Phosphorus-gallium modified copper-based molecular sieve waste gas purification functional material and its preparation method and application

Abstract

The invention discloses a phosphorus-gallium modified copper-based molecular sieve waste gas purification functional material and a preparation method and application thereof. The material comprises the following steps: stirring and impregnating ZSM-5 in a mixed solution of NaOH and Ga(NO3)3; after the impregnation is completed, washing and drying to obtain Na-Ga-ZSM-5; adding Na-Ga-ZSM-5 to an NH4Cl solution and stirring in a water bath to obtain NH4-Ga-ZSM-5; adding NH4-Ga-ZSM-5 to an NH4H2PO4 solution, first stirring at room temperature, then heating and stirring until dry, and then calcining to obtain P-Ga-ZSM-5; adding P-Ga-ZSM-5 to a Cu(NO3)2 solution, adjusting the pH value of the solution to 4.5-5.5, stirring for 20-30 hours, washing, drying, and calcining to obtain P-Ga / Cu-ZSM-5.

Description

Technical Field

[0001] The present invention belongs to the technical field of denitration catalysts, and specifically relates to a phosphorus-gallium modified copper-based molecular sieve waste gas purification functional material, a preparation method and an application thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In recent years, with increasing attention paid to nitrogen oxide pollution and the introduction and implementation of relevant laws and regulations, my country's nitrogen oxide emission standards have become increasingly stringent. NH3-SCR (ammonia selective catalytic reduction) is one of the most mature and effective technologies for flue gas / exhaust nitrogen oxide purification. The SCR denitrification catalyst is the core component of the NH3-SCR system. Its performance directly affects the overall denitrification efficiency and stability of the system and is crucial to the success of denitrification projects. Based on pollution source classification, nitrogen oxides can be divided into stationary and mobile source emissions. The rapid development of the domestic economy has led to a significant increase in the number of motor vehicles, resulting in a year-on-year increase in the proportion of mobile source nitrogen oxide emissions, making it the primary source of air pollution in large and medium-sized cities.

[0004] Compared with fixed sources, the operating conditions of mobile sources are more complex and changeable. Molecular sieve catalysts (such as Cu-SSZ-13, Cu-ZSM-5) are currently attracting widespread attention in the field of mobile source denitrification due to their ordered pore structure, abundant acidic sites, wide temperature window and efficient redox ability. In actual working conditions, affected by the working state and driving conditions, the exhaust temperature may drop below 250°C. At this time, the activity of the molecular sieve catalyst will decrease rapidly. Doping with active components is a commonly used means to broaden the catalyst temperature window and enhance activity. However, on the one hand, water, as an important component in mobile source exhaust gas, for example, the water vapor content in gasoline vehicles is about 10%, which will solvate the active components in the molecular sieve framework, resulting in higher mobility and mobility, thereby reducing the stability of the catalyst; on the other hand, toxic gases such as SO2 generated in the exhaust gas will poison and inactivate the catalyst. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material and its preparation method and application. The catalyst prepared has good low-temperature activity and stability, which can effectively improve the removal of NO by mobile source NH3-SCR. x efficiency.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material, comprising the following steps:

[0008] ZSM-5 is stirred and impregnated in a mixed solution of NaOH and Ga(NO3)3 at a temperature of 60-80°C for 1-1.5 hours. In the mixed solution, the mass ratio of solute to water is 0.008-0.01:1, and the mass ratio of NaOH to Ga(NO3)3 is 1.2-1.5:1. After impregnation, the mixture is washed and dried to obtain Na-Ga-ZSM-5.

[0009] Add Na-Ga-ZSM-5 to NH4Cl solution and stir in a water bath. The concentration of NH4Cl solution is 0.022-0.027 g / L. The stirring temperature of the water bath is 70-90°C. The stirring time is 1-1.5 h to obtain NH4-Ga-ZSM-5.

[0010] Add NH4-Ga-ZSM-5 to NH4H2PO4 solution, adjust the solution pH to 5.2-7.5, the solution temperature to 20-25°C, stir for 1-1.5 hours, then heat the solution to 75-85°C, stir until dry, and then calcine to obtain P-Ga-ZSM-5;

[0011] P-Ga-ZSM-5 was added to Cu(NO3)2 solution, the pH value of the solution was adjusted to 4.5-5.5, stirred for 20-30 hours, washed, dried and calcined to obtain P-Ga / Cu-ZSM-5.

[0012] The role of NaOH is to desiliconize the ZSM-5, exposing Al sites in the skeleton, which paves the way for the subsequent introduction of water to promote the formation of terminal hydroxyl groups on the ring (enhancing acidity). The introduction of Ga facilitates hydrogen abstraction (the inventors have theoretically confirmed that the hydrogen abstraction step is a key energy barrier to the SCR reaction). Experimental verification revealed that the simultaneous introduction of Ga (NaOH treatment followed by Ga(NO3)3 impregnation) produced no significant difference in final activity, so we combined them simultaneously to simplify the experimental steps.

[0013] The impregnation process is conducted at a relatively high temperature (60-80°C). Heating increases the fluidity and diffusion rate of the solvent. During the impregnation process, heating promotes the diffusion of solute molecules in the solvent, allowing them to penetrate the interior of the material more quickly. This helps improve the uniformity and efficiency of the impregnation.

[0014] Ga(NO3)3 regulates Lewis acid, while NaOH promotes the formation of Brønsted acid. In specific reactions, it is crucial to adjust the amounts of the two acids so that they work together to stabilize the cycle. Excessive NaOH can damage the ZSM-5 framework, making it difficult to maintain the MFI structure. Excessive Ga(NO3)3 deposition can affect the subsequent dispersion and anchoring of Cu sites. Low concentrations of either lead to decreased activity (compared to the activity at the optimal introduction concentration).

[0015] In the final product molecular sieve, the influence of impurity Na ions must be eliminated, so the Na ions need to be replaced. The reasons for converting Na-Ga-ZSM-5 into NH4-Ga-ZSM-5 first are as follows:

[0016] NH4-ZSM-5 has higher acidity, which is beneficial for the subsequent Cu 2+ Ion exchange is very important, acidity helps to increase Cu 2+ The adsorption and dispersion of Cu ions promote their interaction with the ZSM-5 molecular sieve framework, which helps to form a highly dispersed Cu-ZSM-5 catalyst and improve its catalytic performance; Cu 2+ Ions generally cannot directly replace Na + ions, because Cu 2+ Ions and Na + The exchange capacity between ions is weak; NH 4+ Compared with Na + Easier to remove, such as by heat treatment.

[0017] The pH value of the solution is adjusted to 5.2-7.5 to provide a suitable acid-base environment, which is conducive to the reaction. In this pH range, the acidity and alkalinity of phosphate are moderate, which is conducive to the reaction with NH4Cl2 in the aminoaluminum silicate molecular sieve. 4+ For ion exchange, too low or too high pH value may affect the effect and selectivity of the reaction.

[0018] The focus of room temperature stirring is to carry out the reaction, while the subsequent heating stirring is to dry out the moisture on the basis of sufficient stirring in the former, control the humidity, and reduce the impact of humidity on the sample during subsequent calcination. At the same time, heating stirring is also a further guarantee to prevent insufficient stirring caused by insufficient time or slow rotor speed during room temperature stirring.

[0019] The pH value of the solution is adjusted to 4.5-5.5. The purpose of adjusting the solution to a slightly acidic environment is to inhibit the side reaction process in the reaction and prevent the damage to the phosphate ions under alkaline conditions.

[0020] In some embodiments, the mass ratio of ZSM-5 to the solute in the mixed solution of NaOH and Ga(NO 3 ) 3 is 1:0.16-0.2.

[0021] In some embodiments, the mass ratio of Na-Ga-ZSM-5 to NH4Cl is 1:0.45-0.55. 4+ During the ion exchange process, H + ions, making the system more acidic. If the mass of NH4Cl is too large, the released H + The number of ions will increase, causing the reaction system to become overly acidic, which may destroy or change the properties of the catalyst or reactants, affecting the selectivity and yield of the reaction.

[0022] The ion exchange process between NH4Cl and Na-ZSM-5 is an exothermic reaction. Excessive NH4Cl concentration increases the exothermic effect, leading to higher reaction temperatures. High temperatures can lead to the formation of reaction byproducts, decreased selectivity, or catalyst deactivation.

[0023] In some embodiments, the mass ratio of NH4-Ga-ZSM-5 to NH4PO4 is 1:0.005-0.007.

[0024] In some embodiments, the mass ratio of P-Ga-ZSM-5 to Cu(NO3)2 is 1:0.05-0.06.

[0025] In some embodiments, the calcination temperature for obtaining P-Ga-ZSM-5 is 500-600° C., and the calcination time is 5-7 h.

[0026] In some embodiments, the calcination temperature for obtaining P-Ga / Cu-ZSM-5 is 500-600° C., and the calcination time is 5-7 h.

[0027] In a second aspect, the present invention provides a phosphorus-gallium modified copper-based molecular sieve waste gas purification functional material prepared by the preparation method.

[0028] In a third aspect, the present invention provides an application of the phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material in catalytic denitrification of mobile source exhaust gas.

[0029] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0030] Compared with the original Cu-ZSM-5 catalyst, the P-Ga / Cu-ZSM-5 catalyst prepared by the present invention maintains its denitrification activity in a dry environment without phosphorus poisoning. Under low-temperature and wet conditions, the denitrification activity of the P-Ga / Cu-ZSM-5 catalyst is about 20% higher than that of the Cu-ZSM-5 catalyst. Stability tests have shown that the water resistance and SO2 poisoning resistance of the P-Ga / Cu-ZSM-5 are both higher than those of Cu-ZSM-5. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] Figure 1 This is a structural diagram of a fixed-bed denitrification reaction test bench;

[0033] Figure 2 This is the denitration activity curve of the Cu-ZSM-5 catalyst prepared in Example 1;

[0034] Figure 3 This is the denitration activity curve of the P-Ga / Cu-ZSM-5 catalyst prepared in Example 2;

[0035] Figure 4 This is the denitration activity curve of the P-Cu-ZSM-5 catalyst prepared in Comparative Example 1;

[0036] Figure 5 This is the denitration activity curve of the Ga-Cu-ZSM-5 catalyst prepared in Comparative Example 2;

[0037] Figure 6 This is a low-temperature and wet working condition stability test curve of the Cu-ZSM-5 catalyst prepared in Example 1;

[0038] Figure 7 This is a low-temperature and wet working condition stability test curve of the P-Ga / Cu-ZSM-5 catalyst prepared in Example 2;

[0039] Figure 8 This is a low-temperature and wet working condition stability test curve of the P-Cu / ZSM-5 catalyst prepared in Comparative Example 1;

[0040] Figure 9 This is a low-temperature and wet working condition stability test curve of the Ga-Cu / ZSM-5 catalyst prepared in Comparative Example 2;

[0041] Figure 10This is a combined comparison chart of the denitration activity curves of the SCR catalysts Cu-ZSM-5 (CZ), P-Ga / Cu-ZSM-5 (PG-CZ), P-Cu / ZSM-5 (P-CZ), and Ga-Cu / ZSM-5 (G-CZ) prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2;

[0042] Figure 11 This is a combined comparison chart of the low-temperature and wet working condition stability test curves of the SCR catalysts Cu-ZSM-5 (CZ), P-Ga / Cu-ZSM-5 (PG-CZ), P-Cu / ZSM-5 (P-CZ), and Ga-Cu / ZSM-5 (G-CZ) prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

[0043] Figure 1 Among them, 1. Mass flow meter; 2. Gas premixer; 3. Flue gas preheating section; 4. Temperature controller; 5. Fixed bed quartz reactor; 6. Concentrated phosphoric acid; 7. Drying bottle; 8. Flue gas analyzer. DETAILED DESCRIPTION

[0044] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0045] In a first aspect, the present invention provides a method for preparing a phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material, comprising the following steps:

[0046] The ZSM-5 molecular sieve is placed in a mixed solution of NaOH and Ga(NO3)3, and the mixed solution is then stirred in a water bath, filtered and washed until neutral, and then dried in a drying oven to obtain Na-Ga-ZSM-5;

[0047] Na-Ga-ZSM-5 was added to NH4Cl solution and stirred in a water bath, followed by centrifugation to obtain NH4-Ga-ZSM-5;

[0048] NH4-Ga-ZSM-5 was added to NH4H2PO4 solution, and ammonia water was added to adjust the pH to 5.2-7.5, followed by stirring and water bath stirring until dry and calcining to obtain P-Ga-ZSM-5;

[0049] P-ZSM-5 was added to Cu(NO3)2 solution and stirred, and ammonia water was added to adjust the pH to 4.5-5.5. Subsequently, the solution was filtered, washed, dried and calcined to obtain P-Ga / Cu-ZSM-5.

[0050] In some embodiments, when ZSM-5 molecular sieve reacts with a mixed solution to produce Na-Ga-ZSM-5, the solute ratio (NaOH+Ga(NO3)3:ZSM-5) is 0.1-0.16:1, and the mass ratio of NaOH to Ga(NO3)3 is 1.2-1.5:1.

[0051] Furthermore, the stirring temperature of the water bath is 60-80° C., and the stirring time of the water bath is 1-1.5 h.

[0052] Furthermore, the drying temperature is 70-90° C., and the drying time is 8-12 hours.

[0053] In some embodiments, when the Na-Ga-ZSM-5 catalyst reacts with the NH4Cl solution to produce NH4-Ga-ZSM-5, the solute ratio (NH4Cl:Na-Ga-ZSM-5) is 0.45-0.55:1.

[0054] Furthermore, the stirring temperature of the water bath is 70-90° C., and the stirring time of the water bath is 1-1.5 h.

[0055] In some embodiments, when the NH4-Ga-ZSM-5 catalyst reacts with the NH4H2PO4 solution to prepare P-Ga-ZSM-5, the solute ratio (NH4H2PO4:NH4-Ga-ZSM-5) is 0.005-0.007:1

[0056] Furthermore, the stirring temperature is 20-25° C., and the stirring time is 1-1.5 h.

[0057] Furthermore, the stirring temperature of the water bath is 70-90°C.

[0058] Furthermore, the calcination temperature is 500-600° C., and the calcination time is 5-7 hours.

[0059] In some embodiments, when the P-Ga-ZSM-5 catalyst is reacted with Cu(NO3)2 solution to prepare P-Ga / Cu-ZSM-5, the solute ratio (Cu(NO3)3:P-Ga-ZSM-5) is 0.05-0.06:1

[0060] Furthermore, the stirring temperature is 25-40° C., and the stirring time is 24 h.

[0061] Furthermore, the drying temperature is 60-80° C., and the drying time is 8-12 hours.

[0062] Furthermore, the calcination temperature is 500-600° C., and the calcination time is 5-7 hours.

[0063] In a second aspect, the present invention provides a phosphorus-gallium modified copper-based molecular sieve waste gas purification functional material prepared by the preparation method.

[0064] The present invention will be further described below with reference to the embodiments.

[0065] Example 1

[0066] A certain amount of ZSM-5 catalyst (silicon-aluminum ratio of 40) was mixed with 0.2 mol / L NaOH solution at a solute ratio of 0.16:1 to form a turbid solution, stirred in a 75°C water bath for 1 hour, and then filtered and washed with deionized water until neutral. The neutral filter cake was placed in a forced air drying oven and dried at 80°C for 12 hours to constant weight. The resulting material was then ground and sieved to obtain Na-ZSM-5 powder below 100 mesh. A certain amount of 100 mesh Na-ZSM-5 powder was mixed with 0.5 mol / L NH4Cl solution at a solute ratio of 0.54:1, then heated in an 80°C water bath, magnetically stirred for 1 hour, and then vacuum filtered for solid-liquid separation. The obtained solid was mixed with a 0.01 mol / L copper nitrate solution at a solute ratio of 0.05:1. The mixture was then magnetically stirred at room temperature for 24 hours. The pH was maintained at 4.5-5.5 with aqueous ammonia. The mixture was then filtered and washed three times. The filter cake was dried in a forced-air drying oven at 80°C for 12 hours to constant weight. Finally, the temperature was increased from room temperature to 550°C at 3°C / min in a muffle furnace, calcined for 5 hours, and then naturally cooled. This yielded a Cu-exchanged molecular sieve catalyst, designated Cu-ZSM-5.

[0067] Example 2

[0068] Take a certain amount of ZSM-5 catalyst (silicon-aluminum ratio of 40) and a mixed solution of 0.2 mol / L NaOH and Ga(NO3)3 at a solute ratio of 0.16:1 to form a turbid solution. Stir in a 75°C water bath for 1 hour, then filter and wash with deionized water until neutral. Place the neutral filter cake in a forced air drying oven at 80°C for 12 hours to constant weight. Then grind and sieve the resulting material to obtain Na-Ga-ZSM-5 powder below 100 mesh.

[0069] A certain amount of 100-mesh Na-Ga-ZSM-5 powder was mixed with 0.5 mol / L NH4Cl solution at a solute ratio of 0.54:1. The mixture was then heated in a water bath at 80°C and magnetically stirred for 1 h. The solid-liquid separation was then performed by vacuum filtration.

[0070] A certain amount of the obtained solid was mixed with 0.0032 mol / L NH4H2PO4 solution at a solute ratio of 0.006:1, and the pH was adjusted to 5.2-7.5 with aqueous ammonia. The mixture was then stirred at room temperature for 1 h and then transferred to an 80°C water bath and stirred until dry. Finally, the temperature was raised from room temperature to 550°C at 3°C / min in a muffle furnace, calcined for 5 h, and then naturally cooled.

[0071] The resulting solid was mixed with a 0.01 mol / L copper nitrate solution at a solute ratio of 0.05:1. The mixture was then magnetically stirred at room temperature for 24 hours. The pH was maintained at 4.5-5.5 with aqueous ammonia. The mixture was then filtered and washed three times. The filter cake was dried in a forced-air drying oven at 80°C for 12 hours to constant weight. Finally, the mixture was heated in a muffle furnace from room temperature to 550°C at a rate of 3°C / min, calcined for 5 hours, and then cooled naturally. This yielded a phosphorus-gallium-modified copper-based molecular sieve exhaust gas purification functional material, designated P-Ga / Cu-ZSM-5.

[0072] Fixed bed denitrification reaction experiment, the experimental platform used is as follows Figure 1 As shown:

[0073] The experimental process is as follows: the gases are premixed in proportion to prepare simulated flue gas, the simulated flue gas is preheated using a flue gas preheating section 3, the preheated simulated flue gas enters a fixed bed quartz reactor (filled with 0.1 g of the catalyst prepared in the embodiment) 5 for catalytic denitrification, the simulated flue gas after catalytic denitrification flows through concentrated phosphoric acid and is dried, and the gas composition is analyzed using a flue gas analyzer 8.

[0074] The reaction conditions of the experimental process are as follows: the simulated flue gas mass flow rate is 100 mL / min, the flow rates of each component are [NO] = 500 ppm, [NH3] = 500 ppm, [O2] = 10 vol%, and N2 is used as the balance gas. The space velocity ratio (GHSV) is set to 60000 mL / (g·h).

[0075] The test temperature range for catalytic denitrification activity is 150-450°C;

[0076] The low temperature and humidity stability test temperature is divided into two ranges, one is 30-200℃, humidity is 10vol%; the other temperature range is 200-400℃, humidity is 10vol%, and SO2 concentration is 1000ppm.

[0077] During the test, it was found that phosphorus and water have a certain synergistic effect. Under such high humidity conditions, the SCR reaction activity is often promoted. However, if the humidity is low (such conditions may also occur in practice), the synergistic effect is not obvious. At this time, the introduction of phosphorus may not only fail to improve the activity, but also cause the phosphorus poisoning phenomenon often mentioned in the literature. Figure 6 Activity tests under a representative dry environment prove that the present invention can effectively promote reaction activity in a low-temperature and high-humidity environment by precisely controlling the introduction of phosphorus content, while also ensuring that the catalytic performance of commonly used commercial catalysts is maintained in a dry environment.

[0078] Depend on Figure 7It can be seen that when the exhaust gas temperature is low (such as below 200°C) and the moisture content is high, the P-Ga / Cu-ZSM-5 catalyst prepared by the method of the present invention in Example 2 has better catalytic performance, which is much higher than the Cu-ZSM-5 catalyst prepared in Example 1.

[0079] However, when the exhaust gas temperature is high (such as above 200°C), the moisture content in the exhaust gas is large and contains a high concentration of SO2, although the catalytic denitrification performance of the catalysts prepared in Example 1 and Example 2 decreases to a certain extent, the catalytic performance of the P-Ga / Cu-ZSM-5 catalyst prepared in Example 2 is still much higher than the catalytic performance of the Cu-ZSM-5 catalyst prepared in Example 1.

[0080] The above description shows that the catalyst prepared by the present invention has good water resistance and SO2 poisoning resistance.

[0081] Comparative Example 1

[0082] A certain amount of ZSM-5 catalyst (silicon-aluminum ratio of 40) was mixed with 0.2 mol / L NaOH solution at a solute ratio of 0.16:1 to form a turbid solution, stirred in a 75°C water bath for 1 hour, and then filtered and washed with deionized water until neutral. The neutral filter cake was placed in a forced air drying oven and dried at 80°C for 12 hours to constant weight. The resulting material was then ground and sieved to obtain Na-ZSM-5 powder below 100 mesh. A certain amount of 100 mesh Na-ZSM-5 powder was mixed with 0.5 mol / L NH4Cl solution at a solute ratio of 0.54:1, then heated in an 80°C water bath, magnetically stirred for 1 hour, and then vacuum filtered for solid-liquid separation. A certain amount of the obtained solid was mixed with 0.0032 mol / L NH4H2PO4 solution at a solute ratio of 0.006:1, and the pH was adjusted to 5.2-7.5 with aqueous ammonia. The mixture was then stirred at room temperature for 1 hour and then transferred to an 80°C water bath and stirred until dry. Finally, the temperature was raised from room temperature to 550°C at 3°C / min in a muffle furnace, calcined for 5 hours, and then naturally cooled.

[0083] The obtained solid was mixed with a 0.01 mol / L copper nitrate solution at a solute ratio of 0.05:1, then magnetically stirred at room temperature for 24 hours. The pH was maintained at 4.5-5.5 with aqueous ammonia, followed by filtration and washing three times. The filter cake was dried in a forced air drying oven at 80°C for 12 hours to constant weight. Finally, the temperature was increased from room temperature to 550°C at 3°C / min in a muffle furnace, calcined for 5 hours, and then naturally cooled. This yielded a phosphorus-modified Cu-ZSM-5 molecular sieve SCR denitration catalyst, designated P-Cu / ZSM-5.

[0084] Comparative Example 2

[0085] Take a certain amount of ZSM-5 catalyst (silicon-aluminum ratio of 40) and a mixed solution of 0.2 mol / L NaOH and Ga(NO3)3 at a solute ratio of 0.16:1 to form a turbid solution. Stir in a 75°C water bath for 1 hour, then filter and wash with deionized water until neutral. Place the neutral filter cake in a forced air drying oven at 80°C for 12 hours to constant weight. Then grind and sieve the resulting material to obtain Na-Ga-ZSM-5 powder below 100 mesh.

[0086] A certain amount of 100-mesh Na-Ga-ZSM-5 powder was mixed with 0.5 mol / L NH4Cl solution at a solute ratio of 0.54:1. The mixture was then heated in a water bath at 80°C and magnetically stirred for 1 h. The solid-liquid separation was then performed by vacuum filtration.

[0087] The obtained solid was mixed with a 0.01 mol / L copper nitrate solution at a solute ratio of 0.05:1. The mixture was then magnetically stirred at room temperature for 24 hours. The pH was maintained at 4.5-5.5 with aqueous ammonia. The mixture was then filtered and washed three times. The filter cake was dried in a forced-air drying oven at 80°C for 12 hours to constant weight. Finally, the temperature was increased from room temperature to 550°C at a rate of 3°C / min in a muffle furnace, calcined for 5 hours, and then naturally cooled. This yielded a phosphorus-gallium-modified copper-based molecular sieve exhaust gas purification functional material, designated Ga-Cu / ZSM-5.

[0088] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for improving the removal of NO from mobile source NH3-SCR x The preparation method of phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material is characterized by: The steps include: ZSM-5 is stirred and impregnated in a mixed solution of NaOH and Ga(NO3)3 at a temperature of 60-80°C for 1-1.5 hours. In the mixed solution, the mass ratio of solute to water is 0.008-0.01:1, and the mass ratio of NaOH to Ga(NO3)3 is 1.2-1.5:

1. After impregnation, the mixture is washed and dried to obtain Na-Ga-ZSM-5. Add Na-Ga-ZSM-5 to NH4Cl solution and stir in a water bath. The concentration of NH4Cl solution is 0.022-0.027 g / L. The stirring temperature of the water bath is 70-90°C. The stirring time is 1-1.5 h to obtain NH4-Ga-ZSM-5. Add NH4-Ga-ZSM-5 to NH4H2PO4 solution, adjust the solution pH to 5.2-7.5, the solution temperature to 20-25°C, stir for 1-1.5 hours, then heat the solution to 75-85°C, stir until dry, and then calcine to obtain P-Ga-ZSM-5; P-Ga-ZSM-5 was added to Cu(NO3)2 solution, the pH value of the solution was adjusted to 4.5-5.5, stirred for 20-30 hours, washed, dried and calcined to obtain P-Ga / Cu-ZSM-5.

2. The method for preparing the phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material according to claim 1, characterized in that: The mass ratio of ZSM-5 to the solute in the mixed solution of NaOH and Ga(NO3)3 is 1:0.16-0.

2.

3. The method for preparing the phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material according to claim 1, characterized in that: The mass ratio of Na-Ga-ZSM-5 to NH4Cl is 1:0.45-0.

55.

4. The method for preparing the phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material according to claim 1, characterized in that: The mass ratio of NH4-Ga-ZSM-5 to NH4PO4 is 1:0.005-0.

007.

5. The method for preparing the phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material according to claim 1, characterized in that: The mass ratio of P-Ga-ZSM-5 to Cu(NO3)2 is 1:0.05-0.

06.

6. The method for preparing the phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material according to claim 1, characterized in that: The calcination temperature for obtaining P-Ga-ZSM-5 is 500-600° C., and the calcination time is 5-7 h.

7. The method for preparing the phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material according to claim 1, characterized in that: The calcination temperature for obtaining P-Ga / Cu-ZSM-5 is 500-600° C., and the calcination time is 5-7 h.

8. The method for preparing the phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material according to claim 7, characterized in that: The calcination temperature of the P-Ga / Cu-ZSM-5 is 520-580° C., and the calcination time is 5-6 h.

9. A method for improving the removal of NO from mobile source NH3-SCR x The phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional material is characterized by: Prepared by the preparation method according to any one of claims 1 to 8.

10. The method for improving the removal of NO by NH3-SCR from mobile sources as claimed in claim 9 x Application of phosphorus-gallium modified copper-based molecular sieve exhaust gas purification functional materials in catalytic denitrification of mobile source exhaust gas.

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