A kind of preparation method of rare earth base high-performance three-effect catalyst
Relating to the field and the present invention relates to the purifying vehicle exhaust technology, is a kind of preparation method of rare earth base high-performance three-effect catalyst.
Behind the background technology car engine start, produce carbon monoxide CO, imperfect combustion hydrocarbon HC and nitrogen oxide NO after the oil inflame
x, these are discharged with waste gas the harmful material of the person, and by automobile three-way catalyst bed.Under the effect of automobile three-way catalyst, the major part of these harmful substances can be converted into harmless composition water, carbon dioxide and nitrogen.These catalyst are supported catalyst active component such as noble metal platinum, palladium, rhodium, ruthenium etc. and be used to improve that the auxiliary agent, additive etc. of its catalytic action constitute on such as catalyst carriers such as aluminium oxide, silica, titanium oxide, complex rare-earth oxidate containing valuable metal materials normally.
Wherein, as the catalyst carrier of the important component part of this catalyst such as aluminium oxide, silica, titanium oxide, rare earth etc., be mainly used in to the activity of such catalysts component high specific surface and catalytic reaction proper pore structure is provided.These catalyst carriers, its specific area generally reaches 130~350m
2/ g, pore structure parameter comprise that average pore size and average pore volume all will meet the demands, as reach aperture and the 0.3cm of 110
3The pore volume of/g.Cordierite ceramic honeycomb matrix wherein, has the gas passage that is arranged in parallel, the shape of these passages has square, triangle etc., the wall thickness of passage can reach 0.1~0.25mm, average hole density can reach 200~800 hole/square inches, even higher can reach 1200 hole/square inches.
In the middle of the auxiliary agent of catalyst constitutes, main auxiliary agent is a cerium base complex rare-earth oxidate containing valuable metal material, this oxide material is except playing the co-catalyst effect that improves catalyst activity, also has good storage oxygen performance, promptly has the characteristic that under oxidizing atmosphere, absorbs oxygen, under reducing atmosphere, discharges oxygen, the characteristic of utilizing this oxygen to absorb, discharge can be widened three-way catalyst air-fuel ratio operation window width, more effectively three kinds of oxious components in the purifying exhaust air.In addition, add the performance that this complex rare-earth oxidate containing valuable metal can improve the noxious materials such as the anti-lead of anti-sulphur of the activity of three-way catalyst, the resistance to elevated temperatures that improves catalyst, catalyst effectively, and can reduce the use amount of noble metal by a relatively large margin.Therefore, complex rare-earth oxidate containing valuable metal has become the important auxiliary component of three-way catalyst preparation, and is irreplaceable.Simultaneously, different catalyst can be selected the complex rare-earth oxidate containing valuable metal of different performance for use, and the performance of catalyst is changed a lot, and the Preparation of catalysts cost respectively is very different, to satisfy different service conditions.These complex rare-earth oxidate containing valuable metals, all be on the basis of cerium oxide, add other oxide components, the oxide that comprises Zr, La, Pr, Nu, Y etc., and can adjust the chemical ratios of each part, the overall performance of composite is changed a lot, comprise that specific surface, pore structure, aperture and the pore volume of these rare earth composite materials distributes or the like.
Change the storage oxygen performance of catalytic activity that can be by adjusting modulation three-way catalysts such as the ratio that alumina catalyst support in the catalyst, auxiliary agent complex rare-earth oxidate containing valuable metal, catalytic active component noble metal etc. form, the performance of composition, the content of composition, resistance to elevated temperatures, catalyst etc. according to these.The present invention uses the complex rare-earth oxidate containing valuable metal catalysis material as important auxiliary agent equally, and utilizes the different physical and chemical performances of these materials to change the Practical Performance of three-way catalyst.
The exhaust combustion purification temperature of Fuel Petroleum car, different because of the content of polluter, can reach 700~800 ℃ when low, Gao Shineng reaches 1300 ℃.Common honeycomb catalyst, although the alumina support of carried noble metal catalyst component is by alkaline earth or rare earth metal, zirconia or silica etc. have carried out stabilization processes, but the aluminium oxide after stable at high temperature exposes the specific area that still is difficult to keep requirement after the long period to the open air.Some catalyst stability under higher temperature is better, but is difficult to adapt to pollutant load condition with higher in the tail gas.
Although the patent of three-way catalyst also has much at present, various methods have been taked in the improvement of three-way catalyst, the alumina support that is included on the structure and composition on the ceramic honeycomb carrier, uses improve and add in the selection of auxiliary agent, the complex rare-earth oxidate containing valuable metal material of the distinct methods preparation used and forming is gone up and the optimization etc. that adds various compositions in catalyst, all done very big effort, and also obtained very big progress, the various aspects of performance of three-way catalyst has obtained very big raising.And rely on these progressive, make three-way catalyst be widely used, become auto industry and satisfying important assurance fast-developing under the environmental requirement prerequisite.But in the use of present three-way catalyst, still there are a lot of problems, the anti-plumbous performance of anti-sulphur that mainly comprises catalyst is not strong, heat-resisting quantity can meet the demands, activity of such catalysts descends very fast under higher temperature, even the coating shedding of generation catalyst, causing that activity of such catalysts completely loses etc., these have all had a strong impact on the result of use of catalyst.Although people have also proposed a lot of solutions, but still well do not solve at present, the in addition high-level requirement of having to from fuel oil aspect that automobile uses, comprise the strictness control of the plumbous equal size of noxious material sulphur in the fuel oil, strictness control of rare hydrocarbon content, arene content, alkane content ratio etc. in the fuel oil, to satisfy the higher instructions for use of catalyst on the one hand, bring into play the catalytic action of catalyst on the other hand again to greatest extent so that pollutant emission drops to minimum.
One of summary of the invention purpose of the present invention is the various aspects of performance that is intended to improve to a certain extent catalyst by the raw material of adjusting Preparation of Catalyst and improvement Preparation of catalysts technology etc.The catalyst of preparation improves from the many-sides such as carrying method of the raw material that adopt, preparation technology, noble metal, makes catalyst obtain improving significantly at the air-fuel ratio operation window width of catalytic activity, resistance to elevated temperatures, catalyst, the aspects such as low temperature ignition performance of catalyst.
The catalyst of the present invention's preparation is formed and comprised that at least three kinds of particles are dispersed on the ceramic matrix: load has the thermally-stabilised of Pt family metal or the stable aluminium oxide particles of process La, Ba; Containing Pt family metal plays catalytic action or does not contain the metal oxide particle that Pt family metal plays promoter effect, comprise complex rare-earth oxidate containing valuable metal, as Ce-Zr, or add the solid solution or the composite oxide material of one or more formation such as La, Y, Nu, Pr, Ba therein; The particle of heat-staple inert fill material comprises the highly stable Alpha-alumina of high temperature, perovskite, calcium oxide, barium monoxide, cordierite, mullite, aluminum magnesium titanate etc.The composition mixing and the structure thereof of above-mentioned multiple composition are compound, extraordinary catalyst coat material can be provided, this material had both had great high-temperature resistant, can combine very firm again with ceramic honeycomb carrier, and can when using lower noble metal amount, also reach good catalytic activity.
The invention provides a kind of new method, promptly do and mix pre-abrasive method, can comprise cordierite ceramic honeycomb, alumina support, complex rare-earth oxidate containing valuable metal, various additives etc. so that each part of catalyst can reach good coupling.It is the new technology of powder processing that the dry state mixing machinery grinds, and not only can change particle size and reduce, and can improve the particularly surface-active of stuff and other stuff of particle.By this method, can guarantee the high degree of dispersion of noble metal at carrier surface, for having good catalytic surface activity, catalyst created condition.Simultaneously by using improved alumina material, complex rare-earth oxidate containing valuable metal material etc., not only make activity of such catalysts component high degree of dispersion after the grinding, and owing to granularity reduce with granularity evenly resistance to elevated temperatures is improved, even under the high temperature more than 1000 ℃, the activity of such catalysts component can sintering.In addition, also the selected a certain amount of inert material of this method in catalyst preparation process comprises cordierite, mullite, Alpha-alumina etc., and key just is these high temperature resistant inert materials, can increase the bond strength of catalyst coat and ceramic honeycomb.
Known have a lot of method for preparing catalyst, they generally are divided into two kinds of preparation process: the active oxidation aluminized coating of pre-coated high-ratio surface or contain the mixed oxide coatings that aluminium oxide, rare earth oxide, other additive etc. are formed on ceramic honeycomb, by again the noble metal active component being loaded to after certain heat treatment on the aforesaid ceramic honeycomb carrier that contains the high-ratio surface coating, pass through certain heat treatment again, or be prepared into catalyst after the reduction processing; Another preparation process is the active oxidation aluminized coating of pre-coated high-ratio surface on ceramic honeycomb or contains the mixed oxide coatings that aluminium oxide, rare earth oxide, other additive etc. are formed, after certain heat treatment, the mixed oxide slurry that will contain the noble metal active component again is coated on the aforesaid ceramic honeycomb carrier that contains the high-ratio surface coating, pass through certain heat treatment again, or be prepared into catalyst after the reduction processing.Above-mentioned coated process can be carried out one or many according to bullion content.
The present invention and above-mentioned catalyst preparation process are different, the main distinction has been to adopt the existing rare earth based composite oxide material through the template preparation, the extraordinary alumina support of high-fire resistance energy, and through the mixed pre-coated slurry of using that the special process process prepares catalyst that grinds of overdrying.But the coated process one or many of this catalyst is finished.
The present invention is a kind of preparation method of rare earth base high-performance three-effect catalyst, it is characterized in that its coated process comprises to be prepared as follows technical process:
1. the selection of raw material:
1) select suitable active aluminum oxide carrier, specific surface is generally 120~300m
2/ g, pore volume is greater than 0.3cm
3/ g, average pore size is more than 100 , granularity is that D90 is below 25 μ m.
2) select suitable rare earth based composite oxides, specific surface is generally at 65~150m
2/ g, pore volume is greater than 0.2cm
3/ g, average pore size is more than 110 , granularity is that D90 is below 40 μ m.The amount of contained cerium and zirconium corresponds essentially to and obtains the required stoichiometric proportion of final purpose compound in these rare earth based composite oxides, and the atomic ratio of the cerium/zirconium that uses among the present invention can change in 1/9 to 9/1 scope.Simultaneously, also added in a certain amount of yttrium, lanthanum, praseodymium, the neodymium one or more, content is within 1%~15% scope.
3) select suitable precious metal salt solution, comprise the acidity or the alkaline solution of platinum nitrate, chloroplatinic acid, hexahydroxy platinic acid, ammonium chloroplatinate etc.; Rhodium nitrate, rhodium chloride solution, chlorine rhodate; Palladium nitrate, palladium bichloride, the acid of chlorine palladium etc.
4) brium carbonate, barium monoxide, barium acetate, barium hydroxide, barium sulfate; Calcium carbonate, calcium oxide, calcium sulfate; Zirconyl nitrate, zirconyl carbonate, zirconium hydroxide, zirconyl acetate, basic zirconium chloride; Cerous carbonate, cerous nitrate; Strontium carbonate, strontium nitrate; Magnesium carbonate, magnesium nitrate; Lanthanum nitrate, lanthanum carbonate; Salt or oxides such as alkali metal such as yttrium nitrate, yttrium carbonate, alkaline-earth metal, rare earth metal.
5) inert material such as Alpha-alumina, perovskite, calcium oxide, barium monoxide, cordierite, mullite, aluminum magnesium titanate etc.The specific area of above-mentioned powder is generally at 1~4m
2Between/the g, the granularity of powder is below 50 μ m.
6) acidic materials of Shi Yonging comprise nitric acid, acetic acid etc.The impurity content of above-mentioned acidic materials is below 1%.
7) alkaline matter of Shi Yonging comprises ammoniacal liquor, urea, potassium hydroxide etc.The content of impurities of above-mentioned alkaline matter is no more than 1%.
8) select suitable cordierite ceramic honeycomb matrix, hole density is 300~600 hole/square inches, square duct.This ceramic honeycomb can be homemade also can be the product of Corning Incorporated.General cell densities is 400 hole/square inches, and in 0.1~0.22mm scope, the wall thickness of typical homemade ceramic honeycomb is 0.16mm to wall thickness greatly, and the wall thickness of healthy and free from worry ceramic honeycomb is 0.12mm.
9) catalyst of the present invention's preparation, the various compositions and the content that contain are, the content of active aluminum oxide carrier is 20~150 grams per liters, the use amount of complex rare-earth oxidate containing valuable metal auxiliary agent is generally 15~200 grams per liters, inert powders such as various packing materials such as cordierite, mullite, Alpha-alumina are 10~100 grams per liters, the content of noble metal is generally 0.2~2 grams per liter, the ratio of Pt, Pd, three kinds of noble metals of Rh generally is controlled at Pt/Rh=15: 1 to 2: 1, Pd/Rh=10: 1 to 2: 1, Pt/Pd/Rh=10: 0: 1 to 0: 10: 1.Stablize aluminium oxide or rugged catalyst with La-Ba, its content is generally 0~5% of aluminium oxide or catalyst coat.
2. grind and the preparation slurries:
10) with above-mentioned gama-alumina separately or confuse rare going up and be ground to certain particle after composite oxides and a spot of alkali metal, alkaline-earth metal etc. mix, be generally D90 within the scope of 3~15 μ m.
11) with noble metal separately or mixed solution be immersed on the powder after the above-mentioned grinding, add certain amount of ammonia water or acetic acid solution then, carried out mixed grinding again 1~5 hour, preferred 2~4 hours, form the wettability mixture of powders.
12) with above-mentioned powder under 120~180 ℃ of temperature dry 1~5 hour, 400~600 ℃ of calcinings 1~5 hour down, preferred 2~3 hours.
13) with the powder after wettability mixture of powders or the calcining, with inert substances such as an amount of Alpha-alumina, perovskite, calcium oxide, barium monoxide, cordierite, mullite, aluminum magnesium titanate separately or mixture etc. fully mix.
14) in said mixture, add the deionized water, acetate, nitric acid of appropriate amount, an amount of ammoniacal liquor etc. and make flowable slurries.
15) above-mentioned slurries are transferred to several the liter in the big or small ball grinder, the pH value that adds an amount of acid solution or alkali lye adjustment slurries adds a spot of defoamer within 2~5 scopes, carry out ball milling then in ball grinder, time is at 4~24 hours, until the particle size D90 of slurries below 10 μ m.
16) slurries after taking-up is ground add liquid to solid contents such as acid, alkali or deionized water and reach 20%~45%.
3. coated and calcining and activating:
17) be immersed among the above-mentioned slurries with ceramic honeycomb matrix or the ceramic honeycomb matrix that contains precoated shet, take out after 10~40 seconds, purge, put into 100~250 ℃ of dryings of drying box 5~20 hours, reach more than 75% to dehydration rate with compressed air.Drying is carried out under air or under the inert atmosphere.
18) the catalyst blank after the preliminary hydro-extraction is put into muffle furnace and is carried out high-temperature calcination.400~650 ℃ of calcining heats, 30 minutes~5 hours time.Calcining is to carry out under air or under the inert atmosphere.
19) after the calcining, needs own and application need according to catalyst at high temperature carry out reduction activation to catalyst.Reduction be in hydrogen atmosphere or reducing atmosphere under carry out.
The rare earth based three-way catalyst of the present invention's preparation, in preparation process, can be as required, pre-coated a kind of active aluminum oxide carrier on the ceramic honeycomb matrix, or directly carry out the coated of catalyst coat.But pre-coated active oxidation aluminized coating must add material such as alumina sol makes the very firm of coating combination.
Except carrying out individual layer coated, can carry out the coated of bilayer or multilayer according to the needs of practical application.Except carrying out individual layer coated, can carry out the coated of bilayer or multilayer according to the needs of practical application.This coated process can be for the first time coated simple repetition, also can be and coated the being very different first time.
The present invention is as a kind of preparation method of rare earth base high-performance three-effect catalyst, and its another feature is that its multilayer coated process comprises and is prepared as follows technical process:
1) contains at least a inert material in the slurries of ground floor and comprise Alpha-alumina, perovskite, cordierite, mullite, aluminum magnesium titanate etc., noble metal is mainly the independent or mixing salt solution of Rh, Pd, load on the active aluminum oxide carrier separately or jointly, these slurries are coated on the ceramic honeycomb carrier, after purging through compressed air, 100~250 ℃ of dryings are 5~20 hours in the baking oven.
2) second layer slurries can contain separate constituent or the blending constituent of Pt, Pd and Rh, and these compositions are prepared according to a certain percentage, load on active aluminum oxide carrier or the complex rare-earth oxidate containing valuable metal respectively or jointly.These slurries do not contain any above-mentioned inert material.
3) will be coated ground floor noble metal cermet honeycomb substrate immerse in the above-mentioned slurries, after 10~30 seconds, take out compressed air and purge and removes unnecessary slurries, put into 100~250 ℃ of dryings of drying box 5~20 hours, reach more than 75% to dehydration rate.Drying is carried out under air or under the inert atmosphere.
4) blank of above-mentioned catalyst is put into muffle furnace and calcine, 400~650 ℃ of calcining heats, 3~5 hours time.Calcining is to carry out under air or inert atmosphere.
5) catalyst of above-mentioned preparation also can carry out reduction activation.
As the preferred technical solution of the present invention, it is further characterized in that its coated process comprises and is prepared as follows technical process:
1. the selection of raw material:
1) preferred suitable rare earth based composite oxides, the atomic ratio of the cerium/zirconium that uses in these rare earth based composite oxides can be at 8-3: variation 1 scope in.Simultaneously, one or more in the yttrium of interpolation, lanthanum, praseodymium, the neodymium, content is within 1%~10% scope.
2) preferred suitable precious metal salt solution comprises the acidity or the alkaline solution of platinum nitrate, chloroplatinic acid etc.; Rhodium nitrate, rhodium chloride solution; Palladium nitrate, palladium bichloride etc.
3) preferred brium carbonate, barium monoxide, barium acetate; Calcium carbonate, calcium oxide; Zirconyl nitrate, zirconium hydroxide, zirconyl acetate, basic zirconium chloride; Cerous nitrate; Strontium nitrate; Magnesium nitrate; Lanthanum nitrate, lanthanum carbonate; Salt or oxides such as alkali metal such as yttrium nitrate, yttrium carbonate, alkaline-earth metal, rare earth metal.
4) catalyst of the present invention's preparation, preferred various composition and content are, the content of active aluminum oxide carrier is 20~120 grams per liters, the use amount of complex rare-earth oxidate containing valuable metal auxiliary agent is generally 15~150 grams per liters, inert powders such as various packing materials such as cordierite, mullite, Alpha-alumina are 10~80 grams per liters, the content of noble metal is generally 0.2~1.5 grams per liter, the ratio of Pt, Pd, three kinds of noble metals of Rh generally is controlled at Pt/Rh=10: 1 to 2: 1, Pd/Rh=8: 1 to 2: 1, Pt/Pd/Rh=8: 0: 1 to 0: 8: 1.Stablize aluminium oxide or rugged catalyst with La-Ba, its content is generally 0~3% of aluminium oxide or catalyst coat.
2. grind and the preparation slurries:
5) with noble metal separately or mixed solution be immersed on the powder after the above-mentioned grinding, add certain amount of ammonia water or acetic acid solution then, carry out mixed grinding again and be preferably 2~4 hours, form the wettability mixture of powders.
6) with above-mentioned powder under 120~180 ℃ of temperature dry 1~5 hour, 500~550 ℃ of preferred calcining heats, preferred 2~3 hours of calcination time.
3. coated and calcining and activating:
7) be immersed among the above-mentioned slurries with ceramic honeycomb matrix or the ceramic honeycomb matrix that contains precoated shet, take out after 10~40 seconds, purge, put into 100~250 ℃ of dryings of drying box 5~12 hours with compressed air.
8) the catalyst blank after the preliminary hydro-extraction is put into muffle furnace and is carried out high-temperature calcination.500~550 ℃ of calcining heats, 30 minutes~3 hours time.
Specific embodiment embodiment 1--embodiment 5 is the embodiment of a coated process.
Embodiment 1
1000 gram gama-alumina powder, specific surface 120 meters squared per gram, (Ce/Zr=9: 1) rare earth oxide, specific surface are 65 meters squared per gram to 700 grams, an amount of barium monoxide, zirconia, cerium oxide etc. mix, through ball milling to the certain particle scope, again with 20 the gram Pd palladium chloride solution, contain 2 the gram Rh rhodium chloride solution, appropriate alkaline liquor, carried out mixed grinding 2 hours, full and uniform back 150 ℃ of dryings 2 hours, 400 ℃ of air were calcined 2 hours down.(Ce/Zr=1: 9) mixing such as rare earth oxide, an amount of acetic acid, appropriate amount of deionized water, 100 gram alpha-alumina powders, 50 gram cordierite powders, 50 gram alumina sols are carried out ball milling and are become slurries with above-mentioned powder and the above-mentioned gama-alumina powder of 500 grams, 350 grams, cordierite honeycomb matrix with Unit 400 immerses in the pasting then, take out, purge excessive pasting with compressed air, drying is removed free water, calcines 150 minutes for 500 ℃.It is 1.4 grams per liters that the catalyst of preparation contains noble metal amount, and palladium/rhodium ratio is 10: 1.
Embodiment 2
800 gram gama-alumina powder, specific surface 230 meters squared per gram, 560 gram (Ce/Zr/La=8: 1: 1) rare earth oxides, specific surface is 85 meters squared per gram, an amount of brium carbonate, zirconium hydroxide, calcium oxide etc. mix, through ball milling to the certain particle scope, again with 18 the gram Pt platinum acid chloride solution, contain 1.2 the gram Rh chlorine rhodium acid ammonium solution, carried out mixed grinding 4 hours, full and uniform back 100 ℃ of dryings 5 hours, 600 ℃ of air were calcined 1 hour down.Above-mentioned powder is carried out ball milling with mixing such as the above-mentioned gama-alumina powder of 400 grams, the above-mentioned Ce/Zr/La rare earth oxide of 280 grams, an amount of acetic acid, appropriate amount of deionized water, 100 gram alpha-alumina powders, 50 gram cordierite powders, 50 gram alumina sols become slurries, cordierite honeycomb matrix with Unit 400 immerses in the pasting then, take out, purge excessive pasting with compressed air, drying is removed free water, calcines 60 minutes for 600 ℃.It is 0.5 grams per liter that the catalyst of preparation contains noble metal amount, and platinum/rhodium ratio is 15: 1.
Embodiment 3
1500 grams are with the gama-alumina powder of 3% cerium, lanthanum, 2% barium modification, specific surface 180 meters squared per gram, 700 gram (Ce/Zr=1: 9) rare earth oxide, specific surface is 110 meters squared per gram, an amount of barium hydroxide, zirconium carbonate, lanthana etc. mix, and with the palladium nitrate solution that contains 10 gram Pd, the rhodium nitrate solution that contains 5 gram Rh carries out mixed grinding and forms the wettability powder after about 4 hours, the calcining 2 hours down of 250 ℃ of dryings 1 hour, 600 ℃ of air.Above-mentioned powder is carried out ball milling with mixing such as the above-mentioned alpha-alumina powder of 100 grams, the above-mentioned Ce/Zr rare earth oxide of 350 grams, an amount of acetic acid, appropriate amount of deionized water, 50 gram cordierite powders, 50 gram alumina sols become slurries, cordierite honeycomb matrix with Unit 400 immerses in the pasting then, take out, purge excessive pasting with compressed air, drying is removed free water, calcines 3 hours for 400 ℃.It is 2.4 grams per liters that the catalyst of preparation contains noble metal amount, and palladium/rhodium ratio is 2: 1.
Embodiment 4
1500 grams are with 3% lanthanum, the gama-alumina powder of 2% barium modification, specific surface 135 meters squared per gram, 500 gram (Ce/Zr/Y=3: 1: 1) rare earth oxides, specific surface is 96 meters squared per gram, an amount of barium acetate, zirconium acetate, cerium oxide etc. mix, with the platinum nitrate solution that contains 10 gram Pt, containing the 5 gram rhodium nitrate solutions of Rh and proper quantity of lye carries out mixed grinding form wettability powder (D90 is less than 15 microns) to certain particle size, with above-mentioned powder and the above-mentioned alpha-alumina powder of 30 grams, 150 gram above-mentioned Ce/Zr/La (Ce/Zr/La=8: 1: 1) rare earth oxides, an amount of acetic acid, appropriate amount of deionized water, 50 gram cordierite powders, mixing such as 50 gram alumina sols are carried out ball milling and are become slurries, cordierite honeycomb matrix with Unit 400 immerses in the pasting then, take out, purge excessive pasting with compressed air, drying is removed free water, calcines 30 minutes for 550 ℃.It is 0.65 grams per liter that the catalyst of preparation contains noble metal amount, and platinum/rhodium ratio is 2: 1.
Embodiment 5
1000 grams, 1% barium monoxide is stablized the gama-alumina powder, and specific surface 160 meters squared per gram are impregnated into the H that contains 15 gram Pt
2Pt (OH)
6In the ammonia spirit, the stable gama-alumina powder of 500 gram 3% lanthanums, specific area is 135 meters squared per gram, be impregnated in the rhodium nitrate solution that contains 3 gram Rh, the stable gama-alumina powder of 500 gram 1% barium monoxide, specific area is 160 meters squared per gram, be impregnated in the solution of the palladium bichloride that contains 3 gram Pd, above-mentioned powder and barium acetate, zirconium hydroxide, cerium oxide etc. mix, carry out ball milling 3 hours to granularity D90 less than 15 microns, add 100 gram alpha-alumina powders again, 20 gram cordierite powders, 30 gram alumina sols, 1000 gram complex rare-earth oxidate containing valuable metal (60%La2O3,10%CeO2,22%Nd2O3 8%Pr6011) becomes slurries with ball millings such as water and acetate, and the cordierite honeycomb matrix of Unit 400 immerses in the pasting, take out, purge excessive pasting with compressed air, drying is removed free water, calcines 30 minutes for 500 ℃.It is 0.9 grams per liter that the catalyst of preparation contains noble metal amount, and platinum/rhodium/palladium ratio is 5: 1: 1.
Embodiment 6
This example is as the embodiment of the coated technical process of multilayer.
Ground floor slurries: 1260 gram gama-alumina powder, specific surface 130 meters squared per gram, dipping contains the palladium chloride solution of 15 gram Pd, dipping contains the rhodium chloride solution of 2.5 gram Rh again, with 850 gram Ce/Zr/La (Ce/Zr/La=8: 1: 1) rare earth oxides, specific surface is 75 meters squared per gram, and mixing such as an amount of barium monoxide, zirconia, alpha-alumina powder, an amount of acetic acid, appropriate amount of deionized water, cordierite powder, alumina sol are carried out ball milling and become slurries.
Second layer slurries: 1000 grams are with the gama-alumina powder of 3~5% ceriums, lanthanum, 2% barium modification, specific surface 130 meters squared per gram, with the platinum nitrate solution that contains 10 gram Pt, the rhodium nitrate solution that contains 2.5 gram Rh, carry out mixed grinding and form the wettability powder of abundant dispersion, carry out ball milling with mixing such as an amount of acetic acid of Ce/Zr/La/Y rare earth oxide (specific surface is 72 meters squared per gram), deionized waters again and become slurries.
Cordierite honeycomb matrix with Unit 400 immerses in the ground floor slurries then, and compressed air purges excessive pasting, and drying is removed free water, calcines 30 minutes for 500 ℃.Immerse in the second layer slurries, compressed air purges excessive pasting again, and drying is removed free water, calcines 60 minutes for 500 ℃.It is 20 gram/cubic feet that the catalyst of preparation contains noble metal amount, and palladium // platinum rhodium ratio is 3: 2: 1.
Comparative example 1
Earlier the slurries that are coated with aluminium oxide and cerium oxide mixture are dipped on the honeycomb substrate, and then with active constituent loading to cated honeycomb substrate.(specific area is 110m to ball milling by the mix powder of 1000g aluminium oxide (90wt%) and cerium oxide (10wt%)
2/ g), 75mlHNO
3And 965mlH
2The mixed liquor that O forms, slurries dilute after through 16.5 hours grinding, and the cordierite honeycomb carrier that 264 ducts are arranged on the cross section is per square inch immersed in these slurries, reach 1.42g/in until the content of honeycomb substrate floating coat
3This cated honeycomb substrate is immersed by H
2PtCl
6And Na
2PdCl
6In the solution of forming (containing 0.337%Pt and 0.142%Pd), behind the certain hour carrier is taken out, blow away unnecessary liquid with compressed air.Feed H
2S15 minute, spend deionised water, 120 ℃ of dryings, 500 ℃ of calcination, the catalyst of preparation contains 0.91g.Pt/ and rises and the 0.488g.Pd liter.
Comparative example 2
1000g alumina powder (cerium oxide that contains 95% aluminium oxide and 5%) is immersed in and contains 383gNi (CHO
2)
22H
2In the solution of the ammonia of O.Powder is 200 ℃ of oven dry in stove, and 650 ℃ were burnt 2 hours.In the basic aqueous solution dipping with the hexahydroxy platinic acid that contains 11.5gPt, and then be immersed in the Rh (NO that contains 1.65gRh
3)
3In the aqueous solution of 120ml glacial acetic acid.Powder that obtains and 450mlH
2O mixes the back ball milling.Behind the ball milling 19 hours, total specific surface is no more than 1m
2/ g cell densities is that the cordierite honeycomb carrier in 400 holes is immersed in the above-mentioned slurries, reaches the 122g/ liter until coating, takes out to blow away unnecessary slurries, and is dry and 500 ℃ of burnings.The catalyst that obtains at last contains the 1.24g.Pt/ liter, 0.177g.Rh/ liter and 18.31g.NiO/ liter.
Comparative example 3
The preparation of first coating:
The 1750g specific area is 150m
2(load 10% other oxide, ratio is 10CeO to the alumina support of/g
2: 88ZrO
2: 2CaO), be placed in the ball mill and H2Pt (OH) the 6 mono aminoethane aqueous solution that contain 15.43gPt, mixed 20 minutes, add 2 gram glacial acetic acids again, the particle diameter more than the ball milling to 90% is less than 10 μ.200 gram specific areas are 100m
2The cerium oxide of/g mixes 20 minutes one-tenth one slurries, and its solid content is 44%.The honeycomb substrate of Unit 400 immerses in first pasting, purge, 110 ℃ of dried overnight, 500 ℃ of calcinings 1 hour, to load capacity be the 109g/ liter.
The preparation of second coating:
660 gram specific areas are 150m
2The aluminium oxide of/g and 660 gram deionized waters mixed 5 minutes in another ball mill, added the H that contains 4.65gPt
2Pt (OH)
6The mono aminoethane aqueous solution, mixed 20 minutes.Then the 10.22g Barium Nitrate Crystal is added and mixed 20 minutes, add 13 gram glacial acetic acids again, the above particle diameter of ball milling to 90% is less than 10 μ.
800g contains 12% cerium oxide and 88% zirconic composite oxides, specific surface is 52m2/g, add the palladium nitrate solution that contains the rhodium nitrate solution of 5.4gRh and contain 0.812gPd, the total amount of two solution is 140 grams, pH is less than 1.0, promptly in 1.5 hours, in conformal powdered, slowly add Rh-Pd solution, mixed again 1.5 hours.120 ℃ of dry wet-millings, 500 ℃ of calcinings in the air.Then with this powder and above-mentioned slurries, deionized water, mixing such as glacial acetic acid, the above particle diameter of ball milling to 90% is less than 10 μ.
The honeycomb substrate that scribbles first coating is immersed (solid content is 33%) in second pasting respectively, 100 ℃ of dryings, 500 ℃ of calcinings, the bullion content that obtains is the 0.7g/ liter,
Initiation temperature evaluation before and after above-mentioned catalyst wears out respectively.Data see Table the initiation temperature evaluating data table that 1-the inventive method is implemented the aging front and back of comparative example.
Appreciation condition is: φ 25 * 50 catalyst, air speed 50000h
-1, the consisting of of normal mixture: O
22.5%, H
2O10%, H
20.4 SO~0.8%,
20.02%, HC (C
3H
6: C
3H
81) 0.15%, CO1.5%, NO0.1%=2:.
Aging condition is: calcining is 50 hours in 1050 ℃ of following air.
Table 1-the inventive method is implemented the initiation temperature evaluating data table of the aging front and back of comparative example
Catalyst | Initiation temperature (℃) |
Fresh catalyst | Aging rear catalyst |
????CO | ????HC | ????NOx | ????CO | ????HC | ????NOx |
Embodiment 1 | ????220 | ????256 | ????245 | ????267 | ????301 | ????298 |
Embodiment 2 | ????216 | ????268 | ????255 | ????278 | ????311 | ????288 |
Embodiment 3 | ????218 | ????266 | ????257 | ????282 | ????309 | ????301 |
Embodiment 4 | ????205 | ????254 | ????248 | ????268 | ????312 | ????294 |
Embodiment 5 | ????203 | ????244 | ????238 | ????272 | ????316 | ????306 |
Embodiment 6 | ????208 | ????232 | ????223 | ????276 | ????318 | ????320 |
Comparative example 1 | ????216 | ????257 | ????244 | ????281 | ????323 | ????310 |
Comparative example 2 | ????218 | ????267 | ????256 | ????290 | ????323 | ????333 |
Comparative example 3 | ????224 | ????253 | ????249 | ????289 | ????319 | ????328 |
As can be seen from the table, fresh catalyst is suitable with the initiation temperature in the comparative example to the initiation temperature of three kinds of pollutants in the embodiment of the invention 1,2,3, but aging back will be lower than the initiation temperature of comparative example catalyst to the initiation temperature of three kinds of pollutants, shows that 1,2,3 the catalyst tolerates high-temperature behavior of embodiment is better than comparative example.And to embodiment 4,5,6, fresh catalyst all will be lower than comparative example with the initiation temperature of catalyst afterwards to three kinds of pollutants that wear out, and shows that this embodiment activity of such catalysts and resistance to elevated temperatures all are better than the comparative example catalyst.