Biodiesel, known as a mixture of fatty acid ethyl/methyl esters, is seen as an alternative, ecofriendly, biodegradable and renewable non-fossil fuel. The use of heterogeneous catalysts for biodiesel synthesis can solve several problems associated with the homogeneous alkaline catalyzed-transesterification. Therefore, this work reports the evaluation of the commercial resin Amberlyst A26OH, a strong anion exchange resin, as a heterogeneous catalyst for the batch transesterification of refined palm olein with ethanol. It was studied the effects of the main operational parameters, considering the molar ratio of the reaction mixture (MRRM), namely the molar ratio of ethanol to olein taking into account only the ethanol added to the reaction system, and the total molar ratio (TMR), in this case considering also the amount of ethanol carried by the resin after its pretreatment. It was determined an optimal range of operational conditions by response surface methodology, guaranteeing conversion to ethyl esters higher than 96% with a catalyst amount corresponding to a range from 10.4 to 11.4% of the oil quantity, a temperature within the range of 55 to 60 ºC and a MRRM within the range from 3.5:1 to 6.0:1.

The modification of four extra virgin olive oils from different origins with refined soybean oil (SO), in the proportions of 0, 5, 10, 20 and 30% m/m, was studied using two approaches. First, the induction period (IP) was determined by Rancimat. In the second strategy, ion chromatography was used to quantify the formic and acetic acids, in their carboxylate forms (formate and acetate), present in the water contained in the measurement vessel of the Rancimat device, 21 h after the beginning of the induced oxidation of the samples. The content of the adulterant (SO) was linearly correlated with the IP (mean correlation coefficient (R) = 0.9858) and the concentration of the formate (mean R = 0.9979) and acetate (mean R = 0.9951). Also, it was observed that as the IP decreased and the formic acid and acetic acid concentrations increased, the monounsaturated fatty acids/polyunsaturated fatty acids ratio decreased.

Abstract Steady increase in prices of petroleum-based fuels and growing environmental concerns are boosting attention to alternative fuels. In this context, biodiesel has drawn attention as an alternative fuel, especially as a substitute to traditional diesel. Biodiesel is commonly produced from triacylglycerols and alcohol through transesterification reaction. Knowledge of equilibrium phase distribution of key components in transesterification systems is essential for a better understanding of the reaction pathway and for guiding the design and optimization of reactors and the products separation. This study reports experimental results and thermodynamic modeling of the liquid-liquid equilibrium of systems composed of soybean oil + monoacylglycerols + diacylglycerols + ethyl oleate + oleic acid + ethanol at 303.15 and 318.15 K. Experimental data were well correlated using NRTL, with a maximum deviation of 0.688%. As for UNIFAC, the deviations between predicted and experimental data ranged from 3.13 to 9.21%.

Abstract In this study, the liquid-liquid equilibrium (LLE) data of systems containing ethyl linoleate/oleate/palmitate/laurate, ethanol and glycerol at temperatures ranging from 323.15 to 353.15 K were used to evaluate the performance of the NRTL, UNIFAC, Cubic-Plus-Association Equation of State (CPA EoS), and artificial neural network (ANN) models. The systems evaluated correspond to the most important components formed at the end of the ethanolysis reaction of soybean, palm and coconut oils. The temperature range selected is very important for heterogeneous catalysts, especially for high-pressure systems. The accuracy of the models was evaluated by average global deviation. UNIFAC, UNIFAC-LLE and CPA EoS models showed lower accuracy with deviations of 10.1, 8.01 and 5.95%, respectively. In spite of this predictive limitation, these models show high extrapolation capability for the description of LLE behavior when few experimental data are available in the literature. The ANN model shows the best agreement between experimental and predicted data with an average deviation of 1.12%. In this regard, ANN is offered in this work as an alternative to equations of state and activity coefficient models to be used in a more reliable and less cumbersome way for process simulators of biodiesel production and separation equipment design.

O modelo proposto formaliza uma preocupação que se encontra cada vez com mais freqüência na literatura, a saber, a de que trabalhadores que não têm acesso a condições adequadas de capacitação, saúde e motivação tendem a aprender menos, reduzindo a velocidade de inovação em produtos e processos na firma. Na medida em que a competitividade internacional repousa crescentemente na inovação e/ou na imitação rápida de tecnologia, um nível baixo de desenvolvimento humano implicará oportunidades de crescimento perdidas. Assim, o modelo assume que, até certo valor crítico do salário real, aumentos de salário real produzem aumentos de competitividade e da taxa de crescimento com equilíbrio externo, tornando compatíveis o crescimento econômico e a distribuição da renda, inclusive num contexto de abertura e de intensa concorrência internacional.

The model formalizes a topic that the economic literature addresses with increasing frequency, namely that workers who have no access to adequate levels of education, health and motivation tend to learn more slowly and this in turn reduces the rate of innovation in products and processes in the firm. To the extent that international competitiveness increasingly relies on innovation and imitation of technology, a low level of human development will render lost opportunities for growth. Thus, the model assumes that - up to a certain critical level of the real wage - increases in real wages lead to a higher rate of growth consistent with balance-of-payments equilibrium, which makes compatible growth and income distribution even in contexts of external openness and intense international competition.

Elabora-se um modelo macroeconômico de curto prazo na tradição pós-keynesiana, no qual a oferta de crédito é endógena e o grau de endividamento das firmas é explicitamente modelado. Relacionam-se as condições de vigência dos regimes minskyanos de financiamento - hedge, especulativo ou Ponzi - não somente ao grau de endividamento e à taxa de juros, mas, inclusive, aos parâmetros da função investimento desejado da firmas e à propensão a poupar dos capitalistas produtivos e financeiros.

It is developed a short-run macromodel in the post-keynesian tradition, in which credit supply is endogenous and firms' debt position is explicitly modeled. The conditions under which each one of the minskyan financing regimes will prevail are related not only to the degree of indebtedness and the level of interest rate, but also to the parameters of firms' desired investment function and the saving propensity of productive and financial capitalists.

Elabora-se um modelo pós-keynesiano de utilização e crescimento da capacidade produtiva, no qual a oferta de moeda de crédito é endógena e o endividamento das firmas é explicitamente modelado. A taxa de juros é determinada pela aplicação de um mark-up sobre a taxa básica fixada pela autoridade monetária. O mark-up bancário varia intertemporalmente em conseqüência de mudanças no nível de atividade econômica, medido pela utilização da capacidade produtiva. Por seu turno, o grau de endividamento das firmas varia em função das taxas de lucro, de acumulação de capital físico e de juros. Em termos dinâmicos, mostra-se que é possível relacionar as condições de estabilidade do sistema formado pelas variáveis taxa de juros e grau de endividamento das firmas ao tipo de regime minskyano de financiamento hedge, especulativo ou Ponzi - prevalecente na economia.

It is developed a post-keynesian dynamic macromodel of utilization and growth of productive capacity, in which the supply of credit-money is endogenous and firms' debt position is explicitly modeled. The interest rate is set by banks as a markup over the base rate, which is exogenously determined by the monetary authority. Over time, the banking markup varies in response to changes in the level of economic activity, which is measured by the utilization of productive capacity. In turn, firms' debt position varies according to the rates of profit, capital accumulation and interest. Regarding dynamics, it is shown the possibility of relating the stability properties of a system having the interest rate and the debt position by firms as state variables to the type of minskyan regime hedge, speculative or Ponzi which prevails among firms.

Elabora-se um modelo macrodinâmico pós-keynesiano de utilização da capacidade, distribuição e inflação por conflito, no qual a oferta de moeda de crédito é endógena. A taxa nominal de juros é determinada pela aplicação de um mark-up sobre a taxa básica fixada pela autoridade monetária. Ao longo do tempo, o mark-up bancário varia com a taxa de lucro sobre o capital físico, enquanto a taxa básica varia com excessos de demanda que não são acomodáveis pela utilização da capacidade. São analisados os casos em que a demanda é suficiente ou não para gerar a plena utilização da capacidade.

It is developed a post-keynesian macrodynamic model of capacity utilization, distribution and conflict inflation, in which the supply of credit-money is endogenous. Nominal interest rate is determined by banks as a markup over the base rate, which is set by the monetary authority. Over time, banking markup varies with firms' profit rate on physical capital, while the base rate rises with any excess demand when capacity is fully utilized. The behavior of the economy is analyzed for the cases in which demand is or is not enough to ensure full capacity utilization.