Theoretical investigation on acetylene cyclotrimerization catalysed by TiO₂ and Ti

Abstract

The reaction mechanisms for acetylene cyclotrimerization using TiO 2 and Ti catalysts were studied by the density functional theory (DFT) method. Interestingly, the reaction catalysed by TiO 2 occurs on the potential energy surface (PES) with a singlet state. For the same reaction catalysed by Ti, spin-orbit coupling (SOC) calculations were performed to discuss spin inversion between the triplet and singlet PESs. The chance that an electron hops in the vicinity of the minimum-energy crossing point (MECP) was verified regarding the Landau-Zener model. The possibilities of single (P ISC 1 ) and double (P ISC 2 ) at MECP1 (SOC = 253.38 cm −1 ) are about 0.35 and 0.46, respectively. The energetic span model developed by Kozuch was applied in the above reactions. The turnover frequency (TOF)-determining transition state (TDTS) and TOF-determining intermediate (TDI) were verified. The TOF value indicates that Ti is a more active catalyst compared with TiO 2 in C 2 H 2 cyclotrimerization.

Cyclotrimerization of Acetylene on Clusters Con+/Fen+/Nin+(n = 1–16)

“…However, the low yields and byproducts of aromatic derivatives may impede industrial applications of these reactions. Although the reaction of acetylene to benzene is exothermic, relatively high temperatures (above typically 400 °C) are currently used to overcome the energy barrier for partial activation of the CC bond to form the benzene ring. − On this background, extensive experimental and theoretical studies have been conducted on transition metal atoms and ions, − oxides, − complexes, − and supported metal catalysts (Pd n /MgO, Rh/MgO, Ag/MgO, Ni/SiO 2 ) − for the purpose of identifying for efficient catalysts for this cyclotrimerization.…”