Catalytic CO2 desorption process and catalyst for said process

Abstract

The present invention relates to a CO2 desorption process for the entire CO2 absorption / desorption procedure. The present invention particularly relates to a process and system for a catalytic CO2 desorption step in the presence of at least one Zr-based catalyst. The present invention also relates to a Zr-based catalyst suitable for the CO2 desorption process and a method for preparing such a catalyst.

Description

[Technical field]

[0001] The present invention relates to a CO2 desorption process for the entire CO2 absorption / desorption procedure. The present invention particularly relates to a process and system for a catalytic CO2 desorption step in the presence of at least one Zr-based catalyst. The present invention also relates to a Zr-based catalyst suitable for the CO2 desorption process and a method for preparing such a catalyst. [Background technology]

[0002] The rapid rise in carbon dioxide (CO2) concentrations in the atmosphere is causing significant climate change. According to the latest report of the Intergovernmental Panel on Climate Change (IPCC), unless CO2 emissions are immediately, rapidly and massively reduced, limiting warming to near 1.5°C or even to 2°C will become unrealistic. However, the risks and costs of non-fossil energy alternatives, for example nuclear, biomass and solar energy, are not able to meet the current energy demand. Moreover, any rapid change to non-fossil energy sources, even if possible, would lead to a massive disruption of the existing energy supply infrastructure with substantial impacts on the world economy. According to the Energy Information Administration, fossil fuel energy is likely to remain the dominant energy source. Under this premise, carbon capture and storage (CCS) and carbon capture and utilization (CCU) are promising pathways to curb the rampant increase in CO2 emissions. However, in either pathway, CO2 capture is always the first step. To meet mid- to long-term CO2 reduction targets, it is necessary to develop cost-effective CO2 capture technologies.

[0003] For CO2 from power plants, one of the major CO2 emission sources, post-combustion capture (PCC) using amine solvent as CO2 absorbent is the most mature and widely used technology. Moreover, post-combustion capture is considered to be the most promising technology to provide an energy-efficient and timely solution to reduce CO2 emissions from fossil power plants. A typical amine-based CO2 capture and regeneration process involves a whole absorption-desorption cycle of CO2 using amine solvent as shown in Figure 1. A CO2-containing flue gas stream is introduced into a packed-bed absorbent column, where the CO2-containing flue gas stream flows countercurrently to contact with the lean amine, allowing efficient absorption. After absorption, the rich amine solvent is introduced into a stripper column for thermal regeneration after flowing through a rich-lean heat exchanger. In the stripper column, heated steam is supplied to strip off the captured CO2 and increase the temperature. This free (lean) amine solvent then returns to the absorbent column for a new absorption cycle.

[0004] Typical amine solvents for CO2 capture include primary amines such as monoethanolamine (MEA), secondary amines such as diethanolamine (DEA) and tertiary amines such as methyldiethanolamine (MDEA). The CO2 absorption mechanism in various amine solvents is shown below.

[0005] Primary / Secondary Amines:

[0006]

number

[0007] Tertiary amines:

[0008]

number

[0009] MEA is the most widely used amine solvent due to its properties of extraordinary CO2 absorption rate, large capacity, high mass transfer performance and low cost. CO2 absorption in MEA solvent follows a zwitterionic mechanism. One CO2 is absorbed to form one carbamic acid and one protonated MEA. As shown in Figure 2, the desorption pathway of CO2 from MEA involves two steps: (1) proton transfer from the protonated amine to water and the desorption of HO. + (1) proton transfer, which involves the transfer of a proton from the amine to the carbamic acid; (2) decomposition of the carbamic acid and the release of CO2. The proton transfer step at low temperatures is unfavorable, forcing the industry to operate under high desorption temperatures for acceptable solvent regeneration efficiency. However, high regeneration temperatures (100-140°C) consume more than 60% of the total energy cost of PCC and also cause degradation of the amine solvent and corrosion of the equipment.

[0010] Extensive research has been conducted to reduce the energy cost during the solvent regeneration step of primary amines. New amine solvents and biphasic amine solvents can significantly reduce the energy cost during desorption while maintaining a relatively high CO2 absorption rate. However, they are still economically inefficient due to the high cost of the solvent and complex reactors.

[0011] From the viewpoint of catalyst, the use of suitable catalyst can reduce the activation energy of CO2 desorption and improve the reaction rate, thereby reducing the stripping time and increasing the solvent regeneration efficiency. Furthermore, some catalysts can enable CO2 desorption at temperatures below 100°C, greatly reducing energy consumption and solvent loss.

[0012] WO2011120138 discloses a method for applying solid catalysts to CO2 absorption and desorption processes. It was reported that CO2 desorption from 5M MEA solvent could be detected at temperatures below 50°C by using an acid catalyst such as H-ZSM-5 in the stripper. The reason for desorption at low temperatures is believed to be the direct donation of protons from the Brønsted acid (B acid) sites of H-ZSM-5 to the carbonic acid. The catalytic performance between the B acid sites and Lewis acid (L acid) sites by H-ZSM-5 and γ-Al2O3 was also compared. The B acid catalyst such as H-ZSM-5 showed better performance for CO2 desorption in the CO2 rich phase (temperature gradient phase) than the Lewis acid catalyst such as γ-Al2O3, but showed poor performance in the CO2 lean phase (isothermal phase). HY, H-Beta, CeSO4 / ZrO2, CMK-3-SiO2, SO4 for CO2 desorption from amine solvents 2- There are many reports on the use of solid acid catalysts such as / ZrO2 / SBA-15, including the following:

[0013] US2016030880A1 discloses a series of metal oxides that increase CO2 desorption from 3M MEA. It also used acidic materials (metal oxides, zeolites, proton exchange resins) to assist in amine regeneration. The metal oxides contained metals from the third to fifth rows of the periodic table. V2O5, MoO3, WO3, Cr2O3, MgO, γ-Al2O3, VO X / Al2O3, MoO x / Al2O3, WO x / Al2O3, H-zeolite-Y, and proton exchange resin (Amberlyst 15(H)) were tested. Among the other materials, MoO3 showed the best catalytic performance, starting CO2 desorption at 40 °C and increasing the amount of CO2 desorption by 27%. However, almost 96% of MoO3 was dissolved during the reaction. The amount of dissolution was reduced to 68% after using γ-Al2O3 as an assistant. However, the amount of CO2 desorption was also reduced. It seems that the improvement of desorption is highly related to the dissolution of metal oxides. This increased the difficulty of catalyst separation after the solvent regeneration process, greatly limiting the application of these types of catalysts.

[0014] US20160250591A1 reports TiO(OH)2 as an efficient catalyst for CO2 desorption from amine solvents. TiO(OH)2 could dramatically improve the CO2 desorption rate of a CO2-saturated 20% MEA solution by 100% at a low temperature gradient step of 88 °C, which was much higher than previous catalysts investigated.

[0015] US2010 / 209323A1 discloses a DeNOx catalyst for the reduction of NOx compounds, and a porous catalyst support material is provided. The catalyst of the invention comprises an active metal catalyst component and a mixed TiO2 / ZrO2 porous support particle comprising a) a crystalline phase comprising titanium dioxide and / or a titanium / zirconium mixed oxide, b) an amorphous phase comprising zirconium, and c) a small amount of one or more metal oxides or semi-metal oxides deposited on the amorphous outer layer. The catalyst of the invention exhibits superior activity and ammonia selectivity.

[0016] According to the reported results, the use of solid catalysts has already shown some improvement in CO2 desorption from amine solvents at low temperatures, but the application requirements still cannot be met due to the constraints of poor catalyst performance or catalyst dissolution problems. Insoluble solid catalysts with good and stable catalytic performance are strongly needed to reduce the energy consumption of the amine regeneration process of PPC. Summary of the Invention [Problem to be solved by the invention]

[0017] Therefore, there is a need for improved catalysts and improved methods for CO2 desorption. [Means for solving the problem]

[0018] It has now been found that the above objectives can be achieved, either individually or in any combination, by employing certain well-defined processes and catalysts disclosed herein.

[0019] The applicants have developed a Zr-based catalyst, preferably comprising ZrO(OH)2, and a method for preparing said catalyst, which exhibits advantageous properties when applied in CO2 desorption processes. For example, the catalytic activity of the catalyst according to the present invention and its embodiments is far superior to any previously reported catalyst. The catalytic activity increases with increasing catalyst loading. The catalytic action is confirmed as the catalytic activity is maintained over several cycles. The present invention and its embodiments also allow for a smaller desorption column, resulting in lower CAPEX. The present invention and its embodiments also allow for a lower CO2 desorption temperature, resulting in lower energy requirements (OPEX). The present invention and its embodiments also reduce the cost of regeneration of the solvent in the absorption process.

[0020] More specifically, the applicants have found that a precisely designed insoluble solid Zr-based catalyst according to the present invention or an embodiment thereof increases the CO2 desorption rate at low temperature in the solvent regeneration process of amine-based CO2 post-combustion process. The catalyst material preferably comprises a specific O:Zr atomic ratio. The catalyst material preferably comprises ZrO(OH)2 and / or is synthesized with a preferred basic precipitant under a preferred pH.

[0021] The applicants have demonstrated that the Zr-based catalyst according to the present invention can enhance the CO2 desorption rate at low temperatures. It is demonstrated herein that the synthesis method can affect the ratio of acidic and basic hydroxyl groups and the surface charge characteristics, leading to further improvement of the catalytic performance.

[0022] The catalyst prepared according to the present invention or its embodiments can be used with MEA solvent and other amines in CO2 capture plants. The improvement of CO2 desorption rate by the catalyst allows the solvent regeneration process to be carried out at low temperature, which can greatly reduce the energy cost of PPC and prevent the deterioration and evaporation of the amine solution. The catalyst is stable in the amine solvent and is insolubilized in the amine solvent, so it is easy to separate and regenerate. In addition, the catalyst may be deposited on a structured support (inert packing) instead of a traditional packing, or may be molded into a solid structure instead of a traditional packing.

[0023] In a first aspect, the present invention provides a method for preparing a Zr-based catalyst for CO2 desorption, the catalyst preferably comprising ZrO(OH)2. The method comprises the following steps: - mixing a solution containing a basic precipitant with a solution containing a Zr source, thereby preparing a synthesis solution; - precipitating a Zr-based catalyst, preferably comprising ZrO(OH)2, from the synthesis solution, thereby obtaining a precipitated Zr-based catalyst; Preferably it comprises:

[0024] The method is preferably characterized in that the pH of the synthesis solution is at least 3 and at most 8, preferably at least 4 and at most 7, for example about 5.

[0025] In some preferred embodiments, the Zr-based catalyst comprises Zr, O and H. Preferably, the O:Zr atomic ratio is at least 2.1, preferably at least 2.2, such as at least 2.3, such as at least 2.4, such as at least 2.5, such as at least 2.6, such as at least 2.7, such as at least 2.8, such as at least 2.9. In some embodiments, the O:Zr atomic ratio is at least 3.0, such as at least 3.5, such as at least 4.0.

[0026] In some preferred embodiments, the Zr-based catalyst comprises ZrO(OH). Preferably, the precipitated Zr-based catalyst comprises at least 60% by weight, preferably at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, such as at least 95% by weight, such as at least 98% by weight, for example at least 99% by weight, of ZrO(OH)2 compared to the total weight of the precipitated Zr-based catalyst.

[0027] In some preferred embodiments, the basic precipitant is NaOH, NH4OH (NH3 * Preferably, the basic precipitant is NaOH.

[0028] In some preferred embodiments, the Zr source is ZrO(NO3)2. In some preferred embodiments, the method comprises the steps of: - Calcining the precipitated Zr-based catalyst at a calcination temperature Tc Further includes:

[0029] Preferably, the calcination temperature Tc is at most 400°C, preferably at most 350°C, preferably at most 300°C.

[0030] In a second aspect, the present invention provides a Zr-based catalyst for CO2 desorption prepared using a method according to the first aspect and embodiments thereof. Preferably, the O:Zr atomic ratio is at least 2.1. Preferably, the Zr-based catalyst comprises ZrO(OH)2.

[0031] (Preferred) embodiments of the first aspect are also (preferred) embodiments of the second aspect and vice versa.

[0032] In some preferred embodiments, the ratio of acidic OH to basic OH of the Zr-based catalyst is at least 0.1 and at most 1.3, preferably at least 0.2 and at most 1.2, preferably at least 0.5 and at most 1.2, preferably at least 0.8 and at most 1.1, preferably about 1.0.

[0033] In some preferred embodiments, the Zr based catalyst has a surface charge zeta potential of at least -25mV, preferably at least -15mV, preferably at least -5mV, such as at least 0mV, such as at least 5mV.

[0034] In some preferred embodiments, the Zr-based catalyst comprises other metals, preferably selected from the group comprising Hf, Ce or Zn. In some preferred embodiments, the purity of Zr compared to other metals in the Zr-based catalyst is at least 80%, preferably at least 85%, preferably at least 90%, preferably at least 95%.

[0035] In a third aspect, the present invention provides a process for CO2 desorption from an amine solvent, the process comprising the following steps: - providing a CO2-containing amine solution comprising CO2 absorbed in an amine solvent; - providing a Zr-based catalyst according to the second aspect and its embodiments to a CO2-containing amine solution; - heating an amine solution containing a Zr-based catalyst to a desorption temperature Td; - Desorption of CO2 from the amine solution containing the Zr-based catalyst during the residence time Preferably it comprises:

[0036] (Preferred) embodiments of the second aspect are also (preferred) embodiments of the third aspect and vice versa.

[0037] In some preferred embodiments, the Zr-based catalyst acts as a non-solubilizing heterogeneous catalyst.

[0038] In some preferred embodiments, the amine solvent comprises a primary amine, a secondary amine, or a tertiary amine. Preferably, the amine solvent comprises monoethanolamine (MEA) or 2-amino-2-methyl-1-propanol (AMP), preferably monoethanolamine (MEA).

[0039] In some preferred embodiments, the residence time is at least 4 hours, and up to 168 hours, preferably at least 8 hours, and up to 72 hours, preferably at least 16 hours, and up to 48 hours, preferably at least 20 hours, and up to 36 hours, for example about 24 hours.

[0040] In a fourth aspect, the present invention provides a CO2 absorption and desorption process. Preferably, the process comprises the following steps: - absorbing CO2 into an amine solvent, thereby obtaining a CO2-containing amine solution; - using the process according to the third aspect or an embodiment thereof to desorb CO2 from the CO2-containing amine solution, thereby regenerating the amine solvent; Includes.

[0041] (Preferred) embodiments of the third aspect are also (preferred) embodiments of the fourth aspect and vice versa.

[0042] In a fifth aspect, the present invention provides the use of a Zr-based catalyst, preferably a catalyst according to the second aspect or an embodiment thereof, in a process according to the third or fourth aspect or an embodiment thereof.

[0043] (Preferred) embodiments of the second, third or fourth aspect are also (preferred) embodiments of the fifth aspect, and vice versa. [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 illustrates a carbon capture process. [Diagram 2] FIG. 1 shows reaction pathways for CO2 elimination from primary and secondary amine solvents. [Diagram 3] FIG. 1 illustrates a lab-scale CO2 desorption apparatus. [Figure 4] Graphs illustrating (A) CO2 loading concentration versus reaction time in 5M CO2 saturated MEA with various catalysts and (B) kinetic studies in the isothermal stage. [Diagram 5]Graphs illustrating (A) CO2 loading concentration versus reaction time in 5M CO2 saturated MEA with various loadings of ZrO(OH)2, (B) kinetic studies during the isothermal stage, and (C) catalytic reaction rate constant (kCAT) versus catalyst loading. [Figure 6] 1 is a graph illustrating (A) a diagram of the solvent reuse experiment, (B) CO2 loading concentration versus reaction time, and (C) a kinetic study of kCAT during the isothermal stage in recycled MEA solvent without solid catalyst. [Figure 7] 1 is a graph illustrating CO2 desorption in 5M CO2 saturated MEA solution for 168 h reaction with and without ZrO(OH)2. [Figure 8] (A) Diagram of two catalyst regeneration methods: wash reuse and direct reuse. (B) Graph illustrating CO2 loading concentration versus reaction time in 5M CO2 saturated MEA with ZrO(OH)2 regenerated by various methods. [Figure 9] Graph illustrating (A) CO2 loading concentration versus reaction time in 5M CO2 saturated MEA with ZrO(OH)2 synthesized under various pH and (B) kCAT versus synthesis pH of ZrO(OH)2. [Figure 10] Graphs illustrating (A) CO2 loading concentration versus reaction time in 5M CO2 saturated MEA with ZrO(OH)2 synthesized by various methods and (B) kinetic studies during the isothermal stage. [Figure 11] 1 is a graph illustrating thermogravimetric analysis (TGA) results of a ZrO(OH)2 catalyst under a N2 atmosphere. [Figure 12] 1 is a graph illustrating the relationship between synthesis pH and density for basic OH, acidic OH, and total OH ZrO(OH). [Figure 13] 1 is a graph illustrating the relationship between kCAT and acidic OH / basic OH ratio. [Figure 14] 1 is a graph illustrating (A) CO2 loading concentration versus reaction time and (B) kinetic studies at the isothermal stage in 5M CO2 saturated MEA with ZrO(OH)2 calcined at various temperatures. [Figure 15]1 is a graph illustrating XRD results of commercial ZrO2 and ZrO(OH)2 calcined at various temperatures. [Figure 16] 1 is a graph illustrating (A) CO2 loading concentration versus reaction time in 5M CO2 saturated MEA with various MZrO(OH)2 catalysts and (B) kinetic studies during the isothermal stage. [Figure 17] 1 is a graph illustrating the relationship between kCAT and zeta potential for various ZrO(OH)2 based catalysts at pH 9.3. [Figure 18] 1 is a graph illustrating (A) CO2 loading concentration versus reaction time and (B) kinetic studies during the isothermal stage in 2.5 M CO2 saturated AMP with and without various catalysts. [Figure 19] FIG. 1 illustrates a continuous CO2 desorption reactor. [Figure 20] FIG. 20 is an enlarged cross-section of the diagram of the continuous CO2 desorption reactor illustrated in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] When describing the present invention, the terms used should be construed in accordance with the following definitions, unless the context dictates otherwise.

[0046] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. By way of further guidance, definitions of terms are included to better understand the teachings of the present invention.

[0047] In the following paragraphs, the various aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects, unless expressly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. Reference throughout this specification to "one embodiment" or "embodiment" means that the particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearance of the phrase "one embodiment" or "embodiment" in various places throughout this specification does not necessarily refer to all the same embodiment, although that may be the case. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure. Moreover, some embodiments described herein include some features included in other embodiments, but not other features, and as would be understood by one of ordinary skill in the art, combinations of features of the various embodiments are meant to be within the scope of the invention and form various embodiments.

[0048] As used herein, the terms "comprising," "comprises," and "comprised of" are synonymous with "including," "includes," or "containing," and are inclusive or open-ended and do not exclude additional, unrecited members, elements, or method steps. As used herein, the terms "comprising," "comprises," and "comprised of" include "consisting of," "consists," and "consists of."

[0049] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. By way of example, "a step" means one step or more than one step.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0051] The recitation of numerical ranges by endpoints includes all integers subsumed within the range, and, where appropriate, fractions (e.g., 1 to 5 may include 1, 2, 3, 4, e.g., when referring to the number of elements, and 1.5, 2, 2.75, and 3.80, e.g., when referring to a measurement). The recitation of endpoints also includes the endpoint values ​​themselves (e.g., 1.0 to 5.0 includes both 1.0 and 5.0). Every numerical range recited herein is intended to include all subranges subsumed within that range.

[0052] As used herein, the term "about," when referring to a measurable value, such as a parameter, amount, time duration, etc., is meant to encompass the specified value and a variation of no more than + / - 10%, preferably no more than + / - 5%, and more preferably no more than + / - 1% from the specified value, provided such variations are appropriate to practice the disclosed invention. It should be understood that the value to which the "about" modifier refers is itself specifically and preferably disclosed.

[0053] The terms "wt. %, "vol. %" or "mole %" refer to the weight percentage, volume percentage or mole percentage of a component relative to the total weight, volume or moles of a material including the component, respectively.

[0054] When describing the present invention, the terms used should be construed in accordance with the following definitions, unless the context dictates otherwise.

[0055] Preferred features, embodiments and uses of the present invention are presented herein below. Each embodiment of the present invention as defined may be combined with any other embodiment, unless expressly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. The present invention is specifically incorporated herein by any one of the following embodiments, or any combination of one or more of the following embodiments with any other aspect and / or embodiment.

[0056] In a first aspect, the present invention provides a method for preparing a Zr-based catalyst for CO2 desorption, the catalyst preferably comprising ZrO(OH)2. The method comprises the following steps: - mixing a solution containing a basic precipitant with a solution containing a Zr source, thereby preparing a synthesis solution; - precipitating a Zr-based catalyst, preferably comprising ZrO(OH)2, from the synthesis solution, thereby obtaining a precipitated Zr-based catalyst; Preferably it comprises:

[0057] The method is preferably characterized in that the pH of the synthesis solution is at least 3 and at most 8, preferably at least 4 and at most 7, such as about 5. In some embodiments, the pH of the synthesis solution is at least 3, preferably at least 4, such as at least 5. In some embodiments, the pH of the synthesis solution is at most 8, preferably at most 7, such as at most 6.

[0058] Catalysts prepared in this manner have been found to provide significant improvements in CO2 desorption properties without significant dissolution, as illustrated in the Examples section. More specifically, it is demonstrated herein that the synthesis method affects the ratio of acidic to basic hydroxyl groups and the surface charge properties, leading to further improvements in catalytic performance.

[0059] In some preferred embodiments, the Zr-based catalyst comprises Zr, O and H. Preferably, the O:Zr atomic ratio is at least 2.1, preferably at least 2.2, such as at least 2.3, such as at least 2.4, such as at least 2.5, such as at least 2.6, such as at least 2.7, such as at least 2.8, such as at least 2.9, such as about 3.0. In some embodiments, the O:Zr atomic ratio is at least 3.0, such as at least 3.5, such as at least 4.0. In some embodiments, the O:Zr atomic ratio is at most 5.0, such as at most 4.9, such as at most 4.8, such as at most 4.7, such as at most 4.6, such as at most 4.5, such as at most 4.4, such as at most 4.3, such as at most 4.2, such as at most 4.1, such as about 4.0. In some embodiments the O:Zr atomic ratio is at least 2.1, at most 5.0, such as at least 2.2, at most 4.9, such as at least 2.3, at most 4.8, such as at least 2.4, at most 4.7, such as at least 2.5, at most 4.6, such as at least 2.6, at most 4.5, such as at least 2.7, at most 4.4, such as at least 2.8, at most 4.3, such as at least 2.9, at most 4.2, such as at least 2.9, at most 4.1, such as about 3.5.

[0060] Catalysts with this atomic ratio were found to provide significant improvement in CO2 desorption properties. The O:Zr atomic ratio is defined herein as the volume fraction and can be measured by the weight loss of the catalyst at 170°C-800°C, assuming that the weight loss comes from the loss of hydroxyl groups forming HO and the remaining part of the solid is ZrO2. The weight loss can be measured by thermogravimetric analysis (TGA) tested under N2 flow and temperature rate of 5-20°C / min, preferably 10°C / min, assuming that all weight loss from a temperature of 180°C onwards forms water and the final solid species above 600-800°C is considered as ZrO2.

[0061] In some preferred embodiments, the Zr-based catalyst comprises ZrO(OH). Preferably, the precipitated Zr-based catalyst comprises at least 60% by weight, preferably at least 70% by weight, preferably at least 80% by weight, preferably at least 90% by weight, such as at least 95% by weight, such as at least 98% by weight, for example at least 99% by weight, of ZrO(OH)2 compared to the total weight of the precipitated Zr-based catalyst.

[0062] Catalysts having this atomic structure have been found to provide significant improvements in CO2 desorption properties, as illustrated in the Examples section.

[0063] In some embodiments, the solution containing the precipitating agent comprises at least 1.00 M, up to 1.50 M, for example about 1.25 M, of the precipitating agent.

[0064] In some preferred embodiments, the basic precipitant is NaOH, NH4OH (NH3 * Preferably, the basic precipitant is NaOH.

[0065] In some embodiments, the solution comprising a Zr source comprises at least 2.00M, up to 4.00M, for example about 3.00M, of the Zr source.

[0066] In some preferred embodiments, the Zr source is ZrO(NO3)2, which is a common Zr source and can more easily form ZrO(OH)2 compared to Zr(NO3)4.

[0067] In some embodiments, the synthesis solution is prepared by adding a solution containing a precipitant dropwise to a solution containing a Zr source while stirring. This allows the final pH to be more easily controlled. Furthermore, the addition of a solution containing a Zr source to a solution containing a precipitant can irreversibly form a precipitate closer to ZrO2 in a basic environment.

[0068] In some embodiments, a co-precipitation method is used. In some preferred embodiments, the method comprises the steps of: - Calcining the precipitated Zr-based catalyst at a calcination temperature Tc Further includes:

[0069] Preferably, the calcination temperature Tc is at most 400°C, preferably at most 350°C, preferably at most 300°C.

[0070] It was found that a calcination step at too high a temperature would remove the OH groups and reduce the catalyst to ZrO2, thereby significantly reducing the catalytic activity, as illustrated in the Examples section.

[0071] In a second aspect, the present invention provides a Zr-based catalyst for CO2 desorption prepared using a method according to the first aspect and embodiments thereof. Preferably, the O:Zr atomic ratio is at least 2.1 or other values ​​as described herein. Preferably, the Zr-based catalyst comprises ZrO(OH)2, preferably in percentages as described herein.

[0072] (Preferred) embodiments of the first aspect are also (preferred) embodiments of the second aspect and vice versa.

[0073] Such catalysts have been found to provide significant improvement in CO2 desorption properties without significant dissolution, as illustrated in the Examples section.

[0074] In some preferred embodiments, the ratio of acidic OH to basic OH of the Zr-based catalyst is at least 0.1 and at most 1.3, preferably at least 0.2 and at most 1.2, preferably at least 0.5 and at most 1.2, preferably at least 0.8 and at most 1.1, preferably about 1.0.

[0075] Controlling the ratio of acidic to basic OH has been found to result in significant improvements in CO2 desorption properties, as illustrated in the Examples section.

[0076] The ratio of acidic to basic OH is preferably measured by thermogravimetric analysis (TGA), for example performed on a TGA Q500 from TA Instruments. TGA may be performed under a N2 atmosphere of 10 mL / min with a temperature ramp from 50° C. to 150° C. and then to 800° C. in 30 minutes to ensure that all free water has been released. The temperature ramp rate may be 10° C. / min.

[0077] In some preferred embodiments, the Zr-based catalysts remain in an amorphous phase upon ambient / inert heating / calcination to 200-300°C. The inventors have surprisingly found that the best performing catalysts do not exhibit tetragonal t-ZrO2 phase and remain in an amorphous phase upon ambient / inert heating / calcination to 200-300°C, while the inferior catalysts clearly form t-ZrO2 phase upon the same heat treatment (measured using traditional state of the art powder X-ray diffraction, e.g., as illustrated in the Examples section). In some preferred embodiments, the Zr-based catalysts contain up to 20.0 wt%, preferably up to 10.0 wt%, preferably up to 5.0 wt%, preferably up to 2.0 wt%, preferably up to 1.0 wt%, and essentially no tetragonal crystalline t-ZrO2 phase after ambient / inert heating / calcination to 200-300°C.

[0078] In some preferred embodiments, the Zr based catalyst has a surface charge zeta potential of at least -25mV, preferably at least -15mV, preferably at least -5mV, such as at least 0mV, such as at least 5mV.

[0079] Catalysts with such high surface charge have been found to provide improved CO2 desorption properties, as illustrated in the Examples section.

[0080] Zeta potential is preferably measured with a NanoPlus HD with an autotitrator manufactured by Particulate Systems. Typically, 40 mg of well-ground sample powder can be mixed with 40 g of ultrapure water, followed by ultrasonication for 20 minutes. Finely dispersed sample solutions can be used for testing. Zeta potential can be tested under a pH of 9.3±0.2. 0.1 M HCl and 0.1 M NaOH can be used for pH adjustment.

[0081] In some preferred embodiments, the Zr-based catalyst comprises other metals, preferably selected from the group comprising Hf, Ce or Zn. Other metals than Zr may be used for cost and / or stability reasons. In some preferred embodiments, the purity of Zr compared to other metals in the Zr-based catalyst is at least 80%, preferably at least 85%, preferably at least 90%, preferably at least 95%.

[0082] Such catalysts have also been found to provide suitable catalytic activity. In a third aspect, the present invention provides a process for CO2 desorption from an amine solvent, the process comprising the following steps: - providing a CO2-containing amine solution comprising CO2 absorbed in an amine solvent; - providing a Zr-based catalyst according to the second aspect and its embodiments to a CO2-containing amine solution; - heating an amine solution containing a Zr-based catalyst to a desorption temperature Td; - Desorption of CO2 from the amine solution containing the Zr-based catalyst during the residence time Preferably it comprises:

[0083] (Preferred) embodiments of the second aspect are also (preferred) embodiments of the third aspect and vice versa.

[0084] The present invention reduces the regeneration costs of the solvent in the absorption / desorption process. In some preferred embodiments, the Zr-based catalyst acts as a non-solubilized heterogeneous catalyst, which is typically stable in amine solvents and is easily isolated and regenerated because it is insoluble in the amine solvent.

[0085] In some preferred embodiments, the amine solvent comprises primary amine, secondary amine or tertiary amine. Examples of suitable amines include, but are not limited to, monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), diethanolamine (DEA), diglycolamine (DGA), methyldiethanolamine (MDEA), piperazine (PZ), ammonia, amines, alkanolamines, derivatives and / or combinations thereof.Preferably, the amine solvent comprises monoethanolamine (MEA) or 2-amino-2-methyl-1-propanol (AMP), preferably monoethanolamine (MEA).

[0086] In some embodiments, the amine solvent comprises a combination of two or more amines as co-solvents, such as AMP and PZ. The amine combination can increase absorption rate and circulation capacity, reduce regeneration energy (heat load), apply high amine solution concentrations, and minimize degradation.

[0087] The AMP / PZ (3M / 1.5M) ratio is considered to be the preferred ratio. The appropriate ratio of AMP / PZ can increase the absorption rate and circulation capacity while avoiding the precipitation of PZ.

[0088] In some embodiments, the amine solvent is present in the amine solution at a molar concentration of at least 1M and up to 10M, preferably at least 2M and up to 8M, preferably at least 4M and up to 6M, for example at a concentration of about 5M.

[0089] These concentrations have been found to provide optimal results, as illustrated in the Examples section.

[0090] In some embodiments, the Zr-based catalyst is provided at a concentration of at least 1.0 g and up to 8.0 g, preferably at least 2.0 g and up to 6.0 g, preferably at least 2.5 g and up to 4.0 g, for example about 3.0 g of Zr-based catalyst per 100 mL of amine solution.

[0091] These amounts have been found to provide optimal results, as illustrated in the Examples section. In some embodiments the desorption temperature Td is at most 500K, preferably at most 450K, preferably at most 400K, preferably at most 380K, preferably about 361K.

[0092] The present invention has the distinct advantage that the desorption temperature can be kept low. The improvement of the CO2 desorption rate by the catalyst allows the solvent regeneration process to be carried out at a low temperature, which greatly reduces the energy cost of PPC and prevents the deterioration and evaporation of the amine solution.

[0093] In some preferred embodiments, the residence time is at least 4 hours, and up to 168 hours, preferably at least 8 hours, and up to 72 hours, preferably at least 16 hours, and up to 48 hours, preferably at least 20 hours, and up to 36 hours, for example about 24 hours.

[0094] These residence times have been found to provide optimal results, as illustrated in the Examples section.

[0095] In a fourth aspect, the present invention provides a CO2 absorption and desorption process. Preferably, the process comprises the following steps: - absorbing CO2 into an amine solvent, thereby obtaining a CO2-containing amine solution; - using the process according to the third aspect or an embodiment thereof to desorb CO2 from the CO2-containing amine solution, thereby regenerating the amine solvent; Includes.

[0096] (Preferred) embodiments of the third aspect are also (preferred) embodiments of the fourth aspect and vice versa.

[0097] The present invention allows for reduced regeneration costs of the solvent in the absorption / desorption process. In some embodiments, the process is a batch process. In some more preferred embodiments, the process is a continuous process.

[0098] In some embodiments, the process includes the following steps: - Reusing the Zr-based catalyst in the process Further includes:

[0099] The catalyst of the present invention has the advantage that it can be easily reused, especially since it typically operates as a heterogeneous catalyst in that the catalyst does not solubilize.

[0100] In some embodiments, recycling the Zr-based catalyst comprises the steps of: - Directly reusing the Zr-based catalyst and the amine solvent in the process by using them in the resorption step without separation. Includes.

[0101] In some embodiments, recycling the Zr-based catalyst comprises the steps of: - removing the Zr-based catalyst from the amine solvent, preferably by filtration; - washing the Zr-based catalyst with water; - optionally centrifuging the Zr-based catalyst; - drying the Zr-based catalyst; Adding the dried catalyst to the amine solvent Includes.

[0102] In a fifth aspect, the present invention provides the use of a Zr-based catalyst, preferably a catalyst according to the second aspect or an embodiment thereof, in a process according to the third or fourth aspect or an embodiment thereof.

[0103] (Preferred) embodiments of the second, third or fourth aspect are also (preferred) embodiments of the fifth aspect, and vice versa.

[0104] The use of the Zr-based catalysts described herein also allows for the miniaturization of the desorption column, resulting in lower CAPEX. The use of the Zr-based catalysts described herein also allows for a reduction in the CO2 desorption temperature, which in turn leads to lower energy requirements (OPEX) and / or less solvent degradation. For example, desorption at lower temperatures allows for less amine degradation.

[0105] Working Example The following examples are used to merely illustrate the present invention and should not be construed as limiting its scope in any way. Although the present invention is shown in only a small part of its form, those skilled in the art should understand that the present invention is not so limited and is susceptible to various changes and modifications without departing from the scope of the present invention.

[0106] Experimental Method The experimental setup for solvent regeneration (CO2 desorption) is shown in Figure 3. The setup consists of a 250 mL round-bottom flask equipped with a thermometer, a heater controlled by a temperature controller, a condenser, and a magnetic stirrer. For a typical CO2 desorption experiment run, 150 mL of 5 M MEA solution initially loaded with CO2 (0.52 mol / mol) and 3 g of catalyst are mixed in the reactor under a N2 flow of 500 mL / min from the top of the condenser. The solution is then heated to 361.1 K in 50 ± 5 min and kept constant for 180 min with a stirring speed of 500 rpm. The time when the solution reaches 361.1 K is noted as 0 min. For a long-term (168 h) CO2 desorption experiment, 6 g of ZrO(OH)2 is used in 150 mL of 5 M MEA. The CO2 concentration of the solution is analyzed by a Chittick apparatus with a mean absolute deviation of less than 5%. Typically, 500 μL of CO2-loaded amine solution was added to the flask by pipette, and then 1 mL of 1.5 M H2SO4 was injected into the solution with vigorous stirring. The volume of CO2 released is noted to further calculate the CO2 concentration of the sample. All samples were tested in triplicate, and the average value was taken.

[0107] The catalyst was characterized in two aspects: the amount of CO2 deposition during the temperature gradient phase and the catalytic reaction rate constant (k CAT ) was used for evaluation.

[0108] k CAT was calculated as follows: k CAT =k overall -k blank k overall is the overall reaction rate constant calculated from the CO2 concentration after 0, 30, 60, 90, 120 and 180 minutes when the temperature stabilizes (isothermal phase). k blank is calculated from the change in CO2 concentration in the MEA solvent without any catalyst during the first 3 h of desorption in the isothermal phase. Unless otherwise specified, k blank The value is -1.3 * 10 -4 minutes -1 It is considered that.

[0109] X-ray powder diffraction (XRD) was performed on a high-throughput STOE STADI P Combi diffractometer in transmission mode using a focused Ge(111) monochromatic X-ray incident beam (λ = 1.5406 Å, Cu Kα source).

[0110] Thermogravimetric analysis (TGA) was performed on a TGA Q500 from TA Instruments. Typically, TGA was performed under a N2 atmosphere at 10 mL / min with a temperature gradient from 50° C. to 150° C. and then to 800° C. in 30 min to ensure that all free water was released. The temperature gradient rate was 10° C. / min.

[0111] Zeta potential was tested on a NanoPlus HD with an autotitrator from Particulate Systems. Typically, 40 mg of well-ground sample powder was mixed with 40 g of ultrapure water, followed by sonication for 20 min. The finely dispersed sample solution was used for testing. Zeta potential was tested under a pH of 9.3 ± 0.2. 0.1 M HCl and 0.1 M NaOH were used for pH adjustment.

[0112] The O:Zr ratios of Zr-based catalyst samples prepared according to the present invention and synthesized at various pH values ​​were found to be 4.27, 4.50, 4.85, 3.39, 2.85 and 2.49.

[0113] Example 1: CO2 desorption performance with various catalysts The performance of various catalysts is shown in Figure 4 and Table 1. The O:Zr ratios of these catalysts ranged from 3:1 to 5:1. Compared to the blank, all three, H-ZSM-5, TiO(OH)2 and ZrO(OH)2, show improved CO2 desorption amount in the temperature gradient stage, with ZrO(OH)2 showing 150% improvement in CO2 desorption amount compared to H-ZSM-5 and TiO(OH)2. After the temperature stabilizes, no significant improvement in CO2 desorption by H-ZSM-5 is observed, while TiO(OH)2 and ZrO(OH)2 still show significant improvement in CO2 desorption rate. Kinetic studies in the isothermal stage show that the k of H-ZSM-5 is significantly improved, whereas TiO(OH)2 and ZrO(OH)2 still show significant improvement in CO2 desorption rate. CAT The value is almost 0, and ZrO(OH)2 is -3.1 * 10 -4 minutes-1 The highest k CAT value, which was found to be 2.4 times that of TiO(OH)2. MoO3 shows a very high increase in the amount of CO2 desorption during the temperature gradient stage, but a lower CO2 desorption rate than ZrO(OH)2 during the isothermal stage. The k CAT is only -1.8 * 10 -4 minutes -1 This means that the catalytic effect of MoO3 is only about 58% of that of ZrO(OH)2. It should be noted that MoO3 is completely dissolved after the temperature reaches 88°C, but no significant dissolution is observed for ZrO(OH)2. k of blank MEA solvent overall is -1.3 * 10 -4 minutes -1 Taking into account this, the use of ZrO(OH)2 provides a 238% improvement in the reaction rate constant for CO2 desorption from the MEA at 88 °C.

[0114] [Table 1]

[0115] Reaction conditions: 3 g catalyst, 150 mL CO2 saturated 5M MEA, 0.5 L / min N2 flow from the top of the condenser, 88° C. The amount of CO2 desorption is calculated at the end of the temperature ramp step.

[0116] Example 2: CO2 desorption performance for various catalyst amounts The CO2 desorption performance with various amounts of ZrO(OH)2 is shown in Figure 5 and Table 2. The amount of CO2 desorption in the temperature gradient stage increased with the amount of catalyst. CAT and catalyst amount show a linear relationship when the catalyst amount is less than 4 g. However, when the catalyst amount is increased to 6 g, k CAT no longer increases linearly but becomes relatively low due to mass transport limitations.

[0117] [Table 2]

[0118] Reaction conditions: 150 mL of CO2 saturated 5M MEA, 0.5 L / min N2 flow from the top of the condenser, 88° C. The amount of CO2 desorption is calculated at the end of the temperature ramp step.

[0119] To confirm that the active sites of ZrO(OH)2 originate from the solid phase and not from solubilized species, the solid phase ZrO(OH)2 was removed from the MEA solution by centrifugation after a typical CO2 desorption reaction, the remaining MEA solution was collected, CO2 was reabsorbed, and another desorption test was performed without any catalyst, noted as "solvent reuse". The experimental scheme and results are shown in Figure 6. The desorption performance showed no significant difference from the blank, and removal of the catalyst abolished the catalytic effect. The desorption rate constant was reduced by more than 90% from that of ZrO(OH)2.

[0120] In the long-term desorption experiment (Fig. 7), ZrO(OH)2 improved the CO2 desorption amount by almost 70% in 24 h compared to the blank. Then, due to thermodynamic constraints, the CO2 desorption rate by ZrO(OH)2 was suppressed, and the CO2 concentration in the solution approached that of the blank and finally reached a similar level after 168 h. This also indicates that the CO2 desorption by ZrO(OH)2 is a catalytic reaction rather than a stoichiometric reaction.

[0121] Catalyst regeneration tests were also conducted with two methods: water-washed regeneration and direct reuse. The schemes of the two methods are shown in Figure 8A. For washing reuse, the used ZrO(OH)2 was washed with water, centrifuged, and dried at 100 °C overnight, and then used in a new CO2 desorption test. For direct reuse, the reaction mixture (lean MEA solution and ZrO(OH)2) was directly subjected to the resorption followed by desorption process. As shown in Figure 8B, both the direct reused ZrO(OH)2 and the water-washed reused ZrO(OH)2 show similar CO2 desorption performance as the unused ZrO(OH)2. The results indicate that ZrO(OH)2 is not a one-time catalyst and can be easily reused.

[0122] Example 3: Effect of synthesis pH on catalyst synthesis A typical ZrO(OH)2 is synthesized by precipitation method. NaOH solution was added dropwise to ZrO(NO3)2 solution under vigorous stirring until pH reached 5. After aging for 3 h, the precipitate was centrifuged, washed three times, and then dried at 100 °C for 48 h. The outstanding catalytic performance of ZrO(OH)2 for CO2 desorption from amine solvents is due to the carefully controlled synthesis process and precisely designed surface properties.

[0123] By changing the amount of basic precipitant, the synthesis pH of ZrO(OH)2 can be easily controlled. As shown in Figure 9 and Table 3, ZrO(OH)2 synthesized under different pH showed very different catalytic performances.

[0124] [Table 3]

[0125] Reaction conditions: 3 g catalyst, 150 mL CO2 saturated 5M MEA, 0.5 L / min N2 flow from the top of the condenser, 88° C. The amount of CO2 desorption is calculated at the end of the temperature ramp step.

[0126] k CAT The relationship between pH and the composite pH shows a volcanic curve, k CAT The maximum is 3.1 at synthetic pH 5. * 10 -4 minutes -1 As the synthesis pH increases or decreases, k CAT It should be noted that ZrO(OH)2 synthesized at low pH such as pH 3 exhibits high CO2 desorption amount and very low catalytic effect (k CAT =-0.7 * 10 -4 minutes -1 ), which indicated that the improvement could be due to residual acid in the synthesis process.

[0127] Example 4: Effect of synthesis method on catalyst synthesis This example compares the catalytic performance of ZrO(OH)2 synthesized by a method according to an embodiment of the present invention with ZrO(OH)2 synthesized from a reported synthesis method for metal hydroxyl oxides.

[0128] Following the reported synthesis method of high performance TiO(OH)2, ZrO(OH)2(iso) catalyst was synthesized. Zirconium isopropoxide was added to deionized water with a molar ratio of H2O:Zr of 1400:1, followed by stirring for 4 h. The precipitated powder was filtered, rinsed with deionized water and ethanol three times, and then dried at 100 °C for about 10 h.

[0129] ZrO(OH)2 can also be synthesized by hydrothermal method. ZrO(NO3)2 was mixed in water-ethanol solvent, held at 80 °C, and circulated for 2 h. The precipitated powder was then filtered, rinsed three times with deionized water, and dried at 100 °C for about 10 h. The dried powder is annotated as ZrO(OH)2(hydro).

[0130] [Table 4]

[0131] Reaction conditions: 3 g catalyst, 150 mL CO2 saturated 5M MEA, 0.5 L / min N2 flow from the top of the condenser, 88° C. The amount of CO2 desorption is calculated at the end of the temperature ramp step.

[0132] The catalytic performance of ZrO(OH)2 synthesized by various methods for CO2 desorption is shown in Table 4 and Figure 10. ZrO(OH)2(hydro) shows the highest CO2 desorption amount in the temperature gradient stage, but only 0.9 * 10 -4 minutes -1 k CAT ZrO(OH)2(iso) shows similar improvement in CO2 desorption amount as ZrO(OH)2. k of ZrO(OH)2(iso) in the temperature gradient stage CAT The value is -1.6 * 10 -4 minutes -1This is only 51% of that of ZrO(OH)2, but the k CAT Still higher than the value (1.3 * 10 -4 minutes -1 The results further demonstrate the advantages of the current synthesis method and show that ZrO(OH)2 itself is more suitable for CO2 desorption than TiO(OH)2.

[0133] Example 5: Effect of Hydroxyl Groups The hydroxyl groups of ZrO(OH)2 are considered to be either acidic or basic depending on the type of bond. The mono-bonded OH can be considered as a weak base. It has a low bond energy with Zr and can be removed at low temperatures (below 400°C). As for the bridging bonded OH groups, their bond with Zr is strong and they can be considered as weak B acids. The removal temperature of the bridging bonded OH is relatively high (400-600°C).

[0134] The amount of hydroxyl groups can be quantified by TGA, since the hydroxyl groups are released as H2O with increasing temperature. A typical TGA result of ZrO(OH)2 is shown in Figure 11. The water released at 200°C-400°C is considered to be due to weakly bonded OH (basic OH), and the water released at 400°C-600°C is considered to be derived from strongly bonded OH (acidic OH).

[0135] The density of hydroxyl groups of ZrO(OH)2 synthesized under various pH values ​​is shown in Figure 12. It can be seen that the synthesis pH has a significant effect on OH groups. When the synthesis pH was increased from 3 to 5, the total density of hydroxyl groups decreased very slightly from 25.7 mmol / g to 23.3 mmol / g, with a slight increase in basic OH (from 10.8 to 11.6 mmol / g) and a decrease in acidic OH (from 14.9 to 12.1 mmol / g). When the synthesis pH was further increased from 5 to 7, the density of both total OH and acidic OH decreased significantly, while basic OH remained almost unchanged. A further increase in pH to 12 resulted in a decrease in the density of both types of OH.

[0136] k CATThe volcano curve relationship between k and the basic / acidic OH ratio is shown in Figure 13. As the ratio of basic OH to acidic OH approaches 1.0, k CAT The results show that there is a synergistic effect between acidic OH and basic OH, therefore controlling the ratio of basic OH and acidic OH in the catalyst may be one of the crucial factors for high performance ZrO(OH)2.

[0137] To further prove the importance of hydroxyl groups in the catalyst, ZrO(OH)2 is calcined from 200 to 600 °C to partially remove OH groups from ZrO(OH)2. From Figure 14 and Table 5, it can be seen that the amount of CO2 desorption in the temperature gradient step decreased with increasing calcination temperature. However, only ZrO(OH)2 calcined at 200 and 300 °C shows a slight decrease in catalytic performance. By further increasing the calcination temperature to 400 °C, the k CAT is -1.3 * 10 -4 minutes -1 The XRD results (Figure 15) show that below 400 °C calcination, ZrO(OH)2 remains amorphous, and after calcination at 400 °C, ZrO(OH)2 crystallizes to form t-ZrO2 with a crystal size of 30 nm. However, compared to commercial ZrO2, ZrO(OH)2 (400 °C) has twice the k CAT The better performance of ZrO(OH)2 compared to ZrO2 may be due to the high density of hydroxyl groups, which makes ZrO(OH)2 a better catalyst than ZrO2. On the other hand, by calcining ZrO(OH)2 at a temperature of 300 °C, a more stable catalyst can be obtained with only a slight decrease in catalytic performance. The O:Zr ratio of ZrO(OH)2 (400 °C) was 2.17:1, which was higher than 3:1 for the other catalysts.

[0138] [Table 5]

[0139] Reaction conditions: 3 g catalyst, 150 mL CO2 saturated 5M MEA, 0.5 L / min N2 flow from the top of the condenser, 88° C. The amount of CO2 desorption is calculated at the end of the temperature ramp step.

[0140] Example 6: Catalytic performance of mixed metal hydroxyl oxides Mixed metal hydroxyl oxides were investigated based on ZrO(OH)2. Typically 10% metal nitrates were mixed with a zirconium precursor followed by ZrO(OH)2 using the same synthesis method. The catalysts are noted as 10%ZrO(OH)2 (M=Hf, Ce, Zn).

[0141] As shown in FIG. 16 and Table 6, 10% ZnZrO(OH)2 showed a 25% improvement in CO2 desorption compared to the blank and a 10% improvement over ZrO(OH)2. However, the k CAT is only -1.6 * 10 -4 minutes -1 , which is 10%HfZrO(OH)2(-1.9 * 10 -4 minutes -1 ) and 10% CeZrO(OH)2(-2.3 * 10 -4 minutes -1 ) lower than ZrO(OH)2 at -3.1 * 10 -4 minutes -1 The highest k CAT It should be noted that the lowest k of 10%MZrO(OH)2 is 10%ZnZrO(OH)2. CAT However, the k of TiO(OH)2 CAT This still represents a 25% improvement over

[0142] [Table 6]

[0143] Reaction conditions: 3 g catalyst, 150 mL CO2 saturated 5M MEA, 0.5 L / min N2 flow from the top of the condenser, 88° C. The amount of CO2 desorption is calculated at the end of the temperature ramp step.

[0144] Example 7: Surface charge of ZrO(OH)2-based catalysts The surface charge of ZrO(OH)2-based catalysts was tested by a zeta potential analyzer under pH 9.3, which is a typical pH of CO2-MEA solvent during desorption. The value of zeta potential reflects the charge characteristics of the particle surface. A positive zeta potential indicates that the particle surface is positively charged, and the absolute value of the zeta potential reflects the charge density. Figure 17 shows the k CAT The results show a clear relationship between the zeta potential and the catalytic activity. The higher the zeta potential, the higher the catalytic activity achieved. A higher zeta potential leads to a higher concentration of carbamic acid species adsorbed on the catalyst surface, which is favorable for the decomposition step of carbamic acid and shows a higher catalytic activity.

[0145] Example 7: CO2 desorption performance of ZrO(OH)2 in 2.5M CO2 saturated AMP solution 2-Amino-2-methyl-1-propanol (AMP) has been proposed as a commercially attractive new CO2 absorbent due to its advantages in absorption capacity, absorption rate, degradation resistance, and renewable energy.

[0146] [Table 7]

[0147] Reaction conditions: 3 g catalyst, 150 mL CO2 saturated 2.5 M AMP, 0.5 L / min N2 flow from the top of the condenser, 88° C. The amount of CO2 desorption is calculated at the end of the temperature ramp step.

[0148] To demonstrate the CO2 desorption performance of ZrO(OH)2 catalyst in other amine solvents, CO2 desorption experiments were carried out in CO2 saturated 2.5M AMP solution. The CO2 desorption performance is shown in Figure 18 and Table 7. AMP already showed a very high desorption rate without any catalyst. The k of AMP blank is -4.8 * 10 -4 minutes -1 This is the k blankHowever, ZrO(OH)2 still shows improvement in both the temperature gradient and isothermal steps. Furthermore, TiO(OH)2 (-1.3 * 10 -4 minutes -1 ) compared to the k CAT showed an improvement of 250%. The results demonstrated that ZrO(OH)2 not only works well in MEA solvent, but can also be applied to other amine solvents to improve the CO2 desorption rate at low temperatures.

[0149] Example 8: Industrial Desorption Process To simulate the continuous desorption process in industry, the catalyst is also tested in a homemade continuous reactor (see Figure 19 and Figure 20 for an enlarged cross section). The CO2-rich amine solution was heated at 85 °C for 3.4 mL min. -1 The CO2 released from the amine solution was carried to the analysis system by a N2 flow blown from above the liquid surface. The flow rate of CO2 desorption was calculated by the signal intensity of m / z=44 from mass spectrometry (MS). The results were double-confirmed by titrating the lean amine solution with CO2.

[0150] The calculation method is as follows: CO2 desorption rate calculated by MS:

[0151]

number

[0152] I: CO2 signal intensity from MS A: Calibration factor of MS signal (%) CO2(%):CO2 concentration(%) F N2 :N2 flow rate (mL / min) F CO2 : released CO2 flow rate (mL / min) The CO2 desorption rate is also confirmed by titration of the liquid sample after the reaction, which is calculated as follows: F CO2 =(ct-c0)×FMEA ct: CO2 concentration in the reaction solution (mL CO2 / mL CO2 ) c0: CO2 concentration in unused solution (mL CO2 / mL CO2 ) F MEA : MEA solution flow rate Table 8 shows the results of CO2 desorption rates in the continuous reactors with various catalysts. Tests without catalyst (referred to as blank), containing glass beads of comparable size to those of the catalyst, showed a relatively low CO2 desorption rate of 9.7 mL / min. By using TiO(OH)2, the CO2 desorption rate increased to 21.0 mL / min. The CO2 desorption rate with ZrO(OH)2 was 35.50 mL / min, showing an improvement of 266% compared to the CO2 desorption rate of the blank and 69% compared to TiO(OH)2.

[0153] [Table 8]

[0154] Reaction conditions: N2: 100 mL / min, CO2 saturated MEA solution flow: 3.4 mL / min, 85 °C, 3 cm catalyst.

[0155] Figures 19 and 20 use the following reference numbers: 101 - liquid sampling; 111 - rich amine tank; 112 - lean amine tank; 121 - pump; 122 - Coriolis circulating heat exchanger; 123 - heated transfer line; 124 - drain valve; 125 - heated laboratory bath; 126 - cold finger trap; 127 - process cooling water; 128 - variable vacuum pump; 129 - flow rate indicator; 130 - catalyst; 140 - mass spectrometry.

Claims

1. CO ２ A method for preparing a Zr-based catalyst for desorption comprising the following steps: - mixing a solution containing a basic precipitant with a solution containing a Zr source, thereby preparing a synthesis solution; - precipitating said Zr-based catalyst from said synthesis solution, thereby obtaining a precipitated Zr-based catalyst. A method comprising: wherein the pH of said synthesis solution is at least 3 and at most 8, preferably at least 4 and at most 7, e.g. about 5; said Zr-based catalyst comprises Zr, O and H, and said O:Zr atomic ratio is at least 2.

1.

2. The Zr-based catalyst is ZrO(OH). ２ The method of claim 1 , comprising:

3. The precipitated Zr-based catalyst is at least 90 wt. % ZrO(OH) relative to the total weight of the precipitated Zr-based catalyst. ２ The method of claim 1 or 2, comprising:

4. The basic precipitant is a hydroxide and / or the Zr source is ZrO(NO ３ ) ２ The method according to any one of claims 1 to 3, wherein

5. Steps below: - calcining said precipitated Zr-based catalyst at a calcination temperature Tc; Further comprising: A process according to any one of claims 1 to 4, wherein the calcination temperature Tc is at most 400°C, preferably at most 350°C, preferably at most 300°C.

6. CO prepared by the method according to any one of claims 1 to 5. ２ A Zr-based catalyst for desorption, having an O:Zr atomic ratio of at least 2.1, preferably said Zr-based catalyst is ZrO(OH) ２ A Zr-based catalyst comprising:

7. 7. The Zr-based catalyst according to claim 6, wherein the ratio of acidic OH to basic OH is at least 0.1 and at most 1.

3.

8. 8. Zr-based catalyst according to claim 6 or 7, having a surface charge zeta potential of at least -25 mV, preferably at least -5 mV.

9. 9. The Zr based catalyst according to any one of claims 6 to 8, comprising other metals selected from the group comprising Hf, Ce or Zn, preferably the purity of Zr compared to said other metals in said Zr based catalyst is at least 90%.

10. CO from amine solvents ２ A desorption process comprising the steps of: - CO absorbed in amine solvent ２ CO ２ Providing an amine solution containing The Zr-based catalyst according to any one of claims 6 to 9 is ２ providing a containing amine solution; - heating the amine solution containing the Zr-based catalyst to a desorption temperature Td; - CO from the amine solution containing the Zr-based catalyst during the residence time ２ To detach and The process includes:

11. The process of claim 10, wherein the Zr-based catalyst acts as a non-solubilizing heterogeneous catalyst.

12. 12. The process according to claim 10 or 11, wherein the amine solvent comprises monoethanolamine (MEA) or 2-amino-2-methyl-1-propanol (AMP), preferably monoethanolamine (MEA).

13. The process according to any one of claims 10 to 12, wherein the residence time is at least 4 hours and at most 168 hours, preferably at least 20 hours and at most 36 hours.

14. CO ２ An absorption and desorption process comprising the following steps: -CO ２ is absorbed in an amine solvent, thereby ２ obtaining a containing amine solution; - CO using the process according to any one of claims 10 to 13 ２ The CO ２ and desorbing the amine from the containing amine solution, thereby regenerating the amine solvent. The process includes:

15. Use of a Zr-based catalyst, preferably a catalyst according to any one of claims 6 to 9, in a process according to any one of claims 10 to 14.

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