Composition useful to treat exhaust gases of internal combustion engines, comprising zirconium oxide, cerium oxide, lanthanum oxide and other rare earth oxides, exhibits defined specific surface of lanthanum oxide

摘要

#CMT# #/CMT# Composition (A) comprising zirconium oxide, cerium oxide, lanthanum oxide and oxide of another rare earth e.g. yttrium, samarium and gadolinium, presents a specific surface of >=40 m 2>/g after calcination for 4 hours at 1000[deg]C, a specific surface of >=15 m 2>/g after calcination for 10 hours at 1150[deg]C, a specific surface of >=7 m 2>/g after calcination for 10 hours at 1200[deg]C and a content of lanthanum oxide and oxide of other rare earth metals at >=15%. #CMT# : #/CMT# Independent claims are included for: (1) preparation of (A) comprising preparing a mixture in a liquid medium containing zirconium, cerium, lanthanum and other rare earth compounds, contacting the mixture with basic compound to obtain a precipitate, heating the precipitate in a liquid medium, adding additives such as to the obtained precipitate anionic surfactants, non-ionic surfactants, polyethyleneglycols, carboxylic acids and their salts or ethoxylate type surfactant of fatty carboxymethyl alcohols, washing the obtained precipitate and calcining the obtained precipitate; (2) a catalytic system, comprising (A); and (3) treatment of exhaust gases from internal combustion engines, using the catalytic system. #CMT#USE : #/CMT# (A) is useful in the treatment of the exhaust gases of internal combustion engines (claimed). #CMT#ADVANTAGE : #/CMT# (A) exhibits improved and stable specific surface and can be easily prepared. #CMT#INORGANIC CHEMISTRY : #/CMT# Preferred Properties: (A) exhibits a specific surface of >=50 m 2>/g after calcination for 4 hours at 1000[deg]C and a specific surface of >=10 m 2>/g after calcination for 10 hours at 1200[deg]C. Preferred Components: The content of lanthanum oxide and other rare earth oxide in (A) is 15-35% and the mass ratio of lanthanum oxide to the rare earth oxide is less than 1.5, preferably less than 1. The content of cerium in (A) is 10-60%, preferably 20-50%. Preferred Process: The heating of the precipitate is carried out at >=100[deg]C. #CMT#EXAMPLE : #/CMT# Zirconium nitrate (152 ml), cerium nitrate (163.9 ml), lanthanum nitrate (13.2 ml) and yttrium nitrate (36.6 ml), were introduced into a beaker under agitation. The reaction mixture was made up to 1 liter using distilled water. Ammonia solution (253.4 ml) was introduced into a reactor under agitation and the solution was made up to 1 liter using distilled water. The nitrate solution was introduced into the reactor under constant agitation. The resulting solution was placed in a stainless steel autoclave equipped with a mobile agitation. The temperature was raised to 150[deg]C for 2 hours under agitation. Lauric acid (33 g) was added to the obtained suspension. The suspension was kept under stirring for 1 hour. The suspension was then filtered on Buchner, and then the filtered precipitate was washed with ammonia cal water. The obtained product was then calcined at 700[deg]C for 4 hours to obtain a composition containing zirconia (40 wt.%), cerium oxide (40 wt.%), lanthanum oxide (6 wt.%) and yttrium oxide (14%).