Phenol Tautomerization Catalyzed by Acid‐Base Pairs in Lewis Acidic Beta Zeolites: A Computational Study

Abstract

We investigate the tautomerization of phenol catalyzed by acid‐base active pair sites in Lewis acidic Beta zeolites by means of density functional calculations using the M06‐L functional. An analysis of the catalytic mechanism shows that hafnium on the Beta zeolite causes the strongest absorption of phenol compared to zirconium, tin, and germanium. This can be rationalized by the highest delocalization of electron density between the Lewis site and the oxygen of phenol which can in turn be quantified by the perturbative E(2) stabilization energy. The reaction is assumed to proceed in two steps, the phenol O−H bond dissociation and the protonation of the intermediate to form the cyclohexa‐2,4‐dien‐1‐one product. The rate determining step is the first one with a free activation energy of 26.3, 25.0, 22.1 and 22.7 kcal mol−1 for Ge‐Beta, Sn‐Beta, Zr‐Beta, and Hf‐Beta zeolites, respectively. The turnover frequencies follow these reaction barriers. Hence, the intrinsic catalytic activity of the Lewis acidic Beta zeolites studied here is in the order of Hf‐Beta≈Zr‐Beta>Sn‐Beta> Ge‐Beta for the tautomerization of phenol.

Computational insights into the zeolite-supported gold nanocluster-catalyzed ethanol dehydrogenation to acetaldehyde

“…These methods and basis sets have shown to be appropriate for metal clusters supported by zeolites in the literature. [44][45][46] All calculations were performed using the Gaussian 09 program. 47 In addition, non-covalent interaction (NCI) analysis was performed with the Multiwfn program 48,49 and visualized using the VMD program.…”

Synthesis and Catalytic Applications of Advanced Sn‐ and Zr‐Zeolites Materials

“…[ 191 ] After further analysis, it was found that this reaction contained two steps, the dissociation of O‐H in phenol and the subsequent protonation of the intermediate, where the first one was the rate‐determining step. [ 192 ]…”

“…[191] After further analysis, it was found that this reaction contained two steps, the dissociation of O-H in phenol and the subsequent protonation of the intermediate, where the first one was the rate-determining step. [192] N-alkylation reaction of aniline with benzyl alcohol was attempted over various silicates (MFI and Beta) with Sn, Ti, Zr, and Hf active sites. [22] Among these zeolites, Zr-Beta and Hf-Beta exhibited excellent activity and selectivity for this conversion.…”