Desenvolvimento e caracterização de catalisadores à base de óxidos de molibdênio e ferro suportados em sílica mesoporosa para a conversão do glicerol em solketal

Abstract

Biodiesel is a renewable alternative to fossil fuels gradually introduced into the Brazilian energy matrix. However, it faces challenges, including the need to diversify raw materials and sustainable management of glycerol, its main byproduct. The large amount of glycerol generated during biodiesel production demands solutions to enhance its economic value, which has encouraged the development of new catalysts to convert it into higher-value compounds, such as solketal, a promising fuel additive that improves performance and reduces emissions. This study aimed to develop and characterize iron and molybdenum oxide-based catalysts supported on mesoporous silica for application in the conversion of glycerol to solketal via acetalization. The catalyst synthesis included characterization techniques to evaluate structural and surface properties, such as X-ray diffraction (XRD), which revealed amorphous or crystalline structures depending on the synthesis methodology. Textural studies demonstrated the formation of a mixed mesoporous network with type IV isotherms, an important characteristic for catalytic processes. ICP-OES analyses confirmed that iron and molybdenum contents remained close to the theoretical values with negligible losses during synthesis. The thermal stability of the catalysts was assessed by TG-DTA, showing greater thermal stability in bimetallic materials compared to molybdenum monometallics. Additionally, XPS and Raman spectra confirmed the presence of molybdenum (VI) and iron (III) in the samples, while FTIR analysis using pyridine as a probe revealed the formation of Lewis and Brønsted acid sites, essential for efficient conversion of glycerol to solketal. Catalytic tests indicated that the synthesized catalysts are promising, with the best performance recorded for the C_FeMo2 catalyst, which achieved a glycerol conversion rate above 70% and solketal selectivity of 97% at room temperature (25±1 °C) after 90 minutes of reaction. These results highlight the potential of iron and molybdenum bimetallic catalysts as a sustainable alternative for adding value to glycerol, contributing to the economic and environmental feasibility of biodiesel production in Brazil.