Oligomerization of Light Olefins to Gasoline: An Advanced NMR Characterization of Liquid Products

Using multiple ¹H and ¹³C NMR spectroscopic techniques, we have investigated the C8 cut from samples of liquid products obtained by the oligomerization of light olefins over solid phosphoric acid (SPA) and MTW zeolite. The carbon species present, CH_<i>n</i> (<i>n</i> = 0–3), were identified by DEPT NMR and quantified using inverse-gated decoupled ¹³C NMR spectra. The olefinic protons and carbons as well as the types of olefins were quantified. ¹³C NMR shows that the amount of methyl carbons is similar for both catalysts but that methylene and methyne carbon distributions are different. The product obtained over MTW catalyst showed higher quantities of quaternary olefins, likely from type V tetrasubstituted olefins, compared to that over SPA catalyst. In addition, 2D NMR has also been attempted to understand the proton and carbon connectivities and confirmed the presence of type I and II olefins

Production of Propylene from 1-Butene on Highly Active “Bi-Functional Single Active Site” Catalyst: Tungsten Carbene-Hydride Supported on Alumina

1-Butene is transformed in a continuous flow reactor over tungsten hydrides precursor W–H/Al₂O₃, <b>1</b>, giving a promising yield into propylene at 150 °C and different pressures. Tungsten carbene-hydride single active site operates as a “bi-functional catalyst” through 1-butene isomerization on W-hydride and 1-butene/2-butenes cross-metathesis on W-carbene. This active moiety is generated in situ at the initiation steps by insertion of 1-butene on tungsten hydrides precursor W–H/Al₂O₃, <b>1</b> followed by α-H and β-H abstraction

Metallacyclobutane Substitution and Its Effect on Alkene Metathesis for Propylene Production over W–H/Al₂O₃: Case of Isobutene/2-Butene Cross-Metathesis

Cross metathesis between 2-butenes and isobutene yielding the valuable products propylene and 2-methyl-2-butene has been investigated at low pressure and temperature using <b>WH</b>_<b>3</b><b>/Al</b>_<b>2</b><b>O</b>_<b>3</b>, a highly active and selective catalyst. Two parallel catalytic cycles for this reaction have been proposed where the cycle involving the less sterically hindered tungstacyclobutane intermediates is most likely favored. Moreover, it has been found that the arrangement of substituents on the least thermodynamically favored tungstacyclobutane governs the conversion rate of the cross metathesis reaction for propylene production from butenes and/or ethylene

Crystallization Mechanism of Zeolite UZM‑5

A reliable formation pathway for UZM-5 zeolite crystals in the presence of tetraethylammonium, tetramethylammonium, and Na⁺ ions at 150 °C has been proposed based on the ¹³C MAS NMR and IR spectra of a series of solid products recovered as a function of time during the crystallization process, as well as on the crystal structure of as-made UZM-5 determined using synchrotron powder X-ray diffraction and Rietveld analyses. The nucleation of this cage-based small-pore zeolite begins with the construction of the largest 26-hedral <i>lta</i>-cages among its four different structural units. The next step is the attachment of 14-hedral <i>wbc</i>-cages to the preorganized <i>lta</i>-cage at shared 6-rings in an appropriate orientation that will allow the growth of two <i>wbc</i>-cage layers linked by 8-hedral <i>rth</i>-cage formation along both <i>a</i> and <i>b</i> axes. The resulting interlayer space is readily converted to a layer of <i>lta</i>-cages by interconnecting two opposing <i>wbc</i>-cages, with the concomitant formation of interlayer <i>d4r</i>-cages and 8-rings. Over the outer surface of the resulting UZM-5 nuclei, which resembles one-half of an <i>lta</i>-cage, the crystal growth may take place in a self-assembled manner as described above