Abstract
This study drew its aspiration from the rapid reduction of fossil fuel reserves for fuel production, their negative influence on the global environment, and their role in climate change which has raised many concerns. Consequently, bioderived molecules have attracted much attention in the past decades because they can be used as substitutes for fossil fuels. In addition, these bioderived compounds, such as furfural and its derivatives have opened up new possibilities for the manufacturing of value-added chemicals with commercial applications, offering sustainable alternatives to fossil fuels. This work aims to synthesize, characterize, and evaluate the catalytic activity of the simple ABO3 and ABB’O3 multicationic inorganic perovskites as heterogeneous catalysts for the conversion of furfural to 𝛽-methoxy-(s)-2-furanethanol and transesterification of cooking oil to methyl ester (biodiesel), in an attempt to contribute to the mitigation of climate change. The investigation involved the optimization of the heterogeneous catalysts in one-pot catalytic transfer hydrogenation and etherification reactions to monitor the selectivity and yield.
These simple and multicationic inorganic perovskite catalysts were successfully synthesized using the sol-gel method where citric acid was used as a chelating agent. The structural composition and morphology of these simple and multicationic inorganic perovskites were characterized using a suite of thermal (thermogravimetric analysis (TGA)), spectroscopic (Fourier transform infrared spectroscopy (FTIR)), structural (Powder X-ray diffraction (PXRD)) and microscopic techniques (Scanning electron microscope (SEM) and high-resolution transmission microscope (HRTEM)). Among the five perovskite catalysts synthesized, LaNiO3, LaNi0.75Mo0.25O3, LaNi0.5Mo0.5O3, LaNi0.25Mo0.75O3, and LaMoO3, the latter had the lowest surface area (6.1 m2/g) and the highest activity confirming that surface area cannot be employed as a factor for improving catalytic activity. There was no correlation between the distribution of Mo/Ni and the surface area of the prepared perovskites. SEM micrographs showed that surface of the all catalysts contains irregularly shaped particles, while HRTEM micrographs revealed that all catalysts have clusters of particles. PXRD diffractograms for LaNiO3 and LaMoO3 matched very well with simulated PXRD patterns, but not for multicationic perovskites. FTIR spectra confirmed the metal-ligand vibration bands of the perovskites. Lastly, the TGA curve showed excellent stability of the catalysts.
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We investigated the effects of Ni/Mo ratio, catalyst loading, temperatures, and solvents on one-pot catalytic transfer hydrogenation and etherification of furfural to produce 𝛽-methoxy-(s)-2-furanethanol, a fine chemical intermediary in the production of value-added chemicals. The results revealed that LaMoO3 catalyst perovskite gave excellent conversion activity of 83%, whereas LaNiO3 catalyst gave the lowest percentage conversion of 37%. Interestingly, there was an obvious trend from low to moderate yield when the Mo concentration was increased, as follows: LaNiO3, LaNi0.75Mo0.25O3, LaNi0.5Mo0.5O3, LaNi0.25Mo0.75O3, and LaMoO3, and in both catalytic systems, 100% selectivity was achieved towards the desired product.
The transesterification of waste cooking oil (WCO) as starting material in methyl ester (biodiesel) production employing methanol solvent and hexane as a co-solvent was investigated using LaMoO3 perovskite catalyst. With a 20:1 methanol-to-oil mole ratio and a 1:1 hexane-to-oil mole ratio, we successfully synthesized fatty acid methyl ester (biodiesel). The influence of temperature, reaction time, catalyst amount, and hexane as a co-solvent on the transesterification of waste cooking oil was investigated. We found that using hexane as a co-solvent in the reaction improved the solubility of oil and methanol. As a result, the highest biodiesel yield of 88.7 % was achieved using hexane as a co-solvent. Overall, the simple and multicationic inorganic perovskites (LaNi1-xMoxO3±δ) as heterogeneous catalysts were employed in the conversion of furfural and waste cooking oil to produce value-added chemicals.