Sha Chen

Selective oxidation of glycerol to lactic acid under acidic conditions using AuPd/TiO2 catalyst

The selective oxidation of glycerol was investigated using AuPd/TiO2 as the catalyst in the presence of AlCl3, and lactic acid was obtained as the predominant product. It was demonstrated that AuPd/TiO2 and AlCl3 played synergistic roles in the production of lactic acid. The possible reaction pathway was proposed, in which glycerol was first oxidized to glyceraldehyde and dihydroxyacetone, catalysed by AuPd/TiO2, followed by the formation of lactic acid, catalyzed by AlCl3.

Cyclization of o-phenylenediamines by CO2 in the presence of H2 for the synthesis of benzimidazoles

The cyclization of o-phenylenediamines by CO2 in the presence of H2 was presented to directly synthesize benzimidazoles, and a series of benzimidazoles were obtained in excellent yields using RuCl2(dppe)2 as the catalyst.

Porous Fe3O4 nanoparticles: Synthesis and application in catalyzing epoxidation of styrene

A facile route was employed to synthesize porous magnetite via reaction of FeCl(3)·6H(2)O with N(2)H(4)·H(2)O in ethylene glycol without any structure-directing agent. The resultant Fe(3)O(4) particles were characterized by transmission electron microscopy, N(2) adsorption, X-ray photoelectron spectroscopy, and thermal gravimetric analysis. It was demonstrated that the particle size varied in the range of 40-220 nm, and the pore size of particles was centered around 2 nm. The gases produced in the formation process of the particles played key role in the formation of the porous structure. The obtained porous magnetite was used as support to immobilize Au nanoparticles with size less than 2 nm with the assistance of L-cysteine. The as-prepared Fe(3)O(4) particles can effectively catalyze epoxidation of styrene, and the immobilization of Au nanoparticles on the Fe(3)O(4) support significantly improved the activity of the catalyst.

Controllable synthesis of supported Cu–M (M =Pt, Pd, Ru, Rh) bimetal nanocatalysts and their catalytic performances

Based on the galvanic replacement reaction between Cu nanoparticles and noble metal ions, a simple and efficient strategy was developed for the preparation of supported Cu–M (M = Pt, Pd, Ru, Rh) bimetallic nanoparticles under intense ultrasonication irradiation at ambient environment. A series of Cu–M/TiO2 bimetal catalysts with controllable composition, metal particle size less than 2 nm and narrow size distribution were obtained, and characterized by transmission electron microscopy (TEM), high resolution transmission electron microscope (HRTEM) with scanning TEM (STEM) mode, energy-dispersive X-ray spectrometers (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and ICP-AES analysis. It was demonstrated that most of the metal particles were present in the form of bimetallic state. The mechanism of this strategy was discussed. The resultant Cu–Pd/TiO2 was used to reduce nitrate at room temperature, and it exhibited extremely high activity.

Ionic liquid-stabilized graphene and its use in immobilizing a metal nanocatalyst

A new ionic liquid (IL), 1-butyl-3-methylimidazolium cholate, was first synthesized through an ion exchange reaction of 1-butyl-3-methylimidazolium chloride with sodium cholate. Stable aqueous dispersions of graphene were achieved by exfoliating graphite in the presence of the IL under ultrasonication. Both transmission electron microscopy and Raman measurements showed that the IL-stabilized graphene (IL–G) sheets existed with only a few (<5) layers. Furthermore, the IL–G was used to immobilize noble metal nanoparticles (Pt, Pd, Ru, Rh, etc), and a series of graphene–metal (G–M) composites with metal size ≤2 nm and very narrow size distributions were obtained. The resulting G–M exhibited superior catalytic performance with respect to hydrogenation of arenes. In particular, the as-prepared G–Ru with Ru content of 5% was very active for the hydrogenation of benzene to hexane with a turnover frequency as high as 6000 h−1. The catalysts could be reused without detectable loss of activity, a result of their stable structure.

Diatomite-supported Pd–M (M = Cu, Co, Ni) bimetal nanocatalysts for selective hydrogenation of long-chain aliphatic esters

Diatomite supported Pd-M (M=Cu, Co, Ni) bimetal nanocatalysts with various metal compositions were prepared and characterized by means of X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was demonstrated that the metal nanoparticles were uniformly distributed on the support, and their size was centered around 8 nm with a relatively narrow size distribution. The catalysts were used to catalyze hydrogenation of long-chain aliphatic esters, including methyl palmitate, methyl stearate, and methyl laurate. It was indicated that the all diatomite-supported Pd-based bimetal catalysts were active to the selective hydrogenation of long-chain esters to corresponding alcohols at 270°C, originated from the synergistic effect between the metal particles and the diatomite support. For the selective hydrogenation of methyl palmitate, Pd-Cu/diatomite with metal loading of 1% and Pd/Cu=3 displayed the highest performance, giving a 1-hexadecanol yield of 82.9% at the substrate conversion of 98.8%.

Ti3+ self-doped TiOx@anatase core–shell structure with enhanced visible light photocatalytic activity

Ti3+ self-doped TiOx@anatase core–shell structures were prepared via hydrolysis of Ti2(SO4)3 around TiO particles, followed by post-calcination at temperatures from 723 to 823 K. The as-prepared TiOx@anatase was examined by means of transmission electronic microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. It was demonstrated that the samples displayed core–shell structures with the shell in the anatase form and the core in the anatase and rutile phases, and a large number of Ti3+ ions were present. Electron paramagnetic resonance analysis indicated that the Ti3+ ions were located throughout the whole sample, including the shell, the core and the interface between the core and the shell. The as-prepared TiOx@anatase core–shell catalysts can absorb visible light and showed good activity for catalyzing the degradation of Rhodamine B under visible light irradiation. In particular, the TiOx@anatase obtained at 773 K showed the best performance, due to the high concentration of well-dispersed Ti3+ ions in the sample.

One-pot solvothermal method to synthesize platinum/W18O49 ultrafine nanowires and their catalytic performance

A simple solvothermal method was developed to prepare platinum/W18O49 ultrafine nanowires (<5 nm in diameter) through hydrolysis of WCl6 in ethanol-water solution in the presence of poly(N-vinyl-2-pyrrolidone) capping with Pt nanoparticles, and a series of Pt/W18O49 nanocomposites were obtained. These Pt/W18O49 composites were characterized by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectra, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. It was demonstrated that PVP not only directed the formation of W18O49 nanowires, but also transferred the metal particles onto the oxide support without any size change. Due to the relatively strong interaction between Pt nanoparticles and the W18O49 nanowires, the as-prepared Pt/W18O49 composites exhibited blue shift in UV emission compared to the W18O49 nanowires, and displayed high activity and excellent stability for hydrogenation of p-chloronitrobenzene to p-chloroaniline with a selectivity of 99.7%.

Pt/titania/reduced graphite oxide nanocomposite: An efficient catalyst for nitrobenzene hydrogenation

In this work, a ternary composite, Pt/TiO(2)/RGO (reduced graphite oxide), was prepared via immobilizing Pt particles onto the TiO(2)/RGO composite that was obtained via redox reaction of TiCl(3) and GO. The composite was characterized by different techniques including X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The TiO(2) particles with size less than 10 nm were uniformly distributed throughout the RGO, and almost each Pt particle with size around 3 nm adhered to TiO(2) particles, resulting in high dispersion of all Pt particles on the support. The Pt particles were in the electron-deficient state due to the strong interactions with the TiO(2) particles and the RGO support. The catalytic performance of the composite for nitrobenzene hydrogenation was investigated under solvent-free condition. It was indicated that the Pt/TiO(2)/RGO catalyst exhibited high activity with a turnover frequency (e.g., 59,000 h(-1)) as well as superior selectivity to aniline (e.g., >99%). Moreover, the catalyst can be reused for six times without any activity loss, which resulted from the stable structure of the catalyst.

Pd nanoparticles immobilized on graphite oxide modified with a base: Highly efficient catalysts for selective hydrogenation of citral

In this work, the Pd-based catalysts were designed via immobilizing Pd nanoparticles on graphite oxide (GO) modified with organic base, 1,1,3,3-tetramethylguanidine (TMG), which was used for the selective hydrogenation of citral. These catalysts were characterized by various techniques including IR, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was demonstrated that the Pd particles with size less than 5 nm were uniformly distributed throughout the support, and they were in the electron-deficient state due to the strong interactions with the modified support. The resultant Pd-TMG/GO catalyst displayed high efficiency for the selective hydrogenation of citral with a turnover frequency of 7100 h−1 as well as superior selectivity to citronellal of 89.6%. Moreover, the catalyst can be reused for five times without obvious activity loss, which may result from its stable structure.