| Answer | Crossword Clue |
|---|---|
| pre | Petroleum Refining Engineer |
| PROPENE | Gas from petroleum refining. |
| ETHANE | Byproduct of petroleum refining |
| ETHANE | Byproduct in petroleum refining |
| petrochemical | Relating to or denoting substances obtained by the refining and processing of petroleum or natural gas |
| petrochemistry | The branch of chemistry concerned with petroleum and natural gas, and with their refining and processing |
