JP6248243B2 - Thickener, slurry for exhaust gas purification catalyst, method for producing the same, and internal combustion engine - Google Patents

Description

  The present invention relates to a thickener, a slurry for exhaust gas purification catalyst, a method for producing an exhaust gas purification catalyst, and an internal combustion engine.

  Conventionally, in the preparation of an exhaust gas purification catalyst, in order to prevent dripping of the slurry for exhaust gas purification catalyst, a method of applying after increasing the viscosity by increasing the solid content concentration has been adopted. In addition, although the thinning agent for lowering | hanging the viscosity of the slurry for exhaust gas purification catalysts is known (for example, patent document 1), the thickening agent for raising this viscosity is not known.

JP 2014-105222 A

In order to prevent dripping of the slurry for exhaust gas purification catalyst, when applying after increasing the viscosity by increasing the solid content concentration, there is a problem that the exhaust gas catalyst layer cannot be thinned due to the high solid content concentration. is there.
This invention is providing the thickener excellent in the thickening effect which can make a viscosity high, without making solid content concentration of the slurry for exhaust gas purification catalysts high.

The thickener of the present invention is characterized in that it is a thickener for increasing the viscosity of a slurry for exhaust gas purification catalyst containing a heat-resistant inorganic oxide supporting a noble metal and a dispersion medium,
It comprises a (co) polymer comprising at least one selected from the group consisting of acrylic acid, ammonium acrylate and amine acrylate as an essential constituent monomer (a),
The gist is that the weight average molecular weight of the (co) polymer is 6 × 10 ³ to 1.4 × 10 ⁴ .

  A feature of the slurry for exhaust gas purification catalyst of the present invention is that it comprises the above thickener, a heat-resistant inorganic oxide carrying a noble metal, and a dispersion medium.

  A feature of the method for producing an exhaust gas purifying catalyst of the present invention is that a slurry is obtained by uniformly mixing and dispersing the above thickener, a heat-resistant inorganic oxide supporting a noble metal, and a dispersion medium, and a base material. The gist includes a coating step (2) for applying a slurry to obtain a coated substrate, and a drying and firing step (3) for drying and firing the coated substrate to obtain an exhaust gas purification catalyst.

The feature of the manufacturing method of the internal combustion engine of the present invention is that the exhaust gas purifying catalyst manufactured by the above manufacturing method is mounted.

  The thickener of the present invention can effectively increase the viscosity of a slurry for an exhaust gas purification catalyst containing a heat-resistant inorganic oxide supporting a noble metal and a dispersion medium (that is, excellent in the thickening effect). Therefore, when the thickener of the present invention is used, the viscosity can be increased without increasing the solid content concentration of the slurry for exhaust gas purification catalyst, and the exhaust gas catalyst layer can be made thinner.

  Since the slurry for exhaust gas purification catalyst of the present invention uses the above thickener, the viscosity can be effectively increased and the exhaust gas catalyst layer can be made thin without increasing the solid content concentration.

  Since the manufacturing method of the exhaust gas purification catalyst of the present invention uses the above thickener, the viscosity can be effectively increased, and the exhaust gas catalyst layer can be made thin without increasing the solid content concentration of the slurry. it can.

  Since the internal combustion engine of the present invention uses the above thickener, the exhaust gas catalyst layer can be made thin.

It is the perspective view which showed typically the honeycomb type base material used in the Example.

<Thickener>
The amine that can constitute the acrylic acid amine salt that is the essential constituent monomer (a) may be any of primary, secondary, or tertiary amines (having 1 to 18 carbon atoms), methylamine, dimethylamine. , Trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, butylamine, dibutylamine, tributylamine, methylethylamine, methylpropylamine, methylbutylamine, ethylpropylamine, ethylbutylamine, propylbutylamine, dimethylethylamine Methyldiethylamine, dimethylpropylamine, methyldipropylamine, dimethylbutylamine, methyldibutylamine, diethylpropylamine, ethyldipropylamine, diethylbutylamine , Ethyldibutylamine, dipropylbutylamine, propyldibutylamine, phenylamine (aniline), diphenylamine, o-methylaniline, m-methylaniline, p-methylaniline, monoethanolamine, diethanolamine, triethanolamine, monopropanolamine , Dipropanolamine, tripropanolamine, 1-amino-2-methylpropanol, 2-amino-2-methylpropanol, 1-aminobutanol, 2-aminobutanol, 3-aminobutanol, 4-aminobutanol, 2-methoxy Ethylamine, 2-ethoxyethylamine, 2-propoxyethylamine, 2-butoxyethylamine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-propoxypropylamine 3-butoxypropylamine, N-methylethanolamine, N, N-dimethylethanolamine, N-ethylethanolamine, N, N-diethylethanolamine, N-propylethanolamine, N, N-dipropylethanolamine, N -Butylethanolamine, N, N-dibutylethanolamine, N-methylpropanolamine, N, N-dimethylpropanolamine, N-ethylpropanolamine, N, N-diethylpropanolamine, N-propylpropanolamine, N, N -Dipropylpropanolamine, N-butylpropanolamine, N, N-dibutylpropanolamine, N-methylbutanolamine, N, N-dimethylbutanolamine, N-ethylbutanolamine, N, N-diethylbutanolamine Min, N-propylbutanolamine, N, N-dipropylbutanolamine, N-butylbutanolamine, N, N-dibutylbutanolamine and the like.

  Among the essential constituent monomers (a), acrylic acid, ammonium acrylate salt, acrylic acid N-methylethanolamine salt, acrylic acid N, N-dimethylethanolamine salt, and acrylic acid diethanolamine from the viewpoint of thickening effect, etc. Salts are preferable, and acrylic acid, ammonium acrylate, N-methylethanolamine acrylate, and diethanolamine acrylate are more preferable.

The (co) polymer may contain a comonomer (b) copolymerizable with the essential constituent monomer (a) as a constituent monomer.
Examples of the comonomer (b) include methacrylic acid, ammonium methacrylate, methacrylic acid amine salt, and (meth) acrylic acid alkyl ester.

  The amine that can constitute the methacrylic acid amine salt may be any of primary, secondary, and tertiary amines (having 1 to 18 carbon atoms), and examples thereof include the above amines.

  The alkyl group that can constitute the (meth) acrylic acid alkyl ester includes a linear alkyl group having 1 to 30 carbon atoms or a branched alkyl group.

  Linear alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, docosyl , Tricosyl, tetracosyl, heptacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl and triaconsil.

  Examples of the branched alkyl group include isopropyl, isobutyl, t-butyl, isopentyl, neopentyl, isohexyl, 2-ethylhexyl, isotridecyl, isooctadecyl, and isotriaconcyl.

  Of these alkyl groups, a linear alkyloxy group is preferable from the viewpoint of thickening effect and the like, more preferably a linear alkyl group having 1 to 18 carbon atoms, and particularly preferably methyl, ethyl and butyl.

  Among the comonomer (b), methacrylic acid, ammonium methacrylate and amine methacrylate are preferable from the viewpoint of thickening effect, and more preferably methacrylic acid and ammonium methacrylate.

  When the copolymerization monomer (b) is included as the constituent monomer of the (co) polymer, the content (mol%) of the essential constituent monomer (a) unit is the essential constituent monomer (a). Based on the number of moles of the unit and the comonomer (b) unit, 93 to 99 is preferable, and 96 to 98 is more preferable. In this case, if it is within this range, the thickening effect is further improved.

  When the comonomer (b) is included as a constituent monomer of the (co) polymer, the content (mol%) of the comonomer (b) unit is the essential constituent monomer (a). 1-7 are preferable based on the number of moles of the unit and the comonomer (b) unit, and more preferably 2-4. In this case, if it is within this range, the thickening effect is further improved.

  As a constituent monomer of the (co) polymer, in addition to the essential constituent monomer (a) and the comonomer (b), another monomer (c) can be included.

  Examples of the other monomer (c) include unsaturated carboxylic acids having 4 to 12 carbon atoms and salts thereof, olefins, ethylenically unsaturated nitriles, and ethylenically unsaturated amides.

  Examples of the unsaturated carboxylic acid having 4 to 12 carbon atoms include unsaturated monocarboxylic acids and unsaturated dicarboxylic acids.

  Unsaturated monocarboxylic acids include aliphatic unsaturated monocarboxylic acids, alicyclic unsaturated monocarboxylic acids and aromatic unsaturated monocarboxylic acids.

  Aliphatic unsaturated monocarboxylic acids include crotonic acid, 3-butenoic acid, 2-pentenoic acid, 3-pentenoic acid, 4-pentenoic acid, 3-methyl-2-butenoic acid, 3-methyl-3-butenoic acid 2-methyl-3-butenoic acid, 2-methyl-2-butenoic acid, 2-ethyl-2-propenoic acid, 2-hexenoic acid, 4-methyl-2-pentenoic acid, 2-methyl-2-pentenoic acid 2-heptenoic acid, 4,4-dimethyl-2-pentenoic acid, 2-octenoic acid, 3-methyl-2-heptenoic acid, 2-nonenoic acid, 3-methyl-2-octenoic acid, 2-decenoic acid and Examples include 2-hydroxypropenoic acid.

  Alicyclic unsaturated monocarboxylic acids include 1-cyclopentene carboxylic acid, 3-cyclopentene carboxylic acid, 4-cyclopentene carboxylic acid, 1-cyclohexene carboxylic acid, 3-cyclohexene carboxylic acid, 4-cyclohexene carboxylic acid, 1-cyclo Heptenecarboxylic acid, 3-cycloheptenecarboxylic acid, 4-cycloheptenecarboxylic acid, 5-cycloheptenecarboxylic acid, 1-cyclooctenecarboxylic acid, 3-cyclooctenecarboxylic acid, 4-cyclooctenecarboxylic acid, 5-cyclooctenecarboxylic acid, 1-cyclononenecarboxylic acid, 3-cyclononenecarboxylic acid, 4-cyclononenecarboxylic acid, 5-cyclononenecarboxylic acid, 1-cyclodecenecarboxylic acid, 3-cyclodecenecarboxylic acid, 4 -Cyclodecenecarboxylic acid and 5-cyclode Etc. Nkarubon acid, and the like.

  Aromatic unsaturated monocarboxylic acids include o-styrene carboxylic acid, p-styrene carboxylic acid, cinnamic acid, atropic acid, 5-vinyl-1-naphthalene carboxylic acid, 4-vinyl-1-naphthalene carboxylic acid and 4- Examples include vinyl-1-anthraquinone carboxylic acid.

  Examples of the unsaturated dicarboxylic acid include aliphatic unsaturated dicarboxylic acids, alicyclic unsaturated dicarboxylic acids, aromatic unsaturated dicarboxylic acids, and intramolecular acid anhydrides thereof.

  Examples of the aliphatic unsaturated dicarboxylic acid include maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, butenedioic acid, 2-pentenedioic acid, 3-pentenoic acid, 4-pentenoic acid, and 2-methyl-2- Butenedioic acid, 2-ethyl-2-propenoic acid, 2-hexenedioic acid, 2-heptenedioic acid, 2-octenoic acid, 3-methyl-2-heptenedioic acid, 2-nonenedioic acid, 2-dekendi And acid and 2-hydroxyptenelodioic acid.

  Examples of the alicyclic unsaturated dicarboxylic acid include 1,2-cyclopentene dicarboxylic acid, 1,3-cyclopentene dicarboxylic acid, 1,4-cyclopentene dicarboxylic acid, 1,2-cyclohexene dicarboxylic acid, 1,3-cyclohexene dicarboxylic acid, 1,4-cyclohexene dicarboxylic acid, 1,2-cycloheptene dicarboxylic acid, 1,3-cycloheptene dicarboxylic acid, 1,4-cycloheptene dicarboxylic acid, 1,5-cycloheptene dicarboxylic acid, 1, 2-cyclooctene dicarboxylic acid, 1,3-cyclooctene dicarboxylic acid, 1,4-cyclooctene dicarboxylic acid, 1,5-cyclooctene dicarboxylic acid, 1,2-cyclononene dicarboxylic acid, 1,3-cyclononene dicarboxylic acid Acid, 1,4-cyclononene dicarboxylic acid, 1,5-cyclononene dicarbo Examples include acid, 1,2-cyclodecenedicarboxylic acid, 1,3-cyclodecenedicarboxylic acid, 1,4-cyclodecenedicarboxylic acid, and 1,5-cyclodecenedicarboxylic acid.

  Examples of the aromatic unsaturated dicarboxylic acid include o, p-styrene dicarboxylic acid, o, p-styrene dicarboxylic acid, 4-vinyl-1,2-naphthalenedicarboxylic acid and 4-vinyl-1,3-anthraquinone dicarboxylic acid. Can be mentioned.

  Examples of intramolecular acid anhydrides of unsaturated dicarboxylic acids include maleic anhydride, itaconic anhydride, and citraconic anhydride.

  Unsaturated carboxylic acid salts include amine salts, ammonium salts and / or quaternary organic ammonium salts.

  Examples of the amine salt include salts of the above amines (primary, secondary or tertiary amine).

  As the quaternary organic ammonium salt, an organic ammonium salt having 4 to 8 carbon atoms can be used, such as tetramethylammonium salt, tetraethylammonium salt, trimethylethylammonium salt, N-methylpyridinium salt and N-methylimidazolium salt. Is mentioned.

  Examples of the olefin include α-olefins having 2 to 20 carbon atoms (ethylene, propylene, butylene, hexylene, octylene, undecylene, tetradecylene, and nonadecylene), diisobutylene, butadiene, piperylene, chloroprene, pinene, limonene, indene, and cyclopentadiene. , Bicyclopentadiene, ethylidene norbornene and the like.

  Examples of the ethylenically unsaturated nitrile include (meth) acrylonitrile, cyanopropene and cyanopentene.

  Examples of the ethylenically unsaturated amide include (meth) acrylamide, N-methyl (meth) acrylamide, N-2-hydroxymethyl (meth) acrylamide, N- (2-aminoethyl) (meth) acrylamide and N- (2- And dimethylaminoethyl) (meth) acrylamide.

  When the other monomer (c) is included as the constituent monomer of the (co) polymer, the content (mol%) of the other monomer (c) unit is the essential constituent monomer (a). Based on the number of moles of the unit, 0.1 to 8 is preferable, more preferably 0.5 to 6, but most preferably no other monomer (c) is contained.

The weight average molecular weight (Mw) of the (co) polymer is preferably 6 × 10 ³ to 2 × 10 ⁴ , more preferably 7 × 10 ^{3 to} 1.7 × 10 ⁴ , particularly preferably from the viewpoint of the thickening effect. Is 8 × 10 ^{3 to} 1.4 × 10 ⁴ .

  The weight average molecular weight (Mw) is measured by gel permeation chromatography (GPC) using (poly) ethylene glycol of known molecular weight as a standard substance (for example, column temperature 40 ° C., eluent methanol: ion exchange) Water: sodium acetate = 800: 1200: 15 (weight ratio), flow rate 0.8 ml / min, sample concentration: 0.4 wt% eluent solution.).

The number of moles (mol%) of the carboxyl group contained in the (co) polymer is preferably 20 to 70, more preferably 25 based on the number of moles of all monomer units constituting the (co) polymer. ˜65, particularly preferably 30˜60. Within this range, the thickening effect is further improved. Note that the carboxyl group, a group represented by -COOH, constitutes an ammonium salt or an amine salt carboxylate groups (-COO ^- group represented by) is not included.

  The (co) polymer can be obtained by using a usual polymerization method of vinyl monomers. As the polymerization method, suspension polymerization, bulk polymerization, solution polymerization and the like can be applied. From the viewpoint of productivity, solution polymerization can be performed. preferable.

  A polymerization catalyst can be used for the polymerization. As the polymerization catalyst, an ordinary polymerization catalyst or the like is used, and azo compounds, persulfates, inorganic peroxides, redox catalysts, and organic peroxides are included. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 4,4′-azobis-4-cyanovaleric acid, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile, 2, 2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-albonitrile), 2,2'-azobis (2,4,4-trimethylpentane), dimethyl 2,2 ' -Azobis (2-methylpropionate), 2,2'-azobis [2- (hydroxymethyl) propionitrile], 1,1'-azobis (1-acetoxy-1-phenylethane) and the like. Examples of the salt include ammonium persulfate, potassium persulfate, sodium persulfate, etc. Examples of the inorganic peroxide include perborate and hydrogen peroxide. Examples of the redox catalyst include ascorbic acid-hydrogen peroxide, etc. Examples of the organic peroxide include benzoyl peroxide, etc. These polymerization catalysts may be used alone or in combination. Of these, persulfates and azo compounds are preferred, more preferred are persulfates and 2,2′-azobisisobutyronitrile, and particularly preferred are ammonium persulfate, potassium persulfate, and sodium persulfate.

  When the polymerization catalyst is used, the amount (% by weight) of the polymerization catalyst is preferably 3 to 100, more preferably 8 to 80, and particularly preferably 10 to 60, based on the weight of the constituent monomer.

  Moreover, you may use the chain transfer agent for radical polymerization as needed. Chain transfer agents include thiocarboxylic acids (n-lauryl mercaptan, mercaptoethanol, mercaptopropanol, etc.), thiolic acids (thioglycolic acid, thiomalic acid, etc.), secondary alcohols (isopropanol, etc.), amines (dibutylamine, etc.) And hypophosphites (sodium hypophosphite, etc.).

  When the chain transfer agent is used, the amount (% by weight) of the chain transfer agent is preferably 0.01 to 10, more preferably 0.05 to 5, particularly preferably based on the weight of the constituent monomer. 0.1-1.

In the case of solution polymerization and suspension polymerization, the solvent includes water (tap water, ion exchange water, industrial water, etc.), alcohol solvent (methanol, ethanol, isopropyl alcohol, etc.) and / or aromatic solvent (toluene, xylene, etc.). Etc. can be used. Among these, water, a mixed solvent of water and an alcohol solvent are preferable, a mixed solvent of water and alcohol is more preferable, and a mixed solvent of ion-exchanged water and isopropyl alcohol is particularly preferable.
When a solvent is used, the amount (% by weight) used is preferably 50 to 900, more preferably 60 to 800, and particularly preferably 100 to 600, based on the total weight of the constituent monomers.

  The polymerization reaction temperature is preferably about 40 to 130 ° C., and the polymerization reaction time is preferably about 1 to 15 hours.

  In addition, you may superpose | polymerize, dripping the whole quantity or one part of a structural monomer. Moreover, you may superpose | polymerize, dripping the whole quantity or one part of a polymerization catalyst. Moreover, you may superpose | polymerize, dripping the whole quantity or one part of a solvent with a structural monomer or a polymerization catalyst. On the other hand, the entire amount of the solvent may be charged in a polymerization tank and polymerization may be performed while removing the solvent. Among these, from the viewpoint of productivity and the like, the method of dropping the whole amount of the constituent monomer and the polymerization catalyst and the method of dropping a part of the solvent together with the constituent monomer or the polymerization catalyst are preferable, and more preferably the constituent unit. In this method, the entire amount of the monomer and the polymerization catalyst is dropped together with a part of the solvent.

  The (co) polymer may be prepared by (co) polymerizing the essential constituent monomer (a) and, if necessary, the comonomer (b) and / or another monomer (c), Prepared by (co) polymerizing acrylic acid and, if necessary, methacrylic acid and / or other monomers (c) (unsaturated carboxylic acids remain unneutralized) and then neutralizing with ammonia and / or amine. May be.

The thickener of the present invention may contain other components (such as a surfactant and / or an aqueous solvent) in addition to the (co) polymer.
As the surfactant, a known surfactant of nonionic type, cationic type, anionic type or amphoteric type is included.

  Nonionic surfactants include alkylphenol alkylene oxide (alkylene oxide having 2 to 4 carbon atoms unless otherwise specified) adduct, higher fatty acid alkylene oxide adduct, polyhydric alcohol fatty acid ester, higher alkyl amine alkylene oxide. Examples include adducts, alkylene oxide adducts of higher fatty acid amides, alkylene oxide adducts of acetylene glycol, and polyoxyalkylene-modified silicones (polyether-modified silicones).

  Cationic surfactants include higher alkylamine salts, higher alkylamine alkylene oxide adducts, solomin A type cationic surfactants, sapamin A type cationic surfactants, Arcobel A type cationic surfactants, and imidazoline type cationic surfactants. Agents, higher alkyltrimethylammonium salts, higher alkyldimethylbenzylammonium salts, sapamine-type quaternary ammonium salts and pyridinium salts.

  Examples of the anionic surfactant include fatty acid salts, α-olefin sulfonates, alkylbenzene sulfonic acids and salts thereof, alkyl sulfate esters, alkyl ether sulfates, N-acyl alkyl taurates, and alkyl sulfosuccinates. It is done.

  Examples of amphoteric surfactants include higher alkylaminopropionates and higher alkyldimethylbetaines.

  When the surfactant is contained, the content (% by weight) is preferably 0.1 to 20, more preferably 0.5 to 10, particularly preferably 1 to 1, based on the weight of the (co) polymer. 5. Within this range, the thickening effect is further improved.

  Examples of the aqueous solvent include water, alcohols having 1 to 6 carbon atoms (such as ethyl alcohol, methyl alcohol, ethylene glycol and diethylene glycol), and ketones having 1 to 6 carbon atoms (such as methyl isobutyl ketone and acetone). You may use individually or in mixture.

  When the aqueous solvent is contained, the content (% by weight) is preferably 10 to 1000, more preferably 50 to 900, particularly preferably 100 to 600, based on the weight of the (co) polymer.

  When the thickener of the present invention contains other components, the thickener of the present invention is obtained by uniformly mixing (uniformly dissolving or uniformly dispersing) the (co) polymer and other components. can get.

The form of the thickener of the present invention is not particularly limited, and may be liquid or solid.
That the thickener is liquid means a state in which the (co) polymer and, if necessary, the surfactant are dissolved or dispersed in an aqueous solvent. In this case, the (co) polymer may be obtained by suspension polymerization or solution polymerization without removing all of the solvent, or the (co) polymer obtained by bulk polymerization or the like is dissolved or dispersed in an aqueous solvent. You may get it.

On the other hand, when the thickener is solid, it may be a solid comprising a (co) polymer, and a powder in which a liquid component {(co) polymer and, if necessary, other constituents} is supported on the powder It may be.
When the thickener is a solid comprising a (co) polymer, the (co) polymer may be obtained by bulk polymerization, or a solution or dispersion containing the (co) polymer may be obtained by suspension polymerization or solution polymerization. After obtaining, it may be obtained by removing the solvent.
As a method for removing the solvent from the solution or dispersion containing the (co) polymer, known methods such as a dry pulverization method, a freeze pulverization method, a spray dryer method, and a drum dryer method can be used. Of these, the dry pulverization method and the spray dryer method are preferred.

The solid size (mm; maximum length) is preferably 0.01 to 5, more preferably 0.05 to 3, particularly preferably 0.08 from the viewpoint of the solubility of the thickener of the present invention. ~ 1.
When the liquid component is supported on the powder, examples of the powder include heat-resistant inorganic oxides, activated carbon, calcium carbonate, zeolite, shirasu balloon, and bentonite described later.
As a method for supporting the liquid component on the powder, a method of stirring and mixing the powder and the liquid component using a known stirring mixer (such as a ribbon mixer and a Henschel mixer) can be applied.
Among the forms of the thickener, liquid is preferable, and more preferably, the (co) polymer is dissolved in an aqueous solvent.

  The thickener of the present invention can effectively increase the viscosity of a slurry for exhaust gas purification catalyst containing a heat-resistant inorganic oxide carrying a noble metal and a dispersion medium. Even if a material other than the thickener of the present invention is used, the viscosity of the slurry cannot be effectively increased. This is considered to be based on the kind of constituent monomer of the (co) polymer contained in the thickener of the present invention and the weight average molecular weight. For example, if the monomer constituting the (co) polymer is changed to another monomer, or the weight average molecular weight is out of the specified range, the effect of the present invention can no longer be obtained.

<Slurry for exhaust gas purification catalyst>
The heat-resistant inorganic oxide is not limited as long as it can support a noble metal without being deteriorated even at a high temperature (900 ° C. or higher), and includes at least one selected from the group consisting of zirconia, alumina, silica, titania, magnesia and ceria. Can be mentioned.

The volume average particle diameter (μm) of the heat-resistant inorganic oxide is preferably 0.1 to 100, more preferably 0.2 to 50, and particularly preferably 0.3 to 10 from the viewpoint of catalyst performance.
In addition, the volume average particle diameter is a laser diffraction particle size analyzer conforming to JIS Z8825-1: 2001 (for example, Microtrac Model No. manufactured by Lees & Northrup). MT3300EX}, a measurement dispersion prepared by adding a measurement sample to water so that the measurement sample concentration is 0.1% by weight, measured at a measurement temperature of 25 ± 5 ° C., and 50% cumulative volume average particle diameter As required.

As the noble metal, nitrogen oxide (NO _x ) can be reduced to nitrogen (N ₂ ), carbon monoxide (CO) can be oxidized to carbon dioxide (CO ₂ ), and hydrocarbon (hydrocarbon) can be converted to carbon dioxide and So-called three-way catalysts can be used without limitation as long as they can be oxidized to water, and examples thereof include platinum, palladium and rhodium.

  The amount (% by weight) of the noble metal supported can be appropriately determined depending on the type of exhaust gas, the amount of exhaust gas treated, etc., but is preferably 0.001 to 20 based on the weight of the heat-resistant inorganic oxide, and more preferably 0.01 to 15.

  As a method for supporting a noble metal on a heat-resistant inorganic oxide, a known method (for example, an impregnation method; a method of impregnating and supporting a catalyst metal solution on an inorganic oxide carrier such as alumina or silica) can be applied as it is. .

  Examples of the dispersion medium include water and a mixed solvent of water and a water-soluble organic solvent. Of these, water is preferred.

  Examples of the water-soluble organic solvent include alcohols having 1 to 3 carbon atoms (such as methanol, ethanol, isopropanol, ethylene glycol, and propylene glycol), ketones having 1 to 3 carbon atoms (such as acetone, methyl ethyl ketone, and dimethyl sulfoxide), and those having 4 to 4 carbon atoms. 6 ethers such as diethyl ether, tetrahydrofuran, dioxane, diethylene glycol and triethylene glycol.

  The content of the thickener is preferably such that the content (% by weight) of the (co) polymer is 0.01 to 15 based on the weight of the heat-resistant inorganic oxide supporting the noble metal, The amount is more preferably 0.05 to 10, and most preferably 0.1 to 5. Within this range, the thickening effect is further improved.

  The content (% by weight) of the dispersion medium can be appropriately determined depending on the catalyst specifications, but is preferably 50 to 90 based on the weight of the heat-resistant inorganic oxide.

  In the slurry for exhaust gas purification catalyst of the present invention, in addition to the above thickener, the heat-resistant inorganic oxide supporting the noble metal and the dispersion medium, other additives (antifoaming agent, thickener other than the thickener of the present invention) are added. (Viscous agent, dispersant, etc.) may be contained.

  As long as the slurry for exhaust gas purification catalyst of the present invention can uniformly mix and disperse the thickener, the heat-resistant inorganic oxide supporting the noble metal and the dispersion medium, the production method is not limited, and by slurrying with a known mixing and dispersing machine, Can be obtained. When slurrying, it can be appropriately sealed or cooled so that the solvent does not evaporate.

The viscosity (mPa · s, 25 ° C.) of the exhaust gas purifying catalyst slurry is preferably 50 to 400, more preferably 70 to 350, particularly preferably 100 to 300 when the shear rate is 380 s ⁻¹ , and the shear rate. Is 4 s ⁻¹ , 500 to 8000 is preferable, 800 to 7500 is more preferable, and 1000 to 7000 is particularly preferable.
The viscosity is measured using a rotational viscometer (for example, a rheometer Physica MCR301 (manufactured by Anton Paar)) at a shear rate of 380 s ⁻¹ or 4 s ⁻¹ .

<Method for producing exhaust gas purification catalyst>
In the slurrying step (1), the above thickener, the heat-resistant inorganic oxide supporting the noble metal, and the dispersion medium are uniformly mixed and dispersed to obtain a slurry. Can be done on the machine.

In the coating step (2), the base material has heat resistance (up to about 900 to 1000 ° C.) and is not limited as long as it has corrosion resistance (no corrosion against exhaust gas), and ceramics and stainless steel are preferable. Can be used for Examples of the ceramic include cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ). The shape of the substrate can be appropriately determined depending on the application.

  When the exhaust gas purification catalyst is for an internal combustion engine, the base material is preferably a monolith type base material that communicates between the inlet end side and the outlet end side, and more preferably communicates between the inlet end side and the outlet end side. It is a honeycomb type substrate.

As a coating method, there is no limitation as long as the coated substrate can be obtained by applying the slurry to the substrate.
When the base material is a monolith type base material that communicates between the inlet end side and the outlet end side, the coating step (2) is a transfer coating in which the slurry is applied by a method of transferring the slurry from the inlet end side toward the outlet end side. It may be a step (21) or a dip coating step (22) of coating by a method of immersing the substrate in the slurry. Of these, the transfer coating step (21) is preferable, and more preferably, the outlet end side is made more negative than the inlet end side, and the pressure difference between the inlet end side and the outlet end side causes the inlet end side to the outlet end side. This is a transfer coating process in which the slurry is coated by a method of transporting the slurry toward it. As the transfer coating step (21), the method disclosed in JP 2008-302304 A is a reference.
When the slurry is transferred by the pressure difference between the inlet end side and the outlet end side, the outlet end side may be depressurized, the inlet end side may be pressurized, and the outlet end side is depressurized. You may pressurize an end side.
The coating amount can be appropriately determined depending on the type of exhaust gas, the exhaust gas treatment amount, and the like.

  In the firing step (3), the drying conditions are not limited as long as the coated substrate can be dried, and known conditions (for example, 240 to 260 ° C., 0.5 to 2 hours) can be applied. The baking conditions are not limited as long as the coated substrate is dried and then baked to burn off the organic components, and those that can be oxidized can be oxidized. Known conditions (for example, 450 to 900 ° C., 0.5 to 2 hours) ) Is applicable.

The exhaust gas purification catalyst produced by the production method of the present invention can be applied without limitation as long as it is an exhaust gas to be purified, and is suitable for exhaust gas discharged from internal combustion engines, factories, industrial waste treatment plants, and the like. Of these, it is most suitable for exhaust gas discharged from an internal combustion engine.
The internal combustion engine equipped with the exhaust gas purification catalyst produced by the production method of the present invention can be installed in an automobile, a motorcycle, an agricultural machine, a civil engineering construction machine, or the like.

  Hereinafter, unless otherwise specified, “part” means “part by weight” and “%” means “% by weight”.

<Example 1>
200 parts of ion-exchanged water and 300 parts of isopropyl alcohol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, and while stirring these, 288 parts (4 mole parts) acrylic acid and 14 parts methacrylic acid (0 .16 mol parts) and 20 parts of 40% aqueous sodium persulfate aqueous solution were added dropwise from separate dropping lines at a constant rate over 3 hours and allowed to react in a sealed state. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the temperature was kept at 95 to 100 ° C. for 3 hours. Then, isopropyl alcohol was removed under reduced pressure while dropping (watering) 150 parts of ion exchange water at this temperature, and then cooled to 30 ° C. Subsequently, 185 parts (2.47 mol parts) of N-methylethanolamine was gradually added in portions while maintaining the temperature at 40 ° C. or lower with stirring. Then, it added with water and adjusted the density | concentration to 25% and obtained the thickener (1) (carboxyl group: 40.6 mol%) of this invention. The weight average molecular weight of the thickener (1) was 1.4 × 10 ⁴ .

<Example 2>
200 parts of ion-exchanged water, 240 parts of isopropyl alcohol and 0.2 part of 2-mercaptoethanol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirring device and a thermometer, and 165 parts of acrylic acid (2. 3 parts by mole) and 4 parts by weight of methacrylic acid (0.05 parts by mole) and 26 parts of 40% sodium persulfate aqueous solution were dropped from a separate dropping line at a constant rate over 3 hours, and sealed. It was made to react with. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the temperature was kept at 95 to 100 ° C. for 3 hours. Then, isopropyl alcohol was removed under reduced pressure while dropping (watering) 150 parts of ion exchange water at this temperature, and then cooled to 30 ° C. Subsequently, while maintaining the temperature at 40 ° C. or lower with stirring, 100 parts of 28% ammonia aqueous solution (1.64 mol parts of ammonia) was gradually added in portions. Then, it added water and adjusted the density | concentration to 25% and obtained the thickener (2) (carboxyl group: 30.2 mol%) of this invention. The thickener (2) had a weight average molecular weight of 1 × 10 ⁴ .

<Example 3>
200 parts of ion-exchanged water, 300 parts of isopropyl alcohol and 0.1 part of 2-mercaptoethanol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirring device and a thermometer, and 165 parts of acrylic acid (2. 3 parts by mole) and 4 parts by weight of methyl acrylate (0.05 parts by mole) and 32 parts of 40% aqueous sodium persulfate solution were dropped from each separate drop line at a constant rate for 3 hours and sealed. Reacted below. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the temperature was kept at 95 to 100 ° C. for 3 hours. Then, isopropyl alcohol was removed under reduced pressure while dropping (watering) 150 parts of ion exchange water at this temperature, and then cooled to 30 ° C. Subsequently, 94 parts (0.9 parts by mole) of diethanolamine was gradually added in portions while maintaining the temperature at 40 ° C. or lower with stirring. Then, it added with water and adjusted the density | concentration to 25% and obtained the thickener (3) (carboxyl group: 59.7 mol%) of this invention. The thickener (3) had a weight average molecular weight of 8 × 10 ³ .

<Example 4>
200 parts of ion-exchanged water and 300 parts of isopropyl alcohol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, and 250 parts (3.5 mole parts) of acrylic acid and 40% persulfuric acid are added while stirring these. 22 parts of an aqueous sodium solution were dropped from each separate dropping line at a constant rate over 3 hours, and reacted in a sealed state. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the temperature was kept at 95 to 100 ° C. for 3 hours. Then, isopropyl alcohol was removed under reduced pressure while dropping (watering) 150 parts of ion exchange water at this temperature, and then cooled to 30 ° C. Subsequently, 145 parts (1.4 mole parts) of diethanolamine was gradually added in portions while maintaining the temperature at 40 ° C. or lower with stirring. Then, it added water and adjusted the density | concentration to 25% and obtained the thickener (4) (carboxyl group: 60 mol%) of this invention. The thickener (4) had a weight average molecular weight of 1.4 × 10 ⁴ .

<Example 5>
200 parts of ion-exchanged water, 280 parts of isopropyl alcohol and 0.1 part of 2-mercaptoethanol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirring device and a thermometer, and 180 parts of acrylic acid (2. 5 mol parts) and 28 parts of 40% sodium persulfate aqueous solution were dropped from each separate dripping line at a constant rate over 3 hours, and reacted in a sealed state. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the temperature was kept at 95 to 100 ° C. for 3 hours. Then, isopropyl alcohol was removed under reduced pressure while dropping (watering) 150 parts of ion exchange water at this temperature, and then cooled to 30 ° C. Subsequently, 61 parts of 28% ammonia aqueous solution (1 mol part of ammonia) was gradually added in portions while maintaining the temperature at 40 ° C. or lower with stirring. Then, it added with water and adjusted the density | concentration to 25% and obtained the thickener (5) (carboxyl group: 60 mol%) of this invention. The thickener (5) had a weight average molecular weight of 9 × 10 ³ .

<Example 6>
200 parts of ion-exchanged water and 300 parts of isopropyl alcohol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer, and a thermometer, and 288 parts (4 parts by mole) of acrylic acid and 40% sodium persulfate aqueous solution are stirred. Twenty parts were dropped from each separate dropping line at a constant rate over 3 hours, and reacted in a sealed state. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the temperature was kept at 95 to 100 ° C. for 3 hours. Then, isopropyl alcohol was removed under reduced pressure while dropping (watering) 150 parts of ion exchange water at this temperature, and then cooled to 30 ° C. Subsequently, 96 parts of a 28% aqueous ammonia solution (1.6 mol parts of ammonia) were gradually added in portions while maintaining the temperature at 40 ° C. or lower with stirring. Then, it added with water and adjusted the density | concentration to 25% and obtained the thickener (6) (carboxyl group: 60 mol%) of this invention. The thickener (6) had a weight average molecular weight of 1.4 × 10 ⁴ .

<Example 7>
200 parts of ion-exchanged water, 250 parts of isopropyl alcohol and 0.2 part of 2-mercaptoethanol are put into a pressure-resistant reaction vessel equipped with a dropping line, a stirrer and a thermometer, and 144 parts of acrylic acid (2 moles) while stirring them. Part) and 30 parts of 40% sodium persulfate aqueous solution were dropped from each separate dropping line at a constant rate over 3 hours and allowed to react in a sealed state. The reaction temperature was maintained at 80-100 ° C. After completion of dropping, the temperature was kept at 95 to 100 ° C. for 3 hours. Then, isopropyl alcohol was removed under reduced pressure while dropping (watering) 150 parts of ion exchange water at this temperature, and then cooled to 30 ° C. Subsequently, 105 parts (1.4 mole parts) of N-methylethanolamine was gradually added in portions while maintaining the temperature at 40 ° C. or lower with stirring. Then, it added with water and adjusted the density | concentration to 25% and obtained the thickener (7) (carboxyl group: 30 mol%) of this invention. The thickener (7) had a weight average molecular weight of 8 × 10 ³ .

<Example 8>
Dispersion medium (1) {ion-exchanged water} 80 parts, alumina (fine particles) 0.6 parts, ceria-zirconia composite oxide (fine particles) 5.4 parts and PGM (platinum group metals: rhodium, palladium, platinum) supported After uniformly mixing 14 parts of the ceria-zirconia composite oxide (fine particles) to obtain a slurry (a1), the slurry (a1) was wet pulverized (below 40 ° C., about 30 minutes) with a bead mill. (B1) was obtained. The slurry (b1) and 0.8 part of the thickener (1) obtained in Example 1 were uniformly mixed to obtain an exhaust gas purifying catalyst slurry (c1) of the present invention.

<Example 9>
Except having changed "0.8 part of thickener (1) obtained in Example 1" into "0.7 part of thickener (1) obtained in Example 1," it carried out similarly to Example 8, and having changed. Thus, an exhaust gas-purifying slurry (c2) of the present invention was obtained.

<Example 10>
Exhaust gas purification slurry of the present invention in the same manner as in Example 8, except that "Thickener (1) obtained in Example 1" was changed to "Thickener (3) obtained in Example 3". (C3) was obtained.

<Example 11>
Except that “0.8 parts by weight of the thickener (1) obtained in Example 1” was changed to “0.4 parts by weight of the thickener (3) obtained in Example 3”, in the same manner as in Example 8. Thus, an exhaust gas-purifying slurry (c4) of the present invention was obtained.

<Example 12>
Exhaust gas purification slurry of the present invention in the same manner as in Example 8, except that "Thickener (1) obtained in Example 1" was changed to "Thickener (5) obtained in Example 5". (C5) was obtained.

<Example 13>
Exhaust gas purification slurry of the present invention in the same manner as in Example 8, except that "Thickener (1) obtained in Example 1" was changed to "Thickener (6) obtained in Example 6". (C6) was obtained.

<Example 14>
Exhaust gas purification slurry of the present invention in the same manner as in Example 8, except that "Thickener (1) obtained in Example 1" was changed to "Thickener (7) obtained in Example 7". (C7) was obtained.

<Example 15>
Exhaust gas purification slurry of the present invention in the same manner as in Example 8, except that "Thickener (1) obtained in Example 1" was changed to "Thickener (2) obtained in Example 2". (C8) was obtained.

<Example 16>
Exhaust gas purification slurry of the present invention in the same manner as in Example 8, except that "Thickener (1) obtained in Example 1" was changed to "Thickener (4) obtained in Example 4". (C9) was obtained.

<Comparative Example 1>
A comparative exhaust gas purifying slurry (c10) was obtained in the same manner as in Example 8, except that the “thickener (1) obtained in Example 1” was not used.

<Comparative example 2>
Disperse medium (1) 50 parts of {ion exchange water}, 0.6 parts of alumina, 5.4 parts of ceria-zirconia composite oxide and 14 parts of ceria-zirconia composite oxide carrying PGM (platinum group metal) After mixing to obtain a slurry (a1), the slurry (a1) was wet pulverized to obtain a slurry (b1). The slurry (b1) was uniformly mixed to obtain a comparative exhaust gas purifying catalyst slurry (c11).

<Example 17>
While reducing the pressure on the outlet end side of the honeycomb type base material (connected between the inlet end side and the outlet end side, see FIG. 1) made of cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ) The inlet end side was attached to the slurry for exhaust gas purification catalyst (c1) obtained in Example 8, and the slurry was applied to the inside of the honeycomb to obtain the coated substrate (1).
The coated substrate (1) was dried at 250 ° C. for 1 hour and then calcined at 500 ° C. for 1 hour to obtain an exhaust gas purification catalyst (1).

<Examples 18 to 23>
Except that the exhaust gas purification catalyst slurry (c1) was changed to any one of the exhaust gas purification catalyst slurries (c2) to (c9), the coated substrates (2) to (9) were obtained in the same manner as in Example 17. After that, exhaust gas purification catalysts (2) to (9) were obtained.

<Comparative Examples 3-4>
Except that the exhaust gas purification catalyst slurry (c1) was changed to any one of the comparative exhaust gas purification catalyst slurries (c10) to (c11), the coated substrates (10) to (11) were the same as in Example 17. ), Exhaust gas purification catalysts (10) to (11) for comparison were obtained.

<Slurry viscosity>
About the slurry (c1)-(c11) for exhaust gas purification catalysts, the viscosity (25 degreeC) was measured by shear rate 4s- ¹ using rheometer Physica MCR301 (made by Anton Paar), and it showed in the following table | surface.

For the exhaust gas purification catalysts (1) to (11), the inlet end side of the cordierite honeycomb-type base material is visually observed, the number of cells (hexagonal holes) blocked is counted, and The clogging rate (%) was calculated.
(Clogging rate) = (Number of blocked cells) × 100 / (Total number of cells)

  When the slurry for exhaust gas catalyst (Examples 8 to 16) using the thickener (Examples 1 to 7) of the present invention is used, the case of using the comparative slurry (Comparative Examples 1 to 2), There was no clogging and the coating could be applied uniformly to the substrate. Therefore, if the slurry for exhaust gas catalyst of the present invention is used, the viscosity can be increased without increasing the solid content concentration of the slurry, it can be uniformly applied to the substrate with less clogging, and high productivity. An exhaust gas purification catalyst can be prepared at a low cost.

Claims (11)

A thickener for increasing the viscosity of a slurry for exhaust gas purification catalyst containing a heat-resistant inorganic oxide supporting a noble metal and a dispersion medium,
It comprises a (co) polymer comprising at least one selected from the group consisting of acrylic acid, ammonium acrylate and amine acrylate as an essential constituent monomer (a),
A thickener, wherein the (co) polymer has a weight average molecular weight of 6 × 10 ³ to 1.4 × 10 ⁴ . As a constituent monomer of the (co) polymer, at least one comonomer (b) selected from the group consisting of methacrylic acid, ammonium methacrylate, amine methacrylate and (meth) acrylic acid alkyl ester is included. The thickener according to claim 1 comprising: Based on the number of moles of the essential constituent monomer (a) unit and the comonomer (b) unit, the content of the essential constituent monomer (a) unit is 93 to 99 mol%, the comonomer (B) Thickener of Claim 2 whose content of a unit is 1-7 mol%. The number of moles of carboxyl groups contained in the (co) polymer is 20 to 70 mol% based on the number of moles of all monomers constituting the (co) polymer. Thickener. A slurry for an exhaust gas purification catalyst comprising the thickener according to any one of claims 1 to 4, a heat-resistant inorganic oxide supporting a noble metal, and a dispersion medium. The slurry according to claim 5, wherein the heat-resistant inorganic oxide is at least one selected from the group consisting of zirconia, alumina, silica, titania and ceria. A slurrying step (1) for obtaining a slurry by uniformly mixing and dispersing the thickening agent according to any one of claims 1 to 4, a heat-resistant inorganic oxide supporting a noble metal, and a dispersion medium; Production of an exhaust gas purification catalyst comprising: an application step (2) for obtaining a coated substrate by coating, and a drying / firing step (3) for drying and firing the coated substrate to obtain an exhaust gas purification catalyst. Method. The manufacturing method according to claim 7, wherein the heat-resistant inorganic oxide is at least one selected from the group consisting of zirconia, alumina, silica, titania and ceria. A monolithic base material in which the base material communicates between the inlet end side and the outlet end side;
The coating step (2) is a transfer coating step (21) in which the slurry is transferred from the inlet end side toward the outlet end side, or a dip coating step (22) in which the substrate is immersed in the slurry. The manufacturing method according to claim 7 or 8. A monolithic base material in which the base material communicates between the inlet end side and the outlet end side;
Coating step (2) is performed by a method in which the outlet end side is set to a negative pressure from the inlet end side and the slurry is transferred from the inlet end side to the outlet end side due to a pressure difference between the inlet end side and the outlet end side. The manufacturing method according to claim 7 or 8, which is a transfer coating step. An internal combustion engine manufacturing method comprising an exhaust gas purifying catalyst manufactured by the manufacturing method according to claim 7.

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