Effect of ZSM-5 addition on product distribution in a high severity FCC mode

The high-severity fluid catalytic cracking (HS-FCC) process is a novel FCC process that enhances light olefins yield under high severity reaction conditions. The process has been investigated by using a small-scale FCC pilot plant (0.1 BPD) with a down-flow reactor. High severity reaction conditions are preferable for enhancing the production of light olefins by catalytic cracking of heavy oils. As another option for the light olefin production, adoption of ZSM-5 additive in conventional FCC units is well known. This presentation describes the effect of ZSM-5 additive on the catalytic cracking of vacuum gas oil under high severity reaction conditions, particularly focusing on the synergistic effect with the base catalyst. Three kinds of FCC catalysts with different activity were used as base catalysts. Although the employment of a ZSM-5 additive resulted in significant increase in the light olefins yield at the expense of gasoline in each catalyst system tested, the effectiveness was varied depending on the nature of the base catalysts. By choosing a suitable base cracking catalyst, more than 20 wt% of propylene yield was obtained at a one-pass conversion of fresh feed.