Síntese de catalisadores do tipo LaNixFe1-xO3 como precursores catalíticos para reação oxidação parcial do metano

Nickel-bases catalysts have been used in several reform reactions, such as in the partial oxidation of methane to obtain H2 or syngas (H2 + CO). High levels of conversion are usually obtained using this family of catalysts, however, their deactivation resulting from carbon deposition still remains a challenge. Different approaches have been tested aiming at minimizing this difficulty, including the production of perovskites and related structures using modern synthesis methods capable of producing low cost materials with controlled microstructural characteristics at industrial scale. To establish grounds for comparison, in the present study LaNixFe1-xO3 (x=0, 0.3 or 0.7) perovskites were prepared following the Pechini method and by microwave assisted self-combustion. All samples were sub sequently calcined at 900 °C to obtain the target phase. The resulting ceramic powders were characterized by thermogravimetric analysis, infrared spectroscopy, X ray diffraction, specific area and temperature programmed reduction tests. Calcined samples were also used in the partial oxidation reaction of methane to evaluate the level of conversion, selectivity and carbon deposition. The results showed that the calcined samples were crystalline and the target phase was formed regardless of the synthesis method. According to results obtained by Rietveld refinement, we observed the formation of 70.0% of LaNi0.3Fe0.7O3 and 30.0% of La2O3 for samples LN3F7-900- P, LN3F7-900-M and 41,6% of LaNi0.7Fe0.3O3, 30.7% of La2NiO4 and 27.7% of La2O3 for samples LN7F3-900-P and LN7F3-900-M.Temperature-programmed profiles of the LaNiO3 sample revealed the presence of a peak around 510 °C, whereas the LaFeO3 sample depicted a peak above 1000°C. The highest l evel of methane conversion was obtained for LaNiO3 synthesized by the Pechini method. Overall, catalysts prepared by the Pechini method depicted better conversion levels compared to those produced by microwave assisted self-combustion

Incorporação de resíduo cerâmico para prevenção da retrogressão da resistência de cimentos de poços de petróleo submetidos à injeção de vapor

Steam injection is the most used thermal recovery method of oil nowadays because of the high degree of development of the technique that allows high recovery factors. However, injection of superheated steam into the reservoir affects the entire structure of the well, including the cemented layer that presents a retrogression of compressive strength and increases the permeability due to formation of more crystalline and denser phases at temperatures above 110 °C. These changes result in failures in the cement that favor the entrance of formation fluids into the annulus space resulting in unsafe operations and restrictions in the economic life of the well. But the strength retrogression can be prevented by partial replacement of cement by silica-based materials that reduce the CaO/SiO2 ratio of cement slurries changing the trajectory of the reactions, converting those deleterious phases in phases with satisfactory mechanical strength and permeability. The aim of this study was to evaluate the behavior of a ceramic waste material rich in silica in partial and total substitution of a mineral additive used to fight the strength retrogression of cement slurries subjected to high temperatures. The evaluation was made by compression, X-ray diffraction (XRD) and thermogravimetry (TG/DTG). The samples were submitted to a cycle of low temperature (38 °C) for 28 days and a cycle of low temperature followed by exposure to 280 ºC and 1000 psi by 3 days. The results showed that slurries with additions of up to 30% of the waste material are not enough to prevent the strength retrogression, while slurries with additions of the waste material combined with silica flour in various proportions produced hydrated products of low Ca/Si ratios that maintained the compressive strength at satisfactory levels

A recepção da criança com deficiência intelectual ao texto literário na educação infantil

The focus of this thesis is children's reception to literary texts starting from literary livelihood in an inclusive literary context, looking for the possible evidences that are present in the construction as reader/hearing of literature. Based on a study case, we search the ways of participation of a child (girl) with intellectual deficiency in situations of offering and reception of literary texts, looking for the understanding and explication of some aspects of her processing and the building up of an initial reader. The data were taken starting from observations in moments of reading and story-telling in the period from November to December/2008 and May to June/2009 in a public school of children education, in Natal- Brazil, in which there was a registered student showing intellectual deficiency associated to Down syndrome. As research tools we used: field diary, interview scripts and video recordings. The analyses were based on research from Amarilha (2001, 2006a, 2006b), Bettelheim (2007), Coelho (2008), Iser (1996), Jauss (1979, 1994), Luria (1990a, 1990b), Vygotsky (1991, 1993), Wallon (2007, 2008) amongst others. The research showed that although expressing little verbalization and limited levels of attention, body attitudes, movements and talks of the child under investigation, denounced engagement and rendition to the sonority of the texts shared. These data gives us traces that, under a mediating action, the child with intellectual limitation can turn into a reader/hearing subject of literature, developing a sensitive and a selective attitude towards the literary text. Amongst other aspects, we identified that (1) a conception of deficiency present through the school that recognizes his/her potential of developing and learning (2) the situation of sharing, that favours a relation with the texts through the other, and (3) the relevance of orality providing the semantic paths that help the child in the building up of meaning, presenting themselves as fundamental to her/his viewing of the literary text, and, therefore, the formation of the reader. Thus, recognizing her/his capacity and possibilities, we think it is important to guarantee to the child with intellectual deficiency, a space towards interaction with the fictional text in which the child can learn and live its ludic and interactive character, to enjoy its hearing abilities, benefiting, then, from the aesthetic experience lived, mainly, in collective situations mediated through the more experient reader and shared with her/his different pairs. The research shows yet that, looking after conditions that guarantee a comfortable environment to the story hearings in the classrooms that focus on children education, being aware of a selection and the prosody of stories, the didactic contract, the attention to individual reactions, enlarge the possibility of any child deficient or not to enjoy her/himself as reader/ hearing subject of literature, engaged in its richness and magic

Avaliação da remoção de sulfeto de hidrogênio do gás natural em uma coluna de absorção

Natural gas, although basically composed by light hydrocarbons, also presents in its composition gaseous contaminants such as CO2 (carbon dioxide) and H2S (hydrogen sulfide). Hydrogen sulfide, which commonly occurs in oil and gas exploration and production activities, besides being among the gases that are responsible by the acid rain and greenhouse effect, can also cause serious harm to health, leading even to death, and damages to oil and natural gas pipelines. Therefore, the removal of hydrogen sulfide will significantly reduce operational costs and will result in oil with best quality to be sent to refinery, thereby resulting in economical, environmental, and social benefits. These factors highlight the need for the development and improvement of hydrogen sulfide sequestrating agents to be used in the oil industry. Nowadays there are several procedures for hydrogen sulfide removal from natural gas used by the petroleum industry. However, they produce derivatives of amines that are harmful to the distillation towers, form insoluble precipitates that cause pipe clogging and produce wastes of high environmental impact. Therefore, the obtaining of a stable system, in inorganic or organic reaction media, that is able to remove hydrogen sulfide without forming by-products that affect the quality and costs of natural gas processing, transport and distribution is of great importance. In this context, the evaluation of the kinetics of H2S removal is a valuable procedure for the treatment of natural gas and disposal of the byproducts generated by the process. This evaluation was made in an absorption column packed with Raschig ring, where natural gas with H2S passes through a stagnant solution, being the contaminant absorbed by it. The content of H2S in natural gas in column output was monitored by an H2S analyzer. The comparison between the obtained curves and the study of the involved reactions have not only allowed to determine the efficiency and mass transfer controlling step of the involved processes but also make possible to effect a more detailed kinetic study and evaluate the commercial potential of each reagent