(584u) The Relationship between Olefin Hydrogenation and Octane Number Loss in FCC Gasoline Hydrodesulfurization

Whatever how the developing of clean-gasoline production technology, nowadays hydrodesulfurization (HDS) still possesses the main position as the most effective approach for large scale production of clean gasoline in industry. HDS technology has a lot of advantages in efficient desulfurization and convenience operation, however, it still has a bottleneck problem^[1]. During desulfurization, some of olefin are inevitable hydrogenation, which leading to huge loss of octane number^[2]. Does each kind of olefin saturated has the same effect on octane number of gasoline? What is the relationship between type, carbon number, and structure of olefin and octane number of gasoline? For these questions, people are still not well understand. Furthermore, content of olefins in gasoline will be further cut down in the very near future. Which kinds of olefin should be remove from gasoline? More deeply studies need to be done before handling these olefins in gasoline.

In this study, based on the detailed olefin compositions and distributions in three different kinds of FCC gasoline feedstock obtained by gas chromatography^[3], we studied the relationship between carbon numbers, structures, and content of olefins and loss of octane number of caused by olefins hydrogenation by combined calculation and experimental methods.

During the study, the olefins studied were quantitatively hydrogenated by artificial calculation method to obtain the effect of different carbon numbers olefins on the octane number of gasoline. As the results shown, the saturation of C5-C8 olefins has the greatest impact on the octane number of gasoline. In addition, olefins content was also one of the major factors affecting octane number of gasoline. Therefore, C5-C7 olefins were one of the major contribution components in gasoline, which considers the influence of olefins content in gasoline. It means that the protection of C5-C7 olefins was key to reduce the octane number loss in HDS. Beyond that, the relationship between olefins structures and octane number of gasoline was also studied. And it shown that the RON loss caused by the n-olefins hydrogenation was larger than i-olefins hydrogenation. Thus, in order to keep the octane number of the gasoline, the protection of C5-C7 olefins was more critical.

Acknowledgement

This research is supported by National Natural Science Foundation of China (Grants 21336011, 21476260, 21236009, and U1162204). And also supported by the Science Foundation of China University of Petroleum-Beijing (Grants 2462015YQ0316).

References

[1] Brunet, S., Mey, D., Perot, G., et al. On the hydrodesulfurization of FCC gasoline: a review[J]. Applied Catalysis A: General, 2005. 278(2): 143-172.

[2]Ishutenko D. I., Nikul’shin P. A., Konovalow V. V., et al. Selective hydrotreating of cat cracked gasoline over a K–CoMoS/Al₂O₃ catalyst[J]. Kinetics and Catalysis, 2015. 56(6): 747–757.