| 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} |
| 325 | DF | .~.~ Of Group VIII (i.e., iron or platinum group) {7} |
| 337 | | .~.~.~ Of nickel |