Method for preparing hydrotalcite compound from cationic oligomer and application of hydrotalcite compound in flue gas desulfurization

Abstract

The invention discloses a method for preparing a hydrotalcite compound from a cationic oligomer and application of the hydrotalcite compound in flue gas desulfurization. The hydrotalcite compound comprises an active component, a precipitator and a surfactant, the active component is one or more of magnesium salt, aluminum salt, ferric salt, zinc salt, copper salt, cerium salt and lanthanum salt; the precipitant is urea; the surfactant is a quaternary ammonium salt cationic oligomer, the molecular formula of the surfactant is [(CH3) 4N + R1N + (CH3) 3R1] n, R1 is a C10-C18 alkyl chain, and n is 1-2. According to the present invention, the characteristics of the hydrotalcite compound precursor are utilized, the catalytic active component is embedded between the precursor laminates through the exchange reaction so as to obtain the hydrotalcite compound crystal with high activity metal dispersity, and the quaternary ammonium salt cation oligomer is adopted to modify the surface of the hydrotalcite compound crystal so as to obtain the high-activity metal-dispersity hydrotalcite compound crystal; and the dispersity of active metal in the crystallization process can be further improved, so that the synergistic effect among multiple metals is fully exerted, and the desulfurization activity is effectively enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical environmental protection, and in particular, to a method for preparing hydrotalcite-like compounds from cationic oligomers and their application in flue gas desulfurization. Background Art

[0002] SO2 is a colorless and highly pungent acidic gas, and its large-scale emission will cause serious harm to humans and the ecological environment. As a common air pollutant, SO2 mainly comes from the flue gas generated by the combustion of fossil energy. In order to reduce SO2 emissions, a variety of flue gas treatment technologies have been proposed, which can be classified into wet, dry, and semi-dry flue gas desulfurization according to process characteristics. Among them, the wet flue gas desulfurization technology is mature and widely used, but its system is complex, the equipment is huge, the investment and operation costs are high, and there is secondary pollution. Compared with the wet flue gas desulfurization technology, the dry desulfurization has the advantages of small floor area, simple equipment operation, and low cost, and has received extensive attention since it was proposed. Dry flue gas desulfurization refers to the catalytic conversion of SO x in the flue gas into metal sulfates or sulfites under the action of a desulfurizer and fixing them, thereby effectively reducing the concentration of sulfur oxides in the discharged flue gas. Desulfurizers can generally be divided into two types: renewable and non-renewable. Among them, a renewable desulfurizer refers to the catalytic conversion of sulfur in metal sulfates or sulfites into SO2, H2S, or elemental S under the action of a reducing gas, so that the reaction activity of the desulfurizer can be partially restored to a certain extent. The selectable renewable desulfurizers mainly include composite metal oxides derived from metal oxides, spinels, and hydrotalcite-like compounds. Metal-based catalysts include transition metals, noble metals, and non-noble metals, which have good structural tunability, abundant Lewis acid active sites, and high activity stability, thus showing excellent catalytic reduction reaction activity. However, such adsorbents are difficult to reduce and have a low sulfur capacity; the preparation process of spinel desulfurizers is simple, the desulfurization effect is good, and the process is mature. They are the main type of desulfurization adsorbents for commercial applications at present. However, the Mg content in such desulfurizers is low, and the bulk sulfates are difficult to regenerate and reduce, resulting in unstable activity; the Mg content in the composite metal oxide desulfurizer is relatively high, and it has become a research hotspot due to its high sulfur capacity, large specific surface area, and good cycle stability. Its desulfurization activity is closely related to the structural properties of the uncalcined hydrotalcite-like compound (LDHs) crystals, especially the dispersion degree of the active metal.

[0003] Patent CN 115253623 A discloses a preparation method of a composite metal oxide type high-temperature flue gas desulfurizer. The active metal is loaded on the surface of the desulfurizer by an impregnation method, and the desulfurizer is treated at 650 °C for 1500 - 5000 mg / m 3When treating flue gas with a SO2 concentration, it shows good regeneration performance, and the desulfurization efficiency is above 95%. However, the dispersion of the active components of the desulfurizer is poor, and the desulfurization reaction temperature is relatively high.

[0004] Patent CN 101905117 A discloses a preparation method of an active component of a sulfur transfer agent for catalytic cracking flue gas. By using the roasting reduction method, a magnesium-aluminum hydrotalcite loaded with Ce or a multi-component hydrotalcite precursor containing other elements is obtained, and then a sulfur transfer agent for catalytic cracking flue gas is prepared by high-temperature roasting. The sulfur transfer agent prepared by this method has a relatively low reduction temperature and a relatively high sulfur absorption capacity during oxidation. However, the dispersion of the metal promoter is poor, and the reduction reaction temperature is relatively high.

[0005] Patent CN 113713800 A discloses a preparation method of a high-temperature flue gas desulfurizer. By using coprecipitation and hydrothermal reaction of a divalent metal ion salt and a water-soluble aluminum salt, a layered double metal hydroxide precursor is obtained, and then the catalytic active components are embedded into the precursor through an ion exchange reaction. Compared with the mechanical mixing method, the two-step reaction can significantly increase the specific surface area of the desulfurizer, and the ion exchange reaction can also improve the dispersion degree of the active metal compared with the impregnation method. However, the process flow is complex, and the desulfurization and regeneration reaction temperatures must reach 700 °C to show good desulfurization and regeneration performance.

[0006] In view of this, the present application is specifically proposed. Summary of the Invention

[0007] In order to solve the above problems, the purpose of the present invention is to provide a method for preparing hydrotalcite-like compounds using cationic oligomers and their application in flue gas desulfurization. By utilizing the characteristics of the hydrotalcite-like compound precursor, the catalytic active components are embedded between the precursor lamellar structures through an ion exchange reaction, thereby obtaining hydrotalcite-like compound crystals with a high dispersion degree of active metals. At the same time, the surface of the hydrotalcite-like compound crystals is modified with quaternary ammonium salt cationic oligomers, which can further improve the dispersion degree of active metals during the crystallization process, thereby giving full play to the synergistic effect between multiple metals and effectively enhancing its desulfurization activity.

[0008] The present invention is achieved through the following technical solutions:

[0009] A hydrotalcite-like compound prepared using cationic oligomers, comprising active components, a precipitant, and a surfactant;

[0010] The active components are one or more of magnesium salts, aluminum salts, iron salts, zinc salts, copper salts, cerium salts, and lanthanum salts;

[0011] The precipitant is urea;

[0012] The surfactant is a quaternary ammonium salt cationic oligomer, and its molecular formula is as follows [(CH3)4N + R1N +((CH3)3R1)n, where R1 is C 10 -C 18 alkyl chain, and n = 1 - 2.

[0013] The present invention provides a method for preparing hydrotalcite - like compounds using cationic oligomers, which includes the following steps:

[0014] (1) Mix the active - component metal precursor salts and the precipitant at room temperature to prepare the corresponding aqueous solution A;

[0015] (2) Dissolve the surfactant in water and prepare the corresponding mixture B;

[0016] (3) Stir the mixture A and B at room temperature for 0.5 h. After mixing evenly, transfer them to a high - pressure reactor, and obtain hydrotalcite - like compound crystals after hydrothermal reaction for a certain time;

[0017] (4) After centrifugal washing, drying, grinding into powder, and calcining the hydrotalcite - like compound crystals obtained by crystallization, obtain composite metal oxide powder;

[0018] (5) Add a certain amount of binder and pore - expanding agent to the composite metal oxide powder obtained after calcination, extrude it into a shape, and obtain the corresponding desulfurizer after calcination.

[0019] The present invention utilizes the characteristics of hydrotalcite - like compound precursors, and embeds catalytic active components into the precursor interlayer through an exchange reaction, thereby obtaining hydrotalcite - like compound crystals with a high active metal dispersion degree. In addition, using quaternary ammonium salt cationic oligomers to modify the surface of hydrotalcite - like compound crystals can further improve the dispersion degree of active metals during the crystallization process, thereby giving full play to the synergistic effect between multiple metals and effectively enhancing its desulfurization activity.

[0020] In a certain embodiment, in step (1), the metal precursor salts include magnesium salts, aluminum salts, cerium salts, and iron salts, where the molar ratio of Mg 2+ : Al 3+ : Ce 3+ : Fe 3+ is 2:0.5 - 1:0 - 0.5:0 - 0.5, and the total concentration of the metal salt solution is 1 mol / L.

[0021] In a certain embodiment, in step (1), the concentration of the precipitant urea is 2 - 10 mol / L.

[0022] In a certain embodiment, in step (2), the concentration of the surfactant is 0.05 - 0.5 mol / L.

[0023] In one embodiment, in step (3), the temperature of the hydrothermal reaction is 120 - 180 °C, and the reaction time is 4 - 10 h.

[0024] In one embodiment, in step (4), the centrifugal washing is performed by washing with deionized water until neutral, the drying temperature is 60 - 90 °C, the calcination temperature is 500 - 520 °C, and the calcination time is 5 - 12 h.

[0025] In one embodiment, in step (5), the binder is aluminosilicate sol, and the mass ratio of it to the composite metal oxide powder is 1:1 - 1:3; the pore expander is sassafras powder, and the addition amount is 1 - 5 wt% of the total amount of substances.

[0026] The present invention also provides the application of a hydrotalcite-like compound or a composite metal oxide desulfurizer prepared by a method for preparing a hydrotalcite-like compound using a cationic oligomer in flue gas desulfurization.

[0027] The reducing and regenerating gas is one of 10% H2 / N2, 10% H2S / N2, 10% CH4 / N2, 10% CO / N2, and preferably 10% H2 / N2.

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

[0029] 1. A method for preparing a hydrotalcite-like compound using a cationic oligomer provided by an embodiment of the present invention utilizes the characteristics of a hydrotalcite-like compound precursor and embeds catalytically active components between the precursor lamellae through an exchange reaction, enabling the acquisition of a hydrotalcite-like compound crystal with a high active metal dispersion degree;

[0030] 2. A method for preparing a hydrotalcite-like compound using a cationic oligomer provided by an embodiment of the present invention modifies the surface of the hydrotalcite-like compound crystal with a quaternary ammonium salt cationic oligomer and obtains a hydrotalcite-like compound crystal with a high active metal dispersion degree through a one-step hydrothermal method, which can further improve the dispersion degree of active metals during the crystallization process, thereby fully exerting the synergistic effect between multiple metals and showing high desulfurization performance during the flue gas desulfurization reaction process;

[0031] 3. A method for preparing a hydrotalcite-like compound using a cationic oligomer provided by an embodiment of the present invention does not require the addition of any organic solvents during the crystallization process of the hydrotalcite-like compound, and the process is simple, green, and environmentally friendly. Specific Embodiments

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and do not limit the present invention.

[0033] In the following description, a number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those of ordinary skill in the art that: the present invention need not be practiced with these specific details. In other embodiments, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring the present invention.

[0034] Throughout the specification, references to "one embodiment", "an embodiment", "an example", or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, the phrases "one embodiment", "an embodiment", "an example", or "an example" that appear throughout the specification do not necessarily all refer to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] In the description of the present invention, the orientation or positional relationship indicated by the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the scope of protection of the present invention.

[0036] Embodiment 1

[0037] A method for preparing a composite metal oxide desulfurizer provided by an embodiment of the present invention specifically includes the following steps:

[0038] (1) Preparation of hydrotalcite-like compounds

[0039] Prepare 500 ml of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, iron nitrate, and urea, denoted as mixed solution A; wherein the concentration of magnesium nitrate is 0.65 mol / L, the concentration of aluminum nitrate is 0.29 mol / L, the concentration of cerium nitrate is 0.04 mol / L, the concentration of iron nitrate is 0.02 mol / L, and the concentration of urea is 5 mol / L.

[0040] Prepare 250 ml of a mixed solution of a quaternary ammonium salt cationic oligomer surfactant, denoted as mixed solution B, wherein the structural formula of the quaternary ammonium salt cationic oligomer surfactant is [(CH3)4N + R1N + (CH3)3R1]n, where R1 is an alkyl chain of C 16 and n = 2, and the concentration is 0.05 mol / L.

[0041] After mixing and stirring the mixed solutions A and B at room temperature for 0.5 h, transfer them into a 1000 ml polytetrafluoroethylene high-pressure reactor and react at 120 °C for 6 h. Then, perform centrifugal separation, wash with deionized water until neutral, and finally wash once with ethanol; the obtained solid is dried overnight in an oven at 90 °C and then ground into powder (greater than 300 mesh).

[0042] (2) Preparation of the composite metal oxide desulfurizer

[0043] Transfer the hydrotalcite-like compound powder prepared in step (1) into a muffle furnace and calcine at 500 °C for 6 h in an air atmosphere to obtain the corresponding composite metal oxide powder, where the heating rate is 2 °C / min.

[0044] Weigh 70 g of the composite metal oxide powder, add 40 g of aluminum gel, 2.7 g of sesbania powder, and 60 g of deionized water, mix well, extrude into shape, and then place at room temperature for 48 h, dry at 100 °C for 12 h, and calcine at 500 °C for 4 h to obtain the corresponding desulfurizer S1.

[0045] Example 2

[0046] A preparation method of a composite metal oxide desulfurizer provided by an embodiment of the present invention specifically includes the following steps:

[0047] (1) Preparation of the hydrotalcite-like compound

[0048] Prepare a 500 ml mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, iron nitrate, and urea, denoted as mixed solution A; where the concentration of magnesium nitrate is 0.65 mol / L, the concentration of aluminum nitrate is 0.29 mol / L, the concentration of cerium nitrate is 0.04 mol / L, the concentration of iron nitrate is 0.02 mol / L, and the concentration of urea is 5 mol / L.

[0049] Prepare a 250 ml mixed solution of quaternary ammonium salt cationic oligomer surfactants, denoted as mixed solution B, where the structural formula of the quaternary ammonium salt cationic oligomer surfactant is [(CH3)4N + R1N + (CH3)3R1]n, where R1 is an alkyl chain of C 16 and n = 2, and the concentration is 0.1 mol / L.

[0050] After mixing and stirring the mixed solutions A and B at room temperature for 0.5 h, transfer them into a 1000 ml polytetrafluoroethylene high-pressure reactor and react at 120 °C for 6 h; then, perform centrifugal separation, wash with deionized water until neutral, and finally wash once with ethanol; the obtained solid is dried overnight in an oven at 90 °C and then ground into powder (greater than 300 mesh).

[0051] (2) Preparation of Composite Metal Oxide Desulfurizer

[0052] Transfer the hydrotalcite-like compound powder prepared in step (1) to a muffle furnace and calcine it at 500 °C for 6 h in an air atmosphere to obtain the corresponding composite metal oxide powder, where the heating rate is 2 °C / min.

[0053] Weigh 70 g of the composite metal oxide powder, add 40 g of aluminum glue, 2.7 g of sesbania powder and 60 g of deionized water. After mixing evenly, extrude it into a shape, and then place it at room temperature for 48 h, dry it at 100 °C for 12 h, and calcine it at 500 °C for 4 h to obtain the corresponding desulfurizer S2.

[0054] Example 3

[0055] A preparation method of a composite metal oxide desulfurizer provided by an embodiment of the present invention specifically includes the following steps:

[0056] (1) Preparation of Hydrotalcite-like Compound

[0057] Prepare a 500 ml mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, iron nitrate and urea, denoted as mixed solution A; where the concentration of magnesium nitrate is 0.65 mol / L, the concentration of aluminum nitrate is 0.29 mol / L, the concentration of cerium nitrate is 0.04 mol / L, the concentration of iron nitrate is 0.02 mol / L, and the concentration of urea is 5 mol / L.

[0058] Prepare a 250 ml mixed solution of quaternary ammonium salt cationic oligomer surfactant, denoted as mixed solution B, where the structural formula of the quaternary ammonium salt cationic oligomer surfactant is [(CH3)4N + R1N + (CH3)3R1]n, where R1 is an alkyl chain of C 16 , and n = 2, with a concentration of 0.2 mol / L.

[0059] Mix and stir mixed solutions A and B at room temperature for 0.5 h, then transfer them to a 1000 ml polytetrafluoroethylene high-pressure reaction kettle and react at 120 °C for 6 h; then, perform centrifugal separation, wash with deionized water until neutral, and finally wash once with ethanol; dry the obtained solid in an oven at 90 °C overnight, and then grind it into powder (greater than 300 mesh).

[0060] (2) Preparation of Composite Metal Oxide Desulfurizer

[0061] Transfer the hydrotalcite-like compound powder prepared in step (1) to a muffle furnace and calcine it at 500 °C for 6 h in an air atmosphere to obtain the corresponding composite metal oxide powder, where the heating rate is 2 °C / min.

[0062] Weigh 70 g of the composite metal oxide powder, add 40 g of aluminum glue, 2.7 g of sesbania powder and 60 g of deionized water. After mixing evenly, extrude it into a shape. Then, place it at room temperature for 48 h, dry it at 100 °C for 12 h, and calcine it at 500 °C for 4 h to obtain the corresponding desulfurizer S3.

[0063] Example 4

[0064] A preparation method of a composite metal oxide desulfurizer provided by an embodiment of the present invention specifically includes the following steps:

[0065] (1) Preparation of hydrotalcite-like compounds

[0066] Prepare a 500 ml mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, iron nitrate and urea, denoted as mixed solution A; among them, the concentration of magnesium nitrate is 0.65 mol / L, the concentration of aluminum nitrate is 0.29 mol / L, the concentration of cerium nitrate is 0.04 mol / L, the concentration of iron nitrate is 0.02 mol / L, and the concentration of urea is 5 mol / L.

[0067] Prepare a 250 ml mixed solution of quaternary ammonium salt cationic oligomer surfactants, denoted as mixed solution B, where the structural formula of the quaternary ammonium salt cationic oligomer surfactant is [(CH3)4N + R1N + (CH3)3R1]n, where R1 is an alkyl chain of C 16 , and n = 1, with a concentration of 0.2 mol / L.

[0068] Mix and stir mixed solutions A and B at room temperature for 0.5 h, then transfer them to a 1000 ml polytetrafluoroethylene high-pressure reaction kettle and react at 120 °C for 6 h; then, perform centrifugal separation, wash with deionized water until neutral, and finally wash once with ethanol; the obtained solid is dried overnight in an oven at 90 °C and then ground into powder (greater than 300 mesh).

[0069] (2) Preparation of composite metal oxide desulfurizer

[0070] Transfer the hydrotalcite-like compound powder prepared in step (1) to a muffle furnace and calcine it at 500 °C for 6 h in an air atmosphere to obtain the corresponding composite metal oxide powder, where the heating rate is 2 °C / min.

[0071] Weigh 70 g of the composite metal oxide powder, add 40 g of aluminum glue, 2.7 g of sesbania powder and 60 g of deionized water. After mixing evenly, extrude it into a shape. Then, place it at room temperature for 48 h, dry it at 100 °C for 12 h, and calcine it at 500 °C for 4 h to obtain the corresponding desulfurizer S4.

[0072] Comparative Example 1

[0073] A preparation method of a composite metal oxide desulfurizer provided in this comparative example specifically includes the following steps:

[0074] (1) Preparation of hydrotalcite-like compounds

[0075] Prepare 500 ml of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, iron nitrate and urea, denoted as mixed solution A. Among them, the concentration of magnesium nitrate is 0.65 mol / L, the concentration of aluminum nitrate is 0.29 mol / L, the concentration of cerium nitrate is 0.04 mol / L, the concentration of iron nitrate is 0.02 mol / L, and the concentration of urea is 5 mol / L.

[0076] Transfer mixed solution A and 250 ml of deionized water to a 1000 ml polytetrafluoroethylene high-pressure reactor, and react at 120 °C for 6 h. Then, perform centrifugal separation, wash with deionized water until neutral, and finally wash once with ethanol. The obtained solid is dried overnight in an oven at 90 °C and then ground into powder (greater than 300 mesh).

[0077] (2) Preparation of composite metal oxide desulfurizer

[0078] Transfer the hydrotalcite-like compound powder prepared in step (1) to a muffle furnace and calcine it at 500 °C for 6 h in an air atmosphere to obtain the corresponding composite metal oxide powder, where the heating rate is 2 °C / min.

[0079] Weigh 70 g of the composite metal oxide powder, add 40 g of aluminum gel, 2.7 g of talc powder and 60 g of deionized water, mix well and extrude into a shape. Then, place it at room temperature for 48 h, dry at 100 °C for 12 h, and calcine at 500 °C for 4 h to obtain the corresponding desulfurizer D1.

[0080] The present invention will be further described below in combination with examples of activity evaluation.

[0081] Examples of activity evaluation:

[0082] The composition of the inlet raw material gas in this test is shown in Table 1, and the space velocity of the desulfurization reaction is 500 h -1 , and the desulfurization activity evaluation is carried out under the condition that the reaction temperature is 500 °C.

[0083] Table 1 Composition of raw material gas

[0084] Gas composition <![CDATA[SO2]]> <![CDATA[O2]]> <![CDATA[CO2]]> <![CDATA[N2]]> Volume percentage (%) 0.5 4 20 75.5

[0085] At the beginning of the evaluation test, first weigh 3 g of small particles with a particle size of 20 - 40 mesh and load them into a fixed-bed micro-reactor, and fix them with quartz wool on the upper and lower layers respectively.

[0086] During the reaction process, when the SO2 content in the outlet gas is higher than 300 ppm, switch to the reducing gas flow. After the regeneration is completed, enter the next desulfurization reaction cycle, and calculate the sulfur capacity of the desulfurizer at this time. The results are shown in Table 2 below.

[0087] Table 2 Desulfurization effect of the composite metal oxide desulfurizer prepared by the present invention

[0088] Desulfurizer Sample number <![CDATA[Sulfur capacity (g SO2 / g cat.)]]> Example 1 Desulfurizer R1 0.18 Example 2 Desulfurizer R2 0.20 Example 3 Desulfurizer R3 0.17 Example 4 Desulfurizer R4 0.18 Comparative example 1 Desulfurizer D1 0.17

[0089] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A hydrotalcite-like compound prepared from a cationic oligomer, characterized in that, It includes an active component, a precipitant and a surfactant; The active component is one or more of magnesium salt, aluminum salt, iron salt, zinc salt, copper salt, cerium salt and lanthanum salt; The precipitant is urea; The surfactant is a quaternary ammonium cationic oligomer, and its molecular formula is as follows [(CH3)4N + R1N + (CH3)3R1]n, where R1 is an alkyl chain of C 10 -C 18 , and n = 1 - 2.

2. A method for preparing the hydrotalcite-like compound according to claim 1 by using a cationic oligomer, characterized in that, It includes the following steps: (1) Mix the active component metal precursor salt and the precipitant at room temperature to prepare a corresponding aqueous solution A; (2) Dissolve the surfactant in water and prepare a corresponding mixture B; (3) Stir the mixture A and B at room temperature for 0.5 h. After mixing evenly, transfer them to a high-pressure reactor. After hydrothermal reaction for a certain time, hydrotalcite-like compound crystals are obtained; (4) The hydrotalcite-like compound crystals obtained by crystallization are centrifuged, washed, dried, ground into powder and calcined to obtain a composite metal oxide powder.

3. A method for preparing hydrotalcite-like compounds using cationic oligomers according to claim 2, characterized in that, In step (1), the metal precursor salts include magnesium salts, aluminum salts, cerium salts and iron salts, wherein the molar ratio of Mg 2+ : Al 3+ : Ce 3+ : Fe 3+ is 2:0.5-1:0-0.5:0-0.5, and the total concentration of the metal salt solution is 1 mol / L.

4. A method for preparing a hydrotalcite-like compound using a cationic oligomer according to claim 2, characterized in that, In step (1), the concentration of the precipitant urea is 2-10 mol / L.

5. A method for preparing hydrotalcite-like compounds using cationic oligomers according to claim 2, characterized in that, In step (2), the concentration of the surfactant is 0.05-0.5 mol / L.

6. A method for preparing a hydrotalcite-like compound using a cationic oligomer according to claim 2, characterized in that, In step (3), the temperature of the hydrothermal reaction is 120-180 °C and the reaction time is 4-10 h.

7. A method for preparing a hydrotalcite-like compound using a cationic oligomer according to claim 2, characterized in that, In step (4), the centrifugal washing is to wash with deionized water until neutral, the drying temperature is 60-90 °C, the calcination temperature is 500-520 °C, and the calcination time is 5-12 h.

8. A method for preparing hydrotalcite-like compounds using cationic oligomers according to claim 2, characterized in that, It further includes: step (5), adding a certain amount of binder and pore former to the composite metal oxide powder obtained after calcination in step (4), extruding into shape, and calcining to obtain a composite metal oxide desulfurizer.

9. A method for preparing a hydrotalcite-like compound using a cationic oligomer according to claim 8, characterized in that, In step (5), the binder is aluminum gel, and its mass ratio to the composite metal oxide powder is 1:1-1:3; the pore former is sesbania powder, and the addition amount is 1-5 wt% of the total amount of substances.

10. Application of the hydrotalcite-like compound described in claim 1 or the composite metal oxide desulfurizer prepared by the method for preparing a hydrotalcite-like compound using a cationic oligomer described in any one of claims 2-9 in flue gas desulfurization.