Modified beta molecular sieve as well as preparation method and application thereof
By loading alkaline earth metals and ruthenium onto β-zeolites, modified β-zeolites were prepared, solving the problems of insufficient activity and stability of existing catalysts and realizing a low-temperature and efficient ammonia decomposition hydrogen production process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-20
- Publication Date
- 2026-05-22
Smart Images
Figure CN122071015A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalytic materials technology, specifically to a modified β-zeolite, its preparation method, and its application. Background Technology
[0002] Hydrogen is the most abundant element in the universe. Hydrogen gas can generate a large amount of heat through combustion and can also provide energy through hydrogen fuel cells. Furthermore, the byproduct of hydrogen combustion is water, which causes no pollution to the environment, making hydrogen a highly regarded clean energy source. However, due to hydrogen's low volumetric energy density and difficulties in transportation, the widespread application of hydrogen energy is severely limited by factors such as high storage costs and low transportation efficiency. Using ammonia as a hydrogen storage carrier, and producing hydrogen on-site through ammonia decomposition, can effectively avoid the problems associated with hydrogen storage and transportation. However, without a catalyst, the thermal decomposition of ammonia requires temperatures above 800°C, and these high temperatures severely affect the energy efficiency of using ammonia-loaded hydrogen.
[0003] Catalysts for hydrogen production from ammonia decomposition typically employ supported catalysts, using active metals such as Ru, Ni, Co, and Fe as active metals and carbon nanotubes, MgO, CeO2, and molecular sieves as supports. Cha et al. reported a Ru-based catalyst supported on NaY molecular sieves [Catalysis B: Environmental. 2021; 283:119627], and Hu et al. reported a Ni-based catalyst supported on HZSM-5 [Applied Catalysis A: General. 2018; 562:49-57.]. While some progress has been made in the research of these catalysts, further improvements are still possible.
[0004] Therefore, developing efficient catalysts to lower the temperature of ammonia decomposition reaction is crucial for the application and promotion of ammonia hydrogen-carrying industry. Summary of the Invention
[0005] The purpose of this invention is to overcome the problems of poor catalytic activity and poor stability of molecular sieve catalysts in the prior art, and to provide a modified β molecular sieve, its preparation method and application. The modified β molecular sieve has strong basicity, high catalytic activity and excellent activity stability.
[0006] To achieve the above objectives, a first aspect of the present invention provides a modified β-molecular sieve, wherein the modified β-molecular sieve comprises an alkaline earth metal type β-molecular sieve and a ruthenium element supported on the alkaline earth metal type β-molecular sieve;
[0007] The modified β molecular sieve showed a CO2 adsorption capacity of 1.5-3.5 mmol / g as determined by CO2-TPD testing.
[0008] After reduction at 500℃ for 1 hour in a hydrogen atmosphere, the Ru dispersion of the modified β molecular sieve was 12-20% according to CO pulse adsorption test.
[0009] Preferably, the modified β molecular sieve has a CO2 adsorption capacity of 1.86-3.04 mmol / g as determined by CO2-TPD test.
[0010] Preferably, after reduction at 500°C for 1 hour in a hydrogen atmosphere, the Ru dispersion of the modified β molecular sieve is 13.6-18.8% after CO pulse adsorption testing.
[0011] Preferably, based on the total amount of the modified β molecular sieve, the ruthenium content is 0.1-5% by weight, preferably 0.3-3% by weight.
[0012] Preferably, the alkaline earth metal type β molecular sieve is obtained by β molecular sieve through alkaline earth metal ion exchange.
[0013] Preferably, the alkaline earth metal is selected from at least one of Ca, Sr and Ba.
[0014] Preferably, based on the total amount of the modified β molecular sieve, the content of alkaline earth metal elements is 1-10% by weight, preferably 5-10% by weight.
[0015] A second aspect of the present invention provides a method for preparing the modified β-zeolite described in the first aspect, wherein the method comprises:
[0016] The modified β-zeolite is obtained by loading active metal ruthenium onto an alkaline earth metal β-zeolite.
[0017] Preferably, the preparation method of the alkaline earth metal type β molecular sieve includes: mixing the β molecular sieve with a solution containing an alkaline earth metal source, performing ion exchange, separating the solid and liquid to obtain a solid product, and drying and calcining the solid product to obtain the alkaline earth metal type β molecular sieve.
[0018] Preferably, the β-zeolite is a Na-type β-zeolite.
[0019] The third aspect of this invention provides an application of the modified β molecular sieve described in the first aspect in the field of ammonia decomposition for hydrogen production.
[0020] The beneficial effects achieved through the above technical solution are as follows:
[0021] (1) In this invention, the modified β-zeolite provided is highly basic, which can improve the electron-donating ability of the catalyst, thereby improving the catalytic activity. Simultaneously, the highly basic modified β-zeolite has a strong interaction with the active metal ruthenium, which can improve the dispersion of the active metal. Using the modified β-zeolite as a catalyst results in high catalytic activity and excellent activity stability;
[0022] (2) In this invention, preferably, the preparation method of the modified β molecular sieve is simple, the conditions are controllable, the raw materials are easy to obtain and the cost is low. The modified β molecular sieve is used as a catalyst in the field of ammonia decomposition to produce hydrogen, which can improve the ammonia conversion rate and reduce the reaction temperature required for ammonia conversion, thereby achieving low-temperature and low-cost hydrogen production. Attached Figure Description
[0023] Figure 1 These are CO2-TPD diagrams of the modified β-zeolites in the embodiments and comparative examples of this invention;
[0024] Figure 2 These are the XRD patterns of the modified β-zeolites in the embodiments and comparative examples of the present invention;
[0025] Figure 3 These are the ammonia conversion rate test results of the catalysts in the embodiments and comparative examples of this invention;
[0026] Figure 4 These are the results of the ammonia decomposition activity and stability test of the catalyst prepared in Example 1 of this invention. Detailed Implementation
[0027] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0028] The first aspect of the present invention provides a modified β molecular sieve, wherein the modified β molecular sieve comprises an alkaline earth metal type β molecular sieve and a ruthenium element supported on the alkaline earth metal type β molecular sieve;
[0029] The modified β molecular sieve showed a CO2 adsorption capacity of 1.5-3.5 mmol / g as determined by CO2-TPD testing.
[0030] After reduction at 500℃ for 1 hour in a hydrogen atmosphere, the Ru dispersion of the modified β molecular sieve was 12-20% according to CO pulse adsorption test.
[0031] In this invention, the modified β molecular sieve is highly basic, and the active metal ruthenium interacts strongly with the alkaline earth metal type β molecular sieve. Using the modified β molecular sieve as a catalyst results in high catalytic activity and excellent activity stability.
[0032] According to the present invention, preferably, the modified β-molecular sieve exhibits a CO2 adsorption capacity of 1.5-3.5 mmol / g as determined by CO2-TPD testing, for example, 1.5 mmol / g, 1.54 mmol / g, 1.58 mmol / g, 1.62 mmol / g, 1.68 mmol / g, 1.72 mmol / g, 1.76 mmol / g, 1.8 mmol / g, 1.86 mmol / g, 1.92 mmol / g, 1.96 mmol / g, 2 mmol / g, 2.04 mmol / g, etc. The CO2 adsorption capacity is 2.1 mmol / g, 2.2 mmol / g, 2.3 mmol / g, 2.4 mmol / g, 2.5 mmol / g, 2.6 mmol / g, 2.7 mmol / g, 2.8 mmol / g, 2.9 mmol / g, 3 mmol / g, 3.04 mmol / g, 3.1 mmol / g, 3.2 mmol / g, 3.3 mmol / g, 3.4 mmol / g, 3.5 mmol / g, or any range between the two, preferably 1.86-3.04 mmol / g. In this invention, the CO2-TPD test includes: adsorbing CO2 onto the modified β-molecular sieve, purging with helium at 100°C for 0.5 hours, and then performing a temperature-programmed desorption process from 100°C to 650°C to obtain a desorption curve. The peak area is obtained by fitting the desorption curve, and the CO2 adsorption capacity is calculated based on the CO2 standard curve.
[0033] In this invention, CO2-TPD was used to test the basicity of the modified β-zeolite. The test results show that the modified β-zeolite, after alkaline earth metal ion exchange, exhibits a larger CO2 desorption peak area compared to conventional Naβ-zeolite catalysts, indicating stronger basicity of the alkaline earth metal β-zeolite.
[0034] According to the present invention, preferably, after reduction at 500°C for 1 hour in a hydrogen atmosphere, the Ru dispersion of the modified β molecular sieve is 12-20% after CO pulse adsorption testing, for example, 12%, 12.4%, 12.8%, 13%, 13.2%, 13.4%, 13.6%, 13.8%, 14%, 14.4%, 14.8%, 15.2%, 15.6%, 16%, 16.2%, 16.4%, 16.8%, 17.2%, 17.6%, 18%, 18.4%, 18.8%, 19%, 20%, or any range between the two, preferably 13.6-18.8%.
[0035] In this invention, the CO pulse adsorption test includes: reducing the modified β molecular sieve at 500°C for 1 hour in a hydrogen atmosphere, then introducing 0.5 mL of CO gas into the modified β molecular sieve sample in pulses at room temperature until CO adsorption reaches saturation. The amount of ruthenium metal exposed on the surface of the modified β molecular sieve is calculated based on the amount of CO consumed. The ratio of the amount of ruthenium metal exposed on the surface of the modified β molecular sieve to the total amount of ruthenium metal loaded in the sample is calculated to obtain the Ru dispersion of the modified β molecular sieve.
[0036] In this invention, the active metal ruthenium supported in the modified β molecular sieve has high dispersion, strong interaction with the support, and high catalytic activity.
[0037] According to the present invention, preferably, based on the total amount of the modified β-zeolite, the ruthenium content is 0.1-5 wt%, more preferably 0.3-3 wt%, for example 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, 2.8 wt%, 3 wt%, or any range between the two, more preferably 0.5-2 wt%. In the present invention, the ruthenium content is determined by X-ray fluorescence spectroscopy (XRF).
[0038] In this invention, ruthenium is dispersed and supported on an alkaline earth metal β-zeolite. The active ruthenium interacts strongly with the support, enhancing the catalytic activity of the modified β-zeolite as a catalyst. Insufficient ruthenium content results in poor catalytic activity; excessive ruthenium content leads to high catalyst costs and agglomeration.
[0039] According to the present invention, the source of the alkaline earth metal β-zeolite is not particularly limited; it can be commercially available or prepared using existing methods. Preferably, the alkaline earth metal β-zeolite is obtained by β-zeolite through alkaline earth metal ion exchange. In the present invention, the method of alkaline earth metal ion exchange is not particularly limited; those skilled in the art can choose conventional ion exchange methods, as long as the obtained alkaline earth metal β-zeolite meets the aforementioned limitations.
[0040] In this invention, the silicon-to-aluminum molar ratio of the modified β-zeolite is not particularly limited. Those skilled in the art can adaptably select a suitable silicon-to-aluminum molar ratio to meet the requirements of the β-zeolite. Preferably, the silicon-to-aluminum molar ratio SiO2 / Al2O3 of the modified β-zeolite is 1:0.01-0.1.
[0041] According to the present invention, preferably, the alkaline earth metal is selected from at least one of Ca, Sr and Ba, and preferably Sr.
[0042] According to the present invention, preferably, based on the total amount of the modified β molecular sieve, the content of alkaline earth metal elements is 1-10% by weight, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range between the two, preferably 5-10% by weight. In the present invention, the content of the alkaline earth metal elements is determined by X-ray fluorescence spectroscopy (XRF).
[0043] According to the present invention, preferably, the specific surface area of the modified β molecular sieve is 300-650 m². 2 / g, for example 300m 2 / g, 350m 2 / g、400m 2 / g、450m 2 / g、500m 2 / g、550m 2 / g、600m 2 / g、650m 2 / g, or any range between the two, preferably 400-600m 2 / g.
[0044] According to the present invention, preferably, the modified β-zeolite has a microporous specific surface area of 300-600 m². 2 / g, for example 300m 2 / g, 350m 2 / g、400m 2 / g、450m 2 / g、500m 2 / g、550m 2 / g、600m 2 / g, or any range between the two, preferably 400-550m 2 / g. In this invention, the modified β-zeolite has a large specific surface area and micropore specific surface area, which can provide more basic active sites and improve catalytic activity.
[0045] According to the present invention, preferably, the pore volume of the modified β molecular sieve is 0.25-0.5 cm³. 3 / g, for example, 0.25cm 3 / g, 0.3cm 3 / g, 0.35cm 3 / g, 0.4cm 3 / g, 0.45cm 3 / g, 0.5cm 3 / g, or any range between the two, preferably 0.3-0.45cm 3 / g.
[0046] In this invention, the specific surface area, micropore specific surface area, and pore volume of the modified β-molecular sieve were measured using the low-temperature nitrogen adsorption capacity method. The experimental instrument was a Micromeritics ASAP2400 static nitrogen adsorption instrument. Experimental conditions: The sample was degassed under vacuum at 1.33 Pa and 300 °C for 4 hours, then contacted with liquid nitrogen at 77 K for isothermal adsorption and desorption. Adsorption and desorption isotherms were measured, and the specific surface area, micropore specific surface area, and pore volume were calculated using the BET formula.
[0047] A second aspect of the present invention provides a method for preparing the modified β-zeolite described in the first aspect, wherein the method comprises:
[0048] The modified β-zeolite is obtained by loading active metal ruthenium onto an alkaline earth metal β-zeolite.
[0049] In this invention, preferably, the preparation method of the modified β molecular sieve is simple, the conditions are controllable, the raw materials are readily available and the cost is low, and the active metal ruthenium is loaded onto the alkaline earth metal type β molecular sieve to improve the catalytic activity of the alkaline earth metal type β molecular sieve.
[0050] According to the present invention, the preparation method of the alkaline earth metal β-zeolite is not particularly limited, as long as the above-mentioned parameter limitations are met. According to a preferred embodiment of the present invention, the preparation method of the alkaline earth metal β-zeolite includes: mixing the β-zeolite with a solution containing an alkaline earth metal source, performing ion exchange, separating the solid and liquid phases to obtain a solid product, and drying and calcining the solid product to obtain the alkaline earth metal β-zeolite.
[0051] According to the present invention, preferably, the β-zeolite is a Na-type β-zeolite. In this invention, Na-type β-zeolite is used as the raw material, which is readily available and its source is not particularly limited; it can be commercially available or prepared using existing methods.
[0052] According to the present invention, preferably, based on 1g of β molecular sieve, the molar amount of alkaline earth metal added to the solution containing the alkaline earth metal source is 0.001-0.1mol, more preferably 0.005-0.02mol.
[0053] According to the present invention, the solvent of the solution containing the alkaline earth metal source is water, and the concentration of the solution is not particularly limited. Preferably, the molar concentration of the alkaline earth metal in the solution containing the alkaline earth metal source is 0.1-2 mol / L, more preferably 0.5-1.5 mol / L.
[0054] According to the present invention, preferably, the alkaline earth metal is selected from at least one of Ca, Sr and Ba, and preferably Sr.
[0055] According to the present invention, the method and conditions for ion exchange are not particularly limited, and are conventional ion exchange methods and conditions in the art. Preferably, the ion exchange conditions include: a reaction temperature of 20-100℃, such as 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, or any range between the two, preferably 25-50℃; for example, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 24h, 28h, 30h, 32h, 36h, or any range between the two; and a reaction time of 0.5-36h, preferably 4-30h. In the present invention, when the ion exchange temperature is high, those skilled in the art can appropriately adjust the ion exchange time, and the obtained alkaline earth metal β-molecular sieve can satisfy the aforementioned parameter limitations.
[0056] In this invention, the method of solid-liquid separation is not particularly limited, but filtration is preferred, and depressurization filtration is even more preferred.
[0057] In this invention, preferably, the method further includes washing the solid-liquid separation product. Washing can be performed using conventional methods and conditions in the art. According to some preferred embodiments of the invention, washing can be performed using deionized water. Preferably, the number of washing cycles is 1-4.
[0058] According to the present invention, the drying can be carried out using conventional methods and conditions in the art. Preferably, the drying conditions include a drying temperature of 100-140°C and a drying time of 1-4 hours.
[0059] According to the present invention, preferably, the calcination conditions include: a calcination temperature of 400-600℃, more preferably 450-550℃; and a calcination time of 2-8h, more preferably 3-5h.
[0060] According to the present invention, preferably, the amount of active metal ruthenium and alkaline earth metal type β molecular sieve is such that, based on the total amount of the modified β molecular sieve obtained, the content of ruthenium element is 0.1-5% by weight, preferably 0.3-3% by weight, and more preferably 0.5-2% by weight.
[0061] In this invention, the loading method and conditions are not particularly limited. Those skilled in the art can choose conventional loading methods that can load active ruthenium metal onto alkaline earth metal β-molecular sieves. According to a preferred embodiment of this invention, the loading method is selected from at least one of impregnation, precipitation deposition and solid-phase ion exchange.
[0062] In this invention, the conditions of the impregnation method are not particularly limited. Those skilled in the art can choose a conventional impregnation method to load active metal ruthenium. According to a preferred embodiment of this invention, the impregnation method includes: mixing an alkaline earth metal type β molecular sieve with a solution containing a ruthenium source, drying and then calcining to obtain a modified β molecular sieve.
[0063] In this invention, the type of ruthenium source is not particularly limited, and can be any soluble compound that can provide ruthenium, which is conventional in the art. It is preferably selected from at least one of ruthenium chloride, ruthenium acetate, hexaammineruthenium chloride, and ruthenium acetylacetonate, with ruthenium chloride being the most preferred.
[0064] In this invention, preferably, the solvent in the ruthenium source-containing solution is water. The mass concentration of the ruthenium source-containing solution is not particularly limited, but preferably, based on ruthenium element, the mass concentration of the ruthenium source-containing solution is 2-10 g / L, more preferably 4-6 g / L.
[0065] According to the present invention, drying can be carried out using conventional methods and conditions in the art. According to some preferred embodiments of the present invention, the dried solid sample obtained by rotary evaporation drying is further dried. Preferably, the drying conditions include: a drying temperature of 100-140°C and a drying time of 1-4 hours.
[0066] In this invention, preferably, the calcination conditions of the impregnation method include: a calcination temperature of 300-600℃, preferably 400-550℃; and a calcination time of 3-8h, preferably 4-7h.
[0067] In this invention, the conditions of the precipitation deposition method are not particularly limited. According to a preferred embodiment of the present invention, the precipitation deposition method includes: heating a mixture containing a ruthenium source and an alkaline earth metal type β molecular sieve, a precipitant and a solvent, separating the solid and liquid to obtain a solid product, and then drying and calcining it to obtain a modified β molecular sieve.
[0068] In this invention, the types of ruthenium sources are described in the foregoing specification and will not be repeated here.
[0069] In this invention, preferably, the solvent is water. The amount of solvent added is not particularly limited and can be adjusted by those skilled in the art according to the heating conditions.
[0070] In this invention, the precipitant is a conventional precipitant in the art, preferably selected from at least one of sodium hydroxide, potassium hydroxide, and urea, and more preferably urea. Using urea as a precipitant allows for slow precipitation and deposition, resulting in a more uniform distribution of Ru metal particles. The amount of precipitant used is not particularly limited and can be adjusted by those skilled in the art based on the precipitation of Ru metal in alkaline earth metal β-molecular sieves.
[0071] In this invention, preferably, the heating conditions include: a heating temperature of 60-100℃, more preferably 70-90℃; and a heating time of 5-15h, more preferably 8-12h.
[0072] In this invention, preferably, the heating is carried out under stirring conditions. The stirring rate is not particularly limited, as long as the mixture is mixed evenly.
[0073] In this invention, preferably, the method further includes, after heating is stopped, cooling the heated product to perform solid-liquid separation, washing the obtained solid product, and then drying it. The conditions for solid-liquid separation are not particularly limited, but vacuum filtration is preferred. The washing can be performed with deionized water until the washing solution is neutral.
[0074] In this invention, the drying conditions are not particularly limited and are conventional drying conditions in the art, as described in the foregoing specification, and will not be repeated here.
[0075] In this invention, preferably, the calcination conditions of the precipitation deposition method include: a calcination temperature of 300-600℃, preferably 400-550℃; and a calcination time of 3-8h, preferably 4-7h.
[0076] In this invention, preferably, the conditions of the solid-phase ion exchange method are not particularly limited. According to a preferred embodiment of the present invention, the solid-phase ion exchange method includes: mechanically mixing a ruthenium source and an alkaline earth metal type β molecular sieve and then calcining them to obtain a modified β molecular sieve.
[0077] In this invention, the types of ruthenium sources are described in the foregoing specification and will not be repeated here.
[0078] In this invention, the mechanical mixing method is not particularly limited, and those skilled in the art can choose conventional mechanical mixing methods, preferably ball milling. The ball milling conditions and equipment are not particularly limited, but preferably, ball milling is carried out in a ball mill jar. The ball milling conditions include: a ball milling speed of 100-200 rpm and a ball milling time of 5-30 minutes.
[0079] In this invention, preferably, the calcination conditions of the solid-phase ion exchange method include: a calcination temperature of 400-700℃, preferably 500-600℃; and a calcination time of 2-8h, preferably 3-7h.
[0080] In this invention, preferably, the method further includes using the modified Y-type molecular sieve as a catalyst after reduction and activation.
[0081] In this invention, the reduction conditions are not particularly limited. Preferably, the reduction conditions include: in the presence of a reducing atmosphere, a reduction temperature of 200-600℃, more preferably 200-500℃, and a reduction time of 0.5-3h, more preferably 1-3h.
[0082] In this invention, the reducing atmosphere is a hydrogen-containing atmosphere, preferably hydrogen gas.
[0083] A third aspect of this invention provides an application of the modified β molecular sieve described in the first aspect in the field of ammonia decomposition for hydrogen production.
[0084] In this invention, the modified β molecular sieve described above is used as a catalyst in the field of ammonia decomposition for hydrogen production. It exhibits high catalytic activity, which can improve the ammonia conversion rate and reduce the reaction temperature required for ammonia conversion, thereby achieving low-temperature and low-cost hydrogen production.
[0085] In this invention, the reaction conditions and equipment for hydrogen production from ammonia decomposition are not particularly limited, and those skilled in the art can choose suitable reaction conditions and equipment for hydrogen production from ammonia decomposition.
[0086] In this invention, preferably, the raw material for the ammonia decomposition to hydrogen production reaction is ammonia gas.
[0087] According to a preferred embodiment of the present invention, when the ammonia decomposition to produce hydrogen is carried out in a fixed-bed reactor, the reaction pressure is atmospheric pressure, the reaction temperature is 300-600°C, and the gas hourly space velocity of the feedstock is 1000-50000 mL NH3·g. cat -1 ·h -1 Preferably, it is 3000-10000 mL NH3·g cat -1 ·h -1 .
[0088] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available.
[0089] In this invention, the room temperature is 25°C;
[0090] The Naβ molecular sieve was produced by Tianjin Yuanli Chemical Co., Ltd., with a SiO2 / Al2O3 ratio of 11.8.
[0091] S BET =597m 2 / g.
[0092] Example 1 of preparation of alkaline earth metal β molecular sieve
[0093] 8.007 g of strontium chloride was dissolved in 50 mL of deionized water, and then 5 g of Naβ molecular sieve was added. The mixture was heated to 50 °C with stirring for ion exchange for 4 hours. The exchanged product was filtered under reduced pressure and washed three times with deionized water. The solid product was then dried at 120 °C for 2 hours and calcined at 450 °C for 4 hours to obtain Srβ molecular sieve, denoted as Al.
[0094] Example 2 of preparation of alkaline earth metal β molecular sieve
[0095] 7.499 g of calcium chloride dihydrate was dissolved in 50 mL of deionized water, and then 5 g of Naβ molecular sieve was added. Ion exchange was performed at room temperature for 24 hours with stirring. The exchanged product was filtered under reduced pressure and washed three times with deionized water. The solid product was then dried at 120 °C for 2 hours and calcined at 450 °C for 4 hours to obtain Caβ molecular sieve, denoted as A2.
[0096] Example 3 of preparation of alkaline earth metal β molecular sieve
[0097] 12.275 g of barium chloride dihydrate was dissolved in 50 mL of deionized water, and then 5 g of Naβ molecular sieve was added. The mixture was heated to 100 °C with stirring and subjected to ion exchange for 0.5 hours. The exchanged product was filtered under reduced pressure and washed three times with deionized water. The solid product was then dried at 120 °C for 2 hours and calcined at 450 °C for 4 hours to obtain Baβ molecular sieve, denoted as A3.
[0098] Example 4 of preparation of alkaline earth metal β molecular sieve
[0099] 3.202 g of strontium chloride was weighed and dissolved in 50 mL of deionized water. Then, 5 g of Naβ molecular sieve was added, and ion exchange was performed at room temperature for 2 hours with stirring. The exchanged product was filtered under reduced pressure and washed three times with deionized water. The solid product was then dried at 120 °C for 2 hours and calcined at 300 °C for 2 hours to obtain Srβ molecular sieve, denoted as A4.
[0100] Example 5 of preparation of alkaline earth metal β molecular sieve
[0101] Ion exchange was performed according to Alkaline Earth Metal β-zeolite Preparation Example 1, except that the amount of strontium chloride added was adjusted to 16.013 g, and other conditions were the same as in Alkaline Earth Metal β-zeolite Preparation Example 1. The resulting Srβ-zeolite was denoted as A5.
[0102] Example 1
[0103] 0.135 g of ruthenium chloride trihydrate was fully dissolved in 10 mL of water, and 4.95 g of Srβ molecular sieve (Al) prepared in Example 1 was added. The sample was dried by rotary evaporation and then further dried at 120 °C for 2 h and calcined at 450 °C for 4 h.
[0104] Example 2
[0105] Add 0.135g of ruthenium chloride trihydrate and 4.95g of Caβ molecular sieve (A2) prepared in Example 2 to a ball mill jar, then ball mill at 100 rpm for 10 min, and calcine the ball-milled product at 600℃ for 3 h.
[0106] Example 3
[0107] 0.135 g of ruthenium chloride trihydrate, 4.95 g of Baβ molecular sieve (A3) prepared in Example 3 of alkaline earth metal β molecular sieve preparation, 5 g of urea, and 250 mL of deionized water were added to a round-bottom flask. The mixture was then heated to 90 °C with stirring and maintained for 10 h. Stirring was stopped, the product was cooled, and the product was filtered under reduced pressure. Finally, the solid product was washed with deionized water until the washing liquid was neutral. The solid product was then dried at 120 °C for 2 h and calcined at 450 °C for 4 h.
[0108] Example 4
[0109] 0.405 g of ruthenium chloride trihydrate was fully dissolved in 10 mL of water, and 4.95 g of Srβ molecular sieve (Al) prepared in Example 1 was added. The sample was dried by rotary evaporation and then further dried at 120 °C for 2 h and calcined at 450 °C for 4 h.
[0110] Example 5
[0111] Modified β-zeolites were prepared according to the method of Example 1, except that Srβ-zeolite A1 was replaced with an equal mass of Srβ-zeolite A4, and other conditions were the same as in Example 1.
[0112] Example 6
[0113] Modified β-zeolites were prepared according to the method of Example 1, except that Srβ-zeolite A1 was replaced with an equal mass of Srβ-zeolite A5, and other conditions were the same as in Example 1.
[0114] Comparative Example 1
[0115] Dissolve 0.135g of ruthenium chloride trihydrate (containing 37wt% ruthenium) completely in 10mL of water, then add 4.95g of commercially available NaY molecular sieve (Dalian Zeer Catalytic Materials, SiO2 / Al2O3 = 5.8, S... BET =827m 2 / g), rotary evaporation drying to obtain a dry solid sample, further drying at 120℃ for 2h, and calcining at 450℃ for 4h.
[0116] Comparative Example 2
[0117] 0.135 g of ruthenium chloride trihydrate was fully dissolved in 10 mL of water, and 4.95 g of commercially available Naβ molecular sieve was added. The sample was dried by rotary evaporation to obtain a dry solid sample, which was then further dried at 120 °C for 2 h and calcined at 450 °C for 4 h.
[0118] Comparative Example 3
[0119] Weigh 7.499g of calcium chloride dihydrate and dissolve it in 50mL of deionized water. Then add 5g of NaY molecular sieve (Dalian Zeer Catalytic Materials, SiO2 / Al2O3 = 5.8, S...). BET =827m 2 / g), and ion exchange was carried out at room temperature for 24 hours with stirring. The exchanged product was filtered under reduced pressure and washed three times with deionized water. The solid product was then dried at 120℃ for 2 hours and calcined at 450℃ for 4 hours to obtain CaY molecular sieve.
[0120] Modified molecular sieves were prepared according to the method of Example 1, except that Caβ molecular sieves were replaced with an equal mass of CaY molecular sieves, and other conditions were the same as in Example 1.
[0121] Comparative Example 4
[0122] Following the method of Alkaline Earth Metal Type β Molecular Sieves Preparation Example 1, except that strontium chloride was replaced with an equimolar amount of cerium chloride, and other conditions were the same as in Alkaline Earth Metal Type β Molecular Sieves Preparation Example 1, Ceβ molecular sieve was obtained.
[0123] Modified molecular sieves were prepared according to the method of Example 1, except that the Srβ molecular sieve support was replaced with an equal mass of Ceβ molecular sieve, and other conditions were the same as in Example 1.
[0124] Comparative Example 5
[0125] (1) Dissolve 0.135g of ruthenium chloride trihydrate in 10mL of water, add 4.95g of commercially available Naβ molecular sieve, and dry by rotary evaporation to obtain a dry solid sample. Further dry at 120℃ for 2h and calcine at 450℃ for 4h.
[0126] (2) Weigh 7.499 g of calcium chloride dihydrate and dissolve it in 50 mL of deionized water. Then add 5 g of the ruthenium-loaded Naβ molecular sieve from step (1) and perform ion exchange at room temperature for 24 hours with stirring. Filter the exchanged product under reduced pressure and wash the solid product three times with deionized water. Then dry the solid product at 120 °C for 2 h and calcine it at 450 °C for 4 h.
[0127] Table 1 shows the composition and pore structure parameters of the modified β molecular sieve. The specific surface area, pore volume and average pore size were measured by the low-temperature nitrogen adsorption capacity method.
[0128] The content of Ru and other cationic metals in the modified β molecular sieve was determined by XRF. The sources of cations in Table 1 include ion-exchanged alkaline earth metals and Ce, as well as Na contained in NaY molecular sieve and Naβ molecular sieve. Specific types are shown in Table 1.
[0129] Table 1
[0130]
[0131] As can be seen from Table 1, although the specific surface area, micropore specific surface area, and pore volume of the modified β-zeolite provided by this invention are slightly lower than those of the unmodified comparative example 2, they are still at a relatively high level. The modified β-zeolite provided by this invention successfully exchanged the corresponding cations.
[0132] Test case
[0133] The CO2 adsorption capacity of the modified β molecular sieve, the Ru dispersion of the modified β molecular sieve, and the evaluation results of its use as a catalyst for ammonia decomposition to produce hydrogen are shown in Table 2.
[0134] The CO2 adsorption capacity of the modified β molecular sieve was obtained by CO2-TPD test;
[0135] The Ru dispersion of the modified β molecular sieve was determined by CO pulse adsorption.
[0136] Table 2
[0137] catalyst sample <![CDATA[CO2 adsorption capacity (mmol / g)]]> Ru dispersion (%) Ammonia conversion rate (500℃) Example 1 2.88 17.9 85.4％ Example 2 1.86 15.8 75.3％ Example 3 1.97 14.8 79.1％ Example 4 2.69 13.6 96.3％ Example 5 2.23 17.7 78.1％ Example 6 3.04 18.8 86.7％ Comparative Example 1 1.24 10.1 52.7％ Comparative Example 2 1.54 12.0 61.0％ Comparative Example 3 1.68 11.3 56.5％ Comparative Example 4 1.33 12.6 54.4％ Comparative Example 5 2.16 9.2 63.6％
[0138] As can be seen from Table 2, the modified β molecular sieve provided by the present invention has a higher ruthenium dispersion in the Sr and Ca modified catalyst examples.
[0139] Figure 1 The CO2-TPD diagrams of the various embodiments and comparative examples were obtained, in conjunction with... Figure 1 As can be seen from the data in Table 2, the basicity of the Sr, Ca and Ba modified β molecular sieves provided by this invention is significantly enhanced, which is much higher than that of unmodified molecular sieve catalysts or those modified with other metals.
[0140] Figure 2 For the XRD patterns of the various embodiments and comparative examples obtained, from Figure 2 As can be seen from the above, the modified β-zeolite catalyst provided by the present invention maintains the β-zeolite structure type very well.
[0141] Activity evaluation of ammonia decomposition for hydrogen production: The catalyst activity was evaluated using a fixed-bed flow-through reactor. The catalyst was reduced at 500℃ under a hydrogen atmosphere for 1 hour. The catalyst loading was 0.5 g, the reaction pressure was atmospheric pressure, the temperature range was 275-550℃, and the feed space velocity was 9000 mL NH3·g. cat-1 ·h -1 .
[0142] Ammonia conversion rate = (inlet ammonia flow rate - outlet ammonia flow rate) / inlet ammonia flow rate × 100%;
[0143] Using the modified molecular sieves prepared in the examples and comparative examples as catalysts, the ammonia conversion rate is as follows: Figure 3 As shown in Table 2, through Figure 3 As can be seen from Table 2, the catalyst in the examples has better catalytic activity, higher ammonia conversion rate, and a lower reaction temperature required to achieve the same ammonia conversion rate, thus enabling low-temperature and low-cost hydrogen production from ammonia.
[0144] At a temperature of 500℃ and a space velocity of 9000 mL / g, NH3·g cat -1 ·h -1 Under the conditions, a lifetime test was conducted on Example 1, and the results are as follows: Figure 4 As shown, through Figure 4 It can be seen that the catalyst prepared in Example 1 can still maintain a high level of ammonia conversion rate after long-term activity testing, showing excellent activity stability.
[0145] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A modified β-molecular sieve, characterized in that, The modified β-zeolite includes an alkaline earth metal β-zeolite and ruthenium supported on the alkaline earth metal β-zeolite; The modified β molecular sieve showed a CO2 adsorption capacity of 1.5-3.5 mmol / g as determined by CO2-TPD testing. After reduction at 500℃ for 1 hour in a hydrogen atmosphere, the Ru dispersion of the modified β molecular sieve was 12-20% according to CO pulse adsorption test.
2. The molecular sieve according to claim 1, wherein, The modified β molecular sieve exhibited a CO2 adsorption capacity of 1.86-3.04 mmol / g as determined by CO2-TPD testing. Preferably, after reduction at 500°C for 1 hour in a hydrogen atmosphere, the Ru dispersion of the modified β molecular sieve is 13.6-18.8% after CO pulse adsorption testing.
3. The molecular sieve according to claim 1 or 2, wherein, Based on the total amount of the modified β molecular sieve, the ruthenium content is 0.1-5% by weight, preferably 0.3-3% by weight; Preferably, the alkaline earth metal β-zeolite is obtained by β-zeolite through alkaline earth metal ion exchange; Preferably, the alkaline earth metal is selected from at least one of Ca, Sr, and Ba; Preferably, based on the total amount of the modified β molecular sieve, the content of alkaline earth metal elements is 1-10% by weight, preferably 5-10% by weight.
4. The molecular sieve according to any one of claims 1-3, wherein, The modified β molecular sieve has a specific surface area of 300-650 m². 2 / g, preferably 400-600m 2 / g; Preferably, the modified β-molecular sieve has a microporous specific surface area of 300-600 m². 2 / g, preferably 400-550m 2 / g; Preferably, the pore volume of the modified β-molecular sieve is 0.25-0.5 cm³. 3 / g, preferably 0.3-0.45cm 3 / g.
5. A method for preparing the modified β-zeolite according to any one of claims 1-4, characterized in that, The method includes: The modified β-zeolite is obtained by loading active metal ruthenium onto an alkaline earth metal β-zeolite.
6. The preparation method according to claim 5, wherein, The preparation method of the alkaline earth metal type β molecular sieve includes: mixing the β molecular sieve with a solution containing an alkaline earth metal source, performing ion exchange, separating the solid and liquid to obtain a solid product, and drying and calcining the solid product to obtain the alkaline earth metal type β molecular sieve. Preferably, the β-zeolite is a Na-type β-zeolite.
7. The preparation method according to claim 6, wherein, Based on a weight of 1g of β-molecular sieve, the molar amount of alkaline earth metal added to the solution containing the alkaline earth metal source is 0.001-0.1mol, preferably 0.005-0.02mol; Preferably, the molar concentration of the alkaline earth metal in the solution containing the alkaline earth metal source is 0.1-2 mol / L, more preferably 0.5-1.5 mol / L; Preferably, the alkaline earth metal is selected from at least one of Ca, Sr and Ba.
8. The preparation method according to claim 6 or 7, wherein, The ion exchange conditions include: a reaction temperature of 20-100℃, preferably 25-50℃; and a reaction time of 0.5-36h, preferably 4-30h. Preferably, the drying conditions include: a drying temperature of 100-140℃ and a drying time of 1-4 hours; Preferably, the roasting conditions include: a roasting temperature of 300-600℃, more preferably 450-550℃; and a roasting time of 2-8h, more preferably 3-5h.
9. The preparation method according to any one of claims 5-8, wherein, The amount of active metal ruthenium and alkaline earth metal type β molecular sieve used is such that, based on the total amount of the modified β molecular sieve obtained, the ruthenium content is 0.1-5% by weight, preferably 0.3-3% by weight.
10. The application of the modified β molecular sieve according to any one of claims 1-4 in the field of ammonia decomposition for hydrogen production.