共查询到20条相似文献,搜索用时 15 毫秒
1.
Betina Jørgensen Steffen Buus Kristensen Andreas Jonas Kunov-Kruse Rasmus Fehrmann Claus Hviid Christensen Anders Riisager 《Topics in Catalysis》2009,52(3):253-257
The gas-phase oxidation of aqueous ethanol with dioxygen has been examined with a new nanoparticle V2O5/TiO2 catalyst. Product selectivity could to a large extent be controlled by small alterations of reaction parameters, allowing
production of acetaldehyde at a selectivity higher than 90%, near quantitative conversion at 175–200 °C. Furthermore, a selectivity
above 80% for acetic acid could be achieved at low gas hourly space velocity at temperatures as low as 165 °C. 相似文献
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K. Deplanche I. P. Mikheenko J. A. Bennett M. Merroun H. Mounzer J. Wood L. E. Macaskie 《Topics in Catalysis》2011,54(16-18):1110-1114
We report a novel biochemical method based on the sacrificial hydrogen strategy to synthesise bimetallic Au/Pd nanoparticles supported on bacterial cells. The synergistic effect of Au/Pd over monometallic preparations was demonstrated in the oxidation of benzyl alcohol. The bioinorganic catalysts outperformed a commercial Pd catalyst (5% Pd/C) showing no deactivation and high selectivity towards benzaldehyde. 相似文献
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After a high-temperature reduction (HTR) at 773 K, TiO2-supported Au became very active for CO oxidation at 313 K and was an order of magnitude more active than SiO2-supported Au, whereas a low-temperature reduction (LTR) at 473 K produced a Au/TiO2 catalyst with very low activity. A HTR step followed by calcination at 673 K and a LTR step gave the most active Au/TiO2 catalyst of all, which was 100-fold more active at 313 K than a typical 2% Pd/Al2O3 catalyst and was stable above 400 K whereas a sharp decrease in activity occurred with the other Au/TiO2 (HTR) sample. With a feed of 5% CO, 5% O2 in He, almost 40% of the CO was converted at 313 K and essentially all the CO was oxidized at 413 K over the best Au/TiO2 catalyst at a space velocity of 333 h–1 based on CO + O2. Half the chloride in the Au precursor was retained in the Au/TiO2 (LTR) sample whereas only 16% was retained in the other three catalysts; this may be one reason for the low activity of the Au/TiO2 (LTR) sample. The reaction order on O2 was approximately 0.4 between 310 and 360 K, while that on CO varied from 0.2 to 0.6. The chemistry associated with this high activity is not yet known but is presently attributed to a synergistic interaction between gold and titania. 相似文献
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The oxidation of glycerol by molecular oxygen in the aqueous phase over Au/TiO2 was investigated in both a batch reactor and a continuous upflow fixed bed reactor. The effects of catalyst particle size,
gas flow rate, liquid flow rate, reaction temperature, dioxygen pressure, and solution pH were examined in the fixed bed system.
The unique hydrodynamics of the fixed bed system allowed for secondary oxidation products such as tartronic acid and oxalic
acid to form in substantial amounts, which contrasts the product distribution observed in a batch system. These results suggest
that reactor configuration can play an important role in the observed product selectivity from oxidation reactions over highly
active gold catalysts. 相似文献
5.
Gaomeng Lü Rui Zhao Guang Qian Yanxing Qi Xiaolai Wang Jishuan Suo 《Catalysis Letters》2004,97(3-4):115-118
The liquid-phase highly efficient selective oxidation cyclohexane to cyclohexanol and cyclohexanone over Au/MCM-41 catalyst was carried out in a solvent-free system, which oxygen as the only oxidant and the reaction conditions are very moderate. The Au/MCM-41 was characterized by XRD, N2adsorption/desorption, UV-Vis, XPS, and ICP-AES. 相似文献
6.
Jianyi Shen Josephine M. Hill Ramchandra M. Watwe S.G. Podkolzin J.A. Dumesic 《Catalysis Letters》1999,60(1-2):1-9
Ethylene adsorption on a Pt/Au/SiO2 catalyst (2 wt% Pt; Au/Pt atomic ratio of 10) was studied using adsorption microcalorimetry and FTIR spectroscopy. Ethylene
adsorption at 300 K on Pt/Au/SiO2 produced π‐bonded, di‐σ‐bonded, and ethylidyne species with an initial heat of 140 kJ/mol, compared to a heat of 157 kJ/mol
for Pt/SiO2 on which only ethylidyne species formed. At 203 and 263 K, ethylene adsorbed on Pt as well as on Au surface atoms for the
Pt/Au/SiO2 catalyst. Quantum chemical, DFT calculations indicate that Au exerts a significantly smaller electronic effect on Pt than
does addition of Sn to Pt.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Decomposition of tannic acid in aqueous solution in advanced oxidation processes has been studied. Different oxidizing agents: ozone, hydrogen peroxide and UV radiation have been used both as single and mutually combined components of the system. The course of reaction was examined by the changes of chemical oxygen demand (COD) and total organic carbon (TOC) in aqueous solutions. Particular attention has been paid to determine optimal concentration of hydrogen peroxide, when it is used alone, together with O3 and in H2O2+O3+UV combination. The most effective optimal concentration of H2O2 was found. The entire mineralization of tannic acid into final products CO2 and H2O can be accomplished in all combinations of advanced oxidation with ozone. Bacteriological test ToxAlert® with luminescence bacteria Vibro fisheri proved that toxicity of solutions decreased considerably during advanced oxidation of tannic acid solution. 相似文献
8.
Nina Hammer Karina Mathisen Tina Zscherpe De Chen Magnus R?nning 《Topics in Catalysis》2011,54(13-15):922-930
The impact of thermal treatment at various preparation stages of carbon supported Au/TiO2 catalysts prior to oxidation of CO in the presence and absence of hydrogen was studied. An increase in catalytic activity for thermally treated samples due to a more ordered structure of TiO2 was observed. A reversible deactivation of the catalysts occurred in the absence of hydrogen. However, the activity was restored at preferential CO oxidation conditions in presence of hydrogen. 相似文献
9.
Yu Pei Jiang Junxiang Chen Can Wang Zhong Wang Da Li Guangci Li Xuebing 《Catalysis Letters》2022,152(10):3046-3057
Catalysis Letters - Catalytic selective hydrogenation of esterified malic acid to produce 1,2,4-butanetriol (1,2,4-BT) using H2 as the reducing reagent suffers from the low 1,2,4-BT selectivity.... 相似文献
10.
Mesoporous Au/TiO2 Catalysts for Low Temperature CO Oxidation 总被引:1,自引:0,他引:1
Y. Denkwitz J. Geserick U. Hörmann V. Plzak U. Kaiser N. Hüsing R. J. Behm 《Catalysis Letters》2007,119(3-4):199-208
The activity and stability of structurally well defined mesoporous Au/TiO2 catalysts with different support morphologies and pore sizes for low temperature CO oxidation was investigated by kinetic
measurements and in-situ IR spectroscopy. The resulting catalysts with Au particle sizes of ∼3 nm exhibit a high activity
for CO oxidation, similar to or exceeding that of highly active standard Au/TiO2 catalysts with similar size Au nanoparticles and loading, and a significantly lower tendency for deactivation. Possible reasons
for the improved performance of these catalysts are discussed. 相似文献
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聚乙烯醇在乙醇水溶液中缩醛化的研究 总被引:4,自引:1,他引:4
聚乙烯醇(PVA)在乙醇水溶液中在酸性条件下与醛类缩醛化制成PVA缩醛的乙醇水溶液。缩醛化度可由乙醇的浓度来控制。PVA缩醛的乙醇水溶液经氧化降解后可直接用作配制胶粘剂和涂料的胶料。 相似文献
14.
Au colloid and titania in different sequence or Au-oxide nano ensembles preformed in hydrosol were deposited on inert amorphous silica or mesoporous SBA-15. It was compared with gold colloid adsorbed on TiO2 or silica support. The formation of the Au/TiO2 interface is discussed in terms of surface charges. Preferential CO oxidation in the presence of hydrogen (PROX) has been correlated with the CO oxidation activity and structural properties, perimeter and the influence of the TiO2 morphology on the catalytic activity has been demonstrated. 相似文献
15.
Ghizlane Abdelli 《臭氧:科学与工程》2016,38(3):233-241
The aim of this work was studying the activity of a Ru/CeO2 powder catalyst in the ozonation of aqueous solution of cyanuric acid (CYA). Ozonation in the presence of the catalyst significantly enhances CYA degradation. Within this work, investigation of the influence of pH and initial concentration on the catalytic ozonation of CYA has been done in a semicontinuous reactor. The removing degree of CYA at pH 5.9 show better response in comparison to pH 2.5 and pH 8.2. The mineralization of CYA by catalytic ozonation formed nitrate ions (0.7 mol of NO3?/mol of CYA removed for 50% initial CYA abatement) and nitrite and ammonium ions in small amounts. Three transformation products formed during catalytic ozonation were identified from LC/MS and MS/MS analyses. The impact of oxidation on the toxicity was measured from the inhibition of Vibrio fisheri, which was found to increase continuously. 相似文献
16.
Well‐dispersed PtSnEu/C and PtSn/C catalysts were prepared by the impregnation–reduction method using formic acid as a reductant and characterised by X‐ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersion X‐ray spectroscopy (EDX) and X‐ray photoelectron spectroscopy (XPS). The synthesised catalysts with different atomic ratios of Pt/Sn/Eu have the Pt face centered cubic (fcc) structure and their particle sizes are 3–4 nm. The PtSnEu/C catalyst is composed of many Pt (0), SnO2, Eu(OH)3, a small amount of Pt(II) and partly alloyed PtSn, but no metallic Eu. The electrochemical measurements indicate that in comparison with Pt3Sn1/C catalyst, the Pt3Sn1Eu1/C catalyst for ethanol oxidation has more negative onset potential, smaller apparent activation energy and lower electrochemical impedance so that it exhibits very high catalytic activity. Its peak current density increases by 135% and 40%, compared with Pt3Sn1/C and Pt1Ru1/C (JM) catalysts, respectively. This is because the Eu(OH)3 formed by adding Eu to PtSn/C catalyst can provide the OH group which is in favour of the removal of adsorbed intermediates and ethanol oxidation. 相似文献
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许小平 《中国化学工程学报》2003,11(3):264-268
N-isopropylacrylamide (NIPAAm) was used to synthesize NIPAAm homopolymer (nonionized) and NIPAAm-sodium methacrylate copolymer (ionized). The swelling equilibria for both gels were obtained in aqueous solution of ethanol with concentration ranging from 0 to 100%(by mass) at 25℃. The swollen gel in water shrank first with the addition of a small amount of ethanol and then reswelled with further addition of ethanol showing not only a discontinuous volume phase transition but also a typical reentrant phenomenon. A thermodynamic model based on the UNIQUAC with the “free-volume“ contribution was applied to correlate and predict the swelling behavior of the poly(NIPAAM)-gels in ethanol-water mixture. 相似文献