Abstract
The effect of a second porous SiO2 shell in the activity and selectivity of the Fe3O4@SiO2–Pt catalyst in the hydrodenitrogenation of indole is reported. The double Fe3O4@SiO2–Pt@SiO2 structure was prepared by coating Fe3O4 nanoparticles with tetraethyl orthosilicate (TEOS) with a further impregnation of 1.0 wt.% of Pt on the (3-aminopropyl)triethoxysilane functionalized Fe3O4@SiO2 structures. The second porous SiO2 shell, obtained by using a hexadecyltrimethylammonium bromide (CTAB) template, covered the Fe3O4@SiO2–Pt catalyst with a well-defined and narrow pore-sized distribution. The full characterization by TEM, inductively coupled plasma-optical emission spectroscopy (ICP-OES), XRD, and N2 adsorption isotherm at 77 K and vibrating sample magnetometry (VSM) of the catalysts indicates homogeneous core@shell structures with a controlled nano-size of metallic Pt. A significant effect of the double SiO2 shell in the catalytic performance was demonstrated by both a higher activity to eliminate the nitrogen atom of the indole molecule present in model liquid fuel and the improvement of the catalytic stability reaching four consecutive reaction cycles with only a slight conversion level decrease.
Highlights
The presence of polyaromatic and cyclic compounds in diesel negatively affects the environment and reduces the quality of diesel, as well as lowers the cetane number, which is indicative of the ease of ignition thereof
Fe3 O4 –NPs were dispersed in a mixture of ethanol, water, and ammonia, and after that tetraethyl orthosilicate (TEOS, Merck® ) was slowly added to the dispersion under stirring for 6 h
The SiO2 coating generated by the Stöber method did not modify the distribution or increase the average size of the Pt–NPs on the surface of the material
Summary
The presence of polyaromatic and cyclic compounds in diesel negatively affects the environment and reduces the quality of diesel, as well as lowers the cetane number, which is indicative of the ease of ignition thereof. Taking into account the different elements that are considered contaminants in the refining processes of the petrochemical industry, within hydrotreatment we can distinguish hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodeoxygenation (HDO), hydrodemetalization (HDM), and hydrodearomatization (HDA). The HDS has been extensively studied because sulfur is a pollutant that is present in higher proportions in crude oils of lower quality and as an important catalyst deactivator because of poisoning [5,6,7,8,9]. Removal of nitrogen from organic compounds present in various fractions of crudes is harder than sulfur removal, which leads to the importance of the study
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