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

Industrial demand for propylene is increasing. Alternative sources of propylene other than petroleum are of wide interest. The catalytic transformation of bioethanol is a promising avenue for the production of propylene. In this work, we investigated the catalytic activities and the reaction mechanism for ethanol conversion to propylene over ZSM-5 catalysts.

We found that the ethylene production by the dehydration of ethanol is observed over BEA, MOR, Y, and FER. On ZSM-5, propylene and butenes were produced, indicating that the oligomerization of ethylene proceeded over ZSM-5. Futhermore, a moderate density of Bronsted acid sites on ZSM-5 was necessary for effective production of propylene. According to the result of the product distribution of the initial reaction stage at a very short contact time, we propose the following mechanism for the ethanol conversion reaction. i) Ethanol was converted to ethylene by rapid dehydration. ii) Ethylene directly transformed to propylene via a π-complex on ZSM-5. Ethylene was also converted to butene by dimerization. iii) Propylene or butene subsequently reacted with ethylene to form C5 or C6 olefins, respectively.

The catalyst deactivation of ZSM-5 is come from the dealumination because of the existence of water which was produced by dehydration of ethanol. The catalytic durability of ZSM-5 was drastically improved by phosphorus modification. The dealumination with water was significantly suppressed by the addition of phosphorus.