| 502 / | HD | CATALYST, SOLID SORBENT, OR SUPPORT THEREFOR: PRODUCT OR PROCESS OF MAKING |
| 100 | DF | CATALYST OR PRECURSOR THEREFOR {12} |
| 300 | DF | .~ Metal, metal oxide or metal hydroxide {10} |
| 302 | DF | .~.~ Of lanthanide series (i.e., atomic number 57 to 71 inclusive) {2} |
| 304 | | .~.~.~ Cerium |