日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Production of propylene by fluid catalytic cracking (FCC) has become more attractive due to a recent growing demand for propylene. In order to increase propylene yield in FCC process, it is important to enhance the cracking activity of the catalyst and minimize the activity for hydrogen transfer reactions. Most of FCC catalysts contain Y type zeolites, and the product yields can be controlled by optimizing the solid acidities and the pore structures of the catalysts. Although reducing the solid acid density and suppress the hydrogen transfer reaction are the main concepts for designing a FCC catalyst producing more propylene, an addition of ZSM-5 additive is much more effective than a modification of FCC catalyst itself. The ZSM-5 additive cracks gasoline-range olefins, which are produced by the FCC catalyst, to light olefins such as propylene and butanes. The catalytic performance of ZSM-5 additive depends largely on the character of ZSM-5 zeolite, the pore structure of the additive, and the phosphorous modification technologies applied for increasing the hydrothermal stability of the catalyst.