Abstract: The effect of catalyst to oil (C/O) ratio and weight hourly space velocity (WHSV) on the yield and compositions of LPG was investigated using a laboratory fixed-fluidized bed (FFB) unit, VGO feedstock, a catalyst containing zeolite Y and shape-selective zeolite. Test results show that with the decrease of WHSV and the increase of C/O ratio, both the LPG yield and heavy oil conversion enhance, but their effects on the compositions of LPG are distinct. With the decrease of WHSV the propylene content of LPG increases; contrarily, with the increase of C/O ratio, the propylene content of LPG decreases, the reason of which is discussed as well. It is found that the decrease of WHSV favors chemical reactions happened in the shape-selective zeolite, and with the increase of C/O ratio, reactions took place in zeolite Y are benefited.

Key words: catalytic cracking, catalyst to oil ratio, WHSV, LPG, propylene