Key role of the pore volume of zeolite for selective production of propylene from olefins

Abstract

A plausible reaction mechanism for propylene (C(3)H(6)) production from ethylene (C(2)H(4)) was investigated, based on the amounts of effluent hydrocarbons and hydrocarbons produced in the pores of SAPO-34. Propylene was produced via an oligomerization-cracking mechanism. On the basis of this mechanism, the conversions of C(2)H(4), pentenes, and hexenes were examined. The catalytic performance was compared, in order to investigate the role of the pore volume of zeolites with 8-, 10-, and 12-membered rings in the selective production of C(3)H(6). The selectivity for C(3)H(6) was crucially dependent upon the pore volume of the zeolite. Highly selective production of C(3)H(6) from olefins (C(2)H(4), pentenes, and hexenes) can be accomplished by employing a new concept: adjusting the pore volume of a zeolite to accommodate the volume of an olefin and/or its carbenium cations, as opposed to a conventional molecular sieve approach. For example, an unimolecular cracking of pentenes into C(3)H(6) and C(2)H(4) involving primary cations can be controlled by the pore volume of a zeolite.

The substrate binding cavity of particulate methane monooxygenase from Methylosinus trichosporium OB3b expresses high enantioselectivity for n-butane and n-pentane oxidation to 2-alcohol

“…Therefore, the cavity reasonably explains the recognition of those substrates to express enantioselectivity. The importance of cavity volume for expressing product selectivity has also been demonstrated in some reactions within pores of zeolites (Corma et al 1997;Koyama et al 2010). Compared with zeolite pore, a protein cavity of pMMO is expected to have more flexible structure.…”

Controlling coke deactivation and cracking selectivity of MFI zeolite by H3PO4 or KOH modification

“…Koyama et al [41] investigated the role of the pore volume of zeolites with 8-, 10-and 12-membered rings for the selective production of propylene from other olefins, by determining the optimum zeolite cavity volume (152-223 Å 3 ) for the formation of the octylcarbenium ion which produces propylene. Furthermore, the local Al distribution in the MFI framework affects the product composition during olefin cracking [39].…”

Shape-Selective Catalysis Determined by the Volume of a Zeolite Cavity and the Reaction Mechanism for Propylene Production by the Conversion of Butene Using a Proton-Exchanged Zeolite

“…According to DFT calculations in our previous work (ref 3 6). Reaction Mechanism for the Conversion of C 2 H 4 into C 3 H 6 at the Initial Stage.…”

“…As reported previously, the volume of the zeolite cavity plays a key role in the selective production of C 3 H 6 in the conversion of C 2 H 4 , pentenes, and hexenes. 3 To examine the effect of D i on the C 3 H 6 selectivity in the conversion of 1-butene, the selectivity shown in Figure 2 was plotted against the D i of 8-, 10-, and 12-MR zeolites, in Figures 3(a), (b), and (c), respectively. The selectivity for C 3 H 6 strongly depended on the D i of the zeolites in the conversion of 1-butene as well.…”

“…As mentioned in Section (3), the 8-, 10-, and 12-MR zeolites that had the maximum selectivities for C 3 H 6 in the conversion of 1-butene had D i values of 7.31 Å (SAPO-34, 8-MR), 6.25 Å (Ferrierite, 10-MR), and 6.62 Å (β, 12-MR). A D i of 6.25−7.31 Å corresponded to spheres with volumes of 128−204 Å3 , which is almost the same size as the octyl carbocations. These experimental results indicate that highly selective production of C 3 H 6 from butene can be accomplished by adjusting the volume of the zeolite cavity to match that of the octyl carbocations.…”