RESUMEN
Development of heterogeneous catalysts from biomass-derived activated carbon is a challenging task. Biomass-derived activated carbon possesses a large specific surface area, highly porous structure, and good thermal/chemical stability. Magnetic copper catalysts based on biomass-derived activated carbon exhibited good catalytic activity in base-free Chan-Lam coupling and oxidations. Herein, biomass-derived activated carbon was prepared by the carbonization of neem dead leaves (abundant waste biomass) followed by chemical activation with KOH. Such a porous carbon material was used as a low cost and highly efficient support material for the preparation of inexpensive and environmentally benign magnetic catalysts [Cu@KF-C/MFe2O4, M = Co, Cu, Ni, and Zn]. In addition, KF modification was done to impart basic character to the catalyst that can perform C-N coupling under base-free conditions. Initially, Brunauer-Emmett-Teller (BET) analysis of the synthesized catalysts was carried out, which indicated that Cu@KF-C/CoFe2O4 possess more surface area as well as pore volume, and so accounting for the highest activity among the other synthesized catalysts. Further, X-ray photoelectron spectroscopy (XPS) analysis was performed, which inferred that Cu@KF-C/CoFe2O4 contains most of the copper in reduced form, i.e., Cu(0), which is the active species responsible for better catalytic activity toward Chan-Lam coupling reactions as well as oxidation of alcohols and hydrocarbons. The physiochemical properties of the most active catalyst, Cu@KF-C/CoFe2O4, was examined by BET, XPS, Fourier transform infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA), field emission gun scanning electron microscopy (FEG-SEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray (EDX) mapping, energy dispersive X-ray (EDX), inductively coupled plasma atomic emission spectroscopy (ICP-AES), powder X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). Moreover, Cu@KF-C/CoFe2O4 shows excellent stability as well as reusability and could be easily separated with the help of an external magnet.
RESUMEN
Herein, well dispersed Ag-Cu NPs supported on modified graphene have been synthesized via a facile and rapid approach using sodium borohydride as a reducing agent under ambient conditions. Dicyandiamide is selected as an effective nitrogen source with TiO2 as an inorganic material to form two kinds of supports, labelled as TiO2-NGO and NTiO2-GO. Initially, the surface area analysis of these two support materials was carried out which indicated that N-doping of GO followed by anchoring with TiO2 has produced support material of larger surface area. Using both types of supports, ten nano-metal catalysts based on Ag and Cu were synthesized. Benefiting from the bimetallic synergistic effect and larger specific surface area of TiO2-NGO, Cu@Ag-TiO2-NGO is found to be a highly active and reusable catalyst out of other synthesized catalysts. It exhibits excellent catalytic activity for oxidation of alcohols and hydrocarbons as well as Chan-Lam coupling reactions. The nanocatalyst is intensively characterized by BET, SEM, HR-TEM, ICP-AES, EDX, CHN, FT-IR, TGA, XRD and XPS.