| 502 / | HD | CATALYST, SOLID SORBENT, OR SUPPORT THEREFOR: PRODUCT OR PROCESS OF MAKING |
| 100 | DF | CATALYST OR PRECURSOR THEREFOR {12} |
| 232 | DF | .~ Silicon containing or process of making {2} |
| 240 | DF | .~.~ With metal, metal oxide, or metal hydroxide {8} |
| 250 | DF | .~.~.~ Of Group II (i.e., alkaline earth, Be, Mg, Zn, Cd or Hg) {2} |
| 251 | | .~.~.~.~ Magnesium {1} |
| 252 | DF | .~.~.~.~.~> And Group VIII metal containing (i.e., iron or platinum group) |