With increasingly stringent environmental requirements and regulations in worldwide, upgrading the quality of gasoline is an impending problem. In particular, China recently announced the new standard for gasoline which is stricter on olefin content and T50 of the gasoline. The gasoline pool of China mainly consists of fluid catalytic cracking (FCC) gasoline which possesses higher content of olefin with C5=-C7= components as major part. In addition, C10-C12 n-alkane components in FCC gasoline with high boiling point and low octane number are unfavorable because of its negative effect on T50. Given the C-C bonding energy of the C10-C12 n-alkanes and the C5=-C7= olefins are similar, we propose a new concept for upgrading the quality of gasoline through head-tail coconversion process. Specifically, we chose 1-hexene and n-decane as head-tail model compounds of these olefin and n-alkane components in FCC gasoline, and typical catalytic results show that higher yield of gasoline (59.6 wt% vs. 50.8 wt%) with lower T50 (99.2oC vs. 104.8oC) and higher i-paraffin content (33.9 wt% vs. 30.3 wt%) could be obtained with co-feeding at 325oC in comparison with single-feeding (Figure 1A). In addition, the olefin content in gasoline product under co-feeding method (21.7 wt%) was lower than that in feed (37.2 wt%). Based on chemical kinetic analysis (Figure 1B), higher 1-hexene isomers and i-paraffins formation rate under co-feeding condition indicates that the hydrogen transfer path between n-decane and carbocations converted from 1-hexene could promote the formation of i-paraffin in gasoline. Such head-tail coconversion of long chain n-alkanes and C5=-C7= could not only regulate the distribution of gasoline product which contributes to upgrading the quality of FCC gasoline, but also help to shed new light on exploring the reaction rule in molecular level.

Efficient head-tail coconversion process for high quality gasoline production via catalytic cracking route

2019 Fall National Meeting

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