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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.

2015-11Master thesis

Open access

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.

2016-12-07Master thesis

Open access