A composite oxide powder for high-temperature direct degradation of nitrogen oxides and a method for preparing the same

Abstract

The application discloses a kind of high-temperature direct degradation nitrogen oxide composite oxide powder and preparation method thereof.A kind of high-temperature direct degradation nitrogen oxide composite oxide powder, by 55%‑99% of rare earth metal element oxide and 1%‑45% of other element oxide with mass fraction, rare earth metal element is selected from one or more of terbium, praseodymium, dysprosium, cerium, samarium, yttrium, lanthanum, neodymium and gadolinium, other elements are selected from one or more of aluminum, zirconium, barium, magnesium, silicon and copper.The composite rare earth oxide powder functional material proposed in the application is directly applied to combustion high-temperature environment, nitrogen oxide in high-temperature flue gas is directly degraded into nitrogen and oxygen on the surface of functional material, and the purpose of reducing industrial combustion nitrogen oxide emission at source can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial atmospheric pollutant treatment, in particular to a composite oxide powder for high-temperature direct degradation of nitrogen oxides and a preparation method thereof. BACKGROUND

[0002] Nitrogen oxides (NOx) are one of the main atmospheric pollutants, mainly from industrial combustion and motor vehicle exhaust emissions. The nitrogen oxides emitted by industrial combustion are mainly thermal NOx, and the main factors affecting the generation of thermal NOx are reaction temperature and oxygen concentration in the reaction process. Researchers at home and abroad have successively proposed low-NOx combustion technologies such as staged combustion, dense and thin combustion, premixed combustion, and exhaust gas recirculation, the core technologies of which are to reduce the temperature of the main combustion zone or the oxygen concentration in the main combustion zone, shorten the residence time of oxygen in the high-temperature zone, or reduce NOx in the exhaust gas. However, these technologies have problems such as increased generation of soot and CO, poor combustion efficiency, and the like, which need to be overcome in practical application; post-combustion treatment mainly includes SCR and SNCR ammonia injection denitration treatment technologies, which have high NOx removal efficiency, but require large flue gas denitration treatment equipment, high initial investment, high operating and labor costs, and also have problems such as ammonia escape and catalyst poisoning in operation.

[0003] Recent research has found that composite rare earth oxides have high conversion efficiency in degrading NOx emitted by motor vehicle exhaust, and the most studied are noble metals, perovskite oxides, molecular sieve catalysts, and other rare earth oxides. Japanese scholar Imanaka et al. found that Gd2Y2BaO 11 , Tb4Yb2O 10 , Tb4Y2BaO 11 , Y2Pr6Eu2O 17 , etc. have high decomposition activity of NO at high temperature; shihara et al. found that Ba / BaY2O4, Ba / Y2O3, and Ba3Y 3.4 Sc 0.6 O9 systems have NO decomposition activity of 50% to 90%; Tatsumi et al. found that the decomposition efficiency of Y2O3-BaO-Ni composite system for NO in a He atmosphere can reach 95% at 1123K. Since more than 90% of the nitrogen oxides emitted by industrial combustion are nitric oxide NO, composite rare earth oxide materials have potential application value in industrial source nitrogen oxide emission reduction. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a composite oxide powder for directly degrading nitrogen oxides at high temperature and a preparation method thereof. The composite rare earth oxide functional material is directly applied to a high-temperature combustion environment. Nitrogen oxides in flue gas at a temperature above 800 DEG C are directly degraded into nitrogen and oxygen on the surface of the functional material, so that the purpose of reducing the emission of nitrogen oxides in industrial combustion at the source can be achieved.

[0005] The present application aims to provide a composite oxide powder for directly degrading nitrogen oxides at high temperature, which is composed of 55%-99% of rare earth metal element oxides and 1%-45% of other element oxides in terms of mass fraction. The rare earth metal elements are selected from one or more of terbium (Tb), praseodymium (Pr), dysprosium (Dy), cerium (Ce), samarium (Sm), yttrium (Y), lanthanum (La), neodymium (Nd) and gadolinium (Gd). The other elements are selected from one or more of aluminum (Al), zirconium (Zr), barium (Ba), magnesium (Mg), silicon (Si) and copper (Cu).

[0006] The composite oxide powder provided by the present application is mainly composed of one or more of rare earth metal element oxides (Tb4O7, Pr6O 11 , Dy2O3, CeO2, Sm2O3, Y2O3, La2O3, Nd2O3 and Gd2O3), and one or more of other element oxides (Al2O3, ZrO2, BaO, MgO, SiO and CuO). The original structure of the composite oxide is distorted to form a composite oxide with high-temperature decomposition characteristics for NO. The specific surface area (BET) of the composite oxide powder material is 28-38 m 2 / g, and the material has a special network pore structure.

[0007] Preferably, 2%-42% of the other element oxides are introduced into 58%-98% of the rare earth metal element oxides in terms of mass fraction, so that the structure of the mixture is distorted to form a composite oxide with high-temperature decomposition characteristics for NO.

[0008] Preferably, the mass ratio of the rare earth metal element oxides to the other element oxides is 8:2-6:4. The rare earth metal element oxides are cerium oxide and yttrium oxide. The other element oxides are zirconium oxide and barium oxide. The mass ratio of the cerium oxide to the yttrium oxide is 8:2-6:4. The mass ratio of the zirconium oxide to the barium oxide is 6:4-5:5.

[0009] Preferably, the mass ratio of the rare earth metal element oxides to the other element oxides is 8:2-6:4. The rare earth metal element oxides are samarium oxide and yttrium oxide. The other element oxides are zirconium oxide and barium oxide. The mass ratio of the samarium oxide to the yttrium oxide is 8:2-6:4. The mass ratio of the zirconium oxide to the barium oxide is 6:4-5:5.

[0010] Another object of the present application is to protect the preparation method of the composite oxide powder for directly degrading nitrogen oxides at high temperature, comprising the following steps:

[0011] (1) Using one or more than one nitrate hydrate containing rare earth metal elements terbium (Tb), praseodymium (Pr), dysprosium (Dy), cerium (Ce), samarium (Sm), yttrium (Y), lanthanum (La), neodymium (Nd) and gadolinium (Gd) as raw materials, mixing with one or more than one nitrate hydrate or nitrate of other elements (Al), zirconium (Zr), barium (Ba), magnesium (Mg), silicon (Si) and copper (Cu), adding glycine solution with a concentration of 0.09-0.16 g / mL, stirring until the solute is dissolved to obtain a precursor solution;

[0012] (2) drying the precursor solution to obtain a precursor solid, heating the precursor solid at 400-600°C for 25-35 minutes to obtain a raw material powder by glycine self-propagating combustion method;

[0013] (3) calcining the raw material powder at 600-1000°C for 2-4 hours, and then grinding to obtain the composite oxide powder.

[0014] Preferably, the ratio of the sum of the amounts of substance of the rare earth metal elements and other elements in the precursor solution of step (1) to the amount of substance of glycine is 1:1.05-1.3.

[0015] Preferably, the drying temperature of step (2) is 80-90°C.

[0016] Preferably, the precursor solid of step (2) is heated at 500°C for 30 minutes.

[0017] Preferably, the particle size of the composite oxide powder after grinding of step (3) is between 10-100 nm. The specific surface area (BET) of the composite oxide powder material is 28-38 m 2 / g, with a special network pore structure.

[0018] The present application also protects the application of the composite oxide powder for directly degrading nitrogen oxides at high temperature in degrading nitrogen oxides in a high-temperature environment above 800°C.

[0019] Compared with the prior art, the composite rare earth oxide powder functional material proposed by the present application has the following advantages: the composite rare earth oxide powder functional material is directly applied to a high-temperature combustion environment, and the nitrogen oxides in high-temperature flue gas are directly degraded into nitrogen and oxygen on the surface of the functional material, which can achieve the purpose of reducing industrial combustion nitrogen oxide emissions at the source. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1is a SEM image of the rare earth complex metal oxide catalyst obtained in Example 1.

[0021] Figure 2 is a NO degradation efficiency characteristic of the powder material obtained in Example 2 under different oxygen partial pressures. DETAILED DESCRIPTION

[0022] The following examples are further illustrations of the application and are not intended to limit the same.

[0023] The objectives, technical solutions, and advantages of the present application will become more apparent after a reading of the following detailed description together with the attached drawings. It is obvious that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The following description of at least one example is merely illustrative in nature and is in no way intended to limit the application or its application or uses. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0024] Example 1

[0025] In a beaker, 48.22 g of Ce(N03)3-6H20, 40.26 g of Y(N03)3-6H20, 3.14 g of Zr(N03)4-5H20, and 5.10 g of Ba(N03)2 were added, 350 mL of deionized water, 31.81 g of glycine, a magnetic rotor, and a magnetic stirrer speed setting of 60 r / min were added, and the heating temperature was set to 80°C. The solution was fully stirred on the magnetic stirrer until the solute was completely dissolved, and a viscous precursor solution was obtained. The precursor solution was moved to a 500 mL beaker, and the beaker was placed in a 90°C drying oven to evaporate the water. The dried beaker was placed on an electric heating furnace, an isolation hood and a powder collector were placed on top of the beaker, the electric heating furnace temperature was set to 500°C, and after heating for 30 minutes, the precursor solid reached the ignition temperature and started to self-propagating combustion. The products produced by combustion were collected by the powder collector to obtain the raw material powder. The collected raw material powder was placed in a quartz boat, which was placed in a 600°C muffle furnace for calcination for 2 hours, and after grinding, the prepared composite oxide powder for high-temperature direct degradation of nitrogen oxides (Ce02-Y203-Zr02-BaO) was obtained.

[0026] The scanning electron microscope image of the composite oxide powder material is shown in Figure 1 , which has a special network pore structure, and the specific surface area (BET) is 31.3 m 2 / g.

[0027] Comparative Example 1

[0028] The same as example 1, except that 23.45 g Ce(NO3)3, 19.46 g Y(NO3)3, 1.24 g ZrOCl2 and 2.10 g Ba(NO3)2 were put into a 500 mL beaker, 300 mL deionized water was added into the beaker, a magnetic rotor was used, the speed of the magnetic stirrer was set to 80 r / min, the mixed solution was moved into a burette after being fully stirred until the solute was completely dissolved, 150 mL ammonia water was dropped into the mixed solution at a speed of 0.5 mL / min, the mixed solution after titration was filtered by a vacuum filter, the precipitate was washed with deionized water for 3 times to remove Cl-ions, the precipitate was washed with n-butanol for 2 times to remove water, the precipitate was dried at room temperature, and then was calcined at 600℃ and 1250℃ for 0.5 hour and 8 hours respectively, the powder after calcination and grinding was prepared by coprecipitation, i.e. the prepared composite oxide powder for high-temperature direct degradation of nitrogen oxides (CeO2-Y2O3-ZrO2-BaO) was obtained, and the specific surface area (BET) of the powder was measured by N2 adsorption BET method to be between 9.7-16.7 m2 / g. 2 / g.

[0029] Example 2

[0030] In beaker A, 102.52 g Sm(NO3)3·6H2O, 43.5 g Y(NO3)3·6H2O and 5.24 g Zr(NO3)4·5H2O were added, 350 mL deionized water was added, a magnetic rotor was used, the speed of the magnetic stirrer was set to 60 r / min, the solution was fully stirred on the magnetic stirrer until the solute was completely dissolved, 8.50 g Ba(NO3)2 was accurately weighed by a balance and put into a 500 mL beaker B, 100 mL deionized water was added, a glass rod was used to stir until it was completely dissolved, the solution in beaker A was poured into beaker B, and the heating temperature of the magnetic stirrer was set to 80℃, and the solution was stirred until it became a viscous precursor solution. Beaker B was placed in a 90℃ drying oven to evaporate water, and a precursor solid was obtained; the dried beaker was placed on an electric heating furnace, a separation hood and a powder collector were placed on the top of the beaker, the temperature of the electric heating furnace was set to 500℃, and after heating for 30 minutes, the precursor solid reached the ignition temperature and started the self-propagating combustion, the product generated by the combustion was collected by the powder collector to obtain a raw material powder. The collected raw material powder was placed in a quartz boat, the quartz boat was placed in a 600℃ muffle furnace and calcined for 2 hours, and after grinding, the prepared composite oxide powder for high-temperature direct degradation of nitrogen oxides was obtained.

[0031] 1 g of the prepared composite oxide powder was taken and placed in a quartz glass tube, the quartz glass tube was placed in an electric heating furnace, and a 1% volume concentration of NO was introduced into the quartz tube, Ar was used as the balance gas, the inlet flow rate was 20 mL / min, and the ratio of catalyst mass to gas flow rate W / F was 3.0 g·s·cm-3 The experimental temperature was 600-1100°C. After the material was decomposed, the concentration of NO in the flue gas was detected by a flue gas analyzer. The results are shown in Table 1. Figure 2 As shown in Table 1, the results show that the decomposition efficiency of the oxide powder prepared under different oxygen atmospheres for NO is about 40% at 750°C, and the maximum decomposition efficiency is 92% at 1100°C.

[0032] The above examples are only used to help understand the technical solutions of the present application and its core idea. It should be pointed out that for those skilled in the art, without departing from the principles of the present application, the present application can be improved and modified in several ways, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. Use of a composite oxide powder for high-temperature direct decomposition of nitrogen oxides for the decomposition of nitrogen oxides in a high-temperature environment above 800°C, characterized in that, The high-temperature direct degradation of nitrogen oxide composite oxide powder is a rare earth metal element oxide with other element oxides, which makes the mixture structure lattice distortion to form a composite oxide with high-temperature decomposition characteristics of NO, and the mass ratio of the rare earth metal element oxide and the other element oxide is 8:2-6:4, the rare earth metal element is selected from one or more of terbium, praseodymium, dysprosium, cerium, samarium, yttrium, lanthanum and neodymium, and the other element is selected from one or more of zirconium, barium, magnesium, silicon and copper, the particle size of the composite oxide powder is between 10-100 nm, and the specific surface area of the composite oxide powder material is 28-38 m 2 / g, with a special network pore structure. The preparation method of the composite oxide powder for high-temperature direct degradation of nitrogen oxides comprises the following steps: (1) taking one or more than one nitrate hydrate containing rare earth metal elements terbium, praseodymium, dysprosium, cerium, samarium, yttrium, lanthanum and neodymium as raw materials, mixing with one or more than one nitrate hydrate or nitrate of other elements zirconium, barium, magnesium, silicon and copper, adding glycine solution, stirring until the solute is dissolved to obtain a precursor solution; (2) drying the precursor solution to obtain a precursor solid, heating the precursor solid at 400-600 DEG C for 25-35 minutes to obtain a raw material powder by glycine self-propagating combustion method; (3) calcining the raw material powder at 600-1000 DEG C for 2-4 hours, and then grinding to obtain the composite oxide powder.

2. Use according to claim 1, characterized in that, In step (1), the ratio of the sum of the amounts of substance of rare earth metal elements and other elements in the precursor solution to the amount of substance of glycine is 1:1.05-1.

3.

3. Use according to claim 1, characterized in that, In step (2), the drying temperature is 80-90 DEG C.

4. Use according to claim 1, characterized in that, In step (2), the precursor solid is heated at 500 DEG C for 30 minutes.

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