Brønsted activity of two-dimensional zeolites compared to bulk materials.

On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al3+ , Ga3+, Fe3+, B3+) Zeolites in the Methanol‐to‐Hydrocarbons Reaction

The influence of framework substituents (Al3+, Ga3+, Fe3+ and B3+) and morphology (bulk vs. nanometer-sized sheets) of MFI zeolites on the acidity and catalytic performance in the methanol-to-hydrocarbons (MTH) reaction was investigated. The Brønsted acid density and strength decreased in the order Al(OH)Si>Ga(OH)Si>Fe(OH)Si≫B(OH)Si. Pyridine 15N NMR spectra confirmed the differences in the Brø...

Acidity of two-dimensional zeolites.

Hybrid quantum mechanics:molecular mechanics (QM/MM) calculations of absolute deprotonation energies are performed with periodic boundary conditions for Brønsted sites of aluminosilicate bilayers with various Al/Si ratios (two-dimensional zeolite). The supercell method is applied and density functional theory is used. Much lower values are obtained (1042, 1069 and 1091 kJ mol(-1) for Al/Si = 1/...

Catalytic Behavior of Brønsted Acid Sites in MWW and MFI Zeolites with Dual Meso- and Microporosity

The catalytic behavior of Brønsted acid sites in three acidic zeolite materials (one MWW and two MFI zeolites) containing dual meso-/microporosity was studied using ethanol dehydration and monomolecular conversion of propane and isobutane as probe reactions. The meso-/microporous MWW zeolite, MCM-36 or pillared MWW, consists of a zeolitic layer structure, with independent microporosity and meso...

Brønsted acid sites based on penta-coordinated aluminum species

Zeolites and amorphous silica-alumina (ASA), which both provide Brønsted acid sites (BASs), are the most extensively used solid acid catalysts in the chemical industry. It is widely believed that BASs consist only of tetra-coordinated aluminum sites (AlIV) with bridging OH groups in zeolites or nearby silanols on ASA surfaces. Here we report the direct observation in ASA of a new type of BAS ba...

NanoscaleChemical Imaging of Brønsted Acid Sites in Zeolites: Strength, Accessibility and Reactivity