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1.
A novel gel-network-coprecipitation process has been developed to prepare ultrafine Cu/ZnO/Al2O3 catalysts for methanol synthesis from CO2 hydrogenation. It is demonstrated that the gel-network-coprecipitation method can allow the preparation of the ultrafine Cu/ZnO/Al2O3 catalysts by homogeneous coprecipitation of the metal nitrate salts in the gel network formed by gelatin solution, which makes the metallic copper in the reduced catalyst exist in much smaller crystallite size and exhibit a much higher metallic copper-specific surface area. The effect of the gel concentration of gelatin on the structure, morphology and catalytic properties of the Cu/ZnO/Al2O3 catalysts for methanol synthesis from hydrogenation of carbon dioxide was investigated. The Cu/ZnO/Al2O3 catalysts prepared by the gel-network-coprecipitation method exhibit a high catalytic activity and selectivity in CO2 hydrogenation to methanol. 相似文献
2.
Garry Glaspell Hassan M. A. Hassan Ahmed Elzatahry Victor Abdalsayed M. Samy El-Shall 《Topics in Catalysis》2008,47(1-2):22-31
Active gold and palladium nanoparticles supported on a variety of oxides (CeO2, ZrO2, Al2O3, SiO2, MgO and ZnO) were synthesized using laser vaporization and microwave irradiation methods. The catalytic activities for CO
oxidation on the nanoparticle catalysts were evaluated and compared among different oxide supports. The effect of shape on
the catalytic activity is demonstrated by comparing the activities of the Au and Pd catalysts deposited on MgO nanocubes and
ZnO nanobelts. The Au/CeO2 nanoparticles deposited on MgO nanocubes exhibit high catalytic activity and stability. The enhanced catalytic activity is
attributed to the presence of a significant concentration of the corner and edge sites in MgO nanocubes. The Au- and Pd-doped
Mn2O3 nanoparticles show promising results for the low temperature CO oxidation. Several approaches for incorporating the Au and
Pd nanocatalysts within mesoporous oxide supports are presented and discussed. 相似文献
3.
Sung Min Kim Mi Eun Lee Jae Wook Choi Dong Jin Suh Young-Woong Suh 《Catalysis communications》2011,12(14):1328-1332
For hydrogenolysis of butyl butyrate (BB), a series of Cu/ZnO/Al2O3 catalysts with different metal compositions were prepared, and characterized by N2O chemisorption for measuring Cu surface area and by chromatographic experiment for determining the heat of BB adsorption. As a result, the presence of ZnO in Cu-based catalysts was found to enhance the catalytic activity of Cu due to dual function of ZnO. The Cu surface area was linearly correlated with the butanol productivity, demonstrating that ZnO exerts the structural function in Cu/ZnO/Al2O3 catalysts. Additionally, the role of ZnO as a chemical contributor was revealed such that its presence leads to lower activation energy of the surface reaction, thus resulting in higher Cu catalytic activity obtained at a low temperature such as 200 °C. Consequently, optimizing the Cu/Zn ratio in Cu/ZnO/Al2O3 catalyst is required to tune its structural and chemical characteristics of Cu metals, and thus to obtain a higher activity on the hydrogenolysis reaction. 相似文献
4.
Xinchang Wang Minggang Zhao Fang Liu Jianfeng Jia Xinjian Li Liangliang Cao 《Ceramics International》2013
Pure and Ni-doped ZnO nanofibers were synthesized using the electrospinning method. The morphology, crystal structure and optical properties of the nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy, respectively. It is found that Ni doping does not change the morphology and crystal structures of the nanofibers, and the ultraviolet emissions of ZnO nanofibers present red shift with increasing Ni doping concentration. C2H2 sensing properties of the sensors based on the nanofibers were investigated. The results show that the C2H2 sensing properties of ZnO nanofibers are effectively improved by Ni doping, and 5 at% Ni-doped ZnO nanofibers exhibit a maximum sensitivity to C2H2 gas. 相似文献
5.
Xin-Rong Zhang Lu-Cum Wang Cheng-Zhang Yao Yong Cao Wei-Lin Dai He-Yong He Kang-Nian Fan 《Catalysis Letters》2005,102(3-4):183-190
The impact of preparation methods on the structure and catalytic behavior of Cu/ZnO/Al2O3 catalysts for H2 production from steam reforming of methanol (SRM) has been reported. The results show that the nanostructured Cu/ZnO/Al2O3 catalyst obtained by a novel gel-coprecipitation of oxalate precursors has a high specific surface area and high component dispersion, exhibiting much higher activity in the SRM reaction as compared to the catalysts prepared by conventional coprecipitation techniques. It is suggested that the superior catalytic performance of the oxalate gel-coprecipitation-derived Cu/ZnO/Al2O3 catalyst could be attributed to the generation of “catalytically active” copper material with a much higher metallic copper specific surface as well as a stronger Cu–Zn interaction due to an easier incorporation of zinc species into CuC2O4 · x H2O precursors as a consequence of isomorphous substitution between copper and zinc in the oxalate gel-precursors. 相似文献
6.
Ali İmran Vaizoğullar 《Chemical Engineering Communications》2017,204(6):689-697
In this study, TiO2, ZnO, TiO2/ZnO (Ti/Zn), and TiO2/ZnO/Sep (Ti/Zn/Sep) catalysts have been synthesized using sol–gel and chemical precipitation method. Their photocatalytic performances have been compared using Flumequine (FLQ) antibiotic. X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), N2-adsorption, and the determination of a zero point charge has been used to characterize the synthesized catalysts. The degradation studies showed that the catalytic efficiency of Ti/Zn/Sep is higher than that for other catalysts. The operational parameters such as pH, initial FLQ concentration, and catalyst dosage were evaluated. UV–vis and high-resolution mass spectroscopy (HRMS) analyses were used to determine the degradation efficiency and products. ZnO played a major role in the FLQ degradation process, and sepiolite contributed to adsorption of FLQ on the catalyst surface enormously. The catalysts exhibited 11%, 23%, 63%, and 85% degradation efficiency for ZnO, TiO2, Ti/Zn, and Ti/Zn/Sep in the decomposition of FLQ, respectively. 相似文献
7.
ZnO nano/microstructures have been formed by thermal evaporation method using ZnO powders mixed with carbon group elements
(C, Si, Ge, Sn, or Pb) as the reducing agent. For cases of mixed precursors of ZnO/C, ZnO/Si, and ZnO/Ge, the pure ZnO nano/microstructures
are realized, while for ZnO/Sn (ZnO/Pb) systems, the phase of Pb2O3 (Zn2SnO4) generally are represented in the ZnO products. The appearance of Pb2O3 (Zn2SnO4) is attributed to the lower melting point and higher vapor pressure of Sn (Pb) in the heating and evaporation processes.
The morphologies and sizes of the products are controlled by adjusting the growth regions and/or introducing gaseous argon.
Room temperature (RT) photoluminescence spectra indicate that the intensity (peak position) of the ultraviolet emission is
increased (redshift) due to the existence of Zn2SnO4 phase in the ZnO products. The Pb2O3 (Zn2SnO4) phase in ZnO nano/microstructures plays a important role in enhancing the saturation magnetizations of RT ferromagnetism
with respect to the case of pure ZnO products fabricated by the precursor of mixed ZnO and graphite. 相似文献
8.
CeO2/ZnO nanostructured microspheres with an average diameter of about 3.8 μm were synthesized by a solid-stabilized emulsion route. The CeO2/ZnO nanostructured microspheres were characterized with SEM, XRD, CO2-TPD, BET measurement and size analysis. Based on the oxidative coupling reaction of methane with carbon dioxide as an oxidant, the catalytic performance of the CeO2/ZnO nanostructured microspheres was evaluated and compared with that of the CeO2/ZnO nanoparticles. The results showed that the surfaces of the CeO2/ZnO nanostructured microspheres consisted of petal-like structures with a petal thickness of about 90 nm and a petal depth of 0.4 μm to 0.9 μm. Using CeO2/ZnO nanostructured microspheres as catalysts for the oxidative coupling of methane with carbon dioxide, the conversion of methane corresponded with that using the CeO2/ZnO nanoparticles, while the CeO2/ZnO nanostructured microspheres had much longer operating life. 相似文献
9.
E.M. Seftel E. Popovici M. Mertens E.A. Stefaniak R. Van Grieken P. Cool E.F. Vansant 《Applied catalysis. B, Environmental》2008,84(3-4):699-705
Sn4+-containing LDH was prepared using the co-precipitation method at constant pH, and characterized using X-ray diffraction, UV–vis diffuse reflectance spectroscopy and TG/DTG methods. The obtained product was further exposed to different thermal treatments in order to obtain nano-sized coupled ZnO/SnO2 systems with enhanced photocatalytic performances than the ones obtained by mixing the two semiconductor oxides. The formation of a well-defined ZnO/SnO2 system and the crystallite size, fully investigated using XRD, micro-Raman scattering and UV–vis DR techniques, were found to be influenced by the nature of the precursors and the calcination temperature. The photocatalytic activity of the ZnO/SnO2 systems, evaluated for the photodegradation of methyl orange (MO) dye, was studied as a function of the initial pH, catalyst loading and the calcination temperature. The metal dispersion supplied by layered structures proved to be an advantage when preparing coupled ZnO/SnO2 systems, the photocatalytic activity being 2.3 times higher comparing with the physical mixtures performances. The maximum photocatalytic activity of the coupled ZnO/SnO2 system having a layered precursor was observed when using neutral pH, at a catalyst loading of 1 g/L calcined at 600 °C for 4 h. 相似文献
10.
Katsutoshi Nagaoka Kulathuiyer Seshan Kazuhiro Takanabe Ken-ichi Aika 《Catalysis Letters》2005,99(1-2):97-100
CH4/CO2 reforming over Pt/ZrO2, Pt/CeO2 and Pt/ZrO2 with CeO2 was investigated at 2 MPa. Pt/ZrO2, which shows stable activity under 0.1 MPa, and Pt/CeO2 showed gradual deactivation with time at the high pressure. The deactivation was suppressed drastically on Pt/ZrO2 with CeO2 prepared by different impregnation order (co-impregnation of Pt and CeO2 on ZrO2, and consecutive impregnation of Pt and CeO2 on ZrO2). The amount of coke deposition was found insignificant and similar among all the catalysts (including Pt/ZrO2 and Pt/CeO2). Catalytic activity after the reaction for 24 h was in agreement with Pt particle size after the reaction for same period, indicating that the difference of the catalytic stability is mainly dependent on the extent of Pt aggregation through catalyst preparation, H2 reduction, and the CH4/CO2 reforming. Pt aggregation and the amount of coke deposition were least pronounced on (Pt–Ce)/ZrO2 prepared by impregnation of CeO2 on Pt/ZrO2 and the catalyst showed highest stability. 相似文献
11.
Po-Kai Chiu Chao-Te Lee Donyau Chiang Wen-Hao Cho Chien-Nan Hsiao Yi-Yan Chen Bo-Ming Huang Jer-Ren Yang 《Nanoscale research letters》2014,9(1):35
Conductive and transparent multilayer thin films consisting of three alternating layers (TiO2/Ag/SiO2, TAS) have been fabricated for applications as transparent conducting oxides. Metal oxide and metal layers were prepared by electron-beam evaporation with ion-assisted deposition, and the optical and electrical properties of the resulting films as well as their energy bounding characteristics and microstructures were carefully investigated. The optical properties of the obtained TAS material were compared with those of well-known transparent metal oxide glasses such as ZnO/Ag/ZnO, TiO2/Ag/TiO2, ZnO/Cu/ZnO, and ZnO/Al/ZnO. The weathering resistance of the TAS film was improved by using a protective SiO2 film as the uppermost layer. The transmittance spectra and sheet resistance of the material were carefully measured and analyzed as a function of the layer thickness. By properly adjusting the thickness of the metal and dielectric films, a low sheet resistance of 6.5 ohm/sq and a high average transmittance of over 89% in the 400 to 700 nm wavelength regions were achieved. We found that the Ag layer played a significant role in determining the optical and electrical properties of this film. 相似文献
12.
Ruichao Zhang Hengbo Yin Dongzhi Zhang Lin Qi Huihong Lu Yutang Shen Tingshun Jiang 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2008,140(1-3):488-496
Cu/ZnO/TiO2 catalysts were prepared via the coprecipitation method. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectrometry, temperature programmed reduction, and N2 adsorption. The catalytic activity of Cu/ZnO/TiO2 catalyst in gas phase hydrogenation of maleic anhydride in the presence of n-butanol was studied at 235–280 °C and 1 MPa. The conversion of maleic anhydride was more than 95.7% and the selectivity of tetrahydrofuran was up to 92.7%. At the same time, n-butanol was converted to butyraldehyde and butyl butyrate via reactions, namely, dehydrogenation, disproportionation, and esterification. There were two kinds of CuO species present in the calcined Cu/ZnO/TiO2 catalysts. At a lower copper content, the CuO species strongly interacted with ZnO and TiO2; at a higher copper content, both the surface-anchored and bulk CuO species were present. The metallic copper (CuO) produced by the reduction of the surface-anchored CuO species favored the deep hydrogenation of maleic anhydride to tetrahydrofuran. The deep hydrogenation activity of Cu/ZnO/TiO2 catalyst increased with the decrease of crystallite sizes of CuO and the increase of microstrain values. Compensations of reaction heat and H2 in the coupling reaction of maleic anhydride hydrogenation and n-butanol dehydrogenation were distinct. 相似文献
13.
A series of ZnO promoted Co/CeO2 catalysts were synthesized and characterized using XRD, TEM, H2-TPR, CO chemisorption, O2-TPO, IR-Py, and CO2-TPD. The effects of ZnO on the catalytic performances of Co/CeO2 were studied in ethanol steam reforming. It was found that the addition of ZnO facilitated the oxidation of Co0 via enhanced oxygen mobility of the CeO2 support which decreased the activity of Co/CeO2 in C–C bond cleavage of ethanol. 3 wt% ZnO promoted Co/CeO2 exhibited minimum CO and CH4 selectivity and maximum CO2 selectivity. This resulted from the combined effects of the following factors with increasing ZnO loading: (1) enhanced oxygen mobility of CeO2 facilitated the oxidation of CH x and CO to form CO2; (2) increased ZnO coverage on CeO2 surface reduced the interaction between CH x /CO and Co/CeO2; and (3) suppressed CO adsorption on Co0 reduced CO oxidation rate to form CO2. In addition, the addition of ZnO also modified the surface acidity and basicity of CeO2, which consequently affected the C2–C4 product distributions. 相似文献
14.
Xiang Li Yanling Zhang Anjie Wang Yao Wang Yongkang Hu 《Catalysis communications》2010,11(14):1129-1132
TiO2- and CeO2-promoted bulk Ni2P catalysts were prepared by impregnation and in-situ H2 temperature-programmed reduction method. The prepared catalysts were characterized by XRD and XPS. The hydrogenation activities of the catalysts were studied using 1.5 wt.% 1-heptene in toluene and 1.0 wt.% phenylacetylene in ethanol as the model feeds. The results indicate that bulk Ni2P possesses low hydrogenation activity but is tunable by simply controlling the content of the additives (TiO2 or CeO2), suggesting that TiO2 and CeO2 are effective promoters to enhance the hydrogenation activity of Ni2P. 相似文献
15.
In the oxidative coupling of methane by carbon dioxide, La2O3/ZnO catalysts were found to have high C2 selectivity and good stability. The coupling selectivity on La2O3/ZnO is about 90%, which is much higher than that on pure La2O3 or ZnO. The consumption ratio of carbon dioxide to methane is approximately one. X-ray diffraction analysis reveals that the structural forms of the oxides are unchanged during the reaction. The reaction mechanism for C2 formation is discussed. 相似文献
16.
Sang-Woo Park Oh-Shim Joo Kwang-Deog Jung Hyo Kim Sung-Hwan Han 《Korean Journal of Chemical Engineering》2000,17(6):719-722
The stability and the activity of Fe2O3/Cr2O3 and ZnO/Cr2O3 catalysts were examined for a reverse-watergas-shift reaction (RWReaction). The initial activities of those catalysts were
quite high so that the conversion reached close to equilibrium. The activity of Fe2O3/Cr2O3 catalyst decreased from 33.5 to 29.8% during the RWReaction for 75 h at 873 K with GHSV (ml/gcat · h) of 100,000. Moreover,
the coke formation on the Fe2O3/Cr2O3 catalyst caused clogging in the RWReactor of the CAMERE process. On the other hand, the ZnO/Cr2O3 catalyst showed no coke formation and no deactivation for the RWReaction at 873 K with GHSV (ml/gcat · h) of 150,000. The
ZnO/Cr2O3 was a good catalyst for the RWReaction of the CAMERE process. 相似文献
17.
Optical and microstructural properties of ZnO/TiO2 nanolaminates prepared by atomic layer deposition
Yu-Zhu Gu Hong-Liang Lu Yang Geng Zhi-Yuan Ye Yuan Zhang Qing-Qing Sun Shi-Jin Ding David Wei Zhang 《Nanoscale research letters》2013,8(1):107
ZnO/TiO2 nanolaminates were grown on Si (100) and quartz substrates by atomic layer deposition at 200°C using diethylzinc, titanium isopropoxide, and deionized water as precursors. All prepared multilayers are nominally 50 nm thick with a varying number of alternating TiO2 and ZnO layers. Sample thickness and ellipsometric spectra were measured using a spectroscopic ellipsometer, and the parameters determined by computer simulation matched with the experimental results well. The effect of nanolaminate structure on the optical transmittance is investigated using an ultraviolet–visible-near-infrared spectrometer. The data from X-ray diffraction spectra suggest that layer growth appears to be substrate sensitive and film thickness also has an influence on the crystallization of films. High-resolution transmission electron microscopy images show clear lattice spacing of ZnO in nanolaminates, indicating that ZnO layers are polycrystalline with preferred (002) orientation while TiO2 layers are amorphous. 相似文献
18.
《Ceramics International》2015,41(8):9420-9425
Novel α-Fe2O3 modified ZnO flower-like microstructures were successfully prepared via a simple and rapid solution route with different α-Fe2O3 contents. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–vis diffuse reflectance spectra (UV–vis DRS) and N2 adsorption/desorption. Photocatalytic activity of the as-prepared α-Fe2O3/ZnO composites was evaluated by degradation of pentachlorophenol (PCP) under simulated solar light. The results indicated that α-Fe2O3/ZnO composites showed higher photocatalytic activity than pure ZnO. The optimum photocatalytic activity of α-Fe2O3/ZnO composite with molar ratio of 1:7 was nearly 2 times as high as that of pure ZnO. The remarkably increased performance of α-Fe2O3/ZnO was mainly attributed to the synergistic effect between α-Fe2O3 and ZnO. In addition, the α-Fe2O3/ZnO composites also showed excellent circulation stability. 相似文献
19.
MnOx–CeO2 mixed oxide catalysts prepared by sol–gel method were tested for the catalytic combustion of chlorobenzene (CB), as a model of chlorinated aromatic volatile organic compounds (CVOCs). MnOx–CeO2 catalysts with the different ratio of Mn/Ce + Mn were found to possess high catalytic activity for catalytic combustion of CB, and MnOx(0.86)–CeO2 was the most active catalyst, on which the complete combustion temperature (T90%) of chlorobenzene was 236 °C. The stability of MnOx–CeO2 catalysts in the CB combustion was investigated. MnOx–CeO2 catalysts with high Mn/Ce + Mn ratios present high stable activity, which is related to their high ability to remove Cl species adsorbed and a large amount of active surface oxygen. 相似文献
20.
Nickel catalysts over the CeO2-ZrO2 solid solution were successfully prepared by the co-precipitation method for partial oxidation of methane. The structures of the catalysts were systematically examined by N2 adsorption/desorption, CO chemisorption, X-ray diffraction (XRD) and H2-TPR techniques. The catalytic performance and carbon deposition were investigated for partial oxidation of methane as well. The results showed that the Ni/CeO2-ZrO2 catalysts had a large BET area and fine Ni dispersion. By the co-precipitation method, Ni and CeO2-ZrO2 solid solution had strong interaction confirmed by the H2-TPR analysis. The Ni/CeO2-ZrO2 catalysts showed high activity and stability and the Ni/Ce0.25Zr0.75O2 exhibited the best activity and coking resistance among these catalysts. The catalytic activities and coking resistant behaviors of catalysts were affected by the surface and structural properties of the catalysts. 相似文献