This work deals with esterification of palm fatty acids to produce biodiesel in a batch reactor, using homogeneous acid catalysts, evaluating the effect of the alcohol used, presence of water, type and concentration of catalysts. Methanesulfonic and sulfuric acid were the best catalysts. Reaction with methanol showed greater yields. It was showed very clearly that the presence of water in the reaction medium showed a negative effect in the reaction velocity. Kinetic parameters were estimated and molecular modeling was performed. Protonation of the carboxylic moiety of the fatty acid were defined as rate determinant step for the reaction.

We have evaluated the influence of alcohol/fatty acid molar ratio (methanol or ethanol), water and catalyst concentrations and temperature by the esterification of palm fatty acids by heterogeneous acid catalysts (varying types, forms, and particle size). Polynaphtalene sulfonic acid (PSA) and niobium oxide (Nb 2 O 5 ) presented better performance than zeolite catalysts. Reaction with methanol presented higher conversion than with ethanol. The experimental design showed that the most relevant variable is the catalyst concentration and all interactions become important in process. A heterogeneous kinetic model was proposed and applied to experimental data. One of the models was adequate for methanol reaction, whereas the homogeneous model was more appropriate for ethanol reaction.

We present a new metal-organic framework (MOF) built from lanthanum and pyrazine-2,5-dicarboxylate (pyzdc) ions. This MOF, [La(pyzdc)1.5(H2O)2]⋅2 H2O, is microporous, with 1D channels that easily accommodate water molecules. Its framework is highly robust to dehydration/hydration cycles. Unusually for a MOF, it also features a high hydrothermal stability. This makes it an ideal candidate for air drying as well as for separating water/alcohol mixtures. The ability of the activated MOF to adsorb water selectively was evaluated by means of thermogravimetric analysis, powder and single-crystal X-ray diffraction and adsorption studies, indicating a maximum uptake of 1.2 mmol g(-1) MOF. These results are in agreement with the microporous structure, which permits only water molecules to enter the channels (alcohols, including methanol, are simply too large). Transient breakthrough simulations using water/methanol mixtures confirm that such mixtures can be separated cleanly using this new MOF.

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Biodiesel can be obtained from fatty acid raw materials through esterification. The reactivity of lauric, palmitic, stearic, oleic, and linoleic fatty acids with methanol using powdered niobic acid as a heterogeneous catalyst was investigated in this work, both experimentally (in a batch reactor) and theoretically. A 23 experimental design was used, with methanol/fatty acid molar ratio, catalyst concentration, and temperature as main factors. An empirical model demonstrated that temperature is the most important variable. Fourteen heterogeneous and 56 homogeneous‐like kinetic models were tested. A homogeneous‐like model considering zero order for all species and inhibition by water was the most adequate for experiments without catalyst. A homogeneous‐like model considering a second‐order reaction in relation to the fatty acid and no water inhibition was the most adequate for niobic acid catalyzed reaction. Molecular modeling confirmed the experimental results showing that the reactivity is directly related to the increase of unsaturated bonds and the reduction of carbon chain length. The polarity of the fatty acid is determinant in the reactivity. At the molecular level, reaction occurs between the HOMO orbital of methanol and LUMO orbitals of fatty acids and reactivity is higher when the energy difference between these orbitals is lower. Copyright © 2010 John Wiley & Sons, Ltd.

Recebido em 3/7/07; aceito em 31/10/07; publicado na web em 7/8/08 PRINCIPAL APPLICATIONS OF MICROWAVES IN PRODUCTION AND REFINING OF PETROLEUM. Microwave irradiation offers a clean, inexpensive, and convenient method of heating, which is an alternative way of introducing energy into chemical systems. In particular, applications of microwave irradiation technology for petroleum processing have been developed in the last twenty years. The main objective of this paper is to review the use of microwave irradiation technology as an alternative technique applied during petroleum refining and primary processing of petroleum fluids, presenting and discussing successful applications of this technology as a tool for petroleum emulsion separation and catalytic reactions normally found at hydrorefining plants.Keywords: microwaves; petroleum refining; primary processing. INTRODUÇÃOA maior parte das descobertas de reservas de petróleo realizadas no Brasil nos últimos anos tem sido de reservatórios de óleos pesados de baixo grau API (<20°), alta viscosidade e elevada acidez total. A produção e o processamento desses óleos pesados têm sido de alto interesse na Petrobras, que vem investindo em programas de pesquisa e desenvolvimento (i.e. PRAVAP, PROTER e PROPES) através do seu centro de pesquisa (CENPES) apontando desafios tecnológicos visando viabilizar a recuperação e a comercialização de óleos pesados.Dentre as melhorias tecnológicas a serem atingidas, destaca-se a necessidade de avanços nas unidades de dessalgação e de hidrorrefino envolvendo reações catalíticas da Petrobras. O processo de dessalgação visa reduzir a concentração de sais no petróleo antes do seu processamento nas unidades de destilação. Constitui uma operação indispensável que, em última análise, depende da separação das gotas de água por gravidade ou decantação. Para que as pequenas gotas de água se depositem, deve ocorrer coalescência de gotículas com formação de gotas suficientemente grandes, capazes de sedimentar com o auxílio da ação da gravidade, resultando na formação de uma camada líquida contínua, em um tempo razoavelmente curto. Para que a coalescência das pequenas gotas e o seu assentamento se processem mais fácil e rapidamente, estabelecem-se condições e empregam-se agentes capazes de favorecer a realização de tais objetivos. Essas condições variam desde o simples aquecimento, para diminuir a viscosidade do óleo, até o emprego de agentes químicos ou de aplicações de campos elétricos ou magnéticos, que promovem a coalescência das gotas de água salgada. Porém, as elevadas estabilidades das emulsões de óleos pesados assim como as altas viscosidades dificultam a separação da água emulsionada do óleo durante o processo de dessalgação, tornando deficientes os tratamentos empregados nesse processo. 1De modo análogo, as unidades de hidrorrefino existentes (hidrotratamento, hidrocraqueamento e hidrogenação) apresentam limitações quanto à capacidade de processamento de óleos pesados. Estes óleos são ricos em compostos de alto peso molecular e estruturas c...

This work studies toluene abatement from gaseous streams, using gamma-Al 2 O 3 supported palladium and platinum catalysts, titania and gamma-Al 2 O 3 supported vanadium oxide catalysts and ZnO/Al 2 O 3 supported copper oxide catalyst, characterized by textural and thermal analyses, X-ray diffraction and fluorescence. Noble metal catalysts have shown higher activity but lower selectivity toward total oxidation, with higher selectivity toward undesired products, like CO and benzene.