CN106799225A - A kind of potassium support type soot combustion catalyst and its preparation method and application - Google Patents

Abstract

The invention relates to a potassium-loaded soot combustion catalyst and its preparation method and application. The catalyst is a potassium-loaded transition metal oxide catalyst, and the catalyst is an irregularly shaped nanoparticle morphology with a particle size distribution of 20 ~1000 nm, the content of K in the potassium-loaded soot combustion catalyst is not more than 20 wt%, and the potassium-loaded soot combustion catalyst contains transition metal Mn. The invention utilizes a very simple and cheap method to obtain a highly active soot combustion catalyst. The co-precipitation method is convenient for operation and scale-up production, the raw materials are cheap and easy to obtain, no professional equipment is needed, and it has great industrial application prospects.

Description

A kind of potassium loaded soot combustion catalyst and its preparation method and application

technical field

The invention belongs to the technical field of catalytic materials, and in particular relates to a potassium-loaded soot combustion catalyst for purifying diesel vehicle exhaust, a preparation method and application thereof.

Background technique

Diesel vehicles are widely used in real life due to their advantages of economy, high thermal efficiency and long range. However, particulate matter (PM, mainly carbon black particles) and nitrogen oxides emitted by diesel engines seriously endanger the environment and human beings. Therefore, an efficient post-treatment purification process is imperative. Usually, a particulate filter (DPF) is used to collect soot particles from diesel vehicle exhaust, and the collected soot particles can be oxidized by _O2 at a rather high temperature (>600°C). However, the exhaust temperature of a diesel engine is generally between 150 and 400°C, and the lower temperature makes it difficult for the carbon black particles in the exhaust to burn, which will lead to the deactivation of the DPF after long-term use. Therefore, it is an urgent task to develop an efficient catalyst to completely oxidize carbon black particles at a lower temperature.

Common catalysts used for soot particle oxidation, such as: CeO2 _- based compounds, perovskite oxides, noble metal-based catalysts, etc., or lack of porous structure is not conducive to the contact of active sites with carbon particles, resulting in catalyst activity Too low, or because the preparation cost of the porous structure is too high, or because of the high cost and easy poisoning of noble metals, which is not conducive to the large-scale application of the soot particle oxidation catalyst. Therefore, there is an urgent need for a simple and inexpensive preparation method to obtain non-noble metal-based highly active catalysts.

Contents of the invention

Aiming at the deficiencies of the prior art, the object of the present invention is to provide a potassium-loaded soot combustion catalyst and its preparation method and application.

In one aspect, the present invention provides a potassium-loaded soot combustion catalyst, the catalyst is a potassium-loaded transition metal oxide catalyst, and the catalyst is an irregularly shaped nano-particle morphology with a particle size distribution of 20 to 1000 nm , the content of K in the potassium-loaded soot combustion catalyst is not more than 20 wt%, and the potassium-loaded soot combustion catalyst contains transition metal Mn.

The material of the invention has good crystallization, excellent activity, good recycling performance, and has potential application prospects in the combustion degradation of solid pollutants.

Preferably, the potassium-supported soot combustion catalyst also contains transition metal Cu, and the molar ratio of transition metal Cu and Mn is not more than 0.7.

Preferably, the catalyst has a specific surface area of 5-20 m ² /g, a pore size of 20-120 nm, and a pore volume of 0.02-0.20 cm ³ /g.

On the other hand, the present invention also provides a kind of preparation method of potassium-supported soot combustion catalyst, comprising:

Mix solution A containing manganese salt and copper salt with alkaline solution B, stir for a certain period of time, then centrifuge, wash with water, and dry to obtain a dry product;

Add the dried product to the potassium salt solution, and evaporate to dryness at 50-90°C to obtain a mixed powder;

The obtained mixed powder is calcined at 400-600° C. for 1-5 hours to obtain the potassium-loaded soot combustion catalyst.

The invention combines the co-precipitation method and the impregnation method to prepare the potassium-loaded soot combustion catalyst. Specifically, the solution A containing the manganese salt and the copper salt and the alkaline solution B are first mixed to react to produce a precipitate, and then centrifuged and dried to obtain a dry product. Mix the obtained dry product with the potassium salt solution evenly, and react at low temperature (50-90°C) to obtain the product (mixed powder). During this process, the potassium salt is loaded on the powder (the so-called dry product), and it is not used in this process. Any organic matter, after calcination, it crystallizes well and is a potassium-loaded soot combustion catalyst with high catalytic activity. The method is low in cost, high in yield, does not need professional equipment, and has great industrial production value.

Preferably, the manganese salt is at least one of nitrates, acetates, sulfates, and chlorides of Mn, and the copper salt is at least one of nitrates, acetates, sulfates, and chlorides of Cu. At least one, the molar concentration of metal ions in the solution A is 0.01-0.50 mol/L, preferably 0.10-0.30 mol/L.

Preferably, the solute in the alkaline solution B is bicarbonate or/and carbonate, preferably bicarbonate, and the concentration of the alkaline solution B is 0.5-5.0 mol/L, preferably 0.5-1.0 mol/L.

Preferably, the volume ratio of the solution A to the alkaline solution B is (0.1-10):1.

Preferably, the stirring is at 0-100°C for 5 minutes to 24 hours, preferably at 25°C for 10 minutes to 1 hour.

Preferably, the heating rate of the calcination is 0.5-10°C/min, preferably 1°C/min.

Preferably, the calcination atmosphere can be flowing air or static air, preferably static air.

Preferably, the calcination temperature is preferably 500° C., and the calcination time is preferably 2 hours.

Preferably, the mixing method of the solution A and the alkaline solution B is that the alkaline solution B is quickly poured into the solution A, the solution A is dripped into the alkaline solution B, or the solution A and the alkaline solution B are co-currently precipitated, preferably Pour quickly into solution A for alkaline solution B.

Preferably, the potassium salt is at least one of nitrate, acetate, sulfate and chloride of K, and the mass content of the potassium salt is 5-20 wt%.

In another aspect, the present invention also provides the application of a potassium-loaded soot combustion catalyst in the treatment of motor vehicle exhaust.

The present invention combines the co-precipitation method and the impregnation method, reacts at low temperature to obtain the product, does not use any organic matter, crystallizes well after calcining, has extremely high catalytic activity, can completely burn soot particles at a low temperature of 340°C, and has a high Good cycle performance. The invention utilizes a very simple and cheap method to obtain a highly active soot combustion catalyst. The co-precipitation method is convenient for operation and scale-up production, the raw materials are cheap and easy to obtain, no professional equipment is needed, and it has great industrial application prospects.

Description of drawings

Fig. 1 is the scanning electron micrograph of the potassium loaded type soot combustion catalyst that the embodiment of the present invention 1 makes;

Fig. 2 is the X-ray diffraction spectrum of the obtained potassium-loaded soot combustion catalyst of the embodiment of the present invention 1;

Fig. 3 is the catalytic effect of potassium-loaded soot combustion catalyst on soot in Example 1 of the present invention;

Fig. 4 is the circulation catalytic effect of the potassium-loaded soot combustion catalyst on soot in Example 2 of the present invention.

detailed description

The present invention will be further described below through the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, not to limit the present invention.

The present invention combines the co-precipitation method and the impregnation method to prepare a potassium-loaded soot combustion catalyst, the catalyst is a potassium-loaded transition metal oxide catalyst, and the catalyst is an irregularly shaped nanoparticle morphology with a particle size distribution of 20 ~1000nm, the content of K in the potassium-loaded soot combustion catalyst is not more than 20wt%. If the potassium salt content is too low, the catalytic performance will be poor; if it is too high, it will be easily volatile and lost, resulting in high cost. The potassium-loaded soot combustion catalyst contains transition metal Mn.

The above-mentioned potassium-loaded soot combustion catalyst also contains transition metal Cu, and the molar ratio of the transition metal Cu and Mn is not more than 0.7.

The method of the invention is low in cost, high in yield, does not need professional equipment, and has great industrialized production value. The preparation method of the potassium-loaded soot combustion catalyst provided by the present invention is exemplarily described below.

A certain amount of raw material (manganese source, Cu source) is dissolved in a certain amount of solvent (such as water, alcohol-water mixed solvent, etc.) to obtain solution A containing manganese salt and copper salt (hereinafter referred to as solution A). The raw material can be one or more of Mn nitrate, acetate, sulfate or chloride. The source of Mn is preferably nitrate. One or more of Cu nitrate, acetate, sulfate or chloride. The Cu source is preferably nitrate. The concentration of metal ions (manganese ions or/and copper ions) in solution A may be 0.01-0.50 mol/L, preferably 0.10-0.30 mol/L. The molar ratio of Cu/Mn in solution A is 0-0.7.

Dissolving the precipitating agent into a certain amount of solvent (such as water, alcohol-water mixed solvent, etc.) to obtain alkaline solution B (hereinafter referred to as solution B). The precipitating agent used in solution B can be bicarbonate (such as sodium bicarbonate, ammonium bicarbonate, etc.), alkaline substances such as carbonate (such as sodium carbonate, ammonium carbonate, etc.), preferably bicarbonate. The concentration of solution B may be 0.5-5.0 mol/L, preferably 0.5-1.0 mol/L.

Under stirring conditions, solution A and solution B are mixed, and stirred at a certain temperature for a certain period of time to obtain a mixed solution containing precipitated substances. Wherein the volume ratio of the solution A and the alkaline solution B may be (0.1-10):1. The mixing method of solution A and solution B can be that solution B is quickly poured into solution A, or solution A is dripped into solution B, or solution A and solution B are precipitated in parallel, preferably solution B is quickly poured into solution A , Rapid mixing makes simultaneous homogeneous nucleation and simultaneous growth during the precipitation process, resulting in a product with uniform particle size. When the fast pouring method is adopted, the adding speed is generally more than 50mL/min, preferably more than 600ml/min, more preferably more than 1200mL/min. When the way of dropping is adopted, the adding speed can be 1-50mL/min. The stirring of solution A and solution B can be carried out at 0-100°C, preferably at 25°C, without heating or cooling, and has an energy-saving effect. The stirring time can be 5 minutes to 24 hours, preferably 10 minutes to 1 hour, the reaction is fast, the required time is short, labor and time saving).

After the obtained mixed solution containing the precipitated substance is subjected to centrifugal water washing and drying treatment, a dry product is obtained. Wherein the drying temperature may be 60-120° C., and the drying time may be 1-24 hours.

Disperse a certain amount of potassium salt and the dry product together in a solvent (such as water, a mixed solvent of alcohol and water, etc.), stir and evaporate to dryness at 50-90° C. to obtain a mixed powder. Wherein the potassium salt can be one or more of K's nitrate, acetate, sulfate or chloride. The mass content of the potassium salt is 5-20 wt%.

The resulting mixed powder is calcined under certain conditions to obtain an oxidized product, and then cooled with the furnace. A stable oxide catalyst can be obtained after calcination. The calcining condition of the mixed vermicelli can be static or flowing air, preferably static air. The calcining temperature may be 400-600°C, preferably 500°C. Calcination time may be 1-5 hours, preferably 2 hours. The heating rate during calcination may be 0.5-10°C/min, preferably 1°C/min.

In the present invention, the specific surface area of the catalyst prepared in the present invention can be 5-20 m ² /g obtained by the BET method.

In the present invention, the pore size of the catalyst prepared in the present invention can be 20-120 nm through the BJH method.

In the present invention, the pore volume of the catalyst prepared in the present invention can be obtained by the BJH method is 0.02-0.20 cm ³ /g.

Examples are given below to describe the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention, and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the above contents of the present invention all belong to the present invention scope of protection. The specific process parameters and the like in the following examples are only examples of suitable ranges, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values exemplified below.

Example 1

3.75 mmol of copper nitrate and 3.75 mmol of manganese nitrate solution were dissolved in 30 ml of water to obtain solution A, and 0.03 mol of NaHCO ₃ was dissolved into 30 ml of water to obtain solution B. Under the condition of stirring, B was quickly poured into A (adding speed 1800mL/min), and reacted at room temperature for 30 minutes. After centrifugal washing and drying, the dried product and 1 mmol KNO ₃ were ultrasonically dispersed in 50 ml of water, and evaporated to dryness in a water bath at 80°C. The powder obtained after evaporation to dryness was calcined at 500° C. for 2 h in a static air atmosphere to obtain the final product. Tested by the BET method, the catalyst prepared in this example has a specific surface area of 18 m ² /g, a pore size of 22-78 nm, and a pore volume of 0.15 cm ³ /g.

FIG. 1 is a scanning electron microscope (SEM) image of a potassium-loaded soot combustion catalyst prepared in an embodiment of the present invention. It can be seen in the figure that the obtained product is irregularly shaped nanoparticles with a particle size of about 20-1000nm. These morphological features are similar to the particle size of carbon particles, which is conducive to the full contact between carbon particles and catalyst particles, thereby promoting the improvement of catalytic performance. improve.

Fig. 2 is the X-ray diffraction pattern of the potassium-loaded soot combustion catalyst prepared in the embodiment of the present invention, in which it can be seen that the product crystallizes well. Fig. 3 is the catalytic effect of the potassium-loaded soot combustion catalyst on soot in Example 1 of the present invention. It can be seen from Fig. 3 that the loaded soot combustion catalyst can completely burn soot particles at a low temperature of 343°C.

Effect example

In order to verify the catalytic removal effect of the transition metal (composite) oxide catalyst of the present invention on soot particles in diesel vehicle exhaust, the special simulated diesel vehicle exhaust conditions were designed and carried out following experiments under laboratory conditions.

Example 2

In the fixed-bed reactor, load the mixture that the 0.1g potassium loading type soot combustion catalyst prepared by the method of embodiment 1, the soot particle of 0.01g, the mixture of 1g quartz sand particle form, pass into the following mixed gas at room temperature: NO The concentration is 500ppm, the concentration of _O2 is 10(V)%, _N2 is the balance gas, and the total flow rate is 0.2L/min. Rise from room temperature to 450°C at a rate of 5 degrees per minute. After the reaction is complete, take out the catalyst and add 0.01g of soot particles to mix thoroughly, reload the fixed bed reactor, and feed the above reaction gas. The speed is raised to 450°C per minute. Repeat the test in this way for a total of 4 times (corresponding to the marks "1 ^st ", "2 ^nd ", "3 ^rd ", "4 ^th " in Figure 4). The conversion effect of the catalyst on soot particles in the temperature range of 250-425°C was tested, and the results are shown in Figure 4. It can be seen that the sample not only has high catalytic activity, but its activity can be compared with the fresh sample at the fourth catalysis, which proves the excellent durability of the catalyst.

In summary, it can be seen that the catalyst provided by the present invention has good crystallization, excellent performance and good durability. The preparation method provided by the invention is simple and economical, the raw materials are cheap, and has high versatility. This catalyst has potential application prospects in the combustion degradation of solid pollutants.

Finally, it is necessary to explain here that: the above examples are only used to further describe the technical solutions of the present invention in detail, and cannot be interpreted as limiting the protection scope of the present invention. Non-essential improvements and adjustments all belong to the protection scope of the present invention.

Claims (10)

1. A potassium-loaded soot combustion catalyst, characterized in that, the catalyst is a potassium-loaded transition metal oxide catalyst, and the catalyst is an irregularly shaped nano-particle appearance, and the particle size distribution is 20 to 1000 nm , the content of K in the potassium-loaded soot combustion catalyst is not more than 20 wt%, and the potassium-loaded soot combustion catalyst contains transition metal Mn. 2. The potassium-loaded soot combustion catalyst according to claim 1, characterized in that, the potassium-loaded soot combustion catalyst also contains transition metal Cu, and the molar ratio of the transition metal Cu and Mn is no more than 0.7. 3. The high-porosity soot combustion catalyst according to claim 1 or 2, characterized in that the specific surface area of the catalyst is 5-20 m ² /g, the pore size is 20-120 nm, and the pore volume is 0.02 ~0.20 cm ³ /g. 4. a preparation method as described in any one of claim 1-3 potassium-loaded soot combustion catalyst, is characterized in that, comprises: Mix solution A containing manganese salt and copper salt with alkaline solution B, stir for a certain period of time, then centrifuge, wash with water, and dry to obtain a dry product; Add the dried product to the potassium salt solution, and evaporate to dryness at 50-90°C to obtain a mixed powder; The obtained mixed powder is calcined at 400-600° C. for 1-5 hours to obtain the potassium-loaded soot combustion catalyst. 5. preparation method according to claim 4 is characterized in that, described manganese salt is at least one in the nitrate, acetate, sulfate, chloride of Mn, and described copper salt is the nitrate of Cu , acetate, sulfate and chloride, the molar concentration of metal ions in the solution A is 0.01-0.50 mol/L, preferably 0.10-0.30 mol/L. 6. according to the described preparation method of claim 4 or 5, it is characterized in that, in the described alkaline solution B, solute is bicarbonate or/and carbonate, preferably bicarbonate, the basic solution B The concentration is 0.5-5.0 mol/L, preferably 0.5-1.0 mol/L. 7. The preparation method according to any one of claims 4-6, characterized in that the volume ratio of the solution A to the alkaline solution B is (0.1-10):1. 8. according to the preparation method described in any one in claim 4-7, it is characterized in that, described solution A and alkaline solution B are mixed in the way that alkaline solution B is quickly poured in solution A, and solution A is dripped into alkali In alkaline solution B, or solution A and alkaline solution B co-current precipitation, preferably alkaline solution B is quickly poured into solution A. 9. according to the preparation method described in any one in claim 4-8, it is characterized in that, described potassium salt is at least one in the nitrate, acetate, sulfate, chloride of K, and described potassium The mass content of the salt is 5-20wt%. 10. The application of a potassium-loaded soot combustion catalyst as described in any one of claims 1-3 in the treatment of motor vehicle exhaust.