CN103111322A - A kind of preparation method of monolithic honeycomb molecular sieve catalyst for N2O decomposition - Google Patents

Abstract

A method for preparing an integral honeycomb molecular sieve catalyst for N ₂ O decomposition relates to the field of honeycomb molecular sieve structured catalysts for N ₂ O direct decomposition, and is suitable for the treatment of waste gas containing high concentration N ₂ O such as adipic acid tail gas treatment. In the present invention, the active molecular sieve component with a particle size of less than 100 meshes is fully mixed with the binder, the mass ratio of the active molecular sieve to the binder is 2:1-4:1, and an extrusion aid is added. The extrusion aid is composed of active molecular sieve and adhesive The total amount of the agent is based on the mass content of 2.5-3%, and the mass content benchmarks mentioned below are the same; the mass content of the pore-forming agent is 0-3%, and it is uniformly mixed in a mixer; the mixed powder is mixed with the peptizer and Water is put into a kneader and kneaded to make a billet, which is aged and then extruded, and then dried and roasted. The catalyst of the invention has a relatively low plasticity of 0.1-0.35, good plasticity, smooth extrusion process, and is not easily deformed after extrusion.

Description

A kind of preparation method of monolithic honeycomb molecular sieve catalyst for N2O decomposition

technical field

The invention relates to a honeycomb molecular sieve structured catalyst for direct decomposition of _N2O and a forming method thereof; it is suitable for the treatment of waste gas containing high concentration of _N2O such as adipic acid tail gas treatment.

Background technique

Nitrous oxide, also known as nitrous oxide, commonly known as laughing gas, not only has a strong greenhouse effect, but also seriously destroys the ozone layer. Man-made emissions of N ₂ O include tail gas from chemical production, such as the tail gas from the production of adipic acid and nitric acid, and coal-fired fluidized bed combustion; it also includes the combustion tail gas of motor vehicles; the combustion of biomass and waste also includes _N2O will be produced. With the enhancement of people's awareness of environmental protection, the treatment of N ₂ O has been highly valued by the majority of industrial production industries and environmental protection organizations.

The direct decomposition technology of N ₂ O is that N ₂ O is decomposed into nitrogen and oxygen under the action of a catalyst. At present, the catalysts used for the direct decomposition of N ₂ O include metal oxide catalysts, hydrotalcite-derived composite compounds, and modified molecular sieve catalysts such as Co-ZSM-5 molecular sieves (US5171553). The treatment of industrial adipic acid tail gas requires the catalyst to have the characteristics of high mechanical strength, low resistance, and small pressure drop, so the monolithic structure of the catalyst is more conducive to its application.

The preparation of monolithic catalysts can be divided into two ways: self-forming and immobilization. Immobilization is to fix the catalyst powder on the surface of a carrier (ceramic, metal, etc.) with a certain structure and mechanical strength by coating or other methods. CN101204665A discloses a monolithic molecular sieve catalyst synthesized in situ on a cordierite carrier and used for the direct decomposition of _N2O , the mass of the molecular sieve is 5%-30% of the mass of the monolithic catalyst; CN102688687 discloses a method for decomposing nitric acid tail gas N The new process of ₂ O, the catalyst used is a honeycomb monolithic catalyst made of zeolite supported on ceramic materials, the content of each active ingredient is: Fe ₂ O ₃ 1-2%, Al ₂ O ₃ 0-2%, SiO ₂ 2-19%, ceramic material 75-90%. Self-shaping is the process of applying mechanical external force to the catalyst to make it have a suitable geometric shape and mechanical strength. CN101905145 introduces a method for forming a molecular sieve honeycomb material, which is formed by mixing molecular sieves, binders and dilute acids and then kneading them.

Contents of the invention

The purpose of the present invention is to provide a honeycomb molecular sieve structured catalyst for the direct decomposition of _N2O , characterized in that the honeycomb monolithic catalyst consists of active components, binders, peptizers, extrusion aids, Formed by extrusion such as pore-forming agent.

Another object of the present invention is to provide a method for preparing a honeycomb structured catalyst for direct decomposition of N ₂ O. Its specific preparation method and process steps are:

A method for preparing a monolithic honeycomb molecular sieve catalyst for _N2O decomposition, characterized in that:

Fully mix the active molecular sieve component with a particle size of less than 100 mesh and the binder, the mass ratio of the active molecular sieve to the binder is 2:1-4:1, add an extrusion aid, and the extrusion aid consists of the active molecular sieve and the binder. The mass content is 2.5-3% as the basis, and the mass content reference mentioned below is the same; the mass content of the pore-forming agent is 0-3%, and it is uniformly mixed in the mixer; the active molecular sieve component is modified by Fe or Co Molecular sieve; molecular sieve is β molecular sieve, ZSM-5 molecular sieve or MCM-22 molecular sieve; Fe or Co account for 1-3% of the total mass of molecular sieve;

Put the mixed powder, peptizer and water into a kneader to knead to make a billet, the mass content of the peptizer is 6-10%, and the water mass content is 50-60%; the prepared billet is sealed with a plastic film in the Aging is carried out in an environment with a temperature lower than 25°C, and the aging time is 4-10h; then it is put into an extrusion molding machine for extrusion molding, and the extrusion pressure is 10-30MPa; the prepared honeycomb body is placed in 18-25 It is shaped and dried at ℃ for 24-48 hours, and then it is put into a drying oven for drying at a drying temperature of 100-150 ℃ and a drying time of 1-2 hours; finally, it is roasted at 550 ℃ for 4-10 hours.

The active molecular sieve component in the present invention is Fe (or Co) modified molecular sieve; the molecular sieve is β molecular sieve, ZSM-5 molecular sieve or MCM-22 molecular sieve; the modified component is iron or cobalt nitrate, oxalate; The modification method is an ion exchange method or an impregnation method. The ion exchange method is to mix iron or cobalt sources, molecular sieves, and water, and stir at 60-100° C. for 4-10 hours. The product is filtered, washed and dried, and calcined in an air atmosphere at 550° C. for 4-6 hours to obtain the active component molecular sieve. The modified components Fe and Co in the active molecular sieve used in the present invention account for 1-3% of the total mass of the molecular sieve.

Adhesive can be one or more in pseudo-boehmite, aluminum oxide, aluminate, and the present invention preferably selects as pseudo-boehmite powder; Peptizer can be one of nitric acid, tartaric acid, citric acid One or more kinds, nitric acid is preferably used in the present invention; the extrusion aid is generally scallop powder. The pore-forming agent is one or more of polyvinyl alcohol, cellulose, urea, and polyethylene glycol, and urea is preferably used in the present invention.

In order to ensure the smooth extrusion of the blank during the molding process, the plasticity of the honeycomb structured catalyst blank for the direct decomposition of N2O prepared by the present invention is 0.1-0.35.

The key step of the present invention is the aging step, and the length of the aging time will affect the plasticity of the molded blank. The aging time of the present invention has an optimum range: 4-10h. When the aging time is too short, the plasticity of the forming blank is low; when the aging time is too long, the plasticity of the forming blank also becomes low due to the loss of moisture.

The setting drying time in the drying step of the present invention is 24-48 hours; the drying time in a drying oven at 100-150 DEG C is 1-2 hours; the roasting temperature is 550 DEG C, and the roasting time is 4-10 hours.

The catalyst of the invention has a relatively low plasticity of 0.1-0.35, good plasticity, smooth extrusion process, and is not easily deformed after extrusion.

Description of drawings

Figure 1 shows the honeycomb structured catalyst prepared in Example 1 of the present invention.

Detailed ways

Embodiments of the present invention will be further described below in conjunction with the accompanying drawings and examples, but the present invention is not limited to the listed examples. Any other known changes within the protection scope of the present invention should also be included.

Example 1

Put 118g of Fe-β molecular sieve (the mass percentage of Fe ions in the modified molecular sieve is 1%), crush and sieve it, put it into the mixer with 45.92g of pseudo-boehmite, and 4.5g of celadon powder; 100g of 9% nitric acid aqueous solution is kneaded, and the kneaded sample is aged in a cool place for 6 hours. The plasticity of the billet is measured by KS-B microcomputer plasticity tester to be 0.253; the billet is put into an extrusion molding machine (the mold size is 4*4mm , wall thickness 1.5mm) After extrusion molding, it was shaped and dried at 18°C for 24 hours, and the extrusion pressure was 10MPa; after drying in a 100°C drying oven for 2h, it was roasted at a heating rate of 2°C/min, and then raised to 550°C for 6h. , to obtain the final product (accompanying drawing 1). The prepared honeycomb structure catalyst was used for the direct decomposition reaction of N ₂ O, the space velocity was 6000h ^-1 , and the concentration of N ₂ O in the feed gas was 10% (V/V, the rest was air). Under these conditions, the lowest temperature for 100% conversion of N ₂ O is 450°C.

Example 2

Put 135.59g of Fe-MCM-22 molecular sieve (the mass percentage of Fe ions in the modified molecular sieve is 1.5%) and put it into the mix with 30.61g of Al2O3, 4.125g of Sesame powder and 3g of polyvinyl alcohol Mix evenly in the machine; add 100g of tartaric acid aqueous solution with a concentration of 9% for kneading, put the kneaded sample in a cool place for aging for 10 hours, and measure the plasticity of the billet with a KS-B microcomputer plasticity tester to be 0.179; put the billet into the extrusion molding machine Medium (the mold size is 1.5*1.5mm in diameter, 1.5mm in wall thickness) after extrusion molding, it is shaped and dried for 36 hours, and the extrusion pressure is 30MPa; it is baked after drying in a 150°C drying oven for 2h, and the heating rate is 2°C/min. Rise to 550°C and roast for 4 hours to obtain the final product. The prepared honeycomb structure catalyst was used for the direct decomposition reaction of N ₂ O, the space velocity was 6000h ^-1 , and the concentration of N ₂ O in the feed gas was 10% (V/V, the rest was air). Under these conditions, the lowest temperature for 100% conversion of N ₂ O is 475°C.

Example 3

Put 127.12g of Fe-β molecular sieve (the mass percentage of Fe ions in the modified molecular sieve is 2.5%) and put it into the mixer together with 38.27g of pseudo-boehmite, 3.75g of celadon powder and 4.5g of cellulose after crushing and sieving Mix uniformly in medium; add 100g of citric acid aqueous solution with a concentration of 10% for kneading, put the kneaded sample in a cool place for aging for 4 hours, and measure the plasticity of the billet with a KS-B microcomputer plasticity tester to be 0.349; put the billet into the extrusion molding machine Medium (the mold size is 2*2mm in diameter, 1.5mm in wall thickness) after extrusion molding, it is shaped and dried for 48 hours, and the extrusion pressure is 30MPa; it is baked after drying in a 150°C drying oven for 2h, and the heating rate is 4°C/min. Calcined at 550°C for 10 hours to obtain the final product. The prepared honeycomb structure catalyst was used for the direct decomposition reaction of N ₂ O, the space velocity was 6000h ^-1 , and the concentration of N ₂ O in the feed gas was 10% (V/V, the rest was air). Under these conditions, the lowest temperature for 100% conversion of N ₂ O is 455°C.

Example 4

118g Co-ZSM-5 molecular sieve (wherein the mass percentage of Co ion accounts for the modified molecular sieve is 1.5%), 45.92g pseudo-boehmite, 3.75g scallop powder, and 100g of nitric acid aqueous solution with a concentration of 9% are as described in Example 1. Prepare a honeycomb structured catalyst with a plasticity of 0.256; use the prepared honeycomb structured catalyst for the direct decomposition reaction of N ₂ O with a space velocity of 4000h ^-1 and a concentration of N ₂ O in the feed gas of 10% (V/V, the rest is air), under this operating condition, the minimum temperature for 100% conversion of N ₂ O is 480°C.

Example 5

135g Co-β molecular sieve (the mass percentage of Co ion in the modified molecular sieve is 2.0%), 30.61g pseudo-boehmite, 4.125g scallop powder, 3g polyethylene glycol, and 100g citric acid aqueous solution with a concentration of 12% The honeycomb structured catalyst was prepared according to Example 1, and its plasticity was 0.185; the prepared honeycomb structured catalyst was used for the direct decomposition reaction of N ₂ O, the space velocity was 6000h ^-1 , and the N ₂ O in the raw gas The concentration of N 2 O is 10% (V/V, the rest is air). Under this operating condition, the minimum temperature for 100% conversion of N _{2 O} is 468°C.

Example 6

127.12g Co-β molecular sieve (wherein the mass percent of Co ion accounts for the modified molecular sieve is 2.5%), 38.27g aluminum acid, 4.5g scallop powder, 4.5g urea, and 100g of nitric acid aqueous solution with a concentration of 15% are as described in Example 1. Prepare a honeycomb structured catalyst with a plasticity of 0.265; use the prepared honeycomb structured catalyst for the direct decomposition reaction of N ₂ O with a space velocity of 6000h ^-1 and a concentration of N ₂ O in the feed gas of 10% (V/V, the rest is air), under this operating condition, the minimum temperature for 100% conversion of N ₂ O is 475°C.

Claims (4)

1. a kind of _N2O decomposes preparation method with monolithic honeycomb molecular sieve catalyst, it is characterized in that: Fully mix the active molecular sieve component with a particle size of less than 100 mesh and the binder, the mass ratio of the active molecular sieve to the binder is 2:1-4:1, add an extrusion aid, and the extrusion aid consists of the active molecular sieve and the binder. The mass content is 2.5-3% as the basis, and the mass content reference mentioned below is the same; the mass content of the pore-forming agent is 0-3%, and it is uniformly mixed in the mixer; the active molecular sieve component is modified by Fe or Co Molecular sieve; molecular sieve is β molecular sieve, ZSM-5 molecular sieve or MCM-22 molecular sieve; Fe or Co account for 1-3% of the total mass of molecular sieve; Put the mixed powder, peptizer and water into a kneader to knead to make a billet, the mass content of the peptizer is 6-10%, and the water mass content is 50-60%; the prepared billet is sealed with a plastic film in the Aging is carried out in an environment with a temperature lower than 25°C, and the aging time is 4-10h; then it is put into an extrusion molding machine for extrusion molding, and the extrusion pressure is 10-30MPa; the prepared honeycomb body is placed in 18-25 It is shaped and dried at ℃ for 24-48 hours, and then it is put into a drying oven for drying at a drying temperature of 100-150 ℃ and a drying time of 1-2 hours; finally, it is roasted at 550 ℃ for 4-10 hours. 2. a kind of _N2O decomposition according to claim 1 is characterized in that: The binder is one or more of pseudo-boehmite, aluminum oxide and aluminate. 3. a kind of _N2O decomposition according to claim 1 is characterized in that: Described peptizer is one or more in nitric acid, tartaric acid, citric acid. 4. a kind of _N2O decomposition according to claim 1 is characterized in that: The pore forming agent is one or more of polyvinyl alcohol, cellulose, urea and polyethylene glycol.

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