Esther N. Ponzi

Catalytic combustion of soot with a O2/NO mixture. KNO3/ZrO2 catalysts

Abstract Catalysts containing 0.25–20% KNO3 supported on ZrO2 have been studied for diesel soot combustion. The addition of KNO3 to ZrO2 support enhances its activity due to the increased contact between soot and catalyst and also because the KNO3 acts as catalyst. The combustion temperature has been measured for “loose” and “tight” contact, between soot and catalyst, and the difference was 10 K for KNO3(20)/ZrO2 catalyst. This finding is very important because under practical conditions the contact between soot and catalyst is poor and this contact resembles the contact denoted as “loose contact”.

Kinetics of carbon formation from CH4-H2 mixtures on nickel-alumina catalyst

Abstract The kinetics of carbon formation from CH4-H2 mixtures diluted with N2 on a steam reforming catalyst of Ni/Al2O3-CaO were studied in the temperature range 838–938 K at atmospheric pressure. It was found that the product formed deactivates the catalyst. Carbon deposition rates were interpretated using a kinetic equation with separable variables of the type r=r*a The reaction rate r* increased with increasing partial pressure of methane and decreased with increasing partial pressure of hydrogen. The experimental data were fitted by a Langmuir-Hinshelwood expression which takes into account competitive adsorption of hydrogen and hydrocarbon. The activity factor a was dependent on the time, temperature and methane and hydrogen partial pressures. Temperature programmed reactions of the coked catalysts with hydrogen allowed us to distinguish two types of deposits of different reactivities.

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.

ACIDITY OF H3PW12O40/SiO2 AND CATALYTIC ACTIVITY OF a -PINENE

The isomerization reaction in liquid phase of a -pinene in camphene catalyzed by tungstophosphoric acid supported on silica is studied. The catalyst is characterized with FT-IR and XRD to establish if the tungstophosphoric acid maintains the Keggin structure after being supported. The catalyst acidity exposed to different thermal treatments was determined by using FT-IR and TPD techniques of ammonia adsorbed. Two types of sites are distinguished, weak acid sites and strong acid sites. The weak acid sites concentration increases with the thermal treatment and can be responsible for the selectivity decrease in camphene by formation of products of higher molecular weight, while the strong acid sites concentration remains almost constant affecting in a lesser degree the obtention of monocyclic compounds

Study of the decomposition of supported nickel acetylacetonate by thermal techniques

The decomposition of supported nickel acetylacetonate (AcacNi) was studied by using thermal techniques to evaluate the nature of the calcination products. Thermogravimetric techniques used in this work indicated transformations occurring during preparation and calcination steps. Results demonstrated the important influence of support modifications upon the catalyst nature finally obtained.

Dimerization of α-pinene, Using Phosphotungstic Acid Supported on SiO 2 as Catalyst

Fil: Merino, Nora Andrea. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico San Luis. Instituto de Investigaciones En Tecnologia Quimica; Argentina

Zirconia-Supported Copper and KNO 3 Catalysts for Diesel Soot Combustion. Deactivation by Hydrotreatment and SO 2

Fil: Mosconi, Sandra Mariela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico San Luis. Instituto de Investigaciones en Tecnologia Quimica; Argentina

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.)