This invention relates to an aqueous dispersion of particles, the dispersion having a particle content of 10-70 wt %, and the particles comprising, on an oxide basis: (a) 10-98 wt % in total of ZrO.sub.2+HfO.sub.2, and (b) 2-90 wt % in total of AI.sub.2O.sub.3, CeO.sub.2, La.sub.2O.sub.3, Nd.sub.2O.sub.3, Pr.sub.6O.sub.11, Y.sub.2O.sub.3, or a transition metal oxide, wherein the dispersion has a Z-average particle size of 100-350 nm and the particles have a crystallite size of 1-9 nm. The invention also relates to a substrate coated with the aqueous dispersion of particles.

The present teachings are directed to inorganic oxide materials that include Al.sub.2O.sub.3, CeO.sub.2, and at least one of MgO and Pr.sub.6O.sub.11. The present teachings are also directed to catalysts having at least one noble metal supported on these inorganic oxide materials, as well as methods for treating exhaust gases from internal combustion engines using such catalysts.

The present teachings are directed to inorganic oxide materials that include Al.sub.2O.sub.3, CeO.sub.2, and at least one of MgO and Pr.sub.6O.sub.11. The present teachings are also directed to catalysts having at least one noble metal supported on these inorganic oxide materials, as well as methods for treating exhaust gases from internal combustion engines using such catalysts.

A method of forming a metal oxide material having a rod shape or polyhedral nanostructure includes preparing a first reverse micro-emulsion system comprising an aqueous precipitating agent dispersion and a second reverse micro-emulsion system containing an aqueous metal salt dispersion; combining the micro-emulsions together to initiate a reaction; allowing the reaction to continue to form a product mixture comprising a metal oxide gel and aqueous media; separating the metal oxide gel from the aqueous media; collecting the metal oxide gel; and calcining the metal oxide gel to form the metal oxide material. The metal oxide material corresponds to the chemical formula of La.sub.2M.sub.xNi.sub.1-xO.sub.4, Pr.sub.2-yA.sub.yNiO.sub.4, or La.sub.2-zD.sub.zNiO.sub.4, wherein M is copper, cobalt, iron, manganese, chromium, aluminum, or platinum; A is lanthanum or neodymium; D is calcium, barium or strontium; x ranges from 0 to 1; y ranges from 0 to 2; and z ranges from 0 to 0.25.

A nitrous oxide (N.sub.2O) removal catalyst composite is provided, comprising a N.sub.2O removal catalytic material on a substrate, the catalytic material comprising a rhodium (Rh) component supported on a ceria-based support, wherein the catalyst composite has a H.sub.2-consumption peak of about 100° C. or less as measured by hydrogen temperature-programmed reduction (H.sub.2-TPR). Methods of making and using the same are also provided.

A nitrous oxide (N.sub.2O) removal catalyst composite is provided, comprising a N.sub.2O removal catalytic material on a substrate, the catalytic material comprising a rhodium (Rh) component supported on a ceria-based support, wherein the catalyst composite has a H.sub.2-consumption peak of about 100° C. or less as measured by hydrogen temperature-programmed reduction (H.sub.2-TPR). Methods of making and using the same are also provided.

The invention relates to a method for converting a gas into methane (CH4) which includes: a step of activating a catalytic material including praseodymium oxide (Pr6O11) associated with nickel oxide (NiO) and alumina (Al2O3), the respective proportions of which are, relative to the total mass of these three compounds: Pr6O11: 1 wt % to 20 wt %, NiO: 1 wt % to 20 wt %, and A12O3: 60 to 98 wt %; and a step of passing a gas including at least one carbon monoxide (CO) over the activated catalytic material.

The invention relates to a method for converting a gas into methane (CH4) which includes: a step of activating a catalytic material including praseodymium oxide (Pr6O11) associated with nickel oxide (NiO) and alumina (Al2O3), the respective proportions of which are, relative to the total mass of these three compounds: Pr6O11: 1 wt % to 20 wt %, NiO: 1 wt % to 20 wt %, and A12O3: 60 to 98 wt %; and a step of passing a gas including at least one carbon monoxide (CO) over the activated catalytic material.

A nanocrystal-sized cerium-zirconium mixed oxide material includes at least 30% by mass zirconium oxide; between 5% to 55% by mass cerium oxide; and a total of 25% or less by mass of at least one oxide of a rare earth metal selected from the group of lanthanum, neodymium, praseodymium, or yttrium. The nanocrystal-sized cerium-zirconium mixed oxide exhibits hierarchically ordered aggregates having a d.sub.50 particle size less than 1.5 μm and a total pore volume after calcination at a temperature of 600° C. or more that is at least 0.7 cm.sup.3/g with a fraction of pores between 2 nm to 10 nm being less than 15%. The nanocrystal-sized cerium-zirconium mixed oxide material is prepared using a co-precipitation method followed by milling the dried and calcined oxide material. The nanocrystal-sized cerium-zirconium mixed oxide material forms a particulate filter that may be used in an exhaust system arising from a gas or diesel engine.

A nanocrystal-sized cerium-zirconium mixed oxide material includes at least 30% by mass zirconium oxide; between 5% to 55% by mass cerium oxide; and a total of 25% or less by mass of at least one oxide of a rare earth metal selected from the group of lanthanum, neodymium, praseodymium, or yttrium. The nanocrystal-sized cerium-zirconium mixed oxide exhibits hierarchically ordered aggregates having a d.sub.50 particle size less than 1.5 μm and a total pore volume after calcination at a temperature of 600° C. or more that is at least 0.7 cm.sup.3/g with a fraction of pores between 2 nm to 10 nm being less than 15%. The nanocrystal-sized cerium-zirconium mixed oxide material is prepared using a co-precipitation method followed by milling the dried and calcined oxide material. The nanocrystal-sized cerium-zirconium mixed oxide material forms a particulate filter that may be used in an exhaust system arising from a gas or diesel engine.