Abstract
Abstract In the present study, a facile solvothermal method was used for the synthesis of silicotungstic acid (HSiW) immobilized on Ce-based metal organic framework (Ce-BDC) and embedded in Zr-based metal-organic framework (UiO-66(Zr)) composite catalyst, namely, Ce-BDC@HSiW@UiO-66 for the production of biodiesel through green fatty acid esterification. The obtained hybrids were characterized by various characterization technologies, including Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 physisorption, X-ray photoelectron spectroscopy, and temperature-programmed desorption of NH3 (NH3-TPD) analysis. The characterization analyses showed that the hybrids have been successfully synthesized. Also, the volume and pore size of UiO-66(Zr) were changed by introducing HSiW@Ce-BDC, and the resulting Ce-BDC@HSiW@UiO-66 possessed the mesoporous structure and relatively high surface area. Simultaneously, the NH3-TPD analysis of Ce-BDC@HSiW@UiO-66 reveals that the acid strength was increased in comparison with HSiW@Ce-BDC. In addition, the composite Ce-BDC@HSiW@UiO-66 demonstrated high catalytic activity, and the oleic acid esterification gave 81.5% conversion at optimum conditions of 0.2 g catalysts, 1:30 oleic acid to methanol molar ratio at 130°C for 4 h. More interestingly, after six recycling cycles, the reduction in the conversion rate was only 4.6%, indicating that Ce-BDC@HSiW@UiO-66 has excellent reusability. Our study provides an effective approach to synthesize multifunctional hybrids for green biofuel production.
Highlights
With the rapid growth of world population and the development of industrialization, the growing consumption of energy, especially fossil fuels, is increasing [1]
The production of biodiesel by esterification process is an interesting choice via using low-cost feedstock with high fatty acid contents, which may be the best solution for cost reduction [5]
The absence of peak at 745 cm−1 was believed to be the O–H vibrations in the H2BDC ligand. These results indicate the presence of the organic ligands terephthalic acid in the synthesized samples
Summary
With the rapid growth of world population and the development of industrialization, the growing consumption of energy, especially fossil fuels, is increasing [1]. The production of biodiesel by esterification process is an interesting choice via using low-cost feedstock with high fatty acid contents, which may be the best solution for cost reduction [5]. Composite catalyst for green fatty acid esterification 185 corrosion of the vessel with large amount of wastewater from neutralization steps, and the impossibility of reuse [7]. Heteropolyacids may require an appropriate support with high surface area and chemical stability for corresponding impregnation or anchoring [18,19]. We prepared a novel Ce-BDC@HSiW@UiO-66 composite synthesized by the simple solvothermal method. The synthesized Ce-BDC acted as the supporting material, and the silicotungstic acid was immobilized on Ce-BDC to form HSiW@Ce-BDC. The hybrids were used for esterification of green fatty acid. All chemicals were of analytical grade and used without further purification, unless otherwise noted
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