| 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} |
| 254 | DF | .~.~.~ Of Group VI (i.e., Cr, Mo, W or Po) {2} |
| 256 | | .~.~.~.~ Chromium {1} |
| 257 | DF | .~.~.~.~.~> And Group VIII metal containing (i.e., iron or platinum group) |