CuO supported LaCeOx catalyst for removing CO from hydrogen-rich gas, and preparation method and application thereof

Abstract

This invention discloses a CuO-supported LaCeOx catalyst for removing CO from hydrogen-rich gas, its preparation method, and its application. The CuO-supported LaCeOx catalyst is a CuO / La-CeO2 catalyst, comprising a support and an active component. The support is La-doped CeO2, and the active component is CuO. Based on the total mass of the support, the loading of CuO is 10–30 wt.%, and the doping amount of La is 5–20 wt.%. This invention uses cerium oxide (CeO2) as the matrix. La doping into the CeO2 bulk phase promotes the interaction with CuO, resulting in the formation of additional low-coordinate Cu at the interface sites for CO adsorption. ξ+ This enhances the anchoring effect on CO in hydrogen-rich gases and improves the selectivity of the reaction. This invention is particularly suitable for the deep removal of CO from hydrogen-rich gases.

Description

Technical Field

[0001] This invention belongs to the field of energy and chemical technology / catalysis, and relates to a CuO-supported LaCeOx catalyst for removing CO from hydrogen-rich gas, its preparation method and application, and more specifically to a CuO / La-CeO2 catalyst, its preparation method and application for highly selective removal of CO from hydrogen-rich gas. Background Technology

[0002] A fuel cell is a power generation device that utilizes H2 and O2. It can efficiently and environmentally convert hydrogen energy stored in fuel into electrical energy without a heat engine process, and is not limited by the Carnot cycle. It has high energy conversion efficiency and is an ideal energy utilization method, widely used in transportation and other fields. Currently developed proton exchange membrane fuel cells (PEMFCs) generally use methanol as raw material. The H2 produced by the methanol-water reforming reaction contains a small amount of CO impurities. Trace amounts of CO are preferentially adsorbed on the anode of PEMFCs, poisoning the Pt electrode, reducing the lifespan of the fuel cell, and affecting its operating efficiency.

[0003] Currently, numerous H2 purification strategies have been developed, such as selective CO oxidation, selective CO methanation, high / low temperature water-gas shift, palladium membrane purification, and pressure swing adsorption (PSA). Among these, selective CO oxidation is the most economical and effective method for removing CO from hydrogen-rich gases. This involves selectively catalytically oxidizing CO by introducing a small amount of O2 or air into the hydrogen-rich gas, minimizing H2 loss. CO-PROX technology is used to purify H2 produced by methanol steam reforming, reducing the CO concentration to within the tolerance range of PEMFC electrodes (<10 ppm). The preparation and development of highly efficient catalysts are the core technologies of CO-PROX; the catalytic material should possess both excellent CO conversion rate and CO2 selectivity.

[0004] However, current catalysts for the PROX reaction still have the following problems: 1. Current research focuses mainly on the structural design and microscopic characterization of reaction mechanisms of innovative catalytic materials. To avoid considering the competitive oxidation of H2 and optimizing reaction selectivity, existing studies usually use 50 vol.% H2 to simulate the PROX reaction gas, with Ar or He as the equilibrium gas. In practical applications, the proportion of H2 produced by methanol-water reforming is 70-75 vol.%, far higher than the reported H2 (50 vol.%). This is far from the actual application conditions, thus avoiding the problem of competitive oxidation of hydrogen. 2. Current research usually uses 100 ppm CO as the tolerance standard for fuel cell electrodes, but PEMFCs should be able to tolerate a CO concentration of less than 10 ppm for long-term operation, which obviously idealizes the PROX reaction. 3. Current research mostly chooses metal oxides as additives to regulate the activity of CuO / CeO2 catalysts. The active component, support, and additive each exist in the form of metal oxides, and the crystals are phase-separated. The study of ternary components increases the complexity of catalytic materials. Activity analysis needs to consider various combinations, such as the interaction between the active component and the support, the interaction between the active component and the promoter, the interaction between the promoter and the support, and the interaction among the active component, the support, and the promoter.

[0005] Therefore, it is desirable to prepare catalysts with high catalytic activity and high selectivity through simple preparation methods for the deep removal of CO from reaction gases with a high hydrogen content.

[0006] The present invention aims to solve the above-mentioned problems. Summary of the Invention

[0007] This invention aims to overcome the shortcomings of existing technologies. Addressing the issues of competitive oxidation by hydrogen in the PROX reaction when the hydrogen content is high, and the difficulty in achieving deep CO removal, this invention uses cerium oxide (CeO2) as the matrix. By doping La into the CeO2 bulk phase, the interaction with CuO is promoted, and the interfacial sites generate additional low-coordinate Cu for CO adsorption. ξ+ This enhances the anchoring effect on CO in hydrogen-rich gases and improves the selectivity of the reaction. This invention is particularly suitable for the deep removal of CO from hydrogen-rich gases.

[0008] The technical solution adopted in this invention is as follows:

[0009] The first aspect of this invention provides a CuO-supported LaCeOx catalyst for removing CO from hydrogen-rich gas. The CuO-supported LaCeOx catalyst is a CuO / La-CeO2 catalyst, comprising a support and an active component. The support is La-doped CeO2, and the active component is CuO. Based on the total mass of the support, the loading of CuO is 10–30 wt.%, and the doping amount of La is 5–20 wt.%.

[0010] Preferably, the CuO loading is 10–30 wt.% based on the total mass of the catalyst, and the La doping amount is 10 wt.% based on the total mass of the support.

[0011] The second aspect of this invention provides a method for preparing the catalyst described in the first aspect of this invention, wherein La-Ce is first prepared by a hydrothermal method. O2 The carrier is then used to load CuO active components onto the carrier using an impregnation method.

[0012] Preferably, the method for preparing the catalyst includes the following steps:

[0013] (1) Dissolve the La source and Ce source in deionized water to prepare a precursor solution of La and Ce, and add it dropwise to an alkaline solution to prepare an alkaline suspension;

[0014] (2) The alkaline suspension obtained in step (1) is then transferred to a reaction vessel for hydrothermal reaction.

[0015] (3) The reactants obtained in step (2) are washed until the pH of the washing solution is 7-10. The precipitate is dried, ground and then calcined to obtain the La-CeO2 support.

[0016] (4) Dissolve the Cu source in deionized water to prepare a Cu precursor solution. Then grind and sieve the La-CeO2 support obtained in step (3), disperse it in deionized water, mix it with the Cu precursor solution, dry it initially, place it in an oven to dry, grind it, and calcine it to obtain the CuO / La-CeO2 catalyst.

[0017] Preferably, in step (1), the alkaline solution is a NaOH solution;

[0018] The La source is selected from at least one of lanthanum nitrate, lanthanum chloride, lanthanum acetate, and lanthanum sulfate; the Ce source is selected from at least one of cerium nitrate, cerium oxalate, cerium chloride, and cerium sulfate.

[0019] The molar concentration of the NaOH solution is 18–25 mol / L;

[0020] The volume ratio of NaOH solution to precursor salt solution is 0.5–0.8, and the concentration of the precursor solution is: the ratio of the total mass of La source and Ce source to deionized water is (1.8–2.5) g: (25–50) mL.

[0021] Preferably, in step (2), the stirring time is 0.5 to 2 hours; the hydrothermal reaction temperature is 90 to 110°C; and the hydrothermal reaction time is 20 to 26 hours.

[0022] Preferably, in step (3), the product is washed by centrifugation with deionized water;

[0023] The drying temperature is 60–100℃, the drying time is 18–24 h, the calcination temperature is 400–600℃, and the calcination time is 1.5–3 h.

[0024] Preferably, in step (4), water bath evaporation is used for preliminary drying;

[0025] The Cu source is selected from at least one of copper nitrate, copper sulfate, copper acetate and copper oxalate. The water bath temperature is 60-80℃, the drying temperature is 60-100℃, the drying time is 18-24h, the calcination temperature is 300-500℃, and the calcination time is 1.5-3h.

[0026] The dispersion method is ultrasonic dispersion, with an ultrasonic frequency of 60–120 kHz and an ultrasonic dispersion time of 10–30 min;

[0027] The amount of Cu source is controlled so that the mass ratio of CuO to La-CeO2 is 0.10 to 0.30, that is, based on the total mass of the support, the loading of CuO is 10 to 30 wt.%.

[0028] A third aspect of the present invention provides an application of the catalyst described in the first aspect of the present invention, using it as a catalyst for the removal of CO from a hydrogen-rich gas, wherein the hydrogen-rich gas has a hydrogen content of 20-70 vol.%, more preferably 50-70 vol.%.

[0029] Preferably, after removal, the CO concentration in the hydrogen-rich gas is less than 10 ppm, and the CO2 selectivity in the product is greater than 50%.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. This invention uses cerium oxide (CeO2) as a matrix and modifies it by doping with La species, inducing changes in the surface properties of CeO2 and promoting its interaction with CuO. The interfacial sites generate additional low-coordinate Cu for CO adsorption. ξ+ This enhances the anchoring effect on CO in hydrogen-rich gas and improves the selectivity of the reaction.

[0032] 2. The preparation method of this invention uses CuO as the active component. The synthesized CuO / La-CeO2 catalyst achieves highly selective catalytic oxidation of CO with a 0-70 vol.% H2 content within the temperature range of 100-110℃, reducing the CO concentration to below 10 ppm and achieving a CO2 selectivity of over 50%. This suppresses the competitive oxidation of H2 and CO, reducing H2 loss while achieving CO purification standards. This lays a solid foundation for further promoting the industrial production, synthesis, and application of CuO / CeO2 type catalytic materials.

[0033] Even under conditions where the H2 content in the reaction gas is as high as 70 vol.%, the catalyst of this invention can achieve deep purification and removal of CO, reducing the CO concentration to below 10 ppm while maintaining a selectivity of over 50%. The 70 vol.% H2 content in the reaction gas more realistically simulates the actual methanol-water reforming reaction gas composition. Current research typically uses 50 vol.% H2 to simulate the PROX reaction gas, with Ar or He as the equilibrium gas, which differs significantly from actual application conditions. This avoids the problem of analyzing competitive oxidation and idealizes the PROX reaction.

[0034] 3. In this invention, La is doped into the CeO2 support. The La-CeO2 support exists as a single crystalline phase, without the formation of La2O3 crystals. The doping control method involved in this patent ensures that the catalytic material remains a binary component, namely the active component and the support, simplifying the complexity of the catalytic system and facilitating the analysis of the source of activity and the interaction between the catalytic components.

[0035] 4. The CuO / La-CeO2 involved in this invention has advantages over traditional noble metal-based catalysts, such as low price, simple synthesis process, wide tolerance for operational errors, and no need for atmosphere pretreatment. Attached Figure Description

[0036] Figure 1 This is a flowchart of catalyst synthesis.

[0037] Figure 2 The CO conversion and CO2 selectivity of the PROX reaction catalyzed by CuO / La-CeO2 and CuO / CeO2 are shown.

[0038] Figure 3 Stability test of CuO / La-CeO2 in a PROX atmosphere of 70 vol.% H2.

[0039] Figure 4 This is the in-situ transmission infrared absorption spectrum of CO catalytic oxidation.

[0040] Figure 5 Comparison of X-ray powder diffraction spectra of La-CeO2 and CeO2 support.

[0041] Figure 6 The CO conversion rates of different samples under different catalytic conditions are shown. Detailed Implementation

[0042] The present invention will be further described below through embodiments, but is not limited to these embodiments. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in manuals, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified.

[0043] The specific steps of the method described in this invention are as follows:

[0044] Example 1

[0045] (1) Dissolve 1.95g of cerium nitrate hexahydrate and 0.17g of lanthanum nitrate in 10mL of deionized water and stir evenly until completely dissolved; prepare a NaOH precipitant solution by weighing 25g of NaOH and dissolving it in 30mL of deionized water and stirring until completely dissolved; add the above mixed solution of cerium nitrate and lanthanum nitrate dropwise to the NaOH solution, and a purple-white flocculent precipitate will be formed by the reaction. Continue stirring for 1h.

[0046] (2) Transfer the above reaction solution to a reaction vessel, add deionized water to 100 mL, and perform hydrothermal reaction for 24 h at a hydrothermal temperature of 100 °C. After the reaction is completed and the temperature is lowered, collect the substrate.

[0047] (3) The above substrate was washed by vacuum filtration until the pH of the eluent was 8, and the filter cake was collected. It was then dried in an oven at 80°C for 24 hours and ground into powder with a particle size of less than 200 mesh. The powder was spread evenly in a crucible and calcined at 500°C for 2 hours to obtain pale yellow La-CeO2. Batch synthesis was achieved by repeating or scaling up the process proportionally.

[0048] (4) Dissolve 0.24g of copper nitrate trihydrate in 10mL of deionized water to make a copper nitrate solution; at the same time, weigh 1g of La-CeO2 carrier and ultrasonically disperse it in 20mL of deionized water to make a carrier turbidity.

[0049] (5) Mix the copper nitrate solution prepared in (4) with the La-CeO2 turbid liquid, stir and dry under water bath heating at 60°C, transfer the semi-dry paste to an oven at 80°C and dry for 24 hours, and calcine at 400°C for 2 hours after thorough drying to obtain CuO / La-CeO2 catalyst with a CuO loading of 10 wt.%.

[0050] Example 2

[0051] Control of CuO loading: The experimental method for preparing and synthesizing La-CeO2 was the same as steps (1, 2, 3) in Example 1, except that the amount of copper nitrate trihydrate was adjusted to 0.47 g and 0.70 g, respectively. 1 g of La-CeO2 support was weighed, and subsequent processing steps were the same. CuO / La-CeO2 catalyst samples with CuO loadings of 20 wt.% and 30 wt.% were synthesized.

[0052] Adjustment of La doping concentration: The amounts of cerium nitrate hexahydrate and lanthanum nitrate reagent (1.95 g + 0.17 g) in Example 1 were adjusted to 2.06 g + 0.08 g and 1.74 g + 0.33 g, respectively, with the remaining steps remaining the same. CuO / La-CeO2 catalyst samples with La doping concentrations of 5 wt.% and 20 wt.% were synthesized.

[0053] Comparative Example 1

[0054] 2.17 g of cerium nitrate hexahydrate was dissolved in 10 mL of deionized water and stirred evenly until completely dissolved. The remaining steps were the same as in Example 1 to prepare the comparative catalyst CuO / CeO2.

[0055] 0.50 g of the CuO / La-CeO2 catalyst prepared in Example 1 was placed in a fixed-bed reactor. The CO-PROX reaction gas composition was 1 vol.% CO, 2 vol.% O2, and 20–70 vol.% H2. An N2 balance gas was prepared, with a total flow rate of 100 mL / min. The CO conversion and CO2 selectivity under different H2 ratios at 100℃ and 110℃ are shown in the attached figure. Figure 2 The left figure is shown. Experiments show that the CuO / La-CeO2 catalyst prepared in this example achieved nearly 100% CO conversion and consistently higher than 50% CO2 selectivity within a H2 variation range of 20–70 vol.%. Figure 3 In stability tests, the CuO / La-CeO2 catalyst achieved a CO purification efficiency of less than 10 ppm and a CO2 selectivity of over 50% for more than 6 hours at 110℃. The in-situ transmission infrared characterization results for CO oxidation are as follows: Figure 4 As shown, three CO infrared adsorption peaks exist on CuO / La-CeO2, corresponding to Cu... 2+ -CO(2180cm -1 Cu + -CO(2132cm -1 ), and Cu ξ+ -CO(2110cm -1 (0 < ξ < 1). Additional Cu ξ+ The site enhances the adsorption capacity for CO and improves the selectivity of the reaction. Figure 5The image shows a comparison of the X-ray powder diffraction spectra of La-CeO2 and CeO2 supports. Figure 5 It can be seen that the La-CeO2 support exists as a single crystalline phase, and no La2O3 crystals are observed.

[0056] 0.50 g of the comparative catalyst CuO / CeO2 was placed in a fixed-bed reactor. The CO-PROX reaction gas composition was 1 vol.% CO, 2 vol.% O2, and 20–70 vol.% H2. N2 balance gas was prepared, and the total flow rate was 100 mL / min. The CO conversion and CO2 selectivity under different H2 ratios at 100℃ and 110℃ were as follows: Figure 2 As shown in the right figure, the CO conversion rate is close to 100% within the range of H2 proportions; however, its CO2 selectivity remains at a low level, around 25%, indicating that competitive oxidation by H2 consumes a large amount of O2. The in-situ transmission infrared characterization results of CO oxidation are shown below. Figure 4 As shown, two distinct CO infrared adsorption peaks exist on CuO / CeO2, corresponding to Cu... 2+ -CO(2180cm -1 Cu + -CO(2132cm -1 Compared to CuO / La-CeO2, the additional Cu ξ+ -CO is not obvious and does not exist stably during the reaction.

[0057] Furthermore, catalytic activity tests were conducted using La-CeO2 with 10 wt.% La doping as the support, and CuO / La-CeO2 catalyst samples with CuO loadings of 20 wt.% and 30 wt.%; as well as CuO / La-CeO2 catalyst samples with 10 wt.% CuO loading and La dopings of 5 wt.% and 20 wt.% respectively. PROX catalytic activity tests were performed on these four samples. 0.50 g of each sample was placed in a fixed-bed reactor. The CO-PROX reaction gas composition was 1 vol.% CO, 2 vol.1% O2, and 70 vol.% H2, with N2 as the equilibrium gas, and a total flow rate of 100 mL / min. The CO conversion rates under different H2 ratios at 100℃ and 110℃ are shown in the attached figure. Figure 6 As shown, the experimental results indicate that, under the same test conditions, the above samples can achieve near-complete catalytic conversion of CO at 70 vol.% H2.

[0058] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. An application of a CuO-supported LaCeOx catalyst as a catalyst for the removal of CO from hydrogen-rich gas, characterized in that, The CuO-supported LaCeOx catalyst is a CuO / La-CeO2 catalyst, comprising a support and an active component. The support is La-doped CeO2, and the active component is CuO. Based on the total mass of the support, the loading of CuO is 10–30 wt.%, and the doping amount of La is 5–20 wt.%. The CuO-supported LaCeOx catalyst is used as a catalyst for the removal of CO from hydrogen-rich gas, wherein the hydrogen-rich gas has a hydrogen content of 50-70 vol.%. After removal, the CO concentration in the hydrogen-rich gas is less than 10 ppm, and the CO2 selectivity in the product is higher than 50%, which inhibits the competitive oxidation of H2 and CO, and reduces H2 loss while achieving the standard purification of CO.

2. The application according to claim 1, characterized in that, The CuO loading is 10 wt.% based on the total mass of the catalyst, and the La doping amount is 10 wt.% based on the total mass of the support.

3. The application according to claim 1, characterized in that, The preparation method of the CuO-supported LaCeOx catalyst is as follows: first, a La-CeO2 support is prepared by hydrothermal method, and then CuO active components are loaded on the support by impregnation method.

4. The application according to claim 3, characterized in that, Includes the following steps: (1) Dissolve the La source and Ce source in deionized water to prepare a La and Ce precursor solution, and add it dropwise to an alkaline solution to prepare an alkaline suspension; (2) The alkaline suspension obtained in step (1) is then transferred to a reaction vessel for hydrothermal reaction; (3) The reactants obtained in step (2) are washed until the pH of the washing solution is 7~10. The precipitate is dried, ground and then calcined to obtain the La-CeO2 support. (4) Dissolve the Cu source in deionized water to prepare a Cu precursor solution. Then grind and sieve the La-CeO2 support obtained in step (3), disperse it in deionized water, mix it with the Cu precursor solution, dry it initially, place it in an oven to dry, grind it, and calcine it to obtain the CuO / La-CeO2 catalyst.

5. The application according to claim 4, characterized in that, In step (1), the alkaline solution is a NaOH solution; The La source is selected from at least one of lanthanum nitrate, lanthanum chloride, lanthanum acetate, and lanthanum sulfate; the Ce source is selected from at least one of cerium nitrate, cerium oxalate, cerium chloride, and cerium sulfate. The molar concentration of the NaOH solution is 18~25 mol / L; The volume ratio of NaOH solution to precursor salt solution is 0.5~0.

8. The concentration of the precursor solution is: the ratio of the total mass of La source and Ce source to deionized water is (1.8~2.5) g: (25~50) mL.

6. The application according to claim 4, characterized in that, In step (2), the stirring time is 0.5~2 h; the hydrothermal reaction temperature is 90~110℃ and the hydrothermal reaction time is 20~26 h.

7. The application according to claim 4, characterized in that, In step (3), the product is washed by centrifugation with deionized water; The drying temperature is 60~100 ℃, the drying time is 18~24 h, the calcination temperature is 400~600 ℃, and the calcination time is 1.5~3 h.

8. The application according to claim 4, characterized in that, In step (4), water bath evaporation is used for preliminary drying; The Cu source is selected from at least one of copper nitrate, copper sulfate, copper acetate and copper oxalate. The water bath temperature is 60~80 ℃, the drying temperature is 60~100 ℃, the drying time is 18~24 h, the calcination temperature is 300~500 ℃, and the calcination time is 1.5~3 h. The dispersion method is ultrasonic dispersion, with an ultrasonic frequency of 60~120 KHz and an ultrasonic dispersion time of 10~30 min; The amount of Cu source is controlled so that the mass ratio of CuO to La-CeO2 is 0.10~0.30, that is, based on the total mass of the support, the loading of CuO is 10~30 wt.%.

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