Modelagem matemática da reforma a vapor do etanol

Abstract

The historical global dependence on fossil fuels and the growing concern regarding the worsening of the greenhouse effect demand the diversification of the energy matrix towards more sustainable alternatives. In this scenario, hydrogen stands out as a promising energy vector due to its high energy density and the absence of greenhouse gas emissions during its use. Although current hydrogen production is dominated by fossil methane steam reforming, steam reforming of ethanol emerges as a new sustainable route. To make steam reforming of ethanol viable, supported catalysts, such as Nickel and Cobalt-based bimetallics, have shown great potential in inhibiting coke formation and increasing the H2 yield. However, the high chemical complexity of the ethanol molecule generates various parallel and consecutive reactions, which hinders the elucidation of the process kinetics. Based on this context, the present work proposed a reaction pathway and, from it, developed a phenomenological kinetic model capable of describing steam reforming of ethanol for hydrogen production. Using experimental screening data previously obtained by the research group, the study implemented and compared three different algorithms for the parametric fitting of the developed model: Non-Linear Least Squares, Simulated Annealing, and the Covariance Matrix Adaptation Evolution Strategy. Before the parametric fitting, a thermodynamic analysis proved that the experimental screening tests operated far from equilibrium. The fitting results highlighted the limitations of traditional deterministic optimizations, emphasizing the robustness of the evolutive algorithm in bypassing local minima and performing uncertainty estimation through confidence intervals. Although the preliminary data were limited, they proved to be sufficient to estimate the initial kinetic parameters. These estimates were for the 4Co4Ni, 8Co,