Modelagem, simulação e otimização de um reator descontínuo heterogêneo para síntese enzimática de butanoato de etila catalisada por Novozym 435

Abstract

Ethyl butanoate is a relevant aroma compound in the chemical, pharmaceutical, food, and cosmetics industries. Its production via enzymatic esterification with heterogeneous biocatalysts, such as Novozym 435, is a promising alternative to improve yield and reduce the environmental impact of industrial processes. However, it still presents limitations due to the cost of biocatalysts and diffusional restrictions affecting the reaction rate. Thus, this study aimed to design a heterogeneous batch reactor through modeling, simulation, and optimization of ethyl butanoate synthesis using Novozym 435, focusing on process scale-up. Different mathematical models were proposed for the reactor, analyzing the relevance of internal and external diffusional limitations. The kinetic parameters and physical properties of the reaction system were obtained from the literature and empirical correlations. The reactor model with the best predictive capability, selected through an experimental validation test, was used in a sensitivity analysis to define process variables and performance and sustainability metrics. This served as the basis for the multi-objective optimization of the reactor operation, conducted for both batch and fed-batch configurations using butyric acid and ethanol, via Pareto front analysis. For scale-up, a constant power-to-volume ratio criterion was applied. Additionally, the costs of raw materials and the financial return of pilot-scale operation were estimated. The model considering internal diffusional limitations achieved a percentage error of 10.97% in estimating the reaction conversion profile. Simulations revealed that the initial substrate concentration and biocatalyst mass were the most relevant variables for achieving high productivity values. In the reactor optimization, the batch operation stood out, reaching an ester productivity of 1.13 g/h, a biocatalyst productivity of 44.41 kg p /kg c .h, and a product concentration of 1.95 M using 2.49 M butyric acid, 2.24 M ethanol, and 1.16% biocatalyst. During scale-up, the power-to- volume ratio remained at 173.70 W/m³, achieving an ester productivity of 9.26 kg/h in a volume of 82 L. The preliminary cost analysis reinforced the importance of maintaining biocatalyst stability over multiple operational cycles, focusing on process feasibility. Therefore, through simulation and optimization of the enzymatic synthesis of ethyl butanoate using Novozym 435, relevant data were obtained for designing a heterogeneous batch reactor, demonstrating higher production yields compared to the literature, as well as lower waste generation.