Ca / M multi-metal bifunctional material as well as preparation method and application thereof

Abstract

The invention discloses a Ca / M multi-metal bifunctional material and a preparation method and application thereof, and belongs to the field of carbon dioxide treatment.The method comprises the steps that a Ca source, an M source and a complexing agent are pre-reacted and then desolventized, and a precursor is obtained; calcining the precursor at the temperature of 500 DEG C or above to obtain a precursor material; and carrying out thermal modification on the precursor material in a hydrogen-containing atmosphere to prepare the calcium-based multi-metal bifunctional material, the M source is one or more materials containing alkali metal, alkaline earth metal and transition metal, and the Ca / M element content ratio of the Ca source to the M source is 1: (1-5). The invention also comprises the material prepared by the preparation method and application of the material in carbon dioxide capture and conversion. The material prepared by the preparation method disclosed by the invention has excellent carbon dioxide reduction catalytic activity and cycling stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial process waste gas purification, relates to carbon dioxide catalytic degradation technology, and specifically relates to a Ca / M multi-metal bifunctional material, a preparation method thereof, and an application thereof. Background Art

[0002] Regarding the problem of carbon dioxide emissions, the traditional liquid ammonia adsorption method has high energy consumption and environmental risks. In contrast, solid adsorbents provide a more stable and efficient solution for reversible CO2 capture and conversion. Carbon Capture, Utilization and Storage (CCUS) technology captures CO2 and converts it into high-value chemicals, realizing large-scale low-carbon utilization of coal resources. However, the high cost of CCUS and the complexity of transportation and enrichment processes hinder its economic feasibility.

[0003] Developing bifunctional materials for Integrated Carbon Capture and Utilization (ICCU) can eliminate the need for CO2 transportation and storage, thereby reducing the overall cost. The main paths of ICCU include reverse water gas shift (RWGS), methanation, dry reforming, etc. Compared with other processes, the ICCU-RWGS process has higher CO2 conversion rate, negligible side reactions, and higher space-time yield, and can efficiently capture low-concentration CO2 in flue gas, store green hydrogen and utilize sensible heat, showing significant application potential. Bifunctional materials mainly composed of calcium-based materials have advantages due to their high theoretical CO2 adsorption capacity, economy, and wide availability. However, these materials face significant challenges in high-temperature cycle deactivation. Optimizing the types and ratios of catalysts and adsorbents, and developing economical, efficient, and stable bifunctional materials for use at appropriate temperatures are the future development trends. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem of unsatisfactory existing carbon dioxide capture and reduction effects, and provide a Ca / M multi-metal bifunctional material (which can also be called a carbon dioxide capture and reduction catalyst), a preparation method thereof, and an application thereof. This material takes into account both carbon dioxide capture and reduction activities, and improves the capture, reduction activities, and cycle stability of carbon dioxide.

[0005] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0006] A preparation method of a Ca / M multi-metal bifunctional material, and the method is as follows:

[0007] Step 1: Pre-react a Ca source, an M source, and a complexing agent and then desolvate to obtain a precursor;

[0008] Step 2: Calcinate the precursor at a temperature of 500 - 850 °C to obtain a precursor material;

[0009] Step 3: Thermally modify the precursor material in a hydrogen-containing atmosphere to prepare a Ca / M multi-metal bifunctional material.

[0010] In the present invention, the Ca source and the M source are calcined at a temperature of 500 - 850 °C, and then thermally modified in a hydrogen-containing atmosphere. In this way, the physicochemical structure characteristics of the prepared material can be unexpectedly improved, so as to adapt to the requirements of carbon dioxide capture and reduction catalysis, and improve the carbon dioxide capture and reduction catalytic effects.

[0011] In the present invention, the precursor is innovatively calcined, combined with the subsequent thermal modification treatment in a hydrogen-containing atmosphere. In this way, the phase and crystal lattice spacing of the product can be unexpectedly adjusted, so as to adapt to the requirements of carbon dioxide capture and reduction catalysis, and can significantly improve the efficiency and effect of catalytic reduction of carbon dioxide to carbon monoxide.

[0012] The preparation method of the present invention can endow the material with special phase, crystal, grain boundary and other characteristics, and the material prepared by the preparation method can meet the requirements of carbon dioxide capture and reduction catalysis, and significantly improve the yield of carbon monoxide.

[0013] Further, in Step 1, the Ca source is any component capable of providing Ca material, for example, optionally at least one of calcium oxides, carbonates, bicarbonates, nitrates, organic acid salts;

[0014] The M is one or more of alkali metals, alkaline earth metals, transition metals, including but not limited to sodium, magnesium, potassium, iron, manganese, nickel, copper, cerium, cobalt, zirconium, aluminum, etc.;

[0015] The M source is at least one of oxides, carbonates, bicarbonates, nitrates, organic acid salts of M-containing metals;

[0016] Preferably, the M is a multi-element combination of elements such as iron, nickel, cerium, magnesium, zirconium, etc.; It is unexpectedly shown by research that using the combined M of iron, nickel, cerium, magnesium, zirconium can further cooperate with the process synergistically, which helps to further jointly control the structure of the product, making it exhibit better carbon dioxide capture and reduction activities and the cyclic stability of the bifunctional material. When the M is a multi-element combination of elements such as iron, nickel, cerium, magnesium, etc., there is no special requirement for the ratio between the elements, for example, it can be 2:1:3:5.

[0017] The complexing agent is at least one of citric acid, ethylene glycol, glycine, nitrilotriacetic acid, ethylenediaminetetraacetic acid;

[0018] The Ca / M element content ratio of the Ca source and the M source is 1:0.5 to 5, and further can be 1:2 to 4;

[0019] The weight ratio of the Ca source and the complexing agent is 1:0.5 to 1, and further can be 1:0.6 to 0.8.

[0020] Further, in step one, the solvent for the pre-reaction is water or a mixed solvent of water-organic solvent; the organic solvent is methanol, ethanol, acetone, tetrahydrofuran, etc.;

[0021] The temperature of the pre-reaction (also known as the gelation reaction) is 50 to 90 °C, and the time is 2 to 3 h;

[0022] The way of desolvation (also known as aging) is, for example, evaporation, freeze-drying, extraction, distillation, centrifugation, membrane adsorption, etc. Among them, the evaporation process can be carried out under normal pressure or negative pressure. The temperature of the desolvation process is, for example, 150 to 200 °C.

[0023] Further, in step two, the atmosphere for the calcination is an oxygen-containing atmosphere, which can be oxygen, or a mixture of oxygen and other gases (such as nitrogen, argon, etc.). Considering the simplicity of the treatment process and cost, it can be further air;

[0024] The temperature of the calcination is 600 to 800 °C; in the present invention, the regulation of the product phase and crystal spacing can be achieved at this relatively low temperature, so as to make it more suitable for the application requirements of carbon dioxide capture and reduction.

[0025] The time of the calcination is 3 to 8 h, and further can be 4 to 5 h.

[0026] Further, in step two, before the calcination, pre-calcination is carried out at a temperature of 250 to 400 °C; in the present invention, pre-calcining the precursor and then carrying out the calcination treatment can further facilitate the regulation of the physical and chemical characteristics such as the crystal spacing of the product, making it more suitable for carbon dioxide capture and reduction, and further improving its carbon dioxide reduction effect. The time of the pre-calcination is 0.5 to 2 h, preferably 1 to 1.5 h.

[0027] Further, in step three, the content of hydrogen in the hydrogen-containing atmosphere is 20 to 100 vol.%, and further can be 30 to 60 vol.%; the temperature of the thermal modification is 500 to 850 °C, and further preferably 600 to 800 °C; the time is 1 to 4 h.

[0028] A Ca / M multi-metal bifunctional material prepared by the above preparation method.

[0029] Application of the Ca / M multi-metal bifunctional material prepared by the above preparation method, said application being: using the Ca / M multi-metal bifunctional material to capture carbon dioxide in the waste gas containing carbon dioxide, and then performing reduction treatment in a hydrogen-containing atmosphere to collect the CO product in the reduction stage.

[0030] Further, the waste gas containing carbon dioxide can be any gas with a carbon dioxide recovery requirement. In the waste gas containing carbon dioxide, the carbon dioxide content is 5-30%, the nitrogen oxides are <500 mg / m 3 , the sulfur dioxide is <1000 mg / m 3 , and the particulate matter is <100 mg / m 3 ; the temperature for capture is 25-750 °C, and considering the treatment efficiency, it can be further 500-700 °C, and the time is 10-60 min; in the hydrogen-containing atmosphere, the hydrogen content is 20-100 vol.%, and it can be further 40-60 vol.%, the temperature for the reduction treatment is 550-750 °C, and it can be further 600-700 °C, and even further 630-670 °C, and the time is 10-70 min.

[0031] Further, before capture, the Ca / M multi-metal bifunctional material is preferably pre-activated with a hydrogen-containing atmosphere, and then capture and subsequent reduction treatment are carried out; in the present invention, before carbon dioxide capture-reduction, it can be preferably pre-activated with a hydrogen-containing atmosphere. Among them, the activation temperature is 550-750 °C (further can be 600-700 °C), and the time is 0.1-2 h (further can be 0.5-1 h). Preferably, the above-mentioned capture and reduction treatments are carried out cyclically.

[0032] The beneficial effects of the present invention compared with the prior art are as follows:

[0033] 1. The Ca / M multi-metal bifunctional material prepared by the present invention not only has excellent catalytic reduction activity, but also has excellent structural stability and regeneration ability, and it can be used for cyclically carrying out capture and reduction treatment to realize the cyclic capture and reduction of carbon dioxide.

[0034] 2. The present invention pre-calcines the Ca source and M source at a temperature of 500-850 °C, and then performs thermal modification in a hydrogen-containing atmosphere, so that the crystal spacing and other physical and chemical structural characteristics of the prepared material can be unexpectedly improved, and further the activity of carbon dioxide capture and reduction to carbon monoxide can be improved.

[0035] 3. In the present invention, under the preferred process, the crystal characteristics of the product can be further optimized to make it more suitable for the application requirements of carbon dioxide capture and reduction.

[0036] 4. Research shows that the Ca / M multi-metal bifunctional material described in the present invention has good stability during the adsorption-calcination cycle, enabling the single-cycle production of CO to reach 8.5 mmol / g. After 15 cycles of experiments, the cumulative production of CO is 125 mmol / g, and the CO selectivity remains 99%. The above advantages endow the present invention with excellent material stability. Detailed Embodiments

[0037] The present invention will be further described below in conjunction with embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described below, and those skilled in the art can make various modifications or alterations within the scope of the claims.

[0038] An optional preparation method of the Ca / M multi-metal bifunctional material of the present invention comprises the following steps:

[0039] In the first step, a Ca source, an M source, and a complexing agent (citric acid) are dissolved in deionized water to form a mixed solution containing metal ions. Among them, the Ca / M element content ratio of the Ca source to the M source is 1:1 to 5;

[0040] In the second step, it is heated in a water bath at 60 - 90 °C and continuously stirred, and then desolvated at 160 - 200 °C for 2 - 10 h to obtain a precursor;

[0041] In the third step, the precursor is calcined in a muffle furnace under an air atmosphere at 500 - 850 °C, more preferably at 600 - 800 °C, to obtain a precursor material.

[0042] In the fourth step, the precursor material is thermally modified in a hydrogen-containing atmosphere to obtain the Ca / M multi-metal bifunctional material.

[0043] Another object of the present invention is to provide a method for integrating CO₂ capture and utilization using the novel Ca / M multi-metal bifunctional material of the present invention, enabling the novel Ca / M multi-metal bifunctional material of the present invention to contact industrial flue gas at a temperature of 400 - 800 °C to capture carbon dioxide therein, and then catalytically reduce it in a hydrogen-containing atmosphere at a temperature of 400 - 800 °C to prepare CO. A further preferred application method of the present invention is to pre-activate the Ca / M multi-metal bifunctional material in a hydrogen-containing atmosphere, then mix it with a carbon dioxide-containing atmosphere for capture, and then reduce it in a hydrogen-containing atmosphere.

[0044] In the present invention, the above-mentioned carbon dioxide capture and reduction processes can be repeated.

[0045] In the present invention, at the laboratory stage, a composite gas of carbon dioxide - Ar is used as the test simulation gas.

[0046] Example 1

[0047] Step a. Preparation of multi-metal FeNiCeMgCa material

[0048] a-1: Mix calcium carbonate (Ca source), iron nitrate, nickel nitrate, cerium nitrate, magnesium nitrate (M source), and citric acid (the weight ratio of calcium carbonate to citric acid is 50:30, and the weight ratio of Ca / M element is 1:4, iron:nickel:cerium:magnesium = 2:1:3:5) in deionized water, react at 60 - 70°C for 3 - 4 h by water bath heating, then carry out desolvation at 160 - 170°C to obtain a precursor, and then calcine the precursor in an air atmosphere at 600°C for 5 h to obtain a precursor catalyst;

[0049] a-2: Place the precursor catalyst in a H2-Ar mixed atmosphere (hydrogen content is 30 vol.%) and keep it heat-modified at 650°C for 2 h to prepare a Ca / M multi-metal bifunctional material.

[0050] Step b. Detection of CO2 capture and conversion performance

[0051] Use a serial fixed-bed experimental bench to detect the effect of the synthesized Ca / M multi-metal bifunctional material on capturing and utilizing carbon dioxide. The quartz tube used in the fixed bed is 400 mm long and 10 mm in inner diameter, and the controlled temperature range is 400 - 800°C. Before the experiment, place 0.06 - 0.08 g of quartz wool in the quartz tube, and then load 0.1 g of the Ca / M composite material. The experimental gas conditions are 10% CO2 / Ar, 30% H2 / Ar, and pure Ar for purging. Control the gas components fed in through a mass flowmeter, control the total flow rate to be 200 mL / min, and the gas enters the fixed bed through the pipeline for the experiment after mixing.

[0052] First, introduce the CO2 / Ar for 30 min (the temperature in the treatment stage is T, and keep the temperature T for the capture time), after the adsorption ends, introduce Ar again for purging, and finally introduce the H2 / Ar to carry out the carbon dioxide reduction conversion experiment until the CO2 is completely converted (the temperature in the treatment stage is T, and keep the temperature T for the reduction conversion time). The cyclic experiment repeats the gas switching of purging, adsorption, and reaction processes. The components and concentrations of the consumed and generated gases during the experiment are measured by a non-dispersive infrared analyzer. The instrument measurement error is linearly calibrated by standard gases with different concentrations, and the error is less than ±3% of the total range. The measured active temperature range is 550 - 700°C. Among them, when the temperature T is 650°C, the highest single-cycle yield of CO is 8.5 mmol / g, and the total yield of CO after 15 cycles is 125 mmol / g, and the CO selectivity remains 99%.

[0053] Example 2

[0054] Compared with Example 1, the only difference is that the type of M source is changed. The ratios of M and Ca in the M source are the same as those in Example 1. The experimental groups are as follows:

[0055] Group A: The M source is magnesium nitrate;

[0056] Group B: The M source is ferric nitrate + nickel nitrate + cerium nitrate, where the mass ratio of iron / (nickel + cerium) elements is 1:2;

[0057] Group C: The M source is magnesium nitrate + ferric nitrate

[0058] Group D: The M source is magnesium nitrate + nickel nitrate

[0059] Group E: The M source is magnesium nitrate + cerium nitrate

[0060] Test according to the method described in Example 1, and the results are as follows:

[0061] Group A: The active temperature range is 580 - 680 °C, and the total CO production at a temperature of 650 °C is 7.8 mmol / g.

[0062] Group B: The active temperature range is 560 - 690 °C, and the total CO production at a temperature of 650 °C is 5.8 mmol / g.

[0063] Group C: The active temperature range is 550 - 680 °C, and the total CO production at a temperature of 650 °C is 6.2 mmol / g.

[0064] Group D: The active temperature range is 500 - 670 °C, and the total CO production at a temperature of 650 °C is 7.3 mmol / g.

[0065] Group E: The active temperature range is 580 - 700 °C, and the total CO production at a temperature of 650 °C is 7.5 mmol / g.

[0066] It can be seen from the comparison between Example 1 and Example 2 that by using the combination of M and Ca and the described preparation process, excellent carbon dioxide capture and conversion capabilities can be obtained. Especially when using the combination of Mg and other metal elements as the M source, a more excellent synergistic effect can be unexpectedly obtained.

[0067] Example 3

[0068] Compared with Example 1, the only difference is that the dosage of the Ca source remains unchanged, and the metal ratio in the M source is iron: nickel: cerium: magnesium = 2:3:1:5. Other operations and parameters are the same as those in Example 1:

[0069] Test according to the method described in Example 1, and the result is: the total CO production at a temperature of 650 °C is 7.7 mmol / g.

[0070] Example 4

[0071] Compared with Example 1, the difference is only that the calcination temperature in step a is changed to 700 °C, the time is 4 h, the hydrogen content in the atmosphere of thermal modification is 60 vol.%, the temperature of thermal modification is 700 °C, and the time is 3 h. Other operations and parameters are the same as those in Example 1.

[0072] It is found by testing that the total CO output at 650 °C is 8.0 mmol / g.

[0073] Example 5

[0074] Compared with Example 1, the difference is only that during the calcination process in step a-1, the precursor is first heated to 300 °C and kept warm for 1 h, and then heated to 600 °C and kept warm for 4 h to obtain the precursor catalyst. Other operations and parameters are the same as those in Example 1.

[0075] It is found by testing that the total CO output at 650 °C is 8.8 mmol / g.

[0076] It can be seen from Example 1 and Example 5 that by adopting the two-stage gradient process of the present invention, the CO2 capture and conversion performance of the material can be further improved, making it more suitable for the requirements of carbon dioxide capture and reduction, and further improving its reduction effect.

[0077] Example 6

[0078] Compared with Example 1, the difference is only that in step (b), before introducing the CO2 / Ar capture, 40 vol.% hydrogen-Ar atmosphere is introduced into the system in advance, and it is kept warm and activated at 600 °C for 30 min, and then subsequent treatment is carried out. Other operations and parameters are the same as those in Example 1.

[0079] Tested according to the method described in Example 1, the result is: the total CO output at 650 °C is 8.3 mmol / g.

[0080] Comparative Example 1

[0081] Compared with Example 1, the difference is only that the calcium source is missing, and the missing part is supplemented equally by the M source. Other operations and parameters are the same as those in Example 1

[0082] Tested according to the method of Example 1, the result is that the total CO output at 650 °C is 0.2 mmol / g.

[0083] Comparative Example 2

[0084] Compared with Example 1, the difference is only that the M source is missing, and the missing part is supplemented equally by the calcium source. Other operations and parameters are the same as those in Example 1

[0085] The test was carried out according to the method of Example 1, and the result was that the total CO output was 5.5 mmol / g at a temperature of 650 °C.

[0086] Comparative Example 3:

[0087] Compared with Example 1, the difference is only that the amount of calcium source is kept unchanged, and the ratio of M / Ca is not controlled within the required range. The experimental groups are, for example:

[0088] Group A: The elemental ratio of Ca / M is 1:2;

[0089] Group B: The ratio of Ca / M is 1:6;

[0090] The test was carried out according to the method described in Example 1, and the results were as follows:

[0091] Group A: The total CO output was 7.3 mmol / g at a temperature of 650 °C.

[0092] Group B: The total CO output was 5.9 mmol / g at a temperature of 650 °C.

[0093] Comparative Example 4

[0094] Compared with Example 1, the difference is only that the calcination temperature is 400 °C, and other operations and parameters are the same as in Example 1.

[0095] The test was carried out according to the method of Example 1, and the result was that the total CO output was 4.3 mmol / g at a temperature of 650 °C.

[0096] Comparative Example 5

[0097] Compared with Example 1, the difference is only that citric acid is missing, and other operations and parameters are the same as in Example 1.

[0098] The test was carried out according to the method of Example 1, and the result was that the total CO output was 4.1 mmol / g at a temperature of 650 °C.

[0099] Comparative Example 6

[0100] Compared with Example 1, the difference is only that the reduction treatment step is missing. That is, the thermal modification gas is changed from hydrogen to air, and the time is also 2 h;

[0101] The test was carried out according to the method described in Example 1, and the results were as follows: The total CO output was 7.7 mmol / g at a temperature of 650 °C.

Claims

1. A preparation method of a Ca / M multi-metal bifunctional material, characterized in that: The method is as follows: Step 1: Pre-react the Ca source, M source and complexing agent and then remove the solvent to obtain a precursor. Step 2: Calcinate the precursor at a temperature of 500 - 850 °C to obtain a precursor material. Step 3: Thermally modify the precursor material in a hydrogen-containing atmosphere to prepare a Ca / M multi-metal bifunctional material.

2. The preparation method of a Ca / M multi-metal bifunctional material according to claim 1, characterized in that: In Step 1, the Ca source is at least one of calcium oxides, carbonates, bicarbonates, nitrates, and organic acid salts. The M is one or more of alkali metals, alkaline earth metals, and transition metals. The M source is at least one of oxides, carbonates, bicarbonates, nitrates, and organic acid salts of metals containing M. The complexing agent is at least one of citric acid, ethylene glycol, glycine, nitrilotriacetic acid, and ethylenediaminetetraacetic acid. The Ca / M element content ratio of the Ca source and the M source is 1:0.5 - 5. The weight ratio of the Ca source to the complexing agent is 1:0.5 - 1.

3. The preparation method of a Ca / M multi-metal bifunctional material according to claim 1, characterized in that: In Step 1, the solvent for the pre-reaction is water or a mixed solvent of water - organic solvent; the organic solvent is methanol, ethanol, acetone, tetrahydrofuran, etc. The temperature of the pre-reaction is 50 - 90 °C, and the time is 2 - 3 h. The method of removing the solvent is evaporation, freeze-drying, extraction, distillation, centrifugation, membrane adsorption, etc.

4. The preparation method of a Ca / M multi-metal bifunctional material according to claim 1, characterized in that: In Step 2, the atmosphere for calcination is an oxygen-containing atmosphere. The temperature of the calcination is 600 - 800 °C, and the calcination time is 3 - 8 h.

5. The preparation method of a Ca / M multi-metal bifunctional material according to claim 1 or 4, characterized in that: In Step 2, before calcination, pre-calcine at a temperature of 250 - 400 °C in advance, and the pre-calcination time is 0.5 - 2 h.

6. The preparation method of a Ca / M multi-metal bifunctional material according to claim 1, characterized in that: In Step 3, the hydrogen content in the hydrogen-containing atmosphere is 20 - 100 vol.%; the temperature of the thermal modification is 500 - 850 °C, and the time is 1 - 4 h.

7. A Ca / M multi-metal bifunctional material prepared by the preparation method according to any one of claims 1 - 6.

8. Use of the Ca / M multi-metal bifunctional material prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The application is as follows: Use the Ca / M multi-metal bifunctional material to capture carbon dioxide in the waste gas containing carbon dioxide, and then perform reduction treatment in a hydrogen-containing atmosphere to collect the CO product in the reduction stage.

9. The application according to claim 8, wherein: In the waste gas containing carbon dioxide, the carbon dioxide content is 5-30%, nitrogen oxides <500 mg / m 3 , sulfur dioxide <1000 mg / m 3 , particulate matter <100 mg / m 3 ; the temperature for capture is 25-750 °C and the time is 10-60 min; in the hydrogen-containing atmosphere, the hydrogen content is 20-100 vol.%, and the temperature for reduction treatment is 550-750 °C and the time is 10-70 min.

10. The application according to claim 8 or 9, characterized in that: Before capture, pre-activate the Ca / M multi-metal bifunctional material with a hydrogen-containing atmosphere, and the activation temperature is 550 - 750 °C, and the time is 0.1 - 2 h.