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1.
The hydrogenation of CO2 has been studied at atmospheric pressure on Co/C and Ni/C catalysts and the results are compared with those obtained on unsupported Co and Ni. Specific activites in the form of turnover frequencies for CO2 hydrogenation decrease with increasing metal dispersity. Carbon supported Co and Ni present a smaller selectivity for methane than bulk metals. Higher specific activities and smaller activation energies are obtained on Co catalysts, compared with those determined for Ni catalysts.
CO2 Co/ Ni/ Co Ni . CO2 . Co Ni , . .相似文献
2.
Pt/Ce0.75Zr0.25O2的催化性能及其氧移动性的 18O 同位素交换表征 总被引:1,自引:0,他引:1
采用浸渍法制备了Pt/Ce0.75Zr0.25O2催化剂,考察了催化剂对乙醇及CO的氧化活性,并采用 18O 同位素交换、乙醇程序升温表面反应(C2H5OH-TPSR)、一氧化碳程序升温脱附(CO-TPD)和程序升温还原(H2-TPR)等技术对催化剂进行了表征. 结果表明, Pt/Ce0.75Zr0.25O2催化剂表现出较高的乙醇和CO氧化活性,其催化活性随着Pt负载量的增加而提高. 当Pt负载量为3%时,活性最高. 继续增加Pt负载量,催化剂活性下降. C2H5OH-TPSR和CO-TPD结果表明,催化剂对乙醇或CO的氧化活性与从催化剂表面脱附出来的CO2量有对应关系, CO2脱附量越大,催化剂活性越高. 18O 同位素交换结果表明,表面氧交换能力与其氧化活性有一定对应关系,催化剂的表面氧交换能力越高,氧化活性越高. 相似文献
3.
B. Bachiller-Baeza A. Guerrero-Ruiz I. Rodríguez-Ramos 《Applied Surface Science》2007,253(10):4805-4813
Ruthenium-supported catalysts modified by the addition of Mg, Na or Ce were studied in the selective hydrogenation of paracetamol (4-acetamidophenol) to cis- and trans-4-acetamidocyclohexanol. In both series, catalysts supported on carbon or on alumina, the modified catalysts were more selective to the trans isomer than the corresponding monometallic catalysts. However, the modified catalysts, particularly the supported on carbon, were less active. Moreover, there is a reduction in the hydrogenolysis reaction of the OH group on carbon-supported catalysts. The enhancement observed in the stereoselectivity for the modified catalysts may be explained by an alteration in the acid-base properties of the catalyst surface, which eventually control the mode of adsorption of the molecule of paracetamol and probably the tautomeric equilibrium of the 4-acetamidocyclohexene-1-ol intermediate. The optimum amount of promoter to improve the stereoselectivity seems to depend on the inherent acid-base characteristics of both the modifier and the support. Therefore, the proper adjustment or fine tuning of these parameters is crucial for obtaining the best results in terms of stereoselectivity. 相似文献
4.
L. Gonzalo-Chacón A. Arcoya I. Rodríguez-Ramos E. Gallegos-Suárez A. Guerrero-Ruiz 《Adsorption》2011,17(3):595-602
Modifications of texture and surface properties of a commercial activated carbon (Norit GF-40) were performed by several treatments
in order to study their effects on the selective adsorption of nitromethane from nitromethane/water vapor mixtures. Characterisation
of the samples by nitrogen adsorption and thermal analysis showed that HNO3 treatments produce important losses of porosity and surface area, accompanied of an increase of oxygenated functional groups
on the surface of carbon, which are progressively removed by heating at temperatures between 573 and 1073 K. All this leads
to a drastic decrease of the adsorption capacity per gram of adsorbent with respect to the raw carbon, which offers, on the
other hand, the best adsorptive performance. Oxidation by H2O2 does not practically affect its textural properties and introduces an important amount of oxygen functional groups at the
surface, but changes in the adsorptive properties of carbon are insignificant. Sample oxidised by H2O2 and subsequently treated by diethylentriamine shows a decrease in adsorption capacity, without any relevant loss of surface
area. The raw carbon treated at high temperature that exhibits the highest surface area and where surface functional groups
are absent, showed the greatest adsorption capacity for nitromethane, being much more selective for nitromethane than for
water, in nitromethane-water mixtures. Adsorption capacity values for nitromethane on the different samples are related to
the extent of the surface area, while water vapour adsorption seems to depend on the population of functional groups at the
surface, which may work as adsorption sites. 相似文献
5.
Ayari Faouzi Mannei Emna Asedegbega-Nieto Esther Mhamdi Mourad Guerrero-Ruiz Antonio Ricardo Delahay Gérard Ghorbel Abdelhamid 《Journal of Thermal Analysis and Calorimetry》2018,131(2):1295-1306
Journal of Thermal Analysis and Calorimetry - Thermal decomposition (2 K min?1) of ammonium heptamolybdate tetrahydrate, performed between room temperature and... 相似文献
6.
A. Guerrero-Ruiz 《Reaction Kinetics and Catalysis Letters》1993,49(1):53-60
Hydrogen and carbon monoxide chemisorption on supported platinum catalysts have been studied volumetrically and the adsorption heats determined by microcalorimetric measurements. From the results of this study is concluded that the use of reversible (or second) isotherms as a measure of weak chemisorption would appear inadequate. 相似文献
7.
Comparative Study of the Adsorption from Aqueous Solutions and the Desorption of Phenol and Nonylphenol Substrates on Activated Carbons 总被引:1,自引:0,他引:1
Adsorption of phenol and nonylphenol from aqueous solutions on microporous activated carbons has been studied. The phenol isotherm changes from L-shaped for surface oxygen group free carbon (I sample) to a two-stepped isotherm for oxidized carbon (IN sample, HNO(3) treated) Furthermore, the adsorbed amounts diminish in about 25% on IN carbon. It is proposed that a change in the adsorption mechanism take place; i.e., weak interaction forces between the pi electrons in phenol and the pi electron in carbon are present on the original I carbon, while a donor-acceptor complex on the oxidized IN carbon is operating between basic surface oxygen groups and phenol aromatic rings. The shape of nonylphenol isotherms is two-stepped for both carbons. The introduction of acidic oxygen surface groups on the carbon enhances the specific nonylphenol adsorption by about 40%. This may be interpreted as being due to the fact that nonylphenol is hydrogen-bonded to the oxidized carbon surface by means of acidic groups. Thermal desorption experiments indicate that phenol is mainly physisorbed. Thermal desorption further confirms that nonylphenol is possibly bonded to oxygen surface groups by hydrogen bonds. Copyright 2001 Academic Press. 相似文献
8.
Different monometallic catalysts containing Fe, Co or Ni and a Fe–Co bimetallic catalyst have been prepared by impregnation of an activated carbon. The formation of subcarbonyl species during CO adsorption, as detected by the slow adsorption rate, was observed. From the CO adsorption isotherms, the possibility of a surface reorganization in the Co catalysts induced by the interaction with CO is deduced.
, Fe, Co Ni Fe–Co . CO . Co , CO.相似文献
9.
A. Guerrero-Ruiz C. Moreno-Castilla I. Rodríguez-Ramos 《Reaction Kinetics and Catalysis Letters》1985,27(2):283-286
The hydrogenolysis of n-butane on different carbon supported iron catalysts has been studied. Changes in activity, product distribution, apparent activation energy and frequency factor were found to be a function of particle size. This behavior is explained as a change in the reaction mechanism, which also leads to the isomerization of n-butane in the case of catalysts with higher dispersity.
- . , , . , - .相似文献
10.
Eva Castillejos Inmaculada Rodríguez-Ramos Maria Soria Sánchez Vicenta Muñoz Antonio Guerrero-Ruiz 《Adsorption》2011,17(3):483-488
This study illustrates the effect of the adsorbent porosity (activated carbon and high surface area graphite) on the phenol
adsorption kinetics. We have developed an experimental system where on line analysis of the solution is carried out by an
optic fiber probe introduced in the water solution and directly connected with the UV spectrometer. This experimental setup
permits to be more precise in determining kinetic parameters, considering that measurements are taken each 20 seconds. Our
results show that the choice of the particle diameter of the adsorbent is critical in the control of the adsorption process
kinetic, while the porosity of the carbon materials appears to be less relevant. 相似文献