Development of Sustainable Heterogeneous Catalysts for the Photocatalytic Treatment of Effluents

Optimization of Biodiesel Production Process Using MoO3 Catalysts and Residual Oil: A Comprehensive Experimental 23 Study

The study aimed to utilize MoO3 catalysts, produced on a pilot scale via combustion reaction, to produce biodiesel from residual oil. Optimization of the process was conducted using a 23 experimental design. Structural characterization of the catalysts was performed through X-ray diffraction, fluorescence, Raman spectroscopy, and particle size distribution analyses. At the same time, thermal properties were examined via thermogravimetry and differential thermal analysis. Catalytic performance was assessed following process optimization. α-MoO3 exhibited a monophasic structure with orthorhombic phase, whereas α/h-MoO3 showed a biphasic structure. α-MoO3 had a larger crystallite size and higher crystallinity, with thermal stability observed up to certain temperatures. X-ray fluorescence confirmed molybdenum oxide predominance in the catalysts, with traces of iron oxide. Particle size distribution analyses revealed polymodal distributions attributed to structural differences. Both catalysts demonstrated activity under all conditions tested, with ester conversions ranging from 93% to 99%. The single-phase catalyst had a long life cycle and was reusable for six biodiesel production cycles. The experimental design proved to be predictive and significant, with the type of catalyst being the most influential variable. Optimal conditions included α-MoO3 catalyst, oil/alcohol ratio of 1/15, and a reaction time of 60 min, resulting in high biodiesel conversion rates and showcasing the viability of MoO3 catalysts in residual oil biodiesel production.

A Brief Review of MoO3 and MoO3-Based Materials and Recent Technological Applications in Gas Sensors, Lithium-Ion Batteries, Adsorption, and Photocatalysis

Molybdenum trioxide is an abundant natural, low-cost, and environmentally friendly material that has gained considerable attention from many researchers in a variety of high-impact applications. It is an attractive inorganic oxide that has been widely studied because of its layered structure, which results in intercalation ability through tetrahedral/octahedral holes and extension channels and leads to superior charge transfer. Shape-related properties such as high specific capacities, the presence of exposed active sites on the oxygen-rich structure, and its natural tendency to oxygen vacancy that leads to a high ionic conductivity are also attractive to technological applications. Due to its chemistry with multiple valence states, high thermal and chemical stability, high reduction potential, and electrochemical activity, many studies have focused on the development of molybdenum oxide-based systems in the last few years. Thus, this article aims to briefly review the latest advances in technological applications of MoO3 and MoO3-based materials in gas sensors, lithium-ion batteries, and water pollution treatment using adsorption and photocatalysis techniques, presenting the most relevant and new information on heterostructures, metal doping, and non-stoichiometric MoO3-x.

From Disposal to Reuse: Production of Sustainable Fatty Acid Alkyl Esters Derived from Residual Oil Using a Biphasic Magnetic Catalyst

The development of technologies to promote residual oil reuse has been encouraged, aiming to reduce the environmental impact and promote sustainability. In this study, a biphasic magnetic catalyst with composition equal to ZnO-Ni0.5Zn0.5Fe2O4 was synthesized and applied to the fatty acid alkyl ester (FAAE) production from residual oil. The ZnO-Ni0.5Zn0.5Fe2O4 catalyst was synthesized by combustion reaction and characterized by X-ray diffraction (XRD), textural analysis, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetry, particle size distribution, scanning electron microscopy, magnetic measurements, quantification of acidic sites by TPD-NH3, and catalytic tests. The efficiency of catalyst synthesis was evaluated by XRD, FTIR, and Raman spectroscopy experiments. Granulometric analysis and SEM images confirmed the presence of the agglomerates and particles with a wide size range. The catalyst presented soft magnetic behavior, with high saturation magnetization. Additionally, the catalytic activity of the ZnO-Ni0.5Zn0.5Fe2O4 system showed an average conversion of 73% for the methyl route. The results indicate that the reuse of residual oil is feasible for FAAE production, contributing to sustainable fuel development. Moreover, it allows the reintroduction of waste oil into the biodiesel production chain, reducing cost after process optimization.