| 摘要 |
A sulfur-containing catalytically cracked naphtha is upgraded to form a low-sulfur gasoline product by a process which retains the octane contribution from the olefinic front end of the naphtha. Initially, the mercaptan sulfur in the front end of the cracked naphtha is converted to higher boiling disulfides by oxidation. The front end, which is then essentially an olefinic, high octane sulfur-free material, may be blended directly into the gasoline pool. The back end, which now contains the original higher boiling sulfur components such as thiophenes, together with the sulfur transferred from the front end as disulfides, is hydrotreated to produce a desulfurized product. This desulfurized product, which has undergone a loss in octane by saturation of olefins, is then treated in a second stage, by contact with a catalyst of acidic functionality, preferably a zeolite such as ZSM-5, under conditions which produce a product in the gasoline boiling range of higher octane value. Because this second product may contain combined organic sulfur, it may be subjected to a final desulfurization to reduce organic sulfur to acceptable levels. |
