Search

To reveal the influence of acid sites with different spatial locations of USY zeolite with different micro-/mesoporous structures and Si/Al ratio, catalytic cracking of methylcyclohexane on the zeolites is employed to study the synergism effects of acid sites and porous structures ("active region") in the hierarchical USY zeolites. The results showed that the hierarchical USY zeolites have increased numbers of accessibly strong Brønsted acid sites and greatly enhanced diffusion ability due to the hierarchical pore-structure, resulting in mainly monomolecular protolytic scission in cracking reactions and less bimolecular hydrogen transfer. The isomerization reaction is from intramolecular transalkylation and the isomerics are the intermediates of the cracking reaction. The protolytic cracking that occurs in hierarchical high-silica USY-zeolites follows the Haag-Dessau cracking. [ABSTRACT FROM AUTHOR]

Three industrially modified Y zeolites with a hierarchical structure were characterized by XRD, N2 adsorption–desorption, SEM, TEM, 27Al-/29Si-NMR, in situ pyridine-FTIR, and NH3-TPD techniques. The industrial hydrocracking catalyst of light diesel oil was prepared by kneading and extruding the mixture of 10 wt.% industrially modified zeolite, commercial alumina, nickel nitrate, and molybdenum oxide. The small amount of hierarchical Y zeolite in the hydrocracking catalyst plays a key role, resulting in selective hydrogenation of naphthalene and further ring-opening activity. The mesoporous structure of the zeolites provided an effective interface and improved the accessibility of acid sites to bulky reactants. [ABSTRACT FROM AUTHOR]

Pd nanoparticles (NPs) supported on amine-functionalized layered double hydroxides (LDHs) (Pd/NH2-LDH-NS) were successfully obtained by implanting aminopropyltriethoxysilane (APTS) on MgAl LDH nanosheets (LDH-NS), followed by impregnating [Pd(NH3)4]Cl2 and reduction with NaBH4. The physicochemical characteristics of the obtained Pd/NH2-LDH-NS were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR),, N2 adsorption–desorption, inductive coupled plasma (ICP), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy(XPS), and their catalytic performance was tested in the selective oxidation of benzyl alcohol with molecular oxygen under solvent-free and base-free conditions. The results showed that the implanted –NH2 groups can promote the dispersion of the supported Pd NPs via complexation of the implanted –NH2 groups to Pd NPs, and they can increase the surface basicity of the catalysts, thus enhancing the catalytic activity and selectivity to benzylaldehyde. Pd/NH2-LDH-NS exhibited enhanced catalytic activity (31.6%) and selectivity (>98%) compared to the corresponding Pd/LDH-NS, Pd/LDH, Pd/SiO2, and Pd/Al2O3. Moreover, Pd/NH2-LDH-NS was remarkably stable and could be reused at least four times without a significant loss in activity and selectivity. [ABSTRACT FROM AUTHOR]

To improve the catalytic performance of zeolite catalysts in reactions involving bulky molecules, a series of mesoporous Beta zeolite were prepared using organic functionalized fumed silica as the silicon source, which were thoroughly characterized in terms of porosity and acidity. The peaks in X-ray diffraction (XRD) patterns showed broadening, and the external surface area and mesoporosity increased progressively when the content of organic functionalization increased. An infrared (IR) spectroscopy study of adsorbed probe molecules, including pyridine (Py-IR), 2,6-ditertbutylpyridine (DTBPy-IR) and pivalonitrile (Pn-IR), showed that the improvement of mesoporosity increased the accessibility of acidic sites. In the catalytic benzylation of naphthalene with benzyl chloride (BC) over the mesoporous Beta zeolite catalysts, the conversion of BC was significantly increased when the accessibility of Brönsted acid sites improved. The increase of mesoporosity not only improved the diffusion ability of the reactants and products, but also increased the accessibility of acid sites, which greatly enhanced the activity of the mesoporous Beta zeolite catalysts. It is highlighted that the interdependence of mesoporosity, acid type, acid concentration, and strength of the mesoporous Beta zeolites on the catalytic performance in the benzylation of naphthalene with BC was comprehensively studied. [ABSTRACT FROM AUTHOR]