Investigation of the Selective Production of Ethylene from Propylene Over Small-Pore Zeolites.

The selective production of ethylene from the direct conversion of propylene (propylene-to-ethylene, PTE) was examined for the first time using various types of 8-membered ring (8-MR) zeolite materials with different pore structures. Among these 8-MR zeolites, SSZ-13 zeolite with a three-dimensional chabazite structure exhibited the highest ethylene yield. To increase the ethylene selectivity further, the PTE reactions were conducted over SSZ-13 zeolite external surface modifications with silylation or phosphorus. The external surface modifications enhanced the ethylene selectivity due to the passivation of external acid sites. The surface-modified SSZ-13 catalyst exhibited the highest selectivity to ethylene, at more than 90% at 450 degrees C, a WHSV of 0.33 h(-1), and a propylene particle pressure of 0.1 MPa.