WO2019140750A1

WO2019140750A1 - Method for preparing high-iron content fe-zsm-5 molecular sieve

Info

Publication number: WO2019140750A1
Application number: PCT/CN2018/077820
Authority: WO
Inventors: 陈文勇; 周旭晨; 刘环昌; 明曰信; 彭立
Original assignee: 山东齐鲁华信高科有限公司
Priority date: 2018-01-19
Filing date: 2018-03-02
Publication date: 2019-07-25
Also published as: CN108217681B; CN108217681A

Abstract

A method for preparing a high-iron content Fe-ZSM-5 molecular sieve. Under a condition where no organic amine template is used, an appropriate silicon source, alkali source, aluminium source, and iron source are first selected, a seed crystal is added, and a hydrothermal synthesis method is adopted; crystallization at a constant temperature is performed to obtain a slurry of an NaFe-ZSM-5 molecular sieve a framework of which contains iron, the slurry is subjected to exchange with an acidic solution and waching to obtain low-sodium Fe-ZSM-5, and the low-sodium Fe-ZSM-5 is uniformly mixed with an inorganic iron salt solution; exchange, washing and drying at constant temperatures and then roasting are performed to obtain high-iron content hydrogen-type Fe-ZSM-5. No organic amine template is used, a plurality of inorganic silicon sources, aluminium sources, and iron sources, and a seed crystal are adopted to prepare the Fe-ZSM-5 molecular sieve with an iron content higher than 6% by means of the hydrothermal synthesis method and ion exchange. Industrialization production is easily achieved, and no environment pollution problem due to removal of a template will occur. The iron content is increased on the surface of a molecular sieve by means of a single ion exchange method, so that the iron element in and out of the framework of the molecular sieve can be uniformly distributed, and the relative crystallization degree of the Fe-ZSM-5 molecular sieve can be kept to a maximum degree.

Description

Method for preparing high-iron content Fe-ZSM-5 molecular sieve

Technical field

The invention relates to the technical field of molecular sieves, in particular to a preparation method of high-iron content Fe-ZSM-5 molecular sieve.

Background technique

Metal modified zeolite catalyst is important class of selective catalytic reduction of nitrogen oxides in the catalyst, the catalyst metal such as iron and copper modified zeolite prepared exhibits good activity in terms of selectivity denitration, NO _x conversion rate Up to 95% higher, the metal modified molecular sieve catalyst currently used for selective denitration includes Cu-ZSM-5, Cu-SSZ-13, Fe-ZSM-5, Fe-BETA, Fe-ZSM-5, etc., Cu -ZSM-5 in the reaction feed containing 2% of water vapor to seriously affect their catalytic activity, and automobile exhaust contains up to 10% to 16% of water vapor, a great impact on the conversion of NO _x; and SSZ-13 Molecular sieves such as BETA are introduced into the templating agent during the synthesis process, and the crystallization period is long. The cost of the metal modified molecular sieve is high, which limits the application and promotion of the metal modified molecular sieve. Studies have shown that, Fe-ZSM-5 catalyst in the case of SO ₂ and H ₂ O in the presence of NO _x to maintain a high conversion rate, have good hydrothermal stability and sulfur tolerance. Therefore, the research on low-cost Fe-ZSM-5 molecular sieve has become a development trend for selective denitrification of automobile exhaust.

At present, Fe-ZSM-5 molecular sieve mainly has the following problems in the synthesis: First, the use of templating agent, due to the high cost of the stencil agent, greatly increases the production cost of the molecular sieve, and environmental pollution during the process of removing the stencil agent. Second, the current Fe-ZSM-5 molecular sieve synthesized by the in-situ synthesis method has a low iron content, generally below 3%, and generally requires at least two exchanges of repeated calcination to make Fe-ZSM-5. The molecular sieve has a high iron content, but repeated calcination easily causes the crystal skeleton defect of the Fe-ZSM-5 molecular sieve, affecting the crystallinity of the product and ultimately affecting its catalytic performance. Third, the existing solid impregnation method can be improved. The iron content of Fe-ZSM-5 molecular sieve, but its active site is mostly present on the surface of the molecular sieve, resulting in low catalytic activity of the molecular sieve.

Summary of the invention

In order to solve the above problems, an object of the present invention is to provide a method for preparing a high iron content Fe-ZSM-5 molecular sieve.

In order to achieve the above object, the present invention is achieved by the following technical solutions:

A method for preparing a high-iron content Fe-ZSM-5 molecular sieve comprises the following steps:

1 Dissolve the aluminum source and the iron source in water, and aging at 70-90 ° C for 2 to 3 hours to obtain a B solution; wherein the aluminum source, the iron source and the water are added in a molar ratio of aluminum ions, iron ions and water. Calculated as 1:0.1～1:100～200; the aluminum source is aluminum sulfate, aluminum chloride or aluminum nitrate; the iron source is ferrous sulfate, ferrous chloride, iron sulfate, ferric chloride or ferric nitrate ;

2 The silicon source, the alkali source and the seed crystal are beaten uniformly in water to obtain a solution A; wherein the molar ratio of each component in the solution A to the aluminum source in the step 1 in terms of Al ₂ O ₃ is SiO ₂ :Na ₂ O: Al ₂ O ₃ :H ₂ O=40-120:8-12:1:200-1900; the quality of the seed crystal is 0.2 to 2 times the mass of the aluminum source in the step 1; the silicon source is white carbon black, silica gel And/or water glass; the alkali source is sodium hydroxide; the seed crystal is ZSM-5 molecular sieve;

3, while stirring, the solution B obtained in step 1 is dropped into the solution A obtained in step 2, and the temperature is raised to 85 to 95 ° C for pre-crystallization for 2 to 3 hours, and then the temperature is raised to 160 to 200 ° C for 5 to 48 hours to obtain a slurry. Wherein the stirring speed is 80 to 200 rpm;

4, the slurry obtained in step 3 is filtered, the filter cake is washed with 5 to 10 times by weight of water, and then 5 to 10 times by weight of the acidic solution is exchanged to remove sodium ions, and washed by suction to obtain a low-sodium Fe-ZSM-5 molecular sieve; Wherein the acidic solution is an ammonium sulfate solution or an ammonium chloride solution having a mass fraction of 10 to 15%;

5 The low-sodium Fe-ZSM-5 molecular sieve obtained in the step 4, the inorganic iron salt and the water are uniformly mixed in a mass ratio of 1:0.3 to 1:4-10, and exchanged at 70-95 ° C for 1 to 10 hours, and washed by filtration. The low sodium high iron Fe-ZSM-5 molecular sieve filter cake is obtained, and the obtained low sodium high iron Fe-ZSM-5 molecular sieve filter cake is dried and calcined at 350 to 500 ° C for 2 to 4 hours to obtain a high iron content Fe-ZSM-5 molecular sieve. The inorganic iron salt is ferrous sulfate, ferrous chloride or iron sulfate.

Preferably, the source of iron is ferrous sulfate or ferrous chloride.

Preferably, the aluminum source is aluminum chloride.

Preferably, the source of silicon is water glass.

Preferably, the temperature of crystallization in step 3 is 165 to 185 ° C for 12 to 24 hours.

Preferably, the acidic solution is a 12% by mass ammonium sulfate solution.

Preferably, the inorganic iron salt is ferrous sulfate or ferrous chloride.

Preferably, the step of preparing the low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake in the step 5 is: mixing the low-sodium Fe-ZSM-5 molecular sieve obtained in the step 4, the inorganic iron salt and the water according to the mass ratio of 1:0.8:8. Uniform, exchanged at 90 ° C for 6 hours, filtered and washed to obtain a low sodium high iron Fe-ZSM-5 molecular sieve cake.

A preferred preparation method comprises the following steps:

1 The aluminum source and the iron source are dissolved in water and aged at 75 ° C for 3 hours to obtain a B solution; wherein the aluminum source, the iron source and the water are added in a ratio of aluminum ion, iron ion and water in a molar ratio of 1: 0.6: 160; the aluminum source is aluminum chloride; the iron source is ferrous chloride;

2 The silicon source, the alkali source and the seed crystal are beaten uniformly in water to obtain a solution A; wherein the molar ratio of each component in the solution A to the aluminum source in the step 1 in terms of Al ₂ O ₃ is SiO ₂ :Na ₂ O: Al ₂ O ₃ :H ₂ O=100:10:1:1000; the mass of the seed crystal is 1 times the mass of the aluminum source in step 1; the silicon source is water glass; the alkali source is sodium hydroxide; The seed crystal is ZSM-5 molecular sieve;

3 Under stirring, the solution B obtained in step 1 is dropped into the solution A obtained in step 2, and the temperature is raised to 90 ° C for pre-crystallization for 2.5 hours, and then the temperature is raised to 180 ° C for 15 hours to obtain a slurry in which the stirring speed is 120 rpm. /Minute;

4 The slurry obtained in the step 3 is filtered, the filter cake is washed with 8 times by weight of water, and then 6 times by weight of the acidic solution is exchanged to remove the sodium ions, and washed with suction to obtain a low-sodium Fe-ZSM-5 molecular sieve; wherein the acidic solution is of mass a 12% ammonium sulfate solution;

5 The low-sodium Fe-ZSM-5 molecular sieve obtained in step 4, the inorganic iron salt and water were mixed and beaten according to the mass ratio of 1:0.8:8, and exchanged at 90 ° C for 6 hours, and washed by filtration to obtain low-sodium high-iron Fe-ZSM- 5 molecular sieve filter cake, the obtained low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake was dried and calcined at 400 ° C for 3 hours to obtain a high-iron content Fe-ZSM-5 molecular sieve; the inorganic iron salt was ferrous chloride.

The present invention has the following advantages over the prior art:

The preparation method of the high-iron content Fe-ZSM-5 molecular sieve of the invention is prepared by hydrothermal synthesis without using an organic amine stencil agent, using various organic silicon sources, aluminum sources, iron sources and seed crystals, and then preparing by ion exchange method. The hydrogen type Fe-ZSM-5 molecular sieve with iron content of more than 6% has less operation steps, is easy to realize industrial production, and does not cause the problem of environmental pollution caused by removing the stenciling agent; the present application adopts a single ion exchange method. The iron content is increased on the surface of the molecular sieve, so that the distribution of iron elements inside and outside the molecular sieve framework is uniform, and the relative crystallinity of the Fe-ZSM-5 molecular sieve is retained to the utmost extent;

The preparation method of the present application has a short synthesis time. Since only one ion exchange and one calcination process have been carried out, the iron content can be uniformly distributed inside and outside the molecular sieve framework, and the relative crystallinity of the molecular sieve is high, and the method solves the existing water. In the thermal synthesis method, the relative crystallinity of the molecular sieve is high but the iron content is not high; the use of the ion exchange method to increase the iron content is avoided, but the repeated calcination causes the molecular sieve skeleton to be dealuminated and the lattice collapses, resulting in a decrease in the relative crystallinity of the product. Solving the problem that the iron content of the existing immersion precipitation method is only distributed on the surface of the molecular sieve;

The invention provides a preparation method of high-iron content Fe-ZSM-5 molecular sieve from synthesis to modification, high iron content and uniform distribution, high molecular sieve relative crystallinity, low cost, few process steps, easy operation and low production cost. It has less environmental pollution and is suitable for large-scale production. It has important practical significance for the promotion of Fe-ZSM-5 in the selective denitration of automobile exhaust.

DRAWINGS

1 is an XRD spectrum of ZSM-5 molecular sieve and Fe-ZSM-5 molecular sieve P1 in Example 4;

2 is a NH ₃ -TPD spectrum of ZSM-5 molecular sieve and Fe-ZSM-5 molecular sieve P2 in Example 4;

3 is an XRD spectrum of ZSM-5 molecular sieve and Fe-ZSM-5 molecular sieve P3 in Example 5;

4 is a NH ₃ -TPD spectrum of ZSM-5 molecular sieve and Fe-ZSM-5 molecular sieve P4 in Example 5.

Detailed ways

The object of the present invention is to provide a method for preparing a high-iron content Fe-ZSM-5 molecular sieve, which is achieved by the following technical solutions:

2 The silicon source, the alkali source and the seed crystal are beaten uniformly in water to obtain a solution A; wherein the molar ratio of each component in the solution A to the aluminum source in the step 1 in terms of Al ₂ O ₃ is SiO ₂ :Na ₂ O: Al ₂ O ₃ :H ₂ O=40-120:8-12:1:200-1900; the quality of the seed crystal is 0.2 to 2 times the mass of the aluminum source in the step 1; the silicon source is white carbon black, silica gel And/or water glass; the alkali source is sodium hydroxide; the seed crystal is ZSM-5 molecular sieve or Fe-ZSM-5 molecular sieve;

4, the slurry obtained in step 3 is filtered, the filter cake is washed with 5 to 10 times by weight of water, and then 5 to 10 times by weight of an acidic solution is exchanged to remove sodium ions, and washed by suction to obtain a low-sodium Fe-ZSM-5 molecular sieve; The acidic solution is an ammonium sulfate solution or an ammonium chloride solution having a mass fraction of 10 to 15%; 5 the low sodium Fe-ZSM-5 molecular sieve obtained in the step 4, the inorganic iron salt and the water are in a mass ratio of 1:0.3 to 1:4 to 10 Mix and beat evenly, exchange at 70-95 ° C for 1 to 10 hours, filter and wash to obtain low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake, and obtain the low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake after drying at 350 ~ Calcination at 500 ° C for 2 to 4 hours to obtain a high iron content Fe-ZSM-5 molecular sieve; the inorganic iron salt is ferrous sulfate, ferrous chloride or iron sulfate.

Preferably, the source of iron is ferrous sulfate or ferrous chloride.

Preferably, the aluminum source is aluminum chloride.

Preferably, the source of silicon is water glass.

Preferably, the acidic solution is a 12% by mass ammonium sulfate solution.

Preferably, the inorganic iron salt is ferrous sulfate or ferrous chloride.

A preferred preparation method comprises the following steps:

4 The slurry obtained in the step 3 is filtered, the filter cake is washed with 8 times by weight of water, and then 6 times by weight of the acidic solution is exchanged to remove the sodium ions, and washed with suction to obtain a low sodium Fe-ZSM-5 molecular sieve; wherein the acidic solution is of mass a 12% ammonium sulfate solution;

The invention is further described below in conjunction with specific embodiments.

In the embodiment of the present invention, the water content of the white carbon black is 12 wt%; the modulus of the water glass is 3.2, which means that the molar ratio of silicon oxide to sodium oxide in the aqueous solution is 3.2; the specific gravity of the water glass under the modulus is about 1.257. g/ml, the silica content was 250 g/L, the sodium oxide content was 80 g/L, and the remaining components were considered to be water.

Example 1

1 34.24 kg of aluminum sulfate and 4.0 kg of iron sulfate were dissolved in 360 kg of water, and aged at 70 ° C for 2 hours to obtain a B solution;

2 waxing 240kg of silica, 64kg of sodium hydroxide and 6.85kg of seed crystals in 360kg of water to obtain A solution;

3, while stirring, the solution B obtained in step 1 was dropped into the solution A obtained in step 2, and the temperature was raised to 85 ° C for 2 hours, and then heated to 160 ° C for 5 hours to obtain a slurry in which the stirring speed was 80 rpm. /Minute;

4 The slurry obtained in step 3 is filtered, the filter cake is washed with 5 times by weight of water, and then exchanged with 5 times weight of the acidic solution to remove sodium ions, and washed by suction to obtain a low-sodium Fe-ZSM-5 molecular sieve; wherein the acidic solution is a 10% ammonium sulfate solution with a mass fraction;

5 Take 100kg of the low-sodium Fe-ZSM-5 molecular sieve obtained in step 4, 30kg of ferrous sulfate and 400kg of water, mix and beat evenly, exchange at 70 ° C for 1 hour, filter and wash to obtain low-sodium high-iron Fe-ZSM-5 molecular sieve cake. The obtained low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake was dried and calcined at 350 ° C for 2 hours to obtain a high-iron Fe-ZSM-5 molecular sieve.

Example 2

1 13.33 kg of aluminum chloride and 12.68 kg of ferrous chloride are dissolved in 360 kg of water, and aged at 90 ° C for 3 hours to obtain a B solution;

2 water glass (modulus 3.2) 852.9kg, white carbon black 625.50kg and seed crystal 26.66kg in water 1710kg evenly to obtain A solution;

3, while stirring, the solution B obtained in step 1 was dropped into the solution A obtained in step 2, and the temperature was raised to 95 ° C for pre-crystallization for 3 hours, and then the temperature was raised to 200 ° C for 48 hours to obtain a slurry in which the stirring speed was 200 rpm. /Minute;

4, the slurry obtained in step 3 is filtered, the filter cake is washed with 10 times by weight of water, and then 10 times by weight of acidic solution is exchanged to remove sodium ions, and washed by suction to obtain a low-sodium Fe-ZSM-5 molecular sieve; wherein the acidic solution is of mass a 15% ammonium chloride solution;

5 Take 100kg of low-sodium Fe-ZSM-5 molecular sieve obtained in step 4, 100kg of ferrous chloride and 1000kg of water, mix and beat evenly, exchange at 95 °C for 10 hours, filter and wash to obtain low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake The obtained low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake was dried and calcined at 500 ° C for 4 hours to obtain a high-iron Fe-ZSM-5 molecular sieve.

Example 3

1 37.51 kg of aluminum nitrate and 18 kg of ferric nitrate were dissolved in 432 kg of water, and aged at 85 ° C for 2.5 hours to obtain a B solution;

2 175kg white carbon black, 175kg silica gel, 40kg sodium hydroxide and 45kg of seed crystals are evenly beaten in 450kg of water to obtain A solution;

3, while stirring, the solution B obtained in step 1 was dropped into the solution A obtained in step 2, and the temperature was raised to 90 ° C for pre-crystallization for 2.5 hours, and then the temperature was raised to 180 ° C for 20 hours to obtain a slurry in which the stirring speed was 100 rpm. /Minute;

4, the slurry obtained in step 3 is filtered, the filter cake is washed with 6 times by weight of water, and then 7 times by weight of acidic solution is exchanged to remove sodium ions, and washed by suction to obtain low sodium Fe-ZSM-5 molecular sieve; wherein the acidic solution is mass a 12% ammonium sulfate solution;

5 Take 100kg of the low-sodium Fe-ZSM-5 molecular sieve obtained in step 4, 60kg of ferric sulfate and 500kg of water, mix and beat evenly, exchange at 80 ° C for 3 hours, filter and wash to obtain low-sodium high-iron Fe-ZSM-5 molecular sieve cake, The obtained low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake was dried and calcined at 380 ° C for 3 hours to obtain a high-iron Fe-ZSM-5 molecular sieve.

Example 4

1 34.24 kg of aluminum sulfate and 44.5 kg of ferrous sulfate were dissolved in 540 kg of water, and aged at 80 ° C for 2.5 hours to obtain a solution B;

2 60 kg of silica gel, 72 kg of sodium hydroxide and 51.36 kg of seed crystals are uniformly beaten in water 1080 kg to obtain A solution;

3, while stirring, the solution B obtained in step 1 was dropped into the solution A obtained in step 2, and the temperature was raised to 90 ° C for 2 hours, and then heated to 175 ° C for 12 hours to obtain a slurry in which the stirring speed was 100 rpm. /Minute;

4 The slurry obtained in the step 3 is filtered, the filter cake is washed with 6 times by weight of water, and then ion exchange is performed to remove sodium ions by adding 8 times by weight of the acidic solution, and washed by suction to obtain a low sodium Fe-ZSM-5 molecular sieve P1; The solution is a 14% ammonium sulfate solution;

5 Take 100kg of the low-sodium Fe-ZSM-5 molecular sieve obtained in step 4, 50kg of ferrous sulfate and 600kg of water, mix and beat evenly, exchange at 90 °C for 5 hours, filter and wash to obtain low-sodium high-iron Fe-ZSM-5 molecular sieve cake. The obtained low-sodium high-iron Fe-ZSM-5 molecular sieve cake was dried and calcined at 350 ° C for 3 hours to obtain a high-iron Fe-ZSM-5 molecular sieve P2.

It can be seen from the XRD analysis of Fig. 1 that the diffraction peak positions of P1 (low sodium Fe-ZSM-5) and ZSM-5 are completely identical, and there are no diffraction peaks of other crystal forms, which indicates that the ZSM-5 type product is synthesized. Since the bond length of iron is longer than that of aluminum, iron is introduced into the molecular sieve lattice, so that the cell spacing becomes slightly larger, so the diffraction peaks with 2θ of 8.8° and 22-25° are slightly shifted to the right. It is indicated that the synthesized Fe-ZSM-5 molecular sieve has iron entering the crystal lattice. The relative crystallinity of P1 and P2 is relatively high, 98% and 87%, respectively. It can be seen from the NH ₃ -TPD spectrum of FIG. 2 that the Fe-ZSM-5 molecular sieve P2 synthesized by the present invention replaces the ZSM-5 molecular sieve SiAlOH bond by the iron element entering the molecular sieve skeleton compared with the ZSM-5 molecular sieve. H, the acidity of both strong acid and weak acid decreased, indicating that the iron element is evenly distributed in the molecular sieve.

Example 5

1 13.33 kg of aluminum chloride and 12.6 kg of ferrous chloride are dissolved in 288 kg of water, and aged at 75 ° C for 3 hours to obtain a B solution;

2 water glass (modulus 3.2) 1136.8kg, silica gel 60.08kg and crystal seed 13.33kg in water 900kg evenly to obtain A solution;

4 The slurry obtained in the step 3 is filtered, the filter cake is washed with 8 times by weight of water, and then exchanged with 6 times by weight of the acidic solution to remove sodium ions, and washed by suction to obtain a low sodium Fe-ZSM-5 molecular sieve P3; wherein the acidic solution a 14% ammonium chloride solution;

5 100kg of the low-sodium Fe-ZSM-5 molecular sieve obtained in step 4, 80kg of ferrous chloride and 800kg of water are mixed and beaten according to the mass ratio of 1:0.8:8, and exchanged at 90 °C for 6 hours, filtered and washed to obtain low-sodium high-iron The Fe-ZSM-5 molecular sieve cake was dried, and the obtained low-sodium high-iron Fe-ZSM-5 molecular sieve cake was dried and calcined at 400 ° C for 3 hours to obtain a high-iron Fe-ZSM-5 molecular sieve P4.

It can be known from the XRD analysis of Fig. 3 that the diffraction peak positions of the Fe-ZSM-5 molecular sieve P4 and the ZSM-5 molecular sieve are completely identical, and there is no diffraction peak of other crystal forms, which indicates that the ZSM-5 type product is synthesized. Since the bond length of iron is longer than that of aluminum, iron is introduced into the molecular sieve lattice, so that the cell spacing becomes slightly larger, so the diffraction peaks with 2θ of 8.8° and 22-25° are slightly shifted to the right. It is indicated that the synthesized Fe-ZSM-5 molecular sieve has iron entering the crystal lattice, indicating that the Fe-ZSM-5 molecular sieve with iron skeleton is synthesized. The relative crystallinity of P3 and P4 is relatively high, 96% and 84%, respectively. It can be seen from the NH ₃ -TPD spectrum of FIG. 4 that the P4 synthesized by the present invention replaces the H in the SiAlOH bond of the ZSM-5 molecular sieve by the iron element entering the molecular sieve skeleton, so that the strong acid and the weak acid are compared with the ZSM-5 molecular sieve. The acidity decreases, indicating that iron is evenly distributed in the molecular sieve.

The high-iron content Fe-ZSM-5 molecular sieves obtained in Examples 1 to 5 were tested for iron content, relative crystallinity and selective catalytic denitration performance, wherein the selective catalytic denitration performance was a high-iron content Fe-ZSM-5 molecular sieve. The test is carried out by fully grinding the tablet and filling it in a fixed bed reactor at a concentration of 900*10 ^-6 ppm, an ethylene/NO molar ratio of 1:4, an oxygen volume fraction of 5%, and a water vapor volume fraction of 10%. The inert gas N ₂ was a carrier gas, the total flow rate was 100 ml/min, and the space velocity was 6000 h ^-1 . The conversion of NO at 270 ° C to 350 ° C was tested. The results are shown in Table 1.

Table 1 Test results of iron content, relative crystallinity and selective catalytic denitration performance of the high iron content Fe-ZSM-5 molecular sieve obtained in Examples 1 to 5

	Fe ₂O ₃/％ Fe ₂ O ₃ /%	相对结晶度Relative crystallinity	NO转化率/％NO conversion rate /%
实施例1Example 1	6.126.12	8989	98.1298.12
实施例2Example 2	6.146.14	8989	98.2598.25
实施例3Example 3	6.826.82	8787	99.1499.14
实施例4Example 4	6.946.94	8686	99.2299.22
实施例5Example 5	7.127.12	8484	99.3499.34

Claims

A method for preparing a high-iron content Fe-ZSM-5 molecular sieve, comprising: the following steps:

1 Dissolve the aluminum source and the iron source in water, and aging at 70-90 ° C for 2 to 3 hours to obtain a B solution; wherein the aluminum source, the iron source and the water are added in a molar ratio of aluminum ions, iron ions and water. Calculated as 1:0.1～1:100～200; the aluminum source is aluminum sulfate, aluminum chloride or aluminum nitrate; the iron source is ferrous sulfate, ferrous chloride, iron sulfate, ferric chloride or ferric nitrate ;

2 The silicon source, the alkali source and the seed crystal are beaten uniformly in water to obtain a solution A; wherein the molar ratio of each component in the solution A to the aluminum source in the step 1 in terms of Al 2 O 3 is SiO 2 :Na 2 O: Al 2 O 3 :H 2 O=40-120:8-12:1:200-1900; the quality of the seed crystal is 0.2 to 2 times the mass of the aluminum source in the step 1; the silicon source is white carbon black, silica gel And/or water glass; the alkali source is sodium hydroxide; the seed crystal is ZSM-5 molecular sieve;

3, while stirring, the solution B obtained in step 1 is dropped into the solution A obtained in step 2, and the temperature is raised to 85 to 95 ° C for pre-crystallization for 2 to 3 hours, and then the temperature is raised to 160 to 200 ° C for 5 to 48 hours to obtain a slurry. Wherein the stirring speed is 80 to 200 rpm;

4, the slurry obtained in step 3 is filtered, the filter cake is washed with 5 to 10 times by weight of water, and then 5 to 10 times by weight of an acidic solution is exchanged to remove sodium ions, and washed by suction to obtain a low-sodium Fe-ZSM-5 molecular sieve; The acidic solution is an ammonium sulfate solution or an ammonium chloride solution having a mass fraction of 10 to 15%;

5 The low-sodium Fe-ZSM-5 molecular sieve obtained in the step 4, the inorganic iron salt and the water are uniformly mixed in a mass ratio of 1:0.3 to 1:4-10, and exchanged at 70-95 ° C for 1 to 10 hours, and washed by filtration. The low sodium high iron Fe-ZSM-5 molecular sieve filter cake is obtained, and the obtained low sodium high iron Fe-ZSM-5 molecular sieve filter cake is dried and calcined at 350 to 500 ° C for 2 to 4 hours to obtain a high iron content Fe-ZSM-5 molecular sieve. The inorganic iron salt is ferrous sulfate, ferrous chloride or iron sulfate.
The method for preparing a high-iron content Fe-ZSM-5 molecular sieve according to claim 1, wherein the iron source is ferrous sulfate or ferrous chloride.
The method for preparing a high-iron content Fe-ZSM-5 molecular sieve according to claim 1, wherein the aluminum source is aluminum chloride.
The method for preparing a high-iron content Fe-ZSM-5 molecular sieve according to claim 1, wherein the silicon source is water glass.
The method for preparing a high-iron content Fe-ZSM-5 molecular sieve according to claim 1, wherein:

The crystallization temperature in the step 3 is 165 to 185 ° C for 12 to 24 hours.
The method for preparing a high-iron content Fe-ZSM-5 molecular sieve according to claim 1, wherein the acidic solution is a ammonium sulfate solution having a mass fraction of 12%.
The method for preparing a high-iron content Fe-ZSM-5 molecular sieve according to claim 1, wherein the inorganic iron salt is ferrous sulfate or ferrous chloride.
The method for preparing a high-iron content Fe-ZSM-5 molecular sieve according to claim 1, wherein the step of preparing the low-sodium high-iron Fe-ZSM-5 molecular sieve cake in step 5 is: the low-sodium Fe obtained in step 4 -ZSM-5 molecular sieve, inorganic iron salt and water were mixed and beaten according to a mass ratio of 1:0.8:8, ion exchanged at 90 ° C for 6 hours, and washed by filtration to obtain a low sodium high iron Fe-ZSM-5 molecular sieve filter cake.
The method for preparing a high-iron content Fe-ZSM-5 molecular sieve according to claim 1, comprising the steps of:

1 The aluminum source and the iron source are dissolved in water and aged at 75 ° C for 3 hours to obtain a B solution; wherein the aluminum source, the iron source and the water are added in a ratio of aluminum ion, iron ion and water in a molar ratio of 1: 0.6: 160; the aluminum source is aluminum chloride; the iron source is ferrous chloride;

2 The silicon source, the alkali source and the seed crystal are beaten uniformly in water to obtain a solution A; wherein the molar ratio of each component in the solution A to the aluminum source in the step 1 in terms of Al 2 O 3 is SiO 2 :Na 2 O: Al 2 O 3 :H 2 O=100:10:1:1000; the mass of the seed crystal is 1 times the mass of the aluminum source in step 1; the silicon source is water glass; the alkali source is sodium hydroxide; The seed crystal is ZSM-5 molecular sieve;

3 Under stirring, the solution B obtained in step 1 is dropped into the solution A obtained in step 2, and the temperature is raised to 90 ° C for pre-crystallization for 2.5 hours, and then the temperature is raised to 180 ° C for 15 hours to obtain a slurry in which the stirring speed is 120 rpm. /Minute;

4 The slurry obtained in the step 3 is filtered, the filter cake is washed with 8 times by weight of water, and then 6 times by weight of the acidic solution is added to exchange and remove sodium ions, and washed with suction to obtain a low-sodium Fe-ZSM-5 molecular sieve; wherein the acidic solution is 12% ammonium sulfate solution;

5 The low-sodium Fe-ZSM-5 molecular sieve obtained in step 4, the inorganic iron salt and water were mixed and beaten according to the mass ratio of 1:0.8:8, and exchanged at 90 ° C for 6 hours, and washed by filtration to obtain low-sodium high-iron Fe-ZSM- 5 molecular sieve filter cake, the obtained low-sodium high-iron Fe-ZSM-5 molecular sieve filter cake was dried and calcined at 400 ° C for 3 hours to obtain a high-iron content Fe-ZSM-5 molecular sieve; the inorganic iron salt was ferrous chloride.