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Nanocatalysts for sustainable industrial processses
Publication . Wang, Jiawei; Martins, Luísa Margarida D. R. S.; Rodrigues, João Manuel Cunha
In Chapter 1, rhodium nanoparticles were supported on multiwalled carbon
nanotubes (MWCNTs) and bound to the magnetic core-shell system Fe3O4@TiO2. The
composite Fe3O4@TiO2-Rh-MWCNT and the intermediates were characterized by
SEM, EDS and TEM. Their catalytic activity was studied using i) the hydrogenation
transfer of nitroarenes and cyclohexene in the presence of hydrazine hydrate; ii) the
reduction of 2-nitrophenol with NaBH4; and iii) the decoloration of pigments in the
presence of hydrogen peroxide. The results were monitored by gas chromatography (i)
and UV Visible (ii and iii).
In the second chapter, the catalytic activity of six oxidovanadium(V) aroylhydrazone complexes, viz. [VOL1(OEt)][VOL1(OEt)(EtOH)] (1), [VOL2(OEt)] (2), [Et3NH][VO2L1] (3), [VO2(H2L2)]2·EtOH (4), [VOL1(µ -O)VOL1] (5) and [VOL2(µ -O)VOL2] (6) (H2L1 = 3,5-di-tert-butyl-2-hydroxybenzylidene)-2hydroxybenzohydrazide and H2L2 = 3,5-di-tert-butyl-2-hydroxybenzylidene)-2
aminobenzohydrazide), anchored on nanodiamonds with different treatments, was
studied towards the microwave-assisted partial oxidation of 1-phenylethanol to
acetophenone in the presence of tert-butyl hydroperoxide (TBHP) as oxidant. A high
selectivity for acetophenone was achieved for the optimized conditions. The possibility
of recycling and reuse the heterogeneous catalysts was also investigated.
In chapter 3, the catalytic activity of gold nanoparticles supported at different metal
oxides, such as Fe2O3, Al2O3 ZnO or TiO2, was studied for the above reaction. The
effect of the support, quantity of the catalyst and temperature was investigated. The
recyclability of the gold catalysts was also studied.
In the last chapter, a new copper nanocomposite with functionalized mutiwalled
carbon nanotubes (Cu-MWCNT) was synthesized using a microwave assisted polyol
method. The characterization was performed using XRD and SEM. The catalytic
activity of Cu-MWCNT was studied through the degradation of pigments, such as
amaranth, brilliant blue, indigo, tartrazine and methylene blue.
Metal nanoparticles as catalysts for oxidation reactions
Publication . Ying, Yu; Martins, Luísa Margarida D. R. S.; Rodrigues, João Manuel Cunha
Gold catalysts are currently a “hot topic” of research, as they show application in
many reactions of industrial and environmental importance. The catalytic activity of
gold nanoparticles supported on different carbon materials, as heterogeneous catalysts,
was tested for the microwave-assisted solvent-free oxidation of 1-phenylethanol by
tert-butyl hydroperoxide (TBHP). The catalytic performance was related to the
support interaction, reaction time and temperature, quantity of catalyst, presence of
additives, and other parameters. The possibility of recycling the catalysts was also
investigated.
Gold nanoparticles (1 wt. %) supported on a variety of carbon materials
(activated carbon, graphite, silicon carbide, carbon xerogel, nanodiamonds, and
microdiamonds), by two different methods (colloidal method and double
impregnation), were used as catalysts for the oxidation of 1-phenylethanol. A
maximum yield of acetophenone (99.9%) was obtained with Au nanoparticles
supported on microdiamonds by colloidal method, while Au nanoparticles supported
on silicon carbide by double impregnation method led to the minimum yield of 27.1%.
Moreover, catalyst recyclability was tested up to six consecutive cycles at the
optimized conditions for each catalyst, and it was observed that the catalytic activity
of gold nanoparticles supported on microdiamonds, prepared by the colloidal method,
maintains higher activity when compared with other catalysts after several reaction
cycles.
In addition, copper nanoparticles supported on carbon nanotubes were tested for
degradation of dyes. However, the obtained results were not suitable to be presented
and therefore are compiled in appendix.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
5876
Funding Award Number
UID/QUI/00100/2013