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As the demand for sustainable energy sources expands, the production of biodiesel has attracted great attention. The development of effective and ecologically friendly biodiesel catalysts has become an urgent need. In this context, the goal of this study is to develop a composite solid catalyst with enhanced efficiency, reusability, and reduced environmental impact. For that, eco-friendly, and reusable composite solid catalysts have been designed by impregnating different amounts of zinc aluminate into a zeolite matrix (ZnAl2O4@Zeolite). Structural and morphological characterizations confirmed the successful impregnation of zinc aluminate into the zeolite porous structure. Catalytic experiments revealed that the catalyst containing 15 wt% ZnAl2O4 showed the highest conversion activity of fatty acid methyl esters (FAME) of 99% under optimized reaction conditions, including 8 wt% catalyst, a molar ratio of 10:1 methanol to oil, a temperature of 100 °C, and 3 h of reaction time. The developed catalyst demonstrated high thermal and chemical stability, maintaining good catalytic activity even after five cycles. Furthermore, the produced biodiesel quality assessment has demonstrated good properties in compliance with the criteria of the American Society for Testing and Materials ASTM-D6751 and the European Standard EN14214. Overall, the findings of this study could have a significant impact on the commercial production of biodiesel by offering an efficient and environmentally friendly reusable catalyst, ultimately reducing the cost of biodiesel production. [ABSTRACT FROM AUTHOR]

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Recently, green hydrogen production via solar thermochemical water splitting (STWS) as a clean and sustainable method is becoming a subject of interest to many researchers. Great efforts are being made to develop materials for STWS with suitable operating conditions, low cost, and good cycling stability. In this context, the study of mixed cobalt and nickel oxides with the general formula Co 3- x Ni x O 4 (0 ≤ x ≤ 1) was carried out, where four mixed metal oxides Co 2.75 Ni 0.25 O 4 , Co 2.5 Ni 0.5 O 4 , Co 2.25 Ni 0.75 O 4 , and Co 2 NiO 4 have been successfully synthesized through the sol-gel method modified Pechini route. The structural investigation demonstrated that pure spinel structures were obtained for 0 ≤ x ≤ 0.75. A deep study was carried out with the main goal of finding the best phase that provides low redox temperature. Interesting reduction temperatures for all the compositions have been found, and the lowest values of 675 and 710 °C have been reported for Co 2.25 Ni 0.75 O 4 and Co 2.5 Ni 0.5 O 4 , respectively. The thermal cycling results of this latest material using TGA measurement have proven attractive cycling stability of which the complete reoxidation of the samples was achieved. In addition, thermodynamic analysis of a reduction step was performed and good agreement of the theoretical reduction temperature of Co 2.25 Ni 0.75 O 4 with the experimental one has been found., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)