Metal nanoparticle–carbon nanotubes hybrid catalysts immobilized in a polymeric membrane for the reduction of 4-nitrophenol
SN Applied Sciences(2019)
摘要
In this work, the synthesis of silver and copper nanoparticles and bimetallic silver–platinum and copper–platinum nanoparticles, in previously functionalized multi-walled carbon nanotubes (MWCNT), was carried out using the intermatrix synthesis for the charge of the first metal, and a galvanic replacement for the deposition of a second metal to form the bimetallic NPs. Well-controlled small size NPs were obtained as demonstrated by TEM, with a homogeneous distribution and mean particle diameters of ca. 2.9 nm. The hybrid MNPs/MWCNTs catalysts were characterized by FTIR, TEM and XPS. The metal content was determined by TGA and validated via FAAS. Thereupon, the metal–MWCNTs hybrid catalysts were incorporated into a polymeric membrane (PM) and characterized by SEM. The effects of the hybrid catalyst–polymeric support interactions and the role of the MNPs/MWCNTs/PM materials as heterogeneous catalysts were evaluated from the catalytic performance on the reduction of 4-nitrophenol as a model reaction. An apparent rate constant normalized by the metal content of 1706.7 s −1 mol −1 was achieved for the best system (Ag–PtNPs/MWCNTs/PMR) along with a decrease in the percentage of conversion from 95% (first cycle) to 80% (third cycle). Results indicated that the catalytic activity depends mainly on the MNPs size and the metal content in the catalyst. The catalytic activity of the MNPs/MWCNTs was only 3 times higher than for the MNPs/MWCNTs/PMs catalysts, with the former presenting the advantage of being easily recovered from the reaction medium, thus, demonstrating the capability to perform an efficient and sustainable process.
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关键词
Multi-walled carbon nanotubes, Mono and bimetallic nanoparticles, Polymeric membranes, Hybrid catalyst, Heterogeneous catalysis, 4-Nitrophenol reduction
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