CN101480615A - Catalyst for decomposing laughing gas and preparation method thereof - Google Patents

Abstract

A catalyst for catalytically decomposing laughing gas in industrial waste gas and a preparation method thereof belong to the field of industrial catalyst development. Existing catalysts are sensitive to impurities in exhaust gas, are prone to poisoning and lose activity, have short service life and are expensive. The catalyst provided by the invention is a supported catalyst, with _Al2O3 or cordierite as the carrier, one or more metal oxides of IIA, IIB, and VIII as the active _component , preferably Ni and Pt as the main catalyst active component , Co and Mg are preferably used as cocatalyst active components, and the content of the main catalyst active component and the cocatalyst active component accounts for 0.01-15.0% (wt) and 0.0-20.0% (wt) of the catalyst respectively. The catalyst is prepared by a step-by-step impregnation method, that is, the carrier is first impregnated with the active component of the co-catalyst, dried and then impregnated with the active component of the main catalyst, dried and calcined to obtain the catalyst. The catalyst of the invention has the advantages of high-efficiency decomposition, high stability, low price and the like.

Description

Catalyst for decomposing laughing gas and preparation method thereof

technical field

The invention belongs to the field of industrial catalyst development, in particular to a supported catalyst for catalytically decomposing laughing gas in industrial waste gas into nitrogen and oxygen and a preparation method thereof.

Background technique

With the development of the economy, people's material quality of life is constantly improving, the variety of chemical products is increasing, the quality of the products is constantly improving, and the degree of large-scale industrialization is gradually increasing. However, the damage caused by large-scale industrialized production to the environment is becoming more and more serious. The environment has been severely damaged, and the protection of the environment and the prevention of environmental pollution have been highly valued by countries all over the world, and they have taken active actions to protect the environment on which human beings live. Exhaust gases from industrial production processes often contain nitrogen oxides, including nitric oxide (NO), nitrogen dioxide (NO ₂ ), and laughing gas (N ₂ O). NO and NO ₂ in industrial waste gas can be recovered and utilized by water absorption to achieve the purpose of purification treatment. N ₂ O is colorless, odorless, stable in chemical properties, and not easy to be purified. In the past, there has been a lack of mature and effective emission reduction treatment technology, resulting in the industrial waste gas containing N ₂ O being discharged into the atmosphere without any treatment, while N 2 O ₂ O is one of the most harmful gases to the earth's atmosphere. It reacts with oxygen in the air to form photochemical poisons under the action of ultraviolet rays, and N ₂ O seriously destroys the ozone layer. At the same time, it has an obvious greenhouse effect. Studies have shown that its greenhouse The effect of N 2 O is about 300 times that of carbon dioxide, so controlling and eliminating the emission of N ₂ O in industrial production waste gas to large and medium-sized air has attracted great attention from all over the world. And actively conduct governance research. At present, the treatment technologies for laughing gas mainly include:

1. Pyrolysis method

Send N ₂ O and fuel gas containing low-carbon hydrocarbons together into a high-temperature reaction furnace. Under the high-temperature reaction conditions of more than 1000°C, N ₂ O and low-carbon hydrocarbons undergo a chemical reaction, in which N ₂ O is converted into nitrogen, Hydrocarbons are converted into carbon dioxide and water (US 6328941; US 4973457; US 5429811; US 6056928), and the reaction equation is as follows:

The purification of N ₂ O in industrial waste gas by this technology needs to be carried out at a temperature higher than 1000°C, and a large amount of hydrocarbon fuel is consumed in the process of treatment, resulting in waste of new resources; at the same time, the reaction temperature is high and the requirements for equipment are also very strict. Equipment investment is higher.

2. Catalytic reduction method

Under the action of a catalyst, usually at a temperature of less than 600°C, ammonia is used as a reducing agent to convert nitrogen oxides into nitrogen and water (CN1660492; CN1903412; CN101011659; CN101028594; US 5736114), and the representative reaction equation is:

This technology needs to add a reducing agent such as ammonia in the reaction process, and the operating conditions in the purification process are strict, which is prone to secondary pollution. Moreover, the catalyst has strict requirements on the impurities in the exhaust gas, is easy to be poisoned and loses activity, and the stability of the catalyst is poor.

3. Catalytic decomposition method

Usually, under the condition that the reaction temperature is lower than 700°C, laughing gas is directly catalytically decomposed into nitrogen and oxygen (CN1102435C; CN11088505C; CN120919C; WO9852681), and its representative reaction equation is:

The catalyst directly decomposes N ₂ O into nitrogen and oxygen. The catalyst has strict requirements on the impurity content in the flue gas. The catalyst is easy to sinter under high temperature conditions and loses its activity. The life of the catalyst is usually less than 2 years, and the cost of the catalyst is very high. The cost of production operation is greatly increased.

Contents of the invention

The purpose of the present invention is to solve the problems in the prior art, and provide a catalyst for purifying industrial waste gas and capable of catalytically decomposing laughing gas and a preparation method thereof.

The laughing gas in the catalytic decomposition of industrial waste gas provided by the present invention is nitrogen and oxygen. The catalyst is a supported catalyst, wherein the carrier is aluminum oxide or cordierite, and the active composition of the catalyst is the active component of the main catalyst and the active component of the co-catalyst, which is IIA , IIB, one or more of Group VIII elements. The mass content of the active component of the main catalyst in the catalyst is 0.01-15.0% (wt), and the content of the active component of the co-catalyst in the catalyst is 0.0-20.0% (wt).

The present invention also provides that the preparation method of the solid catalyst is to prepare the supported solid catalyst by adopting step-by-step impregnation method, and the specific preparation steps are as follows:

1) First measure the water absorption of the dry catalyst carrier at room temperature and normal pressure.

2) Prepare the active component of the main catalyst and the soluble salt of the active component of the co-catalyst into a certain concentration solution.

3) When Al ₂ O ₃ is used as the carrier, the carrier generally needs to be calcined at 600-800°C; when cordierite is used as the carrier, the cordierite needs to be pulverized and screened to obtain 40-60 mesh particles. The surface needs to be pretreated with Al ₂ O ₃ coating, dried and calcined as a catalyst carrier.

4) Weighing (quantity) take a quantitative amount of the carrier and the salt solution of the active component of the co-catalyst, impregnate the active component of the co-catalyst, filter after impregnating the active component of the co-catalyst for 0.5 to 12.0 hours at room temperature, and filter the filter residue in an oven at 95 to 120 ° C. After air-drying for 3-10 hours, impregnate the active component of the main catalyst with 0.1-1.0, air-dry in an oven at 95-120°C for 3-10 hours, then age in a muffle furnace at 500-600°C for 2-4 hours to prepare catalyst.

Detailed ways

The present invention will be described in detail below through examples, but the present invention is not limited to the following examples.

Example 1

Cordierite (400 holes/inch ² ) was ground and screened to obtain 40-60 mesh solid particles. After washing and pretreatment, it was air-dried at 110°C for 3 hours, and then impregnated with Al ₂ O ₃ sol to modify the carrier. The catalyst carrier was obtained by blast drying at ℃ for 10 hours and calcining at 650℃ for 2 hours.

Weigh 9.2 g of cobalt nitrate [Co(NO ₃ ) ₂ 6H ₂ O], dissolve it in 200 mL of distilled water to obtain a cobalt nitrate solution; weigh 100 g of the prepared carrier, put it in the cobalt nitrate solution and immerse it for 12.0 hours, then filter, and the filter residue The catalyst precursor I was obtained by air drying in an oven at 110° C. for 3 hours.

Weigh 21.5 g of nickel nitrate [Ni(NO ₃ ) ₂ 6H ₂ O] and dissolve it in 200 mL of distilled water to obtain a nickel nitrate solution; place the above catalyst precursor I in the nickel nitrate solution for 0.5 hours and filter, and filter the residue at 110°C Blast drying in an oven for 5 hours, and roasting in a muffle furnace at 550° C. for 4 hours to obtain Catalyst I for Decomposing Laughing Gas.

Weigh 1g of the prepared catalyst I and place it in a fixed bed reactor. Under the experimental conditions of 450°C, gas composition 0.25% (v) N ₂ O + nitrogen, and gas volume space velocity 2000mL/g.hr, N ₂ O is decomposed and converted The rate is 94.5%.

Example 2

Cordierite (400 holes/ ⁱⁿ² ) was ground and screened to obtain 40-60 mesh solid particles. After washing and pretreatment, it was air-dried at 110°C for 3 hours, and then impregnated with Al ₂ O ₃ sol to modify the carrier. Blast drying at ℃ for 4.5 hours, and calcining at 600 ℃ for 2 hours to obtain a catalyst carrier.

Weigh cobalt nitrate [Co(NO ₃ ) ₂ 6H ₂ O] and [Ca(NO ₃ ) ₂ 6H ₂ O] 10.0g and 3.5g, dissolve in 200mL distilled water to obtain cobalt nitrate + calcium nitrate solution; weigh 100 g of the prepared carrier was taken, immersed in a cobalt nitrate solution for 10 hours, and then filtered, and the filter residue was air-dried in an oven at 95° C. for 12 hours to obtain the catalyst precursor II.

Weigh 2.5g and 20.0g of chloroplatinic acid [H ₂ PtCl ₆ 6H ₂ O] and nickel nitrate [Ni(NO ₃ ) ₂ 6H ₂ O], respectively, and dissolve them in 200mL distilled water to obtain acid solution, the catalyst precursor II was placed in nickel nitrate + chloroplatinic acid solution for 0.1 hour and then filtered, and the filter residue was air-dried in an oven at 100°C for 8 hours, and then roasted in a muffle furnace at 550°C for 3 hours to obtain decomposed Gas Catalyst II.

Weigh 1g of prepared catalyst II in a fixed bed reactor, under the experimental conditions of 450°C, gas composition 0.25% (v) N ₂ O + nitrogen, gas volume space velocity 3000mL/g.hr, the decomposition conversion rate of N ₂ O 99.8%.

Example 3

Weigh cobalt nitrate [Co(NO ₃ ) ₂ 6H ₂ O], magnesium nitrate [Mg(NO ₃ ) ₂ 6H ₂ O] and zinc nitrate 8.6g, 10.4g and 6.4g respectively, dissolve them in 200mL distilled water, Obtain a solution containing cobalt nitrate and magnesium nitrate; weigh 100g of the Al ₂ O ₃ carrier that has been calcined at 600°C and place it in the cobalt nitrate+magnesium nitrate solution, filter after immersion for 10 hours, and dry the filter residue in an oven at 95°C for 12 hours , to obtain the catalyst precursor III; weigh 12.8g of nickel nitrate [Ni(NO ₃ ) ₂ 6H ₂ O], dissolve it in 200mL of distilled water to obtain a nickel nitrate solution, and place the catalyst precursor III in the nickel nitrate solution for 2.0 hours, filtered, and the filter residue was dried at 100° C. for 10 hours, and calcined in a muffle furnace at 550° C. for 3 hours to obtain catalyst III for decomposing laughing gas.

Weigh 1g of prepared catalyst III in a fixed bed reaction device, at 300°C, gas volume composition 1.35% (v) N ₂ O + 1.8% (v) O ₂ + 1.01% (v) CO + 3.5% (v) Under the experimental conditions of CO ₂ +0.02%(v)NO+0.01%(v)NO ₂ +2.5%(v)H ₂ O+0.03%(v)SO ₂ +nitrogen, gas volume space velocity 2000mL/g.hr , N ₂ O decomposition conversion rate was 69.8%.

Example 4

Weigh cobalt nitrate [Co(NO ₃ ) ₂ 6H ₂ O] and magnesium nitrate [Mg(NO ₃ ) ₂ 6H ₂ O] 10.3g and 10.4g respectively, and dissolve them in 200mL distilled water to obtain cobalt nitrate and Magnesium nitrate solution; Weigh 100g of Al ₂ O ₃ carrier that has been calcined at 650°C, place it in cobalt nitrate + magnesium nitrate solution, filter after immersion for 0.5 hours, and dry the filter residue in an oven at 95°C for 12 hours to obtain catalyst precursor IV .

Weigh 2.2g of chloroplatinic acid [H ₂ PtCl ₆ 6H ₂ O] and dissolve it in 200mL of distilled water to obtain a chloroplatinic acid solution; place the catalyst precursor VI in the chloroplatinic acid solution, filter after immersion for 0.1 hour, and filter residue in Blast drying in an oven at 105°C for 10 hours, and then calcining in a muffle furnace at 550°C for 3 hours to obtain catalyst IV for decomposing laughing gas.

Weigh 1g of catalyst IV, at 300°C, the gas volume composition is 1.35%(v) _N2O +1.8%(v) _O2 +1.01%(v)CO+3.5%(v) _CO2 +0.02%(v) Under the experimental conditions of NO+0.01%(v)NO ₂ +2.5%(v)H ₂ O+0.03%(v)SO ₂ +nitrogen, gas volume space velocity 2000mL/g.hr, the decomposition conversion rate of N ₂ O is 73.7%.

Example 5

Weigh cobalt nitrate [Co(NO ₃ ) ₂ 6H ₂ O] and magnesium nitrate [Mg(NO ₃ ) ₂ 6H ₂ O] 7.1g and 5.7g respectively, and dissolve them in 200mL distilled water to obtain cobalt nitrate and Magnesium nitrate solution; Weigh 100g of the Al ₂ O ₃ carrier that has been calcined at 650°C and place it in cobalt nitrate+magnesium nitrate solution, filter after immersion for 2.0 hours, and dry the filter residue in an oven at 105°C for 5 hours to obtain a catalyst precursor V;

Weigh 1.1g and 15.0g of chloroplatinic acid [H ₂ PtCl ₆ 6H ₂ O] and nickel nitrate [Ni(NO ₃ ) ₂ 6H ₂ O] respectively and dissolve them in 200mL distilled water to obtain chloroplatinic acid + nickel nitrate solution The catalyst precursor V was placed in chloroplatinic acid+nickel nitrate solution, filtered after immersion for 2.0 hours, and the filter residue was air-dried in an oven at 105°C for 5 hours, and then roasted in a muffle furnace at 600°C for 3 hours to obtain a catalyst for decomposing laughing gas V.

Weigh 1g of catalyst V, at 400°C, the gas volume composition is 1.35%(v)N ₂ O+1.8%(v)O ₂ +1.01%(v)CO+3.5%(v)CO ₂ +0.02%(v) Under the experimental conditions of NO+0.01%(v)NO ₂ +2.5%(v)H ₂ O+0.03%(v)SO ₂ +nitrogen, gas volume space velocity 2000mL/g.hr, the decomposition conversion rate of N ₂ O is 98.9%.

Claims (7)

1, a kind of direct catalyst for decomposing laughing gas is with Al ₂O ₃Or cordierite is the loaded catalyst of carrier, it is characterized in that: as the activity of such catalysts component, it is characterized in that: constitute the activity of such catalysts component and be divided into major catalyst active constituent and co-catalyst active constituent with one or more metal oxides of IIA, IIB, VIII; Major catalyst active constituent content accounts for 0.01～15.0% (wt) of catalyst, and co-catalyst active constituent content accounts for 0.0～20.0% (wt) of catalyst.

2, according to the described catalyst for decomposing laughing gas of claim 1, it is characterized in that: the metal oxide of preferred Ni and Pt is as the major catalyst active constituent, and active constituent content accounts for 0.01～10.0wt% of catalyst total amount.

3, according to the described catalyst for decomposing laughing gas of claim 1, it is characterized in that: the metal oxide of preferred Co and Mg is as the co-catalyst active constituent, and active constituent content accounts for 0.0～10.0wt% of catalyst total amount.

4, the described catalyst for decomposing laughing gas preparation method of a kind of claim 1～3, the method for employing step impregnation.Wherein used active component Pt adopts the platinum chlorate as the catalyst activity component precursor, and all the other adopt nitrate as the catalyst activity component precursor.

5, by the described catalyst for decomposing laughing gas of claim 1～4, it is characterized in that: when with Al ₂O ₃During for carrier, carrier needs 600～800 ℃ of preliminary treatment.

6, by the described catalyst for decomposing laughing gas of claim 1～5, it is characterized in that: when being carrier with the cordierite, cordierite pulverizing and screening are obtained 40～60 order particles, the cordierite particle surface needs through Al ₂O ₃Coating preliminary treatment, and 95～120 ℃ of dryings 3～10 hours, back behind 500～800 ℃ of roasting 2～4h as catalyst carrier.

7, by claim 1,4～6 described catalyst for decomposing laughing gas, it is characterized in that: carrier at first flooded the co-catalyst active constituent after 0.5～12.0 hour, filter, filter residue flooded the major catalyst active constituent 0.1～2.0 hour again 95～120 ℃ of forced air dryings after 3～10 hours, roasting 2～4h under 95～120 ℃ of forced air dryings 3～10 hours, 500～800 ℃ of conditions.