CN109569289B

CN109569289B - LaSrBO4Denitration method by directly decomposing NO under catalysis of catalyst

Info

Publication number: CN109569289B
Application number: CN201811624804.3A
Authority: CN
Inventors: 周继承; 韩雪; 彭康; 徐文涛; 游志敏
Original assignee: Xiangtan University
Current assignee: Xiangtan University
Priority date: 2018-12-28
Filing date: 2018-12-28
Publication date: 2021-06-15
Anticipated expiration: 2038-12-28
Also published as: CN109569289A

Abstract

The invention provides LaSrBO₄The denitration method by catalytic direct decomposition of NO by the catalyst comprises the following steps: 1) filling LaSrBO in the reaction tube of the microwave reactor device₄The catalyst forms a microwave catalytic reaction bed; 2) the waste gas containing NO passes through a microwave catalytic reaction bed to generate gas-solid catalytic reaction under the combined action of the temperature of the microwave catalytic reaction bed, a microwave field and the catalyst, wherein NO is directly decomposed into N₂And O₂. The method is a novel method for directly decomposing NO by microwave catalytic reaction, does not need to add reducing agents such as ammonia gas, ammonium salt, methane and the like, and is also used for firstly decomposing LaSrBO₄The catalyst is used for the reaction of directly catalyzing and decomposing NO by microwave; the method has the characteristics of simple process, low cost, no secondary pollution and the like.

Description

LaSrBO4Denitration method by directly decomposing NO under catalysis of catalyst

Technical Field

The invention relates to the technical field of catalytic denitration, and particularly relates to LaSrBO₄A method for denitration by directly decomposing NO under the catalysis of a catalyst.

Background

With the rapid development of economy, the consumption of energy is increasing. At present, fossil energy such as petroleum and natural gas is still the main energy in China. The NOx in the exhaust gas from fossil energy combustion causes serious environmental pollution. Therefore, elimination of NOx pollution has become an important issue in the field of environmental protection.

NO direct separationThe solution has economical property and does not consume NH₃、CH₄Reducing agents such as CO, and the like, and no secondary pollution, are considered to be the most attractive methods. Direct decomposition of NO to N₂And O₂It is fully feasible to reach 99% in the thermodynamic range, but the activation energy of the reaction is as high as 364kJ/mol, so that the decomposition of NO is essentially a matter of exploring its kinetics, i.e. to find a suitable catalyst and catalytic method for the reaction. LaSrBO is studied by Zhujunjiang et al₄The conventional reaction mode of the catalyst directly catalyzes and decomposes NO, and the catalyst is found to be used for LaSrNiO only at 850 DEG C₄The conversion rate of NO of the catalyst can reach 94.7 percent, however, the catalyst for LaSrCuO₄The conversion of catalyst NO was only 34.3% for LaSrCoO₄The catalyst NO conversion was only 20.3%. Thus, LaSrBO₄The effect of the catalyst for directly catalyzing the denitration of NO is not ideal.

The inventors of the present application and the group of subjects thereof have been devoted to research in the field of microwave catalytic denitration, as the following patents are previously filed by the applicant.

Patent CN201110451237.8 provides a denitration method for directly decomposing NO by microwave catalysis, in which a reaction tube filled with a catalyst is installed in a microwave field to form a reaction bed layer, and the reaction tube is made of quartz glass or other wave-transparent materials; when the flue gas/waste gas containing NO passes through the reaction bed layer, gas-solid catalytic reaction is carried out under the combined action of a microwave field and a catalyst at a set reaction temperature; the method is characterized in that: the catalyst in the reaction bed layer is a copper molecular sieve catalyst Cu-ZSM-5; the temperature of the catalyst bed layer for the reaction is 100-450 ℃, and preferably 280-380 ℃. When the treated gas passes through the microwave catalytic reaction bed, the copper molecular sieve Cu-ZSM-5 is used as a catalyst to directly catalyze and decompose nitric oxide in the gas to convert the nitric oxide into nitrogen and oxygen, and the nitrogen oxide is removed. The invention has the advantages of high direct decomposition conversion rate, low energy consumption, energy saving, environmental protection, no reducing agent consumption, low operation cost and the like.

Patent application CN 201410736555.2 provides a catalytic denitration method, which is performed in a microwave field, and the catalyst used is a composite metal oxide containing nickel, and the composite metal oxide containing nickel is a Cu-Ni composite metal oxide or a Ni-Fe composite metal oxide. Preferably, when the molar amount of nickel in the nickel-containing composite metal oxide is 1, the molar amount of copper or iron is 0.4 to 2.5. The reaction for directly decomposing NO by microwave catalysis has NO secondary pollution, and has the advantages of simple process, convenient operation, easy control, high NO removal efficiency (the NO conversion rate can reach 98.9%), strong oxygen resistance, low operation temperature, energy conservation, environmental protection and low operation cost.

The patent application CN 201610883390.0 firstly provides a method for microwave direct catalytic decomposition of NO, which comprises the step of using a catalyst containing Cu-SAPO-34 to microwave-catalyze NO in NO-containing gas to directly decompose NO into N at the temperature of 120-400 DEG C₂And O₂. The invention introduces the combination of microwave and a specific denitration catalyst, and carries out reaction and catalytic decomposition on the Cu-SAPO-34 catalyst in a microwave field to obtain good effect. In particular Cu-SAPO-34, together with oxides of transition or valence-changing metal elements, form MeO_xthe-Cu-SAPO-34 mixed catalyst has high activity at 100-400 ℃ when directly catalyzing and decomposing NO. The method has the advantage of efficiently and directly decomposing NO, and has the characteristics of simple process, low cost, NO secondary pollution and the like.

The invention correspondingly obtains the method for directly catalytically decomposing NO by microwaves with good reaction effect, but the technical personnel in the field can make more efforts in the development and application of the catalyst so as to further reduce the cost of the catalyst, improve the conditions of catalytic reaction and improve the conversion rate of NO, so that the direct decomposition of NO by microwave catalysis can be applied to the field of industrial denitration as early as possible.

Disclosure of Invention

The invention aims to provide LaSrBO₄A denitration method for directly decomposing NO by catalyst catalysis aims at solving the problems in the background technology.

In order to realize the purpose, the invention provides LaSrBO₄The denitration method by catalytic direct decomposition of NO by the catalyst comprises the following steps:

1) filling LaSrBO in the reaction tube of the microwave reactor device₄The catalyst forms a microwave catalytic reaction bed;

2) the waste gas containing NO passes through a microwave catalytic reaction bed to generate gas-solid catalytic reaction under the combined action of the temperature of the microwave catalytic reaction bed, a microwave field and the catalyst, wherein NO is directly decomposed into N₂And O₂。

Preferably, in the above technical solution, the LaSrBO₄The type catalyst is LaSrCuO₄、LaSrNiO₄Or LaSrCoO₄(ii) a The temperature of the catalytic reaction is 150-400 ℃; the volume content of oxygen in the NO-containing waste gas is 0.1-10%; the residence time in the microwave catalytic reaction bed is 0.5 to 10 s; the microwave frequency of the microwave field is 500-3000 MHz.

Preferably, in the above technical solution, the LaSrBO₄The catalyst is preferably LaSrCuO₄。

In the above technical scheme, preferably, the temperature of the microwave catalytic reaction bed is 250-350 ℃, and the reaction pressure is atmospheric pressure.

In the above technical solution, it is preferable that the volume content of oxygen in the NO-containing exhaust gas is 2.5 to 7.5%.

Preferably, in the above technical scheme, the residence time of the exhaust gas containing NO in the microwave catalytic reaction bed is 1-3 s.

Preferably, in the above technical solution, the LaSrBO₄The preparation method of the type catalyst comprises the following steps:

according to the catalyst LaSrBO₄Proportioning La (NO)₃)₂、Sr(NO₃)₂And B (NO)₃)₂Dissolving in deionized water; performing ultrasonic treatment for 10-30min, stirring at 40-60 deg.C for 15-60min, and mixing; adding citric acid and ethylene glycol, stirring for 15-60min, heating to 75-85 deg.C, and stirring to obtain soft gel; drying at 110-120 ℃ for more than 2 h; pre-sintering at 350 ℃ for 1-3 h under 250-.

Compared with the prior art, the invention has the following beneficial effects:

1) microwave catalytic direct decomposition of NO to N₂And O₂Simple process and no secondary pollution. By introducing microwavesField, use LaSrCuO₄、LaSrNiO₄And LaSrCoO₄The catalyst can realize high-efficiency direct decomposition of NO into N at low temperature₂And O₂。

2) Compared with LaSrCuO at the high temperature of 850 ℃ in a conventional heating field₄、LaSrNiO₄And LaSrCoO₄LaSrNiO in catalyst₄The conversion rate of the catalyst to NO is different at most, and the LaSrCuO is heated to 400 ℃ under the microwave field₄The catalyst shows the best catalytic effect. This indicates that the LaSrNiO₄And LaSrCoO₄Compared with the catalyst, LaSrCuO₄The catalyst can be better matched with microwaves and is used for catalyzing direct decomposition of NO.

3) LaSrCuO prepared by the preparation method of the invention₄、LaSrNiO₄And LaSrCoO₄The catalyst structure is more suitable for catalyzing the direct decomposition of NO under microwave.

4) The LaSrCuO of the invention₄When the catalyst is used for catalyzing direct decomposition of NO, an excellent direct NO decomposition effect can still be obtained under the condition that NO gas contains a certain amount of oxygen and/or water vapor and the reaction temperature is 250-350 ℃, which shows that the catalyst is less influenced by impurity oxygen and/or water vapor in NO raw material gas.

Detailed Description

The solution according to the invention is explained in detail below with reference to examples, but the invention can be implemented in many different ways, as defined and covered by the claims.

Example 1

Preparation of the catalyst: according to the catalyst LaSrMO₄(M ═ Ni, Co, Cu) La (NO) was added₃)₂、Sr(NO₃)₂With Ni (NO)₃)₂Or Co (NO)₃)₂Or Cu (NO)₃)₂Dissolved in 110mL of deionized water. Performing ultrasonic treatment for 20min, stirring at 50 deg.C for 30min, and mixing. Citric acid and ethylene glycol were added, and the total moles of citric acid and ethylene glycol was 1.25 times the total moles of metal ions. Stirring for 30min, heating to 80 deg.C, and stirring to obtain soft gelAnd (6) gluing. Drying was carried out overnight at 110 ℃. Presintering at 300 ℃ for 2h, calcining at 600 ℃ for 1h, and finally calcining at 900 ℃ for 8h to obtain the catalyst.

Example 2

This example examines the conversion of NO and N in different catalysts by direct microwave catalysis at different temperatures₂Selectivity of (2). In this example, the catalyst mass was 2g, the NO concentration was 1000ppm, and N was₂The flow rate of the mixed gas at the inlet is 120mL/min for balance gas, wherein the flow rate of the mixed gas containing NO is 114mL/min, O₂The flow rate was 6 mL/min. The reaction pressure is normal pressure, and the temperature of the reaction bed layer is regulated and controlled by regulating the microwave power.

TABLE 1

As can be seen from Table 1, LaSrCuO is most preferable as denitration activity₄After the temperature of the catalyst reaches 300-400 ℃, the conversion rate of NO is higher than 93.5 percent. Over the entire temperature range, N₂The selectivity of (A) is high.

Example 3

This example examines LaSrCuO₄At 300 ℃ different O₂Conversion of directly decomposed NO at concentration and product N₂Selectivity of (2). The mass of the catalyst is 2g, the concentration of NO is 1000ppm, the flow rate of the mixed gas at the inlet is 120mL/min, wherein the flow rate of oxygen is 0, 3, 6, 9 and 12mL/min, and N is₂Is the balance gas. The reaction pressure is normal pressure, and the temperature of the reaction bed layer is regulated and controlled by regulating the microwave power.

TABLE 2

O₂Concentration (%)	NO conversion (%)	N₂Selectivity (%)
			0	98.52	100.00
2.5	96.60	100.00
			5	93.68	99.83
7.5	93.30	100.00
			10	92.47	98.91

As can be seen from Table 2, O₂The concentration of (A) has little effect on the denitration reaction and has almost no effect.

Example 4

This example considers the catalyst LaSrCuO₄In the presence of water vapor, the conversion rate of NO and N are directly catalyzed by microwaves at different temperatures₂The influence of selectivity of (c). In this example, the catalyst mass was 2g, the NO concentration was 1000ppm, and the inlet gas flow rate was 120 mL/min. The reaction pressure is normal pressure, and the temperature of the reaction bed layer is regulated and controlled by regulating the microwave power.

TABLE 3

As can be seen from Table 3, in the presence of steam, the NO conversion increases slightly below 300 ℃ and decreases slightly above 300 ℃, but overall, LaSrCuO₄The catalyst still shows high catalytic activity after introducing water vapor.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. LaSrBO₄The method for denitration by catalytic direct decomposition of NO is characterized by comprising the following steps:

1) filling LaSrBO in the reaction tube of the microwave reactor device₄The catalyst forms a microwave catalytic reaction bed, the LaSrBO₄The type catalyst is LaSrCuO₄；

2) The waste gas containing NO passes through a microwave catalytic reaction bed to generate gas-solid catalytic reaction under the combined action of the temperature of the microwave catalytic reaction bed, a microwave field and the catalyst, wherein NO is directly decomposed into N₂And O₂The temperature of the catalytic reaction is 150-400 ℃;

the LaSrBO₄The preparation method of the type catalyst comprises the following steps: according to the catalyst LaSrBO₄Proportioning La (NO)₃)₂、Sr(NO₃)₂And B (NO)₃)₂Dissolving in deionized water; performing ultrasonic treatment for 10-30min, stirring at 40-60 deg.C for 15-60min, and mixing; adding citric acid and ethylene glycol, stirring for 15-60min, heating to 75-85 deg.C, and stirring to obtain soft gel; drying at 110-120 ℃ for more than 2 h; pre-sintering at 350 ℃ for 1-3 h under 250-.

2. The method of claim 1, wherein the volume content of oxygen in the NO-containing exhaust gas is 0.1-10%; the residence time in the microwave catalytic reaction bed is 0.5 to 10 s; the microwave frequency of the microwave field is 500-3000 MHz.

3. The method of claim 2, wherein the temperature of the microwave catalytic reaction bed is 250 ℃ to 350 ℃, and the reaction pressure is atmospheric pressure.

4. The method of claim 2, wherein the volume content of oxygen in the NO-containing exhaust gas is 2.5-7.5%.

5. The method of claim 2, wherein the residence time of the NO-containing exhaust gas in the microwave catalytic reaction bed is 1-3 s.