Highly
stable gold nanoparticles immobilized on the surface of
amine-functionalized nanocomposite microspheres possessing a magnetite
(Fe
3
O
4
) nanoparticle core and a silica (SiO
2
) shell (Au/SiO
2
-shell/Fe
3
O
4
-core) were prepared. These gold nanocomposite catalysts were tested
for 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA) reduction in aqueous
solution in the temperature range 293–323 K and in the presence
of aqueous NaBH
4
reducing agent. The magnetically recyclable
gold catalyst showed high stability (∼3 months), efficient
recyclability (up to 10 cycles), and high activity (∼100% conversion
within 225 s, ∼700 ppm 4-NP or 2-NA). The pseudo-first-order
apparent reaction rate constants (
k
) of 4-NP and
2-NA reduction were 7.5 × 10
–3
and 4.1 ×
10
–3
s
–1
, respectively, and with
an apparent catalytic activity of 4.48 × 10
–8
kmol/(m
3
s).
Mesostructured carbon−silica nanocomposites with hexagonally ordered pore channels have been synthesized from sucrose as a sustainable carbon source via a rotary evaporation induced self-assembly (REISA) method. Phosphate functionalization was performed on the resultant nanocomposite to obtain a strong acid catalyst with bimodal pores. The synthesized materials were thoroughly characterized by X-ray diffraction (XRD); Fourier transform infrared spectroscopy (FTIR); N 2 physisorption; field emission scanning electron microscopy (FESEM); acid titration; energy-dispersive X-ray (EDX) mapping; high-resolution transmission electron microscopy (HRTEM); X-ray photoelectron spectroscopy (XPS); 13 C, 29 Si, and 31 P solid-state magic angle spinning nuclear magnetic resonance (MAS NMR); and thermogravimetric analysis (TGA) techniques. The well-ordered mesopores facilitate the entrance and fast transport of molecules during reaction. The catalytic efficiency of the materials was tested for solventless glycerol carbonylation with urea and glycerol esterification involving acetic acid. The efficient catalytic performance could be associated to the higher acidity and better communicating hierarchically organized porous channels. The catalyst showed good reusability for both the reactions without any significant leaching. Therefore, the specified methodology here provides a useful pathway for the eco-friendly and effective preparation of hierarchically mesoporous carbon−silica composites and alteration of their physicochemical properties. This study opens new avenues for the development of sustainable, robust materials in rapid and facile conversion of biorenewable glycerol to fine chemicals.
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