CN109589988B - Diesel engine double-coating catalyst based on hydrotalcite derived oxide and preparation method thereof - Google Patents

Diesel engine double-coating catalyst based on hydrotalcite derived oxide and preparation method thereof Download PDF

Info

Publication number
CN109589988B
CN109589988B CN201811651436.1A CN201811651436A CN109589988B CN 109589988 B CN109589988 B CN 109589988B CN 201811651436 A CN201811651436 A CN 201811651436A CN 109589988 B CN109589988 B CN 109589988B
Authority
CN
China
Prior art keywords
catalytic coating
composite oxide
coating
mass
preparation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201811651436.1A
Other languages
Chinese (zh)
Other versions
CN109589988A (en
Inventor
吕刚
朱越
宋崇林
李亚松
张荣鑫
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tianjin University
Original Assignee
Tianjin University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tianjin University filed Critical Tianjin University
Priority to CN201811651436.1A priority Critical patent/CN109589988B/en
Publication of CN109589988A publication Critical patent/CN109589988A/en
Application granted granted Critical
Publication of CN109589988B publication Critical patent/CN109589988B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/8986—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with manganese, technetium or rhenium
    • 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
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • 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

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Inorganic Chemistry (AREA)
  • Catalysts (AREA)

Abstract

The invention discloses a diesel engine double-coating catalyst based on hydrotalcite derived oxide and a preparation method thereof. The outer coating contains Pt and perovskite main active ingredients; a BaO adsorbent; a Ce-Zr co-catalyst; hydrotalcite-derived oxide and gamma-Al2O3Coating a base material; the inner coating contains a main active ingredient of perovskite; a BaO adsorbent; a Ce-Zr co-catalyst; hydrotalcite-derived oxide, gamma-Al2O3And SiO2Coating a base material; and a cordierite honeycomb ceramic carrier. The preparation process comprises the following steps: designing the composition of a catalyst; preparation of perovskite and hydrotalcite derived oxides and coating of inner and outer catalytic coatings. Through the cyclic change of the lean/rich combustion working condition of the diesel engine, the catalyst can efficiently catalyze the adsorption-reduction purification reaction of NOx in exhaust. By adopting the non-uniform double-coating preparation method, the distribution characteristic of the functional material is optimized, the raw material cost is reduced, and the NOx purification effect and the durability are improved.

Description

Diesel engine double-coating catalyst based on hydrotalcite derived oxide and preparation method thereof
Technical Field
The invention belongs to the technology of purifying diesel vehicle tail gas pollutants, and particularly relates to a catalyst for adsorbing-reducing and purifying Nitrogen oxide (NOx) pollutants in diesel vehicle tail gas and a preparation method thereof.
Background
Lean NOx Trap (Lean NOx Trap-LNT) technology is one of the most effective methods for controlling NOx emission of medium and small diesel engines at present, and has very high NOXConversion efficiency is to ensure NO of diesel engineXThe emission reaches one of the most potential exhaust gas post-treatment technologies of Euro V and Euro VI emission regulations. The LNT technology can effectively operate by controlling the diesel engine to alternately and circularly operate two working conditions of lean combustion and rich combustion under the action of a special adsorption-reduction catalystAnd removing NOx in the tail gas. The typical LNT technology special catalyst (LNT catalyst for short) is Pt/BaO/Al2O3Ceramic carrier system catalyst, in which noble metal Pt is used as main active component, oxygen (O) is enriched in diesel engine under lean combustion condition2) Catalytic oxidation of a portion of NO in the exhaust to NO2This part of NO2And the remaining NO is then adsorbed on the LNT catalyst by the BaO adsorbent in the form of nitrate/nitrite-based adsorbent species. When the operation is switched to the rich condition, the exhaust gas of the diesel engine contains almost no O at the moment2And Hydrocarbon (HC), hydrogen (H)2) The reducing components are more, and the reducing components can convert NOx in the surface adsorption state of the LNT catalyst into nitrogen (N) under the catalysis of the main active component of the LNT catalyst2) Water (H)2O) and the like, and realizes the purification of NOx, and at the same time, the BaO adsorbent recovers the adsorption capacity of gaseous NOx after releasing adsorbed NOx, that is, realizes the regeneration of the BaO adsorbent. However, the complete adoption of Pt as the main active component leads to high cost, poor sulfur resistance and poor heat resistance of the catalyst, so that the substitution of noble metal becomes one of the core contents in the research and development work of the novel LNT catalyst. However, the coating performance of the BaO adsorbent is poor, and the coating stability is deteriorated when the mass ratio of BaO in the LNT catalyst exceeds 20%, so that the addition amount of BaO in the LNT catalyst needs to be strictly limited, thereby causing that the NOx adsorption performance of the conventional LNT catalyst is difficult to be improved. Al (Al)2O3The coating is a coating base material in the LNT catalyst and can provide a working surface with large specific surface area and high stability for main active components, adsorbents and the like. However, Al2O3The LNT has poor catalytic activity and NOx adsorption performance, and is easy to generate phase change at high temperature or react with BaO adsorbent to generate BaAl with spinel structure2O4Resulting in loss of NOx storage active sites. Therefore, the development of a coated base material with additional adsorbent functionality is also an important part of the development work of new LNT catalysts.
The perovskite type composite oxide is a high-efficiency oxidation-reduction reaction catalyst and is commercially applied to the field of purification of pollutants in tail gas of internal combustion engines for vehicles. The material is often ABO3It shows that the cations with larger A site and smaller B site combine with a specific amount of oxygen ions to form a cubic crystal structure, and the A, B site elements are common metal elements, so the raw material cost is far lower than that of noble metal materials. Currently, lanthanum manganate (LaMnO)3) Is one of the most common perovskite materials, and the proper metal elements are adopted to respectively partially replace the A-site La element and the B-site Mn element, so that the overall physical-chemical characteristics of the perovskite material can be modulated, and specific performance indexes are optimized. In addition, earlier studies have shown that the addition of a small amount of precious metal material to the perovskite material can significantly improve the catalytic activity of the perovskite material for oxidation-reduction reactions.
The derived composite oxide (Al) is obtained by high-temperature roasting of aluminum (Al) -magnesium (Mg) hydrotalcite compounds2O36MgO) with high specific surface area, strong alkalinity, unit NOx saturated adsorption amount close to BaO and excellent coating performance, and the catalyst coating prepared by taking the catalyst coating as the coating base material has the performance close to Al2O3Specific surface area and mechanical strength of the base coating, and Al can be replaced in any proportion in the coating of the LNT catalyst2O3. The hydrotalcite-derived composite oxide material is used as a coating base material in the novel LNT catalyst, so that an additional adsorbent can be provided for the LNT catalyst, the overall NOx adsorption performance of the LNT catalyst is improved, and the using amount of a BaO adsorbent can be reduced. In addition, Bi and Ni elements are respectively used for partially replacing Al and Mg elements in the hydrotalcite derived composite oxide, and the NOx adsorption performance of the hydrotalcite derived composite oxide can be further improved through the synergistic effect among a plurality of metal elements.
The traditional LNT catalyst adopts a method of coating the same coating slurry for multiple times to prepare a catalytic coating, the method has simple process, but the LNT catalyst has different functions of coatings with different depths, and the treated exhaust components are different, so that the uniform coating can cause insufficient distribution of functional components at certain depths, and the functional components at certain depths are excessive. Therefore, the research and development of the non-uniform coating aiming at the catalytic reaction characteristic is beneficial to improving the catalytic effect and saving the using amount of functional components.
Disclosure of Invention
By combining the prior art, the invention designs two catalytic coatings with different compositions aiming at the action characteristics of functional components such as a main active component of noble metal, a base material of a modified hydrotalcite derived composite oxide coating and the like, thereby realizing the performance optimization of the high-performance LNT catalyst. The invention provides a La-La vehicle suitable for diesel vehiclexSr(1-x)MnyCo(1-y)O3The perovskite composite oxide replaces most of noble metals, and the Bi-Ni bimetal modified hydrotalcite derivative composite oxide replaces most of gamma-Al2O3And a novel LNT catalyst using a non-uniform dual catalytic coating and a method for preparing the same.
In order to solve the technical problems, the invention provides a double-coating catalyst for a diesel engine based on hydrotalcite derived oxide, which comprises two catalytic coatings coated on a catalyst carrier in sequence, wherein the catalytic coating coated on the catalyst carrier is an inner catalytic coating, and the catalytic coating coated on the inner catalytic coating and having a component composition different from that of the inner catalytic coating is an outer catalytic coating; the catalyst carrier is 400-mesh cordierite honeycomb ceramic;
the outer catalytic coating comprises Pt and LaxSr(1-x)MnyCo(1-y)O3Perovskite composite oxide, BaO, CeO2-ZrO2Solid solution, Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3；
The inner catalytic coating comprises LaxSr(1-x)MnyCo(1-y)O3Perovskite composite oxide, BaO, CeO2-ZrO2Solid solution, Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3And SiO2；
The LaxSr(1-x)MnyCo(1-y)O3A perovskite composite oxide, wherein x represents the molar percentage of La in the sum of the molar numbers of Sr and La ions, and x is 25-75%; y represents the molar percentage of Mn in the sum of the molar numbers of Co and Mn ions, and y is 25-50%; at the same time, the user can select the desired position,the LaxSr(1-x)MnyCo(1-y)O3The ratio of the sum of the number of moles of La ions and Sr ions to the sum of the number of moles of Mn ions and Co ions in the perovskite-type composite oxide is 1: 1;
the Bi-Ni bimetal modified hydrotalcite derived composite oxide is prepared by partially replacing Al with Bi2O3Partially substituting Al with Ni in 6MgO type hydrotalcite-like compound-derived composite oxide2O36MgO type hydrotalcite-like compound derived composite oxide containing Mg, wherein Bi, Al, Ni and Mg are each Bi2O3、Al2O3NiO and MgO are dispersed in the Bi-Ni bimetal modified hydrotalcite derived composite oxide, and Bi2O3And Al2O3The mole percentage of (A) is as follows: 50-80%/50-20%, the sum of the mole percentages is 100%; the mol percentages of NiO and MgO are as follows: 25-75%/75-25%, the sum of the mole percentages being 100%; and the ratio of the sum of the molar numbers of Bi ions and Al ions to the sum of the molar numbers of Ni ions and Mg ions in the Bi-Ni bimetal modified hydrotalcite derived composite oxide is as follows: 1: 3;
in the outer catalytic coating, Pt and LaxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide forms the main active component of the outer catalytic coating, and Pt and LaxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide comprises the following components in percentage by mass: 2-5%/98-95%, the sum of the mass percentages is 100%; an adsorbent with external catalytic coating composed of BaO and CeO2-ZrO2Solid solution forms an outer catalytic coating cocatalyst; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3The Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al form an outer catalytic coating base material2O3The mass percentage of the components is as follows: 90%/10%; the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating jointly form the outer catalytic coating of the catalyst, wherein the outer catalytic coatingThe mass percentages of the main active component of the chemical coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating respectively correspond to: 10-15%/10%/5-10%/75-65%, the sum of the mass percentages is 100%;
in the internal catalytic coating, LaxSr(1-x)MnyCo(1-y)O3The main active component of the inner catalytic coating is composed of perovskite composite oxide; an adsorbent with internal catalytic coating composed of BaO and CeO2-ZrO2Solid solution is used for forming an inner catalytic coating cocatalyst; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3And SiO2The Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al are used as the base material of the internal catalytic coating2O3And SiO2The mass percentage of the components is as follows: 80-85%/10%/10-5%, the sum of the mass percentages is 100%; the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating jointly form the inner catalytic coating of the catalyst, wherein the mass percentages of the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating respectively correspond to: 5-10%/10%/5-10%/80-70%, the sum of the mass percentages being 100%.
Further, the diesel engine double-coating catalyst based on hydrotalcite derived oxide of the invention, wherein, the CeO2-ZrO2CeO in solid solution2And ZrO2The mass percentage of the components is as follows: 80%/20%.
The gamma-Al2O3Generated by the conversion of aluminum sol as a coating binder; the SiO2Is formed by the conversion of silica gel as a coating binder.
The mass percentages of the outer catalytic coating, the inner catalytic coating and the catalyst carrier are as follows: 4-8%/12-18%/84-74%, and the sum of the mass percentages is 100%.
The preparation method of the diesel engine double-coating catalyst based on the hydrotalcite derived oxide comprises the following steps:
step one, designing a catalyst composition:
respectively designing: the LaxSr(1-x)MnyCo(1-y)O3The mol percentage of La ions and Sr ions and the mol percentage of Mn ions and Co ions in the perovskite composite oxide; in the Bi-Ni bimetal modified hydrotalcite derived composite oxide, Bi2O3And Al2O3The mole percent of NiO and the mole percent of MgO; pt and La in main active components of the outer catalytic coatingxSr(1-x)MnyCo(1-y)O3Mass percent of the perovskite-type composite oxide; the mass percentages of the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al in the outer catalytic coating base material2O3The mass percentage of (A); the mass percentages of the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating are as follows; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al in the base material of the internal catalytic coating2O3And SiO2The mass percentage of (A); the mass percentage ranges of the outer catalytic coating, the inner catalytic coating and the catalyst carrier are as follows; the quality of the external catalytic coating prepared by the external catalytic coating slurry and the quality of the internal catalytic coating prepared by the internal catalytic coating slurry can be respectively prepared;
step two, LaxSr(1-x)MnyCo(1-y)O3Preparation of perovskite composite oxide
Calculating the La required for preparing the inner catalytic coating and the outer catalytic coating according to the proportion of each component designed in the step onexSr(1-x)MnyCo(1-y)O3The total mole number of the perovskite composite oxide and the mole number of La, Sr, Mn and Co ions in the perovskite composite oxide are 433.0g [ La (NO)3)3·6H2O]Preparation of 1mol of La ion, 211.6g of [ Sr (NO)3)2]Preparation of 1molSr ion, 245.1g [ Mn (CH)3COO)2·4H2O]Preparation of 1mol of Mn ion, 291.1g of [ Co (NO)3)2·6H2O]Preparing the reduced proportion of 1mol of Co ions, the total mole number of the four raw materials and C6H12O6Is a ratio of 1:1 and C6H12O6Molecular weight is 180.2, calculated to prepare LaxSr(1-x)MnyCo(1-y)O3La (NO) required for perovskite composite oxide3)3·6H2O、Sr(NO3)2、Mn(CH3COO)2·4H2O、Co(NO3)2·6H2O、C6H12O6The quality of the five raw materials; mixing the La (NO) mentioned above3)3·6H2O、Sr(NO3)2、Mn(CH3COO)2·4H2O、Co(NO3)2·6H2O、C6H12O6Adding five raw materials into deionized water according to the proportion that each mole of metal ions is dissolved in 0.75-1L of deionized water to prepare a solution; evaporating the solution on a rotary evaporator at 60-80 ℃ until the solution is converted into a honey-like wet gel; drying the wet gel at 80-110 ℃ for 6-12 h to obtain fluffy, fragile and faint yellow dry gel; heating the xerogel to 400 ℃ at the speed of 3 ℃/min in a muffle furnace, keeping for 2h, heating to 800 ℃ at the speed of 10 ℃/min, and roasting for 3h to obtain LaxSr(1-x)MnyCo(1-y)O3A perovskite-type composite oxide;
step three, preparing Bi-Ni bimetal modified hydrotalcite derived composite oxide:
calculating the total mass of Bi-Ni bimetal modified hydrotalcite derived composite oxide required by preparing the inner catalytic coating and the outer catalytic coating and Bi in the Bi-Ni bimetal modified hydrotalcite derived composite oxide according to the proportion of each component designed in the step one2O3、Al2O3The molar number of NiO and MgO, and 970.1g of [ Bi (NO)3)3·5H2O]Preparation of 1mol of Bi2O3、750.2g[Al(NO3)3·9H2O]Preparation of 1mol of Al2O3、290.8g[Ni(NO3)2·6H2O]Preparation of 1mol NiO, 256.4g [ Mg (NO)3)2·6H2O]The conversion ratio of 1mol of MgO is prepared, and Bi (NO) required for preparing the Bi-Ni bimetal modified hydrotalcite derivative composite oxide is calculated3)3·5H2O、Al(NO3)3·9H2O、Ni(NO3)2·6H2O、Mg(NO3)2·6H2O, the mass of the four raw materials; weighing the Bi (NO) according to the determined mass3)3·5H2O、Al(NO3)3·9H2O、Ni(NO3)2·6H2O、Mg(NO3)2·6H2Adding the four raw materials into deionized water weighed according to the proportion that each mole of Ni ions and each mole of Mg ions correspond to 0.5-1L of deionized water, and stirring to prepare a solution, namely a precursor solution; weighing sufficient NaOH and Na2CO3And the mole number of NaOH is equal to that of Na2CO3The molar ratio of the NaOH to the Na is 2:1, and then the NaOH and the Na are mixed according to the ratio that each mole of NaOH corresponds to 1L of deionized water2CO3Adding into deionized water, stirring thoroughly until NaOH and Na2CO3Completely dissolving to obtain a buffer solution; adding a buffer solution into the precursor solution at a speed of 30-50 ml/min, stirring vigorously, and simultaneously, continuously measuring the pH value of the precursor solution in which the buffer solution is added by using a pH value analyzer; stopping adding the buffer solution when the pH value is between 9.5 and 10.5, continuously stirring for 2 to 4 hours, standing and aging for 24 to 48 hours, performing suction filtration to separate out solid substances in the aged solution, washing the solid substances with deionized water for 3 to 5 times, drying at 90 to 110 ℃ for 8 to 16 hours, roasting at 500 to 600 ℃ for 2 to 4 hours, naturally cooling, and grinding the solid substances on a ball mill for 1 hour to obtain the Bi-Ni bimetal modified hydrotalcite derived composite oxide;
step four, preparing and coating the inner catalytic coating:
calculating the internal catalysis according to the proportion of each component designed in the step oneLa required for coating preparationxSr(1-x)MnyCo(1-y)O3Perovskite composite oxide, BaO, CeO2、ZrO2Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3、SiO2The mass of (c); binding 255.4g [ Ba (CH)3COO)2]Preparation of 153.3g of BaO, 434.1g of [ Ce (NO)3)3·6H2O]Preparation of 172.1g of CeO2、429.3g[Zr(NO3)4·5H2O]Preparation of 123.2g ZrO2Calculating the conversion ratio of Ba (CH) required by preparing the internal catalytic coating3COO)2、Ce(NO3)3·6H2O、Zr(NO3)4·5H2The mass of O; according to Al in the alumina sol2O3And SiO in silica gel2Respectively calculating the mass of the consumed aluminum sol and the mass of the consumed silica gel required by the preparation of the inner catalytic coating; in addition, the mass of the polyethylene glycol and the nitric acid consumed for preparing the inner catalytic coating is calculated according to the proportion that every 100g of the inner catalytic coating needs 5-15 g of polyethylene glycol with the average molecular weight of 20000 and 25-50 g of nitric acid; weighing Ba (CH) according to the determined mass3COO)2、Ce(NO3)3·6H2O、Zr(NO3)4·5H2O, alumina sol, silica gel, polyethylene glycol with average molecular weight of 20000, nitric acid and LaxSr(1-x)MnyCo(1-y)O3Adding all the raw materials into deionized water with the mass being 10-15 times of the total mass of the prepared inner catalytic coating, and fully stirring to form uniform suspension; grinding the suspension on a wet grinding machine until the median particle size is within the range of 1.0-1.2 microns, and then stirring the ground suspension for 16-24 hours at the temperature of 60-80 ℃ to obtain internal catalytic coating slurry; the mass percentages of the inner catalytic coating, the outer catalytic coating and the catalyst carrier are as follows: 4-8%/12-18%/84-74%, and the sum of the mass percentages is 100%; mixing the inner catalytic coating with 400-mesh cordierite honeycomb ceramic, and mixingThe following impregnation, drying and calcination treatments were carried out: weighing a 400-mesh cordierite honeycomb ceramic carrier with determined mass, immersing the ceramic carrier in the slurry of the internal catalytic coating at the temperature of 60-80 ℃, taking out the carrier from the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying at the temperature of 90-110 ℃ for 6-12 h, and roasting at the temperature of 500-600 ℃ for 2-4 h; repeating the processes of dipping, drying and roasting for 2 times to finish the coating of the inner catalytic coating;
step five, preparing and coating an outer catalytic coating:
calculating the Pt and La required by the preparation of the outer catalytic coating according to the proportion of each component designed in the step onexSr(1-x)MnyCo(1-y)O3Perovskite composite oxide, BaO, CeO2、ZrO2Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3The mass of (c); in combination with 517.9g [ H ]2PtCl6·6H2O]Preparation of 195.1g Pt, 255.4g Ba (CH)3COO)2Preparation of 153.3g of BaO, 434.1g of Ce (NO)3)3·6H2O preparation of 172.1g CeO2、429.3g Zr(NO3)4·5H2O preparation 123.2g ZrO2Calculating the H required by preparing the outer catalytic coating according to the conversion ratio2PtCl6·6H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、Zr(NO3)4·5H2The mass of O; according to Al in the alumina sol2O3Calculating the mass of the consumed aluminum sol required for preparing the outer catalytic coating according to the mass percentage; in addition, the mass of the polyethylene glycol and the nitric acid consumed for preparing the outer catalytic coating is calculated according to the proportion that every 100g of the outer catalytic coating needs 5-15 g of polyethylene glycol with the average molecular weight of 20000 and 25-50 g of nitric acid; weighing the outer catalytic coating preparation according to the determined mass for preparing H2PtCl6·6H2O、Ba(CH3COO)2、Ce(NO3)3·6H2O、Zr(NO3)4·5H2O, alumina sol, average molecular weight 20000 polyethylene glycol, nitric acid and LaxSr(1-x)MnyCo(1-y)O3Adding all the raw materials into deionized water with the mass being 10-15 times of the total mass of the prepared outer catalytic coating, and fully stirring to form uniform suspension; grinding the suspension on a wet grinding machine until the median particle size is within the range of 1.0-1.2 microns, and then stirring the ground suspension for 16-24 hours at the temperature of 60-80 ℃ to obtain outer catalytic coating slurry; immersing the 400-mesh cordierite honeycomb ceramic carrier coated with the inner catalytic coating in the fifth step into slurry of the outer catalytic coating at the temperature of 60-80 ℃, taking the carrier out of the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying at the temperature of 90-110 ℃ for 6-12 h, and roasting at the temperature of 500-600 ℃ for 2-4 h; namely, the coating of the outer catalytic coating is finished, and finally the diesel engine double-coating catalyst based on the hydrotalcite derived oxide is obtained.
The double-coating catalyst of the diesel engine based on the hydrotalcite derived oxide prepared by the preparation method is packaged, the packaged catalyst is arranged in an exhaust passage of the diesel engine, and NOx pollutants in exhaust gas of the diesel engine are purified through NOx adsorption-reduction reaction.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, most of noble metals in the traditional LNT catalyst are replaced by the substituted perovskite composite oxide, so that the sulfur resistance and the thermal stability of the novel LNT catalyst are improved while the raw material cost is reduced. Meanwhile, the modified hydrotalcite-derived composite oxide is used for replacing most of Al in the traditional LNT catalyst2O3The NOx adsorption capacity of the LNT catalyst is significantly improved. And the substitution of Bi element for Al element and Ni element for Mg element in the modified hydrotalcite-derived composite oxide optimizes the NOx adsorption performance of the hydrotalcite-derived composite oxide, and particularly has obvious effect of improving the low-temperature NOx adsorption performance. In addition, the LNT catalyst adopts a non-uniform double-coating preparation method, optimizes the distribution characteristics of functional materials, and thenThe cost of the novel LNT catalyst raw material is reduced step by step, and the NOx purification effect, durability and reliability of the catalyst are improved.
Drawings
Fig. 1 is a schematic diagram of an engine evaluation system for NOx purification performance of an LNT catalyst.
Wherein: 1-a dynamometer; 2-a coupler; 3-test diesel engine; 4-an intake air flow meter; 5-air intake air conditioning; 6-oil injector; 7-a fuel injection control system; 8-exhaust sampling port A; 9-temperature sensor a; 10-exhaust manostat; 11-temperature sensor B; 12-LNT catalyst; 13-temperature sensor C; 14-exhaust sample port B; 15-exhaust sampling channel; 16-engine exhaust gas analyzer; 17-air pump.
FIG. 2 shows an engine evaluation system for NOx purification performance of the LNT catalyst under a lean-burn condition of a diesel engine with an exhaust temperature of 250 ℃ and an airspeed of 30000h-1Under the steady-state working condition, the purification efficiency of NOx in the adsorption-reduction reaction of the NOx exhausted by the diesel engine under the catalysis of the catalyst prepared in the embodiment 1-3 is improved.
FIG. 3 shows an engine evaluation system for NOx purification performance of the LNT catalyst under a lean-burn condition of a diesel engine with an exhaust temperature of 350 ℃ and an airspeed of 50000h-1Under the steady-state working condition, the purification efficiency of NOx in the adsorption-reduction reaction of the NOx exhausted by the diesel engine under the catalysis of the catalyst prepared in the embodiment 1-3 is improved.
Fig. 4 shows NOx purification efficiency in the adsorption-reduction reaction of NOx in the exhaust gas of the diesel engine catalyzed by the catalysts prepared in examples 1 to 3 in the European steady state cycle (ESC) test using the LNT catalyst NOx purification performance engine evaluation system.
Detailed Description
The invention relates to a diesel engine double-coating catalyst based on hydrotalcite derived oxide, which comprises two catalytic coatings coated on a catalyst carrier in sequence, wherein the catalytic coating coated on the catalyst carrier is an inner catalytic coating, and the catalytic coating which is coated on the inner catalytic coating and has different component composition from the inner catalytic coating is an outer catalytic coating; the catalyst support was 400 mesh cordierite honeycomb ceramic. The outer catalytic coating comprises Pt and LaxSr(1-x)MnyCo(1-y)O3Perovskite composite oxide, BaO, CeO2-ZrO2Solid solution, Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3(ii) a The inner catalytic coating comprises LaxSr(1-x)MnyCo(1-y)O3Perovskite composite oxide, BaO, CeO2-ZrO2Solid solution, Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3And SiO2。
(1) The LaxSr(1-x)MnyCo(1-y)O3A perovskite composite oxide, wherein x represents the molar percentage of La in the sum of the molar numbers of Sr and La ions, and x is 25-75%; y represents the molar percentage of Mn in the sum of the molar numbers of Co and Mn ions, and y is 25-50%; meanwhile, the LaxSr(1-x)MnyCo(1-y)O3The ratio of the sum of the number of moles of La ions and Sr ions to the sum of the number of moles of Mn ions and Co ions in the perovskite-type composite oxide is 1: 1.
(2) The Bi-Ni bimetal modified hydrotalcite derived composite oxide is prepared by partially replacing Al with Bi2O3Partially substituting Al with Ni in 6MgO type hydrotalcite-like compound-derived composite oxide2O36MgO type hydrotalcite-like compound derived composite oxide containing Mg, wherein Bi, Al, Ni and Mg are each Bi2O3、Al2O3NiO and MgO are dispersed in the Bi-Ni bimetal modified hydrotalcite derived composite oxide, and Bi2O3And Al2O3The mole percentage of (A) is as follows: 50-80%/50-20%, the sum of the mole percentages is 100%; the mol percentages of NiO and MgO are as follows: 25-75%/75-25%, the sum of the mole percentages being 100%; and the ratio of the sum of the molar numbers of Bi ions and Al ions to the sum of the molar numbers of Ni ions and Mg ions in the Bi-Ni bimetal modified hydrotalcite derived composite oxide is as follows: 1: 3;
(3) from noble metal Pt and said LaxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide forms the main active component of the outer catalytic coating, and Pt and the LaxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide comprises the following components in percentage by mass: 2-5%/98-95%, and the sum of the mass percentages is 100%. An adsorbent with external catalytic coating composed of BaO and CeO2-ZrO2The solid solution constitutes the outer catalytic coating cocatalyst. Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3The Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al form an outer catalytic coating base material2O3The mass percentage of the components is as follows: 90%/10%. The main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating jointly form the outer catalytic coating of the catalyst, wherein the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating respectively correspond to the following components in percentage by mass: 10-15%/10%/5-10%/75-65%, the sum of the mass percentages is 100%.
(4) From LaxSr(1-x)MnyCo(1-y)O3The main active component of the inner catalytic coating is composed of perovskite composite oxide, the adsorbent of the inner catalytic coating is composed of BaO and CeO2-ZrO2The solid solution constitutes the promoter of the inner catalytic coating. Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3And SiO2The Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al are used as the base material of the internal catalytic coating2O3And SiO2The mass percentage of the components is as follows: 80-85%/10%/10-5%, and the sum of the mass percentages is 100%. The main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating jointly form the inner catalytic coating of the catalyst, wherein the mass of the main catalyst of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating is hundreds ofThe ratio of the ratio is respectively as follows: 5-10%/10%/5-10%/80-70%, the sum of the mass percentages being 100%.
(5) The CeO2-ZrO2CeO in solid solution2And ZrO2The mass percentage of the components is as follows: 80%/20%.
(6) The gamma-Al2O3Generated by the conversion of aluminum sol as a coating binder; the SiO2Is formed by the conversion of silica gel as a coating binder.
(7) The catalyst comprises the inner catalytic coating, the outer catalytic coating and 400-mesh cordierite honeycomb ceramic, wherein the 400-mesh cordierite honeycomb ceramic is a carrier of the catalyst, the inner catalytic coating and the outer catalytic coating are coated on the 400-mesh cordierite honeycomb ceramic carrier, and the outer catalytic coating, the inner catalytic coating and the 400-mesh cordierite honeycomb ceramic carrier comprise the following components in percentage by mass: 4-8%/12-18%/84-74%, and the sum of the mass percentages is 100%.
The preparation method of the diesel engine double-coating catalyst based on the hydrotalcite derived oxide comprises the following 5 steps: (1) designing the composition of a catalyst; (2) laxSr(1-x)MnyCo(1-y)O3Preparing perovskite composite oxide; (3) preparing Bi-Ni bimetal modified hydrotalcite derived composite oxide; (4) preparing and coating an inner catalytic coating; (5) preparing and coating an outer catalytic coating.
The technical solution of the present invention is further described below by specific examples in conjunction with the accompanying drawings. It should be noted that the present embodiments are illustrative and not restrictive, and the present invention is not limited to the following embodiments.
The double-coating catalyst for diesel engine based on hydrotalcite derived oxide comprises two catalytic coatings, wherein the catalytic coating directly coated on 400-mesh cordierite honeycomb ceramic carrier is an inner catalytic coating, and the catalytic coating which is coated on the inner catalytic coating and has different component composition from the inner catalytic coating is an outer catalytic coating. The outer catalytic coating comprises noble metals Pt and LaxSr(1-x)MnyCo(1-y)O3Perovskite composite oxide, BaO, CeO2-ZrO2Solid solution, Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3(ii) a The inner catalytic coating comprises LaxSr(1-x)MnyCo(1-y)O3Perovskite composite oxide, BaO, CeO2-ZrO2Solid solution, Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3、SiO2(ii) a The catalyst of the present invention also includes a 400 mesh cordierite honeycomb ceramic support.
From noble metals Pt and LaxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide forms the main active component of the outer catalytic coating, and Pt and LaxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide comprises the following components in percentage by mass: 2-5%/98-95%, and the sum of the mass percentages is 100%. An adsorbent with external catalytic coating composed of BaO and CeO2-ZrO2The solid solution constitutes the outer catalytic coating cocatalyst. Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3The Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al form an outer catalytic coating base material2O3The mass percentage of the components is as follows: 90%/10%. The main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating jointly form the outer catalytic coating of the catalyst, wherein the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating respectively correspond to the following components in percentage by mass: 10-15%/10%/5-10%/75-65%, the sum of the mass percentages is 100%.
From LaxSr(1-x)MnyCo(1-y)O3The main active component of the inner catalytic coating is composed of perovskite composite oxide, the adsorbent of the inner catalytic coating is composed of BaO and CeO2-ZrO2The solid solution constitutes the promoter of the inner catalytic coating. Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3And SiO2The Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al are used as the base material of the internal catalytic coating2O3And SiO2The mass percentage of the components is as follows: 80-85%/10%/10-5%, and the sum of the mass percentages is 100%. The main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating jointly form the inner catalytic coating of the catalyst, wherein the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating respectively correspond to the following components in percentage by mass: 5-10%/10%/5-10%/80-70%, the sum of the mass percentages being 100%.
The LaxSr(1-x)MnyCo(1-y)O3The molar percentage of La ions to Sr ions in the perovskite composite oxide is as follows: 25-75%/75-25%, the sum of the mole percentages being 100%; the molar percentage of Mn ions to Co ions is: 25-50%/75-50%, the sum of the mole percentages being 100%; meanwhile, the LaxSr(1-x)MnyCo(1-y)O3The ratio of the sum of the number of moles of La ions and Sr ions to the sum of the number of moles of Mn ions and Co ions in the perovskite-type composite oxide is: 1:1.
The CeO2-ZrO2CeO in solid solution2And ZrO2The mass percentage of the components is as follows: 80%/20%.
Bi, Al, Ni and Mg in the Bi-Ni bimetal modified hydrotalcite derived composite oxide are respectively Bi2O3、Al2O3NiO and MgO are dispersed in the Bi-Ni bimetal modified hydrotalcite derived composite oxide, and Bi2O3And Al2O3The mole percentage of (A) is as follows: 50-80%/50-20%, the sum of the mole percentages is 100%; the mol percentages of NiO and MgO are as follows: 25-75%/75-25%, the sum of the mole percentages being 100%; and the sum of the molar numbers of Bi ions and Al ions and the sum of the molar numbers of Ni ions and Mg ions in the Bi-Ni bimetal modified hydrotalcite derived composite oxideThe proportion of (A) is as follows: 1:3.
The gamma-Al2O3Generated by the conversion of aluminum sol as a coating binder; the SiO2Is formed by the conversion of silica gel as a coating binder.
The catalyst comprises the inner catalytic coating, the outer catalytic coating and 400-mesh cordierite honeycomb ceramic, wherein the 400-mesh cordierite honeycomb ceramic is a carrier of the catalyst, the inner catalytic coating and the outer catalytic coating are coated on the 400-mesh cordierite honeycomb ceramic carrier, and the outer catalytic coating, the inner catalytic coating and the 400-mesh cordierite honeycomb ceramic carrier comprise the following components in percentage by mass: 4-8%/12-18%/84-74%, and the sum of the mass percentages is 100%.
The method for preparing the catalyst of the present invention is described in detail below with reference to specific examples.
Example 1
(1) Catalyst composition design
Respectively designing Pt and La in main active components of the outer catalytic coatingxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide comprises the following components in percentage by mass: 2%/98%; the mass percentages of the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating are as follows: 15%/10%/10%/65%; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al in base material of inner catalytic coating2O3And SiO2The mass percentage of the components is as follows: 85%/10%/5%; the mass percentages of the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating are as follows: 10%/10%/10%/70%; laxSr(1-x)MnyCo(1-y)O3The molar percentage of La ions to Sr ions in the perovskite composite oxide is as follows: 75%/25%, and the molar percentage of Mn ions to Co ions is: 50%/50%; in the Bi-Ni bimetal modified hydrotalcite derived composite oxide, Bi2O3And Al2O3The mole percentage of (A) is as follows: 80%/20% and the molar percentage of NiO and MgO are as follows:25%/75%. The mass percentage ranges of the outer catalytic coating, the inner catalytic coating and the 400-mesh cordierite honeycomb ceramic carrier are as follows: 7-8%/17-18%/76-74%. The prepared outer catalytic coating slurry can prepare 2000g of outer catalytic coating and the prepared inner catalytic coating slurry can prepare 2000g of inner catalytic coating.
(2)LaxSr(1-x)MnyCo(1-y)O3Preparation of perovskite composite oxide
Weighing 694.6g La (NO)3)3·6H2O、113.2g Sr(NO3)2、262.1g Mn(CH3COO)2·4H2O、311.3g Co(NO3)2·6H2O and 770.9g C6H12O6And adding the 5 raw materials into 4L of deionized water together to prepare a solution. The solution was evaporated on a rotary evaporator at 80 ℃ until the solution turned into a honey-like wet gel, which was dried at 110 ℃ for 6h to give a pale yellow xerogel. Heating the xerogel to 400 ℃ at the speed of 3 ℃/min in a muffle furnace, keeping for 2h, heating to 800 ℃ at the speed of 10 ℃/min, and roasting for 3h to obtain LaxSr(1-x)MnyCo(1-y)O3A perovskite-type composite oxide.
(3) Preparation of Bi-Ni bimetal modified hydrotalcite derived composite oxide
2667.4g Bi (NO) were weighed out3)3·5H2O、515.7g Al(NO3)3·9H2O、1499.2g Ni(NO3)2·6H2O、3965.6g Mg(NO3)2·6H2And O, adding the 4 raw materials into 12L of deionized water, and stirring to prepare a solution, namely a precursor solution. 200g NaOH and 265g Na were weighed out2CO3Adding the two raw materials into 5L of deionized water, and fully stirring until NaOH and Na are obtained2CO3Completely dissolved as buffer. Then adding the buffer solution into the precursor solution at the speed of 50ml/min, stirring vigorously, and simultaneously, continuously measuring the pH value of the precursor solution in which the buffer solution is being added by using a pH value analyzer; the pH value of the precursor liquidStopping adding the buffer solution when the temperature is between 9.5 and 10.5, and continuously stirring the precursor solution for 2 hours; and standing and aging the stirred precursor liquid for 24 hours, wherein a large amount of solid substances are generated in an aged precursor liquid container. Solid substances in the precursor liquid container are separated through suction filtration, and then the solid substances are washed for 3 times by deionized water; and drying the washed solid substance at 110 ℃ for 8h, roasting the dried solid substance at 600 ℃ for 2h, naturally cooling the roasted solid substance, and grinding the solid substance on a ball mill for 1h to obtain the Bi-Ni bimetal modified hydrotalcite derivative composite oxide.
(4) Preparation of internal catalytic coating and its application
Al in the Aluminosol used in example 12O310.8 percent of SiO in the silica gel2The mass percentage of (B) is 25%. Weighing 200g of LaxSr(1-x)MnyCo(1-y)O3Perovskite-type composite oxide, 333.2g Ba (CH)3COO)2、403.6g Ce(NO3)3·6H2O、139.4g Zr(NO3)4·5H2O, 1190g of Bi-Ni bimetal modified hydrotalcite derived composite oxide, 1296.3g of aluminum sol, 280g of silica gel, 300g of polyethylene glycol with the average molecular weight of 20000 and 500g of nitric acid, and all the raw materials are added into 20000g of deionized water and fully stirred to form a uniform suspension. And grinding the suspension on a wet grinding machine until the median particle size (D50 particle size) is within the range of 1.0-1.2 microns, and then stirring the ground suspension for 16 hours at 80 ℃ to obtain the internal catalytic coating slurry. Weighing 1000g of 400-mesh cordierite honeycomb ceramic carrier, immersing the carrier in the slurry of the internal catalytic coating at 80 ℃, taking the carrier out of the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying at 110 ℃ for 6h, and then roasting at 600 ℃ for 2 h. Repeating the processes of dipping, drying and roasting for 2 times to finish the preparation of the inner catalytic coating.
(5) Preparation and application of outer catalytic coating
Weighing 15.9g H2PtCl6·6H2O、294g LaxSr(1-x)MnyCo(1-y)O3Perovskite-type composite oxide, 333.2g Ba (CH)3COO)2、403.6g Ce(NO3)3·6H2O、139.4g Zr(NO3)4·5H2O, 1170g of Bi-Ni bimetal modified hydrotalcite derived composite oxide, 1203.7g of alumina sol, 300g of polyethylene glycol with the average molecular weight of 20000 and 1000g of nitric acid, and all the raw materials are added into 20000g of deionized water and fully stirred to form a uniform suspension. And grinding the suspension on a wet grinding machine until the particle size of D50 is within the range of 1.0-1.2 microns, and stirring the ground suspension for 16 hours at 80 ℃ to obtain the external catalytic coating slurry. And immersing the 400-mesh cordierite honeycomb ceramic carrier coated with the inner catalytic coating into the slurry of the outer catalytic coating at the temperature of 80 ℃, taking the carrier out of the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying for 6h at the temperature of 110 ℃, and roasting for 2h at the temperature of 600 ℃, thus finishing the preparation and coating of the outer catalytic coating.
Example 2
(1) Catalyst composition design
Respectively designing Pt and La in main active components of the outer catalytic coatingxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide comprises the following components in percentage by mass: 5%/95%; the mass percentages of the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating are as follows: 10%/10%/5%/75%. Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al in base material of inner catalytic coating2O3And SiO2The mass percentage of the components is as follows: 80%/10%/10%; the mass percentages of the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating are as follows: 5%/10%/5%/80%. LaxSr(1-x)MnyCo(1-y)O3The molar percentage of La ions to Sr ions in the perovskite composite oxide is as follows: 25%/75%, the molar percentage of Mn ions to Co ions is:25%/75%. In the Bi-Ni bimetal modified hydrotalcite derived composite oxide, Bi2O3And Al2O3The mole percentage of (A) is as follows: 50%/50% and the molar percentages of NiO and MgO are as follows: 75%/25%. The mass percentage ranges of the outer catalytic coating, the inner catalytic coating and the 400-mesh cordierite honeycomb ceramic carrier are as follows: 4-5%/17-18%/79-77%. The prepared outer catalytic coating slurry can prepare 2000g of outer catalytic coating and the prepared inner catalytic coating slurry can prepare 2000g of inner catalytic coating.
(2)LaxSr(1-x)MnyCo(1-y)O3Preparation of perovskite composite oxide
152.2g La (NO) are weighed out3)3·6H2O、223.1g Sr(NO3)2、86.2g Mn(CH3COO)2·4H2O、307.0g Co(NO3)2·6H2O and 506.7g C6H12O6The 5 raw materials are added into 2.5L of deionized water together to prepare a solution. The solution was evaporated on a rotary evaporator at 60 ℃ until the solution turned into a honey-like wet gel, which was then dried at 80 ℃ for 12h to give a pale yellow xerogel. Heating the xerogel to 400 ℃ at the speed of 3 ℃/min in a muffle furnace, keeping for 2h, heating to 800 ℃ at the speed of 10 ℃/min, and roasting for 3h to obtain LaxSr(1-x)MnyCo(1-y)O3A perovskite-type composite oxide.
(3) Preparation of Bi-Ni bimetal modified hydrotalcite derived composite oxide
1874.2g Bi (NO) were weighed out3)3·5H2O、1449.4g Al(NO3)3·9H2O、5056.4g Ni(NO3)2·6H2O、1486.1g Mg(NO3)2·6H2And O, adding the 4 raw materials into 15L of deionized water, and stirring to prepare a solution, namely a precursor solution. 200g NaOH and 265g Na were weighed out2CO3Adding the two raw materials into 5L of deionized water, and fully stirring until NaOH and Na are obtained2CO3Is totally produced fromThe solution was buffered. Then adding the buffer solution into the precursor solution at the speed of 30ml/min, stirring vigorously, and simultaneously, continuously measuring the pH value of the precursor solution in which the buffer solution is being added by using a pH value analyzer; stopping adding the buffer solution when the pH value of the precursor solution is between 9.5 and 10.5, and continuously stirring the precursor solution for 4 hours; and standing and aging the stirred precursor liquid for 48 hours, wherein a large amount of solid substances are generated in an aged precursor liquid container. And (3) separating solid substances in the precursor liquid container through suction filtration, and washing the solid substances with deionized water for 5 times. And drying the washed solid substance at 90 ℃ for 16h, roasting the dried solid substance at 500 ℃ for 4h, naturally cooling the roasted solid substance, and grinding the solid substance on a ball mill for 1h to obtain the Bi-Ni bimetal modified hydrotalcite derivative composite oxide.
(4) Preparation of internal catalytic coating and its application
Al in the Aluminosol used in example 22O310.8 percent of SiO in the silica gel2The mass percentage of (B) is 25%. Weighing 100g of LaxSr(1-x)MnyCo(1-y)O3Perovskite-type composite oxide, 333.2g Ba (CH)3COO)2、201.8g Ce(NO3)3·6H2O、69.7g Zr(NO3)4·5H2O, 1280g of Bi-Ni bimetal modified hydrotalcite derivative composite oxide, 1481.5g of aluminum sol, 640g of silica gel, 200g of polyethylene glycol with the average molecular weight of 20000 and 1000g of nitric acid, wherein all the raw materials are added into 20000g of deionized water and are fully stirred to form uniform suspension. And grinding the suspension on a wet grinding machine until the particle size of D50 is within the range of 1.0-1.2 microns, and stirring the ground suspension at 60 ℃ for 24 hours to obtain the internal catalytic coating slurry. Weighing 1000g of 400-mesh cordierite honeycomb ceramic carrier, immersing the carrier in the slurry of the internal catalytic coating at 60 ℃, taking the carrier out of the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying at 90 ℃ for 12 hours, and roasting at 500 ℃ for 4 hours; repeating the above dipping, drying and roasting process for 2 times to complete the internal catalytic coatingPreparation of the layer.
(5) Preparation and application of outer catalytic coating
Weighing 190g of LaxSr(1-x)MnyCo(1-y)O3Perovskite-type composite oxide, 26.5g H2PtCl6·6H2O、333.2g Ba(CH3COO)2、201.8g Ce(NO3)3·6H2O、69.7g Zr(NO3)4·5H2O, 1350g of Bi-Ni bimetal modified hydrotalcite derivative composite oxide, 1388.9g of aluminum sol, 100g of polyethylene glycol with the average molecular weight of 20000 and 1000g of nitric acid, and all the raw materials are added into 30000g of deionized water and fully stirred to form uniform suspension. And grinding the suspension on a wet grinding machine until the particle size of D50 is within the range of 1.0-1.2 microns, and stirring the ground suspension at 60 ℃ for 24 hours to obtain the external catalytic coating slurry. And immersing the 400-mesh cordierite honeycomb ceramic carrier coated with the inner catalytic coating into the slurry of the outer catalytic coating at the temperature of 80 ℃, taking the carrier out of the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying for 12h at the temperature of 90 ℃, and roasting for 4h at the temperature of 500 ℃, thus finishing the preparation and coating of the outer catalytic coating.
Example 3
(1) Catalyst composition design
Respectively designing Pt and La in main active components of the outer catalytic coatingxSr(1-x)MnyCo(1-y)O3The perovskite composite oxide comprises the following components in percentage by mass: 5%/95%; the mass percentages of the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating are as follows: 15%/10%/5%/70%; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al in base material of inner catalytic coating2O3And SiO2The mass percentage of the components is as follows: 85%/10%/5%; the mass percentages of the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating are as follows: 10%/10%/10%/70%; laxSr(1-x)MnyCo(1-y)O3The molar percentage of La ions to Sr ions in the perovskite composite oxide is as follows: 50%/50%, the molar percentage of Mn ions to Co ions is: 50%/50%; in the Bi-Ni bimetal modified hydrotalcite derived composite oxide, Bi2O3And Al2O3The mole percentage of (A) is as follows: 50%/50% and the molar percentages of NiO and MgO are as follows: 50%/50%. The mass percentage ranges of the outer catalytic coating, the inner catalytic coating and the 400-mesh cordierite honeycomb ceramic carrier are as follows: 6-7%/15-16%/79-77%. The prepared outer catalytic coating slurry can prepare 2000g of outer catalytic coating and the prepared inner catalytic coating slurry can prepare 2000g of inner catalytic coating.
(2)LaxSr(1-x)MnyCo(1-y)O3Preparation of perovskite composite oxide
Weighing 481.3g La (NO)3)3·6H2O、235.2g Sr(NO3)2、272.4g Mn(CH3COO)2·4H2O、323.6g Co(NO3)2·6H2O and 801.2g C6H12O6The 5 raw materials are added into 3.5L of deionized water together to prepare a solution. The solution was evaporated on a rotary evaporator at 70 ℃ until the solution turned into a honey-like wet gel, which was dried at 90 ℃ for 8h to give a pale yellow xerogel. Heating the xerogel to 400 ℃ at the speed of 3 ℃/min in a muffle furnace, keeping for 2h, heating to 800 ℃ at the speed of 10 ℃/min, and roasting for 3h to obtain LaxSr(1-x)MnyCo(1-y)O3A perovskite-type composite oxide.
(3) Preparation of Bi-Ni bimetal modified hydrotalcite derived composite oxide
1889.3g Bi (NO) were weighed out3)3·5H2O、1461.0g Al(NO3)3·9H2O、3398.0g Ni(NO3)2·6H2O、2996.0g Mg(NO3)2·6H2O, adding the 4 raw materials into 15L of deionized water, stirring to prepare a solution,the fluid of the forebody is. 200g NaOH and 265g Na were weighed out2CO3Adding the two raw materials into 5L of deionized water, and fully stirring until NaOH and Na are obtained2CO3Completely dissolved as buffer. Then adding the buffer solution into the precursor solution at the speed of 40ml/min, stirring vigorously, and simultaneously, continuously measuring the pH value of the precursor solution in which the buffer solution is being added by using a pH value analyzer; stopping adding the buffer solution when the pH value of the precursor solution is between 9.5 and 10.5, and continuously stirring the precursor solution for 3 hours; and standing and aging the stirred precursor liquid for 36 hours, wherein a large amount of solid substances are generated in an aged precursor liquid container. Solid substances in the precursor liquid container are separated through suction filtration, and then the solid substances are washed by deionized water for 4 times; and drying the washed solid substance at 100 ℃ for 12h, roasting the dried solid substance at 600 ℃ for 2h, naturally cooling the roasted solid substance, and grinding the solid substance on a ball mill for 1h to obtain the Bi-Ni bimetal modified hydrotalcite derivative composite oxide.
(4) Preparation of internal catalytic coating and its application
Al in the Aluminosol used in example 32O310.8 percent of SiO in the silica gel2The mass percentage of (B) is 25%. Weighing 200g of LaxSr(1-x)MnyCo(1-y)O3Perovskite-type composite oxide, 333.2g Ba (CH)3COO)2、403.6g Ce(NO3)3·6H2O、139.4g Zr(NO3)4·5H2O, 1190g of Bi-Ni bimetal modified hydrotalcite derived composite oxide, 1296.3g of aluminum sol, 280g of silica gel, 200g of polyethylene glycol with the average molecular weight of 20000 and 500g of nitric acid, and all the raw materials are added into 25000g of deionized water and fully stirred to form uniform suspension. And grinding the suspension on a wet grinding machine until the particle size of D50 is within the range of 1.0-1.2 microns, and stirring the ground suspension at 70 ℃ for 20 hours to obtain the internal catalytic coating slurry. Weighing 1000g of 400-mesh cordierite honeycomb ceramic carrier, immersing the carrier in the slurry of the internal catalytic coating at 70 ℃, after the slurry is naturally lifted to fill all pore channels of the carrier,the support was removed from the slurry, the residual fluid in the channels was blown off, dried at 100 ℃ for 9h and calcined at 500 ℃ for 4 h. Repeating the processes of dipping, drying and roasting for 2 times to finish the preparation of the inner catalytic coating.
(5) Preparation of outer catalytic coating and its application
Weighing 39.8g H2PtCl6·6H2O、285g LaxSr(1-x)MnyCo(1-y)O3Perovskite-type composite oxide, 333.2g Ba (CH)3COO)2、201.8g Ce(NO3)3·6H2O、69.7g Zr(NO3)4·5H2O, 1260g of Bi-Ni bimetal modified hydrotalcite derivative composite oxide, 1296.3g of aluminum sol, 300g of polyethylene glycol with the average molecular weight of 20000 and 1000g of nitric acid, and all the raw materials are added into 26000g of deionized water and fully stirred to form uniform suspension. And grinding the suspension on a wet grinding machine until the particle size of D50 is within the range of 1.0-1.2 microns, and stirring the ground suspension at 70 ℃ for 20 hours to obtain the external catalytic coating slurry. And immersing the 400-mesh cordierite honeycomb ceramic carrier coated with the inner catalytic coating into the slurry of the outer catalytic coating at 70 ℃, taking the carrier out of the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying for 9h at 100 ℃, and roasting for 2h at 600 ℃, thus finishing the preparation and coating of the outer catalytic coating.
The NOx adsorption-reduction purification performance of diesel exhaust of the catalysts prepared in examples 1 to 3 was evaluated by using the LNT catalyst NOx purification performance engine evaluation system shown in fig. 1. Before the test, the catalysts prepared in examples 1 to 3 are respectively cut and respectively combined into 4L monolithic catalysts, and the cut and combined monolithic catalysts are packaged. The test method comprises the following steps:
(1) and (3) steady-state working condition test: the torque and the rotating speed of a test engine (CY4102 type diesel engine) 3 are controlled by using a dynamometer 1 and a coupling 2, the temperature and the humidity of inlet air of the engine are regulated to a stable state by using an inlet air conditioner 5, and the exhaust flow of the engine and the volume of a catalyst are adjusted successivelyThe ratio is respectively 30000h-1And 50000h-1And sequentially controlling the temperature of the central point of the LNT catalyst 12 to be 250 ℃ and 350 ℃ respectively, and carrying out catalytic activity evaluation on the catalyst NOx adsorption-reduction reaction. In the test, the fuel supply speed of the fuel injector 6 to the diesel engine is adjusted through the fuel injection control system 7, so that the lean burn/rich burn working condition switching is realized in the running process of the diesel engine. Exhaust gas formed by combustion in a cylinder of the diesel engine passes through an exhaust stabilizer 10 and then enters an LNT (Low-Density fuel) catalyst for adsorption-reduction purification treatment. Diesel exhaust before and after LNT catalyst treatment enters an engine exhaust analyzer 16 through an exhaust sampling passage 15 from an exhaust sampling port A8 and an exhaust sampling port B14 respectively for NOx concentration analysis, and gas after NOx analysis is discharged out of a test room through an air pump 17. Temperature sensor a9 and temperature sensor B11 measure the exhaust gas temperature before and after the exhaust gas regulator 10, and temperature sensor C13 measures the temperature of the center of the LNT catalyst. The temperature measurements of the 3 temperature sensors and the intake air flow measurements of the intake air flow meter 4 provide feedback parameters for the control strategy of the fuel injection control system and the dynamometer. By utilizing the LNT catalyst NOx purification performance engine evaluation system, the exhaust temperature is 250 ℃ and the airspeed is 30000h under the lean-burn working condition of the diesel engine-1The exhaust temperature is 350 ℃ and the space velocity is 50000h under the time and lean combustion working conditions-1In the diesel engine exhaust NOx adsorption-reduction reaction catalyzed by the catalysts prepared in examples 1 to 3, the purification efficiency of NOx is shown in fig. 2 and 3, respectively.
(2) ESC test: by adopting the evaluation system of the NOx purification performance engine of the LNT catalyst, the NOx purification effect in the adsorption-reduction reaction of the NOx exhausted by the diesel engine catalyzed by the catalyst prepared in the examples 1-3 is evaluated according to ESC test regulations specified in national standard GB 17691-2005 emission limit values of the compression ignition type engine and the gas fuel ignition type engine for vehicles and the emission limit values of pollutants exhausted by the automobiles and a measurement method (China stages III, IV and V), as shown in FIG. 4.
In conclusion, the invention discloses a diesel engine double-coating catalyst based on hydrotalcite derived oxide and a preparation method thereof. The outer catalytic coating of the catalyst contains Pt and the main active component of perovskite type composite oxide; a BaO adsorbent; CeO (CeO)2-ZrO2A cocatalyst; modified hydrotalcite-derived composite oxide and gamma-Al2O3Coating a base material; the inner catalytic coating contains a main active component of perovskite type composite oxide; a BaO adsorbent; CeO (CeO)2-ZrO2A cocatalyst; modified hydrotalcite-derived composite oxide, gamma-Al2O3And SiO2Coating a base material; and a 400 mesh cordierite honeycomb ceramic carrier. The preparation process comprises the following steps: designing the composition of a catalyst; laxSr(1-x)MnyCo(1-y)O3The preparation of perovskite composite oxide and Bi-Ni bimetal modified hydrotalcite derivative composite oxide, and the preparation and coating of inner and outer catalytic coatings. Through the cyclic change of the lean/rich combustion working condition of the diesel engine, the catalyst can efficiently catalyze the adsorption-reduction purification reaction of NOx in exhaust. According to the invention, most of noble metals in the traditional LNT catalyst are replaced by the perovskite type composite oxide, so that the sulfur resistance and the thermal stability of the novel LNT catalyst are improved while the raw material cost is reduced. Meanwhile, the modified hydrotalcite-derived composite oxide is used for replacing most of Al in the traditional LNT catalyst2O3The NOx adsorption capacity of the LNT catalyst is significantly improved. In addition, the LNT catalyst adopts a non-uniform double-coating preparation method, so that the distribution characteristic of functional materials is optimized, the cost of the novel LNT catalyst raw materials is further reduced, and the NOx purification effect, durability and reliability of the catalyst are improved.
While the present invention has been described with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are illustrative only and not restrictive, and various modifications which do not depart from the spirit of the present invention and which are intended to be covered by the claims of the present invention may be made by those skilled in the art.

Claims (6)

1. A diesel engine double-coating catalyst based on hydrotalcite derived oxide is characterized in that: the catalyst comprises two catalytic coatings which are sequentially coated on a catalyst carrier, wherein the catalytic coating coated on the catalyst carrier is an inner catalytic coating, and the catalytic coating which is coated on the inner catalytic coating and has different component composition from the inner catalytic coating is an outer catalytic coating;
the catalyst carrier is 400-mesh cordierite honeycomb ceramic;
the outer catalytic coating comprises Pt and LaxSr（1-x）MnyCo (1-y)O3Perovskite composite oxide, BaO, CeO2-ZrO2Solid solution, Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3；
The inner catalytic coating comprises LaxSr（1-x）MnyCo (1-y)O3Perovskite composite oxide, BaO, CeO2-ZrO2Solid solution, Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3And SiO2；
The LaxSr（1-x）MnyCo (1-y)O3The perovskite composite oxide is characterized in that x represents the molar percentage of La in the sum of the molar numbers of Sr and La ions, and x = 25-75%; y represents the molar percentage of Mn in the sum of the molar numbers of Co and Mn ions, and y = 25-50%; meanwhile, the LaxSr（1-x）MnyCo (1-y)O3The ratio of the sum of the number of moles of La ions and Sr ions to the sum of the number of moles of Mn ions and Co ions in the perovskite-type composite oxide is 1: 1;
the Bi-Ni bimetal modified hydrotalcite derived composite oxide is prepared by partially replacing Al with Bi2O3Partially substituting Al with Ni in 6MgO type hydrotalcite-like compound-derived composite oxide2O36MgO type hydrotalcite-like compound derived composite oxide containing Mg, wherein Bi, Al, Ni and Mg are each Bi2O3、Al2O3NiO and MgO are dispersed in the Bi-Ni bimetal modified hydrotalcite derived composite oxide, and Bi2O3And Al2O3The mole percentage of (A) is as follows: 50-80%/50-20%, the sum of the mole percentages is 100%; the mol percentages of NiO and MgO are as follows: 2575%/75-25%, the sum of the mole percentages is 100%; and the ratio of the sum of the molar numbers of Bi ions and Al ions to the sum of the molar numbers of Ni ions and Mg ions in the Bi-Ni bimetal modified hydrotalcite derived composite oxide is as follows: 1: 3;
in the outer catalytic coating, Pt and LaxSr（1-x）MnyCo (1-y)O3The perovskite composite oxide forms the main active component of the outer catalytic coating, and Pt and LaxSr（1-x）MnyCo (1-y)O3The perovskite composite oxide comprises the following components in percentage by mass: 2-5%/98-95%, the sum of the mass percentages is 100%; an adsorbent with external catalytic coating composed of BaO and CeO2-ZrO2Solid solution forms an outer catalytic coating cocatalyst; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3The Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al form an outer catalytic coating base material2O3The mass percentage of the components is as follows: 90%/10%; the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating jointly form the outer catalytic coating of the catalyst, wherein the mass percentages of the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating respectively correspond to: 10-15%/10%/5-10%/75-65%, the sum of the mass percentages is 100%;
in the internal catalytic coating, LaxSr（1-x）MnyCo (1-y)O3The main active component of the inner catalytic coating is composed of perovskite composite oxide; an adsorbent with internal catalytic coating composed of BaO and CeO2-ZrO2Solid solution is used for forming an inner catalytic coating cocatalyst; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al2O3And SiO2The Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al are used as the base material of the internal catalytic coating2O3And SiO2The mass percentage of the components is as follows: 80-85%/10%/10-5%, the sum of the mass percentages is 100%(ii) a The main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating jointly form the inner catalytic coating of the catalyst, wherein the mass percentages of the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating respectively correspond to: 5-10%/10%/5-10%/80-70%, the sum of the mass percentages being 100%.
2. A diesel double-coated catalyst based on hydrotalcite derived oxides according to claim 1, characterized in that: the CeO2-ZrO2CeO in solid solution2And ZrO2The mass percentage of the components is as follows: 80%/20%.
3. A diesel double-coated catalyst based on hydrotalcite derived oxides according to claim 1, characterized in that: the gamma-Al2O3Generated by the conversion of aluminum sol as a coating binder; the SiO2Is formed by the conversion of silica gel as a coating binder.
4. The hydrotalcite derived oxide based diesel dual coated catalyst according to claim 1, characterized in that: the mass percentages of the outer catalytic coating, the inner catalytic coating and the catalyst carrier are as follows: 4-8%/12-18%/84-74%, and the sum of the mass percentages is 100%.
5. A process for the preparation of a double-coated catalyst for diesel engines based on hydrotalcite derived oxides according to any of claims 1 to 4, characterized in that: the method comprises the following steps:
step one, designing a catalyst composition:
respectively designing: the LaxSr（1-x）MnyCo (1-y)O3The mol percentage of La ions and Sr ions and the mol percentage of Mn ions and Co ions in the perovskite composite oxide; in the Bi-Ni bimetal modified hydrotalcite derived composite oxide, Bi2O3And Al2O3The mole percent of NiO and the mole percent of MgO; pt and La in main active components of the outer catalytic coatingxSr（1-x）MnyCo (1-y)O3Mass percent of the perovskite-type composite oxide; the mass percentages of the main active component of the outer catalytic coating, the adsorbent of the outer catalytic coating, the cocatalyst of the outer catalytic coating and the base material of the outer catalytic coating; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al in the outer catalytic coating base material2O3The mass percentage of (A); the mass percentages of the main active component of the inner catalytic coating, the adsorbent of the inner catalytic coating, the cocatalyst of the inner catalytic coating and the base material of the inner catalytic coating are as follows; Bi-Ni bimetal modified hydrotalcite derived composite oxide and gamma-Al in the base material of the internal catalytic coating2O3And SiO2The mass percentage of (A); the mass percentage ranges of the outer catalytic coating, the inner catalytic coating and the catalyst carrier are as follows; the quality of the external catalytic coating prepared by the external catalytic coating slurry and the quality of the internal catalytic coating prepared by the internal catalytic coating slurry can be respectively prepared;
step two, LaxSr（1-x）MnyCo (1-y)O3Preparation of perovskite composite oxide
Calculating the La required for preparing the inner catalytic coating and the outer catalytic coating according to the proportion of each component designed in the step onexSr（1-x）MnyCo (1-y)O3The total mole number of the perovskite composite oxide and the mole number of La, Sr, Mn and Co ions in the perovskite composite oxide are 433.0g La (NO)3)3▪6H2O preparation of 1mol of La ion, 211.6g of Sr (NO)3)2Preparation of 1mol of Sr ion, 245.1g of Mn (CH)3COO)2▪4H2O preparation of 1mol Mn ion, 291.1g Co (NO)3)2▪6H2Reduced proportion of 1mol Co ions prepared from O, total mole number of the four raw materials and C6H12O6Is a ratio of 1:1 and C6H12O6Molecular weight is 180.2, calculated to prepare LaxSr（1-x）MnyCo (1-y)O3La (NO) required for perovskite composite oxide3)3▪6H2O、Sr(NO3)2、Mn(CH3COO)2▪4H2O、Co(NO3)2▪6H2O、C6H12O6The quality of the five raw materials;
mixing the La (NO) mentioned above3)3▪6H2O、Sr(NO3)2、Mn(CH3COO)2▪4H2O、Co(NO3)2▪6H2O、C6H12O6Adding five raw materials into deionized water according to the proportion that each mole of metal ions is dissolved in 0.75-1L of deionized water to prepare a solution; evaporating the solution on a rotary evaporator at 60-80 ℃ until the solution is converted into a honey-like wet gel; drying the wet gel at 80-110 ℃ for 6-12 h to obtain fluffy, fragile and faint yellow dry gel; heating the xerogel to 400 ℃ at the speed of 3 ℃/min in a muffle furnace, keeping for 2h, heating to 800 ℃ at the speed of 10 ℃/min, and roasting for 3h to obtain LaxSr（1-x）MnyCo (1-y)O3A perovskite-type composite oxide;
step three, preparing Bi-Ni bimetal modified hydrotalcite derived composite oxide:
calculating the total mass of Bi-Ni bimetal modified hydrotalcite derived composite oxide required by preparing the inner catalytic coating and the outer catalytic coating and Bi in the Bi-Ni bimetal modified hydrotalcite derived composite oxide according to the proportion of each component designed in the step one2O3、Al2O3NiO, MgO, and 970.1g Bi (NO)3)3▪5H2O preparation of 1mol Bi2O3、750.2g Al(NO3)3▪9H2O preparation of 1mol Al2O3、290.8g Ni(NO3)2▪6H2O preparation of 1mol NiO, 256.4g Mg (NO)3)2▪6H2Calculating the conversion ratio of 1mol MgO prepared by O to Bi (NO) required by preparing Bi-Ni bimetal modified hydrotalcite derivative composite oxide3)3▪5H2O、Al(NO3)3▪9H2O、Ni(NO3)2▪6H2O、Mg(NO3)2▪6H2O, the mass of the four raw materials; weighing the Bi (NO) according to the determined mass3)3▪5H2O、Al(NO3)3▪9H2O、Ni(NO3)2▪6H2O、Mg(NO3)2▪6H2Adding the four raw materials into deionized water weighed according to the proportion that each mole of Ni ions and each mole of Mg ions correspond to 0.5-1L of deionized water, and stirring to prepare a solution, namely a precursor solution;
weighing sufficient NaOH and Na2CO3And the mole number of NaOH is equal to that of Na2CO3The molar ratio of the NaOH to the Na is 2:1, and then the NaOH and the Na are mixed according to the ratio that each mole of NaOH corresponds to 1L of deionized water2CO3Adding into deionized water, stirring thoroughly until NaOH and Na2CO3Completely dissolving to obtain a buffer solution;
adding a buffer solution into the precursor solution at the speed of 30-50 mL/min, stirring vigorously, and simultaneously continuously measuring the pH value of the precursor solution added with the buffer solution by using a pH value analyzer; stopping adding the buffer solution when the pH value is between 9.5 and 10.5, continuously stirring for 2 to 4 hours, standing and aging for 24 to 48 hours, performing suction filtration to separate out solid substances in the aged solution, washing the solid substances with deionized water for 3 to 5 times, drying at 90 to 110 ℃ for 8 to 16 hours, roasting at 500 to 600 ℃ for 2 to 4 hours, naturally cooling, and grinding the solid substances on a ball mill for 1 hour to obtain the Bi-Ni bimetal modified hydrotalcite derived composite oxide;
step four, preparing and coating the inner catalytic coating:
calculating La required by the preparation of the inner catalytic coating according to the proportion of each component designed in the step onexSr（1-x）MnyCo (1-y)O3Perovskite composite oxide, BaO, CeO2、ZrO2Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3、SiO2The mass of (c); binding 255.4g Ba (CH)3COO)2Preparation of 153.3g of BaO, 434.1g of Ce (NO)3)3▪6H2O preparation of 172.1g CeO2、429.3g Zr(NO3)4▪5H2O preparation 123.2g ZrO2Calculating the conversion ratio of Ba (CH) required by preparing the internal catalytic coating3COO)2、Ce(NO3)3▪6H2O、Zr(NO3)4▪5H2The mass of O; according to Al in the alumina sol2O3And SiO in silica gel2Respectively calculating the mass of the consumed aluminum sol and the mass of the consumed silica gel required by the preparation of the inner catalytic coating; in addition, the mass of the polyethylene glycol and the nitric acid consumed for preparing the inner catalytic coating is calculated according to the proportion that every 100g of the inner catalytic coating needs 5-15 g of polyethylene glycol with the average molecular weight of 20000 and 25-50 g of nitric acid; weighing Ba (CH) according to the determined mass3COO)2、Ce(NO3)3▪6H2O、Zr(NO3)4▪5H2O, alumina sol, silica gel, polyethylene glycol with average molecular weight of 20000, nitric acid and LaxSr（1-x）MnyCo (1-y)O3Adding all the raw materials into deionized water with the mass being 10-15 times of the total mass of the prepared inner catalytic coating, and fully stirring to form uniform suspension; grinding the suspension on a wet grinding machine until the median particle size is within the range of 1.0-1.2 microns, and then stirring the ground suspension for 16-24 hours at the temperature of 60-80 ℃ to obtain internal catalytic coating slurry;
the mass percentages of the inner catalytic coating, the outer catalytic coating and the catalyst carrier are as follows: 4-8%/12-18%/84-74%, and the sum of the mass percentages is 100%; carrying out internal catalytic coating and 400-mesh cordierite honeycomb ceramic batching, and carrying out the following dipping, drying and calcining treatments:
weighing a 400-mesh cordierite honeycomb ceramic carrier with determined mass, immersing the ceramic carrier in the slurry of the internal catalytic coating at the temperature of 60-80 ℃, taking the carrier out of the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying at the temperature of 90-110 ℃ for 6-12 h, and roasting at the temperature of 500-600 ℃ for 2-4 h;
repeating the processes of dipping, drying and roasting for 2 times to finish the coating of the inner catalytic coating;
step five, preparing and coating an outer catalytic coating:
calculating the Pt and La required by the preparation of the outer catalytic coating according to the proportion of each component designed in the step onexSr（1-x）MnyCo (1-y)O3Perovskite composite oxide, BaO, CeO2、ZrO2Bi-Ni bimetal modified hydrotalcite derived composite oxide, gamma-Al2O3The mass of (c); combination 517.9g H2PtCl6▪6H2O preparation of 195.1g Pt, 255.4g Ba (CH)3COO)2Preparation of 153.3g of BaO, 434.1g of Ce (NO)3)3▪6H2O preparation of 172.1g CeO2、429.3g Zr(NO3)4▪5H2O preparation 123.2g ZrO2Calculating the H required by preparing the outer catalytic coating according to the conversion ratio2PtCl6▪6H2O、Ba(CH3COO)2、Ce(NO3)3▪6H2O、Zr(NO3)4▪5H2The mass of O; according to Al in the alumina sol2O3Calculating the mass of the consumed aluminum sol required for preparing the outer catalytic coating according to the mass percentage; in addition, the mass of the polyethylene glycol and the nitric acid consumed for preparing the outer catalytic coating is calculated according to the proportion that every 100g of the outer catalytic coating needs 5-15 g of polyethylene glycol with the average molecular weight of 20000 and 25-50 g of nitric acid; weighing the outer catalytic coating preparation according to the determined mass for preparing H2PtCl6▪6H2O、Ba(CH3COO)2、Ce(NO3)3▪6H2O、Zr(NO3)4▪5H2O, alumina sol, polyethylene glycol with average molecular weight of 20000, nitric acid and LaxSr（1-x）MnyCo (1-y)O3Perovskite-type composite oxide and Bi-Ni, adding all the raw materials into deionized water with the mass being 10-15 times of the total mass of the prepared outer catalytic coating, and fully stirring to form uniform suspension; grinding the suspension on a wet grinding machine until the median particle size is within the range of 1.0-1.2 microns, and then stirring the ground suspension for 16-24 hours at the temperature of 60-80 ℃ to obtain outer catalytic coating slurry;
immersing the 400-mesh cordierite honeycomb ceramic carrier coated with the inner catalytic coating into slurry of the outer catalytic coating at the temperature of 60-80 ℃, taking the carrier out of the slurry after the slurry is naturally lifted to fill all pore channels of the carrier, blowing off residual fluid in the pore channels, drying at the temperature of 90-110 ℃ for 6-12 h, and roasting at the temperature of 500-600 ℃ for 2-4 h; namely, the coating of the outer catalytic coating is finished, and finally the diesel engine double-coating catalyst based on the hydrotalcite derived oxide is obtained.
6. The application of the diesel engine double-coating catalyst based on the hydrotalcite derived oxide is characterized in that: the hydrotalcite derived oxide-based diesel engine double-coated catalyst prepared by the preparation method of claim 5 is encapsulated, and the encapsulated catalyst is installed in an exhaust passage of a diesel engine to purify NOx pollutants in exhaust gas of the diesel engine through NOx adsorption-reduction reaction.
CN201811651436.1A 2018-12-31 2018-12-31 Diesel engine double-coating catalyst based on hydrotalcite derived oxide and preparation method thereof Active CN109589988B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201811651436.1A CN109589988B (en) 2018-12-31 2018-12-31 Diesel engine double-coating catalyst based on hydrotalcite derived oxide and preparation method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201811651436.1A CN109589988B (en) 2018-12-31 2018-12-31 Diesel engine double-coating catalyst based on hydrotalcite derived oxide and preparation method thereof

Publications (2)

Publication Number Publication Date
CN109589988A CN109589988A (en) 2019-04-09
CN109589988B true CN109589988B (en) 2021-11-02

Family

ID=65965737

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201811651436.1A Active CN109589988B (en) 2018-12-31 2018-12-31 Diesel engine double-coating catalyst based on hydrotalcite derived oxide and preparation method thereof

Country Status (1)

Country Link
CN (1) CN109589988B (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110508301B (en) * 2019-08-29 2022-02-22 华南农业大学 Biological methanol conversion catalyst SrNiO for full components of methane3/SiC-SiO2-Foam and preparation method thereof
CN111672519A (en) * 2020-03-05 2020-09-18 王金波 Noble metal-rare earth perovskite type integral three-way catalyst and preparation method thereof
CN111841572B (en) * 2020-08-06 2021-04-30 合肥神舟催化净化器股份有限公司 High-acidity single-coating perovskite-based ammonia oxidation catalyst for diesel engine and preparation and application methods thereof
CN112076741B (en) * 2020-09-18 2023-04-14 宁夏大学 CeO (CeO) 2 /Bi 2 O 4 Composite visible light catalyst and preparation method thereof
CN112221511B (en) * 2020-10-13 2022-07-19 天津大学 Ternary metal oxide based diesel particulate oxidation catalyst and preparation method thereof

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102614780A (en) * 2011-01-13 2012-08-01 通用汽车环球科技运作有限责任公司 Sulfur-tolerant perovskite NOx oxidation catalysts
CN103071386A (en) * 2013-01-18 2013-05-01 大连理工大学 Plasma-promoted nitrogen oxide storing reducing and removing method
WO2014183006A1 (en) * 2013-05-10 2014-11-13 Clean Diesel Technologies, Inc. Zpgm diesel oxidation catalysts and methods of making and using same
CN106582794A (en) * 2016-11-18 2017-04-26 天津大学 Catalyst based on modified molecular sieve and hydrotalcite derived oxides and applied to diesel engine, preparation and application

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100836907B1 (en) * 2006-06-23 2008-06-12 희성촉매 주식회사 Transition metal-substituted hydrotalcite catalysts for the removal of nitrogen oxide from the exhaust of diesel engines by the storage-reduction method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102614780A (en) * 2011-01-13 2012-08-01 通用汽车环球科技运作有限责任公司 Sulfur-tolerant perovskite NOx oxidation catalysts
CN103071386A (en) * 2013-01-18 2013-05-01 大连理工大学 Plasma-promoted nitrogen oxide storing reducing and removing method
WO2014183006A1 (en) * 2013-05-10 2014-11-13 Clean Diesel Technologies, Inc. Zpgm diesel oxidation catalysts and methods of making and using same
CN106582794A (en) * 2016-11-18 2017-04-26 天津大学 Catalyst based on modified molecular sieve and hydrotalcite derived oxides and applied to diesel engine, preparation and application

Also Published As

Publication number Publication date
CN109589988A (en) 2019-04-09

Similar Documents

Publication Publication Date Title
CN109589988B (en) Diesel engine double-coating catalyst based on hydrotalcite derived oxide and preparation method thereof
KR101868176B1 (en) Catalyst for gasoline lean burn engines with improved no oxidation activity
JP5771267B2 (en) A novel mixed oxide material for selective catalytic reduction of nitrogen oxides in exhaust gas
CN109589987B (en) Catalyst for diesel engine based on perovskite and modified hydrotalcite derived oxide and preparation method thereof
CN109590017B (en) Diesel engine catalyst based on composite main catalyst and hydrotalcite derived oxide and preparation method thereof
CN106582794B (en) Use for diesel engine catalyst and preparation and application based on modified molecular screen and hydrotalcite Derived Oxides
CN112221495B (en) Catalyst for noble metal substituted perovskite diesel oxidation catalyst and preparation method thereof
KR101859786B1 (en) Catalyst for gasoline lean burn engines with improved nh3-formation activity
CN112805089A (en) Transition metal doped alumina for improved OSC and TWC performance
WO2019088302A1 (en) Oxygen absorbing and releasing material, catalyst, exhaust gas purifying system, and exhaust gas treatment method
CN109499568B (en) Diesel vehicle tail gas purification catalyst based on iron-modified hydrotalcite derived oxide and preparation method thereof
CN111111642B (en) Denitration catalyst and preparation method and application thereof
JP4277771B2 (en) Exhaust gas purification catalyst, exhaust gas purification device, and system including an internal combustion engine
CN109589976B (en) Catalyst for diesel engine based on oxide composite main catalyst and preparation method thereof
CN109590016B (en) Catalyst for diesel engine based on modified hydrotalcite derived oxide and preparation method thereof
CN102574057B (en) Oxygen adsorbent based on lanthanoide oxysulfate, method for producing it, and exhaust gas purifying catalyst containing it
JP6339013B2 (en) Exhaust gas purification catalyst carrier, exhaust gas purification catalyst, and exhaust gas purification catalyst structure
JPH03131343A (en) Preparation of catalyst for purifying exhaust gas
CN114425410B (en) Catalyst for treating ammonia leakage of selective catalytic reduction device and preparation method thereof
CN114682293B (en) Heat-resistant modified mesoporous molecular sieve based nitrogen oxide trapping catalyst, and preparation method and application thereof
CN114682270B (en) Hydrotalcite derived oxide based nitrogen oxide trapping catalyst, preparation method and application
EP2998022A1 (en) Exhaust gas purification catalyst composition and exhaust gas purification catalyst
JPH11290686A (en) Exhaust gas cleaning catalyst
WO2023020579A1 (en) Metal oxide catalyst for selective catalytic reduction
JP3896706B2 (en) Exhaust gas purification catalyst and method for producing the same

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant