A noble metal catalyst for selective catalytic oxidation and dehydrogenation of crude helium

Abstract

The application discloses a noble metal catalyst for selective catalytic oxidative dehydrogenation of crude helium, which comprises an active component, a carrier, an auxiliary agent and a selective regulator; the active component is selected from one or two of Pt, Pd and Ru; the carrier is alumina pellets prepared with the aid of ammonium alginate; the auxiliary agent is any one or more of Ce, La, Y, Zr, Mg and Sr; and the selective regulator is selected from one or more of Ni, Mn, Co, Mo, W and Nb. The catalyst can be applied to a catalytic oxidative dehydrogenation unit for helium extraction from natural gas, realizes selective oxidation of hydrogen, and solves the problem that the existing catalyst simultaneously catalytically oxidizes methane in crude helium into CO2. Through modification of the catalyst, adsorption of methane is inhibited, CO2 generation is greatly reduced, and the load of a subsequent separation and purification unit is reduced. The catalyst has good low-temperature activity, low CO2 selectivity, and the volume fraction of H2 in outlet gas after dehydrogenation is lower than 0.1 ppm, and the volume fraction of CO2 is lower than 30 ppm.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically a crude helium refining selective catalytic oxidation dehydrogenation noble metal catalyst. Background Technology

[0002] Helium is a rare strategic resource that plays a vital role in high-tech fields such as nuclear industry, aerospace, petrochemicals, semiconductors, fiber optics, and deep-sea diving. Helium is mainly found in air, some natural gas, and geothermal dissolved gases, with helium-containing natural gas being the primary source for helium extraction.

[0003] Currently, large-scale helium extraction mainly relies on cryogenic processes. After cryogenic treatment, natural gas yields crude helium with a purity of 60-70%. Hydrogen in this crude helium is difficult to separate due to high condensation costs and its similar physical properties to helium; therefore, catalytic oxidation is commonly used to remove it. The hydrogen fraction in crude helium is generally higher than 4%. To control the exothermic reaction and ensure system safety, multi-stage oxygenation or dilution of the feed gas is typically employed, with the reaction temperature generally controlled below 180°C. The volume fraction of methane in crude helium is approximately 20-40%. Although the complete oxidation temperature of methane in the presence of a catalyst generally exceeds 400°C, trace amounts of methane are still oxidized to CO2 at temperatures below 180°C. Depending on the reaction temperature, space velocity, and H2 concentration in the feed gas, the CO2 volume fraction in the tail gas varies from 10 ppm to 500 ppm. If the CO2 concentration in the tail gas is high, subsequent helium refining requires adding a decarbonization unit or increasing the load on existing purification units.

[0004] Catalytic oxidative dehydrogenation catalysts typically employ noble metal catalysts with platinum and palladium as active components. CN116099545A discloses a dehydrogenation catalyst for high-concentration carbon dioxide gas, using Pd and Pt as active components and Cu, Mo, and rare earth elements as promoters, which can reduce the noble metal loading to a mass fraction of 0.08-0.3%, significantly reducing costs. CN101711987A discloses a catalyst for dehydrogenation under trace hydrogen conditions, using Pd as the active component, alumina as the catalyst, and Ni, Fe, Ba, Ce, La, Sm, and Pr as promoters. The noble metals are dispersed in alcohol-based organic solvents, achieving high dispersion, high activity, high low-temperature activity, and good resistance to poisoning and moisture. CN1249964A discloses a carbon dioxide-rich atmosphere-based hydrogen removal catalyst for urea synthesis. It uses an Al2O3-TiO2 or Al2O3-ZrO composite support to support Pd and Pt bimetals, rare earth elements as auxiliary agents, and wet reduction with hydrazine at room temperature instead of high-temperature reduction. The catalyst exhibits good low-temperature activity, a wide reaction temperature range, and good resistance to toxicity.

[0005] However, existing precious metal dehydrogenation catalysts mainly exhibit good catalytic activity for both hydrogen and hydrocarbon compounds. Trace amounts of methane can be catalytically oxidized to CO2 at around 180°C. There are few literature reports on dehydrogenation catalysts that inhibit the catalytic oxidation of methane under crude helium refining conditions. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the current technology by providing a noble metal catalyst for selective catalytic oxidation dehydrogenation of crude helium. This catalyst can solve the problem of catalyzing the oxidation of trace amounts of methane to CO2 during the use of existing catalysts, reduce the conversion rate of methane in the catalytic oxidation dehydrogenation unit, reduce CO2 production, and reduce the load on the subsequent crude helium refining unit.

[0007] Another objective of this invention is to provide a method for preparing the catalyst described above.

[0008] A third objective of this invention is to provide the application of the catalyst described above.

[0009] To achieve the above-mentioned objectives, the specific technical solution of this invention is as follows:

[0010] A selective catalytic oxidation dehydrogenation noble metal catalyst for crude helium refining, the catalyst comprising an active component, a support, an auxiliary agent, and a selectivity modifier;

[0011] The active component is selected from any one or two of Pt, Pd, and Ru, and the mass content of the active component, calculated as metal, is greater than 0 and less than or equal to 0.15 wt% (specifically, it can be 0.02 wt%, 0.04 wt%, 0.06 wt%, 0.08 wt%, 0.10 wt%, 0.12 wt%, 0.14 wt%, 0.15 wt%, etc.).

[0012] The carrier is alumina microspheres doped with fly ash and additives, prepared with the assistance of ammonium alginate. The additive elements are any one or more of Ce, La, Y, Zr, Mg, and Sr. The content of the carrier is 89.85-99 wt% (specifically, it can be 89.95 wt%, 90.00 wt%, 91.00 wt%, 92.00 wt%, 93.00 wt%, 94.00 wt%, 95.00 wt%, 96.00 wt%, 97.00 wt%, 98.00 wt%, 99.00 wt%, etc.).

[0013] The selectivity modifier is selected from any one or more of Ni, Mn, Co, Mo, W, and Nb, and the content of the selectivity modifier is 1 to 10 wt% based on the mass of the oxide (specifically, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.).

[0014] The total composition of the catalyst is 100%.

[0015] Furthermore, the preparation method of the crude helium refined selective catalytic oxidation dehydrogenation noble metal catalyst described above includes the following steps:

[0016] Step 1. Dissolve any one or more of cerium nitrate, lanthanum nitrate, yttrium nitrate, zirconium nitrate, zirconium oxychloride, magnesium nitrate, and strontium nitrate to prepare a mixed solution. Add a precipitating agent to carry out a precipitation reaction, controlling the pH at 7.0–9.5 (specifically 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, etc.). After aging, filtering, washing, drying, and calcining, the precipitate is obtained as powder A.

[0017] Step 2. Mix boehmite, powder A, and fly ash in a certain proportion, and add them to an excess of ammonium alginate aqueous solution. After homogenization and stirring, add the mixture dropwise to a mixed salt solution of Ba(NO3)2 and Zn(NO3)2. After treatment with glacial acetic acid for 4-8 hours, filter, wash, and dry at 80-120℃ (specifically 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, etc.) for 4-8 hours (specifically 4h, 5h, 6h, 7h, 8h, etc.). Then calcine at 400-600℃ (specifically 400℃, 450℃, 500℃, 550℃, 600℃, etc.) to obtain small balls B.

[0018] Step 3. Prepare a solution of the precursor of the selective regulator, add a pH adjuster to adjust the pH to a certain range, and impregnate an equal volume of the solution onto microspheres B. After impregnation at 10–60°C (specifically 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc.) for 2–4 hours (specifically 2h, 2.5h, 3h, 3.5h, 4h, etc.), dry at 80–120°C for 4–8 hours to obtain microspheres C.

[0019] Step 4. Prepare a solution of the precursor of the active component, add a pH adjuster to adjust the pH to a certain range, and impregnate it onto the spheres C in equal volume. After impregnation at 10-60℃ (specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, etc.) for 2-4 hours (specifically 2h, 2.5h, 3h, 3.5h, 4h, etc.), dry and calcine to obtain the noble metal spherical catalyst D.

[0020] Furthermore, the precursor of the active component is platinum nitrate, chloroplatinic acid, palladium nitrate, chloropalladium acid, ruthenium nitrate, or ruthenium trichloride; the precursor of the selectivity regulator is nickel nitrate, manganese nitrate, cobalt nitrate, cobalt acetate, ammonium molybdate, ammonium metatungstate, or ammonium niobate.

[0021] Further, in step 1, the molar concentration of the mixed solution is 0.01–1.0 mol / L (specifically, it can be 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc.); the precipitant is any one of ammonia, Na₂CO₃, and ammonium carbonate, and the precipitant solution… The concentration is 0.01–1.0 mol / L (specifically, it can be 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc.); the precipitation and aging temperature is 10–80℃ (specifically, it can be 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, etc.). The aging temperatures are 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, etc., and the aging time is 2 to 24 hours (specifically 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc.). The drying conditions are 80 to 120℃ (specifically 80℃, 85℃, 90℃, 95℃, 100℃, 10...). Dry at 5℃, 110℃, 115℃, 120℃, etc. for 8 to 12 hours (specifically 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, etc.), and calcinate at 300 to 600℃ (specifically 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, etc.) for 4 to 8 hours (specifically 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, etc.).

[0022] Further, in step 2, the mass fraction of the ammonium alginate aqueous solution is 0.2-0.8% (specifically, it can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, etc.), and the concentrations of the Ba(NO3)2 and Zn(NO3)2 salt solutions are 0.1-1.0 mol / L (specifically, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc.) and 0.3-3.0 mol / L (specifically, it can be 0.3 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, etc.).

[0023] Further, in step 2, the mass ratio of the pseudoboehmite to powder A is 4 to 9 (specifically, it can be 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, etc.), and more preferably 6 to 8; the mass ratio of the pseudoboehmite to fly ash is 20 to 40, and more preferably 25 to 35.

[0024] Further, in step 3, the pH adjuster is one or more of nitric acid, hydrochloric acid, phosphoric acid, glacial acetic acid, citric acid, tartaric acid, potassium citrate, potassium bicarbonate, and ammonia, controlling the pH range during the impregnation process to be 1.0 to 6.0 (specifically 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, etc.), and more preferably 3.0 to 5.0.

[0025] Further, in step 4, the pH adjuster is one or more of nitric acid, hydrochloric acid, phosphoric acid, glacial acetic acid, citric acid, tartaric acid, potassium citrate, potassium bicarbonate, and ammonia, controlling the pH range during the impregnation process to be 0.5 to 3.5 (specifically, it can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, etc.), and more preferably 0.5 to 2.0.

[0026] The application of the noble metal catalytic oxidative dehydrogenation catalyst described in this invention is in a catalytic oxidative dehydrogenation unit for helium extraction from natural gas or BOG. ​​Crude helium gas is mixed with air, diluted, and then fed into the dehydrogenation reactor. Hydrogen and oxygen in the crude helium gas react under catalytic action to produce water. The volume fraction of H2 in the reactant gas is 0.5–3.0%, and the volume hourly space velocity (HSV) is 1000–5000 h⁻¹. -1 The reaction temperature is 10–200℃, and the bed pressure is 0.1–0.5 MPa. The volume fraction of H2 in the outlet gas is less than 0.1 ppm, and the volume fraction of CO2 is less than 30 ppm.

[0027] Furthermore, the catalyst reduction process is as follows: the catalyst is reduced in a fixed-bed reactor for 2–4 hours at a reduction temperature of 50–100°C and a space velocity of 500–5000 h⁻¹. -1 The pressure is 0-0.5 MPa, and the reducing gas composition is 5-20% H2, with the remainder being N2, or crude helium feedstock gas can be used for direct reduction.

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

[0029] This invention is scientifically designed and simple in method. Alumina microspheres doped with fly ash and additive elements, prepared by ammonium alginate spheronization, serve as a carrier. With the assistance of an acid-base regulator, a selectivity modifier and noble metal active components are loaded onto the carrier. Compared to conventional impregnation-forming methods, the ammonium alginate doping spheronization method can form a hierarchical porous structure, accelerating the reaction rate and allowing barium oxide and zinc oxide to be more uniformly loaded within the spheres. Furthermore, the addition of fly ash increases the carrier strength while simultaneously improving activity and the selectivity of the hydrogen oxidation reaction. The uniformly distributed barium oxide and zinc oxide interact with the additives in the carrier, enhancing the catalyst's oxygen storage capacity, increasing oxygen vacancies, and enhancing the catalyst's catalytic oxidation ability. Acid-base adjustment controls the dispersion and impregnation depth of the active components and the selectivity modifier. The addition of the selectivity modifier alters the CH activation sites on the catalyst surface, reducing methane adsorption and resulting in high H2 catalytic activity and extremely low CO2 selectivity. This means that while maintaining high H2 catalytic oxidation activity, the catalytic combustion of methane to produce CO2 is suppressed, resulting in a CO2 volume fraction in the outlet gas of less than 30 ppm. Simultaneously, the amount of precious metal active components used is reduced, lowering the catalyst production cost, while the catalyst exhibits high stability. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0031] Example 1

[0032] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0033] Step 1: Weigh 24.68g of cerium nitrate, 25.58g of zirconium oxychloride, 31.12g of magnesium nitrate, and deionized water to prepare a 5000mL mixed solution; prepare a 0.05mol / L sodium carbonate solution as a precipitant, and carry out a precipitation reaction between the precipitant and the mixed solution. Control the precipitation temperature at 40℃ and the pH of the precipitate at 7.0. Then age the precipitate for 2 hours, filter and wash it, and dry the resulting filter cake at 100℃ for 12 hours and calcine it at 450℃ for 3 hours to obtain powder A.

[0034] Step 2: Prepare 1000 mL of 0.5 wt% ammonium alginate aqueous solution; mix 105.26 g of boehmite, powder A obtained in step 1, and 2.63 g of fly ash evenly, then add them to the prepared ammonium alginate aqueous solution, stir homogenously, and then dropwise into 300 mL of a mixed salt solution (solvent is water) containing 0.2 mol / L Ba(NO3)2 and 0.4 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 4 h, filter, wash, dry at 120 °C for 8 h, and calcine at 500 °C for 4 h to obtain small balls B.

[0035] Step 3: Weigh 10.90g of nickel nitrate and 14.74g of cobalt nitrate to prepare a mixed solution, add glacial acetic acid to adjust the pH to 3.0, and impregnate an equal volume of the solution onto the microsphere B. Impregnate at 30℃ for 4 hours and dry at 120℃ for 6 hours to obtain microsphere C.

[0036] Step 4: Prepare a 5 mg / mL palladium chloride solution, take 14 mL, add hydrochloric acid, adjust the pH to 0.5, and impregnate an equal volume onto the small spheres C. Impregnate at 10°C for 3 h, dry and calcine to obtain the noble metal spherical catalyst D001.

[0037] Example 2

[0038] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0039] Step 1: Weigh 3.63g cerium nitrate, 21.03g lanthanum nitrate, and 10.28g strontium nitrate, add deionized water to prepare a 2100mL mixed solution; prepare a 0.05mol / L ammonia solution as a precipitant, and carry out a precipitation reaction between the precipitant and the mixed solution. Control the precipitation temperature at 50℃ and the pH at 8.0, age for 3h, filter and wash, and dry the filter cake at 110℃ for 8h and calcine at 550℃ for 4h to obtain powder A.

[0040] Step 2: Prepare 800 mL of 0.8 wt% ammonium alginate aqueous solution. Mix 121.21 g of boehmite, powder A obtained in Step 1, and 4.04 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, dropwise add the mixture to 200 mL of a mixed salt solution (solvent: water) containing 0.5 mol / L Ba(NO3)2 and 1.0 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 8 h, filter, wash, dry at 80 °C for 4 h, and calcine at 500 °C for 4 h to obtain small spheres B.

[0041] Step 3: Weigh 3.00g of cobalt acetate and 15.57g of nickel nitrate to prepare a mixed solution, add nitric acid to adjust the pH to 2.0, and impregnate an equal volume of the solution onto the microsphere B. Impregnate at 30℃ for 4 hours and dry at 120℃ for 8 hours to obtain microsphere C.

[0042] Step 4: Measure 8 mL of 5 mg / mL chloroplatinic acid solution, add hydrochloric acid, adjust the pH to 1.0, and impregnate an equal volume onto the small spheres C. Impregnate at 30°C for 3 hours, dry, and calcine to obtain the noble metal spherical catalyst D002.

[0043] Example 3

[0044] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0045] Step 1: Weigh 16.75g cerium nitrate, 15.77g yttrium nitrate, and 4.07g strontium nitrate, add deionized water, and prepare a 500mL mixed solution; prepare a 0.2mol / L sodium carbonate solution as a precipitant, and carry out a precipitation reaction between the precipitant and the mixed solution, controlling the precipitation temperature at 70℃ and the pH at 9.0, aging for 2h, filtering and washing, and drying the filter cake at 120℃ for 10h, and calcining at 450℃ for 8h to obtain powder A.

[0046] Step 2: Prepare 700 mL of 0.2 wt% ammonium alginate aqueous solution. Mix 123.29 g of boehmite, powder A obtained in Step 1, and 3.08 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, add the mixture dropwise to 400 mL of a mixed salt solution (solvent: water) containing 0.3 mol / L Ba(NO3)2 and 0.9 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 5 h, filter, wash, dry at 100 °C for 7 h, and calcine at 400 °C for 4 h to obtain small spheres B.

[0047] Step 3: Weigh 8.16g of 50% manganese nitrate solution and 1.28g of ammonium metatungstate to prepare a mixed solution, add tartaric acid to adjust the pH to 1.8, and impregnate an equal volume of the solution onto the small ball B. Impregnate at 60℃ for 4 hours and dry at 120℃ for 5 hours to obtain small ball C.

[0048] Step 4: Measure 4.3 mL of 5 mg / mL platinum nitrate solution and 7.6 mL of 5 mg / mL ruthenium nitrate solution, mix the two solutions, add nitric acid, adjust the pH to 0.8, and impregnate the small balls C with an equal volume. Impregnate at 20°C for 2 hours, dry and calcine to obtain the noble metal spherical catalyst D003.

[0049] Example 4

[0050] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0051] Step 1: Weigh 11.64g of cerium nitrate, 26.98g of lanthanum nitrate, and 12.86g of zirconium nitrate, add deionized water to prepare a 1200mL mixed solution, prepare a 0.1mol / L ammonia solution as a precipitant, and carry out a precipitation reaction between the precipitant and the mixed solution. Control the precipitation temperature at 30℃ and the pH at 8.0, age for 4h, filter and wash, and dry the filter cake at 120℃ for 12h and calcine at 400℃ for 5h to obtain powder A.

[0052] Step 2: Prepare 800 mL of 0.8 wt% ammonium alginate aqueous solution. Mix 115.38 g of pseudoboehmite, the obtained powder A, and 5.77 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, dropwise add the mixture to 350 mL of a mixed salt solution (solvent: water) containing 0.2 mol / L Ba(NO3)2 and 0.4 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 6 h, filter, wash, dry at 90 °C for 6 h, and calcine at 300 °C for 4 h to obtain small balls B.

[0053] Step 3: Weigh 5.29g of nickel nitrate and 6.02g of manganese nitrate solution, prepare a mixed solution, add citric acid, adjust the pH to 3.0, and impregnate an equal volume of the solution onto the small ball B. Impregnate at 20℃ for 3 hours and dry at 90℃ for 6 hours to obtain small ball C.

[0054] Step 4: Measure 8 mL of 5 mg / mL palladium nitrate solution, add tartaric acid, adjust the pH to 1.8, and impregnate an equal volume onto the small spheres C. Impregnate at 60°C for 3 hours, dry, and calcine to obtain the noble metal spherical catalyst D004.

[0055] Example 5

[0056] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0057] Step 1: Weigh 6.82g of yttrium nitrate and 72.51g of magnesium nitrate, add deionized water to prepare a 1000mL mixed solution, prepare a 0.3mol / L ammonium carbonate solution as a precipitant, mix the mixed solution and the precipitant to carry out the precipitation reaction, control the precipitation temperature at 70℃, control the pH at 8.5, age for 12h, filter and wash, and dry the filter cake at 110℃ for 10h, and calcine at 600℃ for 6h to obtain powder A.

[0058] Step 2: Prepare 600 mL of 0.3 wt% ammonium alginate aqueous solution. Mix 123.29 g of boehmite, powder A obtained in Step 1, and 4.11 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, add the mixture dropwise to 400 mL of a mixed salt solution (solvent: water) containing 1.0 mol / L Ba(NO3)2 and 2.0 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 5 h, filter, wash, dry at 120 °C for 5 h, dry at 60 °C, and calcine at 500 °C for 3 h to obtain small spheres B.

[0059] Step 3: Weigh 2.11g cobalt nitrate, 1.23g ammonium molybdate, and 0.43g ammonium metatungstate, add deionized water to prepare a mixed solution, add glacial acetic acid and ammonia water, adjust the pH to 5.0, and immerse an equal volume of the solution on small ball B. Immerse at 50℃ for 2 hours and dry at 80℃ for 8 hours to obtain small ball C.

[0060] Step 4: Measure 8 mL of 5 mg / mL palladium nitrate solution and 16 mL of 5 mg / mL platinum nitrate solution, mix the two solutions, add nitric acid and tartaric acid, adjust the pH to 0.5, and impregnate the small balls C with an equal volume. Impregnate at 40℃ for 2 h, dry and calcine to obtain the noble metal spherical catalyst D005.

[0061] Example 6

[0062] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0063] Step 1: Weigh 33.35g zirconium oxychloride and 26.05g strontium nitrate, add deionized water to prepare a 450mL mixed solution, prepare a 1.0mol / L sodium carbonate solution as a precipitant, carry out the precipitation reaction, control the precipitation temperature at 60℃, control the pH at 8.0, age for 20h, filter and wash, and dry the filter cake at 100℃ for 12h, and calcine at 450℃ for 4h to obtain powder A.

[0064] Step 2: Prepare 1200 mL of 0.6 wt% ammonium alginate aqueous solution. Mix 105.26 g of boehmite, powder A obtained in Step 1, and 4.21 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, dropwise add the mixture to 200 mL of a mixed salt solution (solvent: water) containing 0.1 mol / L Ba(NO3)2 and 0.4 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 8 h, filter, wash, dry at 110 °C for 8 h, dry at 100 °C, and calcine at 400 °C for 4 h to obtain small spheres B.

[0065] Step 3: Weigh 9.52g of 50% manganese nitrate solution, 0.96g of ammonium metatungstate and deionized water to prepare a mixed solution, add potassium citrate to adjust the pH to 5.5, and immerse an equal volume of the solution on the small ball B. Immerse at 10℃ for 3 hours and dry at 120℃ for 4 hours to obtain small ball C.

[0066] Step 4: Measure 8 mL of 5 mg / mL chloroplatinic acid solution and 8 mL of 5 mg / mL chloropalladic acid solution, mix the two solutions, add ammonia and citric acid, adjust the pH to 2.0, and impregnate the small balls C with an equal volume. Impregnate at 50℃ for 4 hours, dry and calcine to obtain the noble metal spherical catalyst D006.

[0067] Example 7

[0068] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0069] Step 1: Weigh 39.42g of lanthanum nitrate, 12.93g of zirconium oxychloride, and 31.45g of magnesium nitrate, add deionized water to prepare a 400mL mixed solution, and prepare a 1.0mol / L sodium carbonate solution as a precipitant. The precipitant and the mixed solution are subjected to a precipitation reaction, with the precipitation temperature controlled at 70℃ and the pH at 9.5. The mixture is aged for 15 hours, filtered, washed, and the resulting filter cake is dried at 120℃ for 8 hours and calcined at 550℃ for 6 hours to obtain powder A.

[0070] Step 2: Prepare 900 mL of 0.4 wt% ammonium alginate aqueous solution. Mix 115.38 g of boehmite, powder A obtained in Step 1, and 3.30 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, dropwise add the mixture to 500 mL of a mixed salt solution (solvent: water) containing 0.8 mol / L Ba(NO3)2 and 1.2 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 7 h, filter, wash, dry at 120 °C for 6 h, and calcine at 400 °C for 2 h to obtain small spheres B.

[0071] Step 3: Weigh 4.67g of nickel nitrate and 16.85g of cobalt nitrate, add deionized water to prepare a mixed solution, add potassium citrate to adjust the pH to 4.0, and immerse an equal volume of the solution on the small ball B. Immerse at 10℃ for 4 hours and dry at 120℃ for 6 hours to obtain small ball C.

[0072] Step 4: Measure 16 mL of 5 mg / mL chloroplatinic acid solution, add phosphoric acid, adjust the pH to 1.5, and impregnate an equal volume onto the small spheres C. Impregnate at 30°C for 3 hours, dry, and calcine to obtain the noble metal spherical catalyst D007.

[0073] Example 8

[0074] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0075] Step 1: Weigh 20.29g cerium nitrate, 16.64g zirconium nitrate, and 20.26g magnesium nitrate, add deionized water to prepare a 500mL mixed solution, prepare a 0.5mol / L ammonia solution as a precipitant, and carry out the precipitation reaction together with the precipitant and the mixed solution. Control the precipitation temperature at 40℃ and the pH at 8.0, age for 8h, filter and wash, and dry the filter cake at 110℃ for 10h and calcine at 500℃ for 5h to obtain powder A.

[0076] Step 2: Prepare 1000 mL of 0.4 wt% ammonium alginate aqueous solution. Mix 118.64 g of boehmite, powder A obtained in Step 1, and 3.39 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, dropwise add the mixture to 300 mL of a mixed salt solution (solvent: deionized water) containing 0.5 mol / L Ba(NO3)2 and 0.8 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 8 h, filter, wash, dry at 120 °C for 8 h, and calcine at 600 °C for 2 h to obtain small spheres B.

[0077] Step 3: Weigh 10.51g of nickel nitrate, 6.31g of cobalt acetate, 1.47g of ammonium molybdate and deionized water to prepare a mixed solution, add ammonia water, adjust the pH to 5.0, and immerse an equal volume of the solution on the small ball B. Immerse at 50℃ for 3 hours and dry at 100℃ for 6 hours to obtain the small ball C.

[0078] Step 4: Measure 8 mL of 5 mg / mL platinum nitrate solution and 2 mL of 5 mg / mL palladium nitrate solution, mix the two solutions, add phosphoric acid, adjust the pH to 1.5, and impregnate the small balls C with an equal volume. Impregnate at 40℃ for 3 h, dry and calcine to obtain the noble metal spherical catalyst D008.

[0079] Example 9

[0080] This example is Comparative Example 1. Compared with Example 8, no additives are added during the carrier preparation process in this example, and the carrier only contains Al2O3. Specifically:

[0081] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0082] Step 1: Prepare 1000 mL of 0.4 wt% ammonium alginate aqueous solution. Mix 118.64 g of boehmite with 3.39 g of fly ash and add it to the prepared ammonium alginate aqueous solution. After homogenization and stirring, add it dropwise to 300 mL of a mixed salt solution (solvent is deionized water) containing 0.5 mol / L Ba(NO3)2 and 0.8 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 8 h, filter, wash, dry at 120 °C for 8 h, and calcine at 600 °C for 2 h to obtain small ball B.

[0083] Step 2: Weigh 10.51g of nickel nitrate, 6.31g of cobalt acetate, 1.47g of ammonium molybdate and deionized water to prepare a mixed solution, add ammonia water, adjust the pH to 5.0, and immerse an equal volume of the solution on small ball B. Immerse at 50℃ for 3 hours and dry at 100℃ for 6 hours to obtain small ball C.

[0084] Step 3: Measure 8 mL of 5 mg / mL platinum nitrate solution and 2 mL of 5 mg / mL palladium nitrate solution, mix the two solutions, add phosphoric acid, adjust the pH to 1.5, and impregnate the small balls C with an equal volume. Impregnate at 40℃ for 3 h, dry and calcine to obtain the noble metal spherical catalyst D009.

[0085] Example 10

[0086] This embodiment is Comparative Example 2. Compared with Example 8, this embodiment does not add a selectivity regulator. Specifically:

[0087] Step 1: Weigh 20.29g cerium nitrate, 16.64g zirconium nitrate, 20.26g magnesium nitrate and deionized water to prepare a 500mL mixed solution. Prepare a 0.5mol / L ammonia solution as a precipitant. Perform a precipitation reaction with the mixed solution and the precipitant. Control the precipitation temperature at 40℃ and the pH at 8.0. Aging for 8h, filter and wash, and dry the filter cake at 110℃ for 10h. Then calcine it at 500℃ for 5h to obtain powder A.

[0088] Step 2: Prepare 1000 mL of 0.4 wt% ammonium alginate aqueous solution. Mix 118.64 g of boehmite, powder A obtained in Step 1, and 3.39 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, dropwise add the mixture to 300 mL of a mixed salt solution containing 0.5 mol / L Ba(NO3)2 and 0.8 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 8 h, filter, wash, dry at 120 °C for 8 h, and calcine at 600 °C for 2 h to obtain small balls B.

[0089] Step 3: Measure 8 mL of 5 mg / mL platinum nitrate solution and 2 mL of 5 mg / mL palladium nitrate solution, mix the two solutions, add phosphoric acid, adjust the pH to 1.5, and impregnate an equal volume onto sphere B. Impregnate at 40℃ for 3 h, dry and calcine to obtain the noble metal spherical catalyst D010.

[0090] Example 11

[0091] This example is Comparative Example 3. Compared with Example 8, this example does not use ammonium alginate for preparation. Instead, it uses alumina powder obtained after calcining boehmite to support BaO, ZnO, CeO2, ZrO2, and MgO, and then rolls it into balls. Specifically:

[0092] Step 1: 118.64g of boehmite was calcined at 500℃ to obtain alumina powder; the alumina powder was impregnated with an equal volume of a mixed solution containing 20.29g of cerium nitrate, 16.64g of zirconium nitrate, 20.26g of magnesium nitrate, 0.15g of barium nitrate, and 0.24g of zinc nitrate (the solvent of the mixed solution was deionized water), stirred and evaporated to dryness in a water bath at 110℃, and then calcined at 500℃ for 5h to obtain powder A.

[0093] Step 2: Mix powder A with 3.39g of fly ash, roll into balls, dry at 120℃ for 8 hours, and calcine at 600℃ for 2 hours to obtain small balls B.

[0094] Step 3: Weigh 10.51g of nickel nitrate, 6.31g of cobalt acetate, and 1.47g of ammonium molybdate to prepare a mixed solution, add ammonia water, adjust the pH to 5.0, and immerse an equal volume of the solution on small ball B. Immerse at 50℃ for 3 hours and dry at 100℃ for 6 hours to obtain small ball C.

[0095] Step 4: Measure 8 mL of 5 mg / mL platinum nitrate solution and 2 mL of 5 mg / mL palladium nitrate solution, mix the two solutions, add phosphoric acid, adjust the pH to 1.5, and impregnate the small balls C with an equal volume. Impregnate at 40℃ for 3 h, dry and calcine to obtain the noble metal spherical catalyst D011.

[0096] Example 12

[0097] This embodiment is Comparative Example 4. Compared with Example 8, this embodiment does not add fly ash. Specifically:

[0098] Step 1: Weigh 20.29g cerium nitrate, 16.64g zirconium nitrate, and 20.26g magnesium nitrate and prepare a 500mL mixed solution with deionized water. Prepare a 0.5mol / L ammonia solution as a precipitant. Perform a precipitation reaction with the mixed solution and the precipitant, controlling the precipitation temperature at 40℃ and the pH at 8.0. Aging for 8 hours, followed by filtration and washing, and drying the filter cake at 110℃ for 10 hours and calcining at 500℃ for 5 hours to obtain powder A.

[0099] Step 2: Prepare 1000 mL of 0.4 wt% ammonium alginate aqueous solution. Mix 118.64 g of pseudoboehmite with powder A obtained in Step 1 and add it to the ammonium alginate aqueous solution. After homogenization and stirring, dropwise add it to 300 mL of a mixed salt solution containing 0.5 mol / L Ba(NO3)2 and 0.8 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 8 h, filter, wash, dry at 120 °C for 8 h, and calcine at 600 °C for 2 h to obtain small balls B.

[0100] Step 3: Weigh 10.51g of nickel nitrate, 6.31g of cobalt acetate, and 1.47g of ammonium molybdate and prepare a mixed solution with deionized water. Add ammonia water to adjust the pH to 5.0. Implant an equal volume of the solution onto the small ball B. Implant at 50℃ for 3 hours and dry at 100℃ for 6 hours to obtain the small ball C.

[0101] Step 4: Measure 8 mL of 5 mg / mL platinum nitrate solution and 2 mL of 5 mg / mL palladium nitrate solution, mix the two solutions, add phosphoric acid, adjust the pH to 1.5, and impregnate the small balls C with an equal volume. Impregnate at 40℃ for 3 h, dry and calcine to obtain the noble metal spherical catalyst D012.

[0102] Example 13

[0103] This example is Comparative Example 5. Compared with Example 8, this example does not add an acidity regulator. Specifically:

[0104] Step 1: Weigh 20.29g cerium nitrate, 16.64g zirconium nitrate, and 20.26g magnesium nitrate and prepare a 500mL mixed solution with deionized water. Prepare a 0.5mol / L ammonia solution as a precipitant. Perform a precipitation reaction with the mixed solution and the precipitant, controlling the precipitation temperature at 40℃ and the pH at 8.0. Aging for 8 hours, followed by filtration and washing, and drying the filter cake at 110℃ for 10 hours and calcining at 500℃ for 5 hours to obtain powder A.

[0105] Step 2: Prepare 1000 mL of 0.4 wt% ammonium alginate aqueous solution. Mix 118.64 g of boehmite, powder A obtained in Step 1, and 3.39 g of fly ash, and add them to the ammonium alginate aqueous solution. After homogenization and stirring, dropwise add the mixture to 300 mL of a mixed salt solution containing 0.5 mol / L Ba(NO3)2 and 0.8 mol / L Zn(NO3)2. After treatment with glacial acetic acid for 8 h, filter, wash, dry at 120 °C for 8 h, and calcine at 600 °C for 2 h to obtain small balls B.

[0106] Step 3: Weigh 10.51g of nickel nitrate, 6.31g of cobalt acetate, and 1.47g of ammonium molybdate and prepare a mixed solution with deionized water. Impregnate the small ball B with an equal volume of the solution, soak at 50℃ for 3 hours, and dry at 100℃ for 6 hours to obtain small ball C.

[0107] Step 4: Measure 8 mL of 5 mg / mL platinum nitrate solution and 2 mL of 5 mg / mL palladium nitrate solution, mix the two solutions, and impregnate the small spheres C with an equal volume. Impregnate at 40°C for 3 hours, dry and calcine to obtain the noble metal spherical catalyst D013.

[0108] Catalyst performance testing

[0109] The catalysts prepared in Examples 1-13 were placed in fixed-bed reactors, and their catalytic combustion performance was tested. The prepared catalysts were reduced in the fixed-bed reactors for 2-4 hours at a reduction temperature of 50-100°C and a space velocity of 500-5000 h⁻¹. -1 The pressure was 0–0.5 MPa, and the reducing gas composition was 10 vol% H2, with the remainder being N2. The feed gas and oxygen were then mixed in a specific ratio for activity evaluation. The volume fraction of H2 in the feed gas was 0.5–3.0%, the volume fraction of CH4 was 20%, and the volume hourly space velocity (VHSV) was 1000–5000 h⁻¹. -1 The reaction temperature was 10–200℃, and the bed pressure was 0.1–0.5 MPa. The test results after 500 hours of reaction are detailed in Table 1.

[0110] Table 1. Test results of catalyst performance and mechanical strength

[0111]

[0112] As shown in Table 1 above, after 500 hours of operation, the catalyst of this invention still maintains a H2 conversion rate close to 100%, an outlet hydrogen gas fraction of less than 0.1 ppm, and an outlet carbon dioxide volume fraction of less than 30 ppm. It can simultaneously maintain a high H2 conversion rate and an extremely low CH4 conversion rate within a reaction temperature range of 10–200 °C. In contrast, the outlet H2 and CO2 of catalyst D009 in Comparative Example 1 both increased. While the outlet H2 of catalyst D010 remained below 0.1 ppm, the outlet CO2 increased significantly. This indicates that the addition of the promoter in the support helps improve the H2 conversion rate, but simultaneously promotes the oxidation of CH4. The modification of the selectivity regulator did not significantly promote the catalytic oxidation of H2, but it could inhibit CO2 generation. In Comparative Example 3, the outlet H2 concentration of catalyst D011 increased, and the catalyst strength decreased. In Comparative Example 4, both outlet H2 and CO2 of catalyst D012 increased, indicating that ammonium alginate and fly ash are indispensable in the support formation process. The ammonium alginate molding method creates hierarchical channels within the spherical catalyst, facilitating the diffusion of reactant molecules into the catalyst's internal structure, increasing the reaction rate, and allowing for a more uniform distribution of barium oxide and zinc oxide. This uniform distribution of barium oxide and zinc oxide interacts with the additives in the support, enhancing the catalyst's oxygen storage capacity, increasing oxygen vacancies, and significantly improving H2 conversion. Furthermore, the introduction of various low-content elements such as Fe and Ti into the fly ash not only improves the catalyst's strength but also promotes the dispersion of precious metals on the support surface, enhancing the catalyst's activity. In contrast, the direct mixing of fly ash with alumina powder loaded with additives during the D011 catalyst preparation process does not increase the strength to over 100 N / particle. In Comparative Example 5, the increased outlet H2 and CO2 in D013 indicate that the acid-base regulator simultaneously improves the catalytic activity of H2 and inhibits CH4 oxidation. The acid-base regulator alters the loading depth and dispersion of the active components and selective regulators on the catalyst surface, simultaneously increasing H2 conversion and decreasing CH4 conversion.

[0113] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0114] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A selective catalytic oxidation dehydrogenation noble metal catalyst for crude helium refining, characterized in that, The catalyst comprises an active component, a support, an additive, and a selectivity modifier; wherein the active component is selected from any one or two of Pt, Pd, and Ru, and the content of the active component, calculated as metal, is greater than 0 and less than or equal to 0.15 wt%; the support is alumina microspheres doped with fly ash and additives, prepared with the assistance of ammonium alginate, and the additive element is any one or more of Ce, La, Y, Zr, Mg, and Sr, and the content of the support is 89.85~99 wt%; the selectivity modifier is selected from any one or more of Ni, Mn, Co, Mo, W, and Nb, and the content of the selectivity modifier, calculated as oxide, is 1~10 wt%, and the sum of all components of the catalyst is 100%; The method for preparing the catalyst includes the following steps: Step 1. Dissolve any one or more of cerium nitrate, lanthanum nitrate, yttrium nitrate, zirconium nitrate, zirconium oxychloride, magnesium nitrate, and strontium nitrate to prepare a mixed solution; add a precipitant to carry out a precipitation reaction, control the pH at 7.0~9.5, and after aging, filtration, washing, drying, and calcination, obtain powder A; Step 2. Mix boehmite, powder A, and fly ash in a certain proportion and add them to an ammonium alginate aqueous solution. After homogenization and stirring, add the mixture dropwise to a mixed salt solution of Ba(NO3)2 and Zn(NO3)2. After treatment with glacial acetic acid for 4-8 hours, filter, wash, dry at 80-120℃ for 4-8 hours, and calcine at 400-600℃ to obtain small balls B. Step 3. Prepare a solution of the precursor of the selective regulator, add a pH adjuster to adjust the pH to a certain range, and impregnate an equal volume of the solution onto microspheres B. After impregnation at 10~60℃ for 2~4 hours, dry at 80~120℃ for 4~8 hours to obtain microspheres C. Step 4. Prepare a solution of the precursor of the active component, add a pH adjuster to adjust the pH to a certain range, and impregnate an equal volume of the solution onto the spheres C. After impregnation at 10~60℃ for 2~4 hours, dry and calcine to obtain the noble metal spherical catalyst D.

2. The selective catalytic oxidation dehydrogenation noble metal catalyst for crude helium refining according to claim 1, characterized in that: The precursor of the active component is platinum nitrate, chloroplatinic acid, palladium nitrate, chloropalladium acid, ruthenium nitrate, or ruthenium trichloride; the precursor of the selectivity regulator is nickel nitrate, manganese nitrate, cobalt nitrate, cobalt acetate, ammonium molybdate, ammonium metatungstate, or ammonium niobate.

3. The crude helium refining selective catalytic oxidation dehydrogenation noble metal catalyst according to claim 1, characterized in that: In step 1, the molar concentration of the mixed solution is 0.01~1.0 mol / L; the precipitant is any one of ammonia, Na2CO3, and ammonium carbonate, and the concentration of the precipitant solution is 0.01~1.0 mol / L; the precipitation and aging temperature is 10~80℃, the aging time is 2~24 hours, the drying conditions are drying at 80~120℃ for 8~12 hours, and the calcination conditions are calcination at 300~600℃ for 4~8 hours.

4. The crude helium refining selective catalytic oxidation dehydrogenation noble metal catalyst according to claim 1, characterized in that: In step 2, the mass ratio of pseudoboehmite to powder A is 4-9, and the mass ratio of pseudoboehmite to fly ash is 20-40.

5. The selective catalytic oxidation dehydrogenation noble metal catalyst for crude helium refining according to claim 1, characterized in that: In step 3, the pH adjuster is any one or more of nitric acid, hydrochloric acid, phosphoric acid, glacial acetic acid, citric acid, tartaric acid, potassium citrate, potassium bicarbonate, and ammonia water, and the pH range during the impregnation process is controlled to be 1.0~6.

0.

6. The crude helium refining selective catalytic oxidation dehydrogenation noble metal catalyst according to claim 1, characterized in that: In step 4, the pH adjuster is any one or more of nitric acid, hydrochloric acid, phosphoric acid, glacial acetic acid, citric acid, tartaric acid, potassium citrate, potassium bicarbonate, and ammonia water, and the pH range during the impregnation process is controlled to be 0.5~3.

5.

7. The application of the crude helium refining selective catalytic oxidation dehydrogenation noble metal catalyst according to any one of claims 1-6, characterized in that: This catalyst is used in catalytic oxidation dehydrogenation units for helium extraction from natural gas or BOG, enabling selective catalytic oxidation of hydrogen.

8. The application of the crude helium refining selective catalytic oxidation dehydrogenation noble metal catalyst according to claim 7, characterized in that: In the catalytic oxidative dehydrogenation unit for helium extraction from natural gas or BOG, crude helium is mixed with air, diluted, and then fed into the dehydrogenation reactor. Hydrogen and oxygen in the crude helium react under catalysis to produce water. The volume fraction of H2 in the reactant gas is 0.5–3.0%, and the volume hourly space velocity (VHSV) is 1000–5000 h⁻¹. -1 The reaction temperature is 10~200℃, the bed pressure is 0.1~0.5MPa, and the volume fraction of H2 in the outlet gas is less than 0.1ppm and the volume fraction of CO2 is less than 30ppm.

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