Olefin oligomerization by main group Ga3+ and Zn2+ single site catalysts on SiO2

Abstract

In heterogeneous catalysis, olefin oligomerization is typically performed on immobilized transition metal ions, such as Ni2+ and Cr3+. Here we report that silica-supported, single site catalysts containing immobilized, main group Zn2+ and Ga3+ ion sites catalyze ethylene and propylene oligomerization to an equilibrium distribution of linear olefins with rates similar to that of Ni2+. The molecular weight distribution of products formed on Zn2+ is similar to Ni2+, while Ga3+ forms higher molecular weight olefins. In situ spectroscopic and computational studies suggest that oligomerization unexpectedly occurs by the Cossee-Arlman mechanism via metal hydride and metal alkyl intermediates formed during olefin insertion and β-hydride elimination elementary steps. Initiation of the catalytic cycle is proposed to occur by heterolytic C-H dissociation of ethylene, which occurs at about 250 °C where oligomerization is catalytically relevant. This work illuminates new chemistry for main group metal catalysts with potential for development of new oligomerization processes.

Dehydroaromatization Pathway of Propane on PtZn/SiO2 + ZSM-5 Bifunctional Catalyst

“…The structure of the Ga/Al 2 O 3 catalyst characterized by in situ XAS is reported in Figure . Figure a shows that the XANES energy of the Ga­(AcAc) 3 reference and Ga/Al 2 O 3 is 10.377 and 10.375 keV, respectively, which is consistent with six-coordinate octahedral Ga 3+ and four-coordinate Ga 3+ reported in prior studies. − The EXAFS spectra were fitted to determine the coordination number and bond distance of the catalysts. The lower intensity of the first shell Ga–O scattering of Ga/Al 2 O 3 compared with that of Ga­(AcAc) 3 is suggestive of a lower coordination (Figure b).…”

“…Similar XANES and EXAFS have been reported for Ga/SiO 2 propane dehydrogenation catalysts. 41,42 Propane Conversion over ZSM-5 and 3% Ga/Al 2 O 3 . The product selectivity of 5% propane at 550 °C over Ga/Al 2 O 3 and ZSM-5 is shown in Table 2.…”

High-loading Ga-exchanged MFI zeolites as selective and coke-resistant catalysts for nonoxidative ethane dehydrogenation

“…1–9 In the field of catalysis, isolated metal hydrides on solid supports have been recognized as key species for hydrogenation and dehydrogenation reactions using heterogeneous catalysts since the 1970s. 7,8 On metals 10–16 and metal oxides, 17–25 H 2 is cleaved in a homolytic or heterolytic manner to form metal–hydrogen (M–H) bonds. However, their analysis is difficult owing to the complexity of the surface structures of metals/metal oxides, as well as the instability of generated hydride species.…”

C-Heterogenized Re Nanoparticles as Effective Catalysts for the Reduction of 4-Nitrophenol and Oxidation of 1-Phenylethanol

“…Rhenium complexes have become relevant catalysts in the oxidation of various organic compounds, such as olefins [27], ketones [28,29] and alcohols [30]. High valent oxo-rhenium complexes have also been successfully used in the activation of C-H bonds of aromatic and saturated hydrocarbons [31][32][33][34][35][36][37][38].…”