Catalytic cracking gasoline upgrading method

A catalytic cracking gasoline upgrading method, comprising:

• first, in the presence of a prehydrogenation catalyst, removing diolefins, mercaptans and sulfides from full-range FCC gasoline through a prehydrogenation reactor and converting double bond isomeric terminal olefins into internal olefins at the same time;
• and then carrying out selective hydrodesulfurization on the prehydrogenation product in the presence of a hydrodesulfurization-isomerization catalyst, and isomerizing straight-chain olefins into single-branched olefins or single-branched alkanes, thus obtaining ultralow-sulfur clean gasoline;
• wherein the hydrodesulfurization-isomerization catalyst comprises a carrier and an active ingredient, the carrier contains an alumina composite carrier with a macroporous structure, the alumina composite carrier contains 0.1-12 wt % of tungsten-doped lanthanum ferrite, tungsten in the tungsten-doped lanthanum ferrite accounts for 0.1-8 wt %, the mesopores of the alumina composite carrier account for 1-85% of the total pores, and the macropores of the alumina composite carrier account for 1-70% of the total pores;
• the surface of the carrier is loaded with phosphomolybdic acid, phosphotungstic acid or phosphomolybdotungstic acid;
• by weight, the content of phosphomolybdic acid, phosphotungstic acid or phosphomolybdotungstic acid in the catalyst is between 0.1% and 16.5% as oxides.