A joint experimental–theoretical study on trimethylphosphine adsorption on the Lewis acidic sites present in TS-1 zeolite

Lewis and Brönsted acidic sites in M4+-doped zeolites (M=Ti, Zr, Ge, Sn, Pb) as well as interactions with probe molecules: A DFT study

“…In agreement with the previous studies [27][28][29], the cluster models containing 17-T sites were chosen to represent the local structures of MFI-type zeolite (Fig. 1).…”

“…The standard 6-31G(d) basis set was applied to the elements with atomic numbers below 21. As to Ti, Ge, Sn, Pb and Zr, their core electrons were represented by LANL2DZ effective core potential (ECP) [43,44] and valence electrons by LANL2DZ basis set, respectively [17,[27][28][29]. The combined basis sets are denoted as B1 (default).…”

“…Generally, the larger the M 4+ radii, the more unfavorable the substitutions. The LUMO energies, fukui functions (f M ), absolute electronegativity ( ) have been used to characterize the Lewis acidities of zeolites [28,[30][31][32]35,36,55]. The electrophilic fukui functions (f M + ) are approximated to be [56][57][58],…”

“…In the previous works [27][28][29][30], we studied the Lewis and Brön-sted acidities of TS-1 and Ti-MCM-22 zeolites, see Scheme 1. The Lewis acidities of Ti 4+ -doping zeolites have also received attention from other groups [31][32][33][34][35], while few reports have been given on other tetravalent ions (M 4+ ).…”

In-situ 31P MAS NMR probing of the active centers in Ti silicalite molecular sieve

“…During the past three decades, numerous research groups have been focusing on the synthesis, reaction performance, and especially the characterization of the active centers of TS-1 zeolite [7][8][9][10]. Different methods, such as XRD, Raman, power diffraction, solid state NMR and theoretical calculations, have been used to identify the catalytic active centers of TS-1 zeolite [10][11][12][13][14][15][16]. It is generally accepted that the framework Ti of the zeolite, most likely in a tetrahedral coordination, is usually considered as the active titanium species.…”