CN1935361A - Exhaust-gas purifying catalyst and its producing method therefor - Google Patents
Exhaust-gas purifying catalyst and its producing method therefor Download PDFInfo
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- CN1935361A CN1935361A CN 200510109962 CN200510109962A CN1935361A CN 1935361 A CN1935361 A CN 1935361A CN 200510109962 CN200510109962 CN 200510109962 CN 200510109962 A CN200510109962 A CN 200510109962A CN 1935361 A CN1935361 A CN 1935361A
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Abstract
The present invention discloses a waste-gas cleaning catalyst. It includes carrier and catalyst active component. Said catalyst active component includes at least one kind of noble metal loaded by said carrier. Said carrier includes stable zirconium oxide, said stable zirconium oxide contains at least one kind of stable element selected from rare earth element and alkaline earth element.
Description
Invention field
The present invention relates to a kind of exhaust gas purifying catalyst and manufacture method thereof, relate in particular to a kind of exhaust gas purifying catalyst and manufacture method thereof of using stable zirconia as carrier or loaded article.
Background technology
In recent years, stricter to the regulations of automobile exhaust gas, thus need further hydrocarbon (HC), carbon monoxide (CO) and the nitrogen oxide (NO that reduces in the waste gas
x) amount.
Up to the present, wherein noble metal (catalyst activity composition) is widely used as the catalyst that purifies automobile exhaust gas as the supported catalyst that rhodium is loaded on the porous carrier.This supported catalyst is called the three-dimensional catalyst, because their CO and HC and reductive NOs in can simultaneous oxidation waste gas
x
In the prior art, gama-alumina is as carrier.Yet when at high temperature using for a long time, gama-alumina can undergo phase transition becomes Alpha-alumina, so the specific area of gama-alumina descends.In addition, rhodium can advance in the aluminium oxide in solid solution when at high temperature using, so catalyst performance decline (referring to Japanese Patent Application Publication (KOKAI) 2001-347167).
In this case, need the higher carrier material of heat endurance, to replace aluminium oxide.For example disclose among Japanese patent application (KOKAI) 2000-15101 rhodium has been loaded on on the stable Zirconia carrier of alkaline-earth metal.In addition, Japanese patent application (KOKAI) 2002-518171 discloses a kind of catalyst, and wherein rhodium loads on on the stable Zirconia carrier of rare earth element.
Stable Zirconia carrier has higher heat endurance really.Yet; the inventor finds; the catalytic performance that noble metal loads on the stabilizing zirconia supported catalyst seriously descends; although they have initial performance preferably; this is because under the environmental fluctuating when high temperature uses (alternately fluctuation between poor (oxidation) environment and richness (reduction) environment), surperficial noble metal granule can aggegation or growth.
Summary of the invention
Therefore, the purpose of this invention is to provide a kind of catalyst that is used for the stabilizing zirconia load of purifying exhaust air, waste gas can suppress the reduction of catalyst performance when using under hot environment, and a kind of method for preparing this catalyst also is provided.
First aspect present invention provides a kind of exhaust gas purifying catalyst, it comprises carrier and catalyst activity composition, this catalyst activity composition comprises the noble metal of at least a portion load of at least a this carrier of usefulness, this carrier comprises stable zirconia, this stable zirconia contains at least a stable element that is selected from rare earth element and alkali earth metal, wherein 20～80wt.% of this active component total amount loads in this carrier with the form that forms solid solution with this stable zirconia, and 80～20wt.% of this active component total amount loads on the surface of at least a portion of this carrier.
In one embodiment of the invention, this carrier can contain second kind of stable zirconia, and this second kind of stable zirconia contains at least a stable element that is selected from rare earth element and alkali earth metal and the catalyst activity composition that does not contain solid solution.Can load or this catalyst activity composition of not load on its surface of this second kind of stable zirconia.
In addition, in one embodiment of the invention, except second kind of stable zirconia or replace second kind of stable zirconia, this carrier can contain at least a non-oxide zirconium carrier that is selected from aluminium oxide, cerium oxide, silica, titanium oxide, zeolite and composition thereof.This non-oxide zirconium carrier can any catalyst activity composition of not load, or in its surface can the supported catalyst active component.
Second aspect present invention provides a kind of method of making exhaust gas purifying catalyst, this method comprises the active component of supported catalyst, this catalyst activity composition comprises at least a noble metal on carrier, this carrier comprises stable zirconia, this stable zirconia contains at least a stable element that is selected from rare earth element and alkali earth metal, 20～80wt.% solid solution of this active component total amount is advanced in this carrier, and 80～20wt.% of this active component total amount is loaded on the surface of this carrier at least a portion.
Description of drawings
Fig. 1 shows the SEM photo of aging back embodiment 1 catalyst, will describe in detail below; And
Fig. 2 shows the SEM photo of aging back comparative example 1 catalyst, will describe in detail below.
The specific embodiment
The exhaust gas purifying catalyst of one aspect of the present invention comprises at least a noble metal, and it is the activity of such catalysts composition and loads on the carrier that this carrier comprises stable Zirconium oxide powder (particle), and the noble metal solid solution of specified quantitative is advanced in this stable zirconia.
Stablize this stable zirconia by containing at least a stable element that is selected from rare earth element and alkali earth metal.
Example as the rare earth element of stable element comprises scandium (Sc), yttrium (Y) and lanthanide series.Preferably yttrium (Y), lanthanum (La), cerium (Ce), neodymium (Nd) and praseodymium (Pr).Lanthanum is particularly preferred.Example as the alkaline earth element of stable element comprises calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra).Barium is preferred.These stable elements can use or mix use separately.
The amount that preferably stable zirconia contains stable element is counted 0.1～20 atom by 100 zirconium atoms in the zirconia.If the amount of stable element is less than 0.1 atom %, so to zirconic stabilization deficiency.On the other hand, if the amount of stable element surpasses 20 atom %, be settled out out-phase (foreign phase) so in zirconia, this can reduce catalyst performance.With the stable crystal of zirconium oxide structure of stable element is cubic crystal or tetragonal crystal.Its specific area of preferably stable zirconia particles is 30m
2/ g～100m
2/ g.
Stable zirconia can be by any method preparation as known in the art.For example, Zirconium oxide powder is added in the aqueous solution of the stable element that contains the water soluble salt form, fully stirs the mixture then.Be evaporated to the dispersion that obtains dried.Dry material is preferably 50～200 ℃ of following heat treated 1～48 hour, then under 400～1000 ℃, preferably under 650～1000 ℃, cured 1～12 hour, preferred 2～4 hours, to prepare stable zirconia.The example of the water soluble salt of stable element comprises for example inorganic acid salt, as sulfate, nitrate, hydrochloride and phosphate, and acylate, as acetate and oxalates.Wherein, nitrate is preferred.It is basic identical with the ratio as the Zirconium oxide powder of raw material that operable stabilizing zirconia contains the ratio of stable element and stable element water soluble salt.
Exhaust gas purifying catalyst of the present invention comprises at least a noble metal (catalyst activity composition) that loads on the carrier.20～80wt.% of the noble metal total amount that this is carrier loaded loads in this carrier with the form that becomes solid solution with this stable zirconia, and all the other 80～20wt.% load on the surface of this carrier at least a portion.
If the amount of noble metal that becomes solid solution with zirconia is less than 20wt.%, the durability of catalyst descends so.On the other hand, if load on noble metal amount on this carrier surface, can not fully cause initial catalyst activity so less than 20wt.%.The noble metal amount that becomes solid solution with stable zirconia is preferably 30～70wt.% of noble metal total load amount, and (therefore, the noble metal amount that loads on this carrier surface is preferably 70～30wt.%) of noble metal total load amount.Active component noble metal total load amount (solid solution+noble metal of area load) is generally 0.01～5wt.% of catalyst total amount (carrier+noble metal), preferred 0.1～1wt.%.
The alloy, and the alloy of palladium and platinum that comprise rhodium, palladium, rhodium and platinum as the example of the noble metal of catalyst activity composition.Wherein rhodium is preferred.
In first embodiment of the invention, carrier only is made of the stabilizing zirconia particle, and itself and noble metal form solid solution.In this case, the surface that on solid solution has the surface of stabilizing zirconia particle of noble metal, has carried noble metal.
In second embodiment, except solid solution had the stabilizing zirconia particle of noble metal, this carrier can contain second kind of zirconia particles.Second kind of stable zirconia has the stabilizing zirconia of noble metal identical with solid solution, do not contain the noble metal of any solid solution except second kind of stable zirconia.In second embodiment, solid solution has can load on its surface of stabilizing zirconia particle of noble metal or carried noble metal not.
In the 3rd embodiment, except solid solution had the stabilizing zirconia particle of noble metal, this carrier can contain non-oxide zirconium (carrier) particle.This non-oxide zirconium carrier does not contain the noble metal of any solid solution.Can load on the surface of this non-oxide zirconium carrier granular or carried noble metal not.This non-oxide zirconium carrier is selected from aluminium oxide, cerium oxide, silica, titanium oxide, zeolite and composition thereof.
Therefore, in exhaust gas purifying catalyst of the present invention, carrier always contains the stabilizing zirconia particle that solid solution has noble metal, but the carrier of carried noble metal can only have the stabilizing zirconia particle of noble metal to constitute by solid solution from the teeth outwards, there are the stabilizing zirconia of noble metal and second kind of stable zirconia and/or non-oxide zirconium particle to constitute by solid solution, or constitute (solid solution have can load on its surface of stabilizing zirconia of noble metal or carried noble metal not) in this case, by second kind of stable zirconia and/or non-oxide pick particle.In addition, in the present invention, carrier can contain the not second kind of stable zirconia and/or the non-oxide zirconium particle of carried noble metal.Under any circumstance, active component is by carrier loaded, make 20～80wt.% of active component total amount load in this carrier with the form that becomes solid solution with this stable zirconia, and all the other 80～20wt.% loads on this carrier surface.
The method that the present invention makes exhaust gas purifying catalyst comprised for two steps, i.e. solid solution treatment and area load.
In solid solution treatment, 20～80wt.% solid solution of the noble metal total amount of load is in stable zirconia.Particularly, for example using, ultrasonic wave is well dispersed in stable Zirconium oxide powder in the water, the dispersion that obtains is added in the aqueous solution of noble metal of the water soluble salt form that contains aequum,, filters then and dry with absorption or carried noble metal salt on carrier surface.Used whole noble metals can load on the carrier.Be enough to that noble metal is formed under the temperature and time of solid solution in stable Zirconium oxide powder, the dried powder that obtains at air baking.The stoving temperature that forms solid solution is preferably 600～1000 ℃, more preferably 700～900 ℃.The time of curing changes with stoving temperature, but common 2～4 hours.The example of water-soluble precious metal salt comprises for example inorganic acid salt, as sulfate, nitrate, hydrochloride and phosphate.Wherein, nitrate is preferred.In solid solution treatment, the about 60～100wt.% noble metal that loads on during beginning on the stable zirconium surface forms solid solution.
In the area load step, 80～20wt.% of the noble metal total amount of load loads on the carrier surface.Particularly, with reference to described in the solid solution treatment, precious metal salt is adsorbed and loads on the support powder surface (only is the stabilized zirconia powders that solid solution has noble metal, or solid solution has the stabilized zirconia powders of noble metal and the mixture at second kind of stable zirconia and/or non-oxide zirconium powder end, or second kind of stable zirconia and/or non-oxide zirconium powder end), filter then and drying composite.Used whole noble metals load on the carrier surface.Surperficial noble metal is gone up substantially do not form solid solution but with the fully bonding temperature and time condition of carrier surface under, the powder that obtains at air baking.Stoving temperature is preferably 100～400 ℃, more preferably 200～300 ℃.The time of curing changes with stoving temperature, but common 1～3 hour.In the area load step, all surface precious metal salt that is used as raw material can both load on the carrier surface with oxide form.Should be noted that, also can have the stabilized zirconia powders of noble metal on noble metal and its surface and mix, prepare exhaust gas purifying catalyst of the present invention by simply solid solution being had with the second kind of zirconia and/or the non-oxide zirconium powder end of any noble metal of load not.In addition, also can there be second kind of zirconia of noble metal and/or non-oxide zirconium powder end to mix with surperficial upward load, prepare exhaust gas purifying catalyst of the present invention by simply solid solution there being the stabilized zirconia powders that does not have noble metal on noble metal and its surface.
The catalyst that obtains like this can use after making bead.Selectively, catalyst can be coated in (for example, cordierite honeycomb carrier) on the honeycomb support by wash coat method (wash coat method).
Use the ICP emission spectrum can analyze the noble metal amount that is solid-solubilized in the stable zirconia.Particularly, catalyst is immersed in the lytic agent, the insoluble metal oxide containing precious metals particle of separating on the carrier surface of lytic agent, but dissolving constitutes the stable zirconia (noble metal that contains solid solution) of carrier, fully stirs the mixture with the zirconia of steady dissolution.Noble metal in the solution that use ICP emission spectrographic analysis obtains.Volume ratio is that 1/15 the hydrofluoric acid and the solution of water can be used as lytic agent, and dissolving operation at room temperature (20～30 ℃) was carried out 12 hours.
Catalyst of the present invention circulates repeatedly, (wherein air/fuel is smaller in rich, high temperature (reduction) environment, be that fuel concentration is higher), the noble metal loading that is solid-solubilized in the stable zirconia becomes fine grained (a few dust to 10 dusts of particle diameter) on carrier surface, (wherein air/fuel is bigger in high temperature poor (oxidation) environment, be that fuel concentration is lower), the noble metal of deposition once more solid solution in stable zirconia.Therefore, the growth of noble metal granule is suppressed in the catalyst of the present invention, keeps its high catalyst performance, even also not too big reduction of catalyst performance under the environmental fluctuating of high temperature.On the other hand, the noble metal in being solid-solubilized in stable zirconia is not in advance brought into play the commitment of catalyst action, and the noble metal of load just shows catalyst activity on carrier surface in advance.Therefore, catalyst of the present invention can and fully show catalytic activity in a long time from beginning.In addition, the noble metal of load is the part of total noble metal on carrier surface in advance, and high degree of dispersion is on carrier surface.Therefore, even surperficial noble metal a small amount of, also can show sufficient initial catalytic activity, and because the decentralization on carrier surface is higher, so sintering is suppressed.
Below in conjunction with embodiment the present invention is described, but the invention is not restricted to this.
Embodiment 1
In this embodiment, to contain the total amount that is supported by stable zirconia be the rhodium of 0.5wt.% to the catalyst of preparation.
(A) be 90m with the 50g specific area
2The commercial available Zirconium oxide powder of/g is added to 100mL and contains in the aqueous solution of lanthanum nitrate, and it is 8/100 that its amount makes the La/Zr atomic ratio, stirs mixture to be evaporated to dried at 90 ℃ down.The mixture that obtains descends further dry 12 hours at 120 ℃, and cures under 800 ℃ 2 hours, obtains the stable Zirconia carrier of lanthanum (powder).X-ray diffraction the analysis showed that its crystalline texture of stable zirconia that obtains is cubic lattice.The specific area of stable Zirconia carrier is 70m
2/ g.
(B) Zirconium oxide powder ultrasonic agitation in the 50mL ion exchange water that 50g is stable, and disperse.Add the aqueous solution contain rhodium at once in the dispersion that obtains, wherein rhodium content accounts for 1/2 of the rhodium total amount for the treatment of load, with absorption and load rhodium nitrate on stable zirconia load powder surface, and the suction filtration mixture.Use the rhodium in the ICP emission spectrographic analysis filtrate, do not detect rhodium.Therefore, the load factor of rhodium is 100%.
The stable Zirconium oxide powder of rhodium load descended dry 12 hours at 110 ℃, cured under 800 ℃ 3 hours in air then, so that the rhodium solid solution is advanced in the stable zirconia.Wherein solid solution has the stable zirconic part of rhodium at room temperature to be immersed in the solution that volume ratio is 1/15 hydrofluoric acid and water 12 hours, with the dissolved oxygen zirconium.ICP emission spectrum to gained solution shows that the zirconia solid solution that loads on the stable lip-deep 89wt.% of Zirconia carrier is in stabilizing zirconia.
(C) the stable Zirconium oxide powder that 50g solid solution that will obtain above has rhodium ultrasonic agitation and disperseing 10 minutes in the 50mL ion exchange water.Add the aqueous solution contain rhodium at once in the dispersion that obtains, wherein rhodium content accounts for 1/2 of the rhodium total amount for the treatment of load, with absorption and load rhodium nitrate on stable Zirconia carrier powder surface, suction filtration mixture.The stabilized zirconia powders of the rhodium load that obtains was thus descended dry 12 hours at 110 ℃, cured under 250 ℃ 2 hours in air then, so that rhodium loads on the carrier surface.
(D) compress the catalyst fines that obtains thus, pulverize, and make the bead that diameter is 0.5～1.0mm.
Undertaken by the step identical with embodiment 1, except in embodiment 1 (B) step, using the aqueous solution that contains the boric acid rhodium, wherein the rhodium amount accounts for 1/4 of the rhodium total amount for the treatment of load, in embodiment 1 (C), use the aqueous solution that contains rhodium nitrate, wherein the rhodium amount accounts for 3/4 of the rhodium total amount for the treatment of load, makes required catalyst thus.In the catalyst that obtains, the 25wt.% of rhodium total amount forms solid solution in stable zirconia, and all the other 75wt.% load on the stable Zirconia carrier surface.
Embodiment 3
Undertaken by the process identical with embodiment 1, except in embodiment 1 (B) step, using the aqueous solution that contains the boric acid rhodium, wherein the rhodium amount accounts for 2/3 of the rhodium total amount for the treatment of load, in embodiment 1 (C) step, use the aqueous solution that contains rhodium nitrate, wherein rhodium content accounts for 1/3 of the rhodium total amount for the treatment of load, makes required catalyst thus.In the catalyst that obtains, the 64wt.% of rhodium total amount forms solid solution in stable zirconia, and all the other 36wt.% load on the stable Zirconia carrier surface.
Embodiment 4
In this embodiment, to contain by the total amount of stable zirconia load be the noble metal (rhodium: 0.4% of 0.5wt.% to the catalyst of preparation; Platinum 0.1%).By with embodiment 1 (A) and (B) identical step carry out.Having the stable Zirconium oxide powder of rhodium to be added to the solid solution that obtains thus contains in the aqueous solution of rhodium nitrate and dinitric acid diamines platinate, wherein rhodium content accounts for 1/2 of the rhodium total amount for the treatment of load, with absorption and load rhodium nitrate and dinitric acid diamines platinate on zirconium surface.The powder that obtains descended dry 12 hours at 110 ℃, cured under 250 ℃ 1 hour in air, handled according to embodiment 1 (D) then, with the preparation pellet catalyst.
Embodiment 5
Undertaken by the process identical, replace rhodium nitrate except using palladium nitrate, thereby make pellet catalyst with embodiment 1.
Comparative example 1
The Zirconium oxide powder 50g that the lanthanum that obtains among the embodiment 1 (A) is stable, ultrasonic agitation is 10 minutes in the 50mL ion exchange water, with a minute divided powder.Add the aqueous solution of rhodium nitrate at once in the dispersion that obtains, wherein rhodium content is equivalent to treat the rhodium total amount of load, with absorption and load rhodium nitrate on stable zirconium surface, suction filtration mixture.The stable Zirconium oxide powder of the rhodium load that obtains descended dry 12 hours at 110 ℃, cured under 250 ℃ 2 hours in air then, so that rhodium loads on the carrier surface, the powder that obtains was made bead.
Comparative example 2
Undertaken by the process identical, except not carrying out solid solution treatment, thereby make pellet catalyst with embodiment 5.
The initial catalytic activity of the every kind of catalyst that in embodiment 1～5 and comparative example 1～2, obtains and aging after activity rating as follows.
＜catalytically active assessment 〉
Catalyst sample is placed in the atmospheric fixed bed circulation reaction unit.With 12 ℃/minute the rates of heat addition catalyst sample is heated to 500 ℃ from 100 ℃, the model gas that makes stoichiometry simultaneously is by fixed bed, continuous measurement NO therebetween
xPurification rate.To remove 50%NO
xThe time thermograph make the purification rate index.
(I) initial catalytic activity
The part of the every kind of catalyst that obtains in embodiment 1～5 and comparative example 1～2 is used as the sample of catalytically active assessment, and carries out above-mentioned catalytically active assessment test.
(II) aging back catalytic activity
The part of the every kind of catalyst that obtains in embodiment 1～5 and comparative example 1～2 is placed on the catalyst bed of circulation type aging equipment.Then, the model that will be made up of the nitrogen that contains 5 volume % oxygen model rich gas stingy and that is made up of the nitrogen that contains 10 volume % carbon monoxide is alternately by catalyst bed, and every kind flows through 5 minutes with flow velocity 1000mL/min, passes through 30 hours continuously altogether.Subsequently, take out catalyst, carry out the test of above-mentioned evaluation catalytic activity.Fig. 1 and Fig. 2 show the SEM photo at the catalyst of above-mentioned aging back embodiment 1 and comparative example 1 respectively.As can be seen from the figure, in the catalyst of embodiment 1, deposit to the about 1nm of rhodium particle on the carrier surface in the carrier, and in the catalyst of comparative example 1, it is tens microns that the rhodium particle is given birth to particle size.
Test result shows in table 1.Table 1 also shows the ratio of the noble metal of the amount of noble metal of load and solid solution.
Table 1
| Example | Total noble metal (wt.%) of load | The ratio of the noble metal of solid solution (wt.%) | Temperature when NOx 50% purifies | |||||
| Rh | Pt | Pd | Rh | Pt | Pd | Initially | After aging | |
| Embodiment 1 | 0.5 | 0 | 0 | 44.5 | 0 | 0 | 272 | 277 |
| |
0.5 | 0 | 0 | 25.0 | 0 | 0 | 269 | 286 |
| Embodiment 3 | 0.5 | 0 | 0 | 64.0 | 0 | 0 | 277 | 275 |
| Embodiment 4 | 0.4 | 0.1 | 0 | 45.0 | 0 | 0 | 270 | 280 |
| Embodiment 5 | 0 | 0 | 0.5 | 0 | 0 | 35.0 | 295 | 330 |
| Comparative example 1 | 0.5 | 0 | 0 | 0 | 0 | 0 | 268 | 298 |
| Comparative example 2 | 0 | 0 | 0.5 | 0 | 0 | 0 | 290 | 350 |
As can be seen from Table 1, exhaust gas purifying catalyst of the present invention is compared with initial value after aging and is not almost improved NO
x50% temperature when purifying, and the exhaust gas purifying catalyst of comparative example 1～2 is compared with initial value after aging and has been improved NO largely
xTemperature during 50% purification.These results show, even the at high temperature long-time back catalytic performance that uses of exhaust gas purifying catalyst of the present invention does not descend largely yet, just show enough catalytic activitys simultaneously when using beginning.
Embodiment 6
In this embodiment, to contain the total amount by stable zirconia load be the rhodium of 0.5wt.% to the catalyst of preparation.
By with embodiment 1 (A) and (B) identical step prepare the stable Zirconium oxide powder that solid solution has rhodium.
On the other hand, will be by the 50g lanthanum that identical step among the embodiment 1 (A) obtains stable Zirconium oxide powder ultrasonic agitation and dispersion in the 50mL ion exchange water.Add the aqueous solution contain rhodium at once in the dispersion that obtains, wherein rhodium content accounts for 1/2 of the rhodium total amount for the treatment of load, with absorption and load rhodium nitrate on stable Zirconia carrier powder surface, suction filtration mixture.The stable Zirconium oxide powder of the rhodium of load from the teeth outwards that obtains descended dry 12 hours at 110 ℃, cured under 250 ℃ 1 hour in air then, thereby obtained the support powder of load rhodium from the teeth outwards.
Then, the above-mentioned solid solution of 50g there is the stable Zirconia carrier powder of rhodium and the 50g above-mentioned support powder physical mixed of load rhodium from the teeth outwards, the catalyst fines that mixes with preparation.The catalyst fines that compression obtains is thus pulverized, and is made the bead that diameter is 0.5～1.0mm.
Embodiment 7
In this embodiment, being prepared as follows the total amount that contains by stable zirconia load is the catalyst of the rhodium of 0.5wt.%.
Prepare stable Zirconia carrier powder by the step identical with embodiment 1 (A)-(C), the rhodium solid solution is in wherein forming solid solution, and load in its surface.With this support powder of 50g and 50g stable Zirconia carrier powder (rhodium that does not have load) physical mixed by embodiment 1 (A) preparation.The mixed catalyst powder that compression obtains is thus pulverized, and is made the bead that diameter is 0.5～1.0mm.
Estimate the catalytic activity of the pellet catalyst that obtains among the embodiment 6 and 7 by above-mentioned steps.The results are shown in the following table 2.
Table 2
| Example | Total noble metal (wt.%) of load | The ratio of the noble metal of solid solution (wt.%) | Temperature when NOx 50% purifies | |||||
| Rh | Pt | Pd | Rh | Pt | Pd | Initially | After aging | |
| Embodiment 6 | 0.5 | 0 | 0 | 44.5 | 0 | 0 | 270 | 278 |
| Embodiment 7 | 0.5 | 0 | 0 | 45.0 | 0 | 0 | 275 | 285 |
As can be seen from Table 2, exhaust gas purifying catalyst of the present invention is compared with initial value after aging and is not almost improved NO
xTemperature during 50% purification.Even be that the at high temperature long-time back catalytic performance that uses of exhaust gas purifying catalyst of the present invention does not descend largely yet, when using beginning, just show enough catalytic activitys simultaneously.
Embodiment 8
In this embodiment, be prepared as follows that to contain by stabilizing zirconia load total amount be the catalyst of the rhodium of 0.5wt.%.
Prepare stable Zirconia carrier powder by the step identical with embodiment 1 (A)-(C), rhodium is in wherein forming solid solution, and the rhodium load in its surface.With this support powder of 50g and 50g alumina powder and 50g ceria oxide powder physical mixed,, obtain slurry to wherein adding ion exchange water and adhesive (alumina sol).By the wash coat method slurry is applied the (catalytic amount of coating: 7g) (diameter 30mm on cordierite monolithic honeycomb support; Length 50mm), and dry, make required monolith catalyst.
Embodiment 9
In this embodiment, being prepared as follows the total amount that contains by the stabilizing zirconia load is the catalyst of the rhodium of 0.5wt.%.
Prepare stable Zirconia carrier powder by the step identical with embodiment 1 (A)-(B), rhodium is in wherein forming solid solution.With this support powder of 50g and 50g alumina powder and 50g ceria oxide powder physical mixed,, obtain slurry to wherein adding ion exchange water and adhesive (alumina sol).Add rhodium nitrate aqueous solution in the slurry that obtains, wherein rhodium content accounts for 1/2 of the rhodium total amount for the treatment of load, with absorption and load rhodium on the support powder surface.By the wash coat method slurry that obtains is applied (the catalytic amount of coating: 7g) (diameter 30mm on cordierite monolithic honeycomb support; Length 50mm), and dry, make required monolith catalyst.
Embodiment 10
In this embodiment, being prepared as follows the total amount that contains by the stabilizing zirconia load is the catalyst of the rhodium of 0.5wt.%.
Prepare stable Zirconia carrier powder by the step identical with embodiment 1 (A)-(B), rhodium is in wherein forming solid solution.With this support powder of 50g and 50g alumina powder and 50g ceria oxide powder physical mixed,, obtain slurry to wherein adding ion exchange water and adhesive (alumina sol).By the wash coat method slurry is applied the (catalytic amount of coating: 7g) (diameter 30mm on cordierite monolithic honeycomb support; Length 50mm).Apply the rhodium nitrate aqueous solution contain rhodium on the wash coat that obtains, wherein rhodium content accounts for 1/2 of the rhodium total amount for the treatment of load, 110 ℃ dry 12 hours down, in air, under 250 ℃, cured 1 hour then, make required monolith catalyst.
Estimate the catalytic activity of the catalyst that obtains among the embodiment 8-10 by above-mentioned steps.The results are shown in the following table 3.
Table 3
| Example | Total noble metal (wt.%) of load | The ratio of the noble metal of solid solution (wt.%) | Temperature when NOx 50% purifies | |||||
| Rh | Pt | Pd | Rh | Pt | Pd | Initially | After aging | |
| Embodiment 8 | 0.5 | 0 | 0 | 44.5 | 0 | 0 | 256 | 263 |
| Embodiment 9 | 0.5 | 0 | 0 | 45.0 | 0 | 0 | 257 | 265 |
| Embodiment 10 | 0.5 | 0 | 0 | 45.0 | 0 | 0 | 254 | 266 |
As can be seen from Table 3, exhaust gas purifying catalyst of the present invention is compared with initial value after aging and is not almost improved NO
xTemperature during 50% purification.Even be that the at high temperature long-time back catalytic performance that uses of exhaust gas purifying catalyst of the present invention does not descend largely yet, when using beginning, just show enough catalytic activitys simultaneously.
Claims (11)
1. exhaust gas purifying catalyst, it is characterized in that, comprise carrier and catalyst activity composition, this catalyst activity composition comprises the noble metal of at least a portion load of at least a this carrier of usefulness, this carrier comprises stable zirconia, this stable zirconia contains at least a stable element that is selected from rare earth element and alkali earth metal, wherein 20～80wt.% of this active component total amount loads in this carrier with the form that forms solid solution with this stable zirconia, and 80～20wt.% of this active component total amount loads on the surface of at least a portion of this carrier.
2. catalyst as claimed in claim 1 is characterized in that, the alloy of noble metal selected from rhodium, palladium, rhodium and platinum, and the alloy of palladium and platinum.
3. catalyst as claimed in claim 1 or 2 is characterized in that, the amount that this stable zirconia contains stable element is counted 0.1～20 atom % by zirconium contained in the stable zirconia.
4. as each described catalyst in the claim 1 to 3, it is characterized in that, this carrier also contains second kind of stable zirconia, and this second kind of stable zirconia contains at least a stable element that is selected from rare earth element and alkali earth metal and the active component that does not contain solid solution.
5. catalyst as claimed in claim 4 is characterized in that, this second kind of zirconia be the supported active composition not.
6. catalyst as claimed in claim 4 is characterized in that, the supported active composition is gone up on its surface of this second kind of zirconia.
7. as each described catalyst in the claim 1 to 6, it is characterized in that this carrier contains at least a non-oxide zirconium carrier that is selected from aluminium oxide, cerium oxide, silica, titanium oxide, zeolite and composition thereof.
8. catalyst as claimed in claim 7 is characterized in that, this non-oxide zirconium carrier is the supported active composition not.
9. catalyst as claimed in claim 7 is characterized in that, the supported active composition is gone up on its surface of this non-oxide zirconium carrier.
10. method of making exhaust gas purifying catalyst, it is characterized in that, this method comprises the supported catalyst active component, this catalyst activity composition comprises at least a noble metal on carrier, this carrier comprises stable zirconia, this stable zirconia contains at least a stable element that is selected from rare earth element and alkali earth metal, 20～80wt.% solid solution of this active component total amount is advanced in this carrier, and 80～20wt.% of this active component total amount is loaded on the surface of this carrier at least a portion.
11. method as claimed in claim 10 is characterized in that, realizes solid solution under 600～1000 ℃ temperature.
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| CN 200510109962 CN1935361A (en) | 2005-09-21 | 2005-09-21 | Exhaust-gas purifying catalyst and its producing method therefor |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108602049A (en) * | 2016-01-28 | 2018-09-28 | 株式会社科特拉 | The Zr system complex oxides of loading Pd |
| CN110560056A (en) * | 2019-08-30 | 2019-12-13 | 无锡威孚环保催化剂有限公司 | Universal small gasoline engine tail gas catalyst and preparation method thereof |
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2005
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108602049A (en) * | 2016-01-28 | 2018-09-28 | 株式会社科特拉 | The Zr system complex oxides of loading Pd |
| CN108602049B (en) * | 2016-01-28 | 2021-09-03 | 株式会社科特拉 | Pd-supporting Zr-based composite oxide |
| CN110560056A (en) * | 2019-08-30 | 2019-12-13 | 无锡威孚环保催化剂有限公司 | Universal small gasoline engine tail gas catalyst and preparation method thereof |
| CN110560056B (en) * | 2019-08-30 | 2022-11-01 | 无锡威孚环保催化剂有限公司 | Universal small gasoline engine tail gas catalyst and preparation method thereof |
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