| 502 / | HD | CATALYST, SOLID SORBENT, OR SUPPORT THEREFOR: PRODUCT OR PROCESS OF MAKING | 
| 20 | DF | REGENERATING OR REHABILITATING CATALYST OR SORBENT {4} | 
| 22 | DF | .~ Treating with a liquid or treating in a liquid phase, including dissolved or suspended {5} | 
| 27 | DF | .~.~ Using acid {1} | 
| 28 |  | .~.~.~ Organic |