Abstract
Nanosized copper silicates with three different structural morphology (amorphous, nanotubes and MEL) were prepared using different synthesis methods. The physico-chemical properties of copper silicates were characterized by XRD, FT-IR, SEM, HRTEM, N2-physisorption, XPS and H2-TPR techniques. The results indicated that the preparation conditions affect reduction behavior and textural properties of nanosized copper silicates. Hydrothermal synthesis method yielded chrysocolla-like CuSiO3 nanotubes, which possessed high surface area and pore volume with easy reducibility. The catalytic performances of synthesized copper silicate nanostructures were evaluated for dehydrogenation of methanol. It was found that dehydrogenation activity is depended on the structural properties of copper silicates. Highest activity was observed for copper silicates with nanotube morphology. Catalytic dehydrogenation activity of copper silicates was also related to presence of more number of Cu-O-Si species, easy reducibility and Lewis acid centers. The CuSiO3 nanotubes sample also exhibited good stability under investigated reaction conditions that deactivation was not detected for 48 h.
Highlights
Nanosized copper silicates with three different structural morphology were prepared using different synthesis methods
The FT-IR spectrum for CuSil-NT sample (Fig. 2) displayed two bands at 3620 cm−1 and 673 cm−1, which could be attributed to the stretching and bending vibrations of hydroxyl groups attached to the copper atoms
The enhanced catalytic dehydrogenation activity of CuSil-NT catalyst could be due to the fact that CuSil-NT possessed greater number of surface Lewis acid sites and interactive [Cu-O-Si] species, which are reducible
Summary
Nanosized copper silicates with three different structural morphology (amorphous, nanotubes and MEL) were prepared using different synthesis methods. The reaction can progress in several ways, resulting in either the formation of methyl formate (HCOOCH3) and formaldehyde (HCHO) or the decomposition of CH3OH into COx and H2 Interest in the latter process is associated with the remarkable progress in the H2 fuel cells research, which has taken place in recent decades[2]. It was indicated in the literature that preliminary reduction treatment of copper catalysts (to convert oxidized Cu to Cu metal species) is necessary to obtain higher yields of methyl formate[11]. Some authors reported that metallic copper (Cu°) but oxidized copper species (Cu2+ and Cu+) helpful for the formation of methyl formate in methanol dehydrogenation[12]. In order to investigate the role of structural and textural properties of copper silicates nanomaterials in selectivity to methyl formate, three different nanostructured copper silicates with different structure (amorphous, MEL structure and nanotube) were synthesized. A careful structural and textural characterization of catalysts has been undertaken to determine the nature, as well as the role of the active sites responsible for dehydrogenation of methanol
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