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排序方式: 共有149条查询结果,搜索用时 15 毫秒
71.
钍含量对Co/HMS催化剂结构和费托合成的影响 总被引:3,自引:1,他引:2
详细研究了钍含量对15% Co/HMS催化剂结构、费托合成CO转化率和烃分布的影响, 结果表明: 钍助剂的添加降低了催化剂的钴还原度, 并可使催化剂钴晶粒减小, 且存在钍物种对钴物种的覆盖; 钴晶粒的减小、较高钍含量时催化剂里钍物种对钴物种的覆盖和钴物种还原性能的降低, 使催化剂存在最优的钍含量, 此时催化剂表面暴露的金属钴原子最多, 较好地解释了钍含量达到1.5 wt%时, 催化剂CO转化率最高的实验现象. 烃分布研究表明: 反应温度较低时钍助剂将促进产物链的增长和高碳烃选择性的增加, 但反应温度较高时难以促进产物链的增长. 相似文献
72.
M. K. Bhide M. D. Sastry U. R. K. Rao N. D. Dahale N. C. Jayadevan 《Phase Transitions》2013,86(3):199-208
The paper presents the EPR evidence for the occurrence of phase transitions in (NH4)4ThF8 and (NH4)3ThF7. In both cases the Cu2+ probe occupies a NH4+ site and predominantly experiences a dynamic coordination, either due to dynamic Jahn-Teller effect, or due to fluxional behaviour of surrounding (ThF8)4- units in (NH4)4ThF8. It is proposed that the structural phase transition in this compound at 214 K is associated with the transition of the dynamic coordination of Cu2- into a static one, probably due to freezing of motion of (ThF8)4- units below this temperature. In (NH4)3ThF7 the dynamic features of the Cu2+ EPR spectrum are absent and characteristics of a local orthorhombic symmetry are seen down to 77 K. However, in the high temperature range a change from orthorhombic to axial symmetry is observed at 524 K, possibly due to a phase transition. 相似文献
73.
《Analytical letters》2012,45(19-20):2001-2009
Abstract Thorium(IV)salts were found to act as catalysts for the alkylation of 4-(p-nitrobenzyl)pyridine by T-2 toxin. Using thorium(IV)chloride as the catalyst, a detection procedure for T-2 toxin was developed that required a heating step consisting of only 2 minutes at 90°C. The limit of detection of T-2 toxin with this procedure was found to be 1 microgram. 相似文献
74.
《Analytical letters》2012,45(2):93-97
Abstract It has been demonstrated that copper (II) is an attractive amperometric indicator for the titration of small amounts of thorium in solution. EDTA was used as the titrant. Best results are obtained in the titration when the mole ratio of thorium to copper is high. The method should be applicable to several other metal ions that form more stable EDTA complexes than does copper. 相似文献
75.
《Analytical letters》2012,45(9):1005-1008
Abstract Thorium has been determined amperometrically at an applied e. m. f. of -1.2V with fifteen maleanilic acids. Out of these o-tolyl, p-tolyl, 1-naphthyl, 2-naphthyland 4-amino maleanilic acid were found promising analyticalreagentsand most effective. Th(IV) in the range 6.60 to 2350.0 mg per 100 ml can be determined with an error of ± 0.2%. The interference of fifty-five ions were studied and only five ions Zn(II), Pb(II), Fe(III), UO2 (II) and Zr(IV) interfered. which could be masked by the addition of S2O2 3 or SCN?, Cl? or SO2- 4, SCN? or citrate, citrate or tartrate and P2O4- 7 respectively. 相似文献
76.
Hamid Heshmati Hossein Ghanadzadeh Gilani Amir Haidary 《Journal of Dispersion Science and Technology》2014,35(4):501-509
In this study, an amidoximated chelating ion exchange resin was prepared by poly-acrylonitrile (PAN) grafted potato starch. The adsorbent characterizations such as specific surface area, pore volume, average pore radius, and Fourier transform infrared (FTIR) spectrum of the resin were measured. The effects of pH, adsorbent dosage, contact time, initial concentration of thorium ion, and temperature on adsorption of thorium ion from aqueous solutions were investigated. Four isotherm models including Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin were applied to analyze the equilibrium isotherm data. The results showed that Langmuir and Temkin models had a good agreement with experimental data. The maximum capacity of the adsorbent using the Langmuir isotherm model was 227.27 mg · g?1. The kinetic models like pseudo-first-order, pseudo-second-order, Elovich, and intraparticle were examined to describe the adsorption process. The kinetics of the adsorption process was found to follow the pseudo-second-order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, ΔS°) were also calculated using equilibrium constant values at various temperatures (25, 35, 45, 55°C) and the positive value for ΔH° showed an endothermic adsorption process. The study suggests that the prepared adsorbent has promising potential for the removal of thorium from wastewaters. 相似文献
77.
S. Ganesan 《Pramana》2007,68(2):257-268
The development of accelerator driven sub-critical systems (ADSS) require significant amount of new nuclear data in extended
energy regions as well as for a variety of new materials. This paper reviews these perspectives in the Indian context.
相似文献
78.
Die zeitraubenden Berechnungen der optimal arbeitenden Trennkaskade mittels der von Onsager aufgestellten 2 In q-Regel lassen sich vermeiden, wenn man das Problem vom allgemeinen Standpunkt aus mittels der Variationsrechnung behandelt. Die Hamiltonsche charakteristische Funktion des Variationsproblems tritt bei Cohen als ?value function” auf und stellt ein unmittelbares Maβ für den minimalen Energieaufwand bei einem Trennverfahren dar. Die konsequente Weiterführung der Theorie erlaubt es schlieβlich, die Schar aller optimal arbeitenden Trennkaskaden auf einfache Weise zu ermitteln. Schlieβlich läβt sich damit auch noch das Problem der rechteckigen Kaskaden lösen. 相似文献
79.
M. Saldideh M. Shayesteh M. Eshghi 《中国物理C(英文版)》2014,(8):111-115
In this paper, we have investigated the prospects of exploiting the rich world thorium reserves using Canada Deuterium Uranium (CANDU) reactors. The analysis is performed using the Monte Carlo MCNP code in order to understand how much time the reactor is in criticality conduction. Four different fuel compositions have been selected for analysis. We have obtained the infinite multiplication factor, k∞, under full power operation of the reactor over 8 years. The neutronic flux distribution in the full core reactor has already been investigated. 相似文献
80.
Picardo MC de Melo Ferreira AC Augusto da Costa AC 《Applied biochemistry and biotechnology》2006,134(3):193-206
In the present work, the biosorption of radioactive thorium was investigated using a dry biomass of Sargassum filipendula as the biosorbent material. Radioactive solutions containing between 2.0 and 500.0μg thorium were tested by biosorption with
S. filipendula, yielding uptake capacities from 20 to 100%, depending on the concentration of the solution. Kinetic studies indicated that
equilibrium between the thorium solution and the solid fraction was achieved after three hours of contact and that a second-order
model could express the equilibrium kinetics. In order to investigate the maximum biosorption capacity of the biomass an isotherm
was done, based on the experimental data, which revealed the maximum uptake capacity to be 2.59 μmol thorium/g biomass. The
experimental data fitted well to a Langmuir model, which provided a good correlation between the experimental and predicted
thorium uptake values. 相似文献