Abstract: The effects of reaction severity and catalyst type on catalytic cracking of hydrogenated straight-run diesel were investigated in a small fixed fluidized bed unit. Two processing schemes were designed to produce more liquefied petroleum gas (LPG) and gasoline from catalytic cracking of hydrogenated straight-run diesel. The experimental results showed that conversion rates exceeded 75% on the different catalysts rich in Y-type zeolite and ZSM-5 zeolite under different reaction conditions, such as reaction temperature of 520-600 ℃ and catalyst/oil mass ratio of 6.0-10.0. With the increase of conversion rate, the yield of LPG increased, the yield of gasoline decreased and the research octane number (RON) increased. To produce more LPG, it’s suitable for using ZSM-5 zeolite catalyst at the temperature of 600 ℃ and catalyst/oil mass ratio of 9.96, the yields of LPG and propylene were 36.48% and 16.33%, respectively. Besides, the total yield of ethylene, propylene and butylene was 34.49%. To produce more gasoline, it’s suitable for using Y-type zeolite catalyst at the temperature of 520 ℃ and catalyst/oil mass ratio of 6.05, the yield of gasoline was 60.22% and the RON was 94.1. Under the crude oil price system of 80 $/bbl(1bbl=159L), the per ton oil profits of the two processing schemes were 329.5 Yuan and 296.9 Yuan, respectively.

Key words: straight-run diesel, catalytic cracking, catalyst, conversion rate, propylene, liquefied petroleum gas, gasoline