ABSTRACT Different basic materials, such as K-L zeolite, K-Al2O3, K-Mg/Al mixed oxide and MgO, were used as supports of Pt-catalysts for the dry reforming of methane (DR) reaction. The effects of the distribution of basic strength in the support on the metal-support properties and catalyst performance were evaluated. The density of strong and the total basic sites decreased as follows: MgO>K(Mg-Al) >K-Al2O3>K-L. The total basic sites decrease from 214 to 23 µmol CO2. g-1, for MgO and KL, respectively. Pt catalysts supported on materials with high density of strong basic sites such as MgO were the most adequate for the DR reaction. An increase in the dehydrogenation velocity of 12.1 to 25.2 mol h-1 g-1 was observed between Pt/KL and Pt/MgO, which indicates a higher metallic dispersion of the latter catalyst. With respect to the DR reaction, both catalysts have a similar CO2 conversion, but the CH4 conversion and the H2/CO ratio increase from 71.1 to 83.0 % and 0.5 to 0.73, respectively. The best catalytic behaviour of Pt/MgO would be related with the good interaction between the metal and the basic support. The methane conversion and the H2/CO ratios obtained by DR reaction correlate quite well with the basicity of the different catalysts.

Structured materials composed of α-Al2O3 spheres covered with a porous and thin layer of MgAl2O4 or ZnAl2O4 were obtained. The innovative coating method developed consists in the formation of a precursor gel of MgAl2O4 or ZnAl2O4 by citrate-nitrate combustion method. The alumina spheres are submerged in this gel and then submitted to a drying process in vacuum and to calcinations with N2 and N2/O2. SEM results showed that a very rough and porous layer uniformly covers the spheres. The thickness of the layer reaches the maximum value of 16 µm in the sample coated with two layers of ZnAl2O4. XRD results confirmed the MgAl2O4 or ZnAl2O4 spinel formation in the layered material. The structured materials were used as Pt catalysts supports, showing a good catalytic activity in the n-butane dehydrogenation reaction.

This work studies the catalytic performance in dry reforming of Ru catalysts supported on γ-Al2O3 promoted with Na, K, Mg, Ca and Ba. The supports and the catalysts were characterized and tested in the reaction of CH4 reforming with CO2. Ru/Al2O3-Na and Ru/Al2O3-K catalysts showed higher conversions and better H2/CO molar ratios. This catalytic behavior would be related with the higher metallic dispersions and with the basicity of the support. When the reduction time in H2 was shortened, a decrease of the conversions for all the catalysts, except for Ru/Al2O3-Na, was observed. This phenomenon would not be due to the thermal effect but to the reduction time.

En este trabajo se estudia el comportamiento catalítico en reformado seco de catalizadores de Ru soportados sobre alúminas con agregado de Na, K, Mg, Ca o Ba. Los soportes y catalizadores fueron caracterizados y se analizó el comportamiento catalítico en la reacción de reformado de CH4 con CO2. Los catalizadores Ru/Al2O3-Na y Ru/Al2O3-K ofrecen mayores conversiones y mejores relaciones H2/CO, asunto que está relacionado con la dispersión metálica y con la basicidad del soporte. La disminución del tiempo de reducción previa del catalizador en H2, produce una disminución de las conversiones de CO2 y CH4 para todos los catalizadores excepto para el Ru/Al2O3-Na. Este fenómeno no sería debido al efecto térmico sino al tiempo de reducción propiamente dicho.

We studied hantavirus seroprevalence and virus variability in rodent populations in Diego Gaynor, northwest of Buenos Aires province, Argentina. Rodent samplings were conducted in railroads and cropfield borders in March and July 1999, September and December 2000, and March 2001. Antibody detection was performed by an enzyme link immunosorbent assay (ELISA), using the recombinant nucleoprotein of Andes (AND) virus as antigen. Tissue samples were taken from positive antibody individuals in order to confirm the presence of hantavirus genomic material and to identify virus genotypes. Akodon azarae was the most abundant species, followed by Oligoryzomys flavescens, while Calomys laucha and C. musculinus were rarely caught. We found a rate of seroprevalence of 9.3% for a total sample of 291 A. azarae and 13.5% for 37 O. flavescens. After molecular analyses of hantavirus, we confirmed the presence of hantavirus genomic material in 16 individuals with ELISA (+) results and two individuals with ELISA (-). Four amplimers for each species were sequenced and compared to the corresponding sequences of representative hantaviruses. We identified the AND Cent Lec from three O. flavescens, and the Pergamino virus from four A. azarae and from one O. flavescens. A. azarae males had higher seroprevalence than females, and heavier individuals showed higher seroprevalence than lighter ones. We did not find seroprevalence differences according to sex in O. flavescens, although this result may have been produced by the low sample size. The lowest seroprevalence was found in a period of high rodent density, when juveniles prevailed in the population. We found higher seroprevalences than those detected in previous studies for other localities of central Argentina where cases of hantavirus pulmonary syndrome (HPS) have been reported. The presence of AND Cent Lec virus in rodent populations of the study area, which is responsible of HPS cases in central Argentina, suggests that human populations are at risk of HPS disease, although there were not reported cases of this disease until today.