| 摘要 |
PROBLEM TO BE SOLVED: To obtain a catalyst for purifying exhaust gas which can maintain a high NOx purification ratio in an oxygen excess atmosphere by making the catalyst passes a carrier consisting of a kind of gallosilicate supporting Pt an CeO2 having a specified average crystallite diameter, and setting the SiO2 /Ga2 O3 mole ratio of the gallosilicate within a specified range. SOLUTION: As a catalyst which is deteriorated when exposed to a hydrothermic environment and in which the NOx purification capacity in an oxygen excess atmosphere is not lowered, by providing a carrier which supported Pt and CeO2 whose average crystallite diameter D is D>=13.0 nm, the catalyst is formed. The carrier to be used is formed out of a kind of gallosilicate. The gallosilicate (Ga2 O3 .SiO2 .nH2 O) is a substance in which Al which is a skeleton atom of zeolite is replaced with Ga and means a substance in which the quantity of residual Al is on an inevitable impurity level. By subjecting the gallosilicate to de-Ga treatment, a modified gallosilicate in which the SiO2 /Ga2 O3 mole ratio M is 100<=M<=1230 is obtained. |
