Transition metal-modified co-selective oxidation catalysts, methods of making and using the same

Abstract

The application discloses a transition metal modified CO selective oxidation catalyst and a preparation method and application thereof, and relates to the technical field of catalytic materials. x The catalyst provided by the application comprises a carrier and an active component supported on the carrier, the carrier is Fe(OH) doped and modified by a transition metal, the transition metal is Co and / or Ni, and the active component is an active metal having CO catalytic oxidation activity. The catalyst can be prepared by a co-precipitation-impregnation one-step method. The catalyst provided by the application has excellent CO catalytic oxidation activity under water vapor conditions, can actively utilize water vapor in hydrogen-rich reforming gas, can dissociate water molecules adsorbed by the catalyst into surface active hydroxyl groups at a lower temperature, and the active hydroxyl groups can directly participate in the oxidation of CO, so that the catalytic oxidation conversion rate of CO is improved. In addition, the active hydroxyl groups can inhibit the accumulation of carbonate species on the surface of the catalyst, so that the poisoning effect of CO2 in the hydrogen-rich reforming gas on the catalyst is reduced.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and in particular to a transition metal-modified CO selective oxidation catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen-oxygen fuel cells directly convert chemical energy into electrical energy through the electrochemical reaction of hydrogen and oxygen. They have the advantages of being environmentally friendly and having high energy conversion efficiency, and have broad application prospects in the fields of new energy vehicles and distributed power generation. Currently, the main source of hydrogen relies on the steam reforming of hydrocarbons. This process inevitably produces a small amount of carbon monoxide (CO). CO has a strong poisoning effect on the anode of fuel cells, and even a small amount of CO can cause a sharp decline in battery performance. Therefore, the CO concentration must be reduced to an extremely low level before hydrogen-rich gas enters the battery.

[0003] CO-proximity oxidation (CO-PROX) technology is the preferred method for removing trace amounts of CO from hydrogen-rich gases. This technology introduces a small amount of air / oxygen into a hydrogen-rich atmosphere, relying on a specialized catalyst to preferentially oxidize trace amounts of CO to CO2, while minimizing the oxidation and consumption of valuable hydrogen. However, significant challenges remain in applying these laboratory-developed catalysts to practical industrial applications. On the one hand, the H2 content in reformed gases is typically as high as 70 vol.% or more. At such high H2 concentrations, how to prevent H2 from being competitively oxidized while oxidizing and removing CO is a crucial challenge. The key to the practicality of catalysts lies in the fact that reformed gas often contains excess water vapor (approximately 0-20 vol.%) and a certain amount of CO2 that has not been fully reformed. For most supported catalysts (such as traditional Pt-based or Au-based catalysts), H2O and CO2 are usually considered inhibitory factors, especially during low-temperature (50-80°C) start-up or low-load operation. H2O and carbonate species generated by the reaction of H2O and CO2 are highly likely to compete for adsorption on active sites, thereby blocking the activation reaction of CO and O2 and causing the catalyst to be "poisoned" and deactivated. Summary of the Invention

[0004] This invention provides a transition metal-modified Pt-Fe(OH) x Catalysts, their preparation methods, and applications are discussed, with the aim of improving the conversion rate of CO catalytic oxidation.

[0005] The transition metal-modified CO selective oxidation catalyst provided by this invention includes: carrier; Active components loaded on the carrier; The support is Fe(OH) doped with a transition metal. x The transition metal is Co and / or Ni, and the active component is an active metal with CO catalytic oxidation activity.

[0006] Optionally, the active metal is Pt; the total amount of the transition metal and Pt is 0.05 at.% to 1.5 at.% of the total amount of Fe, and the molar ratio of the transition metal to Pt is 1:1.

[0007] The transition metal-modified CO selective oxidation catalyst provided by this invention can be prepared by the following method, including the following steps: S1, dissolve Fe source, transition metal source and active metal source in deionized water to obtain a mixed metal salt solution; the transition metal source is Co source and / or Ni source, and the active metal source can be decomposed to obtain an active metal with CO catalytic oxidation activity; S2, add an alkaline precipitate to the mixed metal salt solution, adjust the mixed metal salt solution to a preset pH value, and obtain a suspension precipitate; S3, the suspended precipitate is heated and stirred to react, and then the reacted suspended precipitate is allowed to stand and age. The suspended precipitate after standing and aging is separated into solid and liquid to obtain precipitate. The precipitate is washed and dried to obtain catalyst precursor. S4. The catalyst precursor is subjected to reduction heat treatment under a reducing atmosphere to obtain the target catalyst.

[0008] Optionally, the Fe source is at least one of ferric nitrate, ferric sulfate, and ferric chloride; The Co source is at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt chloride; The Ni source is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride.

[0009] Optionally, the active metal source is a Pt source, and the Pt source is at least one of chloroplatinic acid, platinum nitrate, platinum sulfate, and platinum acetylacetonate. In terms of molar amount, the total amount of transition metal and Pt in the target catalyst is 0.05 at.% to 1.5 at.% of the total amount of Fe element, and the molar ratio of the transition metal to Pt is 1:1.

[0010] Optionally, the ratio of the mass of Fe source to the volume of deionized water in the mixed metal salt solution is (2~5) g: (15~30) mL.

[0011] Optionally, the alkaline precipitate is a 1-5 mol / L NaOH solution, and the preset pH value is 8-9.

[0012] Optionally, in step S3, the heating and stirring temperature is 60~85℃, the reaction time is 3~4h, the aging time is 1~3h, the drying temperature is 60~85℃, and the drying time is 18~24h.

[0013] Optionally, the reducing atmosphere is a mixture of H2 and a protective gas, wherein the protective gas is N2, Ar, or He; The H2 volume percentage in the reducing atmosphere is 10~25 vol.%, the gas flow rate of the mixed gas is 30~60 mL / min, the temperature of the reduction heat treatment is 200~250℃, and the treatment time is 30~60 min.

[0014] The transition metal-modified CO selective oxidation catalyst provided by this invention is suitable for selectively removing CO from hydrogen-rich gas, wherein the hydrogen-rich gas contains a predetermined volume percentage of hydrogen and water vapor.

[0015] Optionally, the hydrogen-rich gas contains approximately 70 vol.% H2 and approximately 10 vol.% water vapor by volume.

[0016] Optionally, the operating temperature of the transition metal-modified CO selective oxidation catalyst is 50~80℃.

[0017] The present invention has the following beneficial effects: The catalyst provided by this invention can actively utilize water vapor in hydrogen-rich reformed gas. The catalyst is Co / Ni-doped Fe(OH). x As a carrier of the active component, Co / Ni doping alters Fe(OH)₂. x The electronic structure of the surface allows water molecules adsorbed on the catalyst to dissociate at relatively low temperatures (50~80℃) to generate surface active hydroxyl groups. These active hydroxyl groups can directly participate in the oxidation of CO adsorbed on the catalytic active metal sites, and the oxidation activity of active hydroxyl groups for CO is significantly higher than that of gaseous molecular oxygen (O2), thereby improving the conversion rate of CO catalytic oxidation. At the same time, the abundant active hydroxyl groups on the catalyst surface can inhibit the accumulation of carbonate species on the catalyst surface, reduce the poisoning effect of CO2 in the reformed gas on the catalyst, and the catalyst can maintain stable operation for a long time. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The flowcharts are for some embodiments of the preparation method of the transition metal modified CO selective oxidation catalyst of the present invention. Figure 2 The Pt / Co-Fe(OH) obtained in Examples 1 and 2 of this invention. x and Pt / Ni-Fe(OH)x Stability test data of CO selective oxidation reaction in CO-PROX (H2O) atmosphere system; Figure 3 The Pt / Co-Fe(OH) obtained in Examples 1 and 2 of this invention. x and Pt / Ni-Fe(OH) x Graph of CO selective oxidation reaction activity test data in CO-PROX (MSR) atmosphere system; Figure 4 The Pt / Co-Fe(OH) obtained in Examples 1 and 2 of this invention. x and Pt / Ni-Fe(OH) x A graph showing the CO selective oxidation reaction activity test data after adjusting the introduction order of H2, CO2 and H2O; Figure 5 This is a graph showing the stability test data of the CO selective oxidation reaction of the control samples obtained in Comparative Examples 1 and 2 of this invention in the CO-PROX (MSR) atmosphere system; Figure 6 The Pt / Co-Fe(OH) ratios with different Pt-Co loadings obtained in Example 3 of this invention are examples of Pt / Co-Fe(OH) ratios. x Graph showing the stability test data of the CO selective oxidation reaction of the sample. Detailed Implementation

[0020] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Experimental methods in the embodiments of this invention that do not specify specific conditions are generally performed under conventional conditions and conditions described in the manual, or under conditions recommended by the manufacturer; the general equipment, materials, reagents, etc. used are commercially available unless otherwise specified.

[0022] The transition metal-modified CO (carbon monoxide) selective oxidation catalyst provided in this invention includes a support and an active component supported on the support, wherein the support is Fe(OH) doped with a transition metal. x , denoted as M-Fe(OH) xM represents a transition metal, which can be either Co (cobalt) or Ni (nickel), or both Co and Ni can be selected simultaneously. The active component is an active metal with CO catalytic oxidation activity, such as one or more noble metals including Pt (platinum), Pd (palladium), Ru (ruthenium), Rh (rhodium), and Au (gold). The active metal is anchored to M-Fe(OH) in a highly dispersed form. x On the surface and near the surface of the support, the active metal atoms and the Fe atoms and transition metal M atoms in the support can form a synergistic effect. The catalyst uses the self-heating effect of the reaction to activate H2O, converting H2O into hydroxyl active species that promote the CO oxidation reaction and resist the poisoning of CO2 on the catalyst, thereby achieving deep removal of CO from H2 reformed gas.

[0023] In some preferred embodiments, the active metal may be Pt, and the total amount of transition metal and Pt is 0.05 at.% to 1.5 at.% of the total amount of Fe, and the molar ratio of transition metal to Pt is 1:1.

[0024] In this embodiment of the invention, the transition metal-modified CO selective oxidation catalyst can be prepared by a one-step co-precipitation-impregnation method, which includes steps S1 to S4: S1, Fe source, transition metal source and active metal source are dissolved in deionized water to obtain a mixed metal salt solution; the transition metal source is Co source and / or Ni source, and the active metal source can be decomposed to obtain an active metal with CO catalytic oxidation activity.

[0025] The Fe source can be selected from one or more of ferric nitrate, ferric sulfate, and ferric chloride; the Co source can be selected from one or more of cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt chloride, and their corresponding hydrates; the Ni source can be selected from one or more of nickel nitrate, nickel sulfate, nickel acetate, nickel chloride, and their corresponding hydrates; the active metal can be selected from one or more of Pt, Pd, Ru, Rh, and Au, wherein the Pt source can be selected from at least one of chloroplatinic acid, platinum nitrate, platinum sulfate, and platinum acetylacetonate; the Pd source can be selected from at least one of palladium salts such as palladium chloride, hexachloropalladium, palladium nitrate, and palladium acetate; the Ru source can be selected from at least one of ruthenium salts such as ruthenium trichloride and ruthenium acetylacetonate; and the Rh source can be selected from at least one of rhodium salts such as rhodium trichloride, rhodium nitrate, rhodium acetylacetonate, and rhodium acetate.

[0026] In some specific embodiments, the ratio of the mass of Fe source to the volume of deionized water in the mixed metal salt solution is (2~5) g: (15~30) mL.

[0027] S2, add alkaline precipitate to the mixed metal salt solution, adjust the mixed metal salt solution to the preset pH value, and obtain a suspension precipitate.

[0028] The alkaline precipitate can be a 1-5 mol / L NaOH solution. The actual amount of NaOH solution used is approximately 3:1 molar ratio of Fe element in the mixed metal salt solution. NaOH solution is added dropwise to the mixed metal salt solution until the pH value of the mixed solution reaches 8-9, forming a suspension precipitate. In addition to NaOH solution, potassium hydroxide solution, ammonia water, or ammonium alkali sources can also be selected as alkaline precipitates.

[0029] S3, the suspended precipitate is heated and stirred to react, and then the reacted suspended precipitate is allowed to stand and age. The solid and liquid of the aged suspended precipitate are separated to obtain the precipitate. The precipitate is washed and dried to obtain the catalyst precursor.

[0030] In some specific embodiments, the heating and stirring temperature of this step is 60~85℃, the reaction time is 3~4h, the aging time is 1~3h, the drying temperature is 60~85℃, and the drying time is 18~24h.

[0031] S4. The catalyst precursor is subjected to reduction heat treatment under a reducing atmosphere to obtain the target catalyst.

[0032] In some specific embodiments, the catalyst precursor is ground (fineness less than 100 mesh) and then subjected to reduction heat treatment; the reducing atmosphere is a mixture of H2 and a protective gas, the protective gas being N2, Ar or He; the volume percentage of H2 in the reducing atmosphere is 10~25 vol.%, the gas flow rate of the mixture is 30~60 mL / min, the temperature of the reduction heat treatment is 200~250℃, and the treatment time is 30~60 min.

[0033] The above method generates a hydroxide precursor containing an active metal, a transition metal M (Ni and / or Co), and Fe through co-precipitation under alkaline conditions. After filtration, washing, and drying, the hydroxide precursor is activated under a specific temperature and reducing atmosphere to obtain the target catalyst.

[0034] In some preferred embodiments, Pt is selected as the active metal source, and the resulting target catalyst can be represented as Pt / M-Fe(OH). x In terms of molar amount, the total amount of transition metals and Pt in the target catalyst is 0.05 at.% to 1.5 at.% of the total amount of Fe element, and the molar ratio of transition metals to Pt is 1:1. The above ratio can be achieved by controlling the feeding ratio of Pt source, M source and Fe source.

[0035] The catalyst provided in this invention can actively utilize water vapor in hydrogen-rich reformed gas. The catalyst is Co / Ni-doped Fe(OH). x As a carrier of the active component, Co / Ni doping alters Fe(OH)₂. xThe electronic structure of the surface allows water molecules adsorbed on the catalyst to dissociate and generate surface-active hydroxyl groups. These active hydroxyl groups can directly participate in the oxidation of CO adsorbed on the catalytically active metal sites, thereby improving the catalytic oxidation conversion rate of CO. At the same time, the abundant active hydroxyl groups on the catalyst surface can inhibit the accumulation of carbonate species on the catalyst surface, reducing the poisoning effect of CO2 in the reformed gas on the catalyst, and allowing the catalyst to maintain stable operation for a long time. It should be noted that the catalyst provided in this embodiment of the invention utilizes the heat generated by the CO oxidation reaction to activate water vapor (self-heating effect). At a relatively low temperature (50~80℃), water molecules adsorbed on the catalyst can dissociate and generate surface-active hydroxyl groups, thereby positively promoting the catalytic reaction activity through the self-heating effect.

[0036] The catalyst provided in this invention is particularly suitable for removing CO from hydrogen-rich gas (e.g., 70 vol.% H2) containing water vapor (e.g., 10 vol.% H2O) and a certain amount of CO2 at low temperatures (50~80°C).

[0037] Furthermore, the catalyst provided in this embodiment of the invention utilizes non-noble metal M (Co / Ni) to assist in the dispersion and activation of noble metal components (Pt, Pd, Ru, Rh or Au), achieving excellent catalytic performance with extremely low noble metal loading (only about 0.025-0.75 at.% relative to Fe), and has good economic efficiency for industrial applications.

[0038] Based on the above embodiments, the present invention also proposes the following specific embodiments. It should be noted that the following specific embodiments are merely exemplary and are not intended to limit the scope of protection of the present invention in any way.

[0039] Example 1

[0040] In this embodiment, a co-precipitation-low-temperature reduction method was used to prepare Pt / Co-Fe(OH) with a total Co and Pt loading of approximately 1 at.% (relative to Fe) and a Pt to Co molar ratio of approximately 1:1. x The catalyst, and the specific steps are as follows: (1) Preparation of precursor solution: Weigh 4.04 g of ferric nitrate nonahydrate (Fe(NO3)3·9H2O, 0.01 mol) and dissolve it in 15 mL of deionized water to obtain ferric nitrate solution. Add 20 mL of chloroplatinic acid standard solution (H2PtCl6, Pt content 1.0 g / L) to the ferric nitrate solution, and then add 0.025 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) to the ferric nitrate solution. Mix the above solutions evenly and add deionized water as needed to adjust the volume to obtain mixed metal salt solution.

[0041] (2) Preparation of alkaline solution: Weigh 2g NaOH and dissolve it in 10mL of deionized water to prepare an alkaline precipitate solution with a concentration of about 5mol / L.

[0042] (3) Coprecipitation reaction: Place the mixed metal salt solution in a 50 mL borosilicate glass sample bottle and stir it with high speed magnetically under the heating condition of 80 °C water bath; then, slowly add alkaline precipitate to the mixed metal salt solution, strictly control the amount added (about 5.4~5.5 mL), until the solution forms a stable brownish-red precipitate and the pH value of the supernatant is stable at about 8.5.

[0043] (4) Aging and washing: Seal the sample bottle and continue to stir the mixed metal salt solution at 80°C for 3 hours. Then stop heating and stirring and let the solution stand to precipitate and age for 1 hour. After the supernatant and precipitate are clearly separated, wash the precipitate repeatedly with boiled deionized water to remove nitrate ions and chloride ions.

[0044] (5) Drying and grinding: The washed precipitate cake was placed in an oven and dried at 70°C for 8 hours. Then the dried precipitate was ground to obtain Pt / Co-Fe(OH). x Precursor powder.

[0045] (6) Reduction and activation: The dried precursor powder was placed in a tube furnace and reduced at 200~250℃. The reducing atmosphere was a mixture of H2 and N2 (25 vol.% H2), the gas flow rate was 40 mL / min, and the treatment time was 60 min. After reduction, the precursor powder was finally reduced to Pt / Co-Fe(OH). x catalyst.

[0046] Example 2

[0047] In this embodiment, a co-precipitation-low-temperature reduction method was used to prepare Pt / Ni-Fe(OH) with a total Ni and Pt loading of approximately 1 at.% (relative to Fe) and a Pt to Ni molar ratio of approximately 1:1. x The catalyst, and the specific steps are as follows: (1) Preparation of precursor solution: Weigh 4.04 g of ferric nitrate nonahydrate (Fe(NO3)3·9H2O, 0.01 mol) and dissolve it in 15 mL of deionized water to obtain ferric nitrate solution. Add 20 mL of chloroplatinic acid standard solution (H2PtCl6, Pt content 1.0 g / L) to the ferric nitrate solution, and then add 0.011 g of nickel chloride (NiCl2) to the ferric nitrate solution. Mix the above solutions evenly and add deionized water as needed to adjust the volume to obtain mixed metal salt solution.

[0048] (2) Preparation of alkaline solution: Weigh 2g NaOH and dissolve it in 10mL of deionized water to prepare an alkaline precipitate solution with a concentration of about 5mol / L.

[0049] (3) Coprecipitation reaction: Place the mixed metal salt solution in a 50 mL borosilicate glass sample bottle and stir it with high speed magnetically under the heating condition of 80 °C water bath; then, slowly add alkaline precipitate to the mixed metal salt solution, strictly control the amount added (about 5.4~5.5 mL), until the solution forms a stable brownish-red precipitate and the pH value of the supernatant is stable at about 8.5.

[0050] (4) Aging and washing: Seal the sample bottle and continue to stir the mixed metal salt solution at 80°C for 3 hours. Then stop heating and stirring and let the solution stand to precipitate and age for 1 hour. After the supernatant and precipitate are clearly separated, wash the precipitate repeatedly with boiled deionized water to remove nitrate ions and chloride ions.

[0051] (5) Drying and grinding: The washed precipitate cake was placed in an oven and dried at 70°C for 8 hours. Then the dried precipitate was ground to obtain Pt / Ni-Fe(OH). x Precursor powder.

[0052] (6) Reduction and activation: The dried precursor powder was placed in a tube furnace and reduced at 200~250℃. The reducing atmosphere was a mixture of H2 and N2 (25 vol.% H2), the gas flow rate was 40 mL / min, and the treatment time was 60 min. After reduction, the precursor powder was finally reduced to Pt / Ni-Fe(OH). x catalyst.

[0053] Example 3

[0054] To determine the optimal Pt-M doping amount, Pt / Co-Fe(OH) with different Pt-Co loadings were prepared in this embodiment. x The Pt-Co loadings of the samples were 0.05 at.%, 0.3 at.%, 0.5 at.%, and 1.5 at.%, respectively. The Pt-Co loading refers to the total mass of Pt and Co elements relative to the Fe content. All samples were prepared strictly according to the operating steps of Example 1.

[0055] Comparative Example 1

[0056] To verify the effect of the presence or absence of Pt on the catalytic performance of the catalyst, a control sample Co-Fe(OH) without Pt was prepared in this comparative example. x and Ni-Fe(OH) x .

[0057] Aside from the different raw material ratios in the precursor solution preparation step, Co-Fe(OH) x and Ni-Fe(OH) x The remaining preparation steps are the same as in Examples 1 and 2.

[0058] Among them, Co-Fe(OH) x Precursor solution: Weigh 4.04g of ferric nitrate nonahydrate and dissolve it in deionized water. Do not add chloroplatinic acid solution. Increase the amount of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) to 4 times that in Example 1, that is, weigh 0.1g of cobalt nitrate hexahydrate and add it to the mixed solution. Other steps are the same as those in Example 1.

[0059] Ni-Fe(OH) x Precursor solution: Weigh 4.04g of ferric nitrate nonahydrate and dissolve it in deionized water. Do not add chloroplatinic acid solution. Increase the amount of nickel chloride (NiCl2) to 4 times that in Example 2, that is, weigh 0.044g of nickel chloride and add it to the mixed solution. Other steps are the same as those in Example 2.

[0060] Comparative Example 2

[0061] To verify the necessity of M-doping of transition metals, M-free Pt / Fe(OH) was prepared. x Use samples for comparison.

[0062] Pt / Fe(OH) x Precursor solution: Weigh 4.04 g of ferric nitrate nonahydrate and dissolve it in deionized water. Add 20 mL of chloroplatinic acid standard solution (H2PtCl6, Pt content 1.0 g / L) to the ferric nitrate solution. Do not add a transition metal source. Other steps are consistent with the subsequent steps in Example 1.

[0063] Catalyst performance testing and analysis: The Pt / Co-Fe(OH) prepared in Example 1 x Catalyst and Pt / Ni-Fe(OH) prepared in Example 2 x 0.1 g (40-60 mesh) of catalyst was weighed out and mixed with 0.4 g of quartz sand particles (40-60 mesh) before being packed into a fixed-bed reactor to obtain Pt / Co-Fe(OH)2. x and Pt / Ni-Fe(OH) x Two catalyst experimental groups were set up; three reaction gas atmosphere conditions were set up: CO-PROX (H2O), CO-PROX (CO2), and CO-PROX (MSR).

[0064] The CO-PROX (H2O) reaction gas composition is 1 vol.% CO, 1 vol.% O2 and 70 vol.% H2, with N2 as the balance gas. The total flow rate is 100 mL / min. The mixed gas is bubbled and moistened in a 42℃ water bath before entering the fixed-bed reactor. Under the above atmospheric conditions, a stable reaction temperature of 60℃ is set for the selective oxidation of CO. The changes in components are detected by gas chromatography, and the CO conversion rate is calculated.

[0065] The CO-PROX (CO2) reaction gas composition is 1 vol.% CO, 1 vol.% O2, 20 vol.% CO2 and 70 vol.% H2, with N2 as the balance gas. The total flow rate is 100 mL / min, and the mixed gas is directly introduced into the fixed-bed reactor. A stable reaction temperature of 60 °C is set for the selective oxidation of CO. The changes in components are detected by gas chromatography, and the CO conversion rate is calculated.

[0066] The CO-PROX (MSR) reaction gas composition is 1 vol.% CO, 1 vol.% O2, 20 vol.% CO2 and 70 vol.% H2, with N2 as the balance gas. The total flow rate is 100 mL / min. The mixed gas is bubbled and humidified in a 42℃ constant temperature water bath before entering the fixed bed reactor. A stable reaction temperature of 60℃ is set for the selective oxidation of CO. The changes in components are detected by gas chromatography, and the CO conversion rate is calculated.

[0067] like Figure 2 As shown, under CO-PROX (H2O) atmosphere conditions, Pt / Co-Fe(OH) x and Pt / Ni-Fe(OH) x The catalysts can efficiently remove CO, and the CO conversion rate can remain stable at around 85% during a reaction time of up to 30 hours, without any trend of activity decay.

[0068] See Figure 3 Under CO-PROX (MSR) atmosphere conditions, Pt / Co-Fe(OH) x and Pt / Ni-Fe(OH) x The catalyst was able to maintain a high CO conversion rate for the first 8 hours, but then its activity gradually decreased. This may be due to the continuous accumulation of carbonate species generated by the long-term reaction of CO2 and H2O at low temperature (60℃).

[0069] Furthermore, by adjusting the order in which H2, CO2, and H2O are introduced, the volume percentages of CO and O2 in the CO-PROX reaction gas system remain unchanged, except for H2, CO2, and H2O.

[0070] Test results reference Figure 4 , Figure 4 Figure a shows the reaction gas containing only CO (excluding H2, H2O, and CO2). It can be seen that in the CO oxidation reaction, Pt / Co-Fe(OH) x and Pt / Ni-Fe(OH) x Neither can effectively maintain catalytic activity; Figure 4 Figures b and c show the process of first introducing CO reaction gas containing H2O (the CO reaction gas is bubbled and moistened in a 42°C water bath before entering the fixed-bed reactor), then introducing H2 (70 vol.%), and finally introducing CO2 (20 vol.%). Figure b represents the Pt / Co-Fe(OH) reactor. x Catalytic reactions of catalysts; diagram c represents Pt / Ni-Fe(OH) x The catalytic reaction was conducted at a constant temperature of 60℃. It was observed that the CO conversion rate increased directly to nearly 100% after the introduction of H2O. Subsequent introduction of H2 resulted in a slight decrease in catalytic performance, while the introduction of CO2 showed no significant activity fluctuation. This indicates that the H2O effect was a net activity boost; the introduction of a high proportion of H2 led to competitive oxidation, resulting in a partial loss of catalytic activity, while CO2 had almost no impact on the Pt / Co-Fe(OH) reaction. x and Pt / Ni-Fe(OH) x Its catalytic performance.

[0071] Figure 4 Diagrams d and e in the diagram indicate that a CO reaction gas containing H2 (70 vol.%) is first introduced, followed by CO2, and finally H2O (the CO reaction gas is bubbled and moistened in a 42°C water bath before entering the fixed-bed reactor). Diagram d represents the Pt / Co-Fe(OH) reaction. x Catalytic reactions of catalysts, the e-diagram represents Pt / Ni-Fe(OH) x The catalytic reaction was consistently conducted at 60℃. It was observed that a high proportion of H2 also promoted CO oxidation, but less effectively than H2O. Introducing CO2 at this point resulted in a significant decrease in activity. Introducing H2O restored some activity, but the effect was minimal. This indicates that both H2O and H2 promote CO oxidation. If CO2 is present in the CO-PROX system before H2O, CO2 preferentially occupies the adsorption activation sites of H2O, and the subsequent introduction of H2O cannot completely restore the Pt / M-Fe(OH) ratio. x The activity of H2 and H2O can both be achieved in Pt / M-Fe(OH)2. x The surface is converted into active -OH to participate in the indirect oxidation of CO, but H2O has a better promoting effect.

[0072] The control samples Co-Fe(OH) prepared in Comparative Examples 1 and 2 xNi-Fe(OH) x Pt / Fe(OH) x Catalytic activity was evaluated using the aforementioned catalyst performance testing method, with the reaction gas being a CO-PROX (H2O) system.

[0073] Test results are as follows Figure 5 As shown, Co-Fe(OH) x and Ni-Fe(OH) x Pt / Fe(OH) has almost no activity. x The low activity of Pt / Co-Fe(OH)2, which decreases with reaction time, fully demonstrates the characteristics of the Pt / Co-Fe(OH)2 reaction. x and Pt / Ni-Fe(OH) x The Pt-M-Fe (M is Ni or Co) exhibits a synergistic effect, jointly achieving low-temperature and efficient removal of CO from hydrogen-rich water vapor.

[0074] The Pt / Co-Fe(OH) prepared in Example 3 with different Pt-Co loadings were compared. x The samples were evaluated for catalytic activity using the aforementioned catalyst performance testing method. The Pt-Co loadings were 0.05 at.%, 0.3 at.%, 0.5 at.%, and 1.5 at.%, respectively, and the reaction gas was a CO-PROX (H2O) system.

[0075] Test results are as follows Figure 6 As shown, the activity test results for different Pt-Co loadings indicate that both high and low Pt-Co loadings limit the catalyst activity. Only a suitable Pt-Co loading can achieve high CO catalytic oxidation performance. Among these samples, a Pt / Co-Fe(OH) loading of 0.5 at.% is suitable. x The sample exhibits optimal catalytic activity.

[0076] As can be seen from the above embodiments and catalytic activity test results, the catalyst provided by the embodiments of the present invention has excellent CO catalytic activity under low temperature water vapor conditions. Through the synergistic effect of Pt, M and Fe, the Pt sites supported on the support are uniformly dispersed, and H2O can be efficiently activated to induce the generation of surface hydroxyl species to participate in the CO redox cycle. It can also effectively inhibit the poisoning effect of CO2, and is particularly suitable for deep CO removal under CO-PROX conditions.

[0077] It is understood that other active metal components with similar catalytic properties to Pt, such as Pd, Ru, Rh, or Au, are also applicable to the technical solution of this invention, such as Co / Ni-doped Fe(OH). x All carriers used as active metal components can achieve the same performance as the Pt / Co-Fe(OH) provided in the embodiments of this invention. xCatalysts and Pt / Ni-Fe(OH) x Similar technical effects to catalysts.

[0078] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A transition metal-modified CO selective oxidation catalyst, characterized in that, include: carrier; Active components loaded on the carrier; The support is Fe(OH) doped with a transition metal. x The transition metal is Co and / or Ni, and the active component is an active metal with CO catalytic oxidation activity.

2. The transition metal-modified CO selective oxidation catalyst according to claim 1, characterized in that, The active metal is Pt; by molar amount, the total amount of the transition metal and Pt is 0.05 at.% to 1.5 at.% of the total amount of Fe, and the molar ratio of the transition metal to Pt is 1:

1.

3. A method for preparing a transition metal-modified CO selective oxidation catalyst, characterized in that, Including the following steps: S1, dissolve Fe source, transition metal source and active metal source in deionized water to obtain a mixed metal salt solution; the transition metal source is Co source and / or Ni source, and the active metal source can be decomposed to obtain an active metal with CO catalytic oxidation activity; S2, add an alkaline precipitate to the mixed metal salt solution, adjust the mixed metal salt solution to a preset pH value, and obtain a suspension precipitate; S3, the suspension precipitate is heated and stirred to react, the suspension precipitate after reaction is allowed to stand and age, the suspension precipitate after standing and aging is separated into solid and liquid to obtain precipitate, the precipitate is washed and dried to obtain catalyst precursor. S4. The catalyst precursor is subjected to reduction heat treatment under a reducing atmosphere to obtain the target catalyst.

4. The method for preparing the transition metal-modified CO selective oxidation catalyst according to claim 3, characterized in that, The Fe source is at least one of ferric nitrate, ferric sulfate, and ferric chloride; The Co source is at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt chloride; The Ni source is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride.

5. The method for preparing the transition metal-modified CO selective oxidation catalyst according to claim 3, characterized in that, The active metal source is a Pt source, and the Pt source is at least one of chloroplatinic acid, platinum nitrate, platinum sulfate, and platinum acetylacetonate. In terms of molar amount, the total amount of transition metal and Pt in the target catalyst is 0.05 at.% to 1.5 at.% of the total amount of Fe element, and the molar ratio of the transition metal to Pt is 1:

1.

6. The method for preparing the transition metal-modified CO selective oxidation catalyst according to claim 3, characterized in that, The ratio of the mass of Fe source to the volume of deionized water in the mixed metal salt solution is (2~5) g : (15~30) mL.

7. The method for preparing the transition metal-modified CO selective oxidation catalyst according to claim 3, characterized in that, The alkaline precipitate is a 1-5 mol / L NaOH solution, and the preset pH value is 8-9.

8. The method for preparing the transition metal-modified CO selective oxidation catalyst according to claim 3, characterized in that, In step S3, the heating and stirring temperature is 60~85℃, the reaction time is 3~4h, the aging time is 1~3h, the drying temperature is 60~85℃, and the drying time is 18~24h.

9. The method for preparing the transition metal-modified CO selective oxidation catalyst according to claim 3, characterized in that, The reducing atmosphere is a mixture of H2 and a protective gas, wherein the protective gas is N2, Ar, or He; The H2 volume percentage in the reducing atmosphere is 10~25 vol.%, the gas flow rate of the mixed gas is 30~60 mL / min, the temperature of the reduction heat treatment is 200~250℃, and the treatment time is 30~60 min.

10. The application of a catalyst in the removal of CO from hydrogen-rich gas, characterized in that, The catalyst is the transition metal modified CO selective oxidation catalyst according to claim 1 or 2, or the transition metal modified CO selective oxidation catalyst prepared by any one of the preparation methods of claims 3-9; The hydrogen-rich gas contains a predetermined volume percentage of hydrogen and water vapor.

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