Junhua Wang

Zhejiang University, Hang-hsien, Zhejiang Sheng, China

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Publications (10)13.55 Total impact

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    ABSTRACT: Reduced graphene oxide (RGO)-supported platinum (Pt) catalyst was prepared by simple ethylene glycol (EG) reduction and used for hydrogenation of nitroarenes. Characterizations showed that EG as a reductant exhibited more advantages than the widely used hydrazine hydrate to fabricate monodispersed, small sized Pt nanoparticles on the surface of RGO. The yield of aniline over the Pt/RGO-EG catalyst reached 70.2 mol-AN/(mol-Pt min) at 0 oC, which is 12.5 and 19.5 times higher than that of multi-walled carbon nanotube- and active carbon-supported Pt catalysts, respectively. When the reaction temperature was increased to 20 oC, the catalytic activity of Pt/RGO-EG jumped to 1138.3 mol-AN/(mol-Pt min), and it was also extremely active for the hydrogenation of a series of nitroarenes. The unique catalytic activity of Pt/RGO-EG is not only related to the well dispersed Pt clusters on the RGO sheets but also the well dispersion of Pt/RGO-EG in the reaction mixture.
    Carbon. 02/2012; 50(2):586–596.
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    ABSTRACT: Homogenously dispersed copper on layered solid base (Cu0.4/Mg5.6Al2O8.6-CP, with 80.1% dispersion of copper) was synthesized via thermal decomposition of the as-synthesized Cu0.4Mg5.6Al2(OH)16CO3 layered double hydroxides. This bi-functional highly dispersed Cu-solid base catalyst is extremely effective for hydrogenolysis of aqueous glycerol. The detected conversion of glycerol reached 80.0% with a 98.2% selectivity of 1,2-propanediol at 180°C, 3.0MPa H2 and 20h. But copper dispersed poorly in those catalysts prepared via impregnation and ion-exchange, and their activities were lower. These precursors and catalysts were characterized by N2-adsorption, X-ray diffraction, scanning electronic microscope, transmission electronic microscope, thermo-gravimetry, temperature-programmed reduction with H2, in-situ XRD, dissociative N2O adsorption and CO2 temperature-programmed desorption. It was confirmed that the as-synthesized Cu0.4Mg5.6Al2(OH)16CO3 showed a well crystallized layer-structure of hydrotalcite and copper dispersed homogenously on the layer-structure of hydrotalcite after thermal decomposition and H2 reduction.
    Applied Catalysis B-environmental - APPL CATAL B-ENVIRON. 01/2011; 101(3):431-440.
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    ABSTRACT: A series of carbon supported bimetallic Pt―Cu catalysts were prepared and used for glycerol oxidation with oxygen in a base-free aqueous solution. It was found that bimetallic Pt―Cu/C was more active than monometallic Pt/C towards selective oxidation of glycerol to glyceric acid. The selectivity of free glyceric acid reached 70.8% at an 86.2% conversion of glycerol over 5Pt―Cu/C. Highly dispersed bimetallic Pt―Cu nanoparticles with small particle size in dominant alloyed phase of PtCu3 were confirmed by XRD and TEM in the bimetallic Pt―Cu/C catalyst, which is proposed to contribute to the improved performance.
    Catalysis Communications - CATAL COMMUN. 01/2011; 12(12):1059-1062.
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    ABSTRACT: Hydrogenolysis of biodiesel derived glycerol to 1,2-propanediol (1,2-PDO) has attracted much attention in recent years. In this work, glycerol hydrogenolysis to 1,2-PDO was performed over CuO/MgO catalysts prepared by impregnation and coprecipitation at 180 degrees C and 3.0 MPa H(2). It was found that the Cu(15)/MgO catalyst prepared by coprecipitation had the best activity. The conversion of glycerol and the selectivity of 1,2-PDO over Cu(15)/MgO reached 72.0% and 97.6%, respectively. And the conversion of glycerol was further increased to 82.0% when small amount of NaOH was added in the reaction mixture. Those highly active catalysts were characterized by X-ray diffraction, transmission electron microscopy, N(2)-adsorption and temperature-programmed reduction with H(2). Characterization results revealed that the activity of the prepared catalysts depended strongly on the particle sizes of both Cu and MgO. Catalysts that have smaller sized Cu and MgO particles are more active for glycerol hydrogenolysis.
    Bioresource Technology 09/2010; 101(18):7099-103. · 4.75 Impact Factor
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    ABSTRACT: Nanosized silica gel supported Ni catalysts that have average Ni particle size of 3.7, 11.4, and 11.8 nm were prepared by facile impregnation of different Ni precursors and used for hydrogenation of nitrobenzene (NB). These catalysts were characterized by N2 adsorption, X-ray diffraction, and transmission electron microscopy. It was found that Ni dispersed highly on the surface of silica gel in the catalyst prepared via Ni(en)3(NO3)2, and the detected average Ni particle size was 3.7 nm. On the 3.7 nm sized Ni catalyst, the selectivity of aniline (AN) reached 99% with a 100% conversion of NB in 5.5 h at 90 °C, 1.0 MPa, and NB:Ni = 305 (mole ratio). But, the activities of 11.8 nm sized Ni catalysts and commercial Raney Ni catalyst are quite lower. The reaction network and mechanism of NB hydrogenation on 3.7 nm sized Ni catalyst were discussed on the basis of products distributions at different temperatures and pressures. The calculated activation energy of NB hydrogenation on Ni-5/SiO2-EN catalyst is 54.5 kJ/mol in 70−90 °C.
    Industrial & Engineering Chemistry Research. 04/2010; 49(10).
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    ABSTRACT: Combined Al2O3-HZSM-5 solid acids were prepared and used for methanol dehydration to dimethyl ether (DME) in a fixed-bed reactor. The physicochemical properties of the combined solid acids were characterized by X-ray diffraction, field emission scanning electron microscopy, N2 adsorption, and NH3 temperature-programmed desorption. Al2O3 was highly dispersed in Al2O3-HZSM-5 after impregnation (Al2O3-HZSM-5-IM), while a layered Al2O3-covered HZSM-5 structure solid acid was synthesized via chemical precipitation (Al2O3-HZSM-5-CP). Both the combined Al2O3-HZSM-5 solid acids prepared by impregnation and chemical precipitation have a higher surface area and more meso- and macropores. The combined Al2O3-HZSM-5 solid acids exhibit higher methanol dehydration activity than pure Al2O3 and it possesses higher stability than pure HZSM-5 at a lower temperature (235 (C) and a higher LHSV (30 h−1). The stable DME productivities for Al2O3-HZSM-5-IM and Al2O3-HZSM-5-CP at 235 (C reached 12.7 and 13.5 g/(g·h), respectively.
    Chinese Journal of Catalysis - CHIN J CATAL. 01/2010; 31(8):987-992.
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    ABSTRACT: Two-dimensional gel electrophoresis (2-DE) is a powerful method to study protein expression and function in living organisms and diseases. This technique, however, has not been applied to avian bursa of Fabricius (BF), a central immune organ. Here, optimized 2-DE sample preparation methodologies were constructed for the chicken BF tissue. Using the optimized protocol, we performed further 2-DE analysis on a soluble protein extract from the BF of chickens infected with virulent avibirnavirus. To demonstrate the quality of the extracted proteins, several differentially expressed protein spots selected were cut from 2-DE gels and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). An extraction buffer containing 7 M urea, 2 M thiourea, 2% (w/v) 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS), 50 mM dithiothreitol (DTT), 0.2% Bio-Lyte 3/10, 1 mM phenylmethylsulfonyl fluoride (PMSF), 20 U/ml Deoxyribonuclease I (DNase I), and 0.25 mg/ml Ribonuclease A (RNase A), combined with sonication and vortex, yielded the best 2-DE data. Relative to non-frozen immobilized pH gradient (IPG) strips, frozen IPG strips did not result in significant changes in the 2-DE patterns after isoelectric focusing (IEF). When the optimized protocol was used to analyze the spleen and thymus, as well as avibirnavirus-infected bursa, high quality 2-DE protein expression profiles were obtained. 2-DE maps of BF of chickens infected with virulent avibirnavirus were visibly different and many differentially expressed proteins were found. These results showed that method C, in concert extraction buffer IV, was the most favorable for preparing samples for IEF and subsequent protein separation and yielded the best quality 2-DE patterns. The optimized protocol is a useful sample preparation method for comparative proteomics analysis of chicken BF tissues.
    Proteome Science 10/2009; 7:38. · 2.42 Impact Factor
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    ABSTRACT: The highly pathogenic H5N1 avian influenza virus emerged from China in 1996 and has spread across Eurasia and Africa, with a continuous stream of new cases of human infection appearing since the first large-scale outbreak among migratory birds at Qinghai Lake. The role of wild birds, which are the natural reservoirs for the virus, in the epidemiology of the H5N1 virus has raised great public health concern, but their role in the spread of the virus within the natural ecosystem of free-ranging terrestrial wild mammals remains unclear. In this study, we investigated H5N1 virus infection in wild pikas in an attempt to trace the circulation of the virus. Seroepidemiological surveys confirmed a natural H5N1 virus infection of wild pikas in their native environment. The hemagglutination gene of the H5N1 virus isolated from pikas reveals two distinct evolutionary clades, a mixed/Vietnam H5N1 virus sublineage (MV-like pika virus) and a wild bird Qinghai (QH)-like H5N1 virus sublineage (QH-like pika virus). The amino acid residue (glutamic acid) at position 627 encoded by the PB2 gene of the MV-like pika virus was different from that of the QH-like pika virus; the residue of the MV-like pika virus was the same as that of the goose H5N1 virus (A/GS/Guangdong [GD]/1/96). Further, we discovered that in contrast to the MV-like pika virus, which is nonpathogenic to mice, the QH-like pika virus is highly pathogenic. To mimic the virus infection of pikas, we intranasally inoculated rabbits, a species closely related to pikas, with the H5N1 virus of pika origin. Our findings first demonstrate that wild pikas are mammalian hosts exposed to H5N1 subtype avian influenza viruses in the natural ecosystem and also imply a potential transmission of highly pathogenic avian influenza virus from wild mammals into domestic mammalian hosts and humans.
    Journal of Virology 07/2009; 83(17):8957-64. · 5.08 Impact Factor
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    ABSTRACT: A series of Pt/C catalysts with different Pt particle size ranged from 1.2 to 26.5nm were prepared and used for the oxidation of glycerol in a base-free aqueous solution. The morphologies and the dispersion of Pt were characterized by CO adsorption, TEM and XRD. It was found that the dispersion of Pt depends strongly on the surface properties of the support, the amount of reducing agent and preparation temperature. Though bigger sized Pt particles (>10nm) were less active, smaller sized ones (
    Catalysis Communications - CATAL COMMUN. 01/2009; 10(12):1586-1590.
  • Chinese Journal of Catalysis 32(s 11–12):1831–1837. · 1.30 Impact Factor