CN112879125B - Diesel engine particle catcher coated with noble metal and non-noble metal catalysts in partition mode and preparation method thereof - Google Patents

Diesel engine particle catcher coated with noble metal and non-noble metal catalysts in partition mode and preparation method thereof Download PDF

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CN112879125B
CN112879125B CN202110072636.7A CN202110072636A CN112879125B CN 112879125 B CN112879125 B CN 112879125B CN 202110072636 A CN202110072636 A CN 202110072636A CN 112879125 B CN112879125 B CN 112879125B
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noble metal
slurry
metal catalyst
coating
carrier
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CN112879125A (en
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楼狄明
张允华
齐博阳
房亮
谭丕强
胡志远
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Tongji University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2807—Metal other than sintered metal

Abstract

The invention relates to a diesel engine particle catcher coated with noble metal and non-noble metal catalysts in a partition manner and a preparation method thereof. Compared with the prior art, the method has the advantages of reducing the cost and the like while efficiently reducing the emission of the particulate matters.

Description

Diesel engine particle catcher coated with noble metal and non-noble metal catalysts in partition mode and preparation method thereof
Technical Field
The invention relates to the technical field of diesel engine tail gas purification, in particular to a diesel engine particle catcher coated with precious metal and non-precious metal catalysts in a partition mode and a preparation method thereof.
Background
The diesel engine has good dynamic property and economy, and occupies a larger and larger proportion in the mobile source market. However, Particulate Matter (PM), one of its emissions, is seriously threatening the ecological environment and human health and is the chief culprit in persistent haze weather in many areas throughout the country. Generally, there are two methods for achieving the purification of particulate matter emitted from diesel engines: the method comprises the steps of internal purification and external purification, wherein the internal purification is to adjust the working state of an engine to reduce the emission of particulate matters, such as supercharging and inter-cooling, multi-valve, electric control high-pressure injection, exhaust gas recirculation, combustion chamber improvement and the like. The engine-out purification technology CDPF for discharging particulate matters of the diesel engine can effectively reduce the particulate matter discharge of 85-95% in exhaust, and becomes a key part for assembling a diesel engine mobile source to reach a high discharge standard. The catalytic oxidation, namely 'passive regeneration', is one of the most effective and direct methods for controlling the particulate matters discharged by the diesel engine, and the key implementation means of the method comprises the selection and the proportioning of the catalyst. However, the traditional noble metal catalyst coated on the carrier not only has the problems of high price (194 yuan/g, 545 yuan/g and 3360/g of noble metal platinum) and heat resistance, but also is sensitive to sulfur element in fuel and easy to be poisoned. Therefore, there is a need to find alternative catalyst materials that can achieve cost reduction and autonomous supply while ensuring catalytic properties.
The invention patent CN102400745B discloses a coating method of a three-way catalyst, wherein a first catalyst layer and a second catalyst layer which are prepared by two different three-way catalyst proportions are sequentially coated on the inner surface of a carrier from an air inlet to an air outlet. The content of the noble metal of the second catalytic layer is less than that of the first catalytic layer. The invention adopts a catalyst zone coating method, can ensure the cold start and the integral catalytic conversion performance of the three-way catalyst and simultaneously reduce the coating cost of the three-way catalyst, but still uses more noble metal catalysts, and the problems of cost, heat resistance and the like caused by the noble metal catalysts are not effectively relieved.
The invention patent CN108097258A discloses a monolithic non-noble metal catalyst. The catalyst adopts a honeycomb ceramic substrate, cerium oxide as a coating and non-noble metal oxide as an active component, and has good chlorine resistance and thermal shock resistance and small resistance. Compared with an integral noble metal catalyst, the cost of the invention is lower, but the emission of the non-noble metal catalyst in the low-temperature cold start stage is far different from that of the non-noble metal catalyst coated with the noble metal catalyst, so the actual emission reduction effect of the invention in the low-temperature cold start stage of the engine is not obvious.
Disclosure of Invention
The invention aims to provide a diesel particulate filter coated with precious metal and non-precious metal catalysts in a partition manner and a preparation method thereof, so that the cost is reduced while the particulate matter is efficiently reduced.
The purpose of the invention can be realized by the following technical scheme: the diesel engine particle trap comprises a carrier, and a noble metal catalyst and a non-noble metal catalyst which are coated on the carrier, wherein the noble metal catalyst is coated at the front end of the carrier, and the non-noble metal catalyst is coated at the rear end of the carrier. The diesel particulate filter coated in a subarea way can reduce the cost while ensuring higher catalytic efficiency.
Further, the noble metal catalyst coating length is 1/3 from the front end face of the carrier to the total length of the carrier, and the non-noble metal catalyst coating length is 2/3 from the tail end face of the carrier to the total length.
The noble metal catalyst comprises a Pt-Pd base noble metal catalyst, and the load of Pt-Pd is 10g/ft3~20g/ft3(ii) a The non-noble metal catalyst comprises a Cs-V base non-noble metal catalyst, and the load capacity of Cs-V is 30g/ft3~50g/ft3。
Compared with noble metals, the non-noble metal raw materials have abundant reserves and low price, and the prepared catalyst has better sulfur resistance and thermal aging resistance. The non-noble metal catalyst prepared based on the Cs-V group has low cost and better ignition activity and oxygen storage capacity.
The Pt-Pd base noble metal catalyst at the front end of the carrier has low ignition temperature and strong catalytic activity, can exert the advantage of the catalytic activity when cold starting at low temperature, enhances the efficiency of the passive regeneration of diesel particulate matters, has high catalytic activity under the non-low temperature environment, and simultaneously has good sulfur resistance and thermal stability. When the exhaust gas flow of an engine flows through a diesel particulate filter (CDPF) coated with precious metal and non-precious metal catalysts in a partition mode from the tail end of a DOC, the exhaust gas firstly passes through a carrier section coated with the precious metal catalyst, PM particles in the exhaust gas perform passive reaction under the synergistic action of the precious metal Pt-Pd, and the oxidation characteristic of the particles in a low-temperature environment is well exerted. The PM particulates in the exhaust gas then continue to be further catalytically oxidized in the support section coated with the Cs-V based non-noble metal catalyst. Because the price of the non-noble metal is greatly lower than that of the noble metal, the manufacturing cost of the CDPF can be greatly reduced by partially replacing the coated noble metal catalyst with the non-noble metal catalyst under the condition that the overall purification effect of the CDPF is not influenced, and the external requirement of the noble metal is reduced.
The carrier is in a honeycomb ceramic wall flow type structure, the material is cordierite or SiC, the porosity of the carrier is 50-60%, the wall thickness of the carrier is 3-10 mil, and the pore density of the carrier is 300-600 cpsi. The invention is matched with the characteristics of high temperature resistance, good strength and long service life of the SiC carrier, utilizes the variable price characteristic of a non-noble metal special electronic layer structure to develop the catalyst with excellent performance, realizes flexible control, reduces the cost, and promotes the sustainable development in the field of mobile source exhaust purification.
Al is sequentially arranged between the carrier and the catalyst2O3A layer and a rare earth oxide coating.
Further, the rare earth element oxide comprises CeO2Or La2And O. The rare earth element has the function of storing oxygen, namely storing oxygen under the condition of lean combustion and releasing oxygen under the condition of rich combustion, so that the oxygen fluctuation near the noble metal can be controlled, and the good catalytic oxidation effect of the catalyst is kept. Thus, CeO is used2Or La2O3And when the rare earth oxide is used as a catalyst auxiliary agent for layered coating, the catalytic oxidation effect of the catalyst on PM particles is further improved.
The inner core of the DPF wall-flow type particle trap consists of a base material, a supporter and a coating, wherein the base material of the DPF for the vehicle is generally made of porous ceramic materials. The compounds of the catalytic noble/non-noble metal catalysts are generally not applied directly to the substrate, but are instead first coated with a layer of Al2O3The support in the form of capillary pores forms the "attachment surface" for the catalyst. On the one hand, the specific surface area in contact with the exhaust gas flow is increased, and on the other hand, the coating amount is saved compared with the direct coating of the catalyst on the substrate. Meanwhile, the diesel engine is rich in combustion under most working conditions and has sufficient oxygen content. However, in order to prevent the air-fuel ratio from being too rich or too lean under some conditions, Al is used2O3On the basis of which a second layer of CeO is coated2Or La2O3When the rare earth oxide is used as a catalyst auxiliary agent, the oxygen is stored and released in time, so that the improvement is further realizedThe catalyst has a catalytic oxidation effect on PM particles; the third layer is finally coated with a noble or non-noble metal catalyst which plays a main catalytic role. Thus, a synergistic effect of the multilayer coating is formed.
Meanwhile, in the preparation process of the coating slurry, the proper grinding particle size is selected, so that the catalyst sample can be reasonably dispersed and suspended in multiple media, and the consistency and reliability of the slurry are ensured.
A preparation method of the diesel particulate filter coated with the noble metal and non-noble metal catalysts in a partition mode comprises the following steps:
(1) preparing Al2O3Slurrying and mixing Al2O3Coating the slurry on the surface of a carrier to prepare Al on the surface of the carrier2O3A layer;
(2) preparing rare earth element oxide slurry, and coating the rare earth element oxide slurry on Al2O3Forming a rare earth oxide coating on the layer;
(3) preparing slurry containing a noble metal catalyst and slurry containing a non-noble metal catalyst, coating the slurry containing the noble metal catalyst on the front end of the rare earth element oxide coating, and coating the slurry containing the non-noble metal catalyst on the rear end of the rare earth element oxide coating.
Further, said Al2O3The preparation method of the slurry comprises the following steps: mixing Al2O3Adding zirconium acetate and deionized water according to the weight ratio of 0.92-0.98: 0.05-0.1, fully and uniformly stirring, then dropwise adding nitric acid to adjust the pH of the slurry to be below 5.0, and adding Al2O3The particle size of the slurry is ground to D90 of 2-20 μm.
The preparation method of the rare earth element oxide slurry comprises the following steps: adding the rare earth element oxide and the alumina gel binder into deionized water according to the weight ratio of 0.85-0.95: 0.01-0.02, fully and uniformly stirring, then grinding the granularity of rare earth element oxide slurry until D90 is 2-20 mu m, and dropwise adding tartaric acid to adjust the pH of the slurry to be below 5.0.
The preparation method of the slurry containing the noble metal catalyst comprises the following steps: mixing Al2O3Adding beta-molecular sieve and zirconium acetate into deionized water according to the weight ratio of 0.65-0.85: 0.15-0.3: 0.02-0.04, fully stirring uniformly, grinding the slurry until the D90 is 2-20 mu m, adding noble metal [ Pt (NH)3)4](OH)2And [ Pd (NH)3)4](OH)2The solution is fully stirred, and then tartaric acid is added dropwise to adjust the pH of the slurry to be below 5.0.
The preparation method of the slurry containing the non-noble metal catalyst comprises the following steps: mixing Al2O3Adding the beta-molecular sieve and zirconium acetate into deionized water according to the weight ratio of 0.65-0.85: 0.15-0.3: 0.02-0.04, fully stirring uniformly, grinding the slurry until the D90 is 2-20 mu m, adding non-noble metal CsNO3And NH4VO3The slurry is stirred well and then tartaric acid is added dropwise to adjust the pH of the slurry to below 5.0.
The invention explores the synergistic catalytic action of noble metal and non-noble metal catalysts, designs the diesel particulate trap based on the partitioned coating of noble metal and non-noble metal, makes the best use of the noble metal and the non-noble metal by utilizing the difference of catalytic properties.
Compared with the prior art, the invention has the following advantages:
1. the invention cooperates with the advantages and characteristics of noble metal and non-noble metal catalysts, and the noble metal and non-noble metal catalysts are coated in a partition way, so that the advantages of the noble metal and non-noble metal catalysts are exerted, the cost is reduced, the exhaust conversion efficiency in the whole time period is ensured, and the invention has important engineering significance;
2. the invention passes through Al between the carrier and the catalyst2O3The arrangement of the layer and the rare earth element oxide coating ensures the strength and stability of the whole structure, and simultaneously keeps the good catalytic oxidation performance of the catalyst through the synergistic effect of the layers;
3. the Cs-V base non-noble metal catalyst used in the invention has rich raw material reserves, low cost, better ignition activity and oxygen storage capacity, combines the characteristics of high temperature resistance, good strength and long service life of the SiC carrier, develops a catalyst with excellent performance by utilizing the valence variation characteristic of a non-noble metal special electronic layer structure, realizes flexible control, reduces the cost and promotes the sustainable development in the field of mobile source exhaust purification;
4. according to the invention, through the screening of the coating positions, the coating areas and the loading amounts of the noble metal catalyst and the non-noble metal catalyst, the cost is reduced, and the integral high catalytic efficiency is ensured;
5. the Cs-V base non-noble metal catalyst has high catalytic activity in a non-low temperature environment, has good sulfur resistance and thermal stability, and solves the problems of low heat resistance, easy poisoning and the like caused by noble metal catalysts.
Drawings
FIG. 1 is a graph of particulate matter emission test data for a diesel particulate trap that has been coated with a precious metal catalyst and a non-precious metal catalyst alone;
FIG. 2 is a graph of particulate matter emissions test data for a diesel particulate trap that has been coated with a precious metal catalyst and a non-precious metal catalyst alone;
FIG. 3 is a schematic structural diagram of a diesel particulate trap carrier coated with precious metal and non-precious metal catalysts in a partition manner according to the present invention;
FIG. 4 is a cross-sectional view of a precious metal and non-precious metal catalyst zone coated diesel particulate trap according to the present invention;
FIG. 5 is a schematic view of the installation location of the precious metal and non-precious metal catalyst zone coated diesel particulate trap of the present invention;
in the figure: 1-support, 11-first region, 12-second region, 2-Al2O3The catalyst comprises a layer, a 3-rare earth element oxide coating, a 4-catalyst, a 5-purifier shell, a 51-DOC and a 52-diesel engine particle trap.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The following examples are carried out on the premise of the technical scheme of the invention, and detailed embodiments and specific operation processes are given, but the scope of the invention is not limited to the following examples.
Example 1
Firstly, comparing the catalytic performances of a noble metal catalyst and a non-noble metal catalyst by analyzing the particulate matter emission test data of a diesel particulate trap singly coated with the noble metal catalyst and the non-noble metal catalyst:
passive regeneration: as shown in FIG. 1, the catalytic efficiency of the noble metal catalyst is slightly higher than that of the non-noble metal catalyst in a low-temperature (250-450 ℃) passive regeneration environment. On the other hand, with the rise of temperature, the catalytic performance of the non-noble metal catalyst gradually levels off that of the noble metal catalyst.
Active regeneration: as shown in fig. 2, the non-precious metal DPF at 550 ℃ exhibits very good regeneration efficiency, enabling active regeneration at lower temperatures. In the whole active regeneration stage, the catalytic efficiency of the non-noble metal catalyst is greatly superior to that of the noble metal. And no matter the content of NOx in gas is high or low, the regeneration capacity of the DPF coated by non-noble metal is higher than that of noble metal, and the high conversion rate of soot can be realized in a very short time. The lower the NOx content, the more distinct the difference in regeneration efficiency of the two coated catalysts.
Sulfur resistance: through the research on the related mechanism of the non-noble metal catalyst, due to the inherent property of the non-noble metal catalyst and the addition of the doped rare earth element auxiliary agent, the non-noble metal catalyst can show better sulfur resistance;
durability: through the endurance test, compared with the precious metal DPF, the non-precious metal DPF has low breakage rate after the endurance test and still has higher oxidation activity on the discharged particles.
In conclusion, in consideration of key indexes mainly affecting DPF performance, such as irreplaceable catalytic activity of precious metals in a low-temperature environment and good emission reduction rate of non-precious metals at a high-temperature stage, a method for coating the precious metal catalyst and the non-precious metal catalyst in a partition mode is provided, so that the two catalysts respectively play advantages, make up for the deficiencies of each other and reduce the cost at the same time.
A diesel particulate filter coated with noble metal and non-noble metal catalysts in a partition manner is shown in figures 3-4 and comprises a filter element positioned at the position of the filter elementA cylindrical carrier 1 on the outermost side and Al provided inside the carrier 1 in this order from the outside to the inside2O3Layer 2, rare earth element oxide coating 3 and catalyst 4, wherein, carrier 1 divides into the first region 11 of front end and the second region 12 that is located the rear end, and catalyst 4 includes noble metal catalyst and non-noble metal catalyst, and noble metal catalyst is located first region 11, and non-noble metal catalyst is located second region 12.
The preparation method of the diesel particulate filter coated with the noble metal and non-noble metal catalyst in a partition mode comprises the following specific steps:
step 1: mixing Al2O3Adding zirconium acetate into deionized water according to the weight ratio of 0.92-0.98: 0.05-0.1, fully and uniformly stirring to prepare first coating slurry, and then dropwise adding nitric acid to adjust the pH value of the slurry to be less than 5.0;
step 2: performing slurry ball milling, namely milling the first coating slurry by a planetary ball mill, wherein the rotating speed of the planetary ball mill is 280-380 r/min, the running time is 3-5 h, and the first coating slurry is milled until the granularity D90 of the slurry is 2-20 mu m;
and step 3: measuring solid content, namely putting 5g of slurry into a dry pot, putting the dry pot into a muffle furnace at 550-600 ℃ for roasting for 10-20 min, cooling to room temperature, weighing the powder mass, dividing the powder mass by 5g, and calculating to obtain the solid content of the first coating slurry;
and 4, step 4: coating, namely placing the carrier 1 at a coating cavity of a special quantitative coating machine, calculating a target wet weight gain according to the coating amount of 50-60 g/L and the measured solid content, adding the calculated first coating slurry into a slurry disc of the special quantitative coating machine, performing quantitative coating, and coating the first coating slurry on the surface of the carrier to form Al2O3A layer 2;
and 5: drying and roasting: drying and roasting the carrier 1 coated with the first coating slurry, and weighing;
step 6: adding CeO2Or La2O3Adding the aluminum adhesive binder into deionized water according to the weight ratio of 0.85-0.95: 0.01-0.02, fully and uniformly stirring, and preparing second coating slurry;
and 7: performing slurry ball milling, namely milling the second coating slurry by a planetary ball mill, wherein the rotating speed of the planetary ball mill is 280-380 r/min, the running time is 3-5 h, and the second coating slurry is milled until the granularity D90 is 2-20 mu m;
and 8: measuring solid content, namely putting 5g of second coating slurry into a dry pot, roasting the dry pot in a muffle furnace at 550-600 ℃ for 10-20 min, cooling to room temperature, weighing the mass of the powder, and dividing the mass by 5g to obtain the solid content of the second coating slurry;
and step 9: adjusting the pH of the slurry, slowly adding tartaric acid into the second coating slurry added with the noble metal, and adjusting the pH of the second coating slurry to be below 5.0;
step 10: coating, namely placing the carrier 1 at a coating cavity of a special quantitative coating machine, calculating the target wet weight gain according to the coating amount of 70-80 g/L and the measured solid content, adding the calculated second coating slurry into a slurry disc of the special quantitative coating machine, performing quantitative coating, and coating the second coating slurry on an Al layer2O3Forming a rare earth oxide coating 3 on the layer 2;
step 11: drying and roasting, namely drying and roasting the carrier 1 coated with the second coating slurry, and weighing;
step 12: preparing slurry by mixing Al2O3The beta-molecular sieve and the zirconium acetate are in a weight ratio of 0.65-0.85: 0.15-0.3: 0.02-0.04, adding the mixture into deionized water, and fully and uniformly stirring to prepare third coating slurry;
step 13: slurry ball milling: grinding the third coating slurry by a planetary ball mill, wherein the rotating speed of the planetary ball mill is 280-380 r/min, the running time is 3-5 h, and the granularity of the slurry is 2-20 mu m when the slurry reaches D90;
step 14: measuring solid content, namely putting 5g of third coating slurry into a dry pot, roasting the dry pot in a muffle furnace at 550-600 ℃ for 10-20 min, cooling to room temperature, weighing the mass of the powder, and dividing the mass by 5g to obtain the solid content of the third coating slurry;
step 15: adding noble metal solution to add noble metal [ Pt (NH) ]3)4](OH)2And [ Pd (NH)3)4](OH)2Slowly adding the solution into the slurry after ball milling, and stirring for 2-8 h until the active component noble metal Pt-Pd solution is completely dispersed in the third coating slurry, wherein the total amount of Pt-Pd is 10-20 g/ft3；
Step 16: adjusting the pH of the slurry, namely slowly adding tartaric acid into the third coating slurry added with the noble metal, and adjusting the pH of the third coating slurry to be below 5.0;
and step 17: coating, namely placing 1/3 lengths of the front end of the carrier 1 at a coating cavity of a special quantitative coating machine, calculating a target wet weight gain according to the coating amount of 80-90 g/L and the measured solid content, adding the calculated third coating slurry into a slurry tray, performing quantitative coating, and coating the third coating slurry on the rare earth element oxide coating 3 to form a noble metal catalyst layer;
step 18: drying and roasting: drying and roasting the carrier 1 coated with the third coating slurry, and weighing;
step 19: adding non-noble metal CsNO into the solution3And NH4VO3Slowly adding the solution into the slurry subjected to ball milling in the step 13, and stirring for 2-8 hours until the non-noble metal Cs-V solution of the active component is completely dispersed in the third coating slurry, wherein the total amount of Cs-V is 30-50 g/ft3；
Step 20: adjusting the pH value of the slurry: slowly adding tartaric acid into the third coating slurry added with the noble metal, and adjusting the pH of the third coating slurry to be below 5.0;
step 21: coating, namely placing 2/3 lengths of the rear end of the carrier 1 at a coating cavity of a special quantitative coating machine, calculating a target wet weight gain according to the requirement of coating amount of 80-90 g/L and the measured solid content, adding the calculated third coating slurry into a slurry tray, performing quantitative coating, and coating the third coating slurry on the rare earth element oxide coating 3 to form a non-noble metal catalyst layer;
step 22: drying and roasting: the support 1 coated with the third coating slurry was dried and baked, and then weighed.
As shown in fig. 5, the diesel particulate trap 52 coated with the precious metal and non-precious metal catalysts prepared by the above method in a partitioned manner is installed in the purifier housing 5 and is disposed behind the DOC51, the Pt-Pd-based precious metal catalyst in the first region 11 at the front end of the carrier 1 has a low ignition temperature and a strong catalytic activity, and can exert its catalytic activity advantage at low-temperature cold start to enhance the efficiency of passive regeneration of diesel particulate matter, and the Cs-V-based non-precious metal catalyst also has a high catalytic activity in a non-low-temperature environment and has good sulfur resistance and thermal stability. When the engine exhaust gas flow flows through a diesel particulate filter (CDPF) coated with precious metal and non-precious metal catalysts in a partition mode from the tail end of the DOC51, the engine exhaust gas firstly passes through a carrier section coated with the precious metal catalysts, PM particles in the exhaust gas perform passive reaction under the synergistic action of the precious metal Pt-Pd, and the oxidation characteristic of the particles in a low-temperature environment is well exerted. The second zone 12 is then coated with a Cs-V based non-noble metal catalyst and PM particles in the exhaust continue to be further catalytically oxidized. Because the price of the non-noble metal is greatly lower than that of the noble metal, the coated noble metal catalyst is partially replaced by the non-noble metal catalyst under the condition that the whole purification effect is not influenced, the manufacturing cost of the CDPF can be greatly reduced, and the external requirement of the noble metal is reduced.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims (9)

1. A diesel engine particle catcher coated with noble metal and non-noble metal catalysts in a partition mode is characterized by comprising a carrier, and a noble metal catalyst and a non-noble metal catalyst which are coated on the carrier, wherein the noble metal catalyst is coated at the front end of the carrier, and the non-noble metal catalyst is coated at the rear end of the carrier;
al is sequentially arranged between the carrier and the catalyst2O3A layer and a rare earth oxide coating.
2. The diesel particulate trap of claim 1, wherein the precious metal catalyst coating length is 1/3 the total length of the carrier from the front end face of the carrier and the non-precious metal catalyst coating length is 2/3 the total length of the carrier from the rear end face of the carrier.
3. The precious and non-precious metal catalyst zoned-coated diesel particulate trap of claim 1, wherein the precious metal catalyst comprises a Pt-Pd based precious metal catalyst with a Pt-Pd loading of 10g/ft3~20g/ft3(ii) a The non-noble metal catalyst comprises a Cs-V base non-noble metal catalyst, and the load capacity of Cs-V is 30g/ft3~50g/ft3。
4. The diesel particulate trap of claim 1, wherein the support is a honeycomb ceramic wall flow structure made of cordierite or SiC, the porosity of the support is 50-60%, the wall thickness of the support is 3-10 mil, and the pore density of the support is 300-600 cpsi.
5. The precious and non-precious metal catalyst zoned-coated diesel particulate trap of claim 4, wherein the rare earth oxide comprises CeO2Or La2O。
6. A method for preparing the diesel particulate trap with the precious metal and non-precious metal catalyst zone coating function as recited in any one of claims 1 to 5, which comprises the following steps:
(1) preparing Al2O3Slurrying and mixing Al2O3Coating the slurry on the surface of a carrier to prepare Al on the surface of the carrier2O3A layer;
(2) preparing rare earth element oxide slurry, and coating the rare earth element oxide slurry on Al2O3Forming a rare earth oxide coating on the layer;
(3) preparing slurry containing a noble metal catalyst and slurry containing a non-noble metal catalyst, coating the slurry containing the noble metal catalyst on the front end of the rare earth element oxide coating, and coating the slurry containing the non-noble metal catalyst on the rear end of the rare earth element oxide coating.
7. The method of claim 6, wherein said Al is selected from the group consisting of Al, Cu, Ni, Cu, Al, Si, Al, and Al, Si, Al, or a mixture thereof2O3The preparation method of the slurry comprises the following steps: mixing Al2O3Adding zirconium acetate and deionized water according to the weight ratio of 0.92-0.98: 0.05-0.1, fully and uniformly stirring, then dropwise adding nitric acid to adjust the pH of the slurry to be below 5.0, and adding Al2O3The particle size of the slurry is ground to D90 of 2-20 μm.
8. The method of claim 6, wherein the rare earth oxide slurry is prepared by the steps of: adding the rare earth element oxide and the alumina gel binder into deionized water according to the weight ratio of 0.85-0.95: 0.01-0.02, fully and uniformly stirring, then grinding the granularity of rare earth element oxide slurry until D90 is 2-20 mu m, and dropwise adding tartaric acid to adjust the pH of the slurry to be below 5.0.
9. The method of claim 6, wherein the slurry containing the precious metal catalyst is prepared by: mixing Al2O3Adding beta-molecular sieve and zirconium acetate into deionized water according to the weight ratio of 0.65-0.85: 0.15-0.3: 0.02-0.04, fully stirring uniformly, grinding the slurry until the D90 is 2-20 mu m, adding noble metal [ Pt (NH)3)4](OH)2And [ Pd (NH)3)4](OH)2Fully stirring the solution, and then dropwise adding tartaric acid to adjust the pH of the slurry to be below 5.0;
the preparation method of the slurry containing the non-noble metal catalyst comprises the following steps: mixing Al2O3Adding the beta-molecular sieve and zirconium acetate into deionized water according to the weight ratio of 0.65-0.85: 0.15-0.3: 0.02-0.04, fully stirring uniformly, grinding the slurry until the D90 is 2-20 mu m, adding non-noble metal CsNO3And NH4VO3The slurry is stirred well and then tartaric acid is added dropwise to adjust the pH of the slurry to below 5.0.
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