregnated with PEI 1 (MW 800 g / mol) to obtain 30-50% w / w loading. [Figure 6] Figure 6 graphically shows the CO2 uptake of silica 3 impregnated with PEI 1 (MW 800 g / mol) to obtain 30-50% w / w loading. [Figure 7] Figure 7 graphically shows the CO2 uptake of silica 3 impregnated with PEI2 (MW 5000 g / mol) to obtain 30-50% w / w loading. [Figure 8]FIG. 8 is a graph comparing the loss of CO2 adsorption capacity during oxidation at 80°C for silica-PEI with loadings of 30, 40, and 47% w / w using silica 1 and PEI 2. [Figure 9] FIG. 9 is a graph comparing the loss of CO2 adsorption capacity during oxidation at 70° C. for silica-PEI with 40 and 47% w / w loadings using Silica 1 and PEI 2. [Figure 10] FIG. 10 graphically depicts the CO2 uptake of silica 1 impregnated with PEI2 at a moisture content below 2% w / w and vacuum dried to 4.5% w / w. [Figure 11] Figure 11 is a graph comparing the loss of CO2 adsorption capacity of silica-PEI (using silica 1 and PEI 2, 47% w / w) upon vacuum drying to moisture contents of less than 2% w / w and 4.5% w / w at 80 °C in air over 10 days. [Figure 12] Figure 12a graphically shows the CO2 uptake of silica 1 impregnated with PEI1 (50% w / w solution) to obtain a loading of 47% w / w, with total water contents of 1.06, 8.55, and 17.98 g of added water per g of silica due to mixing and 1.94, 9.43, and 18.87 g of overall water content per g of silica due to mixing. [Figure 13] Figure 12b graphically shows the CO2 uptake of silica 1 impregnated with PEI1 (99% w / w solution) to obtain a 47% w / w loading, with added water content per gram of silica due to blending of zero, 0.5, 1, 2, 8, 10, 20, and 40 g, and overall water content per gram of silica due to blending of 0.01, 0.51, 1.01, 2.01, 8.01, 10.01, 20.01, and 40.01 g. [Figure 14] FIG. 13 graphically depicts CO2 uptake at 75°C for silica 1 impregnated with PEI2 (50% w / w solution) to obtain loadings of 30-50% w / w. [Figure 15]FIG. 14 graphically depicts CO2 uptake at 75°C for silica 2 impregnated with PEI2 (50% w / w solution) from 30-50% w / w. [Figure 16] FIG. 15 graphically depicts CO2 uptake at 75°C for silica 3 impregnated with PEI2 (50% w / w solution) to obtain loadings of 20-43% w / w. [Figure 17] FIG. 16 graphically depicts CO2 uptake at 75°C for silica 4 impregnated with PEI2 (50% w / w solution) to obtain loadings of 30-50% w / w. [Figure 18] FIG. 17 graphically depicts CO2 uptake at 75°C for QuadraSil® MP(I) Silica impregnated with PEI2 (50% w / w solution) to obtain loadings of 10-35% w / w. [Figure 19] FIG. 18 graphically depicts CO2 uptake at 75°C for Sylobead® SG W Silica impregnated with PEI2 (50% w / w solution) to obtain loadings of 5-20% w / w. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present inventors have now developed a new sorbent that is effective in absorbing carbon dioxide from a gas mixture containing carbon dioxide, such as air or exhaust gas, for example from the combustion of carbonaceous materials such as fossil fuels. A new and advantageous method for preparing the sorbent has also been developed.

[0043] As mentioned above, the present invention provides an adsorbent suitable for absorbing carbon dioxide from a gas mixture, the adsorbent comprising: (A) a polyalkyleneimine or an alkoxylated polyalkyleneimine; and (B) an inorganic solid support; Including, The polyalkyleneimine or alkoxylated polyalkyleneimine (A) is disposed on an inorganic solid support (B), wherein the adsorbent contains more than 2% by weight of water based on the total weight of the adsorbent.

[0044] The adsorbent can be conveniently prepared by the aqueous support method described herein. The described aqueous method is procedurally simple, and because the liquid medium is aqueous, the method has a low environmental impact and is relatively safer than traditional manufacturing methods that use organic solvents. Therefore, the claimed product can be easily obtained by a simple and environmentally friendly method. In the preferred method described herein, the amount of aqueous solvent used is particularly small, which provides practical and efficiency advantages.

[0045] Traditionally, polyamines (including those using polyethyleneimine and alkoxylated polyethyleneimine) are supported on inorganic solid supports such as silica using organic solvents, particularly polar organic solvents such as methanol. Methanol is a convenient solvent because these polyamine materials tend to be highly soluble in methanol and because its relatively low boiling point allows for easy removal after production. However, because methanol is a carbon-containing compound, it is not an ideal solvent choice from an environmental perspective due to the potential for fugitive emissions, especially when the typical purpose of the adsorbent product is to remove carbon (in the form of carbon dioxide) from air or waste combustion gases. Furthermore, even if care and effort is taken to subsequently remove the organic solvent, residual organic solvent may remain in the final adsorbent product. This is less than ideal, especially if the adsorbent is intended to be recycled (by desorbing and re-adsorbing CO2). This is because typical adsorbent recycling processes involve heating the adsorbent, which can release residual methanol along with the CO2.

[0046] The aforementioned U.S. Pat. No. 10,751,689 B2 discloses a specific method for supporting propylene oxide-modified pentaethylenehexamine on a Sipernat® 50S (silica) support using an aqueous solvent system (e.g., Example 2). However, while water is environmentally friendly, it is not generally considered a desirable solvent in such processes because its boiling point is higher than that of conventional polar organic solvents, making it difficult to remove from the final material. In particular, U.S. Pat. No. 10,751,689 B2 teaches those skilled in the art that a very large amount of water is required in the support mixture (water to silica mass ratios of 25:1 or more in the support mixtures according to Examples 1 and 2), necessitating energy-intensive processes to remove this water. Furthermore, conventional wisdom in the field of solid CO2 adsorbents is that, for example, in the case of silica or zeolite adsorbents, the presence of water or moisture in the product reduces the CO2 adsorption capacity. This is acknowledged in column 2, line 24 of U.S. Pat. No. 10,751,689 B2. Consistent with this, U.S. Pat. No. 10,751,689 B2 consistently teaches those skilled in the art to remove moisture after its aqueous manufacturing process by vacuum drying with heating (e.g., column 12, lines 58-67 and Example 2).

[0047] Despite the above-mentioned disadvantages of using organic solvent processes and the environmental advantages of using water, organic solvent processes are widely used in industry for the production of inorganic solid supported polyamine adsorbents.

[0048] However, the present inventors have discovered that, contrary to conventional wisdom, it is not necessary to remove all water from inorganic solid-supported adsorbents after the aqueous polyalkyleneimine loading step to achieve desirable adsorbent properties. Indeed, the present inventors have found that increasing the water content of the adsorbent product to greater than 2% by weight significantly improves carbon dioxide absorption performance. In particular, as shown with reference to Example 2 and FIG. 12 herein, adsorbents of the present invention having a higher water content exhibit similar CO2 adsorption rates compared to reference samples containing less than 2% by weight water, and exhibit slightly higher adsorption capacities compared to the reference samples upon first use (without wishing to be bound by theory, this is believed to be due, at least in part, to partial decomposition of the polyamine in the reference samples due to the more severe drying conditions). However, what is noteworthy is the significant improvement in oxidative stability compared to the reference samples (which indicates the ability of the adsorbent to continue adsorbing CO2 over time). It is surprising and highly advantageous that products of the present invention can provide such improvements compared to reference samples containing less or no water at all.

[0049] The adsorbents of the present invention are an important contribution to the art because they exhibit sufficient CO2 adsorption rates and loading capacities, are highly stable compared to comparative adsorbents, and can be easily, and indeed preferably, prepared using environmentally benign aqueous processes that require less energy and time and require less care in handling the resulting products than methods that previously required complete removal of water.

[0050] Thus, the adsorbent according to the product claims of the present invention contains more than 2% by weight of water based on the weight of the adsorbent. Desirably, the adsorbent can contain at least 2.5% by weight, more desirably at least 3.0% by weight, even more desirably at least 3.5% by weight, and preferably at least 4.0% by weight, e.g., about 4.5% by weight, based on the total weight of the adsorbent. There is no particular upper limit to the amount of water that should be present in the adsorbent. However, there may be practical considerations that should be taken into account when including significant amounts of water in the adsorbent. Thus, the adsorbent can contain 20% or more by weight of water based on the weight of the adsorbent. In some embodiments, including those described above, the adsorbent can contain 20% or less by weight of water based on the weight of the adsorbent, e.g., 15% or less by weight, or 10% or less by weight, or 7.5% or less by weight of water. For example, the amount of water contained in the adsorbent can be 2.5% by mass to 20% by mass, such as 3.0% by mass to 10% by mass, such as 3.5% by mass to 7.5% by mass, or 4.0% by mass to 7.5% by mass, such as 4.5% by mass.

[0051] The present invention also provides a method for producing the described adsorbent, the method comprising supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting comprising contacting the polyalkyleneimine or alkoxylated polyalkyleneimine (A) and the inorganic solid support (B) in the presence of an aqueous solvent (typically water), and then obtaining the adsorbent.

[0052] Thus, the method of the present invention avoids the need for expensive and environmentally harmful organic solvents and the need to remove the organic solvent from the supported inorganic solid support, which carries the risk of residual organic solvent remaining in the adsorbent. Organic solvents in the adsorbent can have a detrimental effect on carbon dioxide absorption and / or some of the residual solvent can later be desorbed during any CO2 desorption process, contaminating the desorbed CO2 and leading to further carbon emissions. Therefore, organic solvents are preferably avoided entirely in current methods, i.e., methods in which the solvent is water.

[0053] In a preferred embodiment of this method, contacting (A) and (B) in the presence of an aqueous solvent results in a supported mixture, wherein the weight ratio of the aqueous solvent to the inorganic support (B) in the supported mixture does not exceed 5:1. It will be understood that this can be achieved by controlling the amount of aqueous solvent provided with component (A) and / or (B). The amount of aqueous solvent provided with component (A) or the alternative solvent provided with component (B) may be relatively large, but the total amount of aqueous solvent (e.g., typically water) in the supported mixture preferably does not exceed the amount described above.

[0054] Optionally, the weight ratio of the aqueous solvent to the inorganic carrier (B) in the supported mixture does not exceed 3:1, and optionally, the weight ratio of the aqueous solvent to the inorganic carrier (B) in the supported mixture does not exceed 2:1. In a preferred embodiment, the weight ratio of the aqueous solvent to the inorganic carrier (B) in the supported mixture does not exceed 1:1. In such a method, the weight ratio of the aqueous solvent to the inorganic carrier (B) in the supported mixture is typically at least 0.2:1 or at least 0.5:1, such as at least 0.8:1, for example at least 1:1. The weight ratio of water to the inorganic carrier (B) in the supported mixture may be, for example, 0.2:1 to 5:1, 0.2:1 to 3:1, 0.2:1 to 2:1, or 0.2:1 to 1.5:1. The mass ratio of water to inorganic carrier (B) in the supported mixture may be, for example, 0.5:1 to 5:1, 0.5:1 to 3:1, 0.5:1 to 2:1, or 0.5:1 to 1.5:1, or may be, for example, 1:1 to 5:1, 1:1 to 3:1, 1:1 to 2:1, or 1:1 to 1.5:1.

[0055] In a preferred embodiment of the method disclosed herein, the total volume of aqueous solvent in the loading step does not exceed 80% of the total pore volume of the inorganic support (B), for example, not exceeding 75% or 70% of the total pore volume of the inorganic support, and may be, for example, 50% or less. In embodiments, the total volume of aqueous solvent used does not exceed 40%, 30%, 25%, 20%, 15%, or 10% of the total pore volume of the inorganic support (B). The total volume of aqueous solvent in this context refers to the total amount of aqueous solvent contributed to the mixture when (A) and (B) are combined. It has been found that by controlling the amount of aqueous solvent used so that it is less than the pore volume of the support, it is advantageously possible to sufficiently load (A) onto (B) while ensuring that the inorganic support (B) remains a flowable powder throughout the process. This also minimizes the use of aqueous solvent while avoiding the need to remove large amounts of water after the loading step. It should also be understood that the rate of addition of (A) to (B), or the rate of addition of (B) to (A), will be adjusted by one skilled in the art to provide suitable process characteristics, such as avoiding caking of (B) or excessive wetting of (B).

[0056] The inorganic support is typically provided in the form of particles. In such embodiments, depending on the aqueous solvent content, the support mixture can have a paste consistency. In particularly advantageous embodiments, the water content may be selected to ensure that the inorganic support in the support mixture remains powder (i.e., without caking) during the support process. It was surprising and advantageous to discover that the support of a polymer on an inorganic support to provide a CO2 adsorbent with excellent properties can be carried out using such a small amount of water as a solvent. Thus, in such embodiments, organic solvents and excessive amounts of water are not required. This reduces both the need for water in the support process and the time and energy required to remove the water after support, improving the efficiency of the process (with practical and environmental benefits).

[0057] In the above process, once A is supported on B to form the adsorbent, the resulting adsorbent can be obtained by any conventional means. Depending on the final water content in the product mixture, it may be desirable to remove some of the water to obtain the product. Water removal can be achieved by any conventional means, such as filtration and / or drying under reduced pressure and / or heat (e.g., in an oven such as a vacuum oven), if desired or necessary.

[0058] Accordingly, the present invention also provides a method for producing the described adsorbent, the method comprising supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), wherein the supporting comprises contacting the polyalkyleneimine or alkoxylated polyalkyleneimine (A) and the inorganic solid support (B) in the presence of an aqueous solvent to form a supported mixture (comprising the adsorbent and the aqueous solvent), and the method further comprises removing water from the supported mixture, for example by drying, to obtain the adsorbent.

[0059] In a further aspect of the present invention, the present application provides a method for preparing an adsorbent suitable for absorbing carbon dioxide from a gas mixture, the method comprising: A step of supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting step comprising contacting (A) with (B) in the presence of an aqueous solvent to obtain a resulting supported mixture. Including, wherein the mass ratio of the aqueous solvent to the inorganic carrier (B) in the supported mixture does not exceed 5:1; The method further includes obtaining an adsorbent from the supported mixture, the resulting adsorbent comprising a polyalkyleneimine or alkoxylated polyalkyleneimine (A) supported on an inorganic solid support (B).

[0060] Advantageously, the method of the present invention utilizes a relatively small amount of aqueous solvent (preferably water) as the solvent. It will be understood that the proportion of aqueous solvent in the support mixture is controlled by controlling the amount of aqueous solvent provided to component (A) and / or (B). The aqueous solvent provided with component (A) or alternatively component (B) may be relatively higher, but the total amount of aqueous solvent (e.g., typically water) in the support mixture does not exceed the amount described above.

[0061] In a preferred embodiment, the weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture is not greater than 3:1, or 2:1, or preferably not greater than 1.5:1. In such a method, the weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture is typically at least 0.2:1, or at least 0.5:1, for example, at least 0.8:1, for example, at least 1:1. The weight ratio of the aqueous solvent (e.g., water) to the inorganic carrier (B) in the support mixture may be, for example, 0.2:1 to 5:1, 0.2:1 to 3:1, 0.2:1 to 2:1, or 0.2:1 to 1.5:1. The weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture may be, for example, 0.5:1 to 5:1, 0.5:1 to 3:1, 0.5:1 to 2:1, or 0.5:1 to 1.5:1. For example, it may be 1:1 to 5:1, 1:1 to 3:1, 1:1 to 2:1, or 1:1 to 1.5:1.

[0062] In a preferred embodiment, the total volume of the aqueous solvent used does not exceed 80% of the total pore volume of the inorganic support, for example, not exceeding 75% or 70% of the total pore volume of the inorganic support, and may be, for example, 50% or less. In an embodiment, the total volume of the aqueous solvent used does not exceed 40%, 30%, 25%, 20%, 15%, or 10% of the total pore volume of the inorganic support (B). The total volume of the aqueous solvent in this context refers to the total amount of aqueous solvent that contributes to the mixture when (A) and (B) are combined. Typically, this refers to the total amount of water present. It has been found that by controlling the amount of aqueous solvent used so that the amount is less than the pore volume of the support, it is possible to advantageously sufficiently load (A) on (B) while ensuring that the inorganic support (B) remains a flowable powder throughout the process. This also minimizes the use of aqueous solvent while avoiding the need to remove large amounts of water after the loading step. It should also be understood that the rate of addition of (A) to (B) or the rate of addition of (B) to (A) can optionally be adjusted by one skilled in the art to provide suitable process characteristics, such as avoiding caking of (B) or excessive wetting of (B).

[0063] The inorganic support is typically provided in the form of particles. In such embodiments, depending on the aqueous solvent content, the support mixture can have a paste consistency. In particularly advantageous embodiments, the water content may be selected to ensure that the inorganic support in the support mixture remains powder (i.e., without caking) during the support process. It was surprising and advantageous to discover that the support of a polymer on an inorganic support to provide a CO2 adsorbent with excellent properties can be carried out using such a small amount of water as a solvent. Thus, the method of the present invention does not require organic solvents or excessive amounts of water. This reduces both the amount of water used in the support process and the time and energy required to remove water to the desired level after the support process, improving the efficiency of the process (with practical and environmental benefits).

[0064] The adsorbent prepared by the above method may suitably be as defined above or may be in accordance with any of the embodiments of the adsorbent of the present invention herein. Preferably, the adsorbent obtained by the above method comprises more than 2% by weight of water, based on the total weight of the adsorbent.

[0065] In the above-described method, once A is supported on B to form the adsorbent, the resulting adsorbent can be obtained from the supported mixture by any conventional means, depending on the water content of the mixture and the desired final water content of the adsorbent. For example, if excess water is present in the supported mixture after the supporting step, the adsorbent can be obtained by filtration and / or water removal. Water removal can be carried out, if desired, by any conventional drying means, such as air drying under reduced pressure and / or heat (e.g., in an oven such as a vacuum oven), or centrifugation. According to a preferred embodiment of the above-described method, the resulting adsorbent contains more than 2% by weight of water, based on the total weight of the adsorbent. This water content can be achieved by appropriately controlling the drying conditions, particularly by not drying the adsorbent below this water content. However, in embodiments in which the weight ratio of aqueous solvent to inorganic support (B) in the supported mixture is relatively low (e.g., 3:1 or less, e.g., 2:1 or less, or 1.5:1 or less), the adsorbent can be obtained directly in a suitable usable form, i.e., without the need for an aqueous solvent removal step such as drying. In certain embodiments, the aqueous solvent content in the loading mixture is low enough so that the inorganic support remains a powder throughout the loading process. The resulting adsorbent may be further dried if desired, but preferably is not dried to a moisture content of 2% by weight or less, based on the total weight of the adsorbent.

[0066] In another aspect of the present invention, the present application provides a method for preparing a sorbent suitable for absorbing carbon dioxide from a gas mixture, the method comprising: A step of supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting step comprising contacting (A) with (B) in the presence of an aqueous solvent to obtain a resulting supported mixture. Including, wherein the ratio of the total mass of the liquid in the support mixture to the mass of the inorganic support (B) in the support mixture does not exceed 10:1; The method further includes obtaining an adsorbent from the supported mixture, the adsorbent comprising a polyalkyleneimine or alkoxylated polyalkyleneimine (A) supported on an inorganic solid support (B).

[0067] Desirably, in the above embodiments, the mass ratio calculation is based on the total mass of the liquid components of the mixture relative to the inorganic support (B). It should be understood that in typical embodiments, the liquid component of the loading mixture comprises, and in some embodiments consists of, an aqueous solvent (e.g., water) combined with the PEI or alkoxylated PEI component (A). Such components typically combine to form a solution. The inventors have found that it is practically advantageous to keep the total liquid component provided in the mixture low. This helps improve loading efficiency, allows the material to be more easily handled during the loading process, and reduces the practical need for solvent removal after the loading process is complete. For example, it helps to ensure that the amount of excess liquid remaining is low once any pores in the inorganic support (B) are filled with liquid. In preferred embodiments, the mass ratio of the liquid in the loading mixture to the inorganic support (B) in the loading mixture does not exceed 6:1, or 4:1, or 3:1, 2:1, or 1:1, or 0.5:1. After the loading step, the adsorbent can be obtained by filtration and / or removal of the aqueous solvent, which can be done by any conventional drying means, such as air drying under reduced pressure and / or heat (e.g., in an oven such as a vacuum oven), or centrifugation, if desired.

[0068] According to a preferred embodiment of the above process, the resulting adsorbent contains more than 2% by weight of water based on the total weight of the adsorbent, which can be achieved by appropriately controlling the drying conditions, in particular so as not to dry the adsorbent below this water content. In embodiments where the mass ratio of the liquid in the loading mixture to the inorganic support (B) in the loading mixture is relatively low (e.g., 6:1 or less, e.g., 4:1 or less, or 3:1 or less, or 2:1 or less, e.g., 1:1 or less, e.g., 0.5:1 or less), the adsorbent can be obtained directly in a suitable usable form, i.e., without the need for an aqueous solvent removal step such as drying. In certain embodiments, the liquid content in the loading mixture is sufficiently low so that the inorganic support remains a powder throughout the loading process. The resulting adsorbent can be further dried if necessary, but is preferably not dried to less than 2% by weight moisture, based on the total weight of the adsorbent.

[0069] In a preferred embodiment, the mass ratio of the liquid to the inorganic carrier (B) in the support mixture does not exceed 6:1, or 4:1, or preferably 3:1. In such a method, the mass ratio of the liquid to the inorganic carrier (B) in the support mixture is typically at least 0.4:1 or at least 1:1, for example at least 1.6:1, for example at least 2:1. The mass ratio of the liquid to the inorganic carrier (B) in the support mixture may be, for example, 0.4:1 to 10:1, 0.4:1 to 6:1, 0.4:1 to 4:1, or 0.4:1 to 3:1. The mass ratio of the liquid to the inorganic carrier (B) in the support mixture may be, for example, 1:1 to 10:1, 1:1 to 6:1, 1:1 to 4:1, or 1:1 to 3:1. For example, it may be 2:1 to 10:1, 2:1 to 6:1, 2:1 to 4:1, or 2:1 to 3:1.

[0070] In some embodiments, the total amount of liquid used does not exceed 80% of the total pore volume of the inorganic support, for example, not exceeding 75% or 70% of the total pore volume of the inorganic support, and may be, for example, 50% or less. In embodiments, the total volume of aqueous solvent used does not exceed 40%, 30%, 25%, 20%, 15%, or 10% of the total pore volume of the inorganic support (B). In this context, the total volume of liquid refers to the total amount of liquid contributed to the mixture when components (A) and (B) are combined with the aqueous solvent component. It has been found that by controlling the amount of liquid used so that it is less than the pore volume of the support, it is advantageous to be able to sufficiently support (A) on (B) while ensuring that the inorganic support (B) remains a flowable powder throughout the process. This also minimizes the use of aqueous solvent, while avoiding the need to remove large amounts of water after the support step. It should also be understood that the rate of addition of (A) to (B) or the rate of addition of (B) to (A) can be adjusted by one skilled in the art to provide suitable process characteristics, such as avoiding caking of (B) or excessive wetting of (B), as the case may be.

[0071] In all of the methods of the present invention described herein, it is desirable to avoid heating the adsorbent to high temperatures during water removal, as this has been observed to lead to a decrease in CO2 adsorption capacity, likely caused by degradation of the polyalkyleneimine / alkoxylated polyalkyleneimine. Typical temperatures for drying generally depend on the size and type of dryer. For example, laboratory ovens may use temperatures above 50°C, e.g., 80°C to 100°C or higher. However, industrial-scale dryers do not operate at such high temperatures; instead, effective drying temperatures may be significantly lower. Preferably, the evaporation temperature should not be too high to avoid damaging the adsorbent. In embodiments, the temperature during the step of removing water from the product does not exceed 95°C, e.g., 80°C, or 75°C, and in embodiments remains below 60°C, e.g., below 50°C, 40°C, or 30°C.

[0072] When drying under reduced pressure, the exact pressure is not particularly important, provided that effective drying is achieved (except, in the case of the inventive products described herein, as long as the product is dried to less than 2% moisture by weight). Typical reduced pressures range, for example, from 100 mbar to 500 mbar. As discussed herein, the adsorbent thus formed should not be over-dried to remove all of the water.

[0073] Therefore, the desired water content of the adsorbent can be easily achieved by controlling the amount of water in the support mixture and / or by controlling the water removal step after the adsorbent is obtained, for example, by controlling the drying conditions.

[0074] The adsorbent of the present invention refers to the product itself or the product provided by the disclosed preparation method, and is typically a particulate solid. Particular solids may be, for example, in the form of a powder, e.g., a free-flowing powder.

[0075] Typically, aqueous solvents are predominantly water-based, e.g., water or a liquid containing water in an amount of at least 60% w / w, with the remainder being a suitable co-solvent. Generally, aqueous solvents contain a much higher content of water.

[0076] Suitably, in any of the methods described herein, the aqueous solvent may comprise water in an amount of at least 90% w / w, preferably at least 95% w / w, more preferably at least 99% w / w, even more preferably at least 99.5% w / w, and especially preferably at least 99.9% w / w. Typically, the solvent is water.

[0077] In any of the processes described herein, the aqueous solvent contains <50 ppm, preferably <30 ppm, preferably <20 ppm, preferably <10 ppm methanol, optionally <50 ppm, preferably <30 ppm, preferably <20 ppm, preferably <10 ppm polar organic solvent, preferably <50 ppm, preferably <30 ppm, preferably <20 ppm, preferably <10 ppm organic solvent, preferably no methanol or no polar organic solvent or no organic solvent, based on the weight of the aqueous solvent.

[0078] These concentrations can be determined by thermal desorption of released volatiles using a gas chromatography-mass spectrometer. The GC / MS used to calculate the values ​​in this disclosure was provided by Agilent. The system configuration was a Kopplung GC-MS (7890 / 5975 or 7890 / 5977) equipped with an electron ionization source and a single quadrupole spectrometer.

[0079] The aqueous solvent is typically water (i.e., consists of water), which in embodiments may be deionized water.

[0080] Either or both of components A and B may be combined with an aqueous solvent (e.g., water) before contacting them together to form the adsorbent. The polyalkyleneimine or alkoxylated polyalkyleneimine (A) to be combined with the inorganic support (B) may be provided neat, e.g., as an anhydrous liquid, although preferably the polyalkyleneimine or alkoxylated polyalkyleneimine is provided as an aqueous solution. The amount of water can be adjusted, if necessary, by adding water to the aqueous solvent of the loading step. However, the water content is preferably controlled to avoid the use of excessive amounts, as required in certain embodiments described herein, e.g., those requiring a mass ratio of water to inorganic solids in the loading mixture not to exceed 5:1.

[0081] Component (A) in the processes / methods of the present invention may be as defined according to any definition of (A) for any embodiment herein. Component (B) in the processes / methods of the present invention may be as defined according to any definition of (B) for any embodiment herein. The adsorbent resulting from the processes / methods of the present invention may be as defined according to any definition of adsorbent for any embodiment herein.

[0082] Either or both of components (A) and (B) may be combined with an aqueous solvent before the step of contacting (A) and (B) in the loading step. In one embodiment, a dry form of inorganic solid carrier (B), preferably silica, may be combined with an aqueous solvent (e.g., water) to form an aqueous mixture containing the carrier. This may be provided in the form of a slurry dispersion or paste. In certain embodiments, the amount of water combined with (B) is kept low enough so that the resulting wet material remains in powder form, e.g., a free-flowing powder. The polyalkyleneimine or alkoxylated polyalkyleneimine (A) (provided neat or as a solution in an aqueous solvent) may then be mixed with an aqueous mixture containing inorganic solid carrier (B), where (B) is preferably silica. In an embodiment, the inorganic carrier is not combined with water before the loading step. In an embodiment, (A) is provided in the form of a solution in an aqueous solvent, preferably water.

[0083] In a preferred embodiment of the method of the present invention, the aqueous solvent is combined with the inorganic solid support (B) in an amount not exceeding 2 g of aqueous solvent per gram of inorganic solid support (B). This allows the loading level of the polyalkyleneimine or alkoxylated polyalkyleneimine (A) to approach the capacity of the inorganic solid support (B). In an embodiment, the total amount of liquid in the loading mixture (i.e., the combined amount of aqueous solvent and PEI or alkoxylated PEI component (A)) should not exceed 4 g of liquid per gram of solid support, e.g., not exceed 3 g per gram.

[0084] In the method of the present invention, the polyalkyleneimine or alkoxylated polyalkyleneimine (A) may be provided in a preformed aqueous solvent (preferably water). Alternatively, the polyalkyleneimine or alkoxylated polyalkyleneimine (A) may be formed in situ in an aqueous solvent in the presence of the inorganic solid support (B), for example, by polymerization of one or more precursors and / or alkoxylation of a polyalkyleneimine precursor. When (A) is formed in situ, it may be formed in the presence of (B), or the reaction mixture obtained after the reaction may be contacted with (B) to form the adsorbent. Preferably, (A) is not prepared in situ, i.e., it is provided in a preformed state, for example, presynthesized, or obtained from a commercial supplier. This allows for improved quality control of the final material.

[0085] The synthesis of polyalkyleneimine or alkoxylated polyalkyleneimine (A) desirably avoids the use of methanol, and in embodiments any polar organic solvent, and in preferred embodiments any organic solvent, to ensure the absence of organic solvent in the adsorbent, which has the advantages discussed above.

[0086] For the same reason, it is preferred that the polyalkyleneimine or alkoxylated polyalkyleneimine (A) component and the inorganic solid support (B) are each provided substantially free, e.g., completely free, of organic solvents such as methanol and / or acetone.

[0087] Preferably, the adsorbent according to the present invention or the adsorbent produced by the method of the present invention contains less than 50 ppm of methanol. The adsorbent preferably contains less than 50 ppm of any polar organic solvent, e.g., less than 50 ppm of any organic solvent. The above components may be present in the adsorbent at less than 30 ppm, e.g., less than 20 ppm, and more preferably less than 10 ppm. Most preferably, the level of each component should be even lower; generally, the adsorbent should be substantially free, e.g., completely free, of the listed components, e.g., methanol, polar organic solvents, or any organic solvents. The level of polar organic solvents can be determined using gas chromatography / mass spectrometry (GC / MS) from Agilent. The system configuration is a Kopplung GC-MS (7890 / 5975 or 7890 / 5977) equipped with an electron ionization source and a single quadrupole spectrometer.

[0088] By organic solvent is meant an organic liquid that dissolves or is miscible with the polyalkyleneimine or alkoxylated polyalkyleneimine. Typically, such organic solvents are polar organic solvents, examples of which include methanol, ethanol, isopropanol, acetone, DMF, or chloroform.

[0089] In all embodiments of the present invention, reference to polyalkyleneimines is preferably poly-C 2~12 - refers to alkyleneimine, most preferably polyethyleneimine, and reference to alkoxylated polyalkyleneimine preferably refers to alkoxylated poly-C 2~12 - refers to alkyleneimines, most preferably alkoxylated polyethyleneimines.

[0090] The adsorbent according to the invention (either as such or as a product produced by the described method) is preferably provided as particles. The adsorbent may, for example, be in the form of a powder, typically a free-flowing powder.

[0091] In the case of particles, the adsorbent is not limited by particle size, and a wide range of particle sizes is possible depending on the intended use. Very small particle sizes, e.g., mass average particle sizes of less than 0.1 mm, are technically possible, while in other cases, much larger mass average particle sizes of 5 mm or more may be desirable. In many applications, adsorbents having a mass average particle size of at least 0.1 mm may be preferred. The mass average particle size is often greater than 0.1 mm, even as large as 5 mm. Therefore, the adsorbent of the present invention preferably has a mass average particle size of 0.1 to 5 mm. Suitably, the mass average particle size may be 0.1 to 3 mm, particularly 0.1 to 2 mm.

[0092] Adsorbents with a mass average particle size of 5 mm or less are suitable for fixed bed operation.

[0093] Particle size distributions were measured using a Malvern Mastersizer 2000 operating in dry dispersion mode using a Scirocco dispersion unit, microvolume tray, and a dispersion pressure of 0.1 bar. Particle size distributions were determined from light scattering data using Mie theory, assuming a real refractive index of 1.46 and an imaginary refractive index of 0.1. The mean particle size determined from these distributions is the median particle size at 50% cumulative volume, which for particles of uniform density corresponds to the median at 50% cumulative mass.

[0094] The adsorbent may also be present as a honeycomb structure.

[0095] In the products or methods described herein, the inorganic solid support (B) component can have a pore volume of 0.2 to 3.0 ml per gram of inorganic solid support (B), for example, 0.5 to 2.5 ml per gram, and preferably 0.7 to 2.0 ml per gram. The inventors have found that this preferred range provides improved carbon dioxide adsorption performance and good strength characteristics. Generally, a very small pore volume can result in poor carbon dioxide adsorption performance under certain circumstances. This performance can be significantly improved by ensuring that the pore volume is no less than 0.7 ml per gram. If the pore volume is significantly larger, the strength of the inorganic solid support (B) may be compromised, especially when the inorganic solid support (B) is required for multiple cycles, for example, in moving beds and fixed beds. A pore volume of 2.0 ml per gram or less can provide optimal strength for this purpose.

[0096] Examples of materials suitable as the inorganic solid support (B) include silica (e.g., fumed silica, precipitated silica, silica gel, or γ-silica), calcium sulfate, calcium silicate, zeolite, alumina (e.g., γ-lumina), titania, aluminosilicate, or inorganic minerals. The material is preferably porous. Preferably, the inorganic solid support is silica, most preferably silica gel or precipitated silica.

[0097] Desirably, the amount of polyalkyleneimine or alkoxylated polyalkyleneimine (A) supported on the inorganic solid support (B) may be as high as possible to provide maximum CO adsorption capacity and oxidative stability. The adsorbent according to the present invention preferably has a loading of polyalkyleneimine or alkoxylated polyalkyleneimine (A) of at least 60% by weight of the maximum loading capacity of the inorganic solid support (B). Preferably, the loading capacity of the adsorbent for polyalkyleneimine or alkoxylated polyalkyleneimine (A) is at least 70% by weight, more preferably at least 80% by weight, and even more preferably at least 90% by weight of the maximum loading capacity of the inorganic solid support (B).

[0098] The maximum loading capacity of the inorganic solid support (B) may vary depending on the inorganic material used. Therefore, the maximum loading capacity refers to the maximum loading capacity of a specific material used as the inorganic solid support (B).

[0099] In the products and methods of the present invention, the adsorbent may comprise PEI / alkoxylated PEI in an amount of 10% to 70% by weight, based on the total weight of the adsorbent. A suitable loading of PEI / alkoxylated PEI on the adsorbent is 20% to 60% by weight, based on the total weight of the adsorbent. The adsorbent according to the present invention preferably has a loading of polyalkyleneimine or alkoxylated polyalkyleneimine (A) of at least 20% by weight, based on the total weight of the adsorbent. Typically, the loading of PEI / alkoxylated PEI does not exceed 60% by weight, more preferably 50% by weight, based on the total weight of the adsorbent. In one embodiment, the adsorbent comprises PEI / alkoxylated PEI in an amount of 20% to 50% by weight, e.g., 20 to 40% by weight, based on the total weight of the adsorbent.

[0100] The loading level of polyalkyleneimine or alkoxylated polyalkyleneimine (A) by weight of inorganic solid support (B) may be at least 40% by weight, for example, 40% to 60% by weight, more preferably 47% to 55% by weight, based on the weight of inorganic solid support (B). Polyalkyleneimines, in particular polyethyleneimines, are well known in the literature, for example the Lupasol® product series sold by BASF.

[0101] The polyalkyleneimine and / or alkoxylated polyalkyleneimine (A) desirably has a mass average molecular weight (M) of 300 to 20,000 g / mol, for example 300 to 15,000 g / mol, preferably 300 to 10,000 g / mol, more preferably 500 to 5,000 g / mol. W) It is preferred that the polyalkyleneimine is polyethyleneimine and the alkoxylated polyalkyleneimine is alkoxylated polyethyleneimine. It is preferred that the polyalkyleneimine and / or the alkoxylated polyalkyleneimine is branched, and is preferably based on branched polyethyleneimine. Typically, the degree of branching (DB) is greater than 50%, preferably 55 to 95%, more preferably 57 to 90%, and even more preferably 60 to 80%.

[0102] The degree of branching (DB) is described in H. Frey et al., Acata Polym. 1997, 48, 30. In this specification, the degree of branching DB is defined as follows: DB(%) = (T + Z) / (T + Z + L) × 100 (wherein T is the average number of terminally bonded monomer units (primary amino groups), Z is the average number of branched monomer units (tertiary amino groups), L is the average number of linearly linked monomer units (secondary amino groups).

[0103] T, Z and L are in DO 13 C-NMR can be used to determine the structure of branched polyethyleneimines. 13 -NMR analysis, Journal of Macromolecular Science: Part A-Chemistry, 22:5-7, 877-887, DOI: 10.1080 / 00222338508056641.

[0104] Such branched polyethyleneimines may have a variety of molecular structures, and one such example of a typical segment of a branched polyethyleneimine can be illustrated by the following exemplary structure:

[0105] [ka]

[0106] In this structure, * indicates the continuity of branched polyethyleneimine molecules.

[0107] Alkoxylated polyalkyleneimines, especially alkoxylated polyethyleneimines, are preferred as component (A) of the adsorbent over unmodified polyalkyleneimines.

[0108] Alkoxylated polyalkyleneimines are known from the literature and can generally be prepared by alkoxylation of polyalkyleneimines with alkylene oxides as alkoxylating agents. Typical descriptions are given in Houben-Weyl, Methoden der organischen Chemie, 4th Ed., Vol. 14 / 2, p. 440ff. (1963) and Vol. E 20, p. 1367f. (1987).

[0109] Preferably, the alkoxylated polyethyleneimine (A) useful in the adsorbents of the present invention is prepared by alkoxylating polyethyleneimine with an alkylene oxide, such as propylene oxide, in a reaction mixture in the substantial absence of an organic polar solvent, such as methanol, ethanol, isopropanol, or chloroform.

[0110] Typically, the alkoxylated polyalkyleneimine (A), preferably the alkoxylated polyethyleneimine, comprises alkoxyl moieties pendant from the main polyalkyleneimine, or preferably polyethyleneimine, structure. These alkoxyl moieties generally comprise one or more C2-C 12 -Alkylene oxide, preferably C2-C 10 The alkylene oxide may be based on a mixture of one or more C2-C4 alkylene oxides and one or more C8-C8 alkylene oxides, preferably ethylene oxide, propylene oxide or butylene oxide, more preferably propylene oxide or butylene oxide. The alkylene oxide may be based on a mixture of one or more C2-C4 alkylene oxides and one or more C8-C8 alkylene oxides. 12alkylene oxide, preferably C2-C4 alkylene oxide and C8-C 12 It may be a mixture of alkylene oxides having a molar ratio of

[0111] Preferably, component (A) included in the adsorbent (or used in the method of forming the adsorbent) is an alkoxylated polyalkyleneimine. Desirably, the alkoxylated polyalkyleneimine (A) is prepared by the following process: (a) the following ingredients: (i) a polyalkyleneimine, and (ii) alkylene oxide providing a reaction mixture comprising: (b) reacting the polyalkyleneimine (i) with the alkylene oxide (ii) at a temperature of at least 50°C; (c) optionally diluting the product of step (b); and Here, the molar ratio of alkylene oxide to NH of the polyalkyleneimine in the reaction mixture is 0.1 to 0.35, the reaction mixture contains less than 55 mass% of water, preferably less than 30 mass% of water, based on the mass of the reaction mixture, and the reaction mixture contains less than 5 mass% of a polar organic solvent, preferably less than 1 mass% of a polar organic solvent, based on the mass of the reaction mixture.

[0112] Preferably, the alkoxylated polyalkyleneimine (A) is an alkoxylated polyethyleneimine and the polyalkyleneimine (i) in step (a) is polyethyleneimine.

[0113] The alkoxylated polyalkyleneimine (A) in this embodiment is preferably branched.

[0114] Preferably, the polyalkyleneimine (i) in the reaction mixture of step (a) has a mass average molecular weight (M) of 300 to 10000 g / mol, preferably 500 to 1500 g / mol. W )

[0115] The alkylene oxide (ii) used in the reaction mixture of step (a) is preferably a C2-C 12 The alkylene oxide is preferably ethylene oxide, propylene oxide or butylene oxide.

[0116] The inventors have found that adsorbents comprising alkoxylated polyalkyleneimines, in particular alkoxylated polyethyleneimines (wherein the alkoxylated polyalkyleneimines are obtained by the alkoxylation process described above), unexpectedly show particularly improved results for capturing carbon dioxide compared to state-of-the-art alkoxylated polyalkyleneimines.

[0117] Without being limited by theory, the inventors believe that the absence or limited presence of water (i.e., less than 55% water, preferably less than 30% water, based on the mass of the reaction mixture) in compositions prepared by a process in which the alkoxylated polyalkyleneimine component of the adsorbent is free or substantially free (i.e., less than 5%, preferably less than 1%) of polar organic solvents avoids competing side reactions compared to alkoxylating polyalkyleneimine using higher levels of adsorbent. This is believed to significantly improve alkylene oxide consumption. As a result, compositions containing alkoxylated polyalkyleneimine used for loading onto inorganic solid support (B) tend to have lower residual amounts of alkylene oxide. Using alkoxylated polyalkyleneimine with low levels of alkylene is advantageous for product safety in view of the high toxicity of alkylene oxide.

[0118] Therefore, more preferably, the alkoxylated polyalkyleneimine-containing composition used for loading onto the inorganic solid support (B) contains a residual alkylene content of <150 ppm, preferably <50 ppm, more preferably <20 ppm, particularly preferably <10 ppm, and most preferably <5 ppm, based on the mass of the alkoxylated polyalkyleneimine in the composition. The alkylene oxide level can be determined using gas chromatography / mass spectrometry (GC / MS) from Agilent. The system configuration is a Kopplung GC-MS (7890 / 5975 or 7890 / 5977) equipped with an electron ionization source and a single quadrupole spectrometer.

[0119] The alkoxylated polyalkyleneimine composition used to prepare the adsorbent is preferably obtained by a process using a reaction mixture containing less than 3% by weight, often less than 2% by weight, preferably less than 1% by weight, for example less than 7500 ppm, more preferably less than 5000 ppm, particularly preferably less than 1000 ppm, less than 500 ppm, more particularly preferably less than 100 ppm, and particularly preferably less than 50 ppm, of a polar organic solvent, based on the weight of the reaction mixture. Most preferably, the reaction mixture does not contain any polar organic solvent. Furthermore, the reaction mixture preferably contains less than 50% by weight, usually less than 40%, and typically less than 35% of water, based on the weight of the reaction mixture. Preferably, the amount of water in the reaction mixture should be less than 30% by weight of the reaction mixture. Desirably, the amount of water should be less than 20% by weight of the reaction mixture. More preferably, the amount of water in the reaction mixture is even lower, for example less than 15% by weight, preferably less than 12% by weight, more preferably less than 10% by weight, for example less than 5% by weight, based on the weight of the reaction mixture. More preferably, the amount of water present in the reaction mixture should be less than 2% by weight, especially less than 1% by weight, based on the weight of the reaction mixture. Particularly preferably, the reaction mixture should be free of water.

[0120] The reaction of step (b) is desirably initiated by raising the temperature of the reaction mixture. Suitably, the reaction of step (b) can be carried out at a temperature of at least 60°C, more suitably 60°C to 140°C, preferably 75°C to 135°C, more suitably 80°C to 130°C, and even more suitably 80°C to 130°C.

[0121] Preferably, the reaction in step (b) may be carried out in a pressurized reaction vessel, for example at a pressure above 1 bar. Preferably, the reaction is carried out at a pressure above 1.25 bar, preferably at a pressure of from 1.5 bar to 3 bar.

[0122] In the process for obtaining alkoxylated polyalkyleneimines used in the manufacture of adsorbents, the molar ratio of alkylene oxide to NH of the polyalkyleneimine, preferably polyethyleneimine, is 0.1 to 0.35. Preferably, the molar ratio of alkylene oxide to NH is 0.15 to 0.32. NH represents the amine number and is calculated by determining the number of secondary amino groups and primary amino groups, where NH = (number of secondary amino groups) + (2 × (number of primary amino groups)). NH is determined by titrating each polyalkyleneimine with trifluoromethanesulfonic acid.

[0123] The alkoxylated polyalkyleneimine, preferably the alkoxylated polyethyleneimine, preferably has an OH / NH molar ratio of 0.20 to 0.35. The OH / NH ratio is 13 It can be determined using C NMR.

[0124] The adsorbent may contain additional additives, such as polyethylene glycol, surfactants, antioxidants such as salicylic acid, or phosphates. In some cases, polyethylene glycol or surfactants may improve the kinetics of carbon dioxide absorption. Antioxidants may enhance oxidative stability. To prepare such products, such additives can be added to the solid inorganic support (B) before, simultaneously with, or after the addition of the polyalkyleneimine / alkoxylated polyalkyleneimine (A). They may be blended with the polyalkyleneimine / alkoxylated polyalkyleneimine, for example, or these components may be added sequentially. Any additives are typically provided in the form of an aqueous solution. Desirably, such additives may be included in the aqueous solvent used to prepare the adsorbent.

[0125] The adsorbents of the present invention can exhibit highly effective carbon dioxide absorption for a significant period of time, including multiple adsorption / desorption cycles. This is particularly true when an alkoxylated polyalkyleneimine, preferably an alkoxylated polyethyleneimine, is used as the adsorbent component (A). When the adsorbent's adsorption capacity decreases below an acceptable level of adsorption efficiency, the adsorbent can be regenerated by removing the polyalkyleneimine or alkoxylated polyalkyleneimine (A) from the inorganic solid support (B). This can be achieved, for example, by a washing process. The washed inorganic solid support (B) can then be reused by combining it with fresh polyalkyleneimine or alkoxylated polyalkyleneimine (A), preferably using the synthesis techniques described above.

[0126] The adsorbent according to the invention is intended for use in capturing carbon dioxide from a gas mixture (containing carbon dioxide). Thus, what is described is a use in capturing carbon dioxide (i.e., a method of using the adsorbent as defined herein). The capture may be from a gas mixture (containing carbon dioxide). The use may include a subsequent step of desorbing the captured carbon dioxide. Desorption is preferably carried out by heating. Since the product according to the invention has significantly improved oxidative stability, it can be recycled in this manner, preferably multiple times. Optionally, the use may therefore include one or more use cycles (e.g., 2, 3, 4, or 5, etc.), each use cycle including both sorption and subsequent desorption of carbon dioxide.

[0127] Typically, the gas mixture includes air and / or exhaust gases, such as exhaust gases resulting from the combustion of carbonaceous materials. Exhaust gases may be generated by industrial processes, such as carbon-fuel combustion processes, including power plants. Additionally, the gas mixture may also include exhaust gases from a variety of other devices, such as heat-generating devices, including commercial and domestic boilers, or motion-generating devices, such as vehicle combustion engines.

[0128] Capturing carbon dioxide from air typically refers to all atmospheric air, including air in enclosed spaces such as buildings.

[0129] The following examples are intended to illustrate the present invention. [Example]

[0130] Description of methods and materials (i) Silica Mesoporous silica synthesized from sodium silicate was prepared and is shown in Table 1.

[0131] [Table 1]

[0132] The numbers in parentheses indicate the mesoporosity (%). a = Johnson Matthey website. b = Grace website. * = bulk density from mercury intrusion porosimetry. c = from N2 adsorption isotherm at -196 °C.

[0133] The porous silica used herein was prepared by mixing sulfuric acid and sodium silicate under controlled conditions, and then washing, drying, and grinding the resulting amorphous solid. Means for controlling pore structure and particle size to obtain desired results are known to those skilled in the art. The key process variables for controlling pore structure are time, temperature, pH, mixing conditions, and reactant concentration. Further relevant information can be found, for example, in The Chemistry of Silica: Solubility, Polymerization, Colloidal, and Surface Properties of Silica, Biochemistry (R.K. Iler, Wiley, 1979) and Sol-Gel Science: Physics and Chemistry of the Sol-Gel Process (C.J.Brinker and G.W.Scherer, eds., Academic Press, 1990).

[0134] (ii) PEI and alkoxylated PEI (A-PEI) Average molar mass (M W Polyethyleneimine (PEI) of 800 g / mol (PEI1, 99%) and 5000 g / mol (PEI2, 50%) g / mol was synthesized by BASF (Table 2A). Alkoxylated PEIs were prepared with different molecular weights (M W ) by reaction with different alkylene oxides in the absence of solvent or in the presence of methanol or water as solvent, as shown in Table 2B.

[0135] [Table 2]

[0136] Molecular weight was determined by gel permeation chromatography. PEI concentration was determined according to ISO 3251. Bulk density was determined according to DIN 51757 at 20°C. Viscosity was determined according to ISO 2555.

[0137] As used throughout this specification, including the examples, molecular weight, average molecular weight or M W References to the mass average molecular weight (M) in units of g / mol W )

[0138] C The synthetic methods for producing A-PEI1-2 and A-PEI1-12 are shown below. References to amine value in each synthetic description refer to the amine value of the polyethyleneimine before alkoxylation.

[0139] C A-PEI1 A 2 L glass flask equipped with a stirrer and reflux funnel was charged with 465 g of polyethyleneimine (PEI, Mw 800 g / mol, amine value 18.2 mmol / g). The mixture was heated to 30 °C while purging with nitrogen for 20 minutes. 500 g of methanol was added (300 rpm). Maintaining the temperature between 30 and 35 °C, 147.3 g of propylene oxide (PO) was added over 3 hours. The mixture was stirred and gently refluxed at 40 °C overnight. The methanol was then removed within 45 minutes. Finally, the temperature was increased to 80 °C and a 40 mbar vacuum was applied for 15 minutes. The resulting yellowish mixture was quenched with nitrogen and cooled to room temperature (approximately 20 °C), yielding 615 g of a yellowish viscous liquid.

[0140] C A-PEI2 A 2 L glass flask equipped with a stirrer and reflux funnel was charged with 470 g of polyethyleneimine (PEI, Mw 1200 g / mol, amine value 17.9 mmol / g). 115 g of water and 500 g of methanol were added (300 rpm), and the mixture was heated to 30 °C while purging with nitrogen for 20 minutes. While maintaining the temperature at 30-35 °C, 151.5 g of butylene oxide (BuO) was added over 3 hours. The temperature was then increased to 100 °C (90 minutes) while removing methanol and water. The mixture was held at 100 °C for 45 minutes, and then a 40 mbar vacuum was applied for 30 minutes. The resulting yellowish mixture was quenched with nitrogen and cooled to room temperature (approximately 20 °C). 623.9 g of a yellowish viscous liquid was obtained.

[0141] A-PEI1 to 12 of the present invention A-PEI1 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of polyethyleneimine (PEI) (MW 800 g / mol, amine number 18.2 mmol / g). The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 110°C. The reactor was pressurized to 2 bar, and propylene oxide (PO) addition was started with 125 g of PO within 5 minutes. An additional 720 g of PO was added over 3.5 hours while stirring at 150 rpm. The temperature was increased to 120°C and stirring was continued for another 3 hours. The reactor was then cooled to 60°C and depressurized. Finally, the reactor was pressurized at 100 mbar for 20 minutes and purged with nitrogen. 3551 g of a slightly yellowish viscous liquid was obtained.

[0142] A-PEI2 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 800 g / mol, amine number 18.2 mmol / g). The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 110°C. The reactor was pressurized to 2 bar, and propylene oxide addition was started with 125 g of PO within 5 minutes. An additional 700 g of PO was added over 3 hours while stirring at 150 rpm. The temperature was increased to 115°C and stirring was continued for another 3 hours. The reactor was then cooled to 60°C and depressurized. Finally, the reactor was pressurized at 100 mbar for 20 minutes and purged with nitrogen. 3409 g of a slightly yellowish viscous liquid was obtained.

[0143] A-PEI3 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 800 g / mol, amine number 18.2 mmol / g). The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 100 °C. The reactor was pressurized to 2 bar, and butylene oxide (BuO) addition was started with 125 g of BuO within 5 minutes. An additional 760 g of BuO was added over 3 hours while stirring at 150 rpm. The temperature was increased to 115 °C, and stirring was continued for another 4 hours. The reactor was then cooled to 60 °C and depressurized. Finally, the reactor was pressurized at 100 mbar for 20 minutes and purged with nitrogen. 3581 g of a clear, viscous liquid was obtained.

[0144] A-PEI4 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 1200 g / mol, amine number 17.9 mmol / g). The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 100°C. The reactor was pressurized to 2 bar, and propylene oxide (PO) addition was started with 117 g of PO within 5 minutes. An additional 640 g of PO was added over 3 hours while stirring at 150 rpm. The temperature was increased to 115°C and stirring was continued for another 3 hours. The reactor was then cooled to 60°C and depressurized. Finally, the reactor was pressurized at 100 mbar for 20 minutes and purged with nitrogen. 3452 g of a slightly yellowish viscous liquid was obtained.

[0145] A-PEI5 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 1200 g / mol, amine number 17.9 mmol / g). The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 110°C. The reactor was pressurized to 2 bar, and propylene oxide (PO) addition was started with 105 g of PO within 5 minutes. An additional 400 g of PO was added over 2.5 hours while stirring at 150 rpm. The temperature was increased to 115°C and stirring was continued for another 3 hours. The reactor was then cooled to 60°C and depressurized. Finally, the reactor was pressurized at 100 mbar for 20 minutes and purged with nitrogen. 3202 g of a slightly yellowish viscous liquid was obtained.

[0146] A-PEI6 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 1200 g / mol, amine number 17.9 mmol / g) followed by 470 g of water. The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 100. The reactor was pressurized to 2 bar, and propylene oxide (PO) addition was started with 117 g of PO within 5 minutes. An additional 640 g of PO was added over 3.5 hours while stirring at 150 rpm. The temperature was increased to 115°C and stirring was continued for another 3 hours. The reactor was then cooled to 60°C and depressurized. Finally, the reactor was pressurized at 100 mbar for 10 minutes and purged with nitrogen. 3913 g of a slightly yellowish liquid was obtained.

[0147] A-PEI7 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 5000 g / mol, amine number 17.7 mmol / g) followed by 385 g of water. The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 100°C. The reactor was pressurized to 2 bar, and butylene oxide (BuO) addition was started with 129 g of BuO within 5 minutes. An additional 600 g of BuO was charged over 3.5 hours while stirring at 150 rpm. The temperature was increased to 120°C and stirring was continued for another 3 hours. The reactor was then cooled to 60°C and depressurized. Finally, the reactor was pressurized at 100 mbar for 10 minutes and purged with nitrogen. 3799 g of a clear liquid was obtained.

[0148] A-PEI8 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 5000 g / mol, amine number 17.7 mmol / g). The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 100 °C. The reactor was pressurized to 2 bar, and the addition of propylene oxide (PO) was started with 105 g of PO within 5 min. An additional 200 g of PO was added over 1.5 h while stirring at 150 rpm. In the next step, 380 g of butylene oxide (BuO) was charged within 2 h, the temperature was increased to 120 °C, and stirring was continued for another 3 h. The reactor was then cooled to 60 °C and depressurized. Finally, the reactor was pressurized at 100 mbar for 20 min and purged with nitrogen. 3380 g of a clear liquid was obtained.

[0149] A-PEI9 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 1200 g / mol, amine number 17.9 mmol / g). The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was raised to 100 °C. After adding 291 g of 1-decene oxide (DO), the reactor was pressurized to 2 bar. Propylene oxide (PO) was added (648 g) within 3.5 h. The temperature was raised to 115 °C and stirred for another 3 h. The reactor was then cooled to 60 °C and depressurized. Finally, the reactor was pressurized at 100 mbar for 20 min and purged with nitrogen. 3636 g of a slightly yellowish viscous liquid was obtained.

[0150] A-PEI10 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 1200 g / mol, amine number 17.9 mmol / g). The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 100 °C. After adding 201 g of 1-decene oxide (DO), the reactor was pressurized to 2 bar. The addition of butylene oxide (BuO) was carried out within 3.5 h (742 g). The temperature was increased to 115 °C and stirred for an additional 3 h. The reactor was then cooled to 60 °C and depressurized. Finally, the reactor was pressurized at 100 mbar for 20 min and purged with nitrogen. 3640 g of a clear viscous liquid was obtained.

[0151] A-PEI11 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 800 g / mol, amine number 18.2 mmol / g) followed by 590 g of water. The reactor was purged with nitrogen three times while the temperature was increased to 100°C (60 mbar). The reactor was pressurized to 2 bar, and butylene oxide (BuO) addition was started with 152 g of BuO within 5 minutes. An additional 700 g of BuO was added over 3 hours while stirring at 150 rpm. The temperature was increased to 120°C, and stirring continued for another 3.5 hours. The reactor was then cooled to 60°C and depressurized. Finally, the reactor was pressurized at 100 mbar for 10 minutes and purged with nitrogen. 3933 g of a clear liquid was obtained.

[0152] A-PEI12 A 5 L stainless steel reactor equipped with a stirrer was charged with 2700 g of PEI (Mw 5000 g / mol, amine number 17.7 mmol / g) and 375 g of water. The reactor was evacuated (60 mbar) and purged with nitrogen three times while the temperature was increased to 100 °C. After adding 293 g of 1,2-dodecene oxide (DDO), the reactor was pressurized to 2 bar. Propylene oxide (PO) was added (462 g) within 3.5 h. The temperature was increased to 115 °C and stirred for an additional 3 h. The reactor was then cooled to 60 °C and depressurized. Finally, the reactor was pressurized at 200 mbar for 10 min and purged with nitrogen. 3826 g of a slightly yellowish viscous liquid was obtained.

[0153] [Table 3]

[0154] (iii) 1 g scale synthesis of silica-PEI and silica-A-PEI by sequential wet impregnation (laboratory scale) In this section, for the purpose of illustrating the calculations for determining the loading of polyethyleneimine and alkoxylated polyethyleneimine on silica, equation (1) is employed, where the term PEI loading refers to the loading of either polyethyleneimine or alkoxylated polyethyleneimine, respectively, and the term WPEI refers to the mass of polyethyleneimine and alkoxylated polyethyleneimine, respectively.

[0155]

number

[0156] Samples of silica PEI or A-PEI, weighing 1 g on a dry basis, were prepared for laboratory-scale testing. The required amount of silica was combined with the required amount of PEI or A-PEI solution, where solutions were prepared using deionized water to achieve PEI or A-PEI loadings ranging from 10 to 50% by mass. Mixing was performed in a 50 mL beaker with vigorous stirring for 5 minutes. The order of mixing, whether the silica was slowly added to the PEI or A-PEI solution or the solution was added dropwise to the silica, had no apparent effect.

[0157] Examples of masses used for 1 g laboratory-scale samples using 50% w / w solutions with PEI2 and silica1 are shown in Table 3. After mixing, the mixtures were dried for 24 hours at 40 °C in a Gallenkamp Vacuum Oven (SDI Group, UK) at 300 mbar. If the water content exceeded 5 ml per gram of silica, the samples were first dried in a fume hood for 3 days before vacuum drying. In all cases, vacuum drying was performed until the solid powder samples contained 5-6% moisture, thus preparing the claimed adsorbents of the present invention. Water content was measured using a TA Instrument Q500 thermogravimetric analyzer (TGA).

[0158] [Table 4]

[0159] The amount in parentheses indicates the amount when 100% w / w PEI1 (MW 800) was used.

[0160] (iv) Scaling up to 40 kg of silica-PEI by sequential wet impregnation (large-scale testing) In this section, the term PEI refers to both polyethyleneimine-supported silica (silica-PEI) and alkoxylated polyethyleneimine-supported silica (silica-A-PEI) syntheses.

[0161] To scale up silica-impregnated PEI to 40 kg, sequential wet impregnation was performed by making 5 kg sub-batches and repeating this process eight times. For example, to prepare 47% w / w silica-PEI on a dry basis using 50% w / w PEI2, approximately 2.65 kg of silica1 was added to 2.80 kg of deionized water (5.15 kg if using a 100% PEI solution for the loading process) and clamped to a Greaves VS-1 laboratory mixer at 300 rpm until thoroughly mixed (Figure 1). After 30 minutes, 4.70 kg of 50% w / w PEI2 (2.35 kg for 100% PEI) was added in 0.50 kg portions until fully combined (Table 4). The resulting mass of water used was 2.65g to 5.15g (2.8kg silica mixture, 2.35g PEI solution), resulting in a water to silica mass ratio of 1.94:1. Increasing the amount of PEI above 3.00kg (1.5kg) increased the RPM from 300 to 800. The entire mixing process took approximately 4 hours. All 5kg batches were placed in a fume hood for a week to drain off excess water, leaving a clumped powder with 50% moisture, calculated from the mass of the plastic bucket used.

[0162] [Table 5]

[0163] The numbers in parentheses indicate the total mass of water used plus half the mass of the 50% PEI aqueous solution, so the water to silica mass ratios are all close to 1.95.

[0164] (v) Scale-up drying of silica-PEI to 40 kg In this section, the term PEI refers to both polyethyleneimine-supported silica (silica-PEI) and alkoxylated polyethyleneimine-supported silica (silica-A-PEI) syntheses.

[0165] Large-scale vacuum drying was performed using a double-cone vacuum dryer. Because the maximum allowable temperature for the material was 45°C, hot water was used as the heating medium. Approximately 20 kg of silica-PEI (50% moisture) was loaded into the vacuum dryer, and the liquid ring vacuum and hot water boiler were started. The hot water temperature was set to 70-95°C, and the dryer was operated under these conditions for 8 hours each day. This procedure was continued until the final product moisture content was less than 2% (Table 5). Since the moisture content of the adsorbent on the sixth day was less than 2% by mass, this product was not the adsorbent described in product claim 1.

[0166] [Table 6]

[0167] (vi)N2 adsorption isotherm Textural characterization of as-received raw silica, silica-PEI, and silica-A-PEI samples was performed on a Micromeritics ASAP 2420 (Micromeritics Instrument Corp, USA) instrument. Approximately 250 mg of sample was weighed into a sample tube with a filling rod. Prior to analysis, samples were degassed for 15 h at 250 °C for as-received silica or at 50 °C under high vacuum (<0.013 mbar) for PEI-impregnated silica to remove adsorbed moisture and other gases. N2 adsorption isotherms were obtained at -196 °C and 0.01–0.99 relative pressures (P / Po). Specific surface areas were calculated using the BET model over the range of 0.05–0.20 P / Po, resulting in a positive BET "C" parameter. The meso- / macropore volume (<140 nm) and particle size distribution were determined using the BJH model with Broekhoff-de-Boer thickness correction, and the micropore volume was obtained using the DR model.

[0168] (vii) Measurement of absolute silica-PEI / silica-A-PEI loading The loading of PEI / A-PEI was determined by analyzing the samples with a thermogravimetric analyzer (TGA) (TGA Q500, TA Instruments Inc, New Castle, DE, USA). Silica and silica-PEI / silica-A-PEI samples (25–30 mg) were heated to 110 °C at a heating rate of 30 °C / min in N2 (1 bar, 100 mL / min) and held for 15 min to remove moisture. After cooling to 80 °C, the samples were heated to 800 °C at a heating rate of 30 °C / min in air (1 bar, 100 mL / min) and equilibrated at 800 °C for an additional 15 min. The mass loss between 200 and 600 °C was used to calculate the loading in wt% on a dry basis.

[0169] (viii) Carbon dioxide (CO2) adsorption and adsorption rate (kinetics) The CO2 adsorption capacity of silica-PEI / silica-A-PEI samples was measured using a TGA (TGA Q500, TA Instruments Inc, New Castle, DE, USA). Approximately 20–25 mg of silica and silica-PEI / silica-A-PEI-impregnated samples were preheated to 110 °C for 30 min and equilibrated in N2 (1 bar, 100 mL / min) to remove adsorbed water. The sample was then cooled to the optimal adsorption temperature and equilibrated. At this stage, the gas was switched to 15% CO2 equilibrated with N2 (1 bar, 100 mL / min) and held for 60 min to obtain the equilibrated CO2 capacity. A 75 °C adsorption temperature was used for PEI1 (MW 800) and PEI2 (MW 5000). The optimal adsorption temperature for alkoxylated PEI ranged from 25 to 70 °C, depending on the degree of alkoxylation. The adsorption capacity on a dry basis was calculated by measuring the mass change after the drying step under 15% CO2 gas. In addition to measuring the CO2 adsorption capacity, adsorption kinetics were calculated by measuring the time to reach 90% and 95% of the equilibrium CO2 capacity (t90 and t95) after 60 min. Additionally, the amount adsorbed after 2 min was also recorded for comparison with the fluidized adsorption rate.

[0170] (ix) Stability / oxidation testing Oxidation tests of silica-PEI / silica-A-PEI were performed at 80 °C for 10 days in a 60 L Lab Pro fan-assisted oven (Scientific Laboratory Supplies, UK). Approximately 0.6 g of sample was weighed into a 50 mL beaker and evenly dispersed to ensure complete air exposure. On days 1, 3, 5, 7, and 10, approximately 50 mg of sample was removed and analyzed immediately, with minimal contact with humid laboratory conditions. The equilibrium CO2 adsorption capacity (in 15% CO2) of the oxidized sample after 60 min was obtained at the optimal temperature for the specific PEI / A-PEI and compared with the initial sample (or day 0) to determine the degree of oxidation.

[0171] result (i) Laboratory synthesis of silica-PEI / silica-A-PEI and the amount of water used Laboratory synthesis of silica-PEI / silica-A-PEI was used to develop a method that can be scaled up to 40 kg batch preparation and then to ton production levels. For 100% PEI / A-PEI, 1 g of silica is used in combination with 1.95 g of deionized water, which translates to 78 kg at the 40 kg scale (Table 6).

[0172] As described herein, it may be procedurally advantageous to ensure that the total amount of water used does not exceed the total pore volume of the silica.

[0173] Silica 1 is primarily mesoporous, and impregnation of PEI into silica 1 occupies both mesopores and narrow macropores. The mesopore volume of PEI1 and PEI2 decreased by 93% and 90%, respectively, from zero to 50% loading, ultimately resulting in N2 adsorption at -196 °C (Table 7, Figures 2 and 3). Particle aggregation was observed to occur at loadings of 50% for both PEI1 and PEI2. Loadings greater than 50% result in sticky powders with undesirable handling characteristics due to excessive aggregation, making them unsuitable for commercial adsorbent use. In desirable embodiments of the adsorbents of the present invention, PEI does not exceed 50% by mass on a dry basis relative to the total mass of the adsorbent. Between loadings of 45 and 47%, 13% of the total pore volume remains for both PEI1 and PEI2, suggesting that these pores serve as diffusion pores for CO2 to reach the amine functional groups within the pores. At loadings above 50% PEI, the PEI-silica samples aggregate and become very sticky at higher loadings. At 50% loading, 7-10% of the total pore volume remains for both PEI1 and PEI-impregnated samples, and this small pore volume can affect adsorption and desorption kinetics. Similar pore volume reductions are observed for other silicas.

[0174] [Table 7]

[0175] The number in parentheses indicates the mass of water equivalent to that when a 100% w / w PEI1 solution is used.

[0176] [Table 8]

[0177] BET SA = BET specific surface area at a relative pressure of 0.05-0.20. Total pore volume = 0-140 nm, using the BJH model (Broekhoff-de-Boer thickness correction) + DR model for microporosity. Average pore diameter = 4V / A (4 × total pore volume / specific surface area, then converted to nm).

[0178] (ii) CO2 uptake by unmodified PEI

[0179] [Table 9]

[0180] [Table 10]

[0181] Example 1: Effect of PEI loading on oxidation resistance on laboratory scale Silica 1 was sequentially wet impregnated with 30, 35, 40, 43, 45, 47 and 50% w / w of PEI2 on a dry basis to compare oxidative stability, where example masses used are shown in Table 10.

[0182] [Table 11]

[0183] The number in parentheses is the total mass of water used, plus the water from the 50% PEI solution.

[0184] Oxidation studies of silica-PEI samples were carried out at increasing PEI loadings at 70 and 80 °C using a fan-assisted oven, with 20–25 mg samples taken on days 1, 3, 5, 7, and 10. CO performance tests were carried out using a TGA at an adsorption temperature of 75 °C with 15% CO (1 bar, 100 ml / min) balanced with N (Figure 8).

[0185] Figure 8 shows that the CO2 capacity of 30% w / w PEI2 loadings decreased by 56% after 10 days of oxidation at 80 °C. At 40% w / w, the decrease was only 54%, and at 47% w / w, the decrease was only 52%. Figure 9 highlights the difference between 40% w / w and 47% w / w loadings at a lower oxidation temperature of 70 °C. At 40% w / w PEI2 loading, the CO2 capacity decreased by 47% after 20 days of oxidation, while at 47% w / w, the decrease was only 20%. The BET results in Table 11 confirm that for the silica 1 studied here, the pore volume for air ingress decreases as the loading exceeds 40% to reach the maximum possible loading of 50% w / w.

[0186] [Table 12]

[0187] BET SA = BET specific surface area at a relative pressure of 0.05-0.20. Total pore volume = 0-140 nm, using the BJH model (Broekhoff-de-Boer thickness correction) + DR model for microporosity. Average pore diameter = 4V / A (4 × total pore volume / specific surface area, then converted to nm).

[0188] In conclusion, this example demonstrates that to maximize oxidative stability, it is highly desirable for PEI to occupy substantially all of the pore volume at the highest possible loading, thereby increasing the density of the PEI layer and reducing the rate of air ingress.

[0189] Example 2: Minimizing vacuum drying time to maintain PEI integrity in large-scale preparations Silica 1 was sequentially wet-impregnated with 47% w / w PEI2 (MW 5000 g / mol). Silica 1 was premixed with water to prepare two 5 kg batches. Approximately 2.65 kg of silica 1 was mixed with 2.80 kg of water using a Greaves VS-1 laboratory mixer at 300 rpm (Figure 1). Next, 4.70 kg of the 50% PEI2 solution was added. As the amount of PEI was increased to 3.00 kg (over 1.5 kg), the rpm was increased from 300 to 800. The silica-PEI batches were placed in a fume hood for 1 week to drain off excess water, leaving a cohesive powder with a 50 w / w moisture content. Each batch weighed approximately 10 kg.

[0190] Vacuum drying was performed using a double-cone vacuum dryer. Because the maximum allowable temperature for the material was 45°C, hot water was used as the heating medium. Approximately 5 kg of silica-PEI (50% moisture) was loaded into the vacuum dryer, and the liquid ring vacuum and hot water boiler were started. The hot water temperature was set to 70-95°C, and the dryer was operated under these conditions for 8 hours each day. This procedure was repeated daily to obtain various products with moisture contents of less than 2% w / w (Table 12). The sample obtained after 6 days, which had a moisture content of 1.9% by weight (i.e., less than 2% by weight) as measured by TGA, is therefore a reference sample without the adsorbent described in product claim 1.

[0191] [Table 13]

[0192] The CO2 adsorption capacity of a 5 kg silica 1PEI2 sample was measured using TGA as described in Methods and Materials. For PEI2 (molecular weight 5000 g / mol), an optimal adsorption temperature of 75 °C was used (Figure 11). In addition to measuring the CO2 adsorption capacity on a dry basis, adsorption kinetics was calculated by determining the time to reach 90% and 95% of the equilibrium CO2 capacity after 60 min (t90 and t95) (Table 13). Oxidative stability was determined at 80 °C as described in Methods and Materials, where 20–25 mg samples were taken over 10 days (Figure 12) and analyzed for changes in CO2 uptake performance by TGA.

[0193] [Table 14]

[0194] In conclusion, this example demonstrates that a sorbent sample according to the present invention containing 4.5% moisture content exhibited significantly improved performance characteristics compared to a reference sample dried to less than 2% moisture by weight. While the adsorption rate (kinetics) was similar between samples, the equilibrium CO2 capacity of the reference sample decreased by 5.0%, presumably due to degradation of the polyethyleneimine upon prolonged heating. Furthermore, the oxidative stability of the reference sample decreased dramatically, with only 8% uptake remaining according to the test conditions, whereas the sample according to the present invention (4.5% moisture content) retained 47% CO2 uptake.

[0195] This demonstrates that the adsorbent of the present invention as defined in product claim 1 has important and unexpected advantages over the current state of the art in this field.

[0196] Example 3: Effect of low to high water weight on wet PEI impregnation of silica The effect of the mass or volume of deionized water on the sequential wet impregnation of PEI and silica was investigated on a 1 g scale (dry basis) using both PEI1 and PEI2, and silica 1. Considering the CO2 uptake and adsorption rates of PEI, a PEI loading of 47% w / w was selected as the optimal loading for silica 1. The masses of water and PEI used to prepare the mixture of silica 1 with PEI1 and 2 are shown in Tables 14a and 14b.

[0197] [Table 15]

[0198] The number in parentheses is the total mass of water used per gram of silica, plus the water from the 50% PEI solution.

[0199] [Table 16]

[0200] The number in parentheses is the total mass of water used per gram of silica, including the water from the 99% PEI solution.

[0201] The equilibrium CO2 adsorption capacities of the silica 1-PEI2 and silica 1-PEI1 samples are shown in Figures 15a and 15b. The adsorption kinetics were calculated by measuring the mass change on a dry basis under 15% CO2 gas and determining the time to reach 90% and 95% of the equilibrium CO2 capacity (t90 and t95) after 60 min (Table 15a and 15b). The results show that the CO2 adsorption capacity does not decrease when the mass of added water is increased from 10 g to 1 g, where 1 g of water corresponds to 2 g of total water, including the water added to the 50% PEI solution. Furthermore, when the 1 g of water in the 50% PEI solution is included, neat PEI1 achieves acceptable performance with only 0.5 g of water. The decrease in performance of the neat sample demonstrates the benefit of adding water to the solution.

[0202] [Table 17]

[0203] [Table 18]

[0204] In conclusion, this example demonstrates that using low levels of deionized water in the preparation of PEI-silica does not adversely affect adsorption kinetics or performance. When scaling up to 5 kg or larger quantities, the amount of water saved by reducing the water content according to the method herein is substantial, considering the cost and time required to dry samples to remove excess water, which typically reaches 5% w / w in silica-PEI products.

[0205] Example 4: Effect of silica particle size on wet sequential impregnation of PEI The effect of particle size (or dry dispersion size) on the sequential wet impregnation of PEI with silica was investigated on a 1 g scale (dry basis) using silicas 1-4 with D(50) particle sizes ranging from 0.1 to 3 mm and commercial silica (Table 1). The higher molecular weight and viscosity of PEI, 2 (50% w / w solution), and the minimum amount of deionized water were related to the bulk density and particle size of the particular silica. To investigate the loading effect of each silica, samples with various loadings were prepared.

[0206] The equilibrium CO adsorption capacities of silicas 1-2 and commercial silicas impregnated with PEI2 (50% w / w solution) were measured by TGA as described in the Methods and Materials section. The results for the six silicas investigated (Table 1) are shown in Figures 13-18 and Tables 16-21.

[0207] [Table 19]

[0208] [Table 20]

[0209] [Table 21]

[0210] [Table 22]

[0211] [Table 23]

[0212] [Table 24]

[0213] These examples demonstrate that aqueous impregnation can be used to impregnate silicas ranging in particle size from less than 0.1 mm to 3.0 mm using minimal amounts of water, and that adsorbents retaining moisture levels above 2% by weight of the adsorbent mass exhibit similar CO2 adsorption efficiencies but improved oxidative stability compared to samples with lower moisture contents. The optimal PEI loading and adsorption kinetics for each silica depend on the total pore volume (or mesoporosity) combined with the particle size range.

[0214] Example 5: CO2 adsorption properties of silica-alkoxylated PEI (silica-A-PEI) Silica-A-PEI was prepared using comparative alkoxylated PEIs (Comparative A-PEIs 1-2) and alkoxylated PEIs (A-PEIs 1-12) shown in Table 2B, and silicas 1-3 shown in Table 1, employing procedures (iii) and (iv) of the "Methods and Materials Description" section, but employing drying procedure (v). The silica-A-PEI adsorbents used in this manner had a water content of approximately 5-6% by weight. C A-PEI1 and C A-PEI2 were prepared using the methanol preparation process described above, so the comparative synthetic method is the aqueous method of the present invention described herein.

[0215] The loading of alkoxylated PEI on silica was determined by the method of (vii), the carbon dioxide adsorption and adsorption rate and (kinetics) were established according to (viii), and the stability / oxidation test was carried out according to (ix) in the Methods and Materials section. The results are shown in Tables 22 and 23.

[0216] [Table 25]

[0217] [Table 26]

[0218] The results showed that silica-A-PEI products based on alkoxylated polyethyleneimine prepared in the absence of organic solvents, or in the absence of solvent or in the presence of some water, showed significantly improved carbon dioxide capture compared to silica-A-PEI products based on alkoxylated polyethyleneimine prepared in the presence of methanol.

Claims

1. (A) a polyalkyleneimine or an alkoxylated polyalkyleneimine; and (B) an inorganic solid support for the polyalkyleneimine or alkoxylated polyalkyleneimine (A); 1. An adsorbent suitable for absorbing carbon dioxide from a gas mixture, comprising: the polyalkyleneimine or alkoxylated polyalkyleneimine (A) is disposed on the inorganic solid support (B); The adsorbent comprises water in an amount greater than 2 wt. % based on the total weight of the adsorbent.

2. 2. The adsorbent of claim 1, containing less than 50 ppm of methanol, optionally less than 50 ppm of a polar organic solvent, preferably less than 50 ppm of an organic solvent.

3. 3. The adsorbent according to claim 1, wherein the polyalkyleneimine or alkoxylated polyalkyleneimine (A) is polyethyleneimine or alkoxylated polyethyleneimine.

4. 3. The adsorbent according to claim 1, wherein the inorganic solid carrier (B) has a pore volume of 0.7 to 2.0 ml / g.

5. 3. The adsorbent according to claim 1, wherein the inorganic solid support has a mass median particle size of at least 0.1 mm, preferably 0.1 to 5 mm.

6. 3. The adsorbent according to claim 1 or 2, wherein the inorganic solid support is porous silica, optionally selected from silica gel or precipitated silica.

7. 3. The adsorbent of claim 1, wherein the alkoxylated polyalkyleneimine has an OH / NH molar ratio of 0.20 to 0.

35.

8. 3. The adsorbent according to claim 1 or 2, wherein the amount of the polyalkyleneimine or alkoxylated polyalkyleneimine (A) in the adsorbent is at least 40% by weight, optionally from 40% to 60% by weight, more preferably from 47% to 55% by weight, based on the weight of the inorganic solid support (B).

9. 3. The adsorbent according to claim 1 or 2, which is produced by combining 2 ml or less of an aqueous solvent per 1 g of the inorganic solid carrier (B).

10. (A) is a process comprising the following steps: (a) the following components: (i) a polyalkyleneimine, and (ii) alkylene oxide providing a reaction mixture comprising: (b) reacting said polyalkyleneimine (i) with said alkylene oxide (ii) at a temperature of at least 50°C; (c) optionally diluting the product of step (b); an alkoxylated polyalkyleneimine obtainable by a process comprising:

3. The adsorbent according to claim 1 or 2, wherein the molar ratio of alkylene oxide to NH of the polyalkyleneimine in the reaction mixture is from 0.1 to 0.35, the reaction mixture comprises less than 55% by weight of water, preferably less than 30% by weight of water, based on the weight of the reaction mixture, and the reaction mixture comprises less than 5% by weight, preferably less than 1% by weight of a polar organic solvent, based on the weight of the reaction mixture.

11. 11. The adsorbent according to claim 10, having a residual alkylene oxide content of less than 150 ppm, preferably less than 50 ppm, more preferably less than 20 ppm, particularly preferably less than 10 ppm, and most preferably less than 5 ppm, based on the weight of the alkoxylated polyalkyleneimine in the composition.

12. 11. The adsorbent of claim 10, wherein the alkoxylated polyalkyleneimine (A) is an alkoxylated polyethyleneimine, and the polyalkyleneimine (i) in step (a) is polyethyleneimine.

13. 11. The adsorbent of claim 10, wherein the reaction mixture comprises less than 20% water by weight, more preferably less than 10% water by weight, based on the weight of the reaction mixture.

14. The adsorbent of claim 10 , wherein the reaction mixture does not contain a polar organic solvent.

15. 11. The adsorbent of claim 10, wherein the molar ratio of alkylene oxide to NH of polyalkyleneimine in the reaction mixture is 0.15 to 0.

32.

16. The alkylene oxide is C ２ ~C １２ 11. The adsorbent according to claim 10, which is an alkylene oxide, preferably ethylene oxide, propylene oxide or butylene oxide.

17. The polyalkyleneimine in the reaction mixture has a weight average molecular weight (M Ｗ 11. The adsorbent of claim 10, wherein

18. 11. The adsorbent of claim 10, wherein the alkoxylated polyalkyleneimine is branched.

19. 10. A method for preparing the adsorbent of claim 1, comprising: A step of supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting step comprising contacting (A) with (B) in the presence of an aqueous solvent, and then obtaining an adsorbent. A method comprising:

20. 20. The method of claim 19, wherein the supported mixture is provided by contacting (A) and (B) in the presence of an aqueous solvent, wherein the weight ratio of aqueous solvent to inorganic support (B) in the supported mixture does not exceed 5:1; optionally, the weight ratio of aqueous solvent to inorganic support (B) in the supported mixture does not exceed 1.5:1; and optionally, the weight ratio of aqueous solvent to inorganic support (B) in the supported mixture does not exceed 0.5:

1.

21. 20. The method of claim 19, wherein the total volume of liquid in the loading mixture does not exceed 2 ml of liquid per gram of inorganic solid support (B).

22. 20. The method of claim 19, wherein the aqueous solvent comprises less than 50 ppm of methanol, optionally less than 50 ppm of a polar organic solvent, preferably less than 50 ppm of an organic solvent, based on the weight of the aqueous solvent, preferably wherein the aqueous solvent is water.

23. a step of supporting a polyalkyleneimine or alkoxylated polyalkyleneimine (A) on an inorganic solid support (B), the supporting step comprising contacting (A) with (B) in the presence of an aqueous solvent to provide a resulting supported mixture; 1. A method for preparing an adsorbent suitable for absorbing carbon dioxide from a gas mixture, comprising: the weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture is not more than 5:1; The method further comprises obtaining an adsorbent from the supported mixture, the adsorbent comprising a polyalkyleneimine or alkoxylated polyalkyleneimine (A) supported on an inorganic solid support (B).

24. 24. The method of claim 23, wherein the resulting adsorbent product is that of claim 1 or 2.

25. 24. The method of claim 23, wherein the weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture does not exceed 3:1, and optionally the weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture does not exceed 2:1; optionally the weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture does not exceed 1.5:1; optionally the weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture does not exceed 1:1; optionally the weight ratio of the aqueous solvent to the inorganic carrier (B) in the support mixture does not exceed 0.5:

1.

26. 24. The method of claim 23, wherein the ratio of the total mass of liquid in the support mixture to the mass of inorganic support (B) in the support mixture does not exceed 10:

1.

27. 24. The method of claim 23, wherein the aqueous solvent comprises less than 50 ppm methanol, optionally less than 50 ppm polar organic solvent, preferably less than 50 ppm organic solvent, based on the weight of the aqueous solvent, preferably the aqueous solvent is water.

28. 24. The method of claim 23, wherein the weight ratio of water to inorganic support (B) in the support mixture is at least 0.2:

1.

29. 24. The method according to claim 23, wherein the total volume of the aqueous solvent used does not exceed 80% of the total pore volume of the inorganic support (B).

30. 20. The adsorbent according to claim 1, or obtainable by the method according to claim 19, wherein the adsorbent comprises the polyalkyleneimine or alkoxylated polyalkyleneimine (A) in an amount of 10% to 70% by weight, relative to the total weight of the adsorbent.

31. 10. A method of using the sorbent of claim 1 for capturing carbon dioxide.

32. 20. Use of the sorbent obtained or obtainable by the method of claim 19 for capturing carbon dioxide.

33. 33. The use for capturing carbon dioxide according to claim 31 or 32, optionally wherein the gas mixture is selected from air or exhaust gases, such as exhaust gases from the combustion of carbonaceous materials.

34. 34. The use of claim 33, wherein the exhaust gas is generated by any of the activities selected from the group consisting of an industrial process, a heat generating device, and a motion generating device.

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