Agradecimentos: The authors thank the financial support from CAPES Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Abstract: Fischer-Tropsch synthesis (FTS) is a catalytic process to convert synthesis gas ( and CO) into fuels, as diesel and gasoline. It is an alternative to produce renewable fuels from raw materials such as biomass. Although a real catalytic FTS is not in equilibrium, the thermodynamic analysis...

Abstract: Fischer-Tropsch synthesis (FTS) is a catalytic process to convert synthesis gas ( and CO) into fuels, as diesel and gasoline. It is an alternative to produce renewable fuels from raw materials such as biomass. Although a real catalytic FTS is not in equilibrium, the thermodynamic analysis of FTS provides a comprehension of the chemical and phase equilibrium for products and reactants in this process. Therefore, this paper aimed to study the thermodynamic equilibrium of FTS using Gibbs energy minimization, allowing to calculate the equilibrium for an isotherm system. Cubic equations of state (CEOS) and Henry's law were employed to represent the non-ideality of the system. The method is formulated as an optimization problem, in which the Gibbs energy minimization is the objective function, and the roots from CEOS are selected by incorporating derivative constraints for each phase (vapor and liquid). Besides, the constraints regarded in this problem are the following: non-negative number of moles, mole balances, and inhibition of methane formation. We evaluated the equilibrium composition for different temperatures, pressures and synthesis gas inlet rate. The results show that CEOS embedded in an optimization problem, through nonlinear programming, is capable of predicting the phase and chemical equilibrium accurately, robustly, and with low computational effort, for a multiphase and multicomponent system. Furthermore, chemical equilibrium for FTS tends to yield light hydrocarbons as much as the rates of in the inlet increasing

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