Search

Graphical abstract Highlights • A new core-shell zeolite catalyst with a hierarchical pore network structure. • A high thermal and hydrothermal stability for the industrial requirements. • Hierarchically cracking of bulky molecules over the core-shell zeolite catalyst. • Heavy oil conversion and gasoline yield increased by 1.8 wt% and 8.9 wt%. Abstract The conversion of the heavy fractions of crude oil into transportation fuels and chemical feedstocks is still a severe challenge for fluid catalytic cracking (FCC) technology, in which geometrical parameters of the catalyst are of key importance to the accessibility for reactant and product molecules to travel through the pore space. Here a new core-shell zeolite catalyst with hierarchical pore network from macro- via meso- to micropores is developed by controlling overgrowth of another zeolite shell on the surface of a commercial Y-zeolite. The zeolite shell is a distinctive nano ZSM-5 crystals. The core-shell zeolite catalyst has a high thermal and hydrothermal stability because of high crystallinity, which can meet the industrial requirements. More importantly, the heavy oil can be cracked by the designed zeolite catalyst step-by-step into the required products. The meso- and macroporous shell facilitates pre-cracking the large molecules in heavy oil into moderate ones which can directly diffuse into the micropores of the Y-zeolite to be cracked selectively into the desired products. Both the pore structure network and acid sites distribution of the core-shell zeolite catalyst in the FCC processing are completely harmonious. As a practical example, the catalytic cracking of VGO heavy oil is actualized over the new catalyst. The results showed that the conversion of heavy oil and the yield of gasoline increased by 1.8 wt% and 8.9 wt% respectively, LPG decreased by 6.9 wt%, iso -paraffins and olefins in gasoline fraction increased by 5.21 wt% and 6.31 wt% respectively, aromatics decreased by 11.55 wt%, because of the graduated cracking in core-shell zeolite and returned isomerization in nano ZSM-5, compared with commercially industrial FCC catalyst. [ABSTRACT FROM AUTHOR]

Highlights: [•] Asymmetric chiral Ru(II) complexes were encapsulated in zeolite MY. [•] The complex encapsulated in LiY has higher ee selectivity than the homogenous. [•] The alkali metal cation exchanged Y has different host effect to the complex. [•] The reactivity was supported by DFT calculation and UV–vis spectra ananlysis. [Copyright &y& Elsevier]

Abstract: Y-Beta zeolite composites denoted as HS-FBZ (High-Silica-Faujasite-Beta-Zeolite) were synthesized hydrothermally using high silica Y as precursor and characterized by XRD, N2 adsorption, SEM, HRTEM, NH3-TPD and FT-IR spectra of pyridine. The results reveal that the different ratios of Y and Beta zeolites in the composites induced the change of surface areas, pore diameters and acid properties of HS-FBZ, and the extended Beta layers on the zeolite Y surface were observed. The composite exhibited an excellent hydrocracking activity for heavy oil. Compared with the corresponding physical mixture of Y and Beta zeolites, the zeolite composite as a hydrocracking catalyst for vacuum gas oil increased the heavy naphtha yield by 5.61wt% and the jet fuel yield by 11.52wt%. [Copyright &y& Elsevier]

A microspherical mesostructured zeolite (MMZ-5) with MFI-topological frameworks is employed. In-situ FT-IR spectra of pyridine and 2, 6-di-tert-butylpyridine have indicated that almost all of the acid sites are located on the zeolitic external surface, which are favorable for access of reactive large molecules. This key effect, along with the reduced diffusion and steric limitation, has been proposed to be main the reason for the enhanced catalytic activity, selectivity and stability exhibited in benzylation of aromatics with benzyl chloride. The need for optimized characterization of the mesoporous surface acidity for different aromatics is highlighted. [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]

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]