Abstract: Deep reduction of the olefins content in gasoline is the key to upgrading gasoline quality in China. Based on the in-depth study of the synergy and competition between bimolecular cracking reaction and hydrogen transfer reaction, the effects of these two kinds of reactions on the decrease of gasoline olefins content and the increase of coke production were divided into three regions, named “coke yield controllable region”, “coke yield transition region” and “coke uncontrollable region”, respectively. Based on this, the development ideal of FCC process for controlling olefins content in gasoline by zones was put forward. Furthermore, the variable-diameter fluidized bed catalytic cracking process suitable for “coke yield controllable zone”, the optimum reaction mode of catalytic cracking process suitable for “coke yield transition zone”, and the catalytic cracking technology suitable for ultra-low olefin gasoline in coke-controlled zone have been developed. Especially in the region where the coke content could not be controlled, the creative introduction of hydrogen negative ion releasing agent and the optimization of the introduction mode have fundamentally solved the key contradiction between deep reduction of olefins content in gasoline and rapid increase of coke yield. The increase rate of coke yield was controlled while the olefin content in gasoline was greatly reduced, which provided a reliable guarantee for upgrading gasoline quality.

Key words: vehicle gasoline, catalytic cracking, olefins content regulation, hydrogen transfer, iso-alkane