CN112516989B - Coating material catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a coating material catalyst and its preparation method and application, and relates to the field of DPF catalysts. The invention discloses the use of lanthanum and praseodymium modified alumina as a carrier, and supporting alkali metals, transition metals and noble metals as main catalysts and catalytic promoters. The agent is loaded with alkali metals on alumina by injection and dripping, quickly dried by flash evaporation, and then roasted at high temperature in a rotary calciner. Finally, transition metals and precious metals are loaded as the main catalyst, thereby obtaining a This high-efficiency oxidation coating material is coated on the particle trap DPF made of cordierite or silicon carbide material to greatly improve the conversion efficiency of DPF oxidized carbon fumes. The invention can solve the existing problems of low regeneration efficiency, short regeneration mileage, high regeneration temperature and high production cost of coating material catalysts in the prior art.

Description

Coating material catalyst and preparation method and application thereof

Technical field

The invention relates to the field of DPF catalysts, and in particular to a coating material catalyst and its preparation method and application.

Background technique

The DPF catalyst is suitable for the treatment of PM pollutants in vehicle exhaust gases of National VI diesel engine models and non-road Stage IV vehicles. In diesel vehicle exhaust gas treatment devices, particle traps are used as devices for collecting and filtering soot. The invented high-efficiency oxidation coating Coated on the inlet end wall of the DPF, the DPF is heated by the temperature of the engine exhaust gas, so that the highly efficient oxidation coating can oxidize the captured soot in each temperature range, thus consuming the black smoke inside the DPF. , so that DPF can be recycled for a long time.

Diesel engine exhaust contains a large number of pollutants, and the key is how to reduce PM. PM is soot. Soot is the product of incomplete combustion of diesel engine fuel. It contains a large number of black carbon particles. It is not pure carbon, but a polymer. Its main components change slightly with the load of the diesel engine. Generally, Contains C 85-95%, O 4-8% and a small amount of H and ash. Some people also believe that soot is graphite crystals, consisting of particles with a diameter of about 0.05 μm that aggregate into porous carbon particles of 0.1-10 μm.

The coating materials currently on the market have the following two points regarding the oxidation efficiency of soot: First, the coating conversion efficiency is not high, resulting in the regeneration mileage of the DPF being too short. Generally, road vehicles trigger active regeneration at about 500 kilometers. And it requires a higher temperature (above 600℃); secondly, the price is high, and the precious metal loading amount needs to be above 5-10g/cft.

People are eager to have a catalyst with high passive regeneration efficiency, long regeneration mileage and low price. At the same time, its production method and process conditions are relatively simple to prepare DPF catalyst.

Contents of the invention

The technical problem to be solved by the present invention is to provide a coating material catalyst and its preparation method and application, so as to solve the problems of low regeneration efficiency, short regeneration mileage, high regeneration temperature and high production cost of the coating material catalyst in the prior art. The problem.

The technical solution adopted by the present invention to solve the technical problem is: a preparation method of coating material catalyst, which includes the following steps:

S1: Add the lanthanum-praseodymium modified alumina material to deionized water, control the final solid content to 20-30%, and control the pH of the solution to 3.8-4.2 during the addition process; then add the alkali solution into the alumina dropwise through peristaltic pump injection Slurry, control the dropping time to 60-90 minutes, use nitric acid to adjust the pH value of the slurry to maintain between 3.8-4.2, and control the stirring time to 3.0-5.0h to form mixed solution A, the lanthanum The mass proportion of lanthanum oxide and praseodymium oxide in the praseodymium modified alumina material is 1.0%-4.0%, and its surface area meets the test value of not less than ^150m2 /g after thermal aging for 4 hours under the aging condition of 1000°C. The alkali solution It is a carbonate solution of any one or more of Na, Cs, Ba, K, Li, and Mg. The mass ratio of the carbonate in the carbonate solution to the alumina in the alumina slurry is 1 :8-1:9;

S2: Dry the mixed solution A through a spray flash dryer at 100°C-150°C. During the drying process, control the feed rate to achieve a drying efficiency of 95%-98% to obtain powder B;

S3: Powder B is calcined at high temperature in a rotary calcining furnace at a programmed temperature rise rate of 5°C/min. The final temperature is controlled at 900°C-1000°C and kept for 4.0h-6.0h. During the calcination process, air is added for atmosphere protection;

S4: Prepare the calcined powder into slurry C through wet grinding, and control the detected particle size D50 in the slurry C to 2.5-3.0 μm;

S5: Mix transition metal nitrates and precious metal nitrates in deionized water and inject them into slurry C through a peristaltic pump. Control the dripping time to 60-90 minutes. During the process, use ammonia to adjust the pH value of the slurry to maintain it at Between 3.8-4.2, control the stirring time to 1.0-2.0h to obtain slurry D. The transition metal nitrate is any one or more of Cu, Co, Mn, Fe, V, Sn, Ni, and W. The transition metal nitrate is The ratio of the amount of metal nitrate to the amount of alumina in the alumina slurry is 0.03-0.06, and the ratio of the amount of the precious metal nitrate to the amount of alumina in the alumina slurry is 0.005-0.01;

S6: Control the solid content of slurry D to 10%-14%, add boehmite powder, then add hydroxymethylcellulose, and stir for 30-60 minutes to obtain slurry E. The boehmite The mass ratio of the powder to the alumina in the slurry D is 1:100-2:100, and the mass ratio of the hydroxymethylcellulose to the alumina in the slurry D is 4:100-6:100;

S7: Choose the semi-transparent carrier with asymmetric structure of silicon carbide of NGK 300-10 or the semi-transparent carrier with asymmetric structure of cordierite of NGK 300-9, choose half of the air inlet end for coating, and control the loading amount at 15-20g /L, and then dried and roasted to obtain the catalyst semi-finished product F;

S8: The catalyst semi-finished product F is subjected to hydrothermal aging treatment at 800°C for 20 hours. The mass ratio of water to catalyst semi-finished product F in the hydrothermal aging treatment is 1:10 to obtain the catalyst semi-finished product G;

S9: Perform sulfur poisoning treatment on the semi-finished catalyst product G. The treatment conditions are SO ₂ 200 ppm, O ₂ 10%, H ₂ O 10%, temperature 250°C, and time 16 hours to obtain the finished catalyst product H.

Further, the precursor of the lanthanum and praseodymium modified alumina selected in step S1 is a lanthanum and praseodymium aluminum common structure, and the molding and roasting temperature of the precursor of the lanthanum and praseodymium modified alumina is not less than 950°C, and the time is not less than 5.0 h, and control the impurity content not to exceed 1.0%.

Further, the alkali solution in step S1 is a carbonate solution of at least two of Na, Cs, Ba, K, Li, and Mg.

Further, the mass ratio of the carbonate in the carbonate solution and the alumina in the alumina slurry in step S1 is 1:8.5-1:9.

Further, in step S1, first add deionized water to the reaction kettle, control the heating temperature to 40-60°C, and then add the lanthanum-modified alumina powder to the deionized water. During the process, the pH is maintained at 3.9- 4.1, the temperature is maintained at 40-60℃.

Further, in step S2, the spray flash dryer uses laboratory spray drying equipment with a power of 4.0kw, an inlet air temperature of 120-150°C, and a water evaporation capacity of 1.0-1.5kg/h.

Furthermore, in the step S3, during high-temperature calcination, the temperature is first raised to 200°C and maintained for 1.0 h, the bound water is evaporated, and then the temperature is raised to 600°C and maintained for 2.0 h to perform the pre-baking process. Then raise the temperature to 950-1000℃ and maintain it for 4.0-5.0h.

Further, during wet grinding in step S4, a horizontal sand mill is used for grinding, using zirconium oxide beads with a particle size of 1.0-1.2mm, the grinding cavity volume is 0.5L, and the zirconium bead filling amount is the total volume. 70-75%, power is 2.2kw.

Further, in the step S4, a laser particle size analyzer is used for particle size detection and analysis. During the test process, a refractive index of 1.544 is selected, the particle addition amount is a shading rate of 13-15%, ultrasonic waves are used for dispersion, and the dispersion time is three minutes. .

Further, in step S5, iron nitrate is first added to the deionized water, then nickel nitrate is added to the deionized water, and then platinum nitrate is added to the deionized water.

Further, in step S5, the stirring time is 60-70 minutes.

Further, in step S6, the solid content of slurry D is controlled to be 10%, the mass ratio of boehmite to molecular sieve is 1:100, and the mass ratio of cellulose to molecular sieve is 6:100.

Further, in the step S7, coating is carried out using the bottom feeding method and feeding from the unilateral air inlet end, the drying temperature is 100-120°C, and the baking temperature is 600-650°C.

The present invention also provides a coating material catalyst, which is prepared by any of the above preparation methods of the coating material catalyst.

The invention also provides an application of a coating material catalyst. The above-mentioned coating material catalyst for rapid oxidation of soot on the DPF is applied to the purification of soot in the exhaust gas of National VI diesel engine models and non-road four-stage vehicle models.

The invention has the following beneficial effects:

The coating material catalyst prepared by the preparation method of the present invention has higher regeneration efficiency, longer regeneration mileage, lower regeneration temperature and lower production cost. The main advantage of this coating material catalyst is that it has both good passive regeneration ability for soot and good sulfur resistance stability. The coating material catalyst has strong hydrothermal aging performance and a large specific surface area of spinel structure. At the same time, it improves the oxidation efficiency of the DPF catalyst for soot according to the NO and NO ₂ provided by the engine, so that the DPF regeneration mileage can be extended to 1500-2500 kilometers to achieve long-term stable use of DPF. The high-efficiency oxidation-coated DPF catalyst prepared by the method of the present invention has a simple preparation process because no waste is generated in the process; and it contains more alkali metals and transition metals, so the catalyst is less sensitive to sulfur and has better resistance to sulfur. Sulfur poisoning ability. The high-efficiency oxidation coating DPF catalyst prepared by the present invention has a BET specific surface area of 50-80 m ² /g, good hydrothermal resistance and stability, and the PM oxidation efficiency can reach an efficiency of greater than 50% at 400°C.

Description of the drawings

Figure 1 shows the particle size composition of black smoke particles of a National VI diesel engine;

Figure 2 is a diagram of the capture efficiency of NGK’s 300-10 silicon carbide asymmetric carrier or NGK’s 300-9 cordierite asymmetric carrier without coating;

Figure 3 is a diagram of the soot conversion efficiency of Example 1, Comparative Example 1 and Comparative Example 2;

Figure 4 is a bench test chart of the soot conversion efficiency of Example 2, Comparative Example 3 and Comparative Example 4;

Figure 5 shows the performance advantages of materials containing K ₂ CO ₃ ;

Figure 6 shows the bench test data of the SINOTRUK MC13 National VI engine;

Figure 7 is a spectrum of K element scanning on a certain plane of the high-efficiency oxidation coating powder using an electron scanning microscope for the catalyst of the present invention;

Figure 8 is a spectrum of Fe element scanning on a certain plane of the high-efficiency oxidation coating powder using an electron scanning microscope on the catalyst of the present invention;

Figure 9 is a diagram showing the proportions of elements obtained using a scanning electron microscope for the catalyst of the present invention.

Detailed ways

The particle size composition of black smoke particles of a National VI diesel engine is shown in Figure 1. The number concentration of PM is mainly concentrated in 5-50nm, and the mass concentration is mainly concentrated in 50-500nm.

In order to meet the national regulations and standards for road National VI diesel engine models and non-road Stage IV vehicles, it is necessary to select appropriate particle traps and coating catalyst materials that can enable the DPF to be recycled for a long time.

According to the particle size of the particles emitted by the engine, we choose NGK's 300-10 silicon carbide asymmetric carrier or NGK's 300-9 cordierite asymmetric carrier as the selected carrier to capture soot. The capture effect is shown in Figure 2 shown.

As can be seen from Figure 2, the PM capture efficiency of NGK's 300-10 silicon carbide asymmetric carrier or NGK's 300-9 cordierite asymmetric carrier without coating reaches more than 90%.

In order to further improve the collection efficiency, the coating material with rapid oxidation of soot is coated on NGK's 300-10 silicon carbide asymmetric carrier or NGK's 300-9 cordierite asymmetric carrier.

Example 1:

Follow the steps below to prepare the coating material catalyst:

(1) Select 5.0% lanthanum-praseodymium modified alumina produced by the French Solvay Company. The alumina has a BET of 180m ² /g after aging at 1050°C for 4 hours as the carrier material. First, take an appropriate amount of deionized water, heat it to 40-60°C, and stir thoroughly; secondly, select K ₂ CO ₃ and Na ₂ CO ₃ as the potassium source and sodium source, and mix them in a mass ratio of 9:1 , to prepare an alkali solution; according to m(K ₂ CO ₃ +Na ₂ CO ₃ ): m(Al ₂ CO ₃ ) is 1:8.5-1:9 to determine the amount of alumina and the potassium and sodium sources. Dosage;

(2) Add the lanthanum-modified alumina material to the deionized water, control the final solid content to 20-30%, and control the pH of the solution to 3.8-4.2 during the addition process; then inject the alkali solution through a peristaltic pump. Add it to the alumina slurry, control the dropping time to 60-90 minutes, use nitric acid to adjust the pH of the slurry to maintain it between 3.8-4.2, and control the stirring time to 3.0-5.0h;

(3) The prepared alumina solution containing potassium salt and sodium salt is then dried by controlling the temperature of 100-150°C through a spray flash dryer. The drying efficiency reaches 95%-98 by controlling the feed rate. Between %; the dried powder is then calcined at high temperature in a rotary calciner, with a programmed heating rate of 5°C/min, and the final temperature is controlled at 900-1000°C and kept for 4.0h-6.0h. The process requires supplementary air. Carry out atmosphere protection;

(4) Prepare the calcined powder into a slurry. Since the KAlO ₂ material forms a spinel structure, in order to achieve uniform mixing of KAlO ₂ -Al ₂ O ₃ , wet grinding is required to obtain a uniform particle size. The slurry liquid is convenient for subsequent loading of main catalyst materials; control the solid content of the prepared slurry to 10-12%, add 1.0% (mass ratio to alumina) boehmite powder, and then add 6.0% (mass ratio to alumina) of hydroxymethyl cellulose, stir for 50-60 minutes, and a high-efficiency oxidation coating slurry to be applied in a wet state can be obtained;

(5) Choose the semi-transparent carrier with asymmetric structure of silicon carbide of NGK 300-10 or the semi-transparent carrier with asymmetric structure of cordierite of NGK 300-9, choose half of the air inlet end for coating, and control the loading amount to 15- 20g/L, and then dried and roasted to obtain the catalyst semi-finished product F;

(6) The catalyst semi-finished product F is subjected to hydrothermal aging treatment at 800°C for 20 hours. The mass ratio of water to catalyst semi-finished product F in the hydrothermal aging treatment is 1:10 to obtain the catalyst semi-finished product G;

(7) Perform sulfur poisoning treatment on the semi-finished catalyst product G. The treatment conditions are SO ₂ 200 ppm, O ₂ 10%, H ₂ O 10%, temperature 250°C, and time 16 hours to obtain the finished catalyst H.

The KAlO ₂ -Al ₂ O ₃ combination material in Embodiment 1 of the present invention is composed of nearly 10% spinel structure KAlO ₂ and nearly 90% γ-Al ₂ 0 ₃ connected through Al atoms.

The alkali metal material selected for the catalyst of the present invention can be any one of the alkali metal and alkaline earth metal families, containing Na, Cs, Ba, K, Li, Mg, but the combination of K and Na is preferred.

The transition metal raw materials selected for the catalyst of the present invention can be a variety of transition metal group elements of the B group, such as Cu, Co, Mn, Fe, V, Sn, Ni, W, etc.

The drying process in the preparation of the high-efficiency oxidation coating catalyst material of the present invention adopts spray flash drying, which can realize the rapid shaping of the loaded K and Na ions, thereby helping to achieve the dispersion rate requirements in the finished product.

The carrier of the DPF catalyst, in order to bring the reaction soot into closer contact with the high-efficiency oxidation coating of the catalyst, can be the known cordierite asymmetric semi-transparent carrier or the silicon carbide asymmetric semi-transparent carrier. It is recommended to use NGK’s 300-9 cordierite carrier or 300-10 silicon carbide carrier.

As one of the loading methods for DPF catalysts, when supported by an asymmetric semi-permeable wall flow carrier made of cordierite, when the DPF carrier oxidizes soot, in order to ensure a sufficiently high oxidation efficiency and regeneration mileage of the catalyst, it is best to It is based on the loading capacity of 15-20g/L. It not only ensures conversion efficiency but also reduces costs.

Binders suitable for supporting DPF catalysts are preferably boehmite and hydroxymethylcellulose. The optimum addition amounts are boehmite with a mass fraction of 1.0% of the molecular sieve and cellulose with a mass fraction of 6.0%.

For the catalyst of the present invention, a scanning electron microscope is used to observe the intensity change of the electron beam, and the material composition is analyzed based on information such as secondary electrons, absorbed electrons, and X-rays generated by the interaction between the electron beam and the material, so as to obtain the proportion of each element. The test results are shown in Figure 9.

For the catalyst of the present invention, XRD analysis equipment, full name X-Ray Diffraction (X-Ray Diffraction), is used to obtain the X-ray signal characteristics after diffraction by using the diffraction phenomenon of X-rays in the crystal, and the diffraction pattern is obtained after processing. The use of spectral information can not only determine the physical phase of a conventional microscope, but also have a "see-through eye" to see whether there are defects (dislocations) and lattice defects inside the crystal to determine the crystal structure type of the material.

According to the XRD test results, the material has a crystal structure of 70% Al2O3 and 28.5% KAl5O8. KAl4O8 is a KAlO2-2Al2O3 structure, indicating the formation of potassium metaaluminate with a spinel structure.

For the catalyst of the present invention, an electron scanning microscope is used to scan a certain plane of the high-efficiency oxidation coating powder for K element, and the spectrum shown in Figure 7 can be obtained.

For the catalyst of the present invention, an electron scanning microscope is used to scan a certain plane of the high-efficiency oxidation coating powder for Fe element, and the pattern shown in Figure 8 can be obtained.

From the scan data on the graph, the dispersion rate value of the active component can be calculated.

For the catalyst of the present invention, 40 mg of the sample was weighed out, degassed at a temperature of 200°C, and its BET specific surface area was measured using a nitrogen physical adsorption method (Shimadzu, Japan).

Take 50 mg of the catalyst, add 3 mL of HF and 3 mL of HNO3, dissolve it in a microwave oven, and then add nitric acid to the residue to further fully dissolve it. Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to analyze the composition of the catalyst components of the solution.

Use the FT-1R analysis device to simulate the gas composition of the exhaust gas. Set the reaction temperatures to 250°C, 300°C, 350°C, 400°C, 450°C, the NO ₂ /NOx ratio to 20%, and the space velocity to 60000h-1 Under the conditions, the oxidative combustion efficiency of the high-efficiency oxidation coating for soot was measured.

The National VI standard SINOTRUK MC13 engine was selected for efficiency testing, and temperatures of 300°C, 350°C, 400°C, 500°C, and 600°C were selected for testing to determine the oxidative combustion efficiency of the high-efficiency oxidation coating for soot, as shown in Figure 6 shown.

Comparative example 1:

Use pure alumina, a material with a BET test value <100m ² /g after aging at 1050°C for 4 hours, and prepare the coating material catalyst according to the following steps:

(1) First, take an appropriate amount of deionized water, heat it to 40-60°C, and stir thoroughly; secondly, select K ₂ CO ₃ and Na ₂ CO ₃ as the potassium source and sodium source, according to the mass ratio of 9:1 Mix in a proportion to prepare an alkali solution; determine the amount of alumina and the source of potassium and sodium according to m(K ₂ CO ₃ +Na ₂ CO ₃ ):m(Al ₂ CO ₃ ): 1:8.5-1:9 The amount of source taken;

(2) Add pure alumina material with a BET test value of <100m ² /g after aging at 1050°C for 4 hours into deionized water. Control the final solid content to 20-30%. During the addition process, control the pH of the solution to 3.8- 4.2; Then add the alkali solution to the alumina slurry by injection and dripping through a peristaltic pump. Control the dripping time to 60-90 minutes. During the process, the pH of the slurry is adjusted to 3.8-4.2 by using nitric acid. Between, control the stirring time to 3.0-5.0h;

(3) The prepared alumina solution containing potassium salt and sodium salt is then dried by controlling the temperature of 100-150°C through a spray flash dryer. The drying efficiency reaches 95%-98 by controlling the feed rate. Between %; the dried powder is then calcined at high temperature in a rotary calciner, with a programmed heating rate of 5°C/min, and the final temperature is controlled at 900-1000°C and kept for 4.0h-6.0h. The process requires supplementary air. Carry out atmosphere protection;

(4) Prepare the calcined powder into a slurry. Since the KAlO2 material forms a spinel structure, in order to achieve uniform mixing of KAlO2-Al2O3, wet grinding is required to obtain a slurry liquid with uniform particle size. To facilitate the subsequent loading of main catalyst materials; control the solid content of the prepared slurry to 10-12%, add 1.0% (mass ratio to alumina) boehmite powder, and then add 6.0% (mass ratio to alumina) The mass ratio of aluminum) to hydroxymethyl cellulose, stir for 50-60 minutes to prepare a wet, high-efficiency oxidation coating slurry to be applied;

(5) Choose the semi-transparent carrier with asymmetric structure of silicon carbide of NGK 300-10 or the semi-transparent carrier with asymmetric structure of cordierite of NGK 300-9, choose half of the air inlet end for coating, and control the loading amount to 15- 20g/L, and then dried and roasted to obtain the catalyst semi-finished product F;

(6) The catalyst semi-finished product F is subjected to hydrothermal aging treatment at 800°C for 20 hours. The mass ratio of water to catalyst semi-finished product F in the hydrothermal aging treatment is 1:10 to obtain the catalyst semi-finished product G;

(7) Perform sulfur poisoning treatment on the semi-finished catalyst product G. The treatment conditions are SO ₂ 200 ppm, O ₂ 10%, H ₂ O 10%, temperature 250°C, and time 16 hours to obtain the finished catalyst H.

Comparative example 2:

Use an alumina material modified with 10% lanthanum and aged at 1050°C for 4 hours with a BET test value of <100m2/g. Follow the following steps to prepare the coating material catalyst:

(1) First, take an appropriate amount of deionized water, heat it to 40-60°C, and stir thoroughly; secondly, select K ₂ CO ₃ and Na ₂ CO ₃ as the potassium source and sodium source, according to the mass ratio of 9:1 Mix in a proportion to prepare an alkali solution; determine the amount of alumina and the source of potassium and sodium according to m(K ₂ CO ₃ +Na ₂ CO ₃ ):m(Al ₂ CO ₃ ): 1:8.5-1:9 The amount of source taken;

(2) Add 10% lanthanum-modified alumina material with a BET test value <100m ² /g after aging at 1050°C for 4 hours into deionized water. Control the final solid content to 20-30%. Control during the addition process. The pH of the solution is 3.8-4.2; then the alkali solution is added to the alumina slurry by injection and dripping through a peristaltic pump. The dripping time is controlled to 60-90 minutes. During the process, the PH of the slurry is adjusted by nitric acid. Maintain it between 3.8-4.2, and control the stirring time to 3.0-5.0h;

(3) The prepared alumina solution containing potassium salt and sodium salt is then dried by controlling the temperature of 100-150°C through a spray flash dryer. The drying efficiency reaches 95%-98 by controlling the feed rate. Between %; the dried powder is then calcined at high temperature in a rotary calciner, with a programmed heating rate of 5°C/min, and the final temperature is controlled at 900-1000°C and kept for 4.0h-6.0h. The process requires supplementary air. Carry out atmosphere protection;

(4) Prepare the calcined powder into a slurry. Since the KAlO ₂ material forms a spinel structure, in order to achieve uniform mixing of KAlO ₂ -Al ₂ O ₃ , wet grinding is required to obtain a uniform particle size. The slurry liquid is convenient for subsequent loading of main catalyst materials; control the solid content of the prepared slurry to 10-12%, add 1.0% (mass ratio to alumina) boehmite powder, and then add 6.0% (mass ratio to alumina) of hydroxymethyl cellulose, stir for 50-60 minutes, and a high-efficiency oxidation coating slurry to be applied in a wet state can be obtained;

(5) Choose the semi-transparent carrier with asymmetric structure of silicon carbide of NGK 300-10 or the semi-transparent carrier with asymmetric structure of cordierite of NGK 300-9, choose half of the air inlet end for coating, and control the loading amount to 15- 20g/L, and then dried and roasted to obtain the catalyst semi-finished product F;

(6) The catalyst semi-finished product F is subjected to hydrothermal aging treatment at 800°C for 20 hours. The mass ratio of water to catalyst semi-finished product F in the hydrothermal aging treatment is 1:10 to obtain the catalyst semi-finished product G;

(7) Perform sulfur poisoning treatment on the semi-finished catalyst product G. The treatment conditions are SO ₂ 200 ppm, O ₂ 10%, H ₂ O 10%, temperature 250°C, and time 16 hours to obtain the finished catalyst H.

Comparing Example 1 with Comparative Example 1 and Comparative Example 2, the following data were obtained:

The comparison of DPF catalyst characteristics is shown in the table below:

BET Spinel structure proportion Dispersion uniformity of active ingredients Example 1 102m ² /g 10.1% 95% Comparative example 1 30m ² /g 6.8% 27% Comparative example 2 60m ² /g 3.2% 50%

Soot oxidation performance test:

When the above DPF catalyst body is exposed to a mixed gas of the following concentration (volume) at a prescribed temperature, time, space velocity, and a given amount of soot, the amount of soot is calculated relative to the amount of soot reduction on the DPF catalyst. Oxidation efficiency. The test conditions are as shown in the table below:

CO NO NO ₂ O ₂ N ₂ SV Soot 300ppm 320ppm 80ppm 10% balance 60000h-1 5g/L

The test results are shown in Figure 3.

It can be seen that it is very critical to determine whether the alumina is modified with appropriate lanthanum and praseodymium, and whether the BET value after aging at 1050°C for 4 hours is 150-200m2/g. The natural high-efficiency oxidation coating is essential for soot oxidation. There is also a big gap in efficiency.

For coating the finished high-efficiency oxidation coating slurry on the NGK cordierite 300-9 asymmetric semi-permeable wall flow carrier, it is necessary to strictly control the solid content of the slurry to 10-12% and the slurry particle size to 2.5-3.0 μm, the added amount of hydroxymethylcellulose is 6.0% of the mass fraction of alumina. According to the distribution of the coating on the DPF carrier and the pressure drop change of the finished product, as well as the final change in soot oxidation efficiency, it is demonstrated that the solid content, The particle size and cellulose addition amount can ensure that DPF has high soot oxidation efficiency, regeneration mileage and durability.

Example 2:

Follow the steps below to prepare the coating material catalyst:

(1) Select alumina modified with 5.0% lanthanum and praseodymium, with a BET of 180m2/g after aging at 1050°C for 4 hours as the carrier material. First, take an appropriate amount of deionized water, heat it to 40-60°C, and stir thoroughly; secondly, select K ₂ CO ₃ and Na ₂ CO ₃ as the potassium source and sodium source, and mix them in a mass ratio of 9:1 , to prepare an alkali solution; according to m(K ₂ CO ₃ +Na ₂ CO ₃ ): m(Al ₂ CO ₃ ) is 1:8.5-1:9 to determine the amount of alumina and the potassium and sodium sources. Dosage;

(2) Add the lanthanum-modified alumina material to the deionized water, control the final solid content to 20-30%, and control the pH of the solution to 3.8-4.2 during the addition process; then inject the alkali solution through a peristaltic pump. Add it to the alumina slurry, control the dropping time to 60-90 minutes, use nitric acid to adjust the pH of the slurry to maintain it between 3.8-4.2, and control the stirring time to 3.0-5.0h;

(3) The prepared alumina solution containing potassium salt and sodium salt is then dried by controlling the temperature of 100-150°C through a spray flash dryer. The drying efficiency reaches 95%-98 by controlling the feed rate. Between %; the dried powder is then calcined at high temperature in a rotary calciner, with a programmed heating rate of 5°C/min, and the final temperature is controlled at 900-1000°C and kept for 4.0h-6.0h. The process requires supplementary air. Carry out atmosphere protection;

(4) Prepare the calcined powder into a slurry. Since the KAlO ₂ material forms a spinel structure, in order to achieve uniform mixing of KAlO ₂ -Al ₂ O ₃ , wet grinding is required to obtain a uniform particle size. The slurry liquid is convenient for subsequent loading of main catalyst materials; control the detection particle size D50 to 2.5-3.0 μm, control the solid content of the prepared slurry to 10-12%, and add 1.0% (mass ratio to alumina) The boehmite powder is added, and then 6.0% (mass ratio to alumina) of hydroxymethyl cellulose is added, and stirred for 50-60 minutes to prepare a wet high-efficiency oxidation coating slurry to be applied. ;

(5) Use a cordierite DPF carrier of 190.5*152.4/300-9, select half of the air inlet end for coating, control the loading amount at 15-20g/L, and then dry and roast to obtain the catalyst semi-finished product F;

(6) The catalyst semi-finished product F is subjected to hydrothermal aging treatment at 800°C for 20 hours. The mass ratio of water to catalyst semi-finished product F in the hydrothermal aging treatment is 1:10 to obtain the catalyst semi-finished product G;

(7) Perform sulfur poisoning treatment on the semi-finished catalyst product G. The treatment conditions are SO ₂ 200 ppm, O ₂ 10%, H ₂ O 10%, temperature 250°C, and time 16 hours to obtain the finished catalyst H.

In Example 2, the various index parameters of the slurry are controlled as follows: the solid content is 10-12%, the slurry particle size is 2.5-3.0 μm, and the hydroxymethylcellulose addition amount is 6.0% of the alumina mass fraction. According to The distribution of the coating on the DPF carrier and the pressure drop of the finished product change, as well as the final change in soot oxidation efficiency.

It involves the parameter control of the finished high-efficiency oxidation coating slurry liquid and the control of the cellulose addition ratio, as well as the bridging effect of the coating on the DPF carrier wall, which is related to the surface tension value of the slurry on the carrier wall; the coating on the DPF The better the bridging effect of the wall is, the more and more uniformly the coating is dispersed on the surface of the wall channel, the larger the contact area with soot, and the higher the oxidation efficiency.

To achieve good distribution of high-efficiency oxidation coating materials on the DPF wall channels, it is necessary to explore the process and fix the parameters in terms of slurry solid content, particle size and cellulose addition amount to ensure that the DPF has a high soot oxidation efficiency. , regeneration mileage and durability performance.

Comparative example 3:

To adjust the slurry particle size value, follow the following steps:

(1) Select alumina modified with 5.0% lanthanum and praseodymium, with a BET of 180m2/g after aging at 1050°C for 4 hours as the carrier material. First, take an appropriate amount of deionized water, heat it to 40-60°C, and stir thoroughly; secondly, select K ₂ CO ₃ and Na ₂ CO ₃ as the potassium source and sodium source, and mix them in a mass ratio of 9:1 , to prepare an alkali solution; according to m(K ₂ CO ₃ +Na ₂ CO ₃ ): m(Al ₂ CO ₃ ) is 1:8.5-1:9 to determine the amount of alumina and the potassium and sodium sources. Dosage;

(2) Add the lanthanum-modified alumina material to the deionized water, control the final solid content to 20-30%, and control the pH of the solution to 3.8-4.2 during the addition process; then inject the alkali solution through a peristaltic pump. Add it to the alumina slurry, control the dropping time to 60-90 minutes, use nitric acid to adjust the pH of the slurry to maintain it between 3.8-4.2, and control the stirring time to 3.0-5.0h;

(3) The prepared alumina solution containing potassium salt and sodium salt is then dried by controlling the temperature of 100-150°C through a spray flash dryer. The drying efficiency reaches 95%-98 by controlling the feed rate. Between %; the dried powder is then calcined at high temperature in a rotary calciner, with a programmed heating rate of 5°C/min, and the final temperature is controlled at 900-1000°C and kept for 4.0h-6.0h. The process requires supplementary air. Carry out atmosphere protection;

(4) Prepare the calcined powder into a slurry. Since the KAlO ₂ material forms a spinel structure, in order to achieve uniform mixing of KAlO ₂ -Al ₂ O ₃ , wet grinding is required to obtain a uniform particle size. The slurry liquid is convenient for subsequent loading of main catalyst materials; control the detection particle size D50 to 4.0-4.5 μm, control the solid content of the prepared slurry to 10-12%, and add 1.0% (mass ratio to alumina) The boehmite powder is added, and then 6.0% (mass ratio to alumina) of hydroxymethyl cellulose is added, and stirred for 50-60 minutes to prepare a wet high-efficiency oxidation coating slurry to be applied. ;

(5) Use a cordierite DPF carrier of 190.5*152.4/300-9, select half of the air inlet end for coating, control the loading amount at 15-20g/L, and then dry and roast to obtain the catalyst semi-finished product F;

(6) The catalyst semi-finished product F is subjected to hydrothermal aging treatment at 800°C for 20 hours. The mass ratio of water to catalyst semi-finished product F in the hydrothermal aging treatment is 1:10 to obtain the catalyst semi-finished product G;

(7) Perform sulfur poisoning treatment on the semi-finished catalyst product G. The treatment conditions are SO ₂ 200 ppm, O ₂ 10%, H ₂ O 10%, temperature 250°C, and time 16 hours to obtain the finished catalyst H.

Comparative example 4:

To adjust the hydroxymethylcellulose addition ratio of the slurry, follow the steps below:

(1) Select alumina modified with 5.0% lanthanum and praseodymium, with a BET of 180m2/g after aging at 1050°C for 4 hours as the carrier material. First, take an appropriate amount of deionized water, heat it to 40-60°C, and stir thoroughly; secondly, select K ₂ CO ₃ and Na ₂ CO ₃ as the potassium source and sodium source, and mix them in a mass ratio of 9:1 , to prepare an alkali solution; according to m(K ₂ CO ₃ +Na ₂ CO ₃ ): m(Al ₂ CO ₃ ) is 1:8.5-1:9 to determine the amount of alumina and the potassium and sodium sources. Dosage;

(2) Add the lanthanum-modified alumina material to the deionized water, control the final solid content to 20-30%, and control the pH of the solution to 3.8-4.2 during the addition process; then inject the alkali solution through a peristaltic pump. Add it to the alumina slurry, control the dropping time to 60-90 minutes, use nitric acid to adjust the pH of the slurry to maintain it between 3.8-4.2, and control the stirring time to 3.0-5.0h;

(3) The prepared alumina solution containing potassium salt and sodium salt is then dried by controlling the temperature of 100-150°C through a spray flash dryer. The drying efficiency reaches 95%-98 by controlling the feed rate. Between %; the dried powder is then calcined at high temperature in a rotary calciner, with a programmed heating rate of 5°C/min, and the final temperature is controlled at 900-1000°C and kept for 4.0h-6.0h. The process requires supplementary air. Carry out atmosphere protection;

(4) Prepare the calcined powder into a slurry. Since the KAlO ₂ material forms a spinel structure, in order to achieve uniform mixing of KAlO ₂ -Al ₂ O ₃ , wet grinding is required to obtain a uniform particle size. The slurry liquid is convenient for subsequent loading of main catalyst materials; control the detection particle size D50 to 2.0-2.5 μm, control the solid content of the prepared slurry to 10-12%, and add 1.0% (mass ratio to alumina) The boehmite powder is added, and then 2.0% (mass ratio to alumina) of hydroxymethylcellulose is added, and stirred for 50-60 minutes to prepare a wet high-efficiency oxidation coating slurry to be applied. ;

(5) Use a cordierite DPF carrier of 190.5*152.4/300-9, select half of the air inlet end for coating, control the loading amount at 15-20g/L, and then dry and roast to obtain the catalyst semi-finished product F;

(6) The catalyst semi-finished product F is subjected to hydrothermal aging treatment at 800°C for 20 hours. The mass ratio of water to catalyst semi-finished product F in the hydrothermal aging treatment is 1:10 to obtain the catalyst semi-finished product G;

(7) Perform sulfur poisoning treatment on the semi-finished catalyst product G. The treatment conditions are SO ₂ 200 ppm, O ₂ 10%, H ₂ O 10%, temperature 250°C, and time 16 hours to obtain the finished catalyst H.

Comparative experiments were conducted between Example 2, Comparative Example 3 and Comparative Example 4:

The test conditions are introduced, mainly bench test equipment and packages.

Introduction to bench testing equipment:

Catalyst information introduction:

Carrier size vector wall Coating weight gain Example 2 190.5*152.4 300-9 18g/L Comparative example 3 190.5*152.4 300-9 18g/L Comparative example 4 190.5*152.4 300-9 18g/L

The data shown in Figure 4 is obtained.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any skilled person familiar with the art can utilize the above-disclosed technology without departing from the scope of the technical solution of the present invention. The contents are slightly changed or modified into equivalent embodiments with equivalent changes, but all modifications to the above embodiments are made without departing from the content of the technical solution of the present invention and based on the technical essence of the present invention and within the spirit and principles of the present invention. Any simple modifications, equivalent substitutions and improvements, etc., still fall within the protection scope of the technical solution of the present invention.

Claims (12)

1. A method for preparing a coating material catalyst, comprising the steps of:

s1: adding the lanthanum praseodymium modified aluminum oxide material into deionized water, controlling the final solid content to be 20-30%, and controlling the pH value of the solution to be 3.8-4.2 in the adding process; then adding alkaline solution into alumina slurry by peristaltic pump injection, controlling the dripping time to be 60-90 min, adjusting the pH value of the slurry liquid to be 3.8-4.2 by nitric acid in the process, controlling the stirring time to be 3.0-5.0h, forming mixed solution A, and obtaining the final productThe lanthanum praseodymium oxide in the lanthanum praseodymium modified alumina material accounts for 1.0% -4.0%, and the surface area of the lanthanum praseodymium oxide meets the requirement that the test value after heat aging for 4 hours under the aging condition of 1000 ℃ is not less than 150m ² The alkali solution is one or more carbonate solutions of Na, cs, K, li, the mass ratio of carbonate in the carbonate solution to alumina in alumina slurry is 1:8-1:9, the precursor of the selected lanthanum praseodymium modified alumina is of a lanthanum praseodymium aluminum common structure, the forming and roasting temperature of the precursor of the lanthanum praseodymium modified alumina is not less than 950 ℃ for not less than 5.0h, and the impurity content is controlled to be not more than 1.0%;

s2: drying the mixed solution A at 100-150 ℃ by a spray flash dryer, and controlling the feeding rate in the drying process to ensure that the drying efficiency is 95-98% to obtain powder B;

s3: the powder B is calcined at high temperature by a rotary calciner, the final temperature is controlled at 900-1000 ℃ for 4.0-6.0 h at a temperature programming rate of 5 ℃/min, and air is supplemented in the calcination process for atmosphere protection;

s4: preparing calcined powder into slurry C by wet grinding, and controlling the detection granularity D50 in the slurry C to be 2.5-3.0 mu m; adopting a laser particle size analyzer to perform particle size detection analysis, wherein the refractive index of 1.544 is selected in the test process, the light shielding rate of 13-15% of the particle addition amount is adopted, and the dispersion is performed by adopting ultrasonic waves for three minutes;

s5: injecting transition metal nitrate and noble metal nitrate into slurry C through a peristaltic pump after mixing the transition metal nitrate and the noble metal nitrate in deionized water, controlling the dripping time to be 60-90 minutes, regulating the pH value of the slurry liquid to be 3.8-4.2 through ammonia water in the process, and controlling the stirring time to be 1.0-2.0 hours to obtain slurry D, wherein the transition metal nitrate is any one or more of Cu, co, mn, fe, V, sn, ni, W, the ratio of the transition metal nitrate to the alumina in the alumina slurry is 0.03-0.06, and the ratio of the noble metal nitrate to the alumina in the alumina slurry is 0.005-0.01;

s6: controlling the solid content of the slurry D to be 10% -14%, adding a water-thinned aluminum powder, adding hydroxymethyl cellulose, and stirring for 30-60 minutes to obtain slurry E, wherein the mass ratio of the water-thinned aluminum powder to the alumina in the slurry D is 1:100-2:100, and the mass ratio of the hydroxymethyl cellulose to the alumina in the slurry D is 4:100-6:100;

s7: selecting a semi-permeable carrier with a silicon carbide asymmetric structure of NGK 300-10 or a cordierite asymmetric structure of NGK 300-9, selecting a half air inlet end for coating, controlling the loading amount to be 15-20g/L, and then drying and roasting to obtain a semi-finished catalyst F;

s8: carrying out hydrothermal aging treatment on the semi-finished product F of the catalyst, wherein the treatment condition is 800 ℃ for 20 hours, and the mass ratio of water to the semi-finished product F of the catalyst is 1:10 in the hydrothermal aging treatment to obtain a semi-finished product G of the catalyst;

s9: sulfur poisoning the semi-finished catalyst G under SO condition ₂ 200ppm，O ₂ 10%，H ₂ O10%, the temperature is 250 ℃ and the time is 16 hours, and the catalyst finished product H is prepared.

2. The method for preparing a catalyst for a coating material according to claim 1, wherein the alkali solution in the step S1 is a carbonate solution of at least two of Na, cs, K, li.

3. The method for preparing a catalyst for a coating material according to claim 1, wherein the mass ratio of carbonate in the carbonate solution to alumina in the alumina slurry in the step S1 is 1:8.5-1:9.

4. The method for preparing a catalyst for a coating material according to claim 1, wherein in the step S1, deionized water is added into a reaction kettle, the heating temperature is controlled to be 40-60 ℃, then lanthanum-modified alumina powder is added into the deionized water, the pH is maintained at 3.9-4.1, and the temperature is maintained at 40-60 ℃.

5. The method for preparing a catalyst for a coating material according to claim 1, wherein in the step S2, a laboratory type spray drying apparatus is used as the spray flash dryer, the power is 4.0kW, the inlet air temperature is 120-150 ℃, and the water evaporation amount is 1.0-1.5kg/h.

6. The method for preparing a catalyst for a coating material according to claim 1, wherein in the step S3, the temperature is raised to 200 ℃ for 1.0h, the bound water is evaporated, the temperature is raised to 600 ℃ for 2.0h, the pre-baking process is performed, and the temperature is raised to 950-1000 ℃ for 4.0-5.0 h.

7. The method for preparing a catalyst for a coating material according to claim 1, wherein in the step S4, the wet grinding is performed by a horizontal sand mill, zirconia beads with a particle size of 1.0-1.2mm are used, the grinding cavity volume is 0.5L, the filling amount of the zirconia beads is 70-75% of the total volume, and the power is 2.2kW.

8. The method for preparing a catalyst for a coating material according to claim 1, wherein in the step S5, ferric nitrate is added to deionized water, nickel nitrate is added to deionized water, and platinum nitrate is added to deionized water.

9. The method for preparing a catalyst for a coating material according to claim 1, wherein in the step S5, the stirring time is 60 to 70 minutes.

10. The method for preparing a catalyst for a coating material according to claim 1, wherein in the step S7, the coating is performed by a lower feeding method, a single side air inlet end is fed, a drying temperature is 100-120 ℃, and a baking temperature is 600-650 ℃.

11. A coated catalyst prepared by the method of any one of claims 1-10.

12. The application of the coating material catalyst is characterized in that the coating material catalyst is applied to purifying soot in tail gas of six-diesel engine vehicle types and non-road four-stage vehicle types.