Selective production of ethylene and propylene via monomolecular cracking of pentene over proton-exchanged zeolites: Pentene cracking mechanism determined by spatial volume of zeolite cavity

The influence of the pore structures of zeolites on their selectivities for the formation of ethylene and propylene was examined in the conversion of 2-methyl-2-butene and 2-pentene over a wide range of pentene conversion. The selectivities for ethylene and propylene were highly dependent on both the spatial volume of the zeolite cavity and the dimensionality of the pore structure. Only when the specific spatial volume of zeolite, with one- or two-dimensional pore structure, was almost the same as the volume of pentyl cations did the selective production of both ethylene and propylene proceed via the monomolecular cracking of pentene. When the spatial volume of the zeolite cavity was enough larger than the volume of pentyl carbenium ions, the reaction of pentyl carbenium ions with pentene could proceed to produce decyl carbenium ions, and by following their β-scission, butenes and hexenes were preferentially formed, together with ethylene and propylene.

Only when the specific spatial volume of zeolite with one- or two-dimensional pore structure was almost the same as the volume of pentyl cations did the selective production of both ethylene and propylene proceed via the monomolecular cracking of pentene.Figure optionsDownload high-quality image (123 K)Download as PowerPoint slideHighlights
► C2H4 and C3H6 production in pentene conversion was performed using various zeolites.
► The selectivity for C2H4 and C3H6 depend on the spatial volume of zeolite cavity.
► The high selectivity was achieved when the cavity and C5H10+ were the same volume.
► The selective production proceeded via the monomolecular cracking of pentene.
► Spatial volume of zeolite cavity determines reaction mechanism of pentene cracking.