Resumo em português Um éster de cadeia longa foi sintetizado pela transesterificação do palmitato de metila com álcoois de cadeia longa usando óxido de magnésio como catalisador. Esses foram preparados pela decomposição térmica de diferentes precursores, buscando estabelecer relações entre propriedades estruturais e atividades. Temperatura e quantidade de catalisador foram variados para se avaliar o rendimento do éster em função do precursor utilizado na preparação do óxido. Resumo em inglês A long chain ester was prepared by transesterification of methyl palmitate with long chain alcohol using magnesium oxide as catalyst prepared by thermal decomposition of different precursors with the intention of establish relations among structural properties and activities. Temperature and catalyst amounts were modified in order to evaluate the yield of the ester in function the precursors used in preparation of the oxide.
Produção de biodiesel através de transesterificação in situ de sementes de girassol via catálise homogênea e heterogênea/ Biodiesel production by in situ transesterification of sunflower seeds by homogeneous and heterogeneous catalysis
Resumo em inglês The objective of this work is to show the results of the in situ transesterification of sunflower seed oil with methanol on basic homogeneous and heterogeneous catalysis for the production of biodiesel. In homogeneous catalysis, the activity of KOH and K2CO3 were evaluated using the same oil:methanol ratio of 1:90. KOH showed to be more active than K2CO3, leading to total conversion in biodiesel after 1h reaction time. In the heterogeneous catalysis the activity of K2CO3/ (mais) Al2O3 was comparable to the activity of K2CO3 bulk: 53.0 and 66.6% resp. The properties of samples of biodiesel produced by homogeneous and heterogeneous catalysis were evaluated and are in accordance with the recommended fuel properties.
Síntese e caracterização de perovskitas LaNi(1-x)Co xO3 como precursores de catalisadores para a conversão do metano a gás de síntese pela reforma com CO2/ Preparation and characterization of LaNi(1-x)Co xO3 perovskites as catalyst precursors for synthesis gas generation by CO2 reforming of methane
Resumo em inglês LaNiO3 perovskite was modified by partial substitution of nickel by cobalt in order to increase the stability and resistance to carbon deposition during the methane CO2 reforming. The results showed that a suitable combination of precipitation and calcination steps resulted in oxides with the desired structure and with important properties for application in heterogeneous catalysis. The partial substitution of Ni by Co resulted in lower rates of conversion of both the rea (mais) ctants, but the catalyst stability was highly increased. The LaNi0.3Co0.7O3 catalyst, calcined at 800 ºC, was the most active under the reaction conditions.
Resumo em inglês Products resulting from the ethoxylation of hydroxylated compounds, especially water and ethanol, are of great commercial importance. This work presents several aspects concerning the catalytic reactions of ethylene oxide, a chemical substance used in the production of a wide variety of products. Mechanisms of ethoxylation, distribution of products, formation of undesired by-products and perspectives for new processes using heterogeneous catalysis are also reviewed and discussed.
Resumo em inglês The broad variety of hydrogenation methods of polydienes is presented. Homogeneous and heterogeneous catalysis are reviewed emphasizing also hydrogen transfer from donor compounds.
Resumo em inglês Many industrial processes produce effluents with a wide variety of xenobiotic organic pollutants, which cannot be efficiently degraded by conventional biological treatments. Thus, the development of new technologies to eliminate these refractory compounds in water has become very imperative in order to assure the quality of this important resource. Ozonation is a very promising process for the treatment of wastewaters containing non-easily removable organic compounds. The (mais) present work aims at highlighting new methods of enhancing the efficiency of ozone towards the removal organic pollutants in aqueous solution. Special attention is given to catalytic ozonation processes contemplating homo- and heterogeneous catalysis, their activity and mechanisms. Recent results and future prospects about the application of these processes to real effluents are also evaluated.
Resumo em inglês This study explores the similarities between solid and liquid acid catalysts highlighting the advantages and the main challenges of heterogeneous catalytic processes. We describe the main developments in technical procedures like selection of compounds and reaction models involved in: increasing acidity, characterization of solid acidity and in coke formation.
Resumo em inglês A CPC (Compound Parabolic Concentrator) reactor was projected and constructed aiming to promote the degradation of the organic matter present in considerable volumes of aqueous effluents, under the action of solar radiation. The essays were done using a model effluent which consists of a mixture of fragments of a sodium salt of lignosulphonic acid possessing a mean molecular weigth of 52,000 Daltons, and a real effluent, from a chip board industry. The volume of effluent (mais) in each test was about 50 L. The tests involved heterogeneous (TiO2 P25 Degussa and formulations made from the association of TiO2 with a photosensitiser), and homogeneous (thermal and photochemical Fenton reactions) catalysis of the effluents. The results demonstrate the viability of application of this kind of reactor even when the load of organic pollutants is high.
Resumo em inglês The synthesis, characterization and some applications in catalysis of pillared clays are described at an introductory level. The use of x-ray diffraction, surface area measurements, thermal analysis, IR spectrophotometry and solid-state NMR in the characterization of pillared clays is briefly discussed. Pillarization followed by doping or introduction of metal clusters into clays could lead to the development of selective heterogeneous catalysts.
Adaptação de forno de microondas doméstico para realização de reações de transesterificação sob refluxo e catálise por argilas/ Adapting a domestic microwave oven transesterification reactions for under reflux and clay catalysis
Resumo em inglês The microwave oven became an important source of heating for many laboratory procedures including accelerating organic reactions. Reactions that require long reflux times can sometimes be carried out in a few hours or minutes in a conventional microwave oven. However, longer reflux times can be troublesome since domestic microwave ovens are not prepared for these harsh conditions. This technical note presents our finding on heterogeneous catalysis transesterification reac (mais) tions between b-keto-esters and carbohydrate derivatives under heating or microwave irradiation using an adapted domestic microwave oven.
A dialética dos campos sociais na interpretação da problemática ambiental: uma análise crítica a partir de diferentes leituras sobre os problemas ambientais/ The dialectics of social fields in the interpretation of the environmental problematic: a critical analysis based on different readings of environmental problems
Resumo em português A problemática ambiental constitui, atualmente, um importante espaço catalisador e produtor de valores regulatórios da vida humana e não-humana na biosfera terrestre. Porém, o que faz com que esta temática adquira tamanha envergadura em relação à sua identificação como problema social importante? A hipótese lançada aqui é a de que por trás desta difusa sensibilidade ambiental encontra-se em processo a configuração de um campo ambiental relativamente estru (mais) turado, no qual se busca, cada vez mais, a legitimidade para tratar das discussões sobre tudo aquilo que diz respeito ao meio ambiente. Neste sentido, tal espaço de lutas simbólicas tende a concentrar confrontos em torno do reconhecimento de certas ações e modos de pensamento, sendo que o que está colocado em jogo, neste caso, são as próprias percepções acerca do que seja o meio ambiente e, em contrapartida, as relações ontológicas construídas entre seres humanos e natureza. Com isto, a paulatina estruturação de um campo ambiental - este último funcionando como um amplo, dinâmico, instável e heterogêneo espaço de debate e de ação - tende a fazer com que determinados conceitos e práticas possam naturalizar-se e, concomitantemente, serem reconhecidas como "ambientalmente corretas". Em suma, a constituição deste domínio prático/discursivo irá concentrar os agentes e suas disputas sobre que saberes, comportamentos e procedimentos deveriam ser instituídos como sendo os mais "adequados" do ponto de vista ambiental. Entretanto, nesta perspectiva, o que seria visto (e adotado) como ambientalmente "correto" ou "adequado" está, desde já, em disputa. Resumo em inglês At present, the environmental question constitutes an important space of catalysis and production of regulatory values of human and non-human life in the earth's biosphere. However, what makes this theme to attain such magnitude in relation to its identification as an important social problem? The hypothesis herein presented is that behind this diffuse environmental sensibility there is the ongoing configuration of a relatively structured environmental field, where legiti (mais) macy is increasingly sought to address discussions dealing with all aspects and issues pertaining to the environment. In this sense, such space of symbolic struggles tends to concentrate confrontations around the acknowledgement of certain actions and ways of thinking; what is at stake, in this case, are the very perceptions about what environment is and, conversely, the ontological relations built between human beings and nature. Thus, the gradual structuring of an environmental field - the latter working as a wide, dynamic, unstable, and heterogeneous space for debate and action - tends to make certain concepts and practices to become natural and, at the same time, to be acknowledged as "environmentally correct". In a nutshell, the constitution of this practical/discursive domain will focus the agents and their disputes onto what types of knowledge, behaviors, and procedures should be instituted as the most "appropriate" from an environmental standpoint. However, under this perspective, what would be seen (and adopted) as environmentally "correct" or "appropriate" is, as of now, the object of dispute.
Resumo em inglês In the last 25 years the research in catalysis has passed from heterogeneous processes mainly applied to petrochemical industries to homogeneous processes applied to fine chemicals and green chemistry. In this context the Brazilian Chemical Society (SBQ) is playing an important role in the organization of this interdisciplinary area involving researches from different fields of physical sciences.