CN109590016A - Use for diesel engine catalyst and preparation method based on modified hydrotalcite Derived Oxides - Google Patents

Use for diesel engine catalyst and preparation method based on modified hydrotalcite Derived Oxides Download PDF

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CN109590016A
CN109590016A CN201811651005.5A CN201811651005A CN109590016A CN 109590016 A CN109590016 A CN 109590016A CN 201811651005 A CN201811651005 A CN 201811651005A CN 109590016 A CN109590016 A CN 109590016A
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catalyst
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mass percent
molecular sieve
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CN109590016B (en
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吕刚
朱越
宋崇林
李亚松
张荣鑫
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Tianjin University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
    • B01J29/46—Iron group metals or copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
    • B01J20/041—Oxides or hydroxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines

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Abstract

The invention discloses a kind of use for diesel engine catalyst based on modified hydrotalcite Derived Oxides, use bimetallic-modified ZSM-5 molecular sieve and noble metal for major catalyst；BaO is adsorbent；CeO2‑ZrO2For co-catalyst；Bimetallic-modified hydrotalcite Derived Oxides and γ-Al2O3For coating basic material；Cordierite honeycomb ceramic is carrier.Preparation process includes: the determination of raw material dosage；Modified ZSM-5 type molecular sieve, the preparation of modified hydrotalcite Derived Mixed Oxides and the preparation of coating paste and coating.By diesel engine dilute/fuel-rich Operation mode cycle variation, catalyst can in efficient catalytic exhaust NOx absorption-reduction reaction.Modified molecules screen sections substitute the noble metal in LNT catalyst, reduce cost of material, improve sulfur resistive, heat resistance；Modified hydrotalcite Derived Oxides substitute the γ-Al in LNT catalyst2O3, improve the NOx adsorption capacity of catalyst.

Description

Use for diesel engine catalyst and preparation method based on modified hydrotalcite Derived Oxides
Technical field
The invention belongs to exhaust gas from diesel vehicle pollutant purification technologies, and in particular to one kind is for nitrogen oxidation in exhaust gas from diesel vehicle Object (Nitrogen Oxides-NOx) pollutant absorption-reduction purification catalyst and preparation method thereof.
Background technique
NOx is a kind of biggish atmosphere pollution of harm, not only has direct toxic action to organism, but also still result in One of major incentives of Disaster Events such as photochemical fog, acid rain, greenhouse effects.As China's motor vehicle yield and ownership are fast Surge length, and the NOx emission contribution rate of traffic transport industry improves year by year, especially in urban area, in recent years, comes from motor vehicle The NOx emission contribution rate of tail gas is more than 50%.And in a motor vehicle, the NOx discharge of diesel vehicle will be to higher, 2017, Having 70% NOx in motor vehicle NOx total release is by emission of diesel engine.For environment protection, ensure that public's body is strong Health, China have formulated the discharge of increasingly strict emission regulation limiting vehicle exhaust pollutant, the state that will especially implement VI emission regulation, wherein the emission limit for diesel vehicle NOx is extremely harsh.To meet VI emission regulation of state, a variety of diesel engines NOx emission control technology is furtherd investigate, and wherein lean-burn NOx trap (Lean NOx Trap-LNT) technology is also referred to as NOx Storage reduction (NOx Storage Reduction-NSR) technology is known as being to solve medium and small diesel vehicle NOx by industry Discharge most potential one of technical measures.
The principle of the technology are as follows: control diesel engine first operates under traditional Lean Burn Operating, at this point, special in LNT technology Under the action of the major catalyst in catalyst (abbreviation LNT catalyst), a part of nitric oxide (NO) in exhaust is catalyzed It is oxidized to nitrogen dioxide (NO2), these NO2And exhaust in remaining NO by the adsorbent in LNT catalyst with nitrate/nitrous The form of Barbiturates adsorbing species is adsorbed on catalyst surface；The close absorption of adsorbance to LNT catalyst surface institute NOx adsorption When the saturated extent of adsorption of agent, adjustment engine is run under fuel-rich operating condition, at this point, not only engine exhaust temperature increases, oxygen (O2) content is close to zero, and unburned hydrocarbon (HC), carbon monoxide (CO), hydrogen (H in exhaust2) etc. reproducibilities ingredient substantially Increase, and these reproducibility ingredients are in LNT catalyst under the action of major catalyst, the NOx that LNT catalyst surface has been adsorbed It is reduced to nitrogen (N2) etc. harmless components；And the LNT catalyst after reacting also has restored NOx adsorption capacity, that is, LNT catalysis Agent realizes regeneration.Control diesel engine reruns above-mentioned lean-burn/fuel-rich operation circulation, can be realized what Diesel NOx was discharged High-efficient purification.
LNT technology principle was proposed in the 1980s, had commercialized product supply market at present, but Since traditional LNT catalyst itself is there are some defects and deficiency, which also fails to large-scale promotion, application.Traditional LNT Catalyst is platinum (Pt)/barium monoxide (BaO)/γ-aluminum oxide (γ-Al2O3) System Catalyst, wherein precious metals pt conduct Major catalyst, in the oxidation reaction of Lean Burn Operating catalysis NO, and in the reduction reaction of fuel-rich operating condition catalytic adsorption state NOx.Although Pt is a kind of oxidation reaction catalyst of function admirable, but its reduction reaction catalytic activity is to be improved, is needed by improving Pt Dosage make up the deficiency of reduction reaction catalytic activity；But then, noble metal is with high costs, sulfur resistive and heat resistance are deposited In obvious deficiency, then cause dosage of the Pt in LNT catalyst unsuitable excessively high.BaO adsorbent is good NOx adsorbent material, NOx unit saturated extent of adsorption is very high, but due in traditional LNT catalyst BaO excessively understand the stability of deteriorated catalyst coating, Mass ratio is restricted, thus cause the saturated extent of adsorption of traditional LNT catalyst entirety limited, diesel engine lean-burn/fuel-rich work Condition switching is excessively frequent, has an adverse effect to the power and economic performance of diesel engine.And γ-Al2O3It is good coating basis Material, the mass ratio in traditional LNT catalyst catalyst coatings is generally 50% or more.But γ-Al2O3Material itself LNT catalytic activity and NOXAdsorption capacity is poor, meanwhile, γ-Al at high temperature2O3It is also easy to undergo phase transition or react with BaO life At the BaAl of spinel structure2O4, lead to NOXIt stores active sites to reduce, to be degrading purification of the LNT catalyst to NOx Energy.
In order to overcome the performance deficiency of above-mentioned traditional LNT catalyst, industry is substituted around precious metal material and novel adsorption The most important means that agent/coating basic material researches and develops the two novel LNT catalyst performance optimizations have been carried out a large amount of systems, have been goed deep into Research work.The study found that the reduction reaction catalytic activity of metal modified molecular screen catalyst is more than noble metal catalyst Reduction reaction catalytic activity, as copper (Cu)/iron (Fe) modified ZSM-5 type molecular sieve catalyst has been applied to diesel engine and has selectively urged Change in reduction (Selective Catalytic Reduction-SCR) NOx purification system.Meanwhile Cu modified ZSM-5 type point The low-temperature oxidation of sub- sieve catalyst-reduction reaction catalytic performance is good, and the high temperature of Fe modified ZSM-5 type molecular sieve type catalyst Oxidation-reduction reaction catalytic activity is higher, it is contemplated that Cu-Fe bimetallic-modified molecular sieve type catalyst can have broader Oxidation-reduction reaction catalytic performance high activity temperature window.In addition, studies have shown that a small amount of noble metal component can change with metal Property molecular sieve type catalyst acts synergistically, and significantly improves the oxidation-reduction reaction catalytic activity of catalyst entirety.Another party Face, magnesium (Mg)-aluminium (Al) carbonate form hydrotalcite Derived Mixed Oxides (molecular formula: Al2O3It is 6MgO) with higher to compare table Area, stronger alkalinity and good coating stability meet high-performance LNT catalyst coating basic material and the additional suction of NOx Attached dose of requirement.In addition, being substituted obtained from Al element and zinc (Zn) element portions substitution Mg element with lanthanum (La) element portions Modified hydrotalcite Derived Mixed Oxides material has more excellent coating characteristic and NOx absorption property.Changed with La-Zn bimetallic Property hydrotalcite Derived Mixed Oxides substitute overwhelming majority γ-Al2O3Coating basic material can dramatically increase in LNT catalyst The content of additional adsorbent, to improve the NOx absorption property of LNT catalyst entirety or reduce the dosage of BaO adsorbent.
Summary of the invention
The present invention on the basis of early-stage study, propose it is a kind of suitable for diesel vehicle, with Cu-Fe bimetallic-modified ZSM- 5 type molecular sieves substitute most of noble metal and substitute major part γ-with La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides Al2O3The use for diesel engine catalyst and preparation method based on modified hydrotalcite Derived Oxides being characterized.
In order to solve the above technical problems, the present invention proposes a kind of diesel engine based on modified hydrotalcite Derived Oxides With catalyst, including modified ZSM-5 type molecular sieve, Pt, Pd, BaO, CeO2-ZrO2The derivative composite oxygen of solid solution, modified hydrotalcite Compound, γ-Al2O3And 400 mesh cordierite honeycomb ceramics carrier；The modified ZSM-5 type molecular sieve is that Cu-Fe bimetallic changes Property type ZSM 5 molecular sieve, wherein Cu element is dispersed in type ZSM 5 molecular sieve surface and micropore in the form of CuO, Fe Element is with Fe2O3Form be dispersed in type ZSM 5 molecular sieve surface and micropore, and described CuO, Fe2O3With ZSM-5 type The mass percent of molecular sieve are as follows: 5~15%/5~10%/90~75%, the sum of mass percent is 100%；The modification Hydrotalcite Derived Mixed Oxides are La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides, the La-Zn bimetallic-modified Hydrotalcite Derived Mixed Oxides are by the part La substitution Al2O3Al in 6MgO type houghite Derived Mixed Oxides, by The part Zn substitution Al2O3Mg in 6MgO type houghite Derived Mixed Oxides and formed, wherein La, Al and Zn, Mg Four kinds of elements are respectively with La2O3、Al2O3It is derivative multiple that the La-Zn bimetallic-modified hydrotalcite is dispersed in the form of ZnO, MgO It closes in oxide, and La2O3And Al2O3Molar percentage are as follows: 50~80%/50~20%, the sum of molar percentage is 100%；The molar percentage of ZnO and MgO are as follows: 25~75%/75~25%, the sum of molar percentage is 100%；Meanwhile institute State the sum of molal quantity of La ion and Al ion and Zn ion and Mg in La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides The ratio of the sum of the molal quantity of ion is 1:3；The Cu-Fe bimetallic-modified type ZSM 5 molecular sieve is constituted with Pt and Pd urges The quality sum of the major catalyst of agent, Pt and Pd and the mass percent of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve are as follows: 2 ~5%/98~95%, the sum of mass percent is 100%；The BaO constitutes the adsorbent of catalyst；The CeO2-ZrO2 Solid solution constitutes the co-catalyst of catalyst；The La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides and γ-Al2O3 Constitute the coating basic material of catalyst；The La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides and γ-Al2O3's Mass percent are as follows: 75~90%/25~10%, the sum of mass percent is 100%；The major catalyst, is helped and is urged adsorbent Agent and coating basic material constitute the catalyst coatings of catalyst, the major catalyst, adsorbent, co-catalyst and coating base The mass percent of plinth material respectively corresponds are as follows: and 5~10%/10%/5~10%/80~70%, the sum of mass percent is 100%；Catalyst is constituted by the catalyst coatings and 400 mesh cordierite honeycomb ceramics, wherein the 400 mesh cordierite bee Nest ceramics are the carrier of catalyst, and the catalyst coatings are coated in 400 mesh cordierite honeycomb ceramics, and the catalysis applies The mass percent of layer and 400 mesh cordierite honeycomb ceramics are as follows: 10~30%/90~70%, the sum of mass percent is 100%.
Further, the present invention is based on the use for diesel engine catalyst of modified hydrotalcite Derived Oxides, wherein described help is urged In agent, CeO2With ZrO2Mass percent are as follows: 80~50%/20~50%, the sum of mass percent be 100%.
In the major catalyst, the mass percent of Pt and Pd are as follows: 25~50%/75~50%, the sum of mass percent It is 100%.
γ-Al in the coating basic material2O3It is converted by the Aluminum sol as adhesive coating.
The preparation method of the above-mentioned use for diesel engine catalyst based on modified hydrotalcite Derived Oxides, comprising the following steps:
Step 1: preparing the determination of catalyst raw material dosage:
Separately design out the quality percentage of the sum of Pt, Pd and Cu-Fe bimetallic-modified type ZSM 5 molecular sieve in major catalyst Than；In the major catalyst, the mass percent of Pt and Pd are as follows: 25~50%/75~50%, the sum of mass percent is 100%；CuO, Fe in Cu-Fe bimetallic-modified type ZSM 5 molecular sieve2O3With the mass percent of type ZSM 5 molecular sieve；It helps and urges CeO in agent2With ZrO2Mass percent are as follows: 80~50%/20~50%, the sum of mass percent be 100%；The painting γ-Al in layer basic material2O3It is converted by the Aluminum sol as adhesive coating；The bis- gold of La-Zn in coating basic material Belong to modified hydrotalcite Derived Mixed Oxides and γ-Al2O3Mass percent；La-Zn bimetallic-modified hydrotalcite derivative is compound In oxide, La2O3And Al2O3Mol percentage and ZnO and MgO mol percentage；Major catalyst, adsorbent, co-catalysis The mass percent of agent and coating basic material；The mass percent model of catalyst coatings and 400 mesh cordierite honeycomb ceramics carriers It encloses；And planned allocation coating slurry produces the quality of catalyst coatings；
Ratio according to each component in above-mentioned catalyst calculates separately out plan, and to prepare Pt, Pd, Cu-Fe in catalyst coatings bis- Metal-modified type ZSM 5 molecular sieve, BaO, CeO2、ZrO2、γ-Al2O3, the derivative combined oxidation of La-Zn bimetallic-modified hydrotalcite CuO, Fe in object and Cu-Fe bimetallic-modified type ZSM 5 molecular sieve2O3With type ZSM 5 molecular sieve, La-Zn bimetallic-modified water La in talcum Derived Mixed Oxides2O3、Al2O3, ZnO and MgO quality；
In conjunction with every 517.9g [H2PtCl6·6H2O] preparation 195.1g Pt, every 266.4g [Pd (NO3)2·2H2O] preparation 106.4g Pd, every 255.4g [Ba (CH3COO)2] preparation 153.3g BaO, every 434.1g [Ce (NO3)3·6H2O] preparation 172.1g CeO2, every 429.3g [Zr (NO3)4·5H2O] preparation 123.2g ZrO2, every 187.6g [Cu (NO3)2] preparation 79.5g CuO, every 808.0g [Fe (NO3)3·9H2O] preparation 159.7g Fe2O3, every 866.0g [La (NO3)3·6H2O] preparation 325.8g La2O3, every 750.2g [Al (NO3)3·9H2O] preparation 102.0g Al2O3, every 297.5g [Zn (NO3)2·6H2O] preparation 81.4g ZnO, every 256.4g [Mg (NO3)2·6H2O] preparation 40.3g MgO, calculate consumption needed for preparing the catalyst H2PtCl6·6H2O、Pd(NO3)2·2H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、Zr(NO3)4·5H2O、Cu(NO3)2、Fe (NO3)3·9H2O、La(NO3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O、Mg(NO3)2·6H2The quality of O；
According to catalyst coatings described in every 100g need 5~15g average molecular weight be 20000 polyethylene glycol and 25~ The ratio of 50g nitric acid calculates the quality of the polyethylene glycol and nitric acid that consume needed for prepares coating slurries；And according in Aluminum sol Al2O3Actual mass percentages calculate prepares coating slurries needed for consumption Aluminum sol quality；
Step 2: the preparation of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve:
Cu (NO is weighed according to the quality that step 1 determines3)2With Fe (NO3)3·9H2O, and according to every mole of Cu (NO3)2With Every mole of Fe (NO3)3·9H2The ratio of the corresponding 1~2L deionized water of O, by Cu (NO3)2With Fe (NO3)3·9H2O be added to go from It is agitated to be configured to mixed solution in sub- water；The type ZSM 5 molecular sieve for having determined that quality is added in the mixed solution, and Liquid, is evaporated by 6~12h of high degree of agitation at 70~80 DEG C at 70~80 DEG C；Then after being evaporated at 90~110 DEG C Powder dries 4~8h, and 2~3h of high-temperature roasting at 550~600 DEG C, gained is Cu-Fe bimetallic-modified ZSM-5 type molecule Sieve；
Step 3: the preparation of La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides:
La (NO is weighed by aforementioned fixed quality3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O and Mg (NO3)2·6H2O answers the ratio of 0.5~1L deionized water according to every mole of Zn ion and every mole of Mg ion pair, by La (NO3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O and Mg (NO3)2·6H2O is added into deionized water, through abundant Stirring, obtained solution are preceding body liquid；
The NaOH and Na of sufficient amount are weighed again2CO3, and the molal quantity and Na of NaOH2CO3Molal quantity ratio be 2:1, The ratio that 1L deionized water is corresponded to according to every moles of NaOH, by NaOH and Na2CO3Be added into deionized water, be sufficiently stirred until NaOH and Na2CO3It is completely dissolved, obtained solution is buffer；
Buffer is added in precursor liquid with the speed of 30~50ml/min, is vigorously stirred, meanwhile, with pH value analyzer company It is continuous to measure the pH value that the precursor liquid of buffer is being added；When pH value is between 9.5~10.5, stop that buffer is added, Continue 2~4h of stirring, still aging 24~48h, filters the solid matter after isolating ageing；By the solid matter spend from Sub- water rinses 3~5 times, dry 8~16h at 90~110 DEG C, 2~4h of roasting at 500~600 DEG C, will after natural cooling It grinds 1h on ball mill to get La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides are arrived；
Step 4: the preparation of coating paste:
Weigh the H for having determined that quality2PtCl6·6H2O、Pd(NO3)2·2H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、 Zr(NO3)4·5H2O, Aluminum sol, polyethylene glycol and nitric acid and the Cu-Fe bimetallic-modified ZSM-5 type molecule being prepared Sieve, La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides, and whole raw materials are added to quality and are equivalent to and are planned It prepares in 10~15 times of catalyst coatings gross mass of deionized water, is sufficiently stirred；With the NaOH solution of 1mol/L or pure glacial acetic acid The pH value for adjusting mixed solution is 3~4, continues to stir mixture to form uniform suspension；The suspension is ground in wet process It is ground to median on grinding machine to be in 1.0~1.2 micron ranges, then stirs the suspension after grinding at 60~80 DEG C Mix 16~for 24 hours to get to coating paste；
Step 5: the coating of coating paste
Design the quality of 400 mesh cordierite honeycomb ceramics carriers of the catalyst coatings of being applied；According to catalyst coatings and violet The mass percent of green stone honeycomb ceramic carrier are as follows: 10~30%/90~70% carries out ingredient, and is impregnated, dried as follows And calcination processing:
The cordierite honeycomb ceramic carrier of 400 cylindrical mesh is immersed in 60~80 DEG C of the coating paste, and The upper surface of cordierite honeycomb ceramic carrier is higher than the liquid level of the coating paste；Slurries to be coated are promoted naturally full of the violet Behind all ducts of green stone honeycomb ceramic carrier, cordierite honeycomb ceramic carrier is taken out from coating paste, is blown off in duct Residual fluid, dry 6~12h at 90~110 DEG C, then 2~4h is calcined at 500~600 DEG C；
Above-mentioned dipping, drying and calcination process 2~3 times are repeated to get the bavin based on modified hydrotalcite Derived Oxides is arrived Oil machine catalyst.
Use for diesel engine catalyst made from above-mentioned preparation method based on modified hydrotalcite Derived Oxides is packaged, And the catalyst after encapsulation is installed in the exhaust duct of diesel vehicle, by NOx absorption-reduction reaction purification of diesel vehicle exhaust NOx pollutant.
Compared with prior art, the beneficial effects of the present invention are:
Using most of precious metal material in Cu-Fe bimetallic-modified type ZSM 5 molecular sieve substitution LNT catalyst, no It reduced by only the cost of material for preparing catalyst, and the sulfur resistive, heat resistance and reduction reaction that improve LNT catalyst are urged Change activity；Meanwhile modification of the Cu-Fe bimetallic to type ZSM 5 molecular sieve, also extend the high catalytic activity temperature of LNT catalyst Spend window.Using major part γ-Al in La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides substitution LNT catalyst2O3It applies Layer basic material provides attached in addition to BaO adsorbent while keeping coating stability not reduce for LNT catalyst Add adsorbent, is added significantly to the NOx adsorption capacity of LNT catalyst；And two kinds of elements of La, Zn respectively replace Al, Mg element Generation, when further improving the NOx absorption property of hydrotalcite Derived Mixed Oxides material, especially low temperature (300 DEG C of <) NOx saturated extent of adsorption significantly improves.In addition, La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides making coatings basis material Material can introduce La element in catalyst coat, improve the high-temperature stability of catalyst, and promote CeO2With major catalyst it Between concerted catalysis act on more efficient performance.
Detailed description of the invention
Fig. 1 is LNT catalyst NOx purifying property engine evaluation system schematic diagram.
Wherein: 1- dynamometer machine；2- shaft coupling；3- tests diesel engine；4- inlet air flow meter；5- air inlet air conditioning；6- fuel injector； 7- fuel injection control systems；8- exhaust sampling port A；9- temperature sensor A；10- is vented voltage-stablizer；11- temperature sensor B； 12-LNT catalyst converter；13- temperature sensor C；14- exhaust sampling port B；15- exhaust gas sampling channel；The analysis of 16- engine exhaust Instrument；17- air pump.
Fig. 2 is to utilize the LNT catalyst NOx purifying property engine evaluation system, is vented in diesel engine Lean Burn Operating Temperature is 250 DEG C, air speed 30000h-1Steady state condition when, the lower diesel engine of Examples 1 to 4 prepared catalyst catalysis is arranged In gas NOx absorption-reduction reaction, the purification efficiency of NOx.
Fig. 3 is to utilize the LNT catalyst NOx purifying property engine evaluation system, is vented in diesel engine Lean Burn Operating Temperature is 350 DEG C, air speed 50000h-1Steady state condition when, the lower diesel engine of Examples 1 to 4 prepared catalyst catalysis is arranged In gas NOx absorption-reduction reaction, the purification efficiency of NOx.
Fig. 4 is to be recycled using the LNT catalyst NOx purifying property engine evaluation system in European steady state test Diesel engine when (European steady state cycle-ESC) is tested, under the catalysis of Examples 1 to 4 prepared catalyst It is vented in NOx absorption-reduction reaction, the purification efficiency of NOx.
Specific embodiment
Below by way of specific embodiment and in conjunction with attached drawing, technical solution of the present invention will be further described.It needs Bright be the embodiment be it is narrative, and non-limiting, the content that is covered of the present invention is not limited to following embodiments.
A kind of use for diesel engine catalyst based on modified hydrotalcite Derived Oxides proposed by the present invention, including Cu-Fe are bis- Metal-modified type ZSM 5 molecular sieve, Pt, Pd, BaO, CeO2-ZrO2Solid solution, La-Zn bimetallic-modified hydrotalcite derivative are compound Oxide, γ-Al2O3And 400 mesh cordierite honeycomb ceramics carrier.
(1) main reminder of catalyst of the present invention is made of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve and precious metals pt and Pd Agent, and the mass percent of the quality sum of precious metals pt and Pd and Cu-Fe bimetallic-modified type ZSM 5 molecular sieve are as follows: 2~ 5%/98~95%, the sum of mass percent is 100%.
(2) Cu element is dispersed in ZSM-5 in the form of CuO in the Cu-Fe bimetallic-modified type ZSM 5 molecular sieve In type molecular sieve surface and micropore, Fe element is with Fe2O3Form be dispersed in type ZSM 5 molecular sieve surface and micropore, and Described CuO, Fe2O3With the mass percent of type ZSM 5 molecular sieve are as follows: 5~15%/5~10%/90~75%, mass percent The sum of be 100%.
(3) mass percent of the precious metals pt and Pd are as follows: 25~50%/75~50%, the sum of mass percent is 100%.
(4) adsorbent of catalyst of the present invention is made of BaO.
(5) by CeO2-ZrO2Solid solution forms the co-catalyst of catalyst of the present invention, and CeO2With ZrO2Quality percentage Than are as follows: 80~50%/20~50%, the sum of mass percent is 100%.
(6) by La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides and γ-Al2O3Form the painting of catalyst of the present invention Layer basic material, and the La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides and γ-Al2O3Mass percent are as follows: 75~90%/25~10%, the sum of mass percent is 100%.
(7) the La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides constitute the coating basis of catalyst of the present invention One of material also undertakes the effect of additional adsorbent in the catalyst, wherein tetra- kinds of La, Al and Zn, Mg elements respectively with La2O3、Al2O3It is dispersed in the La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides with the form of ZnO, MgO, and La2O3And Al2O3Mole (mol) percentage are as follows: the sum of 50~80%/50~20%, mol percentage be 100%；ZnO and The mol percentage of MgO are as follows: the sum of 25~75%/75~25%, mol percentage is 100%；Meanwhile the La-Zn bimetallic In modified hydrotalcite Derived Mixed Oxides the sum of mol number of La ion and Al ion and the mol number of Zn ion and Mg ion it The ratio of sum are as follows: 1:3.
(8) γ-Al in the coating basic material2O3It is converted by the Aluminum sol as adhesive coating.
(9) major catalyst that is made of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve and precious metals pt and Pd, by BaO group At adsorbent, by CeO2-ZrO2The co-catalyst and derived by La-Zn bimetallic-modified hydrotalcite compound that solid solution forms Oxide and γ-Al2O3The coating basic material of composition, collectively constitutes the catalyst coatings of catalyst of the present invention, wherein main catalytic Agent, adsorbent, co-catalyst and coating basic material mass percent respectively correspond are as follows: 5~10%/10%/5~10%/ 80~70%, the sum of mass percent is 100%.
(10) it is made of that the present invention is based on the derivative oxygen of modified hydrotalcite the catalyst coatings and 400 mesh cordierite honeycomb ceramics The use for diesel engine catalyst of compound, wherein 400 mesh cordierite honeycomb ceramics are the carrier of catalyst of the present invention, and need Catalyst coatings are coated on the 400 mesh cordierite honeycomb ceramics carrier, and the catalyst coatings and the 400 mesh cordierite The mass percent of honeycomb ceramic carrier are as follows: 10~30%/90~70%, the sum of mass percent is 100%.
The step of preparation method of use for diesel engine catalyst based on modified hydrotalcite Derived Oxides, concrete technology, wraps It includes: (1) preparing the determination of catalyst raw material dosage；(2) preparation of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve；(3)La-Zn The preparation of bimetallic-modified hydrotalcite Derived Mixed Oxides；(4) preparation of coating paste；(5) coating of coating paste.
Below by way of the preparation method of specific embodiment the present invention will be described in detail catalyst.
Embodiment 1
(1) determination of catalyst raw material dosage is prepared
Major catalyst precious metals pt and Pd quality sum change with Cu-Fe bimetallic in design 1 prepared catalyst of embodiment The mass ratio of property type ZSM 5 molecular sieve are as follows: 2%:98%；CuO, Fe in Cu-Fe bimetallic-modified type ZSM 5 molecular sieve2O3With The mass ratio of type ZSM 5 molecular sieve are as follows: 15%:10%:75%；The mass ratio of precious metals pt and Pd are as follows: 50%:50%； CeO in co-catalyst2、ZrO2Mass ratio are as follows: 80%:20%；La-Zn bimetallic-modified hydrotalcite in coating basic material Derived Mixed Oxides and γ-Al2O3Mass ratio are as follows: 90%:10%；La-Zn bimetallic-modified hydrotalcite derives composite oxygen La in compound2O3And Al2O3Mol ratio are as follows: 80%:20%；The mol ratio of ZnO and MgO are as follows: 50%:50%；Main catalytic Agent, adsorbent, co-catalyst and coating basic material mass ratio are as follows: 10%:10%:10%:70%；Every 100g catalysis applies It is 20000 polyethylene glycol and 25g nitric acid that layer, which needs 15g average molecular weight,.Preparation 2000g catalysis is calculated according to conversion scale Raw material dosage needed for coating: H2PtCl6·6H2O 5.3g、Pd(NO3)2·2H2O 5.0g、Cu(NO3)269.4g、Fe(NO3)3· 9H2O 99.2g, type ZSM 5 molecular sieve 147.0g, Ba (CH3COO)2 333.2g、Ce(NO3)3·6H2O403.6g、Zr (NO3)4·5H2O 139.4g、La(NO3)3·6H2O 1351.0g、Al(NO3)3·9H2O 292.6g、Zn(NO3)2·6H2O 1740.4g、Mg(NO3)2·6H2O 1499.9g、γ-Al2O3140.0g, nitric acid 500g and average molecular weight be 20000 it is poly- Ethylene glycol 300g.Al in Aluminum sol used in the present embodiment2O3Content be 10.8%, thus calculate and need Aluminum sol 1296.3g。
(2) preparation of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve
Cu (NO is weighed according to fixed quality3)2With Fe (NO3)3·9H2O, by described two raw materials addition 0.7L go from It is agitated to be configured to mixed solution in sub- water；The type ZSM 5 molecular sieve for having determined that quality is added in the mixed solution, and Liquid is evaporated at 70 DEG C by the high degree of agitation 12h at 70 DEG C again after the completion of stirring.Then by the powder after being evaporated at 90 DEG C 8h is dried, Cu-Fe bimetallic-modified type ZSM 5 molecular sieve can be obtained in the high-temperature roasting 3h at 550 DEG C of the powder after drying.
(3) preparation of La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides
La (NO is weighed by aforementioned fixed quality3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O and Mg (NO3)2·6H24 kinds of raw materials are added in 11L deionized water, are sufficiently stirred, are configured to solution by O, are preceding body liquid.Again Weigh 200g NaOH and 265g Na2CO3, described two substances are added in 5000g deionized water, are sufficiently stirred until NaOH And Na2CO3It is completely dissolved, is buffer.Then buffer is added in precursor liquid with the speed of 50ml/min, is vigorously stirred, together When, the pH value that the precursor liquid of buffer is being added continuously is measured with pH value analyzer；PH value to the precursor liquid is in 9.5 When between~10.5, stop that buffer is added, and precursor liquid is continued to stir 2h；Precursor liquid after the completion of the stirring is stood Ageing for 24 hours, has a large amount of solid matters to generate in forerunner's liquid container after ageing, isolate consolidating in forerunner's liquid container by filtering State substance, then solid matter deionized water is rinsed 3 times；Solid matter after the flushing is dry at 90 DEG C 16h, then the solid matter after drying is roasted into 4h at 500 DEG C, the solid matter natural cooling after roasting, by it in ball mill La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides can be obtained in upper grinding 1h.
(4) preparation of coating paste
Weigh the H for having determined that quality2PtCl6·6H2O、Pd(NO3)2·2H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、 Zr(NO3)4·5H2O, Aluminum sol, polyethylene glycol and nitric acid and the Cu-Fe bimetallic-modified ZSM-5 type molecule being prepared Sieve, La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides, and whole raw materials are added to 20000g deionized water In, it is sufficiently stirred；The pH value for adjusting mixed solution with the NaOH solution of 1mol/L or pure glacial acetic acid continues to be stirred for 3~4 Object is to form uniform suspension；By the suspension be ground on wet grinding mill median (D50 partial size) be in 1.0~ In 1.2 micron ranges, then the suspension after grinding is stirred at 60 DEG C for 24 hours to get to coating paste.
(5) coating of coating paste
Design the quality of 400 mesh cordierite honeycomb ceramics carriers of the catalyst coatings of being applied；It weighs and has determined that quality The ceramic monolith is immersed in 60 DEG C of the coating paste, and guarantees ceramic load by 400 mesh cordierite honeycomb ceramics carriers The upper surface of body is slightly above slurry liquid level；After slurries promote all ducts full of carrier naturally, carrier is taken from slurry Out, residual fluid in duct is blown off, the dry 12h at 90 DEG C, then 4h is roasted at 500 DEG C；Repeat above-mentioned dipping, drying and roasting Burning process 3 times is to get arriving the use for diesel engine catalyst based on modified hydrotalcite Derived Oxides.
The diesel oil based on modified hydrotalcite Derived Oxides obtained using catalyst preparation carrying method described in embodiment 1 Machine catalyst, the mass percent of catalyst coatings and 400 mesh cordierite honeycomb ceramics carriers are as follows: 28~29%/72~71%, The sum of mass percent is 100%.
Embodiment 2
(1) determination of catalyst raw material dosage is prepared
Major catalyst precious metals pt and Pd quality sum change with Cu-Fe bimetallic in design 2 prepared catalyst of embodiment The mass ratio of property type ZSM 5 molecular sieve are as follows: 5%:95%；CuO, Fe in Cu-Fe bimetallic-modified type ZSM 5 molecular sieve2O3With The mass ratio of type ZSM 5 molecular sieve are as follows: 5%:5%:90%；The mass ratio of precious metals pt and Pd are as follows: 25%:75%；It helps CeO in catalyst2、ZrO2Mass ratio are as follows: 50%:50%；La-Zn bimetallic-modified hydrotalcite spreads out in coating basic material Raw composite oxides and γ-Al2O3Mass ratio are as follows: 75%:25%；La-Zn bimetallic-modified hydrotalcite derives combined oxidation La in object2O3And Al2O3Mol ratio are as follows: 50%:50%；The mol ratio of ZnO and MgO are as follows: 75%:25%；Major catalyst, The mass ratio of adsorbent, co-catalyst and coating basic material are as follows: 10%:10%:10%:70%；Every 100g catalyst coatings Needing 15g average molecular weight is 20000 polyethylene glycol and 50g nitric acid.Preparation 2000g catalysis is calculated according to conversion scale to apply Raw material dosage needed for layer: H2PtCl6·6H2O 6.6g、Pd(NO3)2·2H2O 18.8g、Cu(NO3)222.4g、Fe(NO3)3· 9H2O 48.1g, type ZSM 5 molecular sieve 171.0g, Ba (CH3COO)2 333.2g、Ce(NO3)3·6H2O252.2g、Zr (NO3)4·5H2O 348.5g、La(NO3)3·6H2O 709.7g、Al(NO3)3·9H2O 614.8g、Zn(NO3)2·6H2O 2194.2g、Mg(NO3)2·6H2O 630.4g、γ-Al2O3350.0g, nitric acid 1000g and average molecular weight be 20000 it is poly- Ethylene glycol 300g.Al in Aluminum sol used in the present embodiment2O3Content be 10.8%, thus calculate and need Aluminum sol 3240.7g。
(2) preparation of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve
Cu (NO is weighed according to fixed quality3)2With Fe (NO3)3·9H2O, by described two raw materials add 0.46L go from It is agitated to be configured to mixed solution in sub- water；The type ZSM 5 molecular sieve for having determined that quality is added in the mixed solution, and Liquid is evaporated at 80 DEG C by the high degree of agitation 6h at 80 DEG C again after the completion of stirring.Then by the powder after being evaporated at 110 DEG C 4h is dried, Cu-Fe bimetallic-modified type ZSM 5 molecular sieve can be obtained in the high-temperature roasting 2h at 600 DEG C of the powder after drying.
(3) preparation of La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides
La (NO is weighed by aforementioned fixed quality3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O and Mg (NO3)2·6H24 kinds of raw materials are added in 5L deionized water, are sufficiently stirred, are configured to solution by O, are preceding body liquid.Claim again Take 200g NaOH and 265g Na2CO3, will described two substances be added 5000g deionized water in, be sufficiently stirred until NaOH and Na2CO3It is completely dissolved, is buffer.Then buffer is added in precursor liquid with the speed of 30ml/min, is vigorously stirred, together When, the pH value that the precursor liquid of buffer is being added continuously is measured with pH value analyzer；PH value to the precursor liquid is in 9.5 When between~10.5, stop that buffer is added, and precursor liquid is continued to stir 4h；Precursor liquid after the completion of the stirring is stood It is aged 48h, there are a large amount of solid matters to generate in forerunner's liquid container after ageing, isolates consolidating in forerunner's liquid container by filtering State substance, then solid matter deionized water is rinsed 5 times；Solid matter after the flushing is dry at 110 DEG C 8h, then the solid matter after drying is roasted into 2h at 600 DEG C, the solid matter natural cooling after roasting, by it in ball mill La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides can be obtained in upper grinding 1h.
(4) preparation of coating paste
Weigh the H for having determined that quality2PtCl6·6H2O、Pd(NO3)2·2H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、 Zr(NO3)4·5H2O, Aluminum sol, polyethylene glycol and nitric acid and the Cu-Fe bimetallic-modified ZSM-5 type molecule being prepared Sieve, La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides, and whole raw materials are added to 20000g deionized water In, it is sufficiently stirred；The pH value for adjusting mixed solution with the NaOH solution of 1mol/L or pure glacial acetic acid continues to be stirred for 3~4 Object is to form uniform suspension；The suspension is ground to D50 partial size on wet grinding mill and is in 1.0~1.2 microns of models In enclosing, then the suspension after grinding is stirred to 16h at 80 DEG C to get coating paste is arrived.
(5) coating of coating paste
Design the quality of 400 mesh cordierite honeycomb ceramics carriers of the catalyst coatings of being applied；It weighs and has determined that quality The ceramic monolith is immersed in 80 DEG C of the coating paste, and guarantees ceramic load by 400 mesh cordierite honeycomb ceramics carriers The upper surface of body is slightly above slurry liquid level；After slurries promote all ducts full of carrier naturally, carrier is taken from slurry Out, residual fluid in duct is blown off, the dry 6h at 110 DEG C, then 2h is roasted at 600 DEG C；Repeat above-mentioned dipping, drying and roasting Burning process 2 times is to get arriving the use for diesel engine catalyst based on modified hydrotalcite Derived Oxides.
The diesel oil based on modified hydrotalcite Derived Oxides obtained using catalyst preparation carrying method described in embodiment 2 Machine catalyst, the mass percent of catalyst coatings and 400 mesh cordierite honeycomb ceramics carriers are as follows: 20~21%/80~79%, The sum of mass percent is 100%.
Embodiment 3
(1) determination of catalyst raw material dosage is prepared
Major catalyst precious metals pt and Pd quality sum change with Cu-Fe bimetallic in design 3 prepared catalyst of embodiment The mass ratio of property type ZSM 5 molecular sieve are as follows: 5%:95%；CuO, Fe in Cu-Fe bimetallic-modified type ZSM 5 molecular sieve2O3With The mass ratio of type ZSM 5 molecular sieve are as follows: 15%:10%:75%；The mass ratio of precious metals pt and Pd are as follows: 50%:50%； CeO in co-catalyst2、ZrO2Mass ratio are as follows: 80%:20%；La-Zn bimetallic-modified hydrotalcite in coating basic material Derived Mixed Oxides and γ-Al2O3Mass ratio are as follows: 90%:10%；La-Zn bimetallic-modified hydrotalcite derives composite oxygen La in compound2O3And Al2O3Mol ratio are as follows: 80%:20%；The mol ratio of ZnO and MgO are as follows: 75%:25%；Main catalytic Agent, adsorbent, co-catalyst and coating basic material mass ratio are as follows: 10%:10%:10%:70%；Every 100g catalysis applies It is 20000 polyethylene glycol and 30g nitric acid that layer, which needs 5g average molecular weight,.Preparation 2000g catalysis is calculated according to conversion scale Raw material dosage needed for coating: H2PtCl6·6H2O 13.3g、Pd(NO3)2·2H2O 12.5g、Cu(NO3)267.3g、Fe (NO3)3·9H2O 96.1g, type ZSM 5 molecular sieve 142.5g, Ba (CH3COO)2 333.2g、Ce(NO3)3·6H2O403.6g、 Zr(NO3)4·5H2O 139.4g、La(NO3)3·6H2O 1233.2g、Al(NO3)3·9H2O 267.1g、Zn(NO3)2·6H2O 2383.0g、Mg(NO3)2·6H2O 684.6g、γ-Al2O3The poly- second that 140.0g, nitric acid 600g and average molecular weight are 20000 Glycol 100g.Al in Aluminum sol used in the present embodiment2O3Content be 10.8%, thus calculate and need Aluminum sol 1296.3g。
(2) preparation of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve
Cu (NO is weighed according to fixed quality3)2With Fe (NO3)3·9H2O, by described two raw materials addition 0.9L go from It is agitated to be configured to mixed solution in sub- water；The type ZSM 5 molecular sieve for having determined that quality is added in the mixed solution, and Liquid is evaporated at 80 DEG C by the high degree of agitation 6h at 80 DEG C again after the completion of stirring.Then by the powder after being evaporated at 100 DEG C 6h is dried, Cu-Fe bimetallic-modified type ZSM 5 molecular sieve can be obtained in the high-temperature roasting 2h at 600 DEG C of the powder after drying.
(3) preparation of La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides
La (NO is weighed by aforementioned fixed quality3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O and Mg (NO3)2·6H24 kinds of raw materials are added in 6.5L deionized water, are sufficiently stirred, are configured to solution by O, are preceding body liquid.Again Weigh 200g NaOH and 265g Na2CO3, described two substances are added in 5000g deionized water, are sufficiently stirred until NaOH And Na2CO3It is completely dissolved, is buffer.Then buffer is added in precursor liquid with the speed of 40ml/min, is vigorously stirred, together When, the pH value that the precursor liquid of buffer is being added continuously is measured with pH value analyzer；PH value to the precursor liquid is in 9.5 When between~10.5, stop that buffer is added, and precursor liquid is continued to stir 3h；Precursor liquid after the completion of the stirring is stood It is aged 36h, there are a large amount of solid matters to generate in forerunner's liquid container after ageing, isolates consolidating in forerunner's liquid container by filtering State substance, then solid matter deionized water is rinsed 4 times；Solid matter after the flushing is dry at 100 DEG C 12h, then the solid matter after drying is roasted into 2h at 600 DEG C, the solid matter natural cooling after roasting, by it in ball mill La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides can be obtained in upper grinding 1h.
(4) preparation of coating paste
Weigh the H for having determined that quality2PtCl6·6H2O、Pd(NO3)2·2H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、 Zr(NO3)4·5H2O, Aluminum sol, polyethylene glycol and nitric acid and the Cu-Fe bimetallic-modified ZSM-5 type molecule being prepared Sieve, La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides, and whole raw materials are added to 30000g deionized water In, it is sufficiently stirred；The pH value for adjusting mixed solution with the NaOH solution of 1mol/L or pure glacial acetic acid continues to be stirred for 3~4 Object is to form uniform suspension；The suspension is ground to D50 partial size on wet grinding mill and is in 1.0~1.2 microns of models In enclosing, then the suspension after grinding is stirred to 20h at 70 DEG C to get coating paste is arrived.
(5) coating of coating paste
Design the quality of 400 mesh cordierite honeycomb ceramics carriers of the catalyst coatings of being applied；It weighs and has determined that quality The ceramic monolith is immersed in 70 DEG C of the coating paste, and guarantees ceramic load by 400 mesh cordierite honeycomb ceramics carriers The upper surface of body is slightly above slurry liquid level；After slurries promote all ducts full of carrier naturally, carrier is taken from slurry Out, residual fluid in duct is blown off, the dry 9h at 100 DEG C, then 4h is roasted at 500 DEG C；Repeat above-mentioned dipping, drying and roasting Burning process 2 times is to get arriving the use for diesel engine catalyst based on modified hydrotalcite Derived Oxides.
The diesel oil based on modified hydrotalcite Derived Oxides obtained using catalyst preparation carrying method described in embodiment 3 Machine catalyst, the mass percent of catalyst coatings and 400 mesh cordierite honeycomb ceramics carriers are as follows: 10~11%/90~89%, The sum of mass percent is 100%.
Embodiment 4
(1) determination of catalyst raw material dosage is prepared
Major catalyst precious metals pt and Pd quality sum change with Cu-Fe bimetallic in design 4 prepared catalyst of embodiment The mass ratio of property type ZSM 5 molecular sieve are as follows: 5%:95%；CuO, Fe in Cu-Fe bimetallic-modified type ZSM 5 molecular sieve2O3With The mass ratio of type ZSM 5 molecular sieve are as follows: 10%:10%:80%；The mass ratio of precious metals pt and Pd are as follows: 50%:50%； CeO in co-catalyst2、ZrO2Mass ratio are as follows: 80%:20%；La-Zn bimetallic-modified hydrotalcite in coating basic material Derived Mixed Oxides and γ-Al2O3Mass ratio are as follows: 80%:20%；La-Zn bimetallic-modified hydrotalcite derives composite oxygen La in compound2O3And Al2O3Mol ratio are as follows: 50%:50%；The mol ratio of ZnO and MgO are as follows: 50%:50%；Main catalytic Agent, adsorbent, co-catalyst and coating basic material mass ratio are as follows: 5%:10%:10%:75%；Every 100g catalysis applies It is 20000 polyethylene glycol and 40g nitric acid that layer, which needs 10g average molecular weight,.Preparation 2000g catalysis is calculated according to conversion scale Raw material dosage needed for coating: H2PtCl6·6H2O 6.6g、Pd(NO3)2·2H2O 6.3g、Cu(NO3)222.4g、Fe(NO3)3· 9H2O 48.1g, type ZSM 5 molecular sieve 76g, Ba (CH3COO)2 333.2g、Ce(NO3)3·6H2O403.6g、Zr(NO3)4· 5H2O 139.4g、La(NO3)3·6H2O 897.6g、Al(NO3)3·9H2O 777.6g、Zn(NO3)2·6H2O 1850.2g、 Mg(NO3)2·6H2O 1594.6g、γ-Al2O3The polyethylene glycol that 300.0g, nitric acid 800g and average molecular weight are 20000 200g.Al in Aluminum sol used in the present embodiment2O3Content be 10.8%, thus calculate and need Aluminum sol 2777.8g.
(2) preparation of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve
Cu (NO is weighed according to fixed quality3)2With Fe (NO3)3·9H2O, by described two raw materials addition 0.4L go from It is agitated to be configured to mixed solution in sub- water；The type ZSM 5 molecular sieve for having determined that quality is added in the mixed solution, and Liquid is evaporated at 70 DEG C by the high degree of agitation 12h at 70 DEG C again after the completion of stirring.Then by the powder after being evaporated at 90 DEG C 8h is dried, Cu-Fe bimetallic-modified type ZSM 5 molecular sieve can be obtained in the high-temperature roasting 3h at 550 DEG C of the powder after drying.
(3) preparation of La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides
La (NO is weighed by aforementioned fixed quality3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O and Mg (NO3)2·6H24 kinds of raw materials are added in 7L deionized water, are sufficiently stirred, are configured to solution by O, are preceding body liquid.Claim again Take 200g NaOH and 265g Na2CO3, will described two substances be added 5000g deionized water in, be sufficiently stirred until NaOH and Na2CO3It is completely dissolved, is buffer.Then buffer is added in precursor liquid with the speed of 40ml/min, is vigorously stirred, together When, the pH value that the precursor liquid of buffer is being added continuously is measured with pH value analyzer；PH value to the precursor liquid is in 9.5 When between~10.5, stop that buffer is added, and precursor liquid is continued to stir 3h；Precursor liquid after the completion of the stirring is stood Ageing for 24 hours, has a large amount of solid matters to generate in forerunner's liquid container after ageing, isolate consolidating in forerunner's liquid container by filtering State substance, then solid matter deionized water is rinsed 4 times；Solid matter after the flushing is dry at 100 DEG C 12h, then the solid matter after drying is roasted into 4h at 500 DEG C, the solid matter natural cooling after roasting, by it in ball mill La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides can be obtained in upper grinding 1h.
(4) preparation of coating paste
Weigh the H for having determined that quality2PtCl6·6H2O、Pd(NO3)2·2H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、 Zr(NO3)4·5H2O, Aluminum sol, polyethylene glycol and nitric acid and the Cu-Fe bimetallic-modified ZSM-5 type molecule being prepared Sieve, La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides, and whole raw materials are added to 25000g deionized water In, it is sufficiently stirred；The pH value for adjusting mixed solution with the NaOH solution of 1mol/L or pure glacial acetic acid continues to be stirred for 3~4 Object is to form uniform suspension；The suspension is ground to D50 partial size on wet grinding mill and is in 1.0~1.2 microns of models In enclosing, then the suspension after grinding is stirred to 20h at 70 DEG C to get coating paste is arrived.
(5) coating of coating paste
Design the quality of 400 mesh cordierite honeycomb ceramics carriers of the catalyst coatings of being applied；It weighs and has determined that quality The ceramic monolith is immersed in 70 DEG C of the coating paste, and guarantees ceramic load by 400 mesh cordierite honeycomb ceramics carriers The upper surface of body is slightly above slurry liquid level；After slurries promote all ducts full of carrier naturally, carrier is taken from slurry Out, residual fluid in duct is blown off, the dry 12h at 90 DEG C, then 4h is roasted at 500 DEG C；Repeat above-mentioned dipping, drying and roasting Burning process 3 times is to get arriving the use for diesel engine catalyst based on modified hydrotalcite Derived Oxides.
The diesel oil based on modified hydrotalcite Derived Oxides obtained using catalyst preparation carrying method described in embodiment 4 Machine catalyst, the mass percent of catalyst coatings and 400 mesh cordierite honeycomb ceramics carriers are as follows: 25~26%/75~74%, The sum of mass percent is 100%.
It is made to the Examples 1 to 4 using LNT catalyst NOx purifying property engine evaluation system shown in FIG. 1 Diesel exhaust gas NOx absorption-reduction purification performance of standby catalyst is evaluated.It needs to urge prepared by embodiment 1-4 before test Agent is respectively cut, is respectively combined into 4L integral catalyzer, and seals to the cutting, the integral catalyzer being combined into Dress processing.Test method are as follows:
(1) steady state condition is tested: using dynamometer machine 1 and 2 Control experiment engine of shaft coupling (CY4102 diesel engine) 3 Torque and revolving speed, and reach stable state using the temperature and humidity that air inlet air conditioning 5 adjusts engine charge, successively adjustment is started The ratio of machine extraction flow and catalyst volume is respectively 30000h-1And 50000h-1, and successively control 12 center of LNT catalyst converter The temperature of point is respectively 250 DEG C and 350 DEG C, carries out catalyst n Ox absorption-reduction reaction catalytically active assessment.In test, pass through Fuel injection control systems 7 adjust fuel injector 6 to the delivery rate of diesel engine, realize in diesel engine operational process, lean-burn/fuel-rich The switching of operating condition.The exhaust that diesel engine in-cylinder combustion is formed adsorb-go back into LNT catalyst converter after being vented voltage-stablizer 10 Former purified treatment.LNT catalyst converter handles forward and backward diesel exhaust gas and passes through respectively from exhaust sampling port A8 and exhaust sampling port B14 Exhaust gas sampling channel 15 enters engine exhaust analyzer 16 and carries out NOx concentration analysis, and the gas after NOx is analyzed passes through gas Pump 17 gives off laboratory.The delivery temperature of 10 front and back of temperature sensor A9 and temperature sensor B 11 measurement exhaust voltage-stablizer, And temperature sensor C 13 measures the temperature at LNT catalyst converter center.The measured temperature and charge flow rate of 3 temperature sensors The charge flow rate measured value of meter 4 provides feedback parameter for the control strategy of fuel injection control systems and dynamometer machine.Using described LNT catalyst NOx purifying property engine evaluation system, diesel exhaust gas temperature be 250 DEG C, air speed 30000h-1When with And delivery temperature is 350 DEG C, air speed 50000h-1When, the diesel exhaust gas NOx under the catalysis of Examples 1 to 4 prepared catalyst In absorption-reduction reaction, the purification efficiency difference of NOx is as shown in Figures 2 and 3.
(2) ESC is tested: using the LNT catalyst NOx purifying property engine evaluation system, and according to national standards GB 17691-2005 " automobile-used compression-ignited, gaseous fuel spark-ignition engine and automobile exhaust pollutant discharge limit value and measurement side Method (Chinese III, IV, V stage) " specified in ESC testing regulations evaluation Examples 1 to 4 prepared catalyst catalysis under bavin The clean-up effect that oil machine is vented NOx in NOx absorption-reduction reaction is as shown in Figure 4.
To sum up, catalyst of the present invention is using Cu-Fe bimetallic-modified type ZSM 5 molecular sieve and precious metals pt, Pd composition master Catalyst；BaO forms adsorbent；CeO2-ZrO2Solid solution forms co-catalyst；La-Zn bimetallic-modified hydrotalcite derivative is compound Oxide and γ-Al2O3Form coating basic material；400 mesh cordierite honeycomb ceramics are catalyst carrier.Preparation process includes: The determination of catalyst raw material dosage；Cu-Fe bimetallic-modified type ZSM 5 molecular sieve, La-Zn bimetallic-modified hydrotalcite are derivative multiple Close the preparation of oxide and the preparation and coating of coating paste.Pass through the circulation change of dilute/fuel-rich operating condition of diesel engine, catalyst Can efficient catalytic exhaust in NOx absorption-reduction purification reaction.The present invention uses Cu-Fe bimetallic-modified ZSM-5 type molecule Most of precious metal material in sieve substitution LNT catalyst, not only reduces the cost of material for preparing catalyst, and improve Sulfur resistive, heat resistance and the reduction reaction catalytic activity of LNT catalyst；Meanwhile being spread out using La-Zn bimetallic-modified hydrotalcite Major part γ-Al in raw composite oxides substitution LNT catalyst2O3Coating basic material is keeping coating stability not reduce Meanwhile additional adsorbent is provided for LNT catalyst, it is added significantly to the NOx adsorption capacity of LNT catalyst.
Although above in conjunction with attached drawing, invention has been described, and the invention is not limited to above-mentioned specific implementations Mode, the above mentioned embodiment is only schematical, rather than restrictive, and those skilled in the art are at this Under the enlightenment of invention, without deviating from the spirit of the invention, many variations can also be made, these belong to of the invention Within protection.

Claims (6)

1. a kind of use for diesel engine catalyst based on modified hydrotalcite Derived Oxides, including modified ZSM-5 type molecular sieve, Pt, Pd、BaO、CeO2-ZrO2Solid solution, modified hydrotalcite Derived Mixed Oxides, γ-Al2O3And 400 mesh cordierite honeycomb pottery Ceramic carrier；It is characterized by:
The modified ZSM-5 type molecular sieve is Cu-Fe bimetallic-modified type ZSM 5 molecular sieve, wherein Cu element is with the shape of CuO Formula is dispersed in type ZSM 5 molecular sieve surface and micropore, and Fe element is with Fe2O3Form be dispersed in ZSM-5 type molecule It sieves in surface and micropore, and described CuO, Fe2O3With the mass percent of type ZSM 5 molecular sieve are as follows: 5~15%/5~10%/90 ~75%, the sum of mass percent is 100%；
The modified hydrotalcite Derived Mixed Oxides are La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides, the La- Zn bimetallic-modified hydrotalcite Derived Mixed Oxides are by the part La substitution Al2O36MgO type houghite derives composite oxygen Al in compound, by the part Zn substitution Al2O3Mg in 6MgO type houghite Derived Mixed Oxides and formed, wherein Tetra- kinds of La, Al and Zn, Mg elements are respectively with La2O3、Al2O3The La-Zn bimetallic-modified is dispersed in the form of ZnO, MgO In hydrotalcite Derived Mixed Oxides, and La2O3And Al2O3Molar percentage are as follows: 50~80%/50~20%, Mole percent Than the sum of be 100%；The molar percentage of ZnO and MgO are as follows: 25~75%/75~25%, the sum of molar percentage is 100%； Meanwhile the sum of molal quantity of La ion and Al ion and Zn in the La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides The ratio of the sum of the molal quantity of ion and Mg ion is 1:3；
The Cu-Fe bimetallic-modified type ZSM 5 molecular sieve and Pt and Pd constitute the major catalyst of catalyst, the matter of Pt and Pd Mass percent of the sum of the amount with Cu-Fe bimetallic-modified type ZSM 5 molecular sieve are as follows: 2~5%/98~95%, mass percent The sum of be 100%；The BaO constitutes the adsorbent of catalyst；The CeO2-ZrO2Solid solution constitutes helping for catalyst and urges Agent；The La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides and γ-Al2O3Constitute the coating basis material of catalyst Material；The La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides and γ-Al2O3Mass percent are as follows: 75~90%/25 ~10%, the sum of mass percent is 100%；
The major catalyst, adsorbent, co-catalyst and coating basic material constitute the catalyst coatings of catalyst, the main reminder Agent, adsorbent, co-catalyst and coating basic material mass percent respectively correspond are as follows: 5~10%/10%/5~ 10%/80~70%, the sum of mass percent is 100%；
Catalyst is constituted by the catalyst coatings and 400 mesh cordierite honeycomb ceramics, wherein the 400 mesh cordierite honeycomb Ceramics are the carrier of catalyst, and the catalyst coatings are coated in 400 mesh cordierite honeycomb ceramics, and the catalyst coatings With the mass percent of 400 mesh cordierite honeycomb ceramics are as follows: 10~30%/90~70%, the sum of mass percent is 100%.
2. according to claim 1 based on the use for diesel engine catalyst of modified hydrotalcite Derived Oxides, it is characterised in that: institute It states in co-catalyst, CeO2With ZrO2Mass percent are as follows: 80~50%/20~50%, the sum of mass percent be 100%.
3. according to claim 1 based on the use for diesel engine catalyst of modified hydrotalcite Derived Oxides, it is characterised in that: institute It states in major catalyst, the mass percent of Pt and Pd are as follows: 25~50%/75~50%, the sum of mass percent is 100%.
4. the use for diesel engine catalyst according to claim 1 based on modified hydrotalcite Derived Oxides, it is characterised in that: γ-Al in the coating basic material2O3It is converted by the Aluminum sol as adhesive coating.
5. a kind of preparation side of the use for diesel engine catalyst described in accordance with the claim 1 based on modified hydrotalcite Derived Oxides Method, it is characterized in that: the following steps are included:
Step 1: preparing the determination of catalyst raw material dosage:
The sum of Pt, Pd and Cu-Fe bimetallic-modified type ZSM 5 molecular sieve in major catalyst are separately designed out according to claim 1 Mass percent；In the major catalyst, the mass percent of Pt and Pd are as follows: 25~50%/75~50%, mass percent The sum of be 100%；CuO, Fe in Cu-Fe bimetallic-modified type ZSM 5 molecular sieve2O3With the quality percentage of type ZSM 5 molecular sieve Than；CeO in co-catalyst2With ZrO2Mass percent are as follows: 80~50%/20~50%, the sum of mass percent be 100%； γ-Al in the coating basic material2O3It is converted by the Aluminum sol as adhesive coating；La- in coating basic material Zn bimetallic-modified hydrotalcite Derived Mixed Oxides and γ-Al2O3Mass percent；La-Zn bimetallic-modified hydrotalcite spreads out In raw composite oxides, La2O3And Al2O3Mol percentage and ZnO and MgO mol percentage；Major catalyst, adsorbent, The mass percent of co-catalyst and coating basic material；The quality hundred of catalyst coatings and 400 mesh cordierite honeycomb ceramics carriers Divide and compares range；And planned allocation coating slurry produces the quality of catalyst coatings；
Ratio according to each component in above-mentioned catalyst calculates separately out plan and prepares Pt, Pd, Cu-Fe bimetallic in catalyst coatings Modified ZSM-5 type molecular sieve, BaO, CeO2、ZrO2、γ-Al2O3, La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides with And CuO, Fe in Cu-Fe bimetallic-modified type ZSM 5 molecular sieve2O3With type ZSM 5 molecular sieve, La-Zn bimetallic-modified hydrotalcite La in Derived Mixed Oxides2O3、Al2O3, ZnO and MgO quality；
In conjunction with every 517.9g [H2PtCl6·6H2O] preparation 195.1g Pt, every 266.4g [Pd (NO3)2·2H2O] preparation 106.4g Pd, every 255.4g [Ba (CH3COO)2] preparation 153.3g BaO, every 434.1g [Ce (NO3)3·6H2O] preparation 172.1g CeO2, every 429.3g [Zr (NO3)4·5H2O] preparation 123.2g ZrO2, every 187.6g [Cu (NO3)2] preparation 79.5g CuO, every 808.0g [Fe (NO3)3·9H2O] preparation 159.7g Fe2O3, every 866.0g [La (NO3)3·6H2O] preparation 325.8g La2O3, every 750.2g [Al (NO3)3·9H2O] preparation 102.0g Al2O3, every 297.5g [Zn (NO3)2·6H2O] preparation 81.4g ZnO, every 256.4g [Mg (NO3)2·6H2O] preparation 40.3g MgO, calculate consumption needed for preparing the catalyst H2PtCl6·6H2O、Pd(NO3)2·2H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、Zr(NO3)4·5H2O、Cu(NO3)2、Fe (NO3)3·9H2O、La(NO3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O、Mg(NO3)2·6H2The quality of O；
Needing 5~15g average molecular weight according to catalyst coatings described in every 100g is 20000 polyethylene glycol and 25~50g nitre The ratio of acid calculates the quality of the polyethylene glycol and nitric acid that consume needed for prepares coating slurries；And according to Al in Aluminum sol2O3 Actual mass percentages calculate prepares coating slurries needed for consumption Aluminum sol quality；
Step 2: the preparation of Cu-Fe bimetallic-modified type ZSM 5 molecular sieve:
Cu (NO is weighed according to the quality that step 1 determines3)2With Fe (NO3)3·9H2O, and according to every mole of Cu (NO3)2Often rub You are Fe (NO3)3·9H2The ratio of the corresponding 1~2L deionized water of O, by Cu (NO3)2With Fe (NO3)3·9H2O is added to deionized water In, it is agitated to be configured to mixed solution；The type ZSM 5 molecular sieve for having determined that quality is added in the mixed solution, and 70 Liquid, is evaporated by 6~12h of high degree of agitation at~80 DEG C at 70~80 DEG C；Then by the powder after being evaporated at 90~110 DEG C 4~8h is dried, 2~3h of high-temperature roasting at 550~600 DEG C, gained is Cu-Fe bimetallic-modified type ZSM 5 molecular sieve；
Step 3: the preparation of La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides:
La (NO is weighed by aforementioned fixed quality3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O and Mg (NO3)2·6H2O answers the ratio of 0.5~1L deionized water according to every mole of Zn ion and every mole of Mg ion pair, by La (NO3)3·6H2O、Al(NO3)3·9H2O、Zn(NO3)2·6H2O and Mg (NO3)2·6H2O is added into deionized water, through abundant Stirring, obtained solution are preceding body liquid；
The NaOH and Na of sufficient amount are weighed again2CO3, and the molal quantity and Na of NaOH2CO3Molal quantity ratio be 2:1, according to every Moles of NaOH corresponds to the ratio of 1L deionized water, by NaOH and Na2CO3Be added into deionized water, be sufficiently stirred until NaOH and Na2CO3It is completely dissolved, obtained solution is buffer；
Buffer is added in precursor liquid with the speed of 30~50ml/min, is vigorously stirred, meanwhile, it is continuously surveyed with pH value analyzer The pH value of the precursor liquid of buffer is being added in amount；When pH value is between 9.5~10.5, stops that buffer is added, continue 2~4h, still aging 24~48h are stirred, the solid matter after isolating ageing is filtered；By the solid matter deionized water Rinse 3~5 times, dry 8~16h at 90~110 DEG C, roast 2~4h at 500~600 DEG C, after natural cooling, by its 1h is ground on ball mill to get La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides are arrived；
Step 4: the preparation of coating paste:
Weigh the H for having determined that quality2PtCl6·6H2O、Pd(NO3)2·2H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、Zr (NO3)4·5H2O, Aluminum sol, polyethylene glycol and nitric acid and the Cu-Fe bimetallic-modified type ZSM 5 molecular sieve being prepared, La-Zn bimetallic-modified hydrotalcite Derived Mixed Oxides, and whole raw materials are added to quality and are equivalent to and plan system In the deionized water of standby 10~15 times of catalyst coatings gross mass, it is sufficiently stirred；With the NaOH solution of 1mol/L or pure glacial acetic acid tune The pH value for saving mixed solution is 3~4, continues to stir mixture to form uniform suspension；By the suspension in wet grinding It is ground to median on machine to be in 1.0~1.2 micron ranges, then stirs the suspension after grinding at 60~80 DEG C 16~for 24 hours to get arrive coating paste；
Step 5: the coating of coating paste
Design the quality of 400 mesh cordierite honeycomb ceramics carriers of the catalyst coatings of being applied；According to catalyst coatings and cordierite The mass percent of honeycomb ceramic carrier are as follows: 10~30%/90~70% carries out ingredient, and is impregnated, dried and forged as follows Burning processing:
The cordierite honeycomb ceramic carrier of 400 cylindrical mesh is immersed in 60~80 DEG C of the coating paste, and violet is green The upper surface of stone honeycomb ceramic carrier is higher than the liquid level of the coating paste；Slurries to be coated are promoted naturally full of the cordierite Behind all ducts of honeycomb ceramic carrier, cordierite honeycomb ceramic carrier is taken out from coating paste, blows off in duct and remain Fluid, dry 6~12h at 90~110 DEG C, then 2~4h is calcined at 500~600 DEG C；
Above-mentioned dipping, drying and calcination process 2~3 times are repeated to get the diesel engine based on modified hydrotalcite Derived Oxides is arrived Use catalyst.
6. a kind of purposes of the use for diesel engine catalyst based on modified hydrotalcite Derived Oxides, it is characterized in that: by claim 5 Use for diesel engine catalyst based on modified hydrotalcite Derived Oxides made from the preparation method is packaged, and will be after encapsulation Catalyst be installed in the exhaust duct of diesel vehicle, pass through NOx in NOx absorption-reduction reaction purification of diesel vehicle exhaust pollution Object.
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