María G. González

Partial oxidation of methane to synthesis gas. Behaviour of different Ni supported catalysts

The behaviour of Ni supported catalysts, obtained using Ni(NO3)2 and Ni-acetylacetonate as precursor compounds, is analyzed. It is observed that initial activities and selectivities are similar for both systems, but the stability differs significantly. The systems show different carbon structures and sintering rates, depending on the precursor compound employed.

Γ-Al2O3-Supported XMo6 Anderson Heteropolyoxomolybdates: Adsorption Studies for X = TeVI, AlIII, CoIII, CrIII and NiII by DR Spectroscopy and TPR Analysis

The support–overlayer adsorptive interactions, generated when solutions of Anderson heteropolyoxomolybdates were supported as a monolayer on γ-Al2O3 by means of the equilibrium adsorption method, were studied by XRD analysis, DR spectroscopy, electron microscopy (SEM–EDAX) and TPR methods. The adsorption isotherms and corresponding adsorption parameters (number of active sites and adsorption constants) of the γ-Al2O3-supported ammonium heptamolybdate were obtained and discussed. The following sequence of adsorption strength was suggested: CoMo6 > CrMo6 > TeMo6 ~ AlMo6 > NiMo6. The effectiveness of the TPR technique as a tool for elucidating interaction effects was clearly demonstrated. The formation of a γ-Al2O3-supported Te–Mo mixed valence oxide appears to provide new and interesting catalytic possibilities.

Studies on H2S Adsorption and Carbon Deposition Over Mo-Ni/Al2O3 Catalysts

The influence of molybdenum on the CO2 reforming of methane, simultaneous sulphur poisoning and carbon formation over alumina-supported Ni catalysts was studied. A series of Ni/Al2O3 catalysts modified by Mo was prepared to enable the effect of molybdenum content on H2S adsorption and the catalytic properties of the solids to be studied. The atomic Mo/Ni ratio in such catalysts varied in the range 0.01–1.00 while the Ni content was maintained constant at 3.3%. The catalysts were characterized by TPR, hydrogen adsorption and TEM methods. The H2S adsorption capacities of the catalysts were determined at 923 K employing a mixture consisting of 50 ppm H2S in a hydrogen stream. The results obtained indicate that the Mo promoter had a very favourable influence on the sulphur resistance of the Ni-based catalyst and led to a reduction in the rate of carbon deposition and the formation of graphitic species over the same.

Study of different support and precursor compounds for supported nickel oxyreforming catalysts

Preparation and characterization of different nickel catalysts for the oxyreforming reaction was studied in this work. The catalysts were prepared by impregnating two different precursor compounds (nickel nitrate and nickel acetylacetonate) into α-Al2O3 and α-Al2O3 modified by a layer of aluminium oxide. This modification led to an increment in the dispersion of the active phase and to a more active catalyst.

Cobalt Supported on Zirconia. Selective Catalytic Reduction of NO Using Propane as Reducing Agent

Fil: Lick, Ileana Daniela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico la Plata. Centro de Investigacion y Desarrollo En Ciencias Aplicadas; Argentina

Kinetics and Mechanisms of Catalytic Deactivation: Continuous Reactor

Abstract Some continuous reactor models have been analyzed to find out which of them can be used to distinguish the deactivation mechanism (series, parallel, or impurity) of a catalytic system when the results are expressed as relative reaction rate related to the dimensionless concentration at the outlet. The models analyzed were: plug flow (PF), stirred tank (ST), plug flow with axial dispersion (ADR), and a combined model of the last two (ST-ADR). The combined model (ST-ADR) proved to be the only model which could effectively determine the deactivation mechanism using this type of representation. One of the advantages of the ST-ADR over the diffusion reactor is that the kinetic information of the system without deactivation can be obtained at high flowrates. In this way, the experimental results can be processed using the plug-flow model to determine the kinetics of the main reaction.

START-UP TIME IN TUBULAR REACTORS WITH AXIAL DISPERSION

Abstract In the modeling of nonideal reactors the axial dispersion model is one of the most used (Butt, 1980). Boundary conditions for a tubular reactor with axial dispersion were extensively analyzed (Danckwerts, 1953, Wehner and Wilhelm, 1965, Van Cauwen-berghe, 1966, Choi and Perlmutter, 1976, Deckwer and Mahlmann, 1976) Similarly, the steady state behaviour of the reactor when simple or complex reactions take place was also studied by several authors (Deckwer et al. 1972, Wan and Ziegler, 1973). However, the transient behaviour was only analyzed for simple kinetics expressions (Fan and Ahn, 1963, Sawinsky artd Hunek, 1977, Godslave and Chang, 1980) In the present work, the time necessary to reach the steady state or start-up time is determined for single and complex reversible reactions. The analysis presented is also valid in case there is a change in feed concentration (feed upset, etc.)