Silicoaluminophosphate molecular sieve encapsulated intermetallic co- scr catalysts, their preparation and use

Abstract

The application discloses a kind of silicon-aluminum zeolite molecular sieve encapsulated intermetallic compound CO-SCR catalyst and its preparation method and application in CO-SCR denitration.The silicon-aluminum zeolite molecular sieve encapsulated intermetallic compound CO-SCR catalyst is synthesized by one-step hydrothermal method, comprising: adding soluble A metal compound and soluble B metal compound into the mixed solution of polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropyl alcohol and tetraethyl orthosilicate, then adding diethylamine, stirring for a period of time, then transferring to hydrothermal reaction kettle and hydrothermal reaction at 170-180 DEG C for 48-120 h, washing, drying the obtained hydrothermal product, and then calcining at 580-620 DEG C, followed by reduction in hydrogen atmosphere or hydrogen / inert gas mixed atmosphere at 400-600 DEG C, to obtain the silicon-aluminum zeolite molecular sieve encapsulated intermetallic compound CO-SCR catalyst; A metal is at least one of iridium, ruthenium and rhodium; B metal is at least one of rubidium, tin, zinc and samarium.

Description

Technical Field

[0001] This invention relates to the field of carbon monoxide selective catalytic reduction (CO-SCR) denitrification technology, specifically to an intermetallic compound CO-SCR catalyst encapsulated in aluminous atmosphere using silica-alumina zeolite molecular sieves, its preparation method, and its application. It is suitable for exhaust gases containing both carbon monoxide (CO) and nitrogen oxides (NOx). x Denitrification of flue gas. Background Technology

[0002] Nitrogen oxides (including nitric oxide NO and nitrogen dioxide NO2) are among the main pollutants causing air pollution. The large-scale emission of nitrogen oxides has caused a series of environmental problems, such as acid rain, ozone depletion, and photochemical smog.

[0003] Based on the source of nitrogen oxides, exhaust gases can be divided into industrial exhaust gases from stationary sources and vehicle exhaust gases from mobile sources. Selective catalytic reduction (SCR) is one of the most widely used denitrification technologies. In the thermal power generation industry, a common denitrification technology uses liquid ammonia or ammonia gas (NH3) as a reducing agent, where a selective catalytic reduction reaction occurs under the action of a vanadium-tungsten-titanium or vanadium-molybdenum-titanium (V2O5-WO3(MoO3) / TiO2) catalyst to achieve denitrification. This technology is currently a commercially available denitrification technology widely used in stationary sources such as coal-fired power plants, industrial boilers, and kilns. However, due to the use of NH3 as a reducing agent, this process has high operating costs. Furthermore, at low temperatures, ammonia reacts with sulfur dioxide (SO2) and other components in the flue gas to produce salts, clogging the catalyst pores and the catalyst bed. In addition, unreacted ammonia also poses a significant threat to the surrounding environment.

[0004] Coke oven gas, sintering gas, and boiler gas typically contain both nitrogen oxides and a large amount of carbon monoxide (CO) produced by incomplete combustion. If CO and NO could be combined... x The reaction occurs under the action of a catalyst, resulting in the reaction of CO and NO. x Simultaneous removal of CO can significantly reduce the investment and operating costs of denitrification. Therefore, selective catalytic reduction of carbon monoxide (CO-SCR) technology is an ideal denitrification technology for CO-containing flue gas such as coke oven gas, sintering gas, and boiler gas.

[0005] Current research on CO-SCR reactions is mostly conducted under anaerobic conditions, which are not applicable to real flue gas environments. Because in real flue gas conditions, the O2 content is typically around 5 vol%, CO is easily oxidized to CO2 at relatively low temperatures, making it difficult to react with NO. xMatching the reaction temperature of catalytic reduction with the actual reaction temperature results in very low denitrification efficiency of the catalyst. Only a few noble metal catalysts exhibit denitrification activity in the presence of small amounts of oxygen (Ji et al., Adv. Mater. 2022, 34, 2205703; Jie et al., ACS Catal. 2023, 13, 224-236). Currently, the selection of catalysts available under oxygen-enriched conditions remains very limited.

[0006] Chinese patent application CN202110587825.8 discloses a method for the selective catalytic reduction of NO by CO. x The SiO2 sphere-supported iridium-potassium bimetallic catalyst is prepared using a traditional impregnation method. Specifically, SiO2 spheres are first prepared, and then potassium carbonate (potassium chloride or potassium nitrate) and iridium trichloride are sequentially impregnated. In this catalyst system, intermetallic compounds cannot form between the promoter potassium and the active component iridium. Both the promoter potassium and the active component iridium are supported on the surface of the SiO2 spheres, and there is no confinement effect of the SiO2 spheres on the promoter potassium and the active component iridium. Summary of the Invention

[0007] This invention provides an intermetallic compound CO-SCR catalyst encapsulated in aluminosilicate zeolite molecular sieves for use in aerobic atmospheres, along with its preparation method and applications. The catalyst can be obtained through a one-step hydrothermal synthesis, using an intermetallic compound composed of metals A and B as the active material. Metal A is at least one of ruthenium (Ru), rhodium (Rh), and iridium (Ir), and metal B is at least one of rubidium (Rb), tin (Sn), zinc (Zn), and samarium (Sm). The support is aluminosilicate zeolite molecular sieve. This catalyst exhibits excellent CO-SCR denitrification activity under real flue gas conditions, providing strong catalytic support for the denitrification treatment of flue gas containing large amounts of CO, such as coke oven gas and sintering gas, and has promising application prospects.

[0008] The specific technical solution is as follows:

[0009] A method for preparing an intermetallic compound CO-SCR catalyst encapsulated in a silica-alumina zeolite molecular sieve is disclosed. The method involves a one-step hydrothermal synthesis of the catalyst, specifically comprising: adding a soluble metal A compound and a soluble metal B compound to a mixed solution of polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropoxide, and tetraethyl silicate; then adding diethylamine; stirring for a period of time; transferring the mixture to a hydrothermal reactor; and reacting the mixture at 170–180°C for 48–120 h; washing and drying the resulting hydrothermal product; calcining the product at 580–620°C; and then reducing the product at 400–600°C in a hydrogen atmosphere or a hydrogen / inert gas mixed atmosphere to obtain the silica-alumina zeolite molecular sieve encapsulated intermetallic compound CO-SCR catalyst.

[0010] Metal A is at least one of iridium, ruthenium, and rhodium;

[0011] Metal B is at least one of rubidium, tin, zinc, and samarium.

[0012] This invention reveals that diethylamine can coordinate with various metal cations and, through hydrothermal synthesis, encapsulate the metals within the framework channels of a molecular sieve. Subsequent calcination and high-temperature reduction treatment allow noble metal A to form stable intermetallic compounds with auxiliary metal B. This preparation method achieves a high degree of dispersion of the active phase within the support structure, effectively improving the unit utilization efficiency of the noble metal (at least one of Ru, Rh, and Ir) and enhancing its adsorption capacity and redox ability for the reaction medium.

[0013] Furthermore, this invention utilizes a one-step hydrothermal synthesis of silica-alumina molecular sieves to encapsulate intermetallic compound nanoclusters within the molecular sieve channels. This allows the confinement effect of the molecular sieve channels to effectively suppress the agglomeration and particle size increase of metal particles during reduction and use, thereby effectively enhancing the activity and long-term thermal stability of the active phase.

[0014] In one embodiment, the preparation method of the intermetallic compound CO-SCR catalyst encapsulated by the silica-alumina zeolite molecular sieve involves a mass ratio of polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropoxide, tetraethyl silicate, soluble metal A compound, soluble metal B compound, and diethylamine of 10–200:100–750:1–200:100–450:0.5–2:0.1–50:1–100.

[0015] In one embodiment, the method for preparing the intermetallic compound CO-SCR catalyst encapsulated in the silica-alumina zeolite molecular sieve involves drying at a temperature of 100–120°C for 8–24 hours.

[0016] In one embodiment, the preparation method of the intermetallic compound CO-SCR catalyst encapsulated in the silica-alumina zeolite molecular sieve includes a calcination time of 3 to 10 hours.

[0017] In one embodiment, in the method for preparing the intermetallic compound CO-SCR catalyst encapsulated by the silica-alumina zeolite molecular sieve, the hydrogen volume ratio in the hydrogen / inert gas mixed atmosphere is 5% to 20%.

[0018] In one embodiment, the method for preparing the intermetallic compound CO-SCR catalyst encapsulated in the silica-alumina zeolite molecular sieve, wherein the inert gas is a rare gas and / or nitrogen.

[0019] In one embodiment, the reduction time for the method of preparing the intermetallic compound CO-SCR catalyst encapsulated in the silica-alumina zeolite molecular sieve is 1 to 4 hours.

[0020] This invention further provides an intermetallic compound CO-SCR catalyst encapsulated in silica-alumina zeolite molecular sieve prepared by the aforementioned method.

[0021] The present invention also provides the application of the intermetallic compound CO-SCR catalyst encapsulated in silica-alumina zeolite molecular sieve in CO-SCR denitrification.

[0022] As a general inventive concept, this invention also provides a CO-SCR denitrification method, which uses an intermetallic compound CO-SCR catalyst encapsulated in the aforementioned silica-alumina zeolite molecular sieve to treat waste gas containing CO and nitrogen oxides, with a treatment temperature of 240–360°C.

[0023] In one embodiment, the CO-SCR denitrification method may further include oxygen in the exhaust gas.

[0024] In one embodiment, in the CO-SCR denitrification method, the amount of the intermetallic compound CO-SCR catalyst encapsulated in silica-alumina zeolite molecular sieve can be 2000–80000 h⁻¹. -1 .

[0025] Compared with the prior art, the beneficial effects of this invention are as follows:

[0026] (1) The active phase of the catalyst of the present invention is to form an intermetallic compound by using diethylamine to anchor a specific noble metal A and an auxiliary metal B. Through the form of an intermetallic compound, the amount of noble metal used can be reduced to the greatest extent, thereby reducing the production cost of the catalyst.

[0027] (2) The present invention generates a confinement effect on the intermetallic compound clusters in the channels by loading the silica-alumina zeolite molecular sieve, which strongly inhibits the growth of active phase clusters in long-term heating processes (including catalyst preparation process and denitrification application process), thereby maintaining the long-term stability of the catalyst.

[0028] (3) The intermetallic compound of the catalyst of the present invention is encapsulated in the molecular sieve channel, which can maximize the utilization of the active center.

[0029] In summary, this invention utilizes diethylamine to combine a specific noble metal A and an auxiliary metal B to form an intermetallic compound, and then uses a one-step hydrothermal synthesis method to anchor and encapsulate the intermetallic compound composed of metals A and B within the framework channels of a silica-alumina zeolite molecular sieve. The catalyst of this invention exhibits excellent CO-SCR denitrification activity and long-term stability under real flue gas conditions. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0031] The performance testing conditions for the catalysts prepared in the following examples and comparative examples are as follows:

[0032] The catalyst was placed in a fixed-bed quartz tube reactor for activity testing at a reaction temperature of 240–360 °C, an NO inlet concentration of 600 ppm, a CO inlet concentration of 3000 ppm, an oxygen content of 5 vol%, and a space velocity of 40,000 h⁻¹. -1 The rest is nitrogen.

[0033] Example 1

[0034] Preparation of Ir-Rb@silica-aluminate zeolite molecular sieve catalyst: First, prepare 20 mL of a solution containing 0.06 g iridium (added as chloroiridium hydrate) and 0.08 g rubidium (added as rubidium nitrate); then add 10.0 g polyethylene glycol, 22.5 g tetrapropylammonium hydroxide, 0.4 g aluminum isopropoxide, and 6.0 g tetraethyl silicate to 30 mL of deionized water and stir for 6 h; under stirring, add the prepared 20 mL solution containing 0.06 g iridium and 0.08 g rubidium; then add 4 mL of diethylamine and continue stirring. Stir for 3 hours; finally, the stirred sample is placed in a hydrothermal reactor and hydrothermally heated at 175℃ for 48 hours; after hydrothermal treatment, the sample is washed three times each with ethanol and water, and dried in an oven at 100℃ for 8 hours; then the dried sample is calcined at 600℃ for 3 hours, and finally the calcined sample is reduced in a 10 vol% H2 / N2 mixed gas at 400℃ for 1 hour to obtain the final Ir-Rb@silica-alumina zeolite molecular sieve catalyst, namely, the intermetallic compound CO-SCR catalyst encapsulated in silica-alumina zeolite molecular sieve.

[0035] XRF testing revealed that the catalyst in this embodiment contained 0.56 wt% Ir and 0.75 wt% Rb. The catalyst achieved its highest denitrification efficiency of 85.2% at 270°C. Stability testing at 270°C showed that the catalyst's denitrification activity remained above 80.0% throughout a continuous 24-hour test.

[0036] Comparative Example 1

[0037] Preparation of Ir@silica-alumina zeolite molecular sieve catalyst: The only difference from Example 1 is that the first step was to prepare 20 mL of a solution containing only 0.06 g of iridium (added via chloroiridium acid hydrate) and no rubidium nitrate. Subsequent additions were also made using the same 20 mL solution containing only 0.06 g of iridium (added via chloroiridium acid hydrate) and no rubidium nitrate. All other steps were the same, resulting in the Ir@silica-alumina zeolite molecular sieve catalyst. This catalyst achieved its highest denitrification efficiency of 50.4% at 270 °C.

[0038] Comparative Example 2

[0039] Preparation of Ir-Rb / silica-alumina zeolite molecular sieve catalyst: 10.0 g polyethylene glycol, 22.5 g tetrapropylammonium hydroxide, 0.4 g aluminum isopropoxide, and 6.0 g tetraethyl silicate were added to 30 mL of deionized water and stirred for 6 h; the sample after stirring was placed in a hydrothermal reactor and hydrothermally heated at 175 °C for 48 h; the sample after hydrothermal treatment was washed three times each with ethanol and water; and then dried at 100 °C for 8 h and calcined at 600 °C for 3 h to obtain silica-alumina zeolite molecular sieve. 5.0 g of the prepared zeolite molecular sieve was added to 50 mL of deionized water and stirred. Then, a solution containing 0.03 g of iridium in chloroiridium acid and 0.04 g of rubidium in rubidium nitrate was added and stirred for 4 hours. The sample was then dried in an oven at 100 °C for 8 hours. After that, the dried sample was calcined at 600 °C for 3 hours. Finally, the calcined sample was reduced in a 10 vol% H2 / N2 mixed gas at 400 °C for 1 hour to obtain the final Ir-Rb / silica-aluminate zeolite molecular sieve catalyst.

[0040] XRF testing revealed that the Ir content in this comparative catalyst was 0.55% and the Rb content was 0.80%. The catalyst achieved its highest denitrification efficiency of 65.5% at 270℃.

[0041] Comparative Example 3

[0042] The only difference from Example 1 was the absence of diethylamine; all other aspects remained the same. The resulting catalyst achieved its highest denitrification efficiency of 40.3% at 250°C. The comparison of denitrification efficiency between Comparative Example 3 and Example 1 demonstrates that combining diethylamine with metal ions during metal encapsulation is necessary to enhance the denitrification activity of the catalyst.

[0043] Example 2

[0044] Preparation of Ru-Sn@silica-alumina zeolite molecular sieve catalyst: The only difference from Example 1 is that 10 mL of ruthenium trichloride aqueous solution containing 0.08 g ruthenium and 10 mL of stannous chloride solution containing 0.12 g tin were prepared first, and subsequently, the same 10 mL of ruthenium trichloride aqueous solution and stannous chloride solution containing 0.12 g tin were added. All other steps were the same, resulting in the Ru-Sn@silica-alumina zeolite molecular sieve catalyst. This catalyst achieved its highest denitrification efficiency of 82.7% at 260 °C.

[0045] Example 3

[0046] Preparation of Rh-Zn@silica-alumina zeolite molecular sieve catalyst: The only difference from Example 1 is that 10 mL of a rhodium nitrate aqueous solution containing 0.1 g rhodium and 10 mL of a zinc nitrate solution containing 1.20 g zinc were prepared first. Subsequently, the same 10 mL of the prepared rhodium nitrate aqueous solution and 10 mL of the zinc nitrate solution containing 1.20 g zinc were added. All other steps were the same, resulting in the Rh-Zn@silica-alumina zeolite molecular sieve catalyst. This catalyst achieved its highest denitrification efficiency of 88.9% at 260 °C.

[0047] Example 4

[0048] Preparation of Ir-Sm@silica-alumina zeolite molecular sieve catalyst: The only difference from Example 1 is that 10 mL of a chloroiridium hydrate solution containing 0.1 g iridium and 10 mL of a samarium nitrate solution containing 2.50 g samarium were prepared first, and subsequently, the same 10 mL solutions were added. All other steps were the same, resulting in the Ir-Sm@silica-alumina zeolite molecular sieve catalyst. This catalyst achieved its highest denitrification efficiency of 90.5% at 270 °C.

[0049] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. The application of an intermetallic compound CO-SCR catalyst encapsulated in a silica-alumina zeolite molecular sieve in CO-SCR denitrification, characterized in that, The preparation method of the intermetallic compound CO-SCR catalyst encapsulated by the silica-alumina zeolite molecular sieve adopts a one-step hydrothermal method to synthesize the intermetallic compound CO-SCR catalyst encapsulated by the silica-alumina zeolite molecular sieve. Specifically, it includes: adding soluble metal A compound and soluble metal B compound to a mixed solution of polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropoxide and tetraethyl silicate, then adding diethylamine, stirring for a period of time, transferring to a hydrothermal reactor and hydrothermally reacting at 170~180℃ for 48~120 h, washing and drying the obtained hydrothermal product, calcining it at 580~620℃, and then reducing it at 400~600℃ in a hydrogen atmosphere or a hydrogen / inert gas mixed atmosphere to obtain the intermetallic compound CO-SCR catalyst encapsulated by the silica-alumina zeolite molecular sieve. Metal A is at least one of iridium, ruthenium, and rhodium; Metal B is at least one of rubidium, tin, zinc, and samarium; When metal A is iridium, metal B is rubidium or samarium; when metal A is ruthenium, metal B is tin; when metal A is rhodium, metal B is Zn. The mass ratio of polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropoxide, tetraethyl silicate, soluble metal A compound, soluble metal B compound, and diethylamine is 10~200:100~750:1~200:100~450:0.5~2:0.1~50:1~100.

2. The application according to claim 1, characterized in that, The drying temperature is 100~120℃, and the time is 8~24h.

3. The application according to claim 1, characterized in that, The calcination time is 3 to 10 hours.

4. The application according to claim 1, characterized in that, The hydrogen / inert gas mixture has a hydrogen volume percentage of 5% to 20%. The inert gas is a rare gas and / or nitrogen.

5. The application according to claim 1, characterized in that, The reduction time is 1 to 4 hours.

6. A CO-SCR denitrification method, characterized in that, A CO-SCR catalyst encapsulated in silica-alumina zeolite molecular sieve is used to treat waste gas containing CO and nitrogen oxides at a temperature of 240~360℃. The preparation method of the intermetallic compound CO-SCR catalyst encapsulated by the silica-alumina zeolite molecular sieve adopts a one-step hydrothermal method to synthesize the intermetallic compound CO-SCR catalyst encapsulated by the silica-alumina zeolite molecular sieve. Specifically, it includes: adding soluble metal A compound and soluble metal B compound to a mixed solution of polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropoxide and tetraethyl silicate, then adding diethylamine, stirring for a period of time, transferring to a hydrothermal reactor and hydrothermally reacting at 170~180℃ for 48~120h, washing and drying the obtained hydrothermal product, calcining it at 580~620℃, and then reducing it at 400~600℃ in a hydrogen atmosphere or a hydrogen / inert gas mixed atmosphere to obtain the intermetallic compound CO-SCR catalyst encapsulated by the silica-alumina zeolite molecular sieve. Metal A is at least one of iridium, ruthenium, and rhodium; Metal B is at least one of rubidium, tin, zinc, and samarium; When metal A is iridium, metal B is rubidium or samarium; when metal A is ruthenium, metal B is tin; when metal A is rhodium, metal B is Zn. The mass ratio of polyethylene glycol, tetrapropylammonium hydroxide, aluminum isopropoxide, tetraethyl silicate, soluble metal A compound, soluble metal B compound, and diethylamine is 10~200:100~750:1~200:100~450:0.5~2:0.1~50:1~100.

7. The CO-SCR denitrification method according to claim 6, characterized in that, The exhaust gas also contains oxygen; The amount of the intermetallic compound CO-SCR catalyst encapsulated in the silica-alumina zeolite molecular sieve is 2000~80000 h⁻¹. -1 .