BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an aminated magnesium oxide adsorbent, particularly a magnesium oxide-polyamine adsorbent, methods of making the aminated magnesium oxide adsorbent, and methods of capturing carbon dioxide (CO2) with the aminated magnesium oxide adsorbent.

Discussion of the Background

The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.

Global warming is a serious problem facing human civilization. An increase in the average Earth temperature by even a few degrees might lead to the melting of the polar ice caps, a significant increase in the water level of oceans and seas and, thus, the submerging of some islands and coastal cities. The predicted increase in the average Earth temperature in this century is about 1.5° C. if the emissions of greenhouse gases continue at their current rates. See G. Gómez-Pozuelo, E. S. Sanz-Pérez, A. Arencibia, P. Pizarro, R. Sanz, D. P. Serrano, CO2adsorption on amine-functionalized clays, Microporous and Mesoporous Materials, 282 (2019) 38-47, incorporated herein by reference in its entirety. Despite these consequences, carbon dioxide (CO2) emissions continue to rise. The current CO2concentration in the atmosphere is about 410 ppm compared to about 300 ppm in the middle of the twentieth century. The average annual increase in the atmospheric level of CO2in the past few decades has been estimated to be about 2 ppm, which is an alarming CO2accumulation rate in the atmosphere. See M. Fasihi, O. Efimova, C. Breyer, Techno-economic assessment of CO2direct air capture plants, Journal of Cleaner Production, 224 (2019) 957-980, incorporated herein by reference in their entirety. Thus, CO2capture and sequestration is a key area of research.

A number of processes have been developed and utilized for CO2capture; the most common one is CO2absorption into an aqueous solution of a suitable amine(s). Among these, adsorption by amine solutions such as monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA) are most common. See P. J. G. Huttenhuis, N. J. Agrawal, J. A. Hogendoorn, G. F. Versteeg, Gas solubility of H2S and CO2in aqueous solutions of N-methyldiethanolamine, Journal of Petroleum Science and Engineering, 55 (2007) 122-134; H. Zare Aliabad, S. Mirzaei, Removal of CO2and H2S using Aqueous Alkanolamine Solutions, World Academy of Science, Engineering and Technology, 3 (2009) 50-59; E. B. Rinker, S. S. Ashour, O. C. Sandall, Absorption of carbon dioxide into aqueous blends of diethanolamine and methyldiethanolamine, Industrial & engineering chemistry research, 39 (2000) 4346-4356; C. H. Yu, C. H. Huang, C. S. Tan, A Review of CO2Capture by Absorption and Adsorption, Aerosol and Air Quality Research, 12 (2012) 745-769; and A. A. Olajire, CO2capture and separation technologies for end-of-pipe applications energy 35 (2010) 2610-2628, each incorporated herein by reference in their entirety. However, this process is corrosive, energy-intensive, and utilizes environmentally unfriendly amines. Accordingly, several alternatives such as cryogenic distillation, adsorption, membrane separation, and biological processes (e.g., microbial treatment) have been sought. See K. Maqsood, A. Mullick, A. Ali, K. Kargupta, S. Ganguly, Cryogenic carbon dioxide separation from natural gas: A review based on conventional and novel emerging technologies, Reviews in Chemical Engineering, 30 (2014) 453-477; H. Bamdad, K. Hawboldt, S. MacQuarrie, A review on common adsorbents for acid gases removal: Focus on biochar, Renewable and Sustainable Energy Reviews, 81 (2018) 1705-1720; F. D. Lamari, P. Langlois, M. Dicko, C. Chile, C. Chilev, I. Pentchev, Carbon dioxide capture by adsorption, Journal of Chemical Technology and Metallurgy, 51 (2016) 609-626; G. George, N. Bhoria, S. AlHallaq, A. Abdala, V. Mittal, Polymer membranes for acid gas removal from natural gas, Separation and Purification Technology, 158 (2016) 333-356; B. Belaissaoui, E. Favre, Membrane Separation Processes for Post-Combustion Carbon Dioxide Capture: State of the Art and Critical Overview, Oil Gas Sci. Technol.—Rev. IFP Energies nouvelles, 69 (2014) 1005-1020; and S. Choi, J. H. Drese, C. W. Jones, Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources, ChemSusChem, 2 (2009) 796-854, each incorporated herein by reference in their entirety. Among these, adsorption is most attractive due to its simplicity, low energy requirements, and ease of adsorbent regeneration/reuse.

Despite the above attractive characteristics of adsorption, many known adsorbents (e.g., amines) underperform in terms of CO2adsorption capacity, energy consumption for regeneration, corrosive properties, and mass losses during use, making them less appealing to industry. Research has thus focused on developing new solid adsorbents for CO2capture with higher CO2adsorption capacity. Generally, most of the developed adsorbents are microporous/mesoporous silica, carbon-based adsorbents, metal oxides, and metal-organic frameworks (MOFs). See X. Liu, J. Li, L. Zhou, D. Huang, Y. Zhou, Adsorption of CO2, CH4and N2on ordered mesoporous silica molecular sieve, Chemical Physics Letters, 415 (2005) 198-201; S.-H. Liu, Y.-C. Lin, Y.-C. Chien, H.-R. Hyu, Adsorption of CO2 from Flue Gas Streams by a Highly Efficient and Stable Aminosilica Adsorbent, Journal of the Air & Waste Management Association, 61 (2011) 226-233; M. M. Maroto-Valer, Z. Tang, Y. Zhang, CO2capture by activated and impregnated anthracites, Fuel Processing Technology, 86 (2005) 1487-1502; M. C. Castrillon, K. O. Moura, C. A. Alves, M. Bastos-Neto, D. C. S. Azevedo, J. Hofmann, J. Möllmer, W.-D. Einicke, R. Glaser, CO2and H2S Removal from CH4-Rich Streams by Adsorption on Activated Carbons Modified with K2CO3, NaOH, or Fe2O3, Energy & Fuels, 30 (2016) 9596-9604; L. Li, X. Wen, X. Fu, F. Wang, N. Zhao, F. Xiao, W. Wei, Y. Sun, MgO/Al2O3Sorbent for CO2Capture, Energy & Fuels, 24 (2010) 5773-5780; A. Hakim, T. S. Marliza, N. M. Abu Tahari, R. W. N. Wan Isahak, R. M. Yusop, W. M. Mohamed Hisham, A. M. Yarmo, Studies on CO2Adsorption and Desorption Properties from Various Types of Iron Oxides (FeO, Fe2O3, and Fe3O4), Industrial & Engineering Chemistry Research, 55 (2016) 7888-7897; T. Remy, S. A. Peter, S. Van der Perre, P. Valvekens, D. E. De Vos, G. V. Baron, J. F. M. Denayer, Selective Dynamic CO2Separations on Mg-MOF-74 at Low Pressures: A Detailed Comparison with 13X, The Journal of Physical Chemistry C, 117 (2013) 9301-9310; and S. Couck, J. F. M. Denayer, G. V. Baron, T. Rémy, J. Gascon, F. Kapteijn, An Amine-Functionalized MIL-53 Metal—Organic Framework with Large Separation Power for CO2and CH4, Journal of the American Chemical Society, 131 (2009) 6326-6327, each incorporated herein by reference in their entirety. Although these adsorbents show promising results, most of them require high pressure or temperature to function effectively. See S. Choi, J. H. Drese, C. W. Jones, Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources, ChemSusChem, 2 (2009) 796-854, incorporated herein by reference in its entirety. Moreover, some of these adsorbents are non-regenerable or require prohibitively high regeneration energy. See S. Kumar, S. K. Saxena, A comparative study of CO2sorption properties for different oxides, Materials for Renewable and Sustainable Energy, 3 (2014) 1-30, incorporated herein by reference in its entirety.

For example, U.S. Pat. No. 5,087,597A discloses a method for the capture of CO2using a silica gel adsorbent with a maximum CO2uptake capacity at ambient conditions of 19.6 mg/g.

U.S. Pat. No. 5,876,488A discloses the synthesis of an amine supported on AMBERLITE and its use for CO2adsorption, for example to reduce the partial pressure of CO2in a gas phase mixture to about 1 mm Hg.

U.S. Pat. No. 5,492,683 discloses a method for preparing a CO2adsorbent containing 11 wt. % polyethyleneimine, 16 wt. % triethylene glycol, and 73 wt. % AMBERLITE XAD-7, with a CO2adsorption capacity at 50° C. of about 40 mg/g.

U.S. Pat. No. 4,810,266A discloses a method for CO2adsorption using aminated carbon molecular sieves that have been treated with alkanolamines, with the best adsorbent providing a maximum CO2uptake capacity of below 70 mg/g.

U.S. Pat. No. 7,795,175B2 discloses a method for amine and polyamine grafting on a fumed silica surface, with the adsorbents providing CO2adsorption capacities of up to 105 mg/g.

U.S. Pat. No. 6,908,497B1 discloses a method for preparing dry amine- and/or alcohol-based composites of anhydrous calcium sulfate (CaSO4), and other materials such as silica (SiO2) and alumina (Al2O3) having maximum CO2adsorption capacities of roughly 35 mg/g at ambient conditions.

As alternatives to the above-mentioned adsorbents, metal oxides and metal salts such as CaO, Li4SiO4, and MgO have also been used for CO2adsorption. See A. M. Kierzkowska, R. Pacciani, C. R. Müller, CaO-Based CO2Sorbents: From Fundamentals to the Development of New, Highly Effective Materials, ChemSusChem, 6 (2013) 1130-1148; H. Lu, E. P. Reddy, P. G. Smirniotis, Calcium Oxide Based Sorbents for Capture of Carbon Dioxide at High Temperatures, Industrial & Engineering Chemistry Research, 45 (2006) 3944-3949; R. Quinn, R. J. Kitzhoffer, J. R. Hufton, T. C. Golden, A High Temperature Lithium Orthosilicate-Based Solid Absorbent for Post Combustion CO2Capture, Industrial & Engineering Chemistry Research, 51 (2012) 9320-9327; and A. Hanif, S. Dasgupta, A. Nanoti, Facile Synthesis of High-Surface-Area Mesoporous MgO with Excellent High-Temperature CO2Adsorption Potential, Industrial & Engineering Chemistry Research, 55 (2016) 8070-8078, each incorporated herein by reference in their entirety. Although these metallic adsorbents can function well at atmospheric pressure, they are typically only effective at relatively high temperatures. High operating temperatures in some cases can cause a severe structural deformation of the adsorbents, deteriorating their adsorption capability upon extended use. See A. M. Kierzkowska, R. Pacciani, C. R. Müller, CaO-Based CO2Sorbents: From Fundamentals to the Development of New, Highly Effective Materials, ChemSusChem, 6 (2013) 1130-1148; and G. S. Grasa, J. C. Abanades, CO2Capture Capacity of CaO in Long Series of Carbonation/Calcination Cycles, Industrial & Engineering Chemistry Research, 45 (2006) 8846-8851, each incorporated herein by reference in their entirety. In addition to the above limitations, metal oxide adsorbents require high regeneration temperatures, increasing energy consumption and, thus, the increased operational costs for the adsorption process. See. Kumar, S. K. Saxena, A comparative study of CO2sorption properties for different oxides, Materials for Renewable and Sustainable Energy, 3 (2014) 1-30, incorporated herein by reference in its entirety. Moreover, the formation of metal carbides through the reaction between CO2and the metal oxides at high regeneration temperatures makes regeneration a very challenging task. See H. Lu, E. P. Reddy, P. G. Smirniotis, Calcium Oxide Based Sorbents for Capture of Carbon Dioxide at High Temperatures, Industrial & Engineering Chemistry Research, 45 (2006) 3944-3949, incorporated herein by reference in its entirety.

For example, U.S. Pat. No. 9,370,743B2 discloses a method for the synthesis of a barium titanate composite adsorbent for CO2capture. The adsorbent could not adsorb more than 50 mg/g CO2at ambient conditions, but increasing the adsorption temperature to 200-550° C. improved the CO2adsorption capability.

Magnesium oxide has been used in combination with metal salts as an adsorbent for CO2at high temperatures, and also for other purposes, such as remediation of toxic pollutants and as a catalyst support in a number of reactions. See G. Xiao, R. Singh, A. Chaffee, P. Webley, Advanced adsorbents based on MgO and K2CO3for capture of CO2at elevated temperatures, International Journal of Greenhouse Gas Control, 5 (2011) 634-639; X. Zhao, G. Ji, W. Liu, X. He, E. J. Anthony, M. Zhao, Mesoporous MgO promoted with NaNO3/NaNO2for rapid and high-capacity CO2capture at moderate temperatures, Chemical Engineering Journal, 332 (2018) 216-226; J. Hu, Z. Song, L. Chen, H. Yang, J. Li, R. Richards, Adsorption Properties of MgO(111) Nanoplates for the Dye Pollutants from Wastewater, Journal of Chemical & Engineering Data, 55 (2010) 3742-3748; J. H. Lunsford, P. Qiu, M. P. Rosynek, Z. Yu, Catalytic Conversion of Methane and Ethylene to Propylene, The Journal of Physical Chemistry B, 102 (1998) 167-173; and D. Szmigiel, W. Raróg-Pilecka, E. Miśkiewicz, M. Gliński, M. Kielak, Z. Kaszkur, Z. Kowalczyk, Ammonia synthesis over ruthenium catalysts supported on high surface area MgO and MgO—Al2O3systems, Applied Catalysis A: General, 273 (2004) 105-112, each incorporated herein by reference in their entirety.

However, there is still a need for new MgO-based adsorbents for CO2capture technologies that are effective at ambient conditions.

SUMMARY OF THE INVENTION

Accordingly, it is one object of the present invention to provide an aminated magnesium oxide adsorbent, containing (i) a magnesium oxide matrix having disordered mesopores and a BET surface area of 320 to 380 m2/g, and (ii) a polyamine selected from the group consisting of an ethyleneamine having a molecular weight of up to 450 g/mol and a polyethylene imine having a number average molecular weight of greater than 500 g/mol and up to 20,000 g/mol, wherein the polyamine is impregnated within the disordered mesopores of the magnesium oxide matrix.

In some embodiments, the magnesium oxide matrix is prepared from precipitation of magnesium hydroxide from a solution of a magnesium salt and ammonium hydroxide, followed by calcination of the magnesium hydroxide at 350 to 450° C.

In some embodiments, the magnesium oxide matrix has an average pore volume of 0.3 to 0.5 cm3/g and an average pore size of 3 to 6 nm.

In some embodiments, the magnesium oxide matrix consists essentially of magnesium oxide.

In some embodiments, the polyamine is the ethyleneamine.

In some embodiments, the ethyleneamine is at least one selected from the group consisting of diethylenetriamine, triethylentetramine, tetraethylenepentamine, pentaethylene hexamine, and hexaethylene heptamine.

In some embodiments, the ethyleneamine is diethylenetriamine.

In some embodiments, the polyamine is the polyethylene imine, and the polyethylene imine is a linear polyethylene imine.

In some embodiments, the aminated magnesium oxide adsorbent has a magnesium content of 15 to 31 wt. %, an oxygen content of 40 to 50 wt. %, a carbon content of 17.5 to 30 wt. %, and a nitrogen content of 2 to 16 wt. %, each based on a total weight of the aminated magnesium oxide adsorbent.

In some embodiments, the aminated magnesium oxide adsorbent has a BET surface area of 40 to 98 m2/g.

In some embodiments, the aminated magnesium oxide adsorbent has an average pore size of 7 to 11 nm.

In some embodiments, the aminated magnesium oxide adsorbent has an average pore volume of 0.05 to 0.3 cm3/g.

In some embodiments, the aminated magnesium oxide adsorbent is crystalline by XRD.

In some embodiments, the aminated magnesium oxide adsorbent has a CO2uptake capacity of 24 to 60 mg CO2per 1 g of the aminated magnesium oxide adsorbent at 30° C. and 1 atm.

It is another object of the present disclosure to provide a method of making the aminated magnesium oxide adsorbent, the method involving (i) precipitating magnesium hydroxide from a solution of a magnesium salt and ammonium hydroxide, (ii) calcining the magnesium hydroxide at 350 to 450° C. for 6 to 24 hours to form the magnesium oxide matrix having disordered mesopores, and (iii) wet impregnating the magnesium oxide matrix with an alcoholic solution of the polyamine.

In some embodiments, a molar ratio of the ammonium hydroxide to the magnesium salt in the solution is 2:1 to 9:1, and the precipitating is performed by heating the solution to 50 to 70° C. for 3 to 10 hours, followed by stirring the solution at 20 to 30° C. for 12 to 48 hours.

In some embodiments, a weight ratio of the polyamine to the magnesium oxide matrix for the wet impregnating is 1:1 to 1:3.

It is yet another object of the present disclosure to provide a method of capturing CO2from a gas mixture containing CO2and at least one other gas selected from the group consisting of hydrogen, oxygen, nitrogen, methane, and carbon monoxide, the method involving contacting the gas mixture with the aminated magnesium oxide adsorbent to adsorb at least a portion of the CO2into the aminated magnesium oxide adsorbent, thereby forming a loaded aminated magnesium oxide adsorbent and a gas stream depleted in CO2compared to the gas mixture.

In some embodiments, the gas mixture is a pre-combustion gas mixture containing 15 to 50 vol. % of CO2, based on a total volume of the gas mixture.

In some embodiments, the gas mixture is a post-combustion gas mixture containing 5 to 15 vol. % of CO2, based on a total volume of the gas mixture.

