Microwave-Assisted Air Epoxidation of Mixed Biolefins over a Spherical Bimetal ZnCo-MOF Catalyst.

Here, we report the synthesis of spherical bimetal ZnCo-MOF materials by a hydrothermal rotacrystallization method and their catalytic activity on the air epoxidation of mixed biolefins enhanced by microwaves. The structural and chemical properties of the ZnCo-MOF materials were fully characterized by XRD, IR, SEM, TG, XPS, and NH3-TPD. The morphology of the material exhibited a three-dimensional spherical structure. From an NH3-TPD test of the ZnCo-MOF catalyst, it could be concluded that the Zn0.1Co1-MOF-H-150 rpm material had the highest acidic content and the strongest acidity among the catalysts synthesized by different methods, which gave the best performance in the epoxidation of mixed biolefins. The air epoxidation reaction was carried out under atmospheric pressure and microwave conditions, in the absence of any initiator or coreducing agent. Moreover, the Zn0.1Co1-MOF catalyst could be recycled six times without reducing the catalytic activity significantly, which showed the stability of spherical catalyst material under microwaves.

Highly efficient crystallization of AlPO4-5 accelerated by a rotating hydrothermal synthesis route.

Compared with static hydrothermal synthesis, the crystallization rate of an AlPO4-5 molecular sieve has been accelerated distinctly by a rotating hydrothermal synthesis route with obviously decreased crystal particle size, which is assumed to be ascribed to the increased nucleation centers, accelerated crystal nucleation and growth processes; five-coordinated Al is dominant in the initial reaction gel, and the assembly from amorphous Al species to long-range ordered crystals is mainly contributed by the conversion from five-coordinated Al to four-coordinated Al.

High-Rota Synthesis of Single-/Double-/Multi-Unit-Cell Ti-HSZ Nanosheets To Catalyze Epoxidation of Large Cycloalkenes Efficiently.

This work first reports high-efficiency epoxidation of large cycloalkenes (carbon number ≥ 7) with tert-butyl hydroperoxide (TBHP) over single-/double-/multi-unit-cell nanosheet-constructed hierarchical zeolite, which is synthesized by one-step hydrothermal crystallization using piperidine as the structure-directing agent of the microporous structure. The excellent catalytic property of the material is ascribed to its unique structural characteristic. Plenty of surface titanols or silanols on the surface of MWW nanosheets are beneficial for the formation of transition-state intermediates; a large number of intercrystalline mesopores in the shell of the material not only facilitate the formation of the intermediate for TBHP but also have nearly no hindrance for the diffusion and mass transfer of bulky cycloalkene to the above intermediates; the 12-MR side cups penetrating into the crystals from the external surface are exposed as much as possible to the reaction system because of the single-/double-/multi-unit-cell MWW nanosheet, serving as the primary reaction space for the epoxidation of bulky cyclic alkene and oxidants and providing enough space for the transition state of Ti-OOtBu and bulky cycloalkane. Moreover, an efficient calcination-free catalytic reaction-regeneration method is developed to overcome the challenge for the recyclability of microporous Ti-zeolite in the catalytic epoxidation of bulky cycloalkenes.

Microwave-activated Ni/carbon catalysts for highly selective hydrogenation of nitrobenzene to cyclohexylamine.

Biocarbon supported Ni catalysts have been prepared by facile impregnation of Ni species by microwave-heating and used for selective hydrogenation of nitrobenzene to cyclohexylamine. These catalysts were characterized by X-ray diffraction, Raman spectra, N2 sorption measurement, X-ray photoelectron spectroscopy, temperature programmed reduction of H2 and H2 temperature-programmed desorption. The morphology and particle size of catalysts were imaged by scanning electron microscope and transmission electron microscope. For the hydrogenation of nitrobenzene to cyclohexylamine, 10%Ni/CSC-II(b) exhibits the best catalytic activity to achieve 100 mol% conversion of nitrobenzene and 96.7% selectivity of cyclohexylamine under reaction conditions of 2.0 MPa H2 and 200 °C, ascribed to high dispersion of Ni species and formation of nanosized Ni particles on the support aided by microwave-heating. Thus-prepared Ni/CSC catalyst is greatly activated, in which the addition of precious metal like Rh is totally avoided.

One-pot rota-crystallized hollownest-structured Ti-zeolite: a calcination-free and recyclable catalytic material.

A hydrothermal rota-crystallization method is developed for the one-step synthesis of a hollownest-structured zeolite precursor with the shell composed of autogenously-intergrown MWW nanosheet crystals containing a large number of stacking-pores without using any porogen or hard scaffold. This material possesses a large external surface area. By simple acid washing, the resultant Ti-containing catalyst can be directly used in the epoxidation of alkenes with hydrogen peroxide. The excellent catalytic activity over the Ti-HSZ catalyst is assumed to be due to the exposure of more Ti active sites over the MWW nanosheet crystals in the shell of the catalyst. More importantly, this Ti-HSZ catalyst washed with H2O2/ethanol solution has been reused 6 times without an appreciable decrease in both the conversion of the allyl chloride and the selectivity of the epichlorohydrin, which is ascribed to the structural stability of the hollownest-structured zeolite.

One-step DGC assembly and structural characterization of a hairy particle zeolite-like organic-inorganic hybrid as an efficient modifiable catalytic material.

Organic-inorganic hybrid microporous crystalline molecular sieves, extending the application of conventional zeolites in the fields of selective catalysis and adsorption, have aroused great interest in chemists. However, the complicated and difficult synthesis of organic-inorganic hybrid microporous molecular sieves by using a conventional hydrothermal method has hindered the rapid development of this field. The present work describes the recent progress in the synthesis of a hairy particle zeolite-like organic-inorganic hybrid with the high organic group content by one-step dry-gel conversion (DGC) assembly of organic Si, inorganic Si and other inorganic species without any organic template, which is proven to be efficient, economical, simple, and controllable. Thus-synthesized hybrid materials, as we know, with the highest organic group content reported in the literature, can be bestowed with modifiable catalytic activities by different treatments. This study will be applicable for the development of organic-inorganic hybrid catalytic materials.