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采用浸渍法制备了一系列Ag/ZrO2催化剂, 考察了Ag/ZrO2催化剂对1,2-丙二醇选择性氧化合成丙酮醛反应的催化性能. 实验结果表明: 在原料气配比为V(N2)∶V(O2)=300∶19, n(O2)/n(alcohol)=1.2, 反应物液时空速为3.2 g/(g•h), 反应温度为673 K时, 1,2-丙二醇选择性氧化合成丙酮醛反应的转化率为95.7%, 选择性为55.3%, 高于传统电解银催化剂. UV-Vis DRS和XPS的研究结果表明: 在Ag/ZrO2催化剂上存在大量的Ag+和Agnδ+有利于促进催化活性的提高. 相似文献
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以溶剂热法制备了Fe3O4@SiO2-PSS@UiO-66结构的磁性多孔复合材料,并利用XRD,TEM,SEM,IR,TG,VSM 和N2吸附-脱附对样品的结构和形貌进行测试表征。研究结果表明:磁性UiO-66复合材料是以球型Fe3O4为核,MOF为壳的核-壳结构,其表面的MOF层由多个立方多晶堆积组装而成,且具有良好的超顺磁性。进一步研究了Fe3O4@SiO2-PSS@UiO-66对2-硝基-1,3-苯二酚的吸附性能。探讨了吸附时间,吸附量和2-硝基-1,3-苯二酚初始浓度在吸附过程中的影响,结果表明:当吸附时间为12 h,吸附剂的用量为5 mg,2-硝基-1,3-苯二酚浓度为400 mg·L-1时,最大吸附量为161.36 mg·g-1。另外,磁性UiO-66复合材料对2-硝基-1,3-苯二酚高的吸附性能可能是由于UiO-66与2-硝基-1,3-苯二酚之间的静电作用以及二者之间苯环的π-π作用。 相似文献
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研究了以(-)-α-蒎烯为原料合成(-)-异松蒎酮的反应. 以四氢呋喃为溶剂, 硼氢化钠与三氟化硼乙醚溶液生成的硼烷不经分离直接与α-蒎烯发生反马氏加成反应, 生成二异松蒎烷基硼; 采用四水合过硼酸钠或NaOH-H2O2氧化硼氢化物得到(+)-异松蒎醇, 产率为89.5%, 纯度97.4%, 熔点为55~56 ℃, 比旋光度 +28.31 (c 5.55, CH3OH). 以钒磷氧化物为催化剂、双氧水作氧化剂, 将(+)-异松蒎醇氧化得到(-)-异松蒎酮, 产率88% 以上, 纯度96.0%, 比旋光度为 -10.58 (c 5.51, CH3OH). 采用IR, MS, 1H NMR, 13C NMR等对(+)-异松蒎醇和(-)-异松蒎酮结构进行了表征. 相似文献
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The luminescent properties of Pr3+-doped LaB3O6, SrAl12O19, SrB4O7 and NaYF4 in the vaccum ultraviol-et (VUV) range at different temperatures were investigated under the excitation of high-energetic synchrotron radiation. For Pr3+ ions in LaB3O6, SrAl12O19 and SrB4O7, only the parity-forbidden 1S0→4f2 transitions were observ-ed in the emission spectra at relatively low temperature; but the parity-allowed 4f5d→4f2 transitions appeared simultaneously when the temperature was high enough. And the intensity of broad 4f5d→4f2 emission increased relative to the intensity of 1S0→4f2 emissions with increasing temperature. Then the thermal equilibrium model of energy levels was employed to the lowest 4f5d state and 1S0 state of Pr3+ in the three hosts. The calculated curves were in good agreement with the experimental values, indicating the occurrence of the thermal excitation from 1S0 state to 4f5d states at high temperatures when the lowest 4f5d state lies higher than 1S0 state and the photon energy is high enough. 相似文献
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通过简易、可控的水热方法在泡沫镍基体上直接生长了核壳结构的阵列型Co3O4@δ-MnO2/Pt正极。阵列电极有利于电极的润湿、氧气的传输和Li2O2的负载。Co3O4@δ-MnO2/Pt正极对氧还原和氧析出反应具有高的催化性能,可促使Li2O2依附Co3O4@δ-MnO2/Pt阵列生长,从而保持阵列结构。该生长行为有利于Li2O2在充电时分解。以Co3O4@δ-MnO2/Pt为催化正极的锂氧电池显示出高的容量(在电流密度100 mA·g-1时容量为2 480 mAh·g-1),以及长的循环寿命(容量限定在500 mAh·g-1时,在200 mA·g-1电流密度下,可循环65次),该性能超过了使用Co3O4或Co3O4@δ-MnO2催化剂的电池。 相似文献
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P?ivi M?ki-Arvela Serap Sahin Narendra Kumar Jyri-Pekka Mikkola Kari Er?nen Tapio Salmi Dmitry Yu. Murzin 《Reaction Kinetics and Catalysis Letters》2008,94(2):281-288
Liquid phase tert-butylation of m-cresol was carried out using 12-tungstosilicic acid supported on neutral alumina by varying different parameters. The reaction
has also been carried out by using calcined samples under optimized conditions. The present catalyst shows an excellent activity
of 93.2%, conversion of 100% selectivity for the o-isomer, an important industrial product. 相似文献
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Maria Cyfert Barbara Latko Maria Wronska 《Monatshefte für Chemie / Chemical Monthly》1980,111(3):619-626
The influence of NaClO4, NaCl and Na2SO4 on the oxidation of Fe(phen)
3
2+
by Ce(IV) was investigated by means of the stopped-flow method. At the concentrations range of NaClO4 and NaCl 0.1–1.0M the rate constant values decrease from 1.03·105 to 0.56·105M–1s–1 and from 1.08·105 to 0.81·105M–1s–1 respectively.In varying concentrations of Na2SO4 solutions (0.05–0.35M) the rate constant values decrease from 1.05·105M–1s–1 to 0.45·105M–1s–1.Taking into account the negative salt effect the mechanism of the reaction progress is proposed. 相似文献
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S. A. Grabovskiy Q. K. Timerghazin N. N. Kabal’nova 《Russian Chemical Bulletin》2005,54(10):2384-2393
Oxidation of a series of tert-butyl ethers ButOR (R = Me, Et, CH2CH2Cl, Pri, Bui), diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, diisobutoxymethane, 1,4-dioxane, and tetrahydrofuran with dimethyldioxirane
(DMDO) was studied. The reaction kinetics obeys the second-order equation w = k[DMDO][ether]. The rate constants in a range of 5–50 °C and the activation parameters of the reaction were determined. The
solvent effect on the oxidation rate was studied. The oxidation products are the corresponding alcohols and carbonyl compounds.
The competition between the nonradical (oxygen insertion) and radical mechanisms of the reaction is discussed. The reactions
of the parent dioxirane and DMDO with a series of methyl ethers MeOr’ (r’ = Me, Et, CH2CH2F, Pri) were studied by the density functional theory (DFT). The (U)B3LYP-6-311G(d,p) method was employed to calculate the geometry
and energies of the reactants and transition states. The data obtained indicate a possible increase in the probability of
oxidation via the radical route and an increase in the activation barrier for the substrates containing electron-withdrawing substituents.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2309–2318, October, 2005. 相似文献
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Shukor MY Habib SH Rahman MF Jirangon H Abdullah MP Shamaan NA Syed MA 《Applied biochemistry and biotechnology》2008,149(1):33-43
A molybdate-reducing bacterium has been locally isolated. The bacterium reduces molybdate or Mo6+ to molybdenum blue (molybdate oxidation states of between 5+ and 6+). Different carbon sources such as acetate, formate,
glycerol, citric acid, lactose, fructose, glucose, mannitol, tartarate, maltose, sucrose, and starch were used at an initial
concentration of 0.2% (w/v) in low phosphate media to study their effect on the molybdate reduction efficiency of bacterium. All of the carbon sources
supported cellular growth, but only sucrose, maltose, glucose, and glycerol (in decreasing order) supported molybdate reduction
after 24 h of incubation. Optimum concentration of sucrose for molybdate reduction is 1.0% (w/v) after 24 h of static incubation. Ammonium sulfate, ammonium chloride, valine, OH-proline, glutamic acid, and alanine (in
the order of decreasing efficiency) supported molybdate reduction with ammonium sulfate giving the highest amount of molybdenum
blue after 24 h of incubation at 0.3% (w/v). The optimum molybdate concentration that supports molybdate reduction is between 15 and 25 mM. Molybdate reduction is optimum
at 35 °C. Phosphate at concentrations higher than 5 mM strongly inhibits molybdate reduction. The molybdenum blue produced
from cellular reduction exhibits a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. The
isolate was tentatively identified as Serratia marcescens Strain Dr.Y6 based on carbon utilization profiles using Biolog GN plates and partial 16s rDNA molecular phylogeny. 相似文献
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Ching-Tu Chang Biing-Jye Liaw Yu-Pei Chen Yin-Zu Chen 《Journal of molecular catalysis. A, Chemical》2009,300(1-2):80-88
Gold catalysts, supported on a solid base of MgxAlO hydrotalcite, were prepared by a modified deposition precipitation method for CO selective oxidation. The preparation parameters and pretreatment of the catalysts were investigated. The pH and the HAuCl4 concentration in the initial solution, and the Mg/Al molar ratio of MgxAlO affected the pH in the final solution and determined the actual gold loading of the catalyst. The calcination temperatures of the MgxAlO support and the Au/MgxAlO catalyst dominated the Au3+/Au0 ratio on the catalyst. The pretreatment of the catalyst as well as the gold loading and the Au3+/Au0 ratio, critically determined the activity of the catalyst for CO selective oxidation. Based on XPS and in situ DR-FTIR analyses, a mechanism for CO selective oxidation on 2%Au/Mg2AlO was proposed. The hydroxyl group on Mg2AlO also participated in the reaction. 相似文献
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The kinetics of the oxidation of five catecholamines viz., dopamine (A), L-dopa (B), methyldopa (C), epinephrine (D) and norepinephrine
(E) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in presence of HClO4 was studied at 30±0.1 °C. The five reactions followed identical kinetics with a first-order dependence on [CAT]
o
, fractional-order in [substrate]
o
, and inverse fractional-order in [H+]. Under comparable experimental conditions, the rate of oxidation of catecholamines increases in the order D>E>A>B>C. The
variation of ionic strength of the medium and the addition of p-toluenesulfonamide or halide ions had no significant effect
on the reaction rate. The rate increased with decreasing dielectric constant of the medium. The solvent isotope effect was
studied using D2O. A Michaelis-Menten type mechanism has been suggested to explain the results. Equilibrium and decomposition constants for
CAT-catecholamine complexes have been evaluated. CH3C6H4SO2NHCl of the oxidant has been postulated as the reactive oxidizing species and oxidation products were identified. An isokinetic
relationship is observed with β=361 K, indicating that enthalpy factors control the reaction rate. The mechanism proposed
and the derived rate law are consistent with the observed kinetics. 相似文献
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Akihiko Tsuda Atsuhiro Osuka 《Journal of inclusion phenomena and macrocyclic chemistry》2001,41(1-4):77-81
The AgI-promoted oxidative meso-meso coupling reaction of 5,15-diaryl ZnII-porphyrins is advantageous in light of its high regioselectivity as well as its easy extension to large porphyrin arrays. Linear meso-meso linked porphyrin 128-mer and three-dimensionally arranged grid porphyrin 48-mer were isolated in a discrete form by repetitive oxidation reaction and subsequent gel-permeation chromatography (GPC)-HPLC. 5,15-Diaryl CuII-, NiII-, and PdII-porphyrins were converted to meso- doubly-linked diporphyrins by oxidation with(p-BrC6H4)3NSbCl6. End-aryl-capped meso-meso linked CuII-, NiII-, and PdII- diporphyrins were converted to completely fused meso-meso - -triply-linked diporphyrins through the oxidative ring closure (ODRC) reaction with (p-BrC6H4)3NSbCl6. Finally, we found that ScIII-catalyzed oxidation with DDQ gave a very efficient ODRC reaction and hence allowed the synthesis of triply-linked oligoporphyrins up to 12-mer. 相似文献
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V. I. Minkin M. S. Korobov R. Ya. Olekhnovich G. S. Borodkin L. E. Nivorozhkin 《Russian Chemical Bulletin》1995,44(11):2168-2171
Kinetics and reaction mechanisms governing inversion of the tetrahedral configuration at the metal center in the series ofbis-chelate Zn(II) complexes of 3,2-, 1,2-, and 2,1-oxy(mercapto)naphthaldimines, respectively4–6, have been studied with the use of dynamic1H NMR spectroscopy. A polytopal rearrangement of the diagonal twist type has been found to be an energetically preferable pathway of the inversion reaction for complexes4 and5 with a ZnN2O2 coordination site, whereas the inversion reaction for complexes with a ZnN2S2 coordination site occurs by an intramolecular dissociation-recombination pathway that involves cleavage of a Zn-N coordination bond. In the case of complexes6, the inversion reaction is governed mainly by intramolecular degenerate ligand exchange reactions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11. pp. 2261–2265, November, 1995.This work was supported by the Russian Foundation for Basic Research (project No. 93-03-18692) and the International Science Foundation (grant No. RNJ 000). 相似文献