CN101850248A - Tail gas purification catalyst and preparation method thereof - Google Patents
Tail gas purification catalyst and preparation method thereof Download PDFInfo
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- CN101850248A CN101850248A CN200910106261A CN200910106261A CN101850248A CN 101850248 A CN101850248 A CN 101850248A CN 200910106261 A CN200910106261 A CN 200910106261A CN 200910106261 A CN200910106261 A CN 200910106261A CN 101850248 A CN101850248 A CN 101850248A
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Abstract
The invention discloses a tail gas purification catalyst and a preparation method thereof. The tail gas purification catalyst comprises a catalyst precursor and a protective layer, wherein the catalyst precursor comprises a porous matrix and a catalytic active layer positioned on the porous matrix, and the protective layer is positioned on the catalytic active layer; the catalytic active layer contains one or more of palladium, platinum and rhodium; the protective layer contains aluminum oxide; and the porosity of the protective layer is 0.05 to 0.3ml/g, the thickness is 3 to 25 microns, and the weight of the protective layer is 10 to 100g/l based on the volume of the porous matrix. The invention also discloses the preparation method for the tail gas purification catalyst. The tail gas purification catalyst can remarkably improve the durability of the catalyst and prolong the service life thereof under the condition of basically keeping the initial catalytic efficiency of the catalyst, and can reduce the descent speed of the catalytic activity.
Description
[technical field]
The present invention relates to a kind of tai-gas clean-up catalyst and preparation method thereof, especially a kind of three-way catalyst that is used for purifying automobile tail gas and preparation method thereof.
[background technology]
Along with developing of automobile industry, tail gas pollution problem paid more and more attention, effectively controlling tail gas pollution has become the environmental issue of being badly in need of solution.With noble metals such as palladium, platinum, rhodiums is that the three-way catalyst (TWC) of main active ingredient can play the effect that reduces the automobile exhaust pollution thing preferably, has obtained extensive use in automobile production.In tai-gas clean-up catalyst, pottery or metallic carrier are an indirect supporter, salic and coating rare earth oxide is only the true carrier of catalytic active component, it provides big and stable surface to make above the noble metal that possesses catalytic activity is dispersed in, and coating itself also has certain catalytic purification effect to vehicle exhaust.
The working environment of tai-gas clean-up catalyst is very abominable, not only is faced with effects such as high temperature, high humidity, thermal shock, causes the coating active component to run off or comes off.Composition in the tail gas is also very complicated, inevitable some poisonous substances that exist, as the zinc in the lead in the fuel oil, sulphur and the additive, phosphorus, these poisonous substance molecules chemisorbed on the catalyst surface active position forms strong adsorbing species, hinder the carrying out of reaction, the catalyst light-off time is prolonged, and toxic emission increases.These factors have all had a strong impact on the service life of catalyst, and the catalyst of exploitation high-durability (life-span is longer than 80000km even 160000km) has become the target that each major company is pursued.
Prior art mainly is to improve the durability of tai-gas clean-up catalyst from three aspects.It at first is the prescription that improves coating paste, the adhesion between raising coating and the carrier and the compactness extent of coating, as disclosing a kind of coating paste in the prior art, this slurry is a matrix with the modification composite alumina, add the coating paste of noble metal and surfactant, and before this slurry coating, carrier is carried out cleaning, the coating that obtains is difficult for be full of cracks and comes off.Next is the distribution that improves the durability of coating material itself or improve noble metal.As also disclosing a kind of oxygen storage components that contains manganese that is used for tai-gas clean-up catalyst in the prior art, though this material in long-time high temperature, hydro-thermal, contain in the atmosphere of sulfur dioxide and move, also can provide than zirconium and the high storage oxygen capacity of cerium.Perhaps will place base coat, and will resist the stronger platinum of poisoning capability mutually or rhodium places external skin, improve the sulfur poisoning-resistant ability of catalyst the palladium of sulfur sensitive.The consumption that also can improve noble metal simultaneously improves the durability of catalyst.
Though said method all has certain effect to improving durability of catalyst, cost is higher, and the effect of raising durability of catalyst is also not obvious.
[summary of the invention]
In order to overcome auto-exhaust catalyst weak point in service life in the prior art, durability is not high, and the problem that catalytic activity decline is fast the invention discloses a kind of tai-gas clean-up catalyst, and rise appreciably its service life, the durability height, and catalytic activity descends slowly.
Tai-gas clean-up catalyst disclosed by the invention comprises catalyst precarsor and protective layer, and described catalyst precarsor comprises porous matrix and the catalytic active layer that is positioned on the porous matrix, and described protective layer is positioned on the catalytic active layer;
Contain in palladium, platinum or the rhodium one or more in the described catalytic active layer;
Described protective layer contains aluminium oxide;
Described protective layer porosity is 0.05-0.3ml/g, and thickness is 3-25um, is benchmark with the volume of porous matrix, and described protective layer weight is 10-100g/l.
The invention also discloses the preparation method of above-mentioned tai-gas clean-up catalyst, comprising:
A, the preparation of employing coprecipitation contain the powder precipitation of aluminium, will make salic powder A behind powder precipitation roasting, the ball milling, and the average grain diameter of powder A is 1-20um;
B, powder A, binding agent, raising agent and deionized water are mixed, layer slurry that be protected is benchmark with protective layer slurry gross weight, described powder A content is 10-40wt%, binder content is 5-20wt%, and raising agent content is 0.2-5wt%, and surplus is a deionized water;
C, get the catalyst precarsor that contains porous matrix and catalytic active layer, the protective layer slurry that coating step b makes on the catalytic active layer that loads on the porous matrix obtains the described tai-gas clean-up catalyst that contains matcoveredn through roasting.
Tai-gas clean-up catalyst provided by the invention can not influence under the situation of the initial catalytic efficiency of catalyst substantially, obviously improves the durability and the service life of catalyst, reduces the decrease speed of catalytic activity.
[description of drawings]
Fig. 1 is a tai-gas clean-up catalyst disclosed by the invention duct viewgraph of cross-section;
Attached body tag explanation: 1, porous matrix; 2, catalytic active layer; 3, protective layer.
[specific embodiment]
In order to make technical problem to be solved by this invention, technical scheme and beneficial effect clearer, below the present invention is further elaborated.
In the waste gas purification field, especially the purifying vehicle exhaust field for improving catalytic efficiency, generally adopts porous material as supporting body, i.e. porous matrix.For making things convenient for tail gas to get rid of, increase the contact area of catalyst and tail gas, the raising catalytic efficiency adopts on porous matrix more, has a large amount of through holes along the direction of exhaust gas flow.Be attached with the catalytic active layer that contains noble metal on the duct in porous matrix, be used for cleaning of off-gas.The high-temperature tail gas high velocity stream of getting rid of from automobile engine is through the catalytic active layer of catalyst, the noble metal of catalytic activity laminar surface is when playing catalytic purification tail gas, be subjected to impacting greatly and high temperature corrosion, cause active noble metals to be very easy to inactivation, the catalytic efficiency of catalyst is descended significantly.
The present inventor is by a large amount of experiments, proposed a kind ofly can significantly improve the scour resistance of catalyst and the tai-gas clean-up catalyst in life-span, this tai-gas clean-up catalyst, comprise catalyst precarsor and protective layer, described catalyst precarsor comprises porous matrix and the catalytic active layer that is positioned on the porous matrix, and described protective layer is positioned on the catalytic active layer;
Contain in palladium, platinum or the rhodium one or more in the described catalytic active layer;
Described protective layer contains aluminium oxide;
Described protective layer porosity is 0.05-0.3ml/g, and thickness is 3-25um, is benchmark with the volume of porous matrix, and described protective layer weight is 10-100g/l.
Do not contain precious metal palladium, platinum or rhodium in this protective layer.
Described porous matrix is porous metals matrix well known in the art or porous ceramic matrices suitable, as ceramic honey comb, cordierite ceramic etc.This porous matrix can provide very large contact area, improves catalytic efficiency.This porous carrier can be commercially available, the cordierite honeycomb ceramic carrier of producing as Japanese NGK company.
The catalytic active layer that is positioned on the porous matrix can prepare by this area method commonly used, as gets boehmite, and cerium zirconium compound oxide joins in the deionized water, mixes; Obtain the aluminum oxide coating layer feed liquid through ball milling.Get the cordierite honeycomb ceramic matrix, the dip coating feed liquid is taken out then, adopts compressed air to blow the through hole road, and drying is placed on roasting in the Muffle furnace in air dry oven, promptly makes the ceramic body that has applied alumina layer.Preparation H
3RhCl
6Solution and Pt (NH
3)
4Cl
2Solution mixes, and obtains mixed solution; Get mixed solution, the ceramic body that dipping obtains previously permeates the back fully until solution and takes out drying, roasting, the catalyst precarsor that obtains containing porous matrix He be positioned at the catalytic active layer on the porous matrix.
Same this contains this porous matrix and can be commercially available with the catalyst precarsor that is positioned at the catalytic active layer on the porous matrix, as the three-way catalyst of Britain Zhuan Xin company production.
The content range of the palladium in the catalytic active layer, platinum or rhodium is a scope known in those skilled in the art, is benchmark as the volume with porous matrix, and described noble metal (palladium, platinum or rhodium) total content is 0.05-4g/l.If catalyst precarsor is commercially available, can when buying, select the catalyst precarsor of different bullion contents.
The protective layer that is positioned at the catalytic activity laminar surface is a loose structure, and porosity is 0.05-0.3ml/g, and thickness is 3-25um, is benchmark with the volume of porous matrix, and described protective layer weight is 10-100g/l.Under the preferable case, porosity is 0.1-0.25ml/g, and thickness is 5-15um, and protective layer weight is 20-50g/l.
Generally, in catalyst, be tail gas to be carried out catalytic purification by the active noble metals on the catalytic active layer; If at above-mentioned catalytic active layer surface coverage one protective layer; it inevitably can cover the noble metal composition on the catalytic active layer; the effective dose of active noble metals is reduced; and because the existence of this protective layer; increased the resistance to mass tranfer of tail gas, thereby caused the catalytic efficiency of catalyst to descend to catalytic active layer.But, the present inventor finds by a large amount of experiments, when the structure of this protective layer as mentioned above, the catalyst efficiency of preparation only can occur descending slightly at the use initial stage, growth along with service time, what on the one hand protective layer had been born tail gas stream directly washes away and has absorbed most noxious material, makes the catalytic efficiency of catalyst descend and not obvious; Specific coatings is washed away attenuation on the other hand, and the resistance to mass tranfer of tail gas reduces, and activity of such catalysts also progressively discharges, and the reason of two aspects makes that in the operation later stage catalytic efficiency of catalyst can obviously rise, even is higher than the catalyst that does not contain protective layer.Simultaneously, since the existence of this protective layer, the service life of this tai-gas clean-up catalyst that can rise appreciably.
In the above-mentioned tai-gas clean-up catalyst, its protective layer thickness is to all having certain influence the service life of catalytic activity and catalyst, and under the preferable case, protective layer thickness is 3-25um, more preferably 5-15um.Especially when the thickness of protective layer in the tai-gas clean-up catalyst disclosed by the invention is 10-15um, helps improving the service life of catalyst most and make catalytic efficiency remain on higher level.
Because the protective layer in the tai-gas clean-up catalyst is connected with catalytic active layer; for making the adhesive force height of protective layer and catalytic activity interlayer; compatibility is good; preferred this protective layer contains aluminium oxide, and further preferred this protective layer also contains one or more in rare-earth oxide, transition metal oxide or the alkaline earth oxide.The inventor finds; in this protective layer, contain aluminium oxide; when especially containing in rare-earth oxide, transition metal oxide or the alkaline earth oxide one or more; though there is resistance to mass tranfer; but the catalytic efficiency of this tai-gas clean-up catalyst is improved on the contrary, and also further prolonged the service life of catalyst.
Under the preferable case, above-mentioned rare earth metal is lanthanum and/or cerium; Transition metal is iron and/or zirconium; Alkaline-earth metal is one or more in magnesium, barium, calcium or the strontium.
The invention also discloses the preparation method of above-mentioned tai-gas clean-up catalyst, comprising:
A, the preparation of employing coprecipitation contain the powder precipitation of aluminium, will make salic powder A behind powder precipitation roasting, the ball milling, and the average grain diameter of powder A is 1-20um;
B, powder A, binding agent, raising agent and deionized water are mixed, layer slurry that be protected is benchmark with protective layer slurry gross weight, described powder A content is 10-40wt%, binder content is 5-20wt%, and raising agent content is 0.2-5wt%, and surplus is a deionized water;
C, get the catalyst precarsor that contains porous matrix and catalytic active layer, the protective layer slurry that coating step b makes on the catalytic active layer that loads on the porous matrix obtains the described tai-gas clean-up catalyst that contains matcoveredn through roasting.
In the tai-gas clean-up catalyst by method for preparing, the protective layer porosity is 0.05-0.3ml/g, and thickness is 3-25um, is benchmark with the volume of porous matrix, and described protective layer weight is 10-100g/l.
Coprecipitation is the method for this area trickle powder of preparation commonly used, but the microstructure of the powder that makes under the different preparation conditions also has bigger difference.And adopt the prepared powder structure of different raw materials also different.Under the preferable case, it is alumina powder jointed that the present invention adopts the main component of coprecipitation preparation.
Among the present invention, above-mentioned steps a specifically comprises:
1), the soluble-salt of one or more and aluminium in the soluble-salt of the soluble-salt of rare earth metal or transition metal is dissolved in deionized water, obtains solution B;
2), ammoniacal liquor and/or ammonium carbonate are dissolved in the deionized water, forming the pH value is the solution C of 8-11;
3), under stirring condition, solution B is joined in the solution C;
4), through ageing, filtering-depositing, washing, drying, roasting, ball milling, obtain powder A.
Wherein, the soluble-salt of the soluble-salt of rare earth metal or the soluble-salt of transition metal and aluminium can adopt various above-mentioned metal soluble salt class well known in the art, soluble chloride, sulfate or nitrate as above-mentioned various metals, under the preferable case, select the nitrate of above-mentioned various metals for use.More preferably above-mentioned rare earth metal is lanthanum and/or cerium; Transition metal is iron and/or zirconium.
Aluminum ions concentration is 1-5mol/l in the solution B, and the concentration of rare earth ion is 0-2mol/l, and the concentration of transition metal ions is 0-2mol/l.Being preferably aluminum ions concentration is 2-4mol/l, and the concentration of rare earth ion is 0-1mol/l, and the concentration of transition metal ions is 0-1mol/l.Above-mentioned various concentration is the total concentration of all kinds of metal ions, if contain more than one same metalloid ion in solution B, belongs to then that it doesn't matter between the of a sort various concentration of metal ions, only needs their total concentration to get final product in above-mentioned scope.The preparation method of above-mentioned solution B can not repeat them here for the method for this area various obtain solutions commonly used.
The method of above-mentioned obtain solution C also is this area method commonly used, and as ammoniacal liquor and/or ammonium carbonate are dissolved in the deionized water, the pH value of control solution C is at 8-11.Above-mentioned ammoniacal liquor and/or concentration of ammonium carbonate do not require, and only the pH value of the solution C that need make at last gets final product in above-mentioned scope.Under the preferable case, ammoniacal liquor and ammonium carbonate are present in the solution C with 1: 1 concentration.
After the preparation of solution B and solution C is finished, can be utilized effectively for making solution, be that 1: 1 amount is mixed solution B and solution C under stirring condition by the volume ratio of solution B and solution C.The mode that solution B and solution C are mixed can have multiple, as solution B is splashed in the solution C, also solution B and solution C can be fed two pipelines respectively, the mode that adopts and flow is mixed, keep the flow velocity of solution B certain, adjust the flow velocity of solution C, the pH value of controlling mixed solution is at 8-9.Under the preferable case, carry out under the above-mentioned 50-70 of being blended in ℃.
After mixing finishes, mixed solution is continued to stir 2h, still aging then 12h, filter, the sediment washing, the drying that obtain after filtration are at 400-800 ℃ of following roasting 1-10h again, after the cooling, be 1-20um, obtain powder A sediment ball milling to average grain diameter.Under the preferable case, the average grain diameter of powder A is 5-15um behind the control ball milling.
Above-mentioned powder A also can be commercially available, as the three-way catalyst r-aluminium oxide of Shanghai Sha Bo Chemical Industry Science Co., Ltd production.The average grain diameter of the powder A that is commercially available can be selected when buying, and preferably its average grain diameter is 1-20um.The powder A that satisfies instructions for use also can realize purpose of the present invention, but effect does not have powder A effective of method for preparing.
As another kind of preferred version, after step a, comprising that also the powder A that will make among the step a floods before the step b in the soluble-salt solution of alkaline-earth metal, drying, is that 1-20um obtains modified powder A in 400-800 ℃ of following roasting 1-10h roasting, ball milling to average grain diameter.Wherein, alkaline-earth metal ions concentration is 1-3mol/l in the soluble-salt solution of alkaline-earth metal, is preferably 1.5-2.5mol/l.Wherein alkaline-earth metal is preferably one or more in magnesium, barium, calcium or the strontium.The method of dipping powder A is this area method commonly used in the soluble-salt solution of employing alkaline-earth metal, as getting final product in the soluble-salt solution that powder A is immersed in alkaline-earth metal.
After powder A preparation is finished, powder A, binding agent, raising agent and deionized water are mixed, a layer slurry is protected, with protective layer slurry gross weight is benchmark, and described powder A content is 10-40wt%, and binder content is 5-20wt%, raising agent content is 0.2-5wt%, and surplus is a deionized water; Under the preferable case, powder A content is 10-30wt%, and binder content is 10-15wt%, and raising agent content is 0.5-2wt%.
The above-mentioned method for preparing the protective layer slurry is this area method commonly used, gets final product as placing ball mill to carry out ball milling powder A, binding agent, raising agent and deionized water.After powder A is carried out modification, obtain be modified powder A the time, during preparation protective layer slurry modified powder A, binding agent, raising agent and deionized water mixed getting final product.
Above-mentioned binding agent is preferably aluminium colloidal sol or zirconium colloidal sol; Described aluminium colloidal sol or zirconium colloidal sol are this area aluminium colloidal sol or zirconium colloidal sol commonly used, can obtain by being purchased or making by oneself, as the aluminium colloidal sol of peak in morning, Shengzhou city textile auxiliary Co., Ltd production.
Raising agent is preferably one or more in polyethylene glycol, polyvinyl alcohol, urea, methylol methylcellulose, HEMC or the hydroxypropyl methylcellulose.Above-mentioned various material as raising agent all can be commercially available, as the polyethylene glycol of Tianjin Tiancheng Pharmaceutical Co., Ltd.'s production.
Above-mentioned be purchased or homemade catalyst precarsor on the protective layer slurry that makes of coating step b; the method that applies is conventionally known to one of skill in the art; as carrier being immersed in a period of time in the protective layer slurry, take out then, blow away protective layer slurry unnecessary in the duct with compressed air and get final product.Can control the thickness of the protective layer that makes at last by the amount of the protective layer slurry that applies.
In the present invention; the porosity of the protective layer on the tai-gas clean-up catalyst that makes is at last tested by the following method and is obtained: the protective layer slurry for preparing is divided into two parts; a copy of it is coated on the catalyst precarsor; another part is coated on the blank porous matrix; keep the process conditions of twice coating identical, the catalyst precarsor and the blank porous matrix that will be coated with the protective layer slurry then carry out drying and roasting under identical conditions.The porosity of the protective layer on the blank porous matrix of last test can obtain the porosity of the protective layer on the corresponding tai-gas clean-up catalyst.Wherein, the porosity of the protective layer on the blank porous matrix adopts the test of water absorption rate method according to GB/T 2997.
After the protective layer slurry applied and finishes, the catalyst precarsor that will contain the matcoveredn slurry was in air, and 80-200 ℃ is descended dry 2-9h; Then at 400-800 ℃ of following roasting 2-9h.The protective layer slurry promptly forms above-mentioned protective layer after roasting, the tai-gas clean-up catalyst that obtains simultaneously is the above-mentioned tai-gas clean-up catalyst that contains matcoveredn.Above-mentioned drying and roasting can be finished in commonly used drying machine in this area and burning machine.
Tai-gas clean-up catalyst by method for preparing provided by the invention can keep obviously prolonging under the situation of its catalytic efficiency the service life of tai-gas clean-up catalyst to a certain extent.The present invention is further illustrated below by embodiment.
Present embodiment is used to illustrate tai-gas clean-up catalyst disclosed by the invention and preparation method thereof.
1, preparation powder Al
The 243g aluminum nitrate is dissolved in 1 liter of deionized water, makes solution B 1.Aluminum ions concentration is 1mol/l among the solution B l.
Secure ph is 10 ammonia spirit C11 liter.
At 60 ℃, under the intense agitation, solution B 1 and solution C 1 are joined in the deionized water simultaneously, and keeping the flow velocity of solution B 1 is 10ml/min, adjusts the speed of solution C 1, keep the pH of mixed value at 8-9, after treating that solution B 1 adds, stop to add solution C 1, keep temperature constant, continue to stir 2h, still aging 12h.Filtering-depositing, washing then; Dry 4h under 100 ℃ then at 500 ℃ of following roasting 4h, with sediment ball milling 2h, obtains powder Al, and its average grain diameter is 18um.
2, preparation protective layer slurry
Get 50g powder Al, 36g aluminium colloidal sol, 8g Macrogol 2000,106g deionized water mixing and ball milling, make the protective layer slurry.
3, catalyst precarsor preparation
Take by weighing the 100g boehmite, the 50g zeolite, the 45gCe-Zr-Ba composite oxides add the 300ml deionized water and mix, and make that its solid content is 40%, and 200r/min rotating speed ball milling 10 hours obtains the aluminum oxide coating layer feed liquid.Get the blank cordierite ceramic honey comb matrix A10 of 1L specification, dip coating feed liquid 5min takes out, and compressed air blows the through hole road, 100 ℃ of dry 4h of air dry oven, and 600 ℃ of roasting 4h of Muffle furnace promptly make the porous matrix that has applied alumina layer.Compound concentration is 0.1% H
3RhCl
6Solution and concentration are 0.15% Pt (NH
3)
4Cl
2Each 100ml mixes, and gets mixed solution 150ml, and the ceramic body that dipping obtains previously permeates the back fully until solution and takes out, 80 ℃ of dry 5h, and 650 ℃ of roasting 4h obtain catalyst precarsor A100.
4, preparation tai-gas clean-up catalyst
Get 200g protective layer slurry, be divided into two parts of A11 and A12.
Protective layer slurry A11 is coated on the catalyst precarsor A100 of 1L.
Protective layer slurry A12 is coated on the blank porous matrix A10 of 1L.
The catalyst precarsor that is coated with protective layer slurry A11 is placed 100 ℃ of dry 4h down together with the blank porous matrix that is coated with protective layer slurry A12, then at 500 ℃ of following roasting 4h.
Adopt the water absorption rate method to test the porosity of the protective layer on the blank porous matrix that is coated with protective layer slurry A12.
Obtain tai-gas clean-up catalyst S1, its protective layer thickness is 12um, and porosity is 0.28ml/g, and protective layer weight is 25g/l.
Present embodiment is used to illustrate tai-gas clean-up catalyst disclosed by the invention and preparation method thereof.
1, preparation powder A2
486g aluminum nitrate, 177.5g lanthanum nitrate are dissolved in 1 liter of deionized water, make solution B 2.Aluminum ions concentration is 2mol/l in the solution B 2, and lanthanum ion concentration is 0.5mol/l.
Secure ph is 11 sal volatile C21 liter.
At 60 ℃, under the intense agitation, solution B 2 and solution C 2 are joined in the deionized water simultaneously, and keeping the flow velocity of solution B 2 is 10ml/min, adjusts the speed of solution C 2, keep the pH of mixed value at 8-9, after treating that solution B 2 adds, stop to add solution C 2, keep temperature constant, continue to stir 2h, still aging 12h.Filtering-depositing, washing then; Dry 4h under 100 ℃ then at 500 ℃ of following roasting 4h, with sediment ball milling 2h, obtains powder A2, and its average grain diameter is 12um.
2, preparation protective layer slurry
Get 60g powder A2,24g zirconium colloidal sol, 4g methylol methylcellulose, 112g deionized water mixing and ball milling, make the protective layer slurry.
3, catalyst precarsor preparation
Take by weighing the 100g boehmite, the 50g zeolite, the 45gCe-Zr-Ba composite oxides add the 300ml deionized water and mix, and make that its solid content is 40%, and 200r/min rotating speed ball milling 10 hours obtains the aluminum oxide coating layer feed liquid.Get the blank cordierite ceramic honey comb matrix A20 of 1L specification, dip coating feed liquid 5min takes out, and compressed air blows the through hole road, 100 ℃ of dry 4h of air dry oven, and 600 ℃ of roasting 4h of Muffle furnace promptly make the porous matrix that has applied alumina layer.Compound concentration is 0.1% H
3RhCl
6Solution and concentration are 0.15% Pt (NH
3)
4Cl
2Each 100ml mixes, and gets mixed solution 150ml, and the ceramic body that dipping obtains previously permeates the back fully until solution and takes out, 80 ℃ of dry 5h, and 650 ℃ of roasting 4h obtain catalyst precarsor A200.
4, preparation tai-gas clean-up catalyst
Get 200g protective layer slurry, be divided into two parts of A21 and A22.
Protective layer slurry A21 is coated on the catalyst precarsor A200 of 1L.
Protective layer slurry A22 is coated on the blank porous matrix A20 of 1L.
The catalyst precarsor that is coated with protective layer slurry A21 is placed 100 ℃ of dry 4h down together with the blank porous matrix that is coated with protective layer slurry A22, then at 500 ℃ of following roasting 4h.
Adopt the water absorption rate method to test the porosity of the protective layer on the blank porous matrix that is coated with protective layer slurry A22.
Obtain tai-gas clean-up catalyst S2, its protective layer thickness is 14um, and porosity is 0.24ml/g, and protective layer weight is 30g/l.
Present embodiment is used to illustrate tai-gas clean-up catalyst disclosed by the invention and preparation method thereof.
1, preparation powder A3
486g aluminum nitrate, 71g lanthanum nitrate, 71g cerous nitrate, 170g zirconium nitrate are dissolved in 1 liter of deionized water, make solution B 3.Aluminum ions concentration is that the concentration of 2mol/l, lanthanum ion is that the concentration of 0.2mol/l, cerium ion is that the concentration of 0.2mol/l, zirconium ion is 0.5mol/l in the solution B 3.
Secure ph is 31 liters of the mixed solution C of 10 ammoniacal liquor and ammonium carbonate, and wherein, the amount of substance of ammoniacal liquor and ammonium carbonate is 1: 1.
At 60 ℃, under the intense agitation, solution B 3 and solution C 3 are joined in the deionized water simultaneously, and keeping the flow velocity of solution B 3 is 10ml/min, adjusts the speed of solution C 3, keep the pH of mixed value at 8-9, after treating that solution B 3 adds, stop to add solution C 3, keep temperature constant, continue to stir 2h, still aging 12h.Filtering-depositing, washing then; Dry 4h under 100 ℃ then at 500 ℃ of following roasting 4h, with sediment ball milling 2h, obtains powder A3, and its average grain diameter is 10um.
2, preparation protective layer slurry
Get 90g powder A3,30g aluminium colloidal sol, 1g Macrogol 2000,2g methylol methylcellulose, 177g deionized water mixing and ball milling, make the protective layer slurry.
3, catalyst precarsor preparation
Take by weighing the 100g boehmite, the 50g zeolite, the 45gCe-Zr-Ba composite oxides add the 300ml deionized water and mix, and make that its solid content is 40%, and 200r/min rotating speed ball milling 10 hours obtains the aluminum oxide coating layer feed liquid.Get the blank cordierite ceramic honey comb matrix A30 of 1L specification, dip coating feed liquid 5min takes out, and compressed air blows the through hole road, 100 ℃ of dry 4h of air dry oven, and 600 ℃ of roasting 4h of Muffle furnace promptly make the porous matrix that has applied alumina layer.Compound concentration is 0.1% H
3RhCl
6Solution and concentration are 0.15% Pt (NH
3)
4Cl
2Each 100ml mixes, and gets mixed solution 150ml, and the ceramic body that dipping obtains previously permeates the back fully until solution and takes out, 80 ℃ of dry 5h, and 650 ℃ of roasting 4h obtain catalyst precarsor A300.
4, preparation tai-gas clean-up catalyst
Get 150g protective layer slurry, be divided into two parts of A31 and A32.
Protective layer slurry A31 is coated on the catalyst precarsor A300 of 1L.
Protective layer slurry A32 is coated on the blank porous matrix A30 of 1L.
The catalyst precarsor that is coated with protective layer slurry A31 is placed 100 ℃ of dry 4h down together with the blank porous matrix that is coated with protective layer slurry A32, then at 500 ℃ of following roasting 4h.
Adopt the water absorption rate method to test the porosity of the protective layer on the blank porous matrix that is coated with protective layer slurry A32.
Obtain tai-gas clean-up catalyst S3, its protective layer thickness is 11um, and porosity is 0.25ml/g, and protective layer weight is 23g/l.
Embodiment 4
Present embodiment is used to illustrate tai-gas clean-up catalyst disclosed by the invention and preparation method thereof.
1, preparation powder A4
486g aluminum nitrate, 71g lanthanum nitrate, 71g cerous nitrate, 204g zirconium nitrate are dissolved in 1 liter of deionized water, make solution B 4.Aluminum ions concentration is that the concentration of 2mol/l, lanthanum ion is that the concentration of 0.2mol/l, cerium ion is that the concentration of 0.2mol/l, zirconium ion is 0.6mol/l in the solution B 4.
Secure ph is 41 liters of the mixed solution C of 10 ammoniacal liquor and ammonium carbonate, and wherein, the amount of substance of ammoniacal liquor and ammonium carbonate is 1: 1.
At 60 ℃, under the intense agitation, solution B 4 and solution C 4 are joined in the deionized water simultaneously, and keeping the flow velocity of solution B 4 is 10ml/min, adjusts the speed of solution C 4, keep the pH of mixed value at 8-9, after treating that solution B 4 adds, stop to add solution C 4, keep temperature constant, continue to stir 2h, still aging 12h.Filtering-depositing, washing then; Dry 4h under 100 ℃ then at 500 ℃ of following roasting 4h, with sediment ball milling 2h, obtains powder A4.
2, powder A modification
Above-mentioned powder A4 is immersed in 30min, filtering-depositing, washing then in the barium nitrate solution that concentration is 2mol/l; Dry 4h under 100 ℃ then at 500 ℃ of following roasting 4h, with sediment ball milling 2h, obtains modified powder A4, and its average grain diameter is 8um.
3, preparation protective layer slurry
Get 100g modified powder A4,40g aluminium colloidal sol, 2g Macrogol 2000,258g deionized water mixing and ball milling, make the protective layer slurry.
4, catalyst precarsor preparation
Take by weighing the 100g boehmite, the 50g zeolite, the 45gCe-Zr-Ba composite oxides add the 300ml deionized water and mix, and make that its solid content is 40%, and 200r/min rotating speed ball milling 10 hours obtains the aluminum oxide coating layer feed liquid.Get the blank cordierite ceramic honey comb matrix A40 of 1L specification, dip coating feed liquid 5min takes out, and compressed air blows the through hole road, 100 ℃ of dry 4h of air dry oven, and 600 ℃ of roasting 4h of Muffle furnace promptly make the porous matrix that has applied alumina layer.Compound concentration is 0.1% H
3RhCl
6Solution and concentration are 0.15% Pt (NH
3)
4Cl
2Each 100ml mixes, and gets mixed solution 150ml, and the ceramic body that dipping obtains previously permeates the back fully until solution and takes out, 80 ℃ of dry 5h, and 650 ℃ of roasting 4h obtain catalyst precarsor A400.
5, preparation tai-gas clean-up catalyst
Get 200g protective layer slurry, be divided into two parts of A41 and A42.
Protective layer slurry A41 is coated on the catalyst precarsor A400 of 1L.
Protective layer slurry A42 is coated on the blank porous matrix A40 of 1L.
The catalyst precarsor that is coated with protective layer slurry A41 is placed 100 ℃ of dry 4h down together with the blank porous matrix that is coated with protective layer slurry A42, then at 500 ℃ of following roasting 4h.
Adopt the water absorption rate method to test the porosity of the protective layer on the blank porous matrix that is coated with protective layer slurry A42.
Obtain tai-gas clean-up catalyst S4, its protective layer thickness is 9um, and porosity is 0.21ml/g, and protective layer weight is 25g/l.
Embodiment 5
Present embodiment is used to illustrate tai-gas clean-up catalyst disclosed by the invention and preparation method thereof.
The Preparation of catalysts process is identical with embodiment 1, and different is: adopt the aluminium oxide A5 (the three-way catalyst r-aluminium oxide that Sha Bo Chemical Industry Science Co., Ltd in Shanghai produces, average grain diameter is 10um) that is purchased to replace A1.
Obtain tai-gas clean-up catalyst S5, its protective layer thickness is 11um, and porosity is 0.26ml/g, and protective layer weight is 25g/l.
Comparative Examples 1
This Comparative Examples is used to illustrate tai-gas clean-up catalyst of the prior art and preparation method thereof.
The preparation method of tai-gas clean-up catalyst obtains tai-gas clean-up catalyst D1 with the preparation method of the catalyst precarsor among the embodiment 1.
Comparative Examples 2
This Comparative Examples is used for comparative illustration tai-gas clean-up catalyst disclosed by the invention and preparation method thereof.
The preparation method of tai-gas clean-up catalyst is identical with embodiment 4, and different is: the average grain diameter of the powder AD2 for preparing is 30um.
Obtain tai-gas clean-up catalyst D2, its protective layer thickness is 21um, and porosity is 0.35ml/g, and protective layer weight is 26g/l.
Comparative Examples 3
This Comparative Examples is used for comparative illustration tai-gas clean-up catalyst disclosed by the invention and preparation method thereof.
The preparation method of tai-gas clean-up catalyst is identical with embodiment 4, and different is: the average grain diameter of the powder AD3 for preparing is 20um.
During preparation protective layer slurry, get 200g powder AD3,20g aluminium colloidal sol, 2g Macrogol 2000,178g deionized water mixing and ball milling, make the protective layer slurry.
Obtain tai-gas clean-up catalyst D3, its protective layer thickness is 27um, and porosity is 0.23ml/g, and protective layer weight is 57g/l.
Performance test
The tai-gas clean-up catalyst sample S1-S5, the D1-D3 that prepare are all cut into diameter 23mm, the sample of long 40mm, put into quartz tube furnace, test tai-gas clean-up catalyst catalytic performance adopts the following method performance of the aging and test of simulation after aging fast then.
1, fresh sample catalytic performance test
In tubular reactor, feed the gaseous mixture of simulated automotive tail gas, and be warming up to 500 ℃ by room temperature with the temperature of the speed control gaseous mixture of 5 ℃/min.The gas concentration of measuring catalyst inlet and outlet with gas analyzer changes, and calculates each gas transformation efficiency, and the temperature that transforms with gas at 50% o'clock is the T of this gas
50Gaseous mixture consists of NO 1000ppm, SO
210ppm, CO 1.5%, C
3H
81000ppm, CO
210%, H
2O10%, O
24.8%, N
2Be balance gas.The gaseous mixture flow velocity is 11L/min.Be air speed 40000h
-1
2, simulation is aging fast
It is aging that phase I is that coating is washed away, and continues 30h, comprises 6 circulations altogether.Furnace temperature is warming up to 850 ℃ with the heating rate of 25 ℃/min by 100 ℃ in each circulation, and insulation 4h is cooled to 100 ℃ with same speed then.All stage, the steam volume content was 10% with the speed bubbling air of 33L/min and the mist of steam, and promptly air speed is 120000h
-1
Second stage is the catalyst quick aging, and furnace temperature is warming up to 1000 ℃ with the speed of 20 ℃/min, feeds the aging simulated exhaust gas of use, and insulation 5h lowers the temperature naturally.Simulated exhaust gas consists of: NO 1000ppm, SO
230ppm, CO 1.5%, C
3H
81000ppm, CO
210%, H
2O 10%, O
25%, N
2Be balance gas, reaction velocity is 60000h
-1
Fast the aging sample of simulation is reentered into quartz tube furnace through after weighing and calculating the coating weight loss, the catalytic performance after specimen is aging, and step is as follows:
In tubular reactor, feed the gaseous mixture of simulated automotive tail gas, and be warming up to 500 ℃ by room temperature with the temperature of the speed control gaseous mixture of 5 ℃/min.The gas concentration of measuring catalyst inlet and outlet with gas analyzer changes, and calculates the gas transformation efficiency, and the temperature that transforms with gas at 50% o'clock is the T of this gas
50Gaseous mixture consists of NO 1000ppm, SO
210ppm, CO 1.5%, C
3H
81000ppm, CO
210%, H
2O 10%, O
24.8%, N
2Be balance gas.The gaseous mixture flow velocity is 11L/min.Be air speed 40000h
-1
Initiation temperature after noting initial initiation temperature respectively and wearing out, wherein, what initial initiation temperature embodied is the catalytic performance of fresh tai-gas clean-up catalyst, and initial initiation temperature is low more, and the catalytic performance of fresh catalyst is good more, and catalytic efficiency is high more; Aging back initiation temperature embodies is catalytic performance after tai-gas clean-up catalyst work a period of time, and aging back initiation temperature is low more, and the damage that tai-gas clean-up catalyst is subjected to is more little, and its life-span is also just long more.
The test result that obtains is as shown in table 1.
Table 1
From the test result of table 1 as can be seen, than tai-gas clean-up catalyst of the prior art, be improved significantly the service life of the tai-gas clean-up catalyst of surface-coated matcoveredn disclosed by the invention, and the suffered inhibition of its catalytic efficiency is less.Simultaneously, when containing rare earth metal, transition metal and alkaline-earth metal in this protective layer, when keeping the greater catalytic performance, it is more favourable to improve its service life to tai-gas clean-up catalyst.
Claims (9)
1. a tai-gas clean-up catalyst comprises catalyst precarsor and protective layer, and described catalyst precarsor comprises porous matrix and the catalytic active layer that is positioned on the porous matrix, and described protective layer is positioned on the catalytic active layer;
Contain in palladium, platinum or the rhodium one or more in the described catalytic active layer;
Described protective layer contains aluminium oxide;
Described protective layer porosity is 0.05-0.3ml/g, and thickness is 3-25um, is benchmark with the volume of porous matrix, and described protective layer weight is 10-100g/l.
2. tai-gas clean-up catalyst according to claim 1, wherein, described protective layer also contains one or more in rare-earth oxide, transition metal oxide or the alkaline earth oxide.
3. tai-gas clean-up catalyst according to claim 2, wherein, described rare earth metal is lanthanum and/or cerium; Transition metal is iron and/or zirconium; Alkaline-earth metal is one or more in magnesium, barium, calcium or the strontium.
4. the preparation method of tai-gas clean-up catalyst as claimed in claim 1 comprises:
A, the preparation of employing coprecipitation contain the powder precipitation of aluminium, will make salic powder A behind powder precipitation roasting, the ball milling, and the average grain diameter of powder A is 1-20um;
B, powder A, binding agent, raising agent and deionized water are mixed, layer slurry that be protected is benchmark with protective layer slurry gross weight, described powder A content is 10-40wt%, binder content is 5-20wt%, and raising agent content is 0.2-5wt%, and surplus is a deionized water;
C, get the described catalyst precarsor that contains porous matrix and catalytic active layer, the protective layer slurry that coating step b makes on the catalytic active layer that loads on the porous matrix obtains the described tai-gas clean-up catalyst that contains matcoveredn through roasting.
5. method according to claim 4, wherein, step a comprises:
1), the soluble-salt of one or more and aluminium in the soluble-salt of the soluble-salt of rare earth metal or transition metal is dissolved in deionized water, obtains solution B;
2), ammoniacal liquor and/or ammonium carbonate are dissolved in the deionized water, forming the pH value is the solution C of 8-11;
3), under stirring condition, solution B is joined in the solution C;
4), through ageing, filtering-depositing, washing, drying, roasting, ball milling, obtain powder A.
6. method according to claim 5, wherein, aluminum ions concentration is 1-5mol/l in the solution B, and the concentration of rare earth ion is 0-2mol/l, and the concentration of transition metal ions is 0-2mol/l.
7. method according to claim 4, wherein, after described step a, comprise that also the powder A that will make among the step a floods before the step b in the soluble-salt solution of alkaline-earth metal, drying, roasting, ball milling to average grain diameter are that 1-20um obtains modified powder A.
8. method according to claim 7, wherein, alkaline-earth metal ions concentration is 1-3mol/l in the soluble-salt solution of described alkaline-earth metal.
9. method according to claim 4, wherein, described binding agent is aluminium colloidal sol or zirconium colloidal sol; Raising agent is one or more in polyethylene glycol, polyvinyl alcohol, urea, methylol methylcellulose, HEMC or the hydroxypropyl methylcellulose.
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