| abstract |
This disclosure relates to molecular sieves, in particular to metal-promoted molecular sieves, more particularly to a process for the formation of iron (III) exchanged zeolites. Preferably, the zeolite has a carbazate form or a similar structure. The method may comprise combining the zeolite with the iron (III) cation in an aqueous medium. The process may be performed at a pH of less than about 7 and buffer materials may be used with the aqueous medium. The method beneficially causes iron exchange, which can reach 100%, with removal of the cations (e.g. sodium, NH 4 , and H) from the zeolite. The iron (III) -substituted zeolite prepared according to the disclosed process may contain up to about 2,000 ppm of cations and at least about 1% by weight of iron (III). The present disclosure also provides catalysts (e.g., SCR catalysts) comprising an iron (III) -substituted zeolite and an exhaust treatment system. |