CN103877994A - Metal honeycomb carrier ternary catalyst of minitype general gasoline engine as well as preparation method thereof - Google Patents

Abstract

The invention relates to the field of general gasoline engine tail gas purification treatment, and particularly relates to a ternary catalyst for minitype general gasoline engine tail gas purification as well as a preparation method thereof. The ternary catalyst is characterized in that an iron chromium aluminum metal honeycomb is taken as an inert carrier, a cerium oxide carrier with the specific surface area of 100-200 m<2>/g is adopted, platinum, palladium and rhodium are taken as active components and rear-earth metal oxides are taken as auxiliaries; heat-resisting oxide is theta-aluminum oxide with the specific surface area of 120-200 m<2>/g, and theta-aluminum oxide is stabilized by 3wt%-8wt% of lanthanum; the cerium oxide carrier is of a film shape; platinum and palladium in the active components are loaded on the cerium oxide carrier and subjected to roasting for curing, rhodium in the active components is loaded on theta-aluminum oxide, and the mass ratio of theta-aluminum oxide to cerium oxide to the auxiliaries is (5-40):100:(11-30). The ternary catalyst for the minitype general gasoline engine according to the technical scheme provided by the invention is high in tail gas hydrocarbon compound conversion efficiency, and high in thermal-resisting stability.

Description

Small utility gasoline engine ternary catalyst for metal honeycomb carrier and preparation method

Technical field

The present invention relates to general gasoline engines tail gas clean-up process field, be specifically related to a kind of three-way catalyst for small utility gasoline engine tail gas clean-up and preparation method thereof.

Background technology

Small utility gasoline engine is the same with gasoline car, harmful substance in tail gas is mainly carbon monoxide, nitrogen oxide and hydrocarbon, current most widely used exhaust gas treating method installs exactly three-way catalyst additional and carries out external purification, it utilizes the synergy of noble metal and other rare earth materials, in the situation that controlling air-fuel ratio, the above-mentioned three kinds of harmful substances of purified treatment simultaneously, particularly hydrocarbon wherein, due to the acoustic wave filter structure compactness of small utility gasoline engine, small volume, requires Catalyst Conversion high conventionally.

The generally fluctuation between 500～600 DEG C of small utility gasoline engine operating temperature, occasional reaches more than 1000 DEG C, under such high temperature, can cause as the activated alumina generation heat fade phase transformation of catalyst carrier and then cause that pore volume shrinks, particularly in having water vapour to exist, be adsorbed on the area that pore volume shrinks catalysis material on mounting medium and also can lose a part of catalyst surface, correspondingly catalytic activity also can reduce.

In order to improve the exhaust purification efficiency of catalyst, develop and dropped into actual use containing the three-way catalyst of hydrogen-storing material.By the effect of hydrogen-storing material, three-way catalyst containing hydrogen-storing material stores the oxygen that is contained in waste gas in the time of lean burn condition, and the oxygen that release stores in the time of fuel-rich state, three-way catalyst containing hydrogen-storing material has the structure of noble-metal-supported on cerium oxide or other particulates, but the heat aging performance of the composite oxides of oxidation-containing cerium or cerium oxide and zirconium is poor, in Heat Ageing, composite particles is grown up and is caused specific area decay and oxygen storage capacity to decline, because cerium oxide particle is grown up, the noble metal loading on cerium oxide particle is assembled and sintering, reduce the exhaust-gas purifying performance of self.In addition because alumina support has irregular surface, the noble metal that loads on alumina support duct in cerium oxide layer may be by embedding completely, and result is to cause the specific area of catalyst acutely to decay.

Summary of the invention

One of object of the present invention is to provide a kind of tail gas hydrocarbon transformation efficiency high, the small utility gasoline engine three-way catalyst that heat-resistant stability is high.

In order to reach this purpose, the invention provides a kind of small utility gasoline engine ternary catalyst for metal honeycomb carrier, taking iron-chromium-aluminum metal honeycomb as inert carrier, taking specific area as 100～200m ²the cerium oxide carrier of/g, platinum, palladium, rhodium is active component, and rare-earth oxide is auxiliary agent, and wherein refractory oxides is θ-aluminium oxide, its specific area 120～200m ²/ g, 3～8%(weight ratio for this θ-aluminium oxide) lanthanum stabilisation, described cerium oxide carrier is film-form, the platinum of described active component, palladium loads on cerium oxide carrier and through roasting and solidifies, the rhodium of described active component loads on θ-aluminium oxide, and described θ-aluminium oxide, cerium oxide, auxiliary agent mass ratio are: 5～40:100:11～30.

Because the hydrogen-storing material that contains cerium oxide is with the form application of film, the material of preparation has high specific area, in heating process cerium oxide particle not there is not corresponding growing up, thereby suppressed the decay of cerium oxide specific area.

Another object of the present invention is to provide the preparation method of above-mentioned three-way catalyst, specifically includes following steps:

1) metal beehive carrier pretreatment: in supersonic wave cleaning machine, iron-chromium-aluminum metal honeycomb is cleaned with deionized water and industrial degreasing agent, then dry 0.5～2 hour at 100～180 DEG C, again iron-chromium-aluminum metal honeycomb is carried out to surface high-temp oxidation processes, temperature is 720～1000 DEG C, and the time is 2～5 hours.

2) preparation of high-specific surface area cerium oxide carrier material: the cerous nitrate that takes stoichiometric proportion, zirconium nitrate, lanthanum nitrate, yttrium nitrate, be made into certain concentration solution, then add a certain amount of small organic molecule complexing agent to form metal complex, last metal complex and aluminium oxide effect, after airflow milling is repeatedly dried pulverizing, obtain high specific surface cerium carrier, specific area is 100～200m ²/ g.

3) grained catalyst preparation: by active component palladium, platinum difference oxide impregnation cerium carrier, active component rhodium is impregnated on the θ-aluminium oxide of 3～8% lanthanum stabilisations to θ-aluminium oxide specific area 120～200m ²/ g, dip time is 4～6 hours, then dries respectively 4～7 hours at 80～200 DEG C, difference roasting 3～6 hours at the temperature of 300～600 DEG C, to realize active component in the dispersion of carrier surface and to solidify.

4) transition zone slurry preparation: transition zone adopts boehmite ([AlOOH] 3H2O) at room temperature to react with the diluted nitric acid aqueous solution of 1-3N, regulate PH 2～4, making solid content is 25～40% slurries, particle mean size is at 1～1.5um, the slurry of preparation is mixed with auxiliary agent, and ball milling obtains transition zone slurry.

5) coating of transition zone: dry and roasting: the iron-chromium-aluminum metal honeycomb that step 1 is obtained is impregnated in transition zone slurry, coating coated weight control range is 20～40g/l, coating layer thickness is 5～20um, adopt negative pressure to remove unnecessary slurry in inert carrier, the iron-chromium-aluminum metal honeycomb that has applied transition zone slurry is dried to 4～7 hours at 150～220 DEG C, then roasting 3～26 hours at 600～2900 DEG C, makes curing of coatings on iron-chromium-aluminum metal honeycomb.

6) preparation of active layer slurry: the cerium oxide carrier that step 3 is obtained, add appropriate amount of deionized water, form wet solid, through ball mill ball milling, making solid content is 22～50% slurries, prepared slurry is acid, and pH value is about 2～7, and the pH value of slurry can regulate by add enough inorganic or organic acids in slurry.

7) active layer applies, dry and roasting: the iron-chromium-aluminum metal honeycomb that step 5 is obtained is impregnated in active coating slurry, catalyst coat coated weight control range is 40～150g/l, coating layer thickness is 5～50um, adopt negative pressure to remove unnecessary slurry in inert carrier, then inert carrier is dried to 4～7 hours at 80～200 DEG C, then at 300～600 DEG C, roasting makes catalyst coat be solidificated in transition zone coating for 3～6 hours.

Three-way catalyst prepared by the inventive method, compared with the catalyst of prior art, aspect the HC of catalyst of the present invention conversion ratio and temperature stability, has obtained remarkable improvement.After 1000 DEG C of hydrothermal agings, the HC transformation efficiency of catalyst is higher than 90%, temperature stability excellence.

Detailed description of the invention

The invention provides a kind of small utility gasoline engine ternary catalyst for metal honeycomb carrier and preparation method, taking iron-chromium-aluminum metal honeycomb as the first carrier, specific surface is 100～200m ²the cerium oxide of/g is Second support, and active component is platinum, palladium, rhodium; Refractory oxides is θ-aluminium oxide, and its specific area is 120～200m ²/ g; Complex rare-earth oxidate containing valuable metal is hydrogen-storing material, and auxiliary component is rare-earth oxide lanthanum, cerium, praseodymium, neodymium, zirconium, in yttrium at least one; Top layer catalyst activity component is platinum and rhodium, θ-aluminium oxide in catalyst, and containing cerium-based oxygen storage material, auxiliary agent mass ratio is: 5～40:100:11～30.

Above-mentioned three-way catalyst is prepared by method below:

1, metal beehive carrier pretreatment: clean in supersonic wave cleaning machine with deionized water and industrial degreasing agent, then dry 0.5～2 hour at 100～180 DEG C, again carrier is carried out to surface high-temp oxidation processes, to form compactness oxide-film, treatment temperature is 720～1000 DEG C, and the time is 2～5 hours.

2, the preparation of high-specific surface area cerium oxide carrier material: adopt sol-gal process to prepare high-specific surface area cerium oxide, possess and store accordingly oxygen ability, take the cerous nitrate of stoichiometric proportion, zirconium nitrate, lanthanum nitrate, yttrium nitrate, be made into 10～50% nitrate aqueous solutions, then add the small organic molecule complexing agent of 1.0～2.5 times of rare earth metal molal weight as citric acid, ethylenediamine tetra-acetic acid, tri-butylamine forms metal complex, last metal complex and aluminium oxide effect, after airflow milling is repeatedly dried pulverizing, obtaining specific surface is 100～200m ²the cerium oxide carrier material of/g, wherein oxide ratios is cerium oxide: zirconia: lanthana: yittrium oxide: aluminium oxide=10～40:3～20:2～8:2～5:50～80.

3, grained catalyst preparation: by active component palladium, platinum difference oxide impregnation cerium carrier, active component rhodium is impregnated on the θ-aluminium oxide of 3～8% lanthanum stabilisations to θ-aluminium oxide specific area 120～200m ²/ g, dip time is 4～6 hours, then dries respectively 4～7 hours at 80～200 DEG C, difference roasting 3～6 hours at the temperature of 300～600 DEG C, to realize active component in the dispersion of carrier surface and to solidify.

4) transition zone slurry preparation: transition zone adopts boehmite ([AlOOH] 3H2O) at room temperature to react with the diluted nitric acid aqueous solution of 1-3N, regulate PH 2～4, making solid content is 25～40% slurries, particle mean size is at 1～1.5um, by slurry and the auxiliary agent lanthanum nitrate of preparation, nickel nitrate, rare earth oxygen storage material one at least is wherein mixed, and ball milling obtains transition zone slurry.

5) coating of transition zone: dry and roasting: the iron-chromium-aluminum metal honeycomb that step 1 is obtained is impregnated in transition zone slurry, coating coated weight control range is 20～40g/l, coating layer thickness is 5～20um, adopt negative pressure to remove unnecessary slurry in inert carrier, the iron-chromium-aluminum metal honeycomb that has applied transition zone slurry is dried to 4～7 hours at 150～220 DEG C, then roasting 3～26 hours at 600～2900 DEG C, makes curing of coatings on iron-chromium-aluminum metal honeycomb.

6, the preparation of active layer slurry: will contain the grained catalyst of active component, containing cerium-based oxygen storage material, auxiliary agent acetic acid zirconium, barium acetate, neodymium nitrate, lanthanum nitrate, strontium nitrate, nickel nitrate wherein at least one, then add appropriate amount of deionized water, form wet solid, ball mill ball milling, making solid content is 22～50% slurries, and prepared slurry is acid, and pH value is about 2～7, the pH value of slurry can regulate by add enough inorganic or organic acids in slurry, also can consider to regulate with inorganic acid and organic acid the pH value of slurry simultaneously.Inorganic acid includes but not limited to nitric acid, and organic acid includes but not limited to, acetic acid, propionic acid, oxalic acid, malonic acid, butanedioic acid, glutamic acid, adipic acid, maleic acid, fumaric acid, phthalic acid, tartaric acid, citric acid etc.

7) active layer applies, dry and roasting: the iron-chromium-aluminum metal honeycomb that step 5 is obtained is impregnated in active coating slurry, catalyst coat coated weight control range is 40～150g/l, coating layer thickness is 5～50um, adopt negative pressure to remove unnecessary slurry in inert carrier, then inert carrier is dried to 4～7 hours at 80～200 DEG C, then at 300～600 DEG C, roasting makes catalyst coat be solidificated in transition zone coating for 3～6 hours, the catalyst activity component proportion obtaining is platinum: palladium: rhodium=2～5:5～100:1～5, active component content is 1.7～7.2g/l.

Inventor tests discovery to the catalyst performance of preparing by embodiment, compared with the catalyst of prior art, aspect the HC of catalyst of the present invention conversion ratio and temperature stability, obtain remarkable improvement, after 1000 DEG C of hydrothermal agings, the HC transformation efficiency of catalyst is higher than 90%, surface goes out excellent temperature stability, above-mentioned catalyst adds stainless steel casing and makes ternary cleaner, on small utility gasoline engine, carry out emission test through Tianjin Inst. of IC Engine, can meet EPA tri-stages discharge standard completely, test result is in table 2, table 3.

Catalyst performance test,

Burin-in process: pack catalyst into hydrothermal aging device, pass into the air containing 10% water vapour, 1000 DEG C aging 5 hours.

Activity rating: the evaluation of catalyst sample is carried out on laboratory simulation evaluating apparatus is tested air inlet and gas outlet tail gas concentration simultaneously, and fresh sample test result is in table 4, and ageing test result is in table 5.Simulation gas forms in table 1, and air speed is 60000h ^～1.

The small utility gasoline engine tail gas composition of table 1 simulation test

Table 2 fresh sample A/G1 cycle bleeder test result

125 hours aging rear sample A/G1 cycle bleeder test results of stand of table 3

Table 4 fresh sample initiation temperature

Initiation temperature after 1000 DEG C of 5 hours hydrothermal agings of table 5

Above-described is only the preferred embodiment of the present invention, and in scheme, the general knowledge such as known concrete component and characteristic is not done too much description at this.It should be pointed out that for a person skilled in the art, without departing from the inventive concept of the premise, can also make some improvement, these also should be considered as protection scope of the present invention, and these can not affect effect of the invention process and practical applicability.

Claims (2)

1. small utility gasoline engine ternary catalyst for metal honeycomb carrier, is characterized in that: taking iron-chromium-aluminum metal honeycomb as inert carrier, taking specific area as 100～200m ²the cerium oxide carrier of/g, platinum, palladium, rhodium is active component, and rare-earth oxide is auxiliary agent, and wherein refractory oxides is θ-aluminium oxide, its specific area 120～200m ²/ g, 3～8%(weight ratio for this θ-aluminium oxide) lanthanum stabilisation, described cerium oxide carrier is film-form, the platinum of described active component, palladium load on cerium oxide carrier and through roasting and solidify, the rhodium of described active component loads on θ-aluminium oxide, and described θ-aluminium oxide, cerium oxide, auxiliary agent mass ratio are: 5～40:100:11～30.

2. prepare the method for three-way catalyst as claimed in claim 1: it is characterized in that including following steps:

1) metal beehive carrier pretreatment: in supersonic wave cleaning machine, iron-chromium-aluminum metal honeycomb is cleaned with deionized water and industrial degreasing agent, then dry 0.5～2 hour at 100～180 DEG C, again iron-chromium-aluminum metal honeycomb is carried out to surface high-temp oxidation processes, temperature is 720～1000 DEG C, and the time is 2～5 hours;

2) preparation of high-specific surface area cerium oxide carrier material: the cerous nitrate that takes stoichiometric proportion, zirconium nitrate, lanthanum nitrate, yttrium nitrate, wiring solution-forming, then adds excessive small organic molecule complexing agent to form metal complex, last metal complex and the effect of θ-aluminium oxide, after airflow milling is repeatedly dried pulverizing, obtain high specific surface cerium carrier, specific area is 100～200m ²/ g;

3) grained catalyst preparation: by active component palladium, platinum difference oxide impregnation cerium carrier, active component rhodium is impregnated on the θ-aluminium oxide of 3～8% lanthanum stabilisations to θ-aluminium oxide specific area 120～200m ²/ g, dip time is 4～6 hours, then dries respectively 4～7 hours at 80～200 DEG C, difference roasting 3～6 hours at the temperature of 300～600 DEG C, to realize active component in the dispersion of carrier surface and to solidify;

4) transition zone slurry preparation: transition zone adopts boehmite ([AlOOH] 3H ₂o) at room temperature react with the diluted nitric acid aqueous solution of 1-3N, regulate PH 2～4, making solid content is 25～40% slurries, and particle mean size, at 1～1.5um, is mixed the slurry of preparation with auxiliary agent, and ball milling obtains transition zone slurry;

5) coating of transition zone: dry and roasting: the iron-chromium-aluminum metal honeycomb that step 1 is obtained is impregnated in transition zone slurry, coating coated weight control range is 20～40g/l, coating layer thickness is 5～20um, adopt negative pressure to remove unnecessary slurry in inert carrier, the iron-chromium-aluminum metal honeycomb that has applied transition zone slurry is dried to 4～7 hours at 150～220 DEG C, then roasting 3～26 hours at 600～2900 DEG C, makes curing of coatings on iron-chromium-aluminum metal honeycomb;

6) preparation of active layer slurry: the cerium oxide carrier that step 3 is obtained, add appropriate amount of deionized water, form wet solid, through ball mill ball milling, making solid content is 22～50% slurries, prepared slurry is acid, and pH value is about 2～7, and the pH value of slurry can regulate by add enough inorganic or organic acids in slurry;

7) active layer applies, dry and roasting: the iron-chromium-aluminum metal honeycomb that step 5 is obtained is impregnated in active coating slurry, catalyst coat coated weight control range is 40～150g/l, coating layer thickness is 5～50um, adopt negative pressure to remove unnecessary slurry in inert carrier, then inert carrier is dried to 4～7 hours at 80～200 DEG C, then at 300～600 DEG C, roasting makes catalyst coat be solidificated in transition zone coating for 3～6 hours.