CN111974390A - Catalyst for tail gas of diesel vehicle, preparation process and application - Google Patents

Catalyst for tail gas of diesel vehicle, preparation process and application Download PDF

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CN111974390A
CN111974390A CN202010848605.1A CN202010848605A CN111974390A CN 111974390 A CN111974390 A CN 111974390A CN 202010848605 A CN202010848605 A CN 202010848605A CN 111974390 A CN111974390 A CN 111974390A
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slurry
water
salt
oxide
soluble
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CN111974390B (en
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樊蓉蓉
李兆强
王艳
张丞
王雨
丁智勇
王荣
郭欣
康娜
刘威
宋静
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Baotou Rare Earth Research Institute
Ruike Rare Earth Metallurgy and Functional Materials National Engineering Research Center Co Ltd
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Baotou Rare Earth Research Institute
Ruike Rare Earth Metallurgy and Functional Materials National Engineering Research Center Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/652—Chromium, molybdenum or tungsten
    • B01J23/6527—Tungsten
    • 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
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
    • 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
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0213—Preparation of the impregnating solution
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/088—Decomposition of a metal salt
    • 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
    • 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
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

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Abstract

The invention discloses a catalyst for diesel vehicle tail gas and a preparation process and application thereof. The preparation process comprises the following steps: (1) mixing the oxide slurry with tungstate to form a first slurry; adding a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt to the first slurry to form a second slurry; (2) mixing the second slurry, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt to obtain third slurry; (3) mixing the third slurry with a binder to obtain a fourth slurry; loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain a catalyst; wherein the oxide slurry contains alumina and at least one oxide selected from cerium oxide and zirconium oxide. The catalyst obtained by the method has lower ignition temperature after high-temperature treatment.

Description

Catalyst for tail gas of diesel vehicle, preparation process and application
Technical Field
The invention relates to a catalyst for diesel vehicle tail gas and a preparation process and application thereof.
Background
Diesel exhaust contains a large amount of carbon monoxide, nitrogen oxides and hydrocarbons, which are major sources of atmospheric pollution. Diesel vehicle oxidation catalysts (DOC) are the key core of diesel vehicle exhaust treatment systems, which can be applied to the oxidation of carbon monoxide and hydrocarbons. Up to now, diesel vehicle oxidation catalysts (DOC) on the market have the problems of large consumption of noble metals, poor high temperature resistance and poor aging resistance. Therefore, the method has important significance for reducing the consumption of noble metal and improving the high-temperature resistance and aging resistance of the catalyst.
CN1935370A discloses a preparation method of a three-way catalyst for purifying automobile exhaust using liquefied petroleum gas as fuel. Which comprises the following steps: (1) soaking a cordierite honeycomb ceramic carrier into the coating water slurry, drying, roasting, and coating the coating on the cordierite honeycomb ceramic; the coating water slurry is cerium-zirconium solid solution, rare earth oxide, alumina, tackifier and water. (2) The cordierite honeycomb ceramic carrier containing the coating is dipped into a water solution containing palladium salt, rhodium salt, nickel salt and cerium salt by adopting an isometric dipping method, and the catalyst is prepared after drying, roasting and hydrogen reduction. The catalyst is not suitable for tail gas purification of diesel vehicles, has poor high temperature resistance and aging resistance, and increases the ignition temperature after high-temperature treatment.
CN107649126A discloses a preparation method of a double-base noble metal DOC catalyst for purifying diesel exhaust. The method comprises the following steps: (1) mixing alumina powder or/and modified alumina powder and cerium-zirconium oxide or/and modified cerium-zirconium oxide according to a certain proportion, preparing the mixed powder into slurry, and putting the slurry into a ball mill or a sand mill for grinding; (2) mixing the solution of pt salt and pd salt with HAC or NH3·H2Adjusting the pH value of the slurry, diluting the noble metal salt solution with deionized water respectively, fully stirring the noble metal salt solution, slowly dripping a noble metal pt salt solution into a pd salt solution, and keeping the pd salt solution in a stirring state all the time; fully stirring two noble metal salt solutions after the dropwise adding is finished; (3) slowly dripping a solution containing two noble metal salts into the slurry prepared in the step (1) with a certain mass, wherein the slurry is always in a stirring state; aging to obtain slurry containing the pt-pd of the double-base noble metal, namely the DOC catalyst of the double-base noble metal. The catalyst obtained by the method has poor high temperature resistance and aging resistance, and the ignition temperature is increased after high-temperature treatment.
Disclosure of Invention
In view of the above, in one aspect, the present invention provides a process for preparing a catalyst for diesel vehicle exhaust, which can obtain a catalyst having a lower light-off temperature after a high-temperature treatment. In another aspect, the present invention provides a catalyst for diesel vehicle exhaust. In a further aspect, the invention provides the use of a composition.
In one aspect, the invention provides a preparation process of a catalyst for diesel vehicle exhaust, which comprises the following steps:
(1) mixing the oxide slurry with tungstate to form a first slurry; adding a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt to the first slurry to form a second slurry;
(2) mixing the second slurry, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt to obtain third slurry;
(3) mixing the third slurry with a binder to obtain a fourth slurry; loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain a catalyst;
wherein the oxide slurry contains alumina and at least one oxide selected from cerium oxide and zirconium oxide.
According to the preparation process disclosed by the invention, preferably, the usage amount of the tungstate is 0.5-5 wt% of the total mass of the oxides in the oxidant slurry in terms of tungsten trioxide; the tungstate is selected from one or more of ammonium tungstate, ammonium metatungstate or ammonium paratungstate.
According to the preparation process of the present invention, preferably, the oxide slurry contains alumina, zirconia and ceria, the mass ratio of the ceria to the zirconia to the alumina is (0.01-0.07): 0.04-0.09): 1, and the mass ratio of the ceria to the zirconia is (1-4): 2-5.
According to the production process of the present invention, preferably, a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt is added to the first slurry to form a second slurry;
taking a substrate of a cordierite honeycomb ceramic carrier as a reference, and the load capacity of platinum element is 8-25 g/ft3The loading amount of palladium element is 3-12 g/ft3(ii) a The mass ratio of the platinum element to the palladium element is (1-4) to 1; wherein, the platinum element is calculated by a platinum simple substance, and the palladium element is calculated by a palladium simple substance.
According to the preparation process disclosed by the invention, preferably, the dosage of the lanthanum element is 0.5-5 wt% of the total mass of the oxides in the oxidant slurry in terms of lanthanum oxide; based on yttrium oxide, the dosage of yttrium element is 0.5-5 wt% of the total mass of the oxide in the oxidant slurry.
According to the preparation process, the water-soluble zirconium salt is preferably used in an amount of 1-7 wt% of the total mass of the oxides in the oxidant slurry, calculated on the basis of the zirconia.
According to the preparation process of the invention, preferably, the binder is selected from one or more of aluminum sol, pseudo-boehmite, silica sol, cellulose, citric acid, polyvinyl alcohol and polyethylene glycol;
the drying temperature is 90-130 ℃, and the drying time is 2-6 h; the roasting temperature is 500-800 ℃, and the roasting time is 2-6 h;
the total load capacity of each element in the fourth slurry on the cordierite honeycomb ceramic carrier is 150-180 g/L in terms of oxide.
The invention also provides a preparation process of the catalyst, which comprises the following steps:
(1) mixing the oxide slurry with tungstate to form a first slurry; adding a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt to the first slurry to form a second slurry;
(2) mixing the second slurry, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt to obtain third slurry;
(3) mixing the third slurry with a binder to obtain a fourth slurry; loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain a roasted product;
(4) treating the roasted product at 700-1000 ℃ for 1-8 h to obtain a catalyst;
wherein the oxide slurry contains alumina and at least one oxide selected from cerium oxide and zirconium oxide.
In another aspect, the present invention provides a catalyst for diesel vehicle exhaust, which is obtained by the above preparation process;
the temperatures of the fresh catalyst, the aged catalyst and the high-temperature treated catalyst which correspond to the CO conversion rate of 50 percent are 140-180 ℃, 140-180 ℃ and 140-180 ℃ respectively;
fresh catalyst, aged catalyst and high-temperature treated catalyst pair C3H6The corresponding temperatures are 180-195 ℃, 170-195 ℃ and 170-195 ℃ respectively when the conversion rate is 50%;
the test was carried out in a fixed bed reactor under the following reaction conditions: CO 200ppm and C3H6＝180ppm、NO＝500ppm、CO2＝10vol％、O2＝10vol％，H2O＝7vol％、N2For balancing gas, the total flow is 550ml/min, and the space velocity is 80000h-1(ii) a The reaction temperature range is 100-500 ℃; the aging conditions were: h2O is 10 vol% and the space velocity is 60000h-1The aging temperature is 650 ℃, and the aging time is 100 hours; the high-temperature treatment conditions are as follows: roasting at 800 deg.c for 3 hr.
In yet another aspect, the present invention provides the use of a composition for reducing the light-off temperature of a high temperature treated diesel exhaust catalyst, the composition comprising a tungstate salt, a water soluble lanthanum salt, a water soluble yttrium salt, and a water soluble zirconium salt; the high-temperature treatment conditions are as follows: high-temperature treatment is carried out for 1-8 h at 700-1000 ℃.
The catalyst for the tail gas of the diesel vehicle prepared by the method has lower ignition temperature, and the ignition temperature of the catalyst can be further reduced after hydrothermal aging or high-temperature treatment. The applicants have surprisingly found that by adding water soluble lanthanum, yttrium, tungstate and zirconium salts during the preparation of the catalyst, the resulting catalyst has a lower light-off temperature after high temperature treatment.
Detailed Description
The present invention will be further described with reference to the following specific examples, but the scope of the present invention is not limited thereto.
< method for producing catalyst >
The preparation method of the catalyst comprises the following steps: (1) preparing slurry carrying catalytically active elements; (2) a step of preparing a supporting slurry containing an auxiliary agent; (3) and (3) preparing a catalyst. In addition, the present invention may further include the steps of: (4) and (5) high-temperature treatment. The catalyst of the invention is suitable for treating the tail gas of the diesel vehicle.
Step of preparing slurry carrying catalytically active elements
Mixing the oxide slurry with tungstate to form a first slurry; a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt is added to the first slurry to form a second slurry. According to one embodiment of the present invention, an oxide slurry is mixed with a tungstate to form a first slurry; a solution containing a water-soluble palladium salt is added to the first slurry to form a second slurry. According to another embodiment of the present invention, an oxide slurry is mixed with a tungstate to form a first slurry; a solution containing a water-soluble platinum salt is added to the first slurry to form a second slurry. According to yet another embodiment of the present invention, an oxide slurry is mixed with a tungstate to form a first slurry; a solution containing a water-soluble palladium salt and a water-soluble platinum salt is added to the first slurry to form a second slurry.
The oxide slurry is formed from an oxide and water. The oxide contains alumina and at least one oxide selected from cerium oxide and zirconium oxide. In certain embodiments, the oxide comprises alumina, ceria, and zirconia. The oxide may be composed of alumina, ceria and zirconia. According to a preferred embodiment of the present invention, the oxide may be composed of a solid solution of alumina and cerium zirconium. The mass ratio of cerium oxide to aluminum oxide may be (0.01 to 0.07): 1; preferably (0.02-0.06): 1; more preferably (0.03 to 0.05): 1. The mass ratio of zirconia to alumina may be (0.04-0.09): 1; preferably (0.05-0.09): 1; more preferably (0.06-0.08): 1. The mass ratio of cerium oxide to zirconium oxide may be (1-4) to (2-5); preferably (1-3) to (2-4); more preferably (2 to 3) and (3 to 4). Thus, the ignition temperature of the catalyst is reduced, and the aging resistance and high temperature resistance of the catalyst are improved.
The solid content of the oxide slurry can be 25-45 wt%; preferably 30 to 40 wt%; more preferably 33 to 37 wt%. The average value of the particle size of solid particles in the oxide slurry can be 1-10 mu m; preferably 3-8 μm; more preferably 4 to 7 μm.
The tungstate may be selected from one or more of ammonium tungstate, ammonium metatungstate, and ammonium paratungstate. Preferably, the tungstate is ammonium metatungstate. Calculated by tungsten trioxide, the usage amount of the tungstate is 0.5-5 wt% of the total mass of the oxides in the oxidant slurry; preferably 1 to 4 wt%; more preferably 1 to 3 wt%.
The mass fraction of solute in the solution containing water-soluble palladium salt and/or water-soluble platinum salt can be 10-25 wt%; preferably 15 to 25 wt%; more preferably 15 to 20 wt%. The water-soluble palladium salt and/or the water-soluble platinum salt may be a nitrate salt, such as palladium nitrate, platinum nitrate. Taking a substrate of the cordierite honeycomb ceramic carrier as a reference, and taking a platinum simple substance as a reference, wherein the load capacity of the platinum element is 8-25 g/ft3(ii) a Preferably 8 to 20g/ft3(ii) a More preferably 13 to 18g/ft3. Taking a substrate of the cordierite honeycomb ceramic carrier as a reference, and taking a palladium simple substance as a reference, wherein the load capacity of the palladium element is 3-12 g/ft3(ii) a Preferably 5 to 10g/ft3(ii) a More preferably 7 to 10g/ft3. The mass ratio of the platinum element to the palladium element can be (1-4) to 1; preferably (1-3) 1; more preferably (2-3): 1. Thus, the ignition temperature of the catalyst is reduced, and the aging resistance and high temperature resistance of the catalyst are improved.
Step of preparing supporting slurry containing auxiliary agent
And mixing the second slurry, the water-soluble lanthanum salt, the water-soluble yttrium salt and the water-soluble zirconium salt to obtain third slurry.
Based on lanthanum oxide, the dosage of lanthanum element is 0.5-5 wt% of the total mass of oxides in the oxidant slurry; preferably 1 to 4 wt%; more preferably 1 to 3 wt%. Based on yttrium oxide, the dosage of yttrium element is 0.5-5 wt% of the total mass of the oxide in the oxidant slurry; preferably 1 to 4 wt%; more preferably 1 to 3 wt%. The lanthanum element is calculated by lanthanum oxide, the yttrium element is calculated by yttrium oxide, and the mass ratio of the lanthanum element to the yttrium element can be 1 (0.5-2); preferably 1 (0.5-1.5); more preferably 1 (1-1.5). Thus, the ignition temperature of the catalyst is reduced, and the aging resistance and high temperature resistance of the catalyst are improved.
The water-soluble lanthanum salt and the water-soluble yttrium salt can be nitrate, sulfate, acetate or chloride. Examples of water soluble lanthanum salts, water soluble yttrium salts include, but are not limited to: lanthanum chloride, yttrium chloride, lanthanum nitrate, yttrium nitrate, lanthanum oxide and yttrium oxide.
The water-soluble zirconium salt can be selected from one or more of zirconium acetate, zirconium nitrate and zirconium chloride; preferably zirconium acetate. Based on the zirconia, the using amount of the water-soluble zirconium salt is 1-7 wt% of the total mass of the oxides in the oxidant slurry; preferably 2-6 wt%; more preferably 2 to 4 wt%. The mass fraction of solute in the water-soluble zirconium salt can be 15-30 wt%; preferably 17-25 wt%; more preferably 20 to 25 wt%. Thus, the ignition temperature of the catalyst is reduced, and the aging resistance and high temperature resistance of the catalyst are improved.
Step of preparing the catalyst
Mixing the third slurry with a binder to obtain a fourth slurry; and loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain the catalyst.
The binder can be one or more selected from aluminum sol, pseudo-boehmite, silica sol, cellulose, citric acid, polyvinyl alcohol and polyethylene glycol. Preferably, the binder is selected from one or more of aluminum sol, pseudo-boehmite, silica sol. More preferably, the binder is an aluminum sol. The using amount of the binder is 45-75 wt% of the mass of the oxide in the oxide slurry; preferably 50 to 70 wt%; more preferably 55 to 65 wt%.
The drying temperature can be 90-130 ℃; preferably 100-130 ℃; more preferably 100 to 120 ℃. The drying time can be 2-6 h; preferably 2-5 h; more preferably 2 to 4 hours.
The roasting temperature can be 500-750 ℃; preferably 500-700 ℃; more preferably 500 to 600 ℃. The roasting time can be 2-6 h, preferably 2-5 h; more preferably 2 to 4 hours.
The total load capacity of each element in the fourth slurry on the cordierite honeycomb ceramic carrier is 150-180 g/L calculated by oxide; preferably 150-170 g/L; more preferably 155 to 165 g/L.
Step of high temperature treatment
The preparation process of the catalyst of the present invention may comprise the steps of:
(1) mixing the oxide slurry with tungstate to form a first slurry; adding a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt to the first slurry to form a second slurry;
(2) mixing the second slurry, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt to obtain third slurry;
(3) mixing the third slurry with a binder to obtain a fourth slurry; loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain a roasted product;
(4) and (3) treating the roasted product at the high temperature of 700-1000 ℃ for 1-8 h to obtain the catalyst.
Wherein the oxide slurry contains alumina and at least one oxide selected from cerium oxide and zirconium oxide.
Steps (1) to (4) are as described above. In the step (5), the temperature of the high-temperature treatment can be 700-1000 ℃, preferably 800-950 ℃, and more preferably 800-900 ℃. The time of the high-temperature treatment can be 1-8 h, preferably 1-6 h, and more preferably 2-5 h. This is advantageous in reducing the light-off temperature of the catalyst.
< catalyst >
The catalyst of the invention is prepared by the process. The corresponding temperature of the fresh catalyst to the CO conversion rate of 50% is 140-180 ℃; preferably 150-180 ℃; more preferably 160 to 170 ℃. The temperature of the aged catalyst is 140-180 ℃ when the CO conversion rate is 50%; preferably 160-175 ℃; more preferably 160 to 165 ℃. The temperature corresponding to the CO conversion rate of the catalyst after high-temperature treatment is 140-180 ℃; preferably 150-175 ℃; more preferably 155 to 165 ℃. Fresh catalyst pair C3H6The temperature is 180-195 ℃ when the conversion rate is 50%; preferably 185-195 ℃; more preferably 185 to 190 ℃. Catalysis in the aged stateAgent pair C3H6The temperature is 170-195 ℃ when the conversion rate is 50%; preferably 180-190 ℃; more preferably 180 to 185 ℃. Catalyst pair C after high-temperature treatment3H6The temperature is 170-195 ℃ when the conversion rate is 50%; preferably 180-190 ℃; more preferably 180 to 185 ℃.
The test conditions were as follows:
the test was carried out in a fixed bed reactor under the following reaction conditions: CO 200ppm and C3H6＝180ppm、NO＝500ppm、CO2＝10vol％、O2＝10vol％，H2O＝7vol％、N2For balancing gas, the total flow is 550ml/min, and the space velocity is 80000h-1(ii) a The reaction temperature range is 100-500 ℃.
Aging conditions are as follows: h2O is 10 vol% and the space velocity is 60000h-1The aging temperature is 650 ℃, and the aging time is 100 hours;
high-temperature treatment conditions: roasting at 800 deg.c for 3 hr.
< uses of the composition >
The invention also provides the use of a composition for reducing the light-off temperature of a catalyst after high temperature treatment. The composition comprises tungstate, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt. In certain embodiments, the composition consists of a tungstate salt, a water soluble lanthanum salt, a water soluble yttrium salt, and a water soluble zirconium salt.
The high-temperature treatment condition is that the high-temperature treatment is carried out for 1-8 h at 700-1000 ℃. Preferably, the high-temperature treatment is carried out for 1 to 6 hours at the temperature of 800 to 950 ℃. More preferably, the high temperature treatment is carried out at 800-900 ℃ for 2-5 h.
The tungstate may be selected from one or more of ammonium tungstate, ammonium metatungstate, and ammonium paratungstate. Preferably, the tungstate is ammonium metatungstate. Calculated by tungsten trioxide, the usage amount of the tungstate is 0.5-5 wt% of the total mass of the oxides in the oxidant slurry; preferably 1 to 4 wt%; more preferably 1 to 3 wt%.
Based on lanthanum oxide, the dosage of lanthanum element is 0.5-5 wt% of the total mass of oxides in the oxidant slurry; preferably 1 to 4 wt%; more preferably 1 to 3 wt%. Based on yttrium oxide, the dosage of yttrium element is 0.5-5 wt% of the total mass of the oxide in the oxidant slurry; preferably 1 to 4 wt%; more preferably 1 to 3 wt%. The lanthanum element is calculated by lanthanum oxide, the yttrium element is calculated by yttrium oxide, and the mass ratio of the lanthanum element to the yttrium element can be 1 (0.5-2); preferably 1 (0.5-1.5); more preferably 1 (1-1.5). Thus, the ignition temperature of the catalyst is reduced, and the aging resistance and high temperature resistance of the catalyst are improved.
The water-soluble lanthanum salt and the water-soluble yttrium salt can be nitrate, sulfate, acetate or chloride. Examples of water soluble lanthanum salts, water soluble yttrium salts include, but are not limited to: lanthanum chloride, yttrium chloride, lanthanum nitrate, yttrium nitrate, lanthanum oxide and yttrium oxide.
The water-soluble zirconium salt can be selected from one or more of zirconium acetate, zirconium nitrate and zirconium chloride; preferably zirconium acetate. Based on the zirconia, the using amount of the water-soluble zirconium salt is 1-7 wt% of the total mass of the oxides in the oxidant slurry; preferably 2-6 wt%; more preferably 2 to 4 wt%. The mass fraction of solute in the water-soluble zirconium salt can be 15-30 wt%; preferably 17-25 wt%; more preferably 20 to 25 wt%. Thus, the ignition temperature of the catalyst is reduced, and the aging resistance and high temperature resistance of the catalyst are improved.
In some embodiments, the method specifically comprises the following steps:
(1) mixing the oxide slurry with tungstate to form a first slurry; adding a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt to the first slurry to form a second slurry;
(2) mixing the second slurry, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt to obtain third slurry;
(3) mixing the third slurry with a binder to obtain a fourth slurry; and loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain the catalyst.
In some embodiments, the method specifically comprises the following steps:
(1) mixing the oxide slurry with tungstate to form a first slurry; adding a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt to the first slurry to form a second slurry;
(2) mixing the second slurry, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt to obtain third slurry;
(3) mixing the third slurry with a binder to obtain a fourth slurry; loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain a roasted product;
(4) and (3) treating the roasted product at the high temperature of 700-1000 ℃ for 1-8 h to obtain the catalyst.
The parameters of the above steps and the parameters of the raw materials are as described above.
The following raw materials are introduced:
the cerium-zirconium solid solution contained zirconium in an amount of 60 wt% (in terms of zirconium oxide) and cerium in an amount of 40 wt% (in terms of cerium oxide).
The mass fraction of palladium element in the palladium nitrate solution was 17.4 wt%.
The mass fraction of platinum element in the platinum nitrate solution was 17.7 wt%.
The mass fraction of zirconium acetate in the zirconium acetate solution is 22 wt%.
Example 1
766g of alumina, 87g of cerium-zirconium solid solution and water are uniformly mixed to form mixed slurry (the solid content is 35 wt%); and ball-milling the mixed slurry until the average particle size of solid particles in the mixed slurry is 5 mu m to obtain oxide slurry. To the oxide slurry, 23g of ammonium metatungstate was added to form a first slurry. To the first slurry in a stirred state, 13g of a palladium nitrate solution and 25.6g of a platinum nitrate solution were added dropwise, respectively, to obtain a second slurry.
To the second slurry were added 53g of lanthanum nitrate, 68g of yttrium nitrate and 318g of a zirconium acetate solution to obtain a third slurry.
To the third slurry was added 500g of an aluminum sol to obtain a fourth slurry. Immersing the cordierite honeycomb ceramic carrier into the fourth slurry, taking out and blowing and sweeping redundant slurry; then drying at 110 ℃ for 3h, and roasting the dried cordierite honeycomb ceramic at 550 ℃ for 3h to obtain a catalyst (the loading amount of the catalyst is 160g/L in terms of oxide, and the total loading amount of palladium element and platinum element is 25 g/ft)3Of palladiumThe elements are calculated as palladium simple substance, and the platinum element is calculated as platinum simple substance).
Example 2
766g of alumina, 87g of cerium-zirconium solid solution and water are uniformly mixed to form mixed slurry (the solid content is 35 wt%); and ball-milling the mixed slurry until the average particle size of solid particles in the mixed slurry is 5 mu m to obtain oxide slurry. To the oxide slurry, 23g of ammonium metatungstate was added to form a first slurry. To the first slurry in a stirred state, 13g of a palladium nitrate solution and 25.6g of a platinum nitrate solution were added dropwise, respectively, to obtain a second slurry.
To the second slurry were added 53g of lanthanum nitrate, 68g of yttrium nitrate and 318g of a zirconium acetate solution to obtain a third slurry.
To the third slurry was added 500g of an aluminum sol to obtain a fourth slurry. Immersing the cordierite honeycomb ceramic carrier into the fourth slurry, taking out and blowing and sweeping redundant slurry; then drying at 110 ℃ for 3h, and roasting the dried cordierite honeycomb ceramic at 550 ℃ for 3h to obtain a roasted product.
And placing the roasted product in a muffle furnace, and roasting for 3 hours at 800 ℃ to obtain the catalyst. T of catalyst50(CO) 160 ℃; t is50(C3H6) The temperature was 181 ℃.
Comparative example 1
894g of alumina, 99g of a cerium-zirconium solid solution and water are uniformly mixed to form mixed slurry (the solid content is 35 wt%); and ball-milling the mixed slurry until the average particle size of solid particles in the mixed slurry is 5 mu m to obtain oxide slurry. To the oxide slurry in a stirred state, 13g of a palladium nitrate solution and 25.6g of a platinum nitrate solution were added dropwise, respectively, to obtain a first slurry.
To the first slurry was added 500g of an aluminum sol to obtain a second slurry. Immersing the cordierite honeycomb ceramic carrier into the second slurry, taking out and purging redundant slurry; then drying at 110 ℃ for 3h, and roasting the dried cordierite honeycomb ceramic at 550 ℃ for 3h to obtain a catalyst (the loading amount of the catalyst is 160g/L in terms of oxide, and the total loading amount of palladium element and platinum element is 25 g/ft)3The palladium element is calculated as palladium simple substance, and the platinum element is calculated as platinum simple substance)。
Comparative example 2
809g of alumina, 94g of cerium-zirconium solid solution and water are uniformly mixed to form mixed slurry (the solid content is 35 wt%); and ball-milling the mixed slurry until the average particle size of solid particles in the mixed slurry is 5 mu m to obtain oxide slurry. To the oxide slurry in a stirred state, 13g of a palladium nitrate solution and 25.6g of a platinum nitrate solution were added dropwise, respectively, to obtain a first slurry.
To the first slurry were added 53g of lanthanum nitrate and 68g of yttrium nitrate to obtain a second slurry.
To the second slurry was added 500g of an aluminum sol to obtain a third slurry. Immersing the cordierite honeycomb ceramic carrier into the third slurry, taking out and purging redundant slurry; then drying at 110 ℃ for 3h, and roasting the dried cordierite honeycomb ceramic at 550 ℃ for 3h to obtain a catalyst (the loading amount of the catalyst is 160g/L in terms of oxide, and the total loading amount of palladium element and platinum element is 25 g/ft)3Palladium element is calculated as palladium simple substance, and platinum element is calculated as platinum simple substance).
Examples of the experiments
The catalysts prepared in the above examples and comparative examples were tested for CO and C3H6The temperature at which the conversion is 50%.
The test was carried out in a fixed bed reactor under the following reaction conditions: CO 200ppm and C3H6＝180ppm、NO＝500ppm、CO2＝10vol％、O2＝10vol％，H2O＝7vol％、N2For balancing gas, the total flow is 550ml/min, and the space velocity is 80000h-1(ii) a The reaction temperature range is 100-500 ℃.
Aging conditions are as follows: h2O is 10 vol% and the space velocity is 60000h-1The aging temperature is 650 ℃, and the aging time is 100 h.
High-temperature treatment conditions: the high temperature treatment was carried out in a muffle furnace and calcined at 800 ℃ for 3 h. The test results are shown in table 1.
TABLE 1
Figure BDA0002643964600000141
The present invention is not limited to the above-described embodiments, and any variations, modifications, and substitutions which may occur to those skilled in the art may be made without departing from the spirit of the invention.

Claims (10)

1. A preparation process of a catalyst for diesel vehicle tail gas is characterized by comprising the following steps:
(1) mixing the oxide slurry with tungstate to form a first slurry; adding a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt to the first slurry to form a second slurry;
(2) mixing the second slurry, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt to obtain third slurry;
(3) mixing the third slurry with a binder to obtain a fourth slurry; loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain a catalyst;
wherein the oxide slurry contains alumina and at least one oxide selected from cerium oxide and zirconium oxide.
2. The preparation process according to claim 1, wherein the amount of the tungstate is 0.5 to 5 wt% of the total mass of the oxides in the oxide slurry, calculated as tungsten trioxide; the tungstate is selected from one or more of ammonium tungstate, ammonium metatungstate or ammonium paratungstate.
3. The process according to claim 1, wherein the oxide slurry contains alumina, zirconia, and ceria, and the mass ratio of ceria, zirconia, and alumina is (0.01 to 0.07): 0.04 to 0.09):1, and the mass ratio of ceria and zirconia is (1 to 4): 2 to 5.
4. The process of claim 1, wherein a solution containing a water-soluble palladium salt and a water-soluble platinum salt is added to the first slurry to form a second slurry;
taking a substrate of a cordierite honeycomb ceramic carrier as a reference, and the load capacity of platinum element is 8-25 g/ft3The loading amount of palladium element is 3-12 g/ft3(ii) a The mass ratio of the platinum element to the palladium element is (1-4) to 1; wherein, the platinum element is calculated by a platinum simple substance, and the palladium element is calculated by a palladium simple substance.
5. The preparation process according to claim 1, wherein the lanthanum is used in an amount of 0.5 to 5 wt% based on the total mass of the oxides in the oxide slurry; based on yttrium oxide, the dosage of yttrium element is 0.5-5 wt% of the total mass of the oxide in the oxidant slurry.
6. The process according to claim 1, wherein the water-soluble zirconium salt is used in an amount of 1 to 7 wt% based on the total mass of the oxides in the oxidizer slurry.
7. The preparation process according to any one of claims 1 to 6, wherein the binder is selected from one or more of aluminum sol, pseudo-boehmite, silica sol, cellulose, citric acid, polyvinyl alcohol and polyethylene glycol;
the drying temperature is 90-130 ℃, and the drying time is 2-6 h; the roasting temperature is 500-800 ℃, and the roasting time is 2-6 h;
the total load capacity of each element in the fourth slurry on the cordierite honeycomb ceramic carrier is 150-180 g/L in terms of oxide.
8. A preparation process of a catalyst for diesel vehicle tail gas is characterized by comprising the following steps:
(1) mixing the oxide slurry with tungstate to form a first slurry; adding a solution containing a water-soluble palladium salt and/or a water-soluble platinum salt to the first slurry to form a second slurry;
(2) mixing the second slurry, water-soluble lanthanum salt, water-soluble yttrium salt and water-soluble zirconium salt to obtain third slurry;
(3) mixing the third slurry with a binder to obtain a fourth slurry; loading the fourth slurry on a cordierite honeycomb ceramic carrier, and then drying and roasting to obtain a roasted product;
(4) treating the roasted product at 700-1000 ℃ for 1-8 h to obtain a catalyst;
wherein the oxide slurry contains alumina and at least one oxide selected from cerium oxide and zirconium oxide.
9. A catalyst for diesel vehicle exhaust, characterized in that it is obtained by the preparation process according to any one of claims 1 to 7;
the temperatures of the fresh catalyst, the aged catalyst and the high-temperature treated catalyst which correspond to the CO conversion rate of 50 percent are 140-180 ℃, 140-180 ℃ and 140-180 ℃ respectively;
fresh catalyst, aged catalyst and high-temperature treated catalyst pair C3H6The corresponding temperatures are 180-195 ℃, 170-195 ℃ and 170-195 ℃ respectively when the conversion rate is 50%;
the test was carried out in a fixed bed reactor under the following reaction conditions: CO 200ppm and C3H6＝180ppm、NO＝500ppm、CO2＝10vol％、O2＝10vol％，H2O＝7vol％、N2For balancing gas, the total flow is 550ml/min, and the space velocity is 80000h-1(ii) a The reaction temperature range is 100-500 ℃; the aging conditions were: h2O is 10 vol% and the space velocity is 60000h-1The aging temperature is 650 ℃, and the aging time is 100 hours; the high-temperature treatment conditions are as follows: roasting at 800 deg.c for 3 hr.
10. Use of a composition for reducing the light-off temperature of a high temperature treated diesel exhaust catalyst, wherein the composition comprises a tungstate salt, a water soluble lanthanum salt, a water soluble yttrium salt, and a water soluble zirconium salt; the high-temperature treatment conditions are as follows: high-temperature treatment is carried out for 1-8 h at 700-1000 ℃.
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