CN115532304B - A kind of molecular sieve catalyst for ammonia purification of ammonia internal combustion engine and its preparation method and use - Google Patents

Abstract

The invention relates to a molecular sieve catalyst for ammonia purification of ammonia internal combustion engines and its preparation method and use. The preparation method includes the following steps: (1) using an ion exchange method to first mix and stir ammonia-type molecular sieve and copper salt solution, and then sequentially Solid-liquid separation, first drying and first roasting are carried out to obtain a loaded copper molecular sieve; (2) the copper-loaded molecular sieve obtained in step (1) and the solvent are mixed and stirred for the second time, and then treated with platinum salts in sequence , evaporation, second drying and second roasting to obtain the molecular sieve catalyst. The molecular sieve catalyst includes active components in terms of mass percentage: 0.5-2% platinum and 2-4% copper, and the balance is molecular sieve carrier. The use includes using the molecular sieve catalyst to catalytically purify ammonia gas formed during the operation of an ammonia internal combustion engine. To solve the problem of significant reduction in catalytic performance of current ammonia oxygen catalysts in high-humidity and low-temperature environments.

Description

A kind of molecular sieve catalyst for ammonia purification of ammonia internal combustion engine and its preparation method and use

Technical field

The present invention relates to the field of ammonia oxygen catalysis, specifically to a molecular sieve catalyst for ammonia purification of ammonia internal combustion engines and its preparation method and use. In particular, it relates to a preparation method of a molecular sieve catalyst for ammonia purification of ammonia internal combustion engines, the resulting catalyst and its use.

Background technique

At present, due to the shortage of fossil fuels, ammonia is an ideal energy storage material. Its molecules do not contain carbon elements, and the complete combustion products only include water and nitrogen. And compared with most gaseous fuels, it is easy to be compressed into a liquid state, making it easy to store and transport. As the second largest chemical product in the world, ammonia has relatively complete storage and transportation facilities. Ammonia therefore has the potential to become an alternative fuel for internal combustion engines.

For example, CN114575996A, an ammonia internal combustion engine and its control method, belongs to the field of internal combustion engines. It provides an internal combustion engine device without carbon emissions, and takes into account the difficulty of hydrogen storage and transportation and adopts the main strategy of using ammonia as fuel. By introducing the exhaust gas generated by the internal combustion engine into the ammonia cracking device, partial cracking of ammonia is achieved. The hydrogen produced by the cracking of ammonia increases the reactivity of the gas in the cylinder, enabling stable operation of the entire internal combustion engine. The hydrogen used is only used for starting the internal combustion engine, and the amount is small, which can avoid the problem of difficulty in carrying hydrogen. This solution selects a fuel supply strategy based on working conditions to achieve efficient operation of the ammonia internal combustion engine. The designed ammonia internal combustion engine starts with pure hydrogen, and after starting, pure ammonia is used as the only fuel to supply the internal combustion engine.

CN102859171A discloses an ammonia combustion internal combustion engine using ammonia as fuel, including an ammonia supply device that supplies ammonia to a combustion chamber, and a temperature-increasing and pressure-increasing device that increases the temperature or pressure of ammonia supplied to the ammonia supply device. The temperature-increasing and pressure-increasing device uses energy generated with the operation of the internal combustion engine to increase the temperature or pressure of ammonia. Thereby, the energy efficiency of the entire internal combustion engine or the entire vehicle equipped with the internal combustion engine can be maintained high, and the temperature or pressure of ammonia supplied to the ammonia injection valve can be appropriately controlled.

However, during the combustion process of an ammonia internal combustion engine, part of the fuel ammonia gas will not be fully burned, and the exhaust gas will enter the atmosphere and cause pollution. At the same time, a large amount of water vapor will be formed during the combustion process of the ammonia gas, causing the existing ammonia decomposition catalyst to operate at high temperatures and high temperatures. It is easy to fail in a wet environment, resulting in the exhaust gas not being effectively purified.

Contents of the invention

In view of the problems existing in the prior art, the purpose of the present invention is to provide a molecular sieve catalyst for ammonia purification of ammonia internal combustion engines and its preparation method and application, so as to solve the problem that the catalytic performance of the current ammonia oxygen catalyst is significantly reduced in high humidity and low temperature environments. .

To achieve this goal, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a method for preparing a molecular sieve catalyst for ammonia purification of an ammonia internal combustion engine. The preparation method includes the following steps:

(1) Use the ion exchange method to first mix and stir the ammonia-type molecular sieve and the copper salt solution, and then perform solid-liquid separation, first drying and first roasting in sequence to obtain a loaded copper molecular sieve;

(2) The copper-loaded molecular sieve obtained in step (1) and the solvent are mixed and stirred for a second time, and then subjected to platinum salt treatment, evaporation, second drying and second roasting in sequence to obtain the molecular sieve catalyst.

The preparation method provided by the invention introduces active components platinum and copper through a specific preparation process, and utilizes the synergistic effect of metals to simultaneously improve the low-temperature activity and nitrogen selectivity of the catalyst ammonia oxidation reaction. Using the ion exchange method, copper ions are exchanged into the pores of the molecular sieve, and are evenly distributed in the catalyst in the form of copper ions. The impregnation method is used to evenly load platinum on the molecular sieve carrier. After high-temperature roasting, the platinum mainly exists in the metallic state. Metallic platinum has high activity and can effectively convert ammonia gas in ammonia internal combustion engines. Thus, metallic platinum and ionic copper are used to achieve efficient ammonia oxidation reaction in a high-humidity environment, meeting the purification requirements of unburned ammonia gas in ammonia internal combustion engines.

As a preferred technical solution of the present invention, the copper salt used in preparing the copper salt solution in step (1) includes one or a combination of at least two of copper chloride, copper sulfate, copper nitrate or copper acetate, preferably copper nitrate.

Preferably, the ammonia-type molecular sieve in step (1) includes one or a combination of at least two of ZSM-5 molecular sieve, SSZ-13 molecular sieve or Y molecular sieve.

Preferably, the molar concentration of copper element in the copper salt solution in step (1) is 0.05-2mol/L, for example, it can be 0.05mol/L, 0.06mol/L, 0.07mol/L, 0.08mol/L, 0.09mol /L, 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L, 0.6mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L, 1mol/ L, 1.1mol/L, 1.2mol/L, 1.3mol/L, 1.4mol/L, 1.5mol/L, 1.6mol/L, 1.7mol/L, 1.8mol/L, 1.9mol/L or 2mol/L etc., but are not limited to the listed values, and other unlisted values within this range are also applicable.

Preferably, the solid-liquid ratio g/mL of the ammonia molecular sieve and copper salt solution in step (1) is 1:(80-150), for example, it can be 1:80, 1:85, 1:90, 1:95 , 1:100, 1:105, 1:110, 1:115, 1:120, 1:125, 1:130, 1:135, 1:140, 1:145 or 1:150, etc., but not limited to all For the listed values, other non-listed values within the range are also applicable.

As a preferred technical solution of the present invention, the temperature of the first mixing and stirring in step (1) is 40-60°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃ or 60℃, etc., but not limited to the listed values , other unlisted values within this range are also applicable.

Preferably, the first mixing time in step (1) is 4-8h, for example, it can be 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9 h, 5h, 5.1h, 5.2h, 5.3h, 5.4h, 5.5h, 5.6h, 5.7h, 5.8h, 5.9h, 6h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h , 6.7h, 6.8h, 6.9h, 7h, 7.1h, 7.2h, 7.3h, 7.4h, 7.5h, 7.6h, 7.7h, 7.8h, 7.9h or 8h, etc., but are not limited to the listed values, Other values within this range not listed are also applicable.

As a preferred technical solution of the present invention, the temperature of the first roasting in step (1) is 400-650°C, for example, it can be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C ℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640°C or 650°C, etc., but are not limited to the listed values, and other unlisted values within this range are also applicable.

Preferably, the data of the first roasting in step (1) is 4-8h, for example, it can be 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h , 5h, 5.1h, 5.2h, 5.3h, 5.4h, 5.5h, 5.6h, 5.7h, 5.8h, 5.9h, 6h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h, 7h, 7.1h, 7.2h, 7.3h, 7.4h, 7.5h, 7.6h, 7.7h, 7.8h, 7.9h or 8h, etc., but are not limited to the listed values. The same applies to other values within the range not listed.

As a preferred technical solution of the present invention, the solvent in step (2) includes water. For example, it can be deionized water or industrial return water that meets the requirements.

Preferably, the temperature of the second mixing and stirring in step (2) is 20-40°C, for example, it can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C , 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃ or 40℃, etc., but not limited to the listed values, other values within this range The same applies to non-enumerated values.

Preferably, the second mixing time in step (2) is 0.5-3h, for example, it can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 1.1h, 1.2h, 1.3h, 1.4 h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3h, etc., but Not limited to the listed values, other unlisted values within this range are also applicable.

As a preferred technical solution of the present invention, the platinum salt treatment in step (2) is to add platinum salt to the material obtained by the second mixing and stirring.

Preferably, the platinum salt used in the platinum salt treatment in step (2) includes one or a combination of at least two of tetraammine platinum nitrate, chloroplatinic acid, platinum chloride or ammonium chloroplatinate, preferably tetramine. Platinum nitrate.

Preferably, the mass ratio of the copper-loaded molecular sieve to the platinum element in the platinum salt used in the platinum salt treatment in step (2) is 1: (0.005-0.02), for example, it can be 1:0.005, 1:0.006, 1:0.007, 1:0.008, 1:0.009, 1:0.01, 1:0.011, 1:0.012, 1:0.013, 1:0.014, 1:0.015, 1:0.016, 1:0.017, 1:0.018, 1:0.019 or 1: 0.02, etc., but are not limited to the listed values, and other unlisted values within this range are also applicable.

As a preferred technical solution of the present invention, the evaporation in step (2) includes water bath rotary evaporation.

Preferably, the evaporation temperature in step (2) is 50-80°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C , 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76 ℃, 77 ℃, 78 ℃, 79 ℃ or 80 ℃, etc., but are not limited to the listed values, and other unlisted values within this range are also applicable.

Preferably, the temperature of the second roasting in step (2) is 400-650°C, for example, it can be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃ or 650℃ etc., but are not limited to the listed values, and other unlisted values within this range are also applicable.

Preferably, the second roasting time in step (2) is 3-7h, for example, it can be 3h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h , 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h, 5h, 5.1h, 5.2h, 5.3h, 5.4h, 5.5h, 5.6h, 5.7h, 5.8h, 5.9h, 6h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h, 7h, 7.1h, 7.2h, 7.3h, 7.4 h, 7.5h, 7.6h, 7.7h, 7.8h, 7.9h or 8h, etc., but are not limited to the listed values, and other unlisted values within this range are also applicable.

As a preferred technical solution of the present invention, the preparation method includes the following steps:

(1) Use the ion exchange method to first mix and stir the ammonia-type molecular sieve and the copper salt solution, and then perform solid-liquid separation, first drying and first roasting in sequence to obtain a loaded copper molecular sieve;

The copper salt used in the copper salt solution in the configuration step (1) includes one or a combination of at least two of copper chloride, copper sulfate, copper nitrate or copper acetate; the ammonia type molecular sieve includes ZSM-5 molecular sieve, SSZ- One or a combination of at least two of 13 molecular sieves or Y molecular sieves; the molar concentration of copper element in the copper salt solution is 0.05-2mol/L; the solid-to-liquid ratio of the ammonia molecular sieve and the copper salt solution is g/mL is 1: (80-150); the temperature of the first mixing and stirring is 40-60°C, and the time is 4-8h; the temperature of the first roasting is 400-650°C, and the time is 4-8h;

(2) The copper-loaded molecular sieve obtained in step (1) and the solvent are mixed and stirred for a second time, and then subjected to platinum salt treatment, evaporation, second drying and second roasting in sequence to obtain the molecular sieve catalyst;

The solvent in step (2) includes water; the temperature of the second mixing and stirring is 20-40°C, and the time is 0.5-3h; the platinum salt treatment is to add platinum salt to the material obtained by the second mixing and stirring, the The platinum salt used in the platinum salt treatment includes one or a combination of at least two of tetraammine platinum nitrate, chloroplatinic acid, platinum chloride or ammonium chloroplatinate. The copper molecular sieve loaded in the platinum salt treatment and the platinum salt used The mass ratio of platinum elements is 1:(0.005-0.02); the evaporation includes water bath rotary evaporation, the temperature is 50-80°C; the second roasting temperature is 400-650°C, and the time is 3-7h.

In a second aspect, the present invention provides a molecular sieve catalyst obtained by the preparation method described in the first aspect. The molecular sieve catalyst includes active components in terms of mass percentage: platinum 0.5-2% and copper 2-4%, with the balance As a molecular sieve carrier.

In the present invention, in the preparation process of the molecular sieve catalyst, in order to ensure the loading of active components, the loading process of corresponding elements can be carried out multiple times.

In a third aspect, the present invention provides the use of the molecular sieve catalyst obtained by the preparation method as described in the first aspect. The use includes using the molecular sieve catalyst to catalytically purify the exhaust gas formed during the operation of an ammonia internal combustion engine;

The temperature of the catalytic purification is 175-500°C;

The water content in the exhaust gas of the ammonia internal combustion engine is 5-15% in terms of volume percentage;

The concentration of ammonia in the exhaust gas formed by the ammonia internal combustion engine is 300-1500 ppm.

In the present invention, the total flow rate of gas during purification can be 400-600mL/min, and the air velocity can be 100000-300000h ^-1 .

Compared with existing technical solutions, the present invention has the following beneficial effects:

(1) The ammonia oxidation catalyst of the present invention has high activity in the range of 200-400°C and in the presence of 10% water vapor, and can meet the requirements for catalyst purification of ammonia gas in ammonia internal combustion engines under high temperature and high humidity conditions. The precious metal platinum is the reason for the high activity in the entire temperature range. The precious metal platinum has excellent oxidation ability and is distributed on the molecular sieve carrier in the form of small nanoparticles, so that ammonia can be completely oxidized.

(2) The ammonia oxidation catalyst of the present invention has high nitrogen selectivity (82-95%) in the range of 200-400°C, meeting the requirements for gas purification in ammonia internal combustion engines. The active metal copper exists in the form of highly dispersed ions. In the catalyst, by-product nitrogen oxides can be selectively reduced to nitrogen, thereby improving nitrogen selectivity.

Description of the drawings

Figure 1 is a diagram of ammonia gas conversion rate and nitrogen gas selectivity in the ammonia oxidation reaction in Application Example 1 of the present invention.

The present invention is described in further detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be determined by the claims.

Detailed ways

In order to better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

Example 1

This embodiment provides a molecular sieve catalyst for ammonia purification of ammonia internal combustion engines. The molecular sieve catalyst includes active components in terms of mass percentage: 0.5% platinum and 3% copper, and the balance is a molecular sieve carrier.

The preparation method is as follows:

(1) Use the ion exchange method to first mix and stir the ammonia-type molecular sieve and the copper salt solution, and then perform solid-liquid separation, first drying and first roasting in sequence to obtain a loaded copper molecular sieve;

The copper salt used in the copper salt solution of configuration step (1) is copper nitrate; the ammonia-type molecular sieve is SSZ-13 molecular sieve; the molar concentration of copper element in the copper salt solution is 0.1mol/L; the ammonia-type molecular sieve The solid-to-liquid ratio g/mL of the copper salt solution is 1:100; the temperature of the first mixing and stirring is 60°C and the time is 6h; the temperature of the first roasting is 600°C and the time is 5h;

(2) The copper-loaded molecular sieve obtained in step (1) and the solvent are mixed and stirred for a second time, and then subjected to platinum salt treatment, evaporation, second drying and second roasting in sequence to obtain the molecular sieve catalyst;

The solvent in step (2) is deionized water; the temperature of the second mixing and stirring is 25°C, and the time is 0.5h; the platinum salt treatment is to add platinum salt to the material obtained by the second mixing and stirring, and the platinum salt is added to the material obtained by the second mixing and stirring. The platinum salt used in the salt treatment is tetraammine platinum nitrate, and the mass ratio of the copper molecular sieve loaded in the platinum salt treatment to the platinum element in the platinum salt used is 1:0.005; the evaporation is a water bath rotary evaporation, and the temperature is 60°C; The temperature of the second roasting is 550°C and the time is 6 hours.

Example 2

This embodiment provides a molecular sieve catalyst for ammonia purification of ammonia internal combustion engines. The molecular sieve catalyst includes active components in terms of mass percentage: 1% platinum and 4% copper, and the balance is a molecular sieve carrier.

The preparation method is as follows:

(1) Use the ion exchange method to first mix and stir the ammonia-type molecular sieve and the copper salt solution, and then perform solid-liquid separation, first drying and first roasting in sequence to obtain a loaded copper molecular sieve;

The copper salt used in the copper salt solution of configuration step (1) is copper nitrate; the ammonia-type molecular sieve is SSZ-13 molecular sieve; the molar concentration of copper element in the copper salt solution is 0.1mol/L; the ammonia-type molecular sieve The solid-to-liquid ratio g/mL of the copper salt solution is 1:100; the temperature of the first mixing and stirring is 60°C and the time is 6h; the temperature of the first roasting is 600°C and the time is 6h; this example Step (2) is performed twice to ensure that the copper loading can reach 4%.

(2) The copper-loaded molecular sieve obtained in step (1) and the solvent are mixed and stirred for a second time, and then subjected to platinum salt treatment, evaporation, second drying and second roasting in sequence to obtain the molecular sieve catalyst;

The solvent in step (2) is deionized water; the temperature of the second mixing and stirring is 25°C, and the time is 0.5h; the platinum salt treatment is to add platinum salt to the material obtained by the second mixing and stirring, and the platinum salt is added to the material obtained by the second mixing and stirring. The platinum salt used in the salt treatment is tetraammine platinum nitrate, and the mass ratio of the copper molecular sieve loaded in the platinum salt treatment to the platinum element in the platinum salt used is 1:0.01; the evaporation includes a water bath rotary evaporation, and the temperature is 60°C; The temperature of the second roasting is 550°C and the time is 6 hours.

Example 3

This embodiment provides a molecular sieve catalyst for ammonia purification of ammonia internal combustion engines. The molecular sieve catalyst includes active components in terms of mass percentage: 1.5% platinum and 4% copper, and the balance is a molecular sieve carrier.

The preparation method is as follows:

(1) Use the ion exchange method to first mix and stir the ammonia-type molecular sieve and the copper salt solution, and then perform solid-liquid separation, first drying and first roasting in sequence to obtain a loaded copper molecular sieve;

The copper salt used in the copper salt solution of configuration step (1) is copper nitrate; the ammonia-type molecular sieve is SSZ-13 molecular sieve; the molar concentration of copper element in the copper salt solution is 0.1mol/L; the ammonia-type molecular sieve The solid-to-liquid ratio g/mL of the copper salt solution is 1:100; the temperature of the first mixing and stirring is 60°C and the time is 6h; the temperature of the first roasting is 500°C and the time is 6h; this example Step (2) is performed twice to ensure that the copper loading can reach 4%.

(2) The copper-loaded molecular sieve obtained in step (1) and the solvent are mixed and stirred for a second time, and then subjected to platinum salt treatment, evaporation, second drying and second roasting in sequence to obtain the molecular sieve catalyst;

The solvent in step (2) is deionized water; the temperature of the second mixing and stirring is 25°C, and the time is 0.5h; the platinum salt treatment is to add platinum salt to the material obtained by the second mixing and stirring, and the platinum salt is added to the material obtained by the second mixing and stirring. The platinum salt used in the salt treatment is chloroplatinic acid, and the mass ratio of the copper molecular sieve loaded in the platinum salt treatment to the platinum element in the platinum salt used is 1:0.015; the evaporation includes a water bath rotary evaporation, and the temperature is 60°C; The temperature of the second roasting is 530°C and the time is 6 hours.

Application example 1

Embodiment 1 was used to catalytically purify the ammonia gas appearing in the simulated ammonia internal combustion engine, and a gradient temperature test was conducted on the temperature of the catalytic purification. The temperatures were 150°C, 175°C, 200°C, 225°C, 250°C, 275°C, 300°C, 325°C. ℃, 350℃, 375℃ and 400℃;

The water content in the exhaust gas of the ammonia internal combustion engine is 10% in terms of volume percentage;

The total gas flow rate in the exhaust gas of the ammonia internal combustion engine is 500mL/min, and the air velocity is 200000h ^-1 .

The concentration of ammonia gas formed during the operation of the ammonia internal combustion engine is 1000 ppm.

The indicators of the purified gas at 200°C are shown in Table 1, and those under other temperature conditions are shown in Figure 1.

Application example 2

Embodiment 1 was used to catalytically purify the ammonia gas appearing in the simulated ammonia internal combustion engine, and the temperature of the catalytic purification was 200°C;

The water content in the exhaust gas of the ammonia internal combustion engine is 10% in terms of volume percentage;

The total gas flow rate in the exhaust gas of the ammonia internal combustion engine is 500mL/min, and the air velocity is 200000h ^-1 .

The concentration of ammonia gas formed during the operation of the ammonia internal combustion engine is 500 ppm.

The indicators of the purified gas are detailed in Table 1.

Application example 3

Embodiment 1 was used to catalytically purify the ammonia gas appearing in the simulated ammonia internal combustion engine, and the temperature of the catalytic purification was 200°C;

The water content in the exhaust gas of the ammonia internal combustion engine is 10% in terms of volume percentage;

The total gas flow rate in the exhaust gas of the ammonia internal combustion engine is 500mL/min, and the air velocity is 200000h ^-1 .

The concentration of ammonia formed during the operation of the ammonia internal combustion engine is 200 ppm.

The indicators of the purified gas are detailed in Table 1.

Application example 4

Embodiment 1 is used to catalytically purify ammonia gas appearing in a simulated ammonia internal combustion engine, and the temperature of the catalytic purification is 200°C;

The water content in the exhaust gas of the ammonia internal combustion engine is 5% in terms of volume percentage;

The total gas flow rate in the exhaust gas of the ammonia internal combustion engine is 500mL/min, and the air velocity is 200000h ^-1 .

The concentration of ammonia gas formed during the operation of the ammonia internal combustion engine is 550 ppm.

The indicators of the purified gas are detailed in Table 1.

Application example 5

Embodiment 2 was used to catalytically purify the ammonia gas appearing in the simulated ammonia internal combustion engine, and the temperature of the catalytic purification was 200°C;

The water content in the exhaust gas of the ammonia internal combustion engine is 5% in terms of volume percentage;

The total gas flow rate in the exhaust gas of the ammonia internal combustion engine is 500mL/min, and the air velocity is 200000h ^-1 .

The concentration of ammonia gas formed during the operation of the ammonia internal combustion engine is 550 ppm.

The indicators of the purified gas are detailed in Table 1.

Application example 6

Embodiment 3 was used to catalytically purify the ammonia gas appearing in the simulated ammonia internal combustion engine, and the temperature of the catalytic purification was 200°C;

The water content in the exhaust gas of the ammonia internal combustion engine is 5% in terms of volume percentage;

The total gas flow rate in the exhaust gas of the ammonia internal combustion engine is 500mL/min, and the air velocity is 200000h ^-1 .

The concentration of ammonia gas formed during the operation of the ammonia internal combustion engine is 550 ppm.

The indicators of the purified gas are detailed in Table 1.

Table 1

Conversion rate/% Selectivity/% Application example 1 97.1 93.3 Application example 2 91.2 94.7 Application example 3 98.9 97.4 Application example 4 99.9 90.6 Application example 5 99.8 82.2 Application example 6 98.1 87.1

It can be seen from the results of the above application examples that by introducing the active components platinum and copper, the synergistic effect of metals can be used to simultaneously improve the low-temperature activity and nitrogen selectivity of the catalyst ammonia oxidation reaction. The precious metal platinum has high activity and can ensure the smooth progress of the ammonia oxidation reaction at low temperatures, solving the problem of significant reduction in catalytic performance of current ammonia oxidation catalysts in high-humidity and low-temperature environments.

It is stated that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements of the selected components of the present invention, addition of auxiliary components, selection of specific modes, etc., all fall within the protection scope and disclosure scope of the present invention.

The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, a variety of simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that each of the specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner without conflict. In order to avoid unnecessary repetition, the present invention combines various possible combinations. The combination method will not be further explained.

In addition, any combination of various embodiments of the present invention can also be carried out. As long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Claims (16)

1. A method for preparing a molecular sieve catalyst for ammonia oxidation in an ammonia internal combustion engine, characterized in that the preparation method includes the following steps: (1) Use the ion exchange method to first mix and stir ammonia-type molecular sieves and copper salt solutions, and then perform solid-liquid separation, first drying and first roasting in sequence to obtain copper-loaded molecular sieves; (2) The copper-loaded molecular sieve obtained in step (1) and the solvent are mixed and stirred for the second time, and then subjected to platinum salt treatment, evaporation, second drying and second roasting in sequence to obtain the moisture content in percent by volume. A molecular sieve catalyst for ammonia oxidation with an ammonia content of 5-15%, with a nitrogen selectivity of 82-95% in ammonia oxidation; The temperature of the first mixing and stirring in step (1) is 40-60°C; the temperature of the first roasting is 400-650°C; the ammonia-type molecular sieve includes ZSM-5 molecular sieve, SSZ-13 molecular sieve or Y molecular sieve. One or a combination of at least two; the molar concentration of copper element in the copper salt solution is 0.05-2mol/L; the solid-liquid ratio g/mL of the ammonia molecular sieve and copper salt solution is 1:(80- 150); The platinum salt treatment in step (2) is to add platinum salt to the material obtained by the second mixing and stirring; the second roasting temperature is 400-650°C; the copper molecular sieve loaded in the platinum salt treatment and the platinum in the platinum salt used are The mass ratio of elements is 1:(0.005-0.02). 2. The preparation method according to claim 1, characterized in that the copper salt used in the copper salt solution in configuring step (1) includes one or at least two of copper chloride, copper sulfate, copper nitrate or copper acetate. combination. 3. The preparation method according to claim 2, characterized in that the copper salt used in the copper salt solution in configuring step (1) is copper nitrate. 4. The preparation method according to claim 1, characterized in that the first mixing and stirring time in step (1) is 4-8 hours. 5. The preparation method according to claim 1, characterized in that the first roasting time in step (1) is 4-8 hours. 6. The preparation method of claim 1, wherein the solvent in step (2) includes water. 7. The preparation method according to claim 1, characterized in that the temperature of the second mixing and stirring in step (2) is 20-40°C. 8. The preparation method according to claim 1, characterized in that the second mixing and stirring time in step (2) is 0.5-3h. 9. The preparation method according to claim 1, wherein the platinum salt used in the platinum salt treatment in step (2) includes 1 of tetraammine platinum nitrate, chloroplatinic acid, platinum chloride or ammonium chloroplatinate. species or a combination of at least 2 species. 10. The preparation method according to claim 9, characterized in that the platinum salt used in the platinum salt treatment in step (2) is tetraammine platinum nitrate. 11. The preparation method of claim 1, wherein the evaporation in step (2) includes water bath rotary evaporation. 12. The preparation method according to claim 1, characterized in that the evaporation temperature in step (2) is 50-80°C. 13. The preparation method according to claim 1, characterized in that the second roasting time in step (2) is 3-7 hours. 14. The preparation method according to any one of claims 1-13, characterized in that the preparation method includes the following steps: (1) Use the ion exchange method to first mix and stir ammonia-type molecular sieves and copper salt solutions, and then perform solid-liquid separation, first drying and first roasting in sequence to obtain copper-loaded molecular sieves; The copper salt used in the copper salt solution in the configuration step (1) includes one or a combination of at least two of copper chloride, copper sulfate, copper nitrate or copper acetate; the ammonia type molecular sieve includes ZSM-5 molecular sieve, SSZ- One or a combination of at least two of 13 molecular sieves or Y molecular sieves; the molar concentration of copper element in the copper salt solution is 0.05-2mol/L; the solid-liquid ratio of the ammonia molecular sieve and copper salt solution is g/mL is 1: (80-150); the temperature of the first mixing and stirring is 40-60°C, and the time is 4-8h; the temperature of the first roasting is 400-650°C, and the time is 4-8h; (2) The copper-loaded molecular sieve obtained in step (1) and the solvent are mixed and stirred for a second time, and then subjected to platinum salt treatment, evaporation, second drying and second roasting in sequence to obtain the molecular sieve catalyst; The solvent in step (2) includes water; the temperature of the second mixing and stirring is 20-40°C, and the time is 0.5-3h; the platinum salt treatment is to add platinum salt to the material obtained by the second mixing and stirring, the The platinum salt used in the platinum salt treatment includes one or a combination of at least two of tetraammine platinum nitrate, chloroplatinic acid, platinum chloride or ammonium chloroplatinate. The copper molecular sieve loaded in the platinum salt treatment and the platinum salt used The mass ratio of platinum elements is 1:(0.005-0.02); the evaporation includes water bath rotary evaporation, the temperature is 50-80°C; the second roasting temperature is 400-650°C, and the time is 3-7h. 15. A molecular sieve catalyst obtained by the preparation method according to any one of claims 1-14, characterized in that the molecular sieve catalyst includes active components in terms of mass percentage: platinum 0.5-2% and copper 2- 4%, the balance is molecular sieve carrier. 16. The use of a molecular sieve catalyst obtained by the preparation method according to any one of claims 1 to 14, characterized in that the use includes using the molecular sieve catalyst to catalytically purify the tail gas formed during the operation of an ammonia internal combustion engine; The temperature of the catalytic purification is 175-500°C; The water content in the exhaust gas of the ammonia internal combustion engine is 5-15% in terms of volume percentage; The concentration of ammonia in the exhaust gas formed by the ammonia internal combustion engine is 300-1500 ppm.