| 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} |
| 305 | DF | .~.~ Of Group VI (i.e., Cr, Mo, W or Po) {8} |
| 319 | | .~.~.~ Of chromium {1} |
| 320 | DF | .~.~.~.~> And Group III metal containing (i.e., Sc, Y, Al, Ga, In or Tl) |