| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an iron silicate catalyst being capable of converting nitrogen oxides efficiently over a wide temperature range from low to high temperatures and having high hydrothermal durability, and to provide a method of converting nitrogen oxides using the catalyst. <P>SOLUTION: The catalyst consists of a crystalline silicate of an SiO<SB>2</SB>/Fe<SB>2</SB>O<SB>3</SB>ratio of 20-300 and contains iron in the β-structure with at least 80% of the iron being in the form of isolated ferric ions, and the silicate has high performance of reducing nitrogen oxides selectively at low temperatures. The iron in the β-structure ferric silicate is preferably an isolated ferric ion which has a symmetric tetrahedral structure confirmable by UV/visible absorption spectrometry and electron spin resonance measurement; more preferably, at least 20% of the iron contained are isolated ferric ions having the symmetric tetrahedral structure. <P>COPYRIGHT: (C)2009,JPO&INPIT |
