An exhaust gas-purifying catalyst includes a support and a catalytic metal as one or more precious metals supported by the support. The support includes a composite oxide having a composition represented by a general formula AB.sub.C.sub.O.sub.3, wherein A represents one or more elements selected from the group consisting of lanthanum, neodymium, and yttrium, B represents iron or a combination of iron and aluminum, C represents one or more elements selected from the group consisting of iridium, ruthenium, tantalum, niobium, molybdenum, and tungsten, and each represents a numerical value within a range of more than 0 and less than 1, and and satisfy relational formulae of > and +1.

Provided are a catalyst whereby isobutylene can be produced at high yield in a lower-temperature environment, and a method for producing isobutylene using the catalyst. The catalyst for producing isobutylene is an oxide including at least one element selected from molybdenum and tungsten, and at least one element selected from tantalum, niobium, and titanium.

Provided are a catalyst whereby isobutylene can be produced at high yield in a lower-temperature environment, and a method for producing isobutylene using the catalyst. The catalyst for producing isobutylene is an oxide including at least one element selected from molybdenum and tungsten, and at least one element selected from tantalum, niobium, and titanium.

An exhaust gas-purifying catalyst includes a support and a catalytic metal as one or more precious metals supported by the support. The support includes a composite oxide having a composition represented by a general formula AB.sub.C.sub.O.sub.3, wherein A represents one or more elements selected from the group consisting of lanthanum, neodymium, and yttrium, B represents iron or a combination of iron and aluminum, C represents one or more elements selected from the group consisting of iridium, ruthenium, tantalum, niobium, molybdenum, and tungsten, and each represents a numerical value within a range of more than 0 and less than 1, and and satisfy relational formulae of > and +1.

An exhaust gas-purifying catalyst includes a support and a catalytic metal as one or more precious metals supported by the support. The support includes a composite oxide having a composition represented by a general formula AB.sub.C.sub.O.sub.3, wherein A represents one or more elements selected from the group consisting of lanthanum, neodymium, and yttrium, B represents iron or a combination of iron and aluminum, C represents one or more elements selected from the group consisting of iridium, ruthenium, tantalum, niobium, molybdenum, and tungsten, and each represents a numerical value within a range of more than 0 and less than 1, and and satisfy relational formulae of > and +1.

Provided are a catalyst whereby isobutylene can be produced at high yield in a lower-temperature environment, and a method for producing isobutylene using the catalyst. The catalyst for producing isobutylene is an oxide including at least one element selected from molybdenum and tungsten, and at least one element selected from tantalum, niobium, and titanium.

Provided are a catalyst whereby isobutylene can be produced at high yield in a lower-temperature environment, and a method for producing isobutylene using the catalyst. The catalyst for producing isobutylene is an oxide including at least one element selected from molybdenum and tungsten, and at least one element selected from tantalum, niobium, and titanium.

Disclosed is a calcination apparatus, including: a calcination tube having open ends at both terminals; a pair of hoods, each hood covering each open end of the calcination tube; and a pair of rings, each ring sealing a gap between the calcination tube and the hood, wherein the rings are directly or indirectly fixed on an outer surface of the calcination tube; a groove is provided along a circumferential direction of the ring at a contact surface side between the ring and the hood; a sealed chamber surrounded by the hood and the groove is formed; and both the calcination tube and the rings rotate in a circumferential direction of the calcination tube while keeping the hood in contact with both sides of the groove.

Disclosed is a calcination apparatus, including: a calcination tube having open ends at both terminals; a pair of hoods, each hood covering each open end of the calcination tube; and a pair of rings, each ring sealing a gap between the calcination tube and the hood, wherein the rings are directly or indirectly fixed on an outer surface of the calcination tube; a groove is provided along a circumferential direction of the ring at a contact surface side between the ring and the hood; a sealed chamber surrounded by the hood and the groove is formed; and both the calcination tube and the rings rotate in a circumferential direction of the calcination tube while keeping the hood in contact with both sides of the groove.

An exhaust gas-purifying catalyst includes a support and a catalytic metal supported thereby. The support includes a composite oxide represented by AO.xB.sub.2-C.sub.O.sub.3, wherein A represents at least one of an element having a valence of 1 and an element having a valence of 2, B represents an element having a valence of 3, C represents one or more elements selected from iridium, ruthenium, tantalum, niobium, molybdenum, and tungsten, x represents a numerical value of 1 to 6, and a represents a numerical value greater than 0 and less than 2. The catalytic metal includes one or more precious metals selected from rhodium, palladium, and platinum.