With the help of hydrogen bonding and π⋯π stacking, the small molecular clusters in the impregnating solution was induced to self-assemble and form a new Ni–Mo polyoxometalate based on octamolybdate ...with a molecular formula of Ni(pyz)
6
Mo
8
O
26
(pyz)
2
⋅10H
2
O (pyz = pyrazole). The polyoxometalate was structurally characterized detailed by various technologies, and its sulfide was also characterized to make a preliminary study to explore the use of it as a potential NiMoS active phase precursor. Much more NiMoS active phase and higher catalytic activity of the Ni–Mo sulfided catalyst was found, and the structure-directing effects can account for the phenomenon. The results show the Ni–Mo polyoxometalate Ni(pyz)
6
Mo
8
O
26
(pyz)
2
⋅10H
2
O can make a superior precursor to prepare the hydrodesulfurization catalyst, and it provides a new preparation methodology to the rational design and controllable preparation of superior hydrodesulfurization catalysts.
Graphical Abstract
•Monodisperse nickel nanoparticles (NPs) with different size were synthesized via the thermal decomposition approach.•The size of nickel NPs can easily be controlled by changing synthetic ...conditions.•The possible growth mechanism of nickel NPs was proposed.•The as-synthesized nickel NPs exhibited superparamagnetism characteristics at room temperature, and the saturation magnetization increased significantly with increasing size of the nickel NPs.•The dehydrogenation reaction of cyclohexane on nickel NPs was structure sensitive reaction.
Monodisperse nickel nanoparticles (NPs) with different size were synthesized via the thermal decomposition approach using nickel acetylacetonate as precursors and trioctylphosphine as surfactant in oleylamine. The structure and morphology of as-synthesized nickel NPs were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and selected area electron diffraction (SAED). The surface states of as-synthesized nickel NPs were characterized by Fourier transform infrared (FT-IR) spectra. The textural properties of as-synthesized nickel NPs were characterized by N2 adsorption–desorption. The size of as-synthesized nickel NPs was found to be easily controlled by changing synthetic conditions, including P:Ni precursor ratio, reaction temperature, reaction time and oleylamine quantity, and the possible growth mechanism of nickel NPs was proposed. In addition, the magnetic measurements showed that the as-synthesized nickel NPs exhibited superparamagnetism characteristics at room temperature, and the saturation magnetization increased significantly with the increase in nickel NPs’ size. Finally, the size-dependent catalytic properties of nickel NPs for cyclohexane dehydrogenation reaction were studied. The results demonstrated that the catalytic activity can be enhanced by decreasing the size of NPs, which indicated that the dehydrogenation reaction of cyclohexane on nickel NPs was structure sensitive reaction.
A KF/γ-Al2O3 solid base catalyst was prepared by wet impregnation and applied to the synthesis of eugenol ethyl ether (EEE) from eugenol and diethyl carbonate. By measuring the yield of eugenol ethyl ...ether, we investigated the effects of the catalyst active component, impregnation temperature, KF impregnation concentration, impregnation time, and calcination temperature on catalyst performance. The results showed that the KF/γ-Al2O3 catalyst can adequately facilitate the conversion of eugenol to EEE. The characterizations of the catalysts were examined by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterizations of EEE were examined by nuclear magnetic resonance spectrometry (H1-NMR), gas chromatography–mass spectrometer (GC-MS) and Fourier-transform infrared spectroscopy (FT-IR). It was found that the KF/Al2O3 catalyst (impregnation temperature 60 °C, KF impregnation concentration 40%, impregnation time 8 h, and calcination temperature 450 °C) showed the best effect. The yield of EEE remained 51.2% after recycling the supported catalyst three times.
A simple and novel synthesis process, one-step ionic liquid-assisted hydrothermal synthesis route, has been developed in the work to synthesize Bohemithe (γ-AlOOH) with flower-like structure. The ...samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope (SEM). Ionic liquid Omim+Cl−, as a template, plays an important role in the morphology and pore structure of the products due to its strong interactions with reaction particles. With the increase in the dosage of ionic liquid Omim+Cl−, the morphology of the γ-AlOOH was changed from initial bundles of nanosheets (without ionic liquid) into final well-developed monodispersed 3D flower-like architectures (Omim+Cl−=72mmol). The pore structure was also altered gradually from initial disordered slit-like pore into final relatively ordered ink-bottle pore. Furthermore, the proposed formation mechanism and other influencing factors such as reaction temperature and urea on formation and morphology of the γ-AlOOH have also been investigated.
The flower-like γ-AlOOH architectures composed by nanosheets with narrow size distribution (1.6–2.2μm) and uniform pore size (6.92nm) have been synthesized via a one-step ionic liquid-assisted hydrothermal route. Display omitted
•The γ-AlOOH microflowers were synthesized via an ionic liquid-assisted hydrothermal route.•Ionic liquid plays an important role on the morphology and porous structure of the products.•Ionic liquid can be easily removed from the products and reused in recycling experiments.•A “aggregation–recrystallization–Ostwald Ripening“formation mechanism may occur.
2-Phenylethanol is a specific aromatic alcohol with a rose-like smell, which has been widely used in the cosmetic and food industries. At present, 2-phenylethanol is mainly produced by chemical ...synthesis. The preference of consumers for "natural" products and the demand for environmental-friendly processes have promoted biotechnological processes for 2-phenylethanol production. Yet, high 2-phenylethanol cytotoxicity remains an issue during the bioproduction process.
Corynebacterium glutamicum with inherent tolerance to aromatic compounds was modified for the production of 2-phenylethanol from glucose and xylose. The sensitivity of C. glutamicum to 2-phenylethanol toxicity revealed that this host was more tolerant than Escherichia coli. Introduction of a heterologous Ehrlich pathway into the evolved phenylalanine-producing C. glutamicum CALE1 achieved 2-phenylethanol production, while combined expression of the aro10. Encoding 2-ketoisovalerate decarboxylase originating from Saccharomyces cerevisiae and the yahK encoding alcohol dehydrogenase originating from E. coli was shown to be the most efficient. Furthermore, overexpression of key genes (aroG
, pheA
, aroA, ppsA and tkt) involved in the phenylpyruvate pathway increased 2-phenylethanol titer to 3.23 g/L with a yield of 0.05 g/g glucose. After introducing a xylose assimilation pathway from Xanthomonas campestris and a xylose transporter from E. coli, 3.55 g/L 2-phenylethanol was produced by the engineered strain CGPE15 with a yield of 0.06 g/g xylose, which was 10% higher than that with glucose. This engineered strain CGPE15 also accumulated 3.28 g/L 2-phenylethanol from stalk hydrolysate.
In this study, we established and validated an efficient C. glutamicum strain for the de novo production of 2-phenylethanol from corn stalk hydrolysate. This work supplied a promising route for commodity 2-phenylethanol bioproduction from nonfood lignocellulosic feedstock.
(S)-N-Boc-3-hydroxypiperidine is an important intermediate of the anticancer drug ibrutinib and is mainly synthesized by the asymmetric reduction catalyzed by ketoreductase coupled with glucose ...dehydrogenase at present. In this study, the coexpression recombinant strains E. coli/pET28-K-rbs-G with single promoter and E. coli/pETDuet-K-G with double promoters were first constructed for the coexpression of ketoreductase and glucose dehydrogenase in the same cell. Then, the catalytic efficiency of E. coli/pET28-K-rbs-G for synthesizing (S)-N-Boc-3-hydroxypiperidine was found to be higher than that of E. coli/pETDuet-K-G due to the more balanced activity ratio and higher catalytic activity. On this basis, the catalytic conditions of E. coli/pET28-K-rbs-G were further optimized, and finally both the conversion of the reaction and the optical purity of the product were higher than 99%. In the end, the cell-free extract was proved to be a better catalyst than the whole cell with the improved catalytic efficiency of different recombinant strains. This study developed a better coexpression strategy for ketoreductase and glucose dehydrogenase by investigating the effect of activity ratios and forms of the biocatalysts on the catalytic efficiency deeply, which provided a research basis for the efficient synthesis of chiral compounds.
Melt blending is an effective way to prepare new composite materials, but most polymers are incompatible. In order to reduce the interfacial tension and obtain fine and stable morphology with ...internal symmetric micro-textures, suitable compatibilizers should be added to the blend. The two immiscible polymers, low-density polyethylene (LDPE) and polystyrene (PS), were compatibilized by styrene/ethylene/butylene/styrene block copolymers grafted with maleic anhydride (SEBS-g-MAH) and organomontmorillonite (OMMT). The scanning electron microscope results indicated that the size of the PS phase decreased with increasing the content of SEBS-g-MAH. By introducing OMMT into LDPE/PS/SEBS-g-MAH composites, the compatibility of composites was further improved. The rheological analysis and Cole–Cole plot analysis indicated that the addition of SEBS-g-MAH and OMMT increased the interaction between the two phases. The tensile strength, elongation at break, and impact strength of the LDPE/PS/SEBS-g-MAH (70/30/7, wt%) composite increased by 64%, 255%, and 380%, respectively, compared with the LDPE/PS (70/30, wt%) composite. A small amount of OMMT could synergistically compatibilize the LDPE/PS composite with SEBS-g-MAH. After adding 0.3% OMMT into the LDPE/PS/SEBS-g-MAH system, the tensile strength, elongation at break, and impact strength of the composite were further increased to 18.57 MPa, 71.87%, and 33.28 kJ/m2, respectively.
Carbon microspheres (CMs) with a diameter of 5-10 μm have been synthesized by hydrothermal carbonization of starch and L-arginine. The surface property and structure of CMs were examined by FT-IR ...spectra, N2 adsorption-desorption isotherms and SEM images. These characterizations indicated that the L-arginine does not connect into the CMs but it promotes the starch hydrolysis and polymerization-condensation reaction of intermediate, which accelerates the formation of CMs and improves the yield in shorter time. The surface property of CMs determines adsorption capacity for acetic acid. By contrast, the porosity resulted from the carbonization at 500 and#176;C dominates the adsorption capacity for acetic acid.
The γ˝ phase (Mg4GdZn) precipitate in Mg-Gd-Zn alloy was calculated via first-principle density functional theory within the generalized gradient approximation. Through structure optimization of full ...relaxation, the lattice parameters were theoretically obtained, and the calculated Mg4GdZn is the most energetically stable in view of the formation energy. Independent elastic constants were also calculated, illustrating the calculated Mg4GdZn is mechanically stable. The shear modulus, polycrystalline bulk modulus, Poisson ratio, and Young’s modulus of Mg4GdZn were calculated via the Voigt-Reuss-Hill approximation. Elastic anisotropy and ductility were analyzed in details. Seen from their charge density distribution and electronic density of states, both metallic bond and covalent bond were found in Mg4GdZn.
NiMo catalysts were prepared using Waugh-type NiMo heteropolycompounds as active phase precursors and evaluated in hydrodesulfurization (HDS) of dibenzothiophene (DBT). These catalysts were compared ...with corresponding reference catalysts prepared from the conventional precursors (ammonium heptamolybdate and nickel nitrate). Prepared catalysts were characterized by N
2
physisorption, XRD, FT-IR, H
2
-TPR, DRIFT of CO adsorption and HRTEM techniques. It was found that NiMo catalysts prepared from Waugh-type NiMo HPCs showed higher performance in HDS of DBT than their counterparts. Possible reasons of this result were discussed.
Graphical Abstract
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