Abstract: Due to the growing demands of light olefins, FCC is an important process for propylene production. However, methanol was found in cracking gas which affects the downstream polymerization. The source of oxygen during methanol formation, methanol formation discipline and influence factors were studied. The results indicated that the oxygen contained in methanol is from water, gas mixture of SOx and NOx. With the presence of SO2 and NOx, methanol is formed by reaction of SOx, NOx and H2O. Thermal cracking reaction occurs when catalyst activity is lower, leading to the generation of methanol which follows the free radical mechanism. To inhibit the methanol generation, measures be adopted in commercial operation: (i) reducing the content of SOx and NOx in the flue gas entrained by regenerated catalyst; (ii) maintaining catalyst activity high enough.

Key words: catalytic cracking, oxygenate, methanol, propylene