CN117919931A

CN117919931A - Purifying nitrogen-containing volatile organic compounds and NO in waste gasxIs a method and a purification system of (a)

Info

Publication number: CN117919931A
Application number: CN202211316698.9A
Authority: CN
Inventors: 杜辰昊; 陈航宁; 郑育元; 顾一丹; 许丹丹
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2022-10-26
Filing date: 2022-10-26
Publication date: 2024-04-26

Abstract

The invention discloses a method and a system for purifying nitrogen-containing volatile organic compounds and NOx in waste gas, which relate to the technical field of waste gas purification and comprise the following steps: (1) Adding free oxygen-containing gas into the waste gas containing nitrogen volatile organic compounds and NO _x, and heating the mixed gas to obtain a hot waste gas flow to be treated; (2) And (3) carrying out contact reaction on the hot exhaust gas flow to be treated and an oxidation catalyst, and removing nitrogen-containing volatile organic compounds and NO _x in the hot exhaust gas flow to be treated to obtain a purified exhaust gas flow. The invention adopts a catalytic purification method, and can simultaneously remove the nitrogen-containing volatile organic compounds and NO _x in the waste gas. By controlling parameters such as reaction temperature, gas flow rate, contact time of gas and oxidation catalyst, the purpose of high-efficiency purification of waste gas is achieved. According to the technical scheme, NO _x is reduced without adding a reducing agent, and the NO _x can be converted into N ₂ by combining an oxidation catalyst with a nitrogenous volatile organic compound in the waste gas as the reducing agent.

Description

Method and system for purifying nitrogen-containing volatile organic compounds and NO x in waste gas

Technical Field

The invention relates to the technical field of waste gas purification, in particular to a method and a purification system for purifying nitrogen-containing volatile organic compounds and NO _x in waste gas.

Background

Nitrogen-containing volatile organic compounds are a common type of pollutant in industrial exhaust gas, which is commonly found in organic exhaust gas emissions in petrochemical and pharmaceutical industries. The waste gas containing the nitrogen-containing volatile organic compounds is generally or has a malodorous smell or a high toxicity, and can have adverse effects on the environment and the physical and mental health of people. Under certain specific process conditions, nitrogen oxides (NO _x) tend to be formed with the production of nitrogen-containing volatile organic compounds. For example, in the production of carbon fibers, the exhaust gas produced contains not only HCN highly toxic substances but also a considerable amount of NO _x.

In the prior art, catalytic combustion and selective catalytic reduction are relatively common methods for treating the nitrogen-containing volatile organic compounds and the NO _x. The method comprises the steps of deeply oxidizing the nitrogen-containing volatile organic compound into NO _x, and then reducing NO _x into N ₂ by supplementing a reducing agent. For example, patent CN101362051a discloses an acrylonitrile unit tail gas treatment process. And (3) carrying out selective catalytic reduction reaction by taking the added ammonia gas as a reducing agent to reduce nitrogen oxides in the tail gas into nitrogen and water. The disadvantage is that the whole tail gas treatment process requires two reactors and an additional ammonia spraying device, the whole process flow is relatively complex, and secondary pollution caused by ammonia leakage is possibly accompanied. Patent CN 202675299U discloses an incineration treatment device for nitrogen-containing organic matters, which is to treat the nitrogen-containing organic matters by high-temperature incineration and to remove NO _x by a serial selective catalytic reduction system. It is also relatively costly and complex in process. Although patent CN 109289911a provides a method for treating nitrogen-containing organic contaminants, it still requires additional NH ₃ to be thoroughly purified in the face of NO _x.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a method and a purifying system for purifying nitrogen-containing volatile organic compounds and NO _x in waste gas. According to the invention, nitrogen-containing volatile organic compounds in the waste gas are directly utilized to reduce NO _x to N ₂, additional NH ₃ is not needed to be added as a reducing agent for reducing NO _x, and the installation of an ammonia injection grid device and selective catalytic reduction equipment are not needed, so that the problems of cost improvement and secondary pollution caused by the addition of the additional reducing agent in the prior art are avoided; the oxidation catalyst used in the reaction process does not contain any noble metal, and can obtain good simultaneous purification effect under the conditions of low material consumption and low cost.

One of the purposes of the present invention is to provide a method for purifying nitrogen-containing volatile organic compounds and NO _x in exhaust gas, comprising the following steps:

(1) Adding free oxygen-containing gas into the waste gas containing nitrogen volatile organic compounds and NO _x, and heating the mixed gas to obtain a hot waste gas flow to be treated;

(2) And (3) carrying out contact reaction on the hot exhaust gas flow to be treated and an oxidation catalyst, and removing nitrogen-containing volatile organic compounds and NO _x in the hot exhaust gas flow to be treated to obtain a purified exhaust gas flow.

Preferably, in step (1):

The content of the nitrogen-containing volatile organic compounds in the waste gas is 0.01-5%, the content of NO _x is not higher than 1%, and the content of oxygen is 1-4% by volume percent; and/or the number of the groups of groups,

The nitrogen-containing volatile organic compound is at least one of fatty amine compounds, amide compounds, aromatic amine compounds, nitrogen-containing heterocyclic compounds and cyanide compounds; and/or the number of the groups of groups,

The NO _x is at least one of NO and NO ₂、N₂ O; and/or the number of the groups of groups,

The molar ratio of the nitrogen-containing volatile organic compounds to the NO _x in the hot exhaust stream to be treated is (50-0.1): 1, a step of; and/or the number of the groups of groups,

The oxygen content of the waste gas after the free oxygen-containing gas is supplemented is 6-10%; and/or the number of the groups of groups,

The free oxygen-containing gas comprises air or other oxygen-containing gas based on protective gas, preferably air; and/or the number of the groups of groups,

The temperature of the hot exhaust gas flow to be treated is 200-400 ℃, preferably 250-350 ℃, so that the hot exhaust gas flow to be treated can reach the ignition temperature of the catalytic reaction in the subsequent contact reaction process with the oxidation catalyst, and the catalytic reaction can be performed effectively; and/or the number of the groups of groups,

Removing moisture in the waste gas through gas-liquid separation before the free oxygen-containing gas is supplemented into the waste gas; preferably, the water content in the exhaust gas is reduced to below 1% by volume.

Preferably, in step (2):

The contact reaction of the hot exhaust gas stream to be treated with the oxidation catalyst is carried out in a reactor filled with the oxidation catalyst at a reaction temperature of 300-500 ℃, preferably 350-450 ℃; and/or the contact time is 0.5 to 5s, preferably 0.5 to 1.5s; and/or the linear velocity of the hot exhaust gas stream to be treated is from 0.5 to 2m/s, preferably from 0.5 to 1.5m/s; and/or the number of the groups of groups,

The vent gas stream may be used to heat all or part of the mixed gas described in step (1).

Preferably, the oxidation catalystThe surface density ratio of the acid sites to the Lewis acid sites is 0.25 or more, preferably 0.3 or more; and/or the number of the groups of groups,

The oxidation catalyst comprises a molecular sieve, a metal oxide, a modified metal element and a binder;

the molecular sieve is at least one of MFI type, BEA type, FER type, MOR type and CHA type molecular sieves; the metal element of the metal oxide is at least one element selected from IVB, VB, VIB, VIIB, lanthanoid, rare earth element and does not comprise noble metal.

The modifying metal element is selected from at least one of group VIII, group IB element group, and lanthanide group, and does not include a noble metal.

Preferably, the molecular sieve is present in an amount of from 30 to 80%, preferably from 40 to 70%, by weight based on 100% by weight of the total weight of molecular sieve and metal oxide; the metal oxide content is 20-70%, preferably 30-60%; and/or the number of the groups of groups,

The modified metal element accounts for 0.1-10wt% of the total weight of the molecular sieve and the metal oxide based on the metal element; and/or the number of the groups of groups,

The binder content is 1-20%, preferably 5-15% of the total weight of the molecular sieve and metal oxide.

As a preferred embodiment of the present invention, the molecular sieve is one or both of BEA type molecular sieve and MFI type molecular sieve.

As a preferable aspect of the present invention, the metal element in the metal oxide is at least one selected from Ti, V, mn, fe, co, ni, cu, zr, nb, mo, la, ce, zr, pr, sm, preferably two or more of them; more preferably, the metal element is selected from two or more kinds of Ti, ni, ce, co, fe, la, cu, or three or more kinds; more preferably three or more kinds of Ti, ni, ce, co, fe, la.

As a preferable aspect of the present invention, the metal element of the modified metal is at least one selected from Ce, co, fe, cu, ni, preferably two or more of them; more preferably, the modified metal element may be Fe and/or Cu. The addition of the modified metal plays a role in modifying the molecular sieve, so that the oxidation catalyst has the function of purifying the nitrogen-containing VOCs and NO _x in the waste gas simultaneously and efficiently.

The adhesive is at least one of an organic adhesive and an inorganic adhesive; the inorganic binder is preferably one or more of alumina sol, silica sol, natural clay, water glass, silicate and pseudo-boehmite; the organic binder is preferably one or more of polyethylene oxide, polyvinyl alcohol, cellulose, acrylic acid, methyl cellulose and hydroxymethyl cellulose.

Conventional auxiliary agents, such as a structural reinforcing agent capable of improving the strength of the oxidation catalyst, can be added into the formula of the oxidation catalyst according to actual conditions, such as: the glass fiber is used in a conventional amount, and can be added by a technician according to actual conditions.

Preferably, the oxidation catalyst is prepared by the following method:

Preparing the metal oxide by a coprecipitation method, mixing the obtained metal oxide with the molecular sieve and a binder, forming, and roasting to obtain the oxidation catalyst.

Preferably, the preparation of the oxidation catalyst comprises the following specific steps:

(a) The metal oxide is prepared by adopting a coprecipitation method: adding a precipitant into the precursor solution of the metal oxide, drying the obtained precipitate, screening and roasting to obtain the metal oxide;

(b) Mixing metal oxide and/or metal oxide prepared in the step (a) with molecular sieve powder, adding adhesive, adding modified metal precursor solution, kneading, extruding, drying and roasting to obtain the oxidation catalyst.

Preferably, in step (a):

The precipitant is at least one of sodium hydroxide, sodium carbonate, ammonia water, urea and sodium bicarbonate; and/or the number of the groups of groups,

The pH value of the precursor solution of the metal oxide after adding the precipitant is 7-12; and/or the number of the groups of groups,

The precursor of the metal oxide is selected from water-soluble compounds of the metal, preferably at least one of nitrate, sulfate, hydrochloride and oxalate of the metal; and/or the number of the groups of groups,

The precursor of the modified metal element is selected from water-soluble compounds of the modified metal, preferably at least one of nitrate, sulfate, hydrochloride and oxalate of the modified metal; and/or the number of the groups of groups,

The solvent of the precursor solution is at least one of water, ethanol, methanol, glycol and glycerol; and/or the number of the groups of groups,

The molar concentration of the metal ions in the metal oxide precursor solution and the modified metal precursor solution is independently selected from 0.01-10mol/L, preferably 0.1-1mol/L; and/or the number of the groups of groups,

The drying temperature is 60-120 ℃, preferably 80-100 ℃; and/or the number of the groups of groups,

The drying time is 6-48 hours, preferably 12-24 hours; and/or the number of the groups of groups,

The powder particles obtained by sieving are 80-300 meshes, preferably 100-200 meshes; and/or the number of the groups of groups,

The roasting temperature is 300-600 ℃, preferably 400-550 ℃; and/or the number of the groups of groups,

The calcination time is 1 to 12 hours, preferably 4 to 8 hours.

Preferably, in step (b):

The weight ratio of the molecular sieve to the metal oxide is (30-80): (70-20), preferably (40-70): (60-30); and/or the number of the groups of groups,

The binder accounts for 1-20% of the total weight of the molecular sieve and the metal oxide, preferably 5-15%; and/or the number of the groups of groups,

The powder particle diameter D90 of the molecular sieve is smaller than 10 microns; and/or the number of the groups of groups,

The drying temperature is 30-120 ℃, preferably 40-60 ℃; and/or the number of the groups of groups,

The drying time is 6-72 hours, preferably 24-48 hours; and/or the number of the groups of groups,

The roasting temperature is 400-700 ℃, preferably 400-600 ℃; and/or the number of the groups of groups,

The calcination time is 1 to 12 hours, preferably 4 to 8 hours.

The shape of the oxidation catalyst after kneading and extrusion molding is not particularly limited, and may be a molded structure such as a cylinder, clover, raschig, sphere, honeycomb, or the like.

As a preferred mode of the preparation method of the oxidation catalyst of the present invention, when the metal oxide of the oxidation catalyst of the present invention includes TiO ₂, the TiO ₂ powder may be directly added and mixed in step (b) without co-precipitation in step (a), and TiO ₂ simultaneously plays a role of a co-carrier, so that the strength of the oxidation catalyst can be improved.

Another object of the present invention is to provide a purification system for purifying nitrogen-containing volatile organic compounds and NO _x in exhaust gas, comprising, in order from the upstream side on an exhaust gas passage: optionally a gas-liquid separation device, a compressor for bubbling a free oxygen-containing gas into the exhaust gas stream to be purified, a heat exchanger for preheating the exhaust gas stream to be purified and a fixed bed reactor, the discharge of which is optionally in communication with the heat exchanger; the oxidation catalyst is filled in the fixed bed reactor.

Preferably, a branch pipeline is arranged on an air inlet pipeline of the heat exchanger and is communicated with an air outlet pipeline of the heat exchanger, and an electric heater is connected in parallel.

By adopting the technical scheme, the method for catalytic purification can simultaneously remove the nitrogen-containing volatile organic compounds and NO _x in the waste gas. By controlling parameters such as reaction temperature, gas flow rate, contact time of gas and oxidation catalyst, the purpose of high-efficiency purification of waste gas is achieved. According to the technical scheme, NO _x is reduced without adding a reducing agent, and the NO _x can be converted into N ₂ by combining nitrogen-containing volatile organic compounds in the waste gas as the reducing agent through the design of the oxidation catalyst.

Drawings

FIG. 1 is a schematic diagram of a purification system of the present invention.

The device comprises a waste gas containing 1-nitrogen volatile organic compounds and NO _x, a 2-gas-liquid separation device, a 3-compressor, a 4-waste gas flow to be treated, a 5-heat exchanger, a 6-fixed bed reactor, a 7-electric heater, an 8-branch gas flow, a 9-waste gas flow to be purified for removing moisture, a 10-waste heat gas flow, a 11-waste heat gas flow to be treated combined with the branch gas flow, and a 12-exhaust gas flow.

The waste gas 1 containing nitrogen volatile organic compounds and NO _x passes through the gas-liquid separation device 2, so that the water content in the gas is reduced, and a waste gas stream 9 to be purified for removing the water is obtained. And then, a proper amount of air is blown into the waste gas flow 9 to be purified, the moisture of which is removed, by utilizing the compressor 3, the waste gas flow 4 to be treated is obtained, and the waste gas flow 4 to be treated is fed into the heat exchanger 5 to be preheated, so that the waste gas flow 10 to be treated is obtained, and the requirement of the ignition temperature of the catalytic reaction is met. The gas stream after catalytic purification by means of a fixed bed reactor 6 containing oxidation catalyst is passed to a heat exchanger 5, the heat of which is used to heat the exhaust gas stream 4 to be treated. The heat exchanged exhaust stream 12 is directly vented to the atmosphere.

In order to be able to optimize the purification conditions further, in which a bypass gas stream 8 of the exhaust gas stream 4 to be treated does not pass through the heat exchanger 5, the flow rate and the temperature of the bypass gas stream 8 are controlled by the electric heater 7, so that the gas stream temperature entering the fixed-bed reactor 6 filled with oxidation catalyst can be controlled effectively to optimize the progress of the reaction. For example, if the temperature of the air flow passing through the heat exchanger 5 cannot reach the required ignition temperature, the bypass air flow 8 can be opened, a part of the exhaust air flow 4 to be treated is quickly heated by the electric heater 7 and is converged into the hot exhaust air flow 10 to be treated to increase the temperature thereof, so as to obtain the hot exhaust air flow 11 to be treated with the bypass air flow combined; if the temperature of the hot exhaust gas stream 11 to be treated, in which the bypass gas stream is incorporated, is too high, the bypass gas stream 8 can likewise be opened, so that a part of the exhaust gas stream 4 to be treated does not pass through the heat exchanger 5 and the electric heater 7 does not heat, thereby reducing the temperature of the hot exhaust gas stream 11 to be treated, in which the bypass gas stream is incorporated, entering the fixed bed reactor 6 and controlling the temperature within a suitable interval.

Detailed Description

The present invention is described in detail below with reference to the specific drawings and examples, and it is necessary to point out that the following examples are given for further illustration of the present invention only and are not to be construed as limiting the scope of the present invention, since numerous insubstantial modifications and adaptations of the invention to those skilled in the art will still fall within the scope of the present invention.

Example 1

Preparation of the oxidation catalyst:

(a) 81.75g Ni(NO₃)₂·6H₂O(0.28mol),12.5g Ce(NO₃)₃·6H₂O(0.028mol) g and 34.5g Co (NO ₃)₂·6H₂ O (0.118 mol) are dissolved in a mixed solvent of 250mL deionized water and 50mL ethanol, and are fully stirred to ensure that metal nitrate is completely dissolved, the sum of the molar concentration of Ni, ce and Co metal ions is about 1.42mol/L, then 2mol/L Na ₂CO₃ solution is dropwise added to the solution under the heating condition of 45 ℃ until the pH value of a reaction system is=10, and the solution is filtered, washed and dried for 24 hours at the temperature of 60 ℃, and finally the solution is transferred into a muffle furnace to be roasted for 120 minutes at the temperature of 450 ℃ to obtain the metal oxide.

(B) Taking an MFI type molecular sieve: 240g of ZSM-5 molecular sieve powder (molecular sieve particle size D90=9 micron), 80g of TiO ₂ powder, and 25g of metal oxide prepared in the step (a) are placed in a stirrer to be fully stirred, then transferred into a kneader, 50g of pseudo-boehmite, 2g of methylcellulose and 10g of glass fiber are added, and all materials are fully stirred for 20min. Adding the prepared solution containing 40g of Fe (NO ₃)₃·9H₂ O and 35g of Cu (150 g of NO ₃)₂·6H₂ O (molar concentration of metal ions is 1.7 mol/L)) into a kneader, fully kneading for 40min to obtain a wet blank, adopting a steel plate with a round hole with the diameter of 4mm as a mould, extruding the wet blank through an extruder to obtain a formed catalyst structure, finally drying at 40 ℃ for 28h, drying at 60 ℃ for 24h, roasting at 550 ℃ for 6h to obtain the final oxidation catalyst, wherein the modified metal in the obtained oxidation catalyst accounts for 3.24wt% of the total weight of the oxidation catalyst based on the metal element.

For the prepared oxidation catalystThe surface density ratio of the acid sites to the Lewis acid sites was determined. The testing method comprises the following steps: adsorption of infrared light with pyridine first determines the/>, oxidation catalystThe contents of acid and Lewis acid are divided by the specific surface area of the catalyst to obtain the surface density of different acid sites. The density ratio is the division of the two.

The specific surface area of the sample was tested on Micromeritics TriStar 3000,3000 instruments; of samplesThe content of acid and Lewis acid is qualitatively and quantitatively determined by pyridine adsorption infrared. The acid density of the oxidation catalyst sample is calculated as follows:

Wherein n is the content of the acid site measured, mu mol/g; s is the surface area of the sample, m ²/g.

The acid site ratio of the oxidation catalyst prepared in this example was calculated according to the above formula to be 0.45.

Example 2

(A) The procedure for the preparation of the metal oxide is as in example 1.

(B) Taking BEA type molecular sieve: and (3) placing 150g of Beta molecular sieve powder (the particle size D90=9 microns) and 100g of TiO ₂ powder in a stirrer, fully stirring 25g of metal oxide prepared in the step (a), then transferring into a kneader, adding 50g of pseudo-boehmite, 2g of methylcellulose and 10g of glass fiber, fully stirring all materials for 20min, adding 40g of prepared solution dissolved with Fe (NO ₃)₃·9H₂ O and 35g of Cu (140 g of solution of NO ₃)₂·6H₂ O (the molar concentration of metal ions is 1.7 mol/L)) into the kneader, fully kneading for 40min to obtain a wet blank, extruding a steel plate with round holes with the diameter of 4mm by adopting a die as a wet blank by adopting the extruder to obtain a molded catalyst structure, finally drying at 40 ℃ for 28h, drying at 60 ℃ for 24h, and then roasting at 550 ℃ for 6h to obtain the final oxidation catalyst, wherein the modified metal accounts for 3.91wt% of the total weight of the oxidation catalyst in the obtained oxidation catalyst.

The acid site ratio of the oxidation catalyst in this example was measured as in example 1 and found to be 0.38.

Example 3

(A) The procedure for the preparation of the metal oxide is as in example 1.

(B) Taking CHA type molecular sieve: and (3) adding prepared 155g solution (the molar concentration of metal ions is 1.7 mol/L) of solution (NO ₃)₃·9H₂ O and 35g Cu) dissolved with Fe (NO ₃)₂·6H₂ O) into a kneader for fully kneading for 40min to obtain a wet blank, extruding a steel plate with a round hole with the diameter of 4mm through an extruder to obtain a formed catalyst structure, finally, drying at 40 ℃ for 28h, drying at 60 ℃ for 24h, roasting at 550 ℃ for 6h to obtain the final oxidation catalyst, wherein the modified metal in the obtained oxidation catalyst accounts for 3.52wt% of the total weight of the oxidation catalyst.

The acid site ratio of the oxidation catalyst in this example was measured as in example 1 and found to be 0.35.

Example 4

(A) Taking 81.75gNi (NO ₃)₂·6H₂O,12.5g Ce(NO₃)₃·6H₂ O and 34.5g Co (NO ₃)₂·6H₂ O are dissolved in a mixed solvent of 50mL deionized water and 25mL ethanol), fully stirring to ensure that metal nitrate is completely dissolved, adding 100mL (about 2.13mol/100 mL) of urea aqueous solution containing 5 times of the molar quantity of metal ions to the total molar quantity of metal ions, stirring and refluxing the mixture at 90 ℃ for 6 hours, filtering and washing the obtained product after the reaction is finished, drying the product at 60 ℃ for 24 hours, and finally transferring the product into a muffle furnace for roasting at 450 ℃ for 120 minutes to obtain the metal oxide.

(B) The oxidation catalyst was prepared in the same manner as in example 1, and the modified metal in the obtained oxidation catalyst was 3.24wt% based on the total weight of the oxidation catalyst based on the metal element thereof.

The acid site ratio of the oxidation catalyst in this example was measured as in example 1 and found to be 0.42.

Example 5

(A) Taking 81.75g of Ni (NO ₃)₂·6H₂O,12.5g Ce(NO₃)₃·6H₂ O and 34.5g of Co (NO ₃)₂·6H₂ O are dissolved in a mixed solvent of 50mL of deionized water and 25mL of ethanol) and stirring fully to completely dissolve metal nitrate, then dropwise adding 2mol/L NaOH solution into the solution under the heating condition of 45 ℃ until the pH value of a reaction system is=10, filtering, washing, drying at 60 ℃ for 24 hours, and finally transferring into a muffle furnace to bake for 120 minutes at 450 ℃ to obtain the metal oxide.

(B) Taking an MFI type molecular sieve: 240g of ZSM-5 molecular sieve powder (molecular sieve particle size D90=9 micron), 80g of TiO ₂ powder, and 25g of metal oxide prepared in the step (a) are placed in a stirrer to be fully stirred, then transferred into a kneader, 50g of silica sol, 2g of methylcellulose and 10g of glass fiber are added, and all materials are fully stirred for 20min. Adding the prepared 150g solution (the molar concentration of metal ions is 1.7 mol/L) dissolved with 40g Fe (NO ₃)₃·9H₂ O and 35g Cu (NO ₃)₂·6H₂ O) into a kneader, fully kneading for 40min to obtain a wet blank, adopting a steel plate with a round hole with the diameter of 4mm as a mould, extruding the wet blank through the extruder to obtain a formed catalyst structure, finally drying at 40 ℃ for 28h, drying at 60 ℃ for 24h, roasting at 550 ℃ for 6h to obtain the final oxidation catalyst, wherein the modified metal in the obtained oxidation catalyst accounts for 3.16wt% of the total weight of the oxidation catalyst based on the metal elements.

The acid site ratio of the oxidation catalyst in this example was measured as in example 1 and found to be 0.28.

Example 6

(A) 112.4g Fe ₂(SO₄)₃·9H₂O(0.2mol),37.3g CeCl₃ (0.1 mol) and 3.25g La (NO ₃)₃ (0.01 mol) are dissolved in a mixed solvent of 800mL deionized water and 200mL ethanol, and the mixed solvent is fully stirred to enable metal salts to be fully dissolved, the sum of the molar concentration of three metal ions is 0.31mol/L, then 1mol/L NaOH solution is dropwise added to the solution under the condition of heating at 45 ℃ until the pH value of a reaction system is 12, and the solution is dried for 24 hours at 60 ℃ after filtering and washing, and finally the solution is transferred into a muffle furnace to be roasted for 300 minutes at 550 ℃ to obtain metal oxides.

(B) Taking an MFI type molecular sieve: 100g of ZSM-5 molecular sieve powder (molecular sieve particle size D90=9 microns), 150g of TiO ₂ powder, and 20g of metal oxide prepared in the step (a) are placed in a stirrer to be fully stirred, then transferred into a kneader, 50g of natural clay, 2g of polyvinyl alcohol and 10g of glass fiber are added, and all materials are fully stirred for 20min. Adding the prepared 150g solution (the molar concentration of metal ions is 1.23 mol/L) dissolved with 30g Fe (NO ₃)₃·9H₂ O and 25g Cu (NO ₃)₂·6H₂ O) into a kneader, fully kneading for 40min to obtain a wet blank, adopting a steel plate with a round hole with the diameter of 4mm as a mould, extruding the wet blank through the extruder to obtain a formed catalyst structure, finally drying at 40 ℃ for 28h, drying at 60 ℃ for 24h, roasting at 550 ℃ for 6h to obtain the final oxidation catalyst, wherein the modified metal in the obtained oxidation catalyst accounts for 4.09wt% of the total weight of the oxidation catalyst based on the metal elements.

The acid site ratio of the oxidation catalyst in this example was measured as in example 1 and found to be 0.32.

Example 7

(A) The procedure for the preparation of the metal oxide is as in example 1.

(B) Taking an MFI type molecular sieve: 240g of ZSM-5 molecular sieve powder (molecular sieve particle size D90=9 micron), 80g of TiO ₂ powder, and 25g of metal oxide prepared in the step (a) are placed in a stirrer to be fully stirred, then transferred into a kneader, 50g of pseudo-boehmite, 2g of methylcellulose and 10g of glass fiber are added, and all materials are fully stirred for 20min. Adding prepared solution containing 10g Ni (NO ₃)₃·6H₂ O and 8g Co (150 g of NO ₃)₂·6H₂ O (molar concentration of metal ions is 0.44 mol/L)) into a kneader, fully kneading for 40min to obtain a wet blank, adopting a steel plate with a round hole with the diameter of 4mm as a mould, extruding the wet blank through an extruder to obtain a formed catalyst structure, finally drying at 40 ℃ for 28h, drying at 60 ℃ for 24h, roasting at 550 ℃ for 6h to obtain the final oxidation catalyst, wherein the modified metal in the obtained oxidation catalyst accounts for 0.88wt% of the total weight of the oxidation catalyst based on the metal element.

Example 8

(A) The procedure for the preparation of the metal oxide is as in example 1.

(B) Taking an MFI type molecular sieve: 240g of ZSM-5 molecular sieve powder (molecular sieve particle size D90=9 micron), 80g of TiO ₂ powder, and 25g of metal oxide prepared in the step (a) are placed in a stirrer to be fully stirred, then transferred into a kneader, 50g of pseudo-boehmite, 2g of methylcellulose and 10g of glass fiber are added, and all materials are fully stirred for 20min. Adding the prepared solution containing 80g of Cu (NO ₃)₃·6H₂ O and 60g of Ce (150 g of NO ₃)₃·6H₂ O (the molar concentration of metal ions is 3.35 mol/L)) into a kneader, fully kneading for 40min to obtain a wet blank, adopting a steel plate with a round hole with the diameter of 4mm as a mould, extruding the wet blank through an extruder to obtain a formed catalyst structure, finally drying at 40 ℃ for 28h, drying at 60 ℃ for 24h, roasting at 550 ℃ for 6h to obtain the final oxidation catalyst, wherein the modified metal in the obtained oxidation catalyst accounts for 9.1wt% of the total weight of the oxidation catalyst based on the metal element.

Example 9

The method for purifying nitrogen-containing volatile organic compounds and NO _x in the waste gas comprises the following steps:

The purification system shown in FIG. 1 was employed, in which the pyridine concentration in the exhaust gas stream 4 to be treated obtained after the compressor 3 had been blown with a proper amount of air was 1000ppm, the NO _x concentration was 300ppm, the O ₂ concentration was 8% by volume, and the H ₂ O content was 0.5% by volume. The gas stream was fed into the fixed-bed reactor 6 at a volumetric flow rate of 10Nm ³/h and a linear velocity of 0.6m/s, and the contact reaction time of the hot exhaust gas stream to be treated with the oxidation catalyst was 1s.

The oxidation catalyst used in this example was the oxidation catalyst prepared in example 1, and the loading was 1L and the volume space velocity (based on the total amount of gas passing through the oxidation catalyst) was 10000h ^-1. The inlet temperature of the exhaust gas stream before entering the fixed bed reactor 6 was 300℃and the concentration of NO _x at the outlet after 48 hours of operation was 11.5ppm, the removal efficiency of NO _x was 96.2%. The pyridine content is less than 1ppm as measured by GC-IMS, and the purification efficiency is more than 99%.

Example 10

The purification system shown in FIG. 1 was employed, in which, in the exhaust gas stream 4 to be treated obtained after the compressor 3 had been blown with a proper amount of air, the concentration of triethylamine was 500ppm, the concentration of NO _x was 300ppm, the concentration of O ₂ was 8% by volume and the H ₂ O content was 0.5% by volume. The gas stream was fed into the fixed-bed reactor 6 at a volumetric flow rate of 10Nm ³/h and a linear velocity of 0.6m/s, and the contact reaction time of the hot exhaust gas stream to be treated with the oxidation catalyst was 1s.

The oxidation catalyst used in this example was the oxidation catalyst prepared in example 3, and the loading was 1L and the volume space velocity (based on the total amount of gas passing through the oxidation catalyst) was 10000h ^-1. The inlet temperature of the exhaust gas stream before entering the fixed bed reactor 6 was 320℃and the concentration of NO _x at the outlet after 48 hours of operation was 21.3ppm, the removal efficiency of NO _x was 92.9%. The triethylamine content is less than 1ppm as measured by GC-FID, and the purification efficiency is more than 99%.

Example 11

The purification system shown in FIG. 1 was employed, in which the concentration of formamide, the concentration of NO _x, the concentration of O ₂, the volume fraction of 8% and the H ₂ O content of 1% were 300ppm, 500ppm, and the volume fraction of the exhaust gas stream 4 to be treated, which was obtained after the compressor 3 had been blown with an appropriate amount of air. The gas stream was fed into the fixed-bed reactor 6 at a volumetric flow rate of 10Nm ³/h and a linear velocity of 0.6m/s, and the contact reaction time of the hot exhaust gas stream to be treated with the oxidation catalyst was 1s.

The oxidation catalyst used in this example was the oxidation catalyst prepared in example 4, and the loading was 1L and the volume space velocity (based on the total amount of gas passing through the oxidation catalyst) was 10000h ^-1. The inlet temperature of the exhaust gas stream before entering the fixed bed reactor 6 (the temperature of the hot exhaust gas stream to be treated) was 280℃and the concentration of NO _x at the outlet after 48 hours of operation was 21.8ppm, the removal efficiency of NO _x was 95.7%. The formamide content is 1.8ppm by GC-FID measurement, and the purification efficiency is more than 99%.

Example 12

The purification system shown in FIG. 1 was employed, in which the acetonitrile concentration was 1000ppm, the NO _x concentration was 500ppm, the O ₂ concentration was 8% by volume and the H ₂ O content was 0.5% by volume in the exhaust gas stream 4 to be treated obtained after the compressor 3 had been purged with an appropriate amount of air. The gas stream was fed into the fixed-bed reactor 6 at a volumetric flow rate of 10Nm ³/h and a linear velocity of 0.6m/s, and the contact reaction time of the hot exhaust gas stream to be treated with the oxidation catalyst was 1s.

The oxidation catalyst used in this example was the oxidation catalyst prepared in example 5, and the loading was 1L and the volume space velocity (based on the total amount of gas passing through the oxidation catalyst) was 10000h ^-1. The inlet temperature of the exhaust gas stream before entering the fixed bed reactor 6 was 320℃and the concentration of NO _x at the outlet after 48 hours of operation was 42.7ppm, the removal efficiency of NO _x was 91.5%. The acetonitrile content was 2.8ppm as determined by GC-FID, and the purification efficiency was more than 99%.

Example 13

The only difference compared to example 9 is: the concentration of O ₂ in the exhaust gas stream 4 to be treated, which is obtained after the compressor 3 has been inflated with a suitable amount of air, is controlled to 6%, the remaining parameters being unchanged.

In this example, the oxidation catalyst of example 1 was used as well, and the reaction parameters were the same as in example 1. The concentration of NO _x at the outlet after 48h of operation was 18.7ppm and the removal efficiency of NO _x was 93.8%. The pyridine content was 3.6ppm as determined by GC-MS, and the purification efficiency was greater than 99%.

Example 14

The only difference compared to example 9 is: the concentration of O ₂ in the exhaust gas stream 4 to be treated, which is obtained after the compressor 3 has been inflated with a suitable amount of air, is controlled to 10%, the remaining parameters being unchanged.

In this example, the oxidation catalyst of example 1 was used as well, and the reaction parameters were the same as in example 1. The concentration of NO _x at the outlet after 48h of operation was 21.3ppm and the removal efficiency of NO _x was 92.9%. The pyridine content is less than 1ppm as measured by GC-MS, and the purification efficiency is more than 99%.

Claims

1. A method for purifying nitrogen-containing volatile organic compounds and NO _x in waste gas comprises the following steps:

2. The method according to claim 1, characterized in that in step (1):

The temperature of the hot exhaust gas stream to be treated is 200-400 ℃, preferably 250-350 ℃; and/or the number of the groups of groups,

3. The method according to claim 1, characterized in that in step (2):

the reaction temperature of the contact reaction of the hot exhaust gas flow to be treated and the oxidation catalyst is 300-500 ℃, preferably 350-450 ℃; and/or the contact time is 0.5 to 5s, preferably 0.5 to 1.5s; and/or the linear velocity of the hot exhaust gas stream to be treated is from 0.5 to 2m/s, preferably from 0.5 to 1.5m/s; and/or the number of the groups of groups,

4. The method according to claim 1, characterized in that:

the oxidation catalyst The surface density ratio of the acid sites to the Lewis acid sites is 0.25 or more, preferably 0.3 or more; and/or the number of the groups of groups,

The molecular sieve is at least one of MFI type, BEA type, FER type, MOR type and CHA type molecular sieves; the metal element of the metal oxide is at least one element selected from IVB, VB, VIB, VIIB, lanthanoid and rare earth elements, and does not comprise noble metal;

5. The method according to claim 1, characterized in that:

The content of the molecular sieve is 30-80%, preferably 40-70% based on 100% by weight of the total weight of the molecular sieve and the metal oxide; the metal oxide content is 20-70%, preferably 30-60%; and/or the number of the groups of groups,

6. The method according to claim 1, characterized in that:

The molecular sieve is one or two of BEA type molecular sieve and MFI type molecular sieve; and/or the number of the groups of groups,

The metal element of the metal oxide is selected from at least one of Ti, V, mn, fe, co, ni, cu, zr, nb, mo, la, ce, zr, pr, sm, preferably two or more of them; and/or the number of the groups of groups,

The metal element of the modified metal is selected from at least one, preferably two or more of Ce, co, fe, cu, ni;

7. The process according to any one of claims 4 to 6, characterized in that the oxidation catalyst is prepared by the following method:

8. The method according to claim 7, characterized in that the preparation of the oxidation catalyst comprises the following specific steps:

9. The method for purifying nitrogen-containing volatile organic compounds and NO _x in exhaust gas according to claim 8, wherein in step (a):

The molar concentration of metal ions in the metal oxide precursor solution and the modified metal precursor solution is independently selected from 0.01-10mol/L, preferably 0.1-1mol/L; and/or the number of the groups of groups,

The calcination time is 1 to 12 hours, preferably 4 to 8 hours.

10. The method of claim 8, wherein in step (b):

The calcination time is 1 to 12 hours, preferably 4 to 8 hours.

11. A purification system for purifying a nitrogen-containing volatile organic compound and NO _x in an exhaust gas according to any one of claims 1 to 10, characterized in that the purification system comprises, in order from the upstream side on the exhaust gas passage: optionally a gas-liquid separation device, a compressor for bubbling a free oxygen-containing gas into the exhaust gas stream to be purified, a heat exchanger for preheating the exhaust gas stream to be purified and a fixed bed reactor, the discharge of which is optionally in communication with the heat exchanger; the oxidation catalyst is filled in the fixed bed reactor.

12. The purification system of claim 11, wherein: the air inlet pipeline of the heat exchanger is provided with a branch pipeline which is communicated with the air outlet pipeline of the heat exchanger, and an electric heater is connected in parallel.