Absorbent for a hydrocarbon, and exhaust gas-purifying catalyst

A method for purifying an exhaust gas, which comprises contacting an exhaust gas-purifying catalyst comprising (1) an adsorbent for a hydrocarbon which comprises a calcined beta zeolite showing a powder X-ray diffraction such that the sum of X-ray diffraction intensities at lattice spacings d=1.15±0.03 nm and d=0.397±0.01 nm, is at least 90% of the diffraction intensity at d=0.346±0.01 nm of Catalysis Society reference catalyst JRC-Z-HM-20(3), and (2) a nitrogen oxide removing catalyst having an active metal contained in a porous material, with the exhaust gas.

A method for adsorbing and removing a hydrocarbon from a gas phase, comprising:

• contacting an adsorbent for a hydrocarbon which is a straight chain paraffin or olefin, each having at least 7 carbon atoms, and/or a polycyclic aromatic compound, which adsorbent comprises a calcined β-zeolite showing a powder X-ray diffraction pattern such that the sum of X-ray diffraction intensities at lattice spacings d=1.15±0.03 nm and d=0.397±0.01 nm, is at least 90% of the diffraction intensity at d=0.346±0.01 nm of Catalysis Society reference catalyst JRC-Z-HM-20(3), with the gas phase.

A method for purifying an exhaust gas, which comprises:

• contacting an exhaust gas-purifying catalyst comprising (1) an adsorbent that is a calcined β-zeolite showing a powder X-ray diffraction pattern such that the sum of X-ray diffraction intensities at lattice spacings d=1.15±0.03 nm and d=0.397±0.01 nm, is at least 90% of the diffraction intensity at d=0.346±0.01 nm of Catalysis Society reference catalyst JRC-Z-HM-20(3) for a hydrocarbon which is a straight chain paraffin or olefin, each having at least 7 carbon atoms, and/or a polycyclic aromatic compound, and (2) a nitrogen oxide removing catalyst having an active metal contained in a porous material, with the exhaust gas.