Fluidized catalytic conversion method for preparing low-carbon olefins

A fluidized catalytic conversion method for producing light olefins, comprising the steps of:

• 1) Introducing an olefin-rich feedstock through a first inlet into a fluidized catalytic conversion reactor, contacting with a catalytic conversion catalyst, and reacting under first catalytic conversion conditions, wherein the olefin-rich feedstock has an olefin content of 50 wt % or more and the catalyst conversion catalyst is preheated to a temperature of 650° C. or higher;
• 2) Separating the effluent of the fluidized catalytic conversion reactor to obtain a reaction product vapor and a spent catalyst, and separating the reaction product vapor to obtain ethylene, propylene, butylene and a stream comprising C5+ olefins;
• and
• 3) feeding at least a part of the stream comprising C5+ olefins obtained from step 2) to the fluidized catalytic conversion reactor through a second inlet located downstream from the first inlet for further reaction,
• wherein the first catalytic conversion conditions include:
• a reaction temperature of 600-800° C.;
• a reaction pressure of 0.05-1 MPa;
• a reaction time of 0.01 to 100 seconds;
• and
• a weight ratio of the catalytic conversion catalyst to the olefin-rich feedstock of (1-200):1;
• and
• 4) feeding at least a part of the butylene obtained from step 2) to the fluidized catalytic conversion reactor at a third inlet located downstream from the first inlet for further reaction under second catalytic conversion conditions,
• wherein the second catalytic conversion conversions include:
• a reaction temperature of 650-800° C.;
• a reaction pressure of 0.05-1 MPa;
• a reaction time of 0.01 to 10 seconds;
• and
• a weight ratio of the catalytic conversion catalyst to the butylene of (20-200):1.