Catalysts studies

It is also important to point out that pure cobalt oxide, alone or finely dispersed in Si02 (i.e. Co-Si02, Co-Si02-l and Co-Si02-2 in Table 1), zeolite HY, fullerene (i.e. C q/C-,0 80/20) is at least as effective as the reduced oxides for the production of nanotubules in our experimental conditions. In fact, the catalysts studied in this work are also active if the hydrogenation step is not performed. This important point, is presently being investigated in our laboratory in order to elucidate the nature of the active catalyst (probably a metal carbide) for the production of nanotubules. 

A short survey of information on formation, structure, and some properties of palladium and nickel hydrides (including the alloys with group IB metals) is necessary before proceeding to the discussion of the catalytic behavior of these hydrides in various reactions of hydrogen on their surface. Knowledge of these metal-hydrogen systems is certainly helpful in the appreciation, whether the effective catalyst studied is a hydride rather than a metal, and in consequence is to be treated in a different way in a discussion of its catalytic activity. 

Strictly a-solid solution of hydrogen in a metal catalyst studied. 

Application of a Temperature-Programmed Desorption Technique to Catalyst Studies... 

A Pilot Plant Reactor-Surface Analysis System for Catalyst Studies... 

A comparison of the qualitative features of the FRC spectra for the catalyst studied show a clear distinction between Rh/S102 and Rh/T102, In terms of their reversible H2-chemlsorptlon. Suprlslngly, little difference was observed between normal and SMSI-Rh/T102. "Normal" Rh/T102 behaved quite differently from Rh/S102, In spite of their similarities In total, l.e., static, chemisorption behavior. 

All of the supported bimetallic catalysts studied show a sharp drop in methanatlon activity when the Ru/M ratio falls below four. 

Figure 5.27 A recycle-loop reactor for catalyst studies.

XAS has widely been used for catalyst studies [308], and also in relation to polymers and catalyst residues. 

Catalyst Study. Equivalent amounts of p-phenylenebis(4,4-dimethyl-2-oxazol1n-5-one ) (2) and Jeffamine D-2000 (polyoxypropylenediamine from Texaco Chemical Co., amine equiv. weight 1023) were mixed with 5 mole % of the desired catalyst. The stirred mixture was heated at 240°C under argon for 30 minutes, then an additional 1.5 hours under vacuum (<1 torr) and collected. The amount of cyclization was estimated by 1H-NMR in CDC 13 by comparison of the Integrated intensities of the absorptions due to the gem-dimethyl substituents. These absorptions appeared at 1.39 ppm in the cyclic form and at 1.73 ppm in the open-chain form of the polymer (see Scheme 4). Results are listed in Table I. 

Other metal oxide catalysts studied for the SCR-NH3 reaction include iron, copper, chromium and manganese oxides supported on various oxides, introduced into zeolite cavities or added to pillared-type clays. Copper catalysts and copper-nickel catalysts, in particular, show some advantages when NO—N02 mixtures are present in the feed and S02 is absent [31b], such as in the case of nitric acid plant tail emissions. The mechanism of NO reduction over copper- and manganese-based catalysts is different from that over vanadia—titania based catalysts. Scheme 1.1 reports the proposed mechanism of SCR-NH3 over Cu-alumina catalysts [31b],... 

The initial screening of the resin catalysts was done in a batch reactor at supercritical for butene-1 conditions of temperature 155 °C, pressure of 1000 psig and at molar ratio of 1-butene water of 5.5. The reaction was stopped after predetermined period of time and the products analyzed. It was found that under the standard reaction conditions, for all of the catalysts studied, a constant concentration in the sec-butanol concentration was achieved within a 1-2 hour reaction time. Using only the linear section of the concentration-time plot, the one hour result was used to evaluate the catalyst activity, which was normalized as mmol of SBA/ per proton/ per hour (a), as mmol of product/ per gram of dry catalyst/ per hour (b) and mmol of product/ per ml of wet catalyst/ per hour (c). 

Enantioselective hydrogenation of 2,3-butanedione and 3,4-hexanedione has been studied over different type of supported Pt catalysts (Pt/Al203, Pt/Si02, Pt/MCM-41) in the presence of cinchonidine (CD). Kinetic results confirmed that (i) 2,3-butanedione is more reactive than 3,4-hexanedione over all catalysts studied and (ii) both substrates have a strong poisoning effect. The kinetic results confirmed also that CD concentration close to 10"3 M is necessary to achieve both high reaction rate and enantioselectivity in the range of 55-65 %. NMR results confirmed that substrate-modifier interaction takes also place in the liquid phase. 

The ability of STM to image at the atomic scale is particularly exemplified by the two other chapters in the book. Thornton and Pang discuss the identification of point defects at Ti02 surfaces, a material that has played an important role in model catalyst studies to date. Point defects have been suggested to be responsible for much of the activity at oxide surfaces and the ability to identify these features and track their reactions with such species as oxygen and water represents a major advance in our ability to explore surface reactions. Meanwhile, Baddeley and Richardson concentrate on the effects of chirality at surfaces, and on the important field of surface chirality and its effects on adsorption, in a chapter that touches on one of the fundamental questions in the whole of science - the origins of life itself ... 

Barnett et al. [AIChE J., 7 (211), 1961] have studied the catalytic dehydrogenation of cyclohexane to benzene over a platinum-on-alumina catalyst. A 4 to 1 mole ratio of hydrogen to cyclohexane was used to minimize carbon formation on the catalyst. Studies were made in an isothermal, continuous flow reactor. The results of one run on 0.32 cm diameter catalyst pellets are given below. 

High MW fraction in EPDM ought to contribute favorably to the vulcanizate tensile properties ( ). The following preliminary observations were gathered to examine whether difference in. tensile strength of samples prepared with various catalysts studied was due primarily to the difference in MWD of the terpolymers. ... 

Lebreton, R. Brunet, S. Perot, G., et al., Influence of sulfur containing compounds on high temperature coke formation on hydrotreating catalyst. Studies in Surface Science and Catalysis, 2000. 130 p. 2861. 

Virtually all catalysts studied by the ESR technique are composed of small crystallites or an amorphous material. For such samples, the spectrum is the envelope of the spectra from all possible orientations of the radical with respect to the external magnetic field. In order to obtain meaningful data it must be possible to extract the principal g and hyperfine values from these polycrystalline spectra. A relatively straightforward analysis of the spectra can be made provided the resolution is adequate. 

Ming, J., Koizumi, N., Ozaki, T., and Yamada, M. 2001. Adsorption properties of cobalt and cobalt-manganese catalysts studied by in-situ diffuse reflectance FTIR using CO and CO+H2 as probes. Appl. Catal. A Gen. 209 59-70. 

Rothaemel, M., Hanssen, K.F., Blekkan, E.A., Schanke, D., and Holmen, A. 1997. The effect of water on cobalt Fischer-Tropsch catalysts studied by steady-state isotopic transient kinetic analysis (SSITKA). Catal. Today 38 79-84. 

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