Chromatographic Measurement of Hydrogen Adsorption on Supported Metallic Catalysts

Roca, François Figueras; Mourgues, L. De; Trambouze, Yves

doi:10.1093/chromsci/6.3.161

Cited by 15 publications

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“…Comparison of the Thomson results with experimental entropies for ammonia clusters (Figure 7) shows a sharp disagreement for all ions. For instance, at cluster size 5, the experimental results are more negative than predicted ones by [5][6][7][8][9][10][11][12][13][14][15] eu; furthermore, theory and experiment seem to diverge as cluster size increases. Clearly the experimental results suggest more ordered cluster ions than can be accounted for by the Thomson equation.…”

Section: Comparison With Experimental Resultsmentioning

confidence: 99%

“…At this time, special regard should be paid to the role of surface hydroxyl groups on metal oxides, because they are held tenaciously on the surface even after degassing the sample at higher temperatures.1-4 Actually, some cases are known where the presence of optimum amounts of water enhance a catalytic activity of metal oxides. 5,6 Therefore, it will be useful in the characterization of solid surfaces to understand the adsorption of organic molecules on metal oxide surfaces as a function of the surface hydroxyl content of the sample.…”

Section: Introductionmentioning

confidence: 99%

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Thomson equation revisited in light of ion-clustering experiments

Holland¹,

Castleman²

1982

J. Phys. Chem.

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there are initial concentration gradients in both phases at the beginning of the ripple experiments. We, therefore, first solved eq 10, 12,13, 17, 20, and 21, respectively, for a flat interface starting with a fresh interface at t = 0, i.e., Ci(x,y,0) = C0 and C2(x,y,0) = 0. We then assumed that quantities like C^Cy.t), which now depend on time and location because of evaporation, do not change significantly on the time scale of ripples and calculated the perturbed concentration profile by an appropriate linearization procedure. So we determined Ct(1) from the equation [see (12)] dCi(1)(x,y,0 _ Dll 77 + 77 |c1(1)(x,y,t) -v{x,y,t)^-Cxm{y,te) (22) \ dx2 dy2 4J oy where te is the time of observation.For all practical situations, the initial concentration gradients lead to negligible deviations from the equilibrium results presented above. This can easily be understood: according to ( 14), perturbations of solute concentration decay on a length scale ^ * 1 1~( 1/ )1/2 while Cif0)(t0) changes on a length scale of ^)1/2. Hence, initial gradients are of little importance for ( ^)1/2 » 1 which holds for all experimental situations. ConclusionsOur main result is expression 19 for the dilational index e. We have shown that diffusion in the liquid dominates evporation as the mechanism for restoring gradients in solute concentration. But even diffusion is of minor importance: Lucassen and Hansen5 6have shown that it is already difficult to determine the diffusion coefficient from ripple experiments. Hence, our results suggest that it will be almost impossible to get reliable data on evaporation from studies of the ripple spectrum.Similar equations can be applied to ripples at a liquidliquid interface when discussing transfer of surfactant between the liquids. In that case, the additional terms in the expression for the dilational modulus will probably be more important, and the effect may be larger.

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Section: Comparison With Experimental Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thomson equation revisited in light of ion-clustering experiments

Holland¹,

Castleman²

1982

J. Phys. Chem.

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“…Volumetric and gravimetric gas adsorption methods are commonly employed for chemisorption measurements, but their use is limited for high-temperature measurement due to decomposition of chemisorbed adsorbate. To avoid this, use of gas chromatographic procedures has been made successfully by many investigators (Grubner, 1962;Hughes, et al, 1962; Piringer and Tataru, 1964; Roca et al, 1968).…”

Section: Surface Area Measurement Under Reaction Conditionsmentioning

confidence: 99%

Applications of Gas Chromatography in Catalysis

Choudhary¹,

Doraiswamy²

1971

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Applications ofGas Chromatography in Catalysis L. K. Doraiswamy was born on May 18, 1927, and received his MS in chemical engineering from the University of Wisconsin in 1950 and his PhD in chemical engineering from the same University in 1952. After working for a year with R. L. Carlisle Chemical and Manufacturing Company, Brooklyn, Dr. Doraiswamy joined the Chemical Engineering Division of National Chemical Laboratory at Poona, India, in 195j. At present, he is Head, Division of Chemical Engineering and Process Development. He has published about 50 papers, mostly in chemical reaction engineering and chemical engineering thermodynamics, and has been associated with the development of several processes at the National Chemical Laboratory which are now in operation in India. Vasant R. Choudhary, born Nov. 28, 19j.j, is a research fellow at the National Chemical Laboratory, Poona, India. He received his bachelor of science (1965) and master of science (1967) degrees in chemistry from the University of Poona in First Class. His fields of interest are kinetics and heterogeneous catalysis.

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“…The specific surface area of the oxide catalysts was obtained from fourpoint nitrogen isotherms obtained with a modified Perkin-Elmer Sorptometer. The surface area of platinum in the PVAI2O3 catalysts was determined by both flow (Roca et al, 1968) and static (Spenadel and Boudart, 1960) hydrogen chemisorption techniques.…”

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confidence: 99%

Lanthanum Lead Manganite Catalyst for Carbon Monoxide and Propylene Oxidation

Katz¹,

Croat²,

Laukonis³

1975

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The activity of single crystal lanthanum lead manganite (La0.7Pbo.3Mn03) was compared to Pt/Al203, Co304, and CuO under conditions important to automotive emission control. In simulated automotive exhaust ambients, the observed order of activity of fresh catalyts toward both CO and C3H6 oxidation was found in general to be: Pt/Al203 > Co304 > La0.7Pbo.3Mn03 > CuO. Pt/Al203 remained the most active of the materials throughout tests In which the susceptibility of catalysts to various modes of deactivation, namely, high temperature exposure, S02 poisoning and reaction with -203, was measured. The results for the single crystal manganite catalyst showed it to be susceptible to thermal deactivation but resistant to S02 poisoning. Manganite was also found to react extensively with • 203 at 1000°C suggesting potential difficulties with supported catalysts.Basic differences were found between the properties of single crystal and polycrystalline forms of La0.7Pbo.3Mn03. They showed different oxidation kinetics and the specific catalytic activity of the single crystals was found to be roughly 100 times higher than the polycrystalline materials. The data suggest that the enhanced activity might be due to the presence of small quantities of Pt. In addition to single crystal LaojPbo.sMnOs and Pt/ AI2O3, two base metal catalysts, C03O4 and CuO, were included in the study to broaden the scope by which the activity of manganite catalysts could be assessed. The activity of polycrystalline Lao^Pbo.sMnOs materials was also investigated. Experimental SectionMaterials. A total of four manganite samples were investigated. These included two samples of crushed Lao.7Pbo.3Mn03 single crystals (37-250 µ ) which were grown from a lead borate flux in a Pt crucible and subsequently etched 3-5 min in hot (80°C) 20% nitric acid (Voorhoeve et al., 1973). The two samples were prepared at different laboratories. The first (sample A) was obtained from J. P. Remeika (Bell Telephone Laboratories), and the second (sample B) was prepared by the authors. The remaining samples were polycrystalline. Sample C was prepared from coprecipitated hydroxides which were calcined in A1203 crucibles for 24 hr at 600°C and etched 5 min in hot (50°C) 15% nitric acid (Voorhoeve et al., 1973). Testing was conducted on particles in the 149-250-µ range. Samples A-C were found by X-ray diffraction analysis to be single phase material with well defined perovskite structures.

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Chromatographic Measurement of Hydrogen Adsorption on Supported Metallic Catalysts

Cited by 15 publications

References 0 publications

Thomson equation revisited in light of ion-clustering experiments

Thomson equation revisited in light of ion-clustering experiments

Applications of Gas Chromatography in Catalysis

Lanthanum Lead Manganite Catalyst for Carbon Monoxide and Propylene Oxidation

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