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

Abstract

The role of the zeolite cavity in the production of C 3 H 6 from butene was investigated using various zeolites with pore structures of 8-, 10-, and 12-membered rings (MRs). The reaction mechanism is discussed on the basis of which octyl carbocations produced C 3 H 6 at low conversions of butene. The selectivity for C 3 H 6 was highly dependent on the volume of the zeolite cavity but not on the entrance pore diameter. The optimum cavity volumes of zeolites with 8-, 10-, and 12-MR entrance pore structures were similar, while the highest C 3 H 6 selectivity among the zeolites was different. The most selective production of C 3 H 6 can be accomplished by matching the volume of the specific octyl carbocation to that of the zeolite cavity. This concept can be employed to explain the selective production of C 3 H 6 according to a proposed reaction model. Furthermore, the reaction mechanism for the production of C 3 H 6 from C 2 H 4 was also investigated at low conversion of C 2 H 4 . C 3 H 6 was produced by the β-scission of the same specific octyl carbocations in the conversions of both butene and C 2 H 4 .

Self-Radiolysis of Tritiated Water Stored in Zeolites 4A: Production and Behavior of H2 and O2

“…3 He Release 3 He is an interesting species as it is released by Tritium decay and is not a reactive gas.…”

“…We synthetized chemically pure tritiated water by isotopic exchange. 250 cm 3 and 300 cm 3 of non-tritiated milli-Q water were introduced in two 560 cm 3 316L stainless steel containers. We then introduced gaseous T 2 (90% T 2 , 5 % N 2 , 2 % 3 He, 1 % O 2 , 1 % DT, 1 % HT) at a pressure of about 800 mbar.…”

Adsorptive characterization of porous solids: Error analysis guides the way

“…Second MOF is the fully microporous UiO-66 [18], which also gained significant attention because of excellent stability and interesting properties [19][20][21][22]. Sigma-1, a microporous zeolite and member of the DDR structural topology, known for its high separation performance in membrane and adsorptive processes, http incorporates aluminium into the framework, making the material also suitable for catalysis [23][24][25]. c-Alumina is chosen as representative for mesoporous metal-oxide supports, which are used frequently in heterogeneous catalysis [26][27][28].…”

Influence of zeolite pore structure on product selectivities for protolysis and hydride transfer reactions in the cracking of n-pentane

“…Derouane and co-workers proposed that molecules and their direct curved framework environment in zeolites tended to reciprocally optimize their van der Waals interactions, 28 and that the van der Waals energy between the molecules and wall surface of then zeolite cavity was proportional to the heat of sorption of hydrocarbons on zeolites. 10,11,29 These results make us hypothesize that the cavity volume of the zeolite influences the catalytic activity and the product selectivity for n-pentane cracking. 10,11,29 When 1-hexene cracking was carried out using various zeolites, the turnover frequency for C 3 H 6 formation (TOF(C 3 H 6 )) was related to the van der Waals energy between C 6 H 13 + carbenium ions and the wall of the zeolite cavity; log (TOF(C 3 H 6 )) was proportional to the van der Waals energy.…”

“…The mean crystal diameters of the materials were estimated by measuring the sizes of 100 crystals in the obtained SEM images. The number of acidic protons over aluminosilicate molecular sieves of ZSM-22, ZSM-23, ZSM-5, Nu-87, ZSM-11, and Y were determined by measuring the SiO 2 /Al 2 O 3 ratio using 29 Si magic-angle spinning nuclear magnetic resonance ( 29 Si MAS NMR), and the degree of NH 4+ substitution was calculated from the amount of residual Na + . The average crystal size of all zeolites was smaller than about 1 mm.…”