The influence on selectivity of the aluminum content in the matrix of FCC catalysts

The influence that both the type of matrix and the interaction between zeolite and matrix have on the selectivity of FCC catalysts was studied by means of the conversion of cyclohexene at 300 ◦C on a large number of samples in which the matrix was changed. Silica/alumina matrices had 0, 12 and 25% of alumina, and catalysts were subjected to steaming of varying severity followed by acid extraction in some samples to remove extraframework aluminum species (EFAl). Resulting  catalysts were characterized by various techniques. It was confirmed that hydrogen transfer does not depend directly on the type of coordination of the aluminum atoms in the sample, but rather on the density of paired sites in the zeolite component. It was possible to define the selectivity of reaction pathways (SRP) as an index to describe the relative importance of the processes ofdesorption via hydride transfer to yield cyclohexane against retention of the cation cyclohexil via isomerization and further reaction. A high value of SRP would mean that a given catalyst has a lower ability to retain adsorbed species that can be subjected to additional reactions like, in this particular reaction, isomerization and further proton transfer to the catalyst surface, or cracking. The index was shown to increase whereas the relative amount of octahedral aluminum atoms decreased, a fact that can be associated to the formation of a new silica/alumina phase. Such phase would be formed by means of the reaction of aluminum extracted from the zeolite upon steaming and silica present in the matrix.Fil: de la Puente, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Falabella Sousa Aguiar, Eduardo. Centro de Pesquisas-Petrobras; BrasilFil: Figueiredo Costa, Alexandre. Centro de Pesquisas-Petrobras; BrasilFil: Sedran, Ulises Anselmo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Discrepancies in Determinations of the Ginzburg-Landau Parameter

Long-standing discrepancies within determinations of the Ginzburg-Landau parameter $\kappa$ from supercritical field measurements on superconducting microspheres are reexamined. The discrepancy in tin is shown to result from differing methods of analyses, whereas the discrepancy in indium is a consequence of significantly differing experimental results. The reanalyses however confirms the lower $\kappa$ determinations to within experimental uncertainties.Comment: submitted to Phys. Rev.

Pesquisa de determinantes genéticos em isolados bacterianos ambientais resistentes a antibióticos

Estágio realizado na Escola Superior de Biotecnologia-UCP e orientado pela Prof.ª Doutora Célia ManaiaTese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 200

Emissão de CO2 do solo sob cultivo de cana-de-açúcar em função da topografia

A variação temporal e espacial da emissão de CO2 solo-atmosfera é influenciada por inúmeros atributos do solo relacionados à produção de CO2 e à difusão do gás no solo. Ainda são escassos, entretanto, estudos visando compreender o efeito da topografia na variação da emissão deste gás, especialmente em áreas agrícolas da região tropical. O objetivo deste trabalho foi estudar a variação temporal e espacial da emissão de CO2 solo-atmosfera e sua relação com atributos do solo em área de cultivo de cana-de-açúcar sob diferentes formas de relevo e posições na encosta. A média da emissão de CO2 no período de sete meses de estudo variou entre 0,23 e 0,71; 0,27 e 0,90 e 0,31 e 0.80 g CO2 m-2 h- 1, nas posições côncava (Conc), encosta superior (BackS) e encosta inferior (FootS), respectivamente. A variação temporal da emissão em cada uma das áreas foi explicada por uma relação exponencial entre emissão de CO2 e temperatura do solo, e uma relação linear da emissão deste gás com a umidade do solo. O valor de Q10 foi 1,98 (± 0,34); 1,81 (± 0,49) e 1,71 (± 0,31) para Conc, BackS e FootS, respectivamente. Densidade do solo, macroporosidade, resistência do solo à penetração, agregação e conteúdo de carbono orgânico oxidável explicaram as variações observadas na emissão de CO2, especialmente quando se compara a posição côncava com a encosta superior. O efeito do relevo e da posição topográfica sobre a variação da emissão de CO2 do solo foi dependente da época de amostragem.The spatial and temporal variation of soil CO2 emission is influenced by several soil attributes related to CO2 production and its diffusion in the soil. However, few studies aiming to understand the effect of topography on the variability of CO2 emissions exist, especially for cropping areas of tropical regions. The objective of this study was to evaluate the spatial and temporal changes of soil CO2 emission and its relation to soil attributes in an area currently cropped with sugarcane under different relief forms and slope positions. Mean CO2 emissions in the studied period (seven months) varied between 0.23 and 0.71, 0.27 and 0.90, and 0.31 and 0.80 g m-2 h-1 of CO2 for concave (Conc), backslope (BackS) and footslope (FootS) positions, respectively. The temporal variability of CO2 emissions in each area was explained by an exponential relation between the CO2 emission and soil temperature and a linear relation between CO2 emission and soil water content. The Q10 values were 1.98 (± 0.34), 1.81 (± 0.49) and 1.71 (± 0.31) for Conc, BackS and FootS, respectively. Bulk density, macroporosity, penetration resistance, aggregation and oxidizable organic carbon content explain the changes in soil CO2 emission observed, especially when the Conc position was compared to BackS. The effect of relief form and topographic position on soil CO2 emission variation was dependent on the time of measurement

Soybean seed protein concentration is limited by nitrogen supply in tropical and subtropical environments in Brazil

Soybean production contributes to ca. 60% of global plant-based protein used for food and feed. Brazil is the largest soybean producer and exporter, with 60% from tropical and 40% from subtropical environments. Nitrogen (N) can play an essential role in the storage of proteins in seeds; thus, it could be a key factor in increasing the quantity and quality of seeds in high-yielding soybean crops. Unlike in temperate environments, there is a gap of knowledge on whether soybean grown under tropical and subtropical climates are limited by N-fertilization to sustain the seed yield increase without detriments in seed protein concentration. This study aimed to evaluate the effect of N-fertilization on soybean seed yield, protein, and oil concentrations in tropical and subtropical environments in Brazil, thus contributing to agricultural intensification procedures and food security studies. Two levels of N-fertilization (0 and 1000 ka/ha) were tested across 11 tropical or subtropical environments. The range of latitudes explored here was from 12º S to 29º S, representing the major soybean-producing regions in Brazil either under rainfed or irrigated conditions. We found that seed yield responses to N-fertilization were significant (in some environments under rainfed with an average increase of 7%) or not significant (in irrigated). Seed protein increases due to improved N-fertilization (on average 4% for irrigated and 12% for rainfed conditions) were much higher than previous reports from temperate environments. Regardless of N supply and water deficit, there was a trend of seed protein and oil concentration increasing toward lower latitudes