CN1559681A

CN1559681A - High performance carbon monoxide oxidation catalyst and its preparation method

Info

Publication number: CN1559681A
Application number: CNA2004100229036A
Authority: CN
Inventors: 王正祥; 陈洪
Original assignee: SCIENCE AND TECHNOLOGY DEVELOPMENT DEPARTMENT ZHUZHOU TECHNOLOGY COLLEGE
Current assignee: SCIENCE AND TECHNOLOGY DEVELOPMENT DEPARTMENT ZHUZHOU TECHNOLOGY COLLEGE
Priority date: 2004-02-17
Filing date: 2004-02-17
Publication date: 2005-01-05
Anticipated expiration: 2024-02-17
Also published as: CN100381202C

Abstract

A catalyst for oxidizing CO with high performance is prepared from KMnO4, MnSO4, CuSO4.5H2O, H2SO4 and Na2CO3 through reducing KMnO4 by MnSO4 in acidic condition to obtain active MnO2 powder, and reacting on others to regulate the size of crystal grain and its hydrated degree.

Description

High-performance carbon monoxide oxidation catalyst and preparation method thereof

Technical Field

The invention relates to an improvement (international classification number C10K3/00) of chemical composition for catalytic treatment of combustible gas containing carbon monoxide, in particular to a carbon monoxide oxidation catalyst and a preparation method thereof.

Technical Field

The carbon monoxide generated by incomplete combustion of carbon and carbon compounds is harmful to human bodyAre well known. Carbon monoxide gas with concentration capable of causing death can be generated in the case of fire disaster, gas outburst and gas explosion in coal mines; in addition, the pollution of the smoke to the indoor air, the tail gas discharged by automobiles and the like can generate carbon monoxide which is harmful to human bodies. Therefore, the development of a carbon monoxide normal temperature oxidation catalyst with excellent performance has been a subject of interest and ongoing execution by researchers. Generally, carbon monoxide is relatively easily oxidized. Therefore, the catalyst has various preparation methods and compositions, such as common metals or their oxides or their mixtures, but these catalysts generally can only function at high or higher temperature ranges, and catalysts having excellent catalytic activity at low or normal temperatures are rare. At present, the key part of the filter type self-rescuer and the gas mask for fire fighting for coal mines is MnO₂And a CuO-based catalyst for normal temperature oxidation of carbon monoxide (called Hogata Hopcalite). The catalyst is a non-carrier catalyst and is characterized by relatively low cost and capability of generating catalytic oxidation in a room temperature environment. But currently with MnO₂And CuO as the main carbon monoxide oxidation catalyst also have disadvantages. Mainly, the activity of the catalyst can not meet the performance requirement of the product at present, and the activity reproducibility of the catalyst is poor; secondly, the concentration of the acid used in the preparation is higher, generally more than 60%, so that the environmental pollution is larger in the preparation, and the environmental protection is not facilitated; furthermore, MnO is currently used₂And CuO as main component, the primary particles of manganese dioxide are coarse and not distributedThe uniformity leads to poor hydration degree and poor hydration uniformity, and has great influence on the catalytic activity of the catalyst while being inconvenient to wash. There is a need to improve this.

Disclosure of Invention

The invention aims to provide a catalyst for oxidizing carbon monoxide, which has low acid concentration (below 60%) during preparation, low pollution during preparation and low pollutionThe primary particles of manganese dioxide generated in the preparation process of manganese dioxide are finer in particles, and the novel carbon monoxide oxidation catalyst is easy to wash. The purpose of the invention is realized by the following technical scheme that KMnO is adopted₄As an oxidant, MnSO₄Uses a liquid phase precipitation method to prepare superfine powder as a reducing agent to prepare superfine MnO₂The powder and CuO are used for preparing a product with excellent performance to carbon monoxide by utilizing the synergistic catalysis effect. Compared with the product prepared by the conventional preparation method, the powder is fine and easy to wash, and the excellent performance of the primary particles is maintained.

The components and the mixture ratio are as follows: KMnO is selected₄、MnSO₄、CuSO₄.5H₂O、H₂SO₄、Na₂CO₃Is taken as a raw material; the components are as follows (by weight portion):

KMnO₄1 part of MnSO₄.H₂1.4-1.7 parts of O;

CuSO₄.5H₂0.5-2.9 parts of O and H₂SO₄2.0-6.8 parts;

Na₂CO₃0.26 to 1.47 parts.

Wherein the molar ratio of manganese sulfate to potassium permanganate is 1.26-1.50, the content of copper oxide is 15-45%, and the content of sulfuric acid is 45-60% by weight.

The specific manufacturing method comprises the following steps: under acidic conditions, with MnSO₄Reduction of KMnO₄Preparing active manganese dioxide, wherein the reaction molecular formula is as follows:

the invention uses surfactant to adjust the size and hydration degree of manganese dioxide crystal grain under lower acidity (45% -60%), to prepare carbon monoxide catalyst product with excellent performance, which can be used in industrial production.

The specific manufacturing process comprises the following steps:

1. preparation of active manganese dioxide

Dissolving a certain amount of selected manganese sulfate in water, adding a certain amount of sulfuric acid, adding a certain amount of powdered potassium permanganate at a constant speed at the temperature of 50-65 ℃, continuing to react for 2-3 hours after the addition is finished, centrifuging and drying the obtained precipitate, and washing the precipitate with water until sulfate ions do not exist.

2. Preparation of mixed precipitate of manganese dioxide and basic copper carbonate

Dispersing manganese dioxide in water, adding a certain amount of copper sulfate solution, stirring for 30-60 minutes, neutralizing with concentrated soda ash solution until the pH value is about 7-8, washing the obtained composite precipitate until sulfate ions do not exist, centrifugally drying, and drying at 120 ℃.

3. Catalyst formation and activation

And pressing the obtained mixed powder of manganese dioxide and basic copper carbonate into a wafer with the thickness of 1cm and the diameter of 80cm under an industrial oil press of 100 tons, crushing and collecting the wafer into particles with the particle size of 12-18 meshes, activating the particles at the temperature of 250 ℃ for 6 hours, and sealing and storing the particles.

The working mechanism of the invention is as follows:

under acidic conditions, KMnO₄With MnSO₄The oxidation-reduction reaction takes place to produce active manganese dioxide with catalytic oxidation performance to carbon monoxide, and the reaction is as follows:

the reaction process is accompanied by the following side reactions

Theoretically, it is thought that the oxidation activity of manganese oxide mainly depends on the valence state of manganese, the crystal structure of manganese dioxide, the particle size and particle size distribution of manganese dioxide, and has a close relationship with the hydration degree and hydration uniformity of manganese dioxide, and in general,when a good crystal structure, a small particle size and a good particle size distribution are obtained, a high hydration degree and hydration uniformity can be obtained.

The catalytic reaction of the carbon monoxide oxidation catalyst mainly comprising manganese dioxide and copper oxide belongs to heterogeneous catalytic reaction. It is generally believed that the heterogeneous catalytic reaction involves several processes: the method comprises seven processes of reactant molecules, namely, the outer diffusion of the laminar boundary layer, the inner diffusion of the reactant molecules in catalyst pores, the chemical adsorption on the surface of the catalyst, surface chemical reaction, the desorption of reaction products, the inner diffusion of desorbed products in the catalyst pores, the outer diffusion of the desorbed products in the laminar boundary layer and the like. The catalytic oxidation of carbon monoxide by the catalyst can be divided into four stages: the first stage, the initial stage of the reaction, in which the concentration of the catalyst active centers is high, carbon monoxide entering the catalyst layer can be completely captured by the catalyst active centers, and there is a relevant process when going through the catalytic reaction. And in the second stage, the carbon monoxide is in an accelerated oxidation stage, wherein on one hand, the temperature of the catalyst layer is continuously increased to be beneficial to improving the oxidation speed of the carbon monoxide, on the other hand, the active points of the catalyst continuously adsorb the carbon monoxide and carry out surface chemical reaction to cause the inactivation of the catalyst, the active points are reduced, and at the moment, the permeation concentration of the carbon monoxide is in a slow rising trend. In the third stage, the temperature of the catalyst layer does not rise any more, and the deactivation speed of the catalyst is reduced, which shows that the relative balance between the adsorption and the evaporation of water, which are main factors causing the deactivation of the catalyst, is achieved, and the apparent oxidation rate of the carbon monoxide is basically maintained unchanged. In the fourth stage, the catalyst is in the accelerated deactivation stage, and the concentration of carbon monoxide permeating the catalyst layer is increased continuously. The catalytic performance of the catalyst is equal to MnO in four stages of the whole catalytic reaction₂The particle size and the distribution uniformity of the particle size have a great relationship with the hydration degree and the hydration uniformity of the manganese dioxide in the preparation process, the finer and more uniform the manganese dioxide particles are, the higher the catalytic activity of the manganese dioxide particles is, the higher the hydration degree is, the better the hydration uniformity is, the higher the catalytic performance of the manganese dioxide particles is, the particle size and the particle size distribution simultaneously influence the hydration performance of the manganese dioxide particles, the smaller the particle size is, the higher the hydration degree is, the more uniform the particle size distribution is, and the more uniform the hydration. In aqueous suspension of manganese dioxide, the manganese dioxide particles are surrounded by water, and these water molecules are relatively strongly bonded around the surfaces of the manganese dioxide particles, and reactIn the process of (1), MnO₂The surface of the particles also being adsorbed with a considerable amount of other ions, e.g.SO₄ ^2-Etc. the introduction of these impurities leads to MnO on the one hand₂The difficulty of washing, on the other hand, affects the hydration degree and hydration uniformity of the manganese dioxide, thereby finally affecting the catalytic oxidation performance of the catalyst.

Detailed Description

Example one

KMnO is selected₄，MnSO₄，CuSO₄.5H₂O，H₂SO₄，NaOH，Na₂CO₃The raw materials are mixed according to the following proportion (by weight portion):

KMnO₄1 part of MnSO₄.H₂1.4-1.7 parts of O;

CuSO₄.5H₂0.5-2.9 parts of O; h₂SO₄2.0-6.8 parts;

Na₂CO₃0.26 to 1.47 parts.

Dissolving 1.33 parts by weight of manganese sulfate in 1.4 parts by weight of water, then adding 3 parts by weight of sulfuric acid, adding 1 part by weight of powdery potassium permanganate at a constant speed at the temperature of 50-65 ℃, continuing to react for 2-3 hours after the addition is finished, centrifuging and drying the obtained precipitate, and washing the precipitate with water until sulfate ion is avoided. Preparation of mixed precipitate of manganese dioxide and basic copper carbonate

Dispersing 1 part by weight of manganese dioxide in water, adding a solution containing 2.1 parts by weight of copper sulfate pentahydrate, stirring for 30-60 minutes, neutralizing with a concentrated aqueous solution containing 1.1 parts by weight of soda ash until the pH value is about 7-8, washing the obtained composite precipitate until sulfate ions are not generated, centrifugally drying, and drying at 120 ℃.

And pressing the dried mixed powder of manganese dioxide and basic copper carbonate into a wafer with the thickness of 1cm and the diameter of 80cm under a 100-ton industrial oil press, crushing, collecting particles with the size of 12-18 meshes, activating at the temperature of 250 ℃ for 6 hours, and sealing and storing the sample.

We determined the optimal reaction conditions. The molar ratio of manganese sulfate to potassium permanganate is as follows: 1.43; sulfuric acid content50-58% of the weight of the liquid, 55-65 ℃ of the reaction temperature, 40% of the content of copper oxide and 1000-1700 kg/cm of the forming pressure²The activation temperature is 250-280 ℃, and the activation time is 4-6 hours.

1) The raw material ratio is as follows: the molar ratio of the reactant manganese sulfate to potassium permanganate is 1.26-1.50, and 1.43 is the best.

2) The content of active ingredients is as follows: in two compositions MnO₂In the CuO catalyst system, the content of copper oxide is 15-45%

The influence on the performance of the catalyst is small, and the optimal content of copper oxide is 40 percent

4) The preparation reaction temperature of the manganese dioxide can be changed within 50-65 ℃, and the performance of the product is not greatly influenced.

5) The molding pressure is 1000kg/cm²～1700kg/cm²The catalyst product has certain strength, the catalytic performance of the catalyst is ensured, the amount of dust in the wearing process is controlled, the respiratory resistance is reduced, and the dust inhalation amount of self-rescuer and fire-fighting gas mask wearing persons is reduced.

6) Activation temperature: the activation temperature can be varied from 200 to 300 deg.C, preferably 250 deg.C

7) Activation time: 4-6 hours.

8)Particle size: the catalyst forming particles are 10-18 meshes, and the optimal distribution of the catalyst forming particles is preferably 12-14 meshes, so that the catalyst forming particles are favorable for the catalytic performance and the reduction of the respiratory resistance.

9) The further improvement of the catalyst can not only greatly reduce the dust amount, but also greatly reduce the cost.

Claims

1. HeightA performance carbon monoxide oxidation catalyst is characterized in that: the catalyst is KMnO₄As an oxidant, MnSO₄Uses a liquid phase precipitation method to prepare superfine powder as a reducing agent to prepare superfine MnO₂The powder is prepared by utilizing the synergistic catalysis effect with CuO, and comprises the following components in percentage by weight: KMnO is selected₄、MnSO₄、CuSO₄.5H₂O、H₂SO₄、Na₂CO₃Is taken as a raw material; the components are as follows (by weight portion):

KMnO₄1 part of MnSO₄.H₂1.4-1.7 parts of O;

CuSO₄.5H₂0.5-2.9 parts of O; h₂SO₄2.0-6.8 parts;

Na₂CO₃0.26-1.47 parts;

2. The process of claim 1 for the preparation of a high performance carbon monoxide oxidation catalyst, wherein: the preparation method of the catalyst comprises the following steps: under acidic conditions, withMnSO₄Reduction of KMnO₄Preparing active manganese dioxide, under the condition of lower acidity (45% -60%), and regulating the size and hydration degree of manganese dioxide crystal grains by using surfactant, and its concrete preparation process is as follows:

A. preparation of active manganese dioxide

Dissolving a selected amount of manganese sulfate in water, adding a certain amount of sulfuric acid, adding a certain amount of powdery potassium permanganate at a constant speed at the temperature of 50-65 ℃, continuing to react for 2-3 hours after the addition is finished, centrifuging and drying the obtained precipitate, and washing the precipitate with water until sulfate ions do not exist;

B. preparation of mixed precipitate of manganese dioxide and basic copper carbonate

Dispersing manganese dioxide in water, adding a certain amount of copper sulfate solution, stirring for 30-60 minutes, neutralizing with concentrated soda ash solution until the pH value is about 7-8, washing the obtained composite precipitate until sulfate ions do not exist, centrifugally drying, and drying at 120 ℃;

C. catalyst formation and activation