Ir supported over carbon materials for the selective hydrogenation of chloronitrobenzenes

Abstract

In the present work we have studied the effect of carbon supports with different graphitic character (carbon nanotubes, mesoporous graphite and activated carbon) on the catalytic performance of iridium nanoparticles on the liquid phase chemoselective hydrogenation of para-chloronitrobenzene at room temperature. The effect of the oxygen groups was also evaluated by oxidizing a portion of the carbon nanotubes. The Raman and XRD spectra showed that the mesoporous graphite displayed the strongest graphitic character. The characterization of the catalysts by HR-TEM, XPS and TPR-H2, showed that the catalysts had similar particle size and that the catalysts prepared over the previously oxidized support, Ir/CNTox, was not fully reduced. The activity and selectivity achieved with the catalyst Ir/CNT was the best among the samples and the presence of irdium oxide on Ir/CNTox diminished the yield to p-chloroaniline, being the worse catalyst. The reactivity of different isomers was also studied over Ir/CNT and it followed the order m > o > p. This is a previous version of the article published in Catalysis Today. 2015Today. , 249: 72-78. doi:10.1016Today. /j.cattod.2014 Highlights -Ir catalysts supported on carbon materials with different graphitic character.-The effect of oxygen groups in carbon nanotubes has been evaluated.-Ir/CNT shows the best catalytic performance in p-chloronitrobenzene hydrogenation.-The reactivity of different isomers on Ir/CNT was m > o > p. AbstractIn the present work we have studied the effect of carbon supports with different graphitic character (carbon nanotubes, mesoporous graphite and activated carbon) on the catalytic performance of iridium nanoparticles on the liquid phase chemoselective hydrogenation of para-chloronitrobenzene at room temperature. The effect of the oxygen groups was also evaluated by oxidizing a portion of the carbon nanotubes. TheRaman and XRD spectra showed that the mesoporous graphite displayed the strongest graphitic character. The characterization of the catalysts by HR-TEM, XPS and TPR-H 2 , showed that the catalysts had similar particle size and that the catalysts prepared over the previously oxidized support, Ir/CNTox, was not fully reduced. The activity and selectivity achieved with the catalyst Ir/CNT was the best among the samples and the presence of irdium oxide on Ir/CNTox diminished the yield to p-chloroaniline, *Manuscript Click here to view linked References being the worse catalyst. The reactivity of different isomers was also studied over Ir/CNT and it followed the order m > o > p.

Synthesis of palladium nanoparticles on carbon nanotubes and graphene for the chemoselective hydrogenation of para-chloronitrobenzene

“…Details on the analyses of reactants and products can be found elsewhere [6]. Additional experiments were performed to verify that the reaction was heterogeneously catalyzed: the reaction was stopped at 50% conversion and the liquid filtrate was submitted to the reaction conditions.…”

“…However, to achieve yields higher than 99 % of the desired aromatic haloamines it is necessary to add modifiers or to employ bimetallic catalysts [3,4]. Moreover, the use of a hydrophobic support as carbon materials may inhibit the formation of aniline [5,6]. In addition, the morphology of carbon nanotubes as rolling graphene layers might influence the adsorption of the molecules and hence the catalytic performance.…”

“…Besides, their particular electronic properties can induce a positive charge on the metal species due to electron transfer [7], this activating the N=O bond. However, to obtain an optimal size of the nanoparticles a previous oxidation step is frequently needed which may affect the catalytic performance [6]. Therefore alternative methods to synthetize metal nanoparticles have to be developed.…”

Iridium nanoparticles supported in polymeric membranes: a new material for hydrogenation reactions

“…23 In another work, Pd NPs were supported in cellulose polymeric membranes. [32][33][34][35][36] We report iridium NPs synthesized in the IL [BMI.PF 6 ] combined with cellulose acetate in acetone and the IL 1-n-butyl-3methylimidazolium bis(trifluoromethane sulfonyl)imide [BMI.N(Tf) 2 ] for the generation of new polymeric membranesupported Ir(0) NPs hydrogenation catalysts. 24 In another case, a poly(ionic liquid) was chemically grafted to a microPESs support membrane to stabilize Pd NPs.…”

Synthesis of palladium nanoparticles over graphite oxide and carbon nanotubes by reduction in ethylene glycol and their catalytic performance on the chemoselective hydrogenation of para-chloronitrobenzene

“…Palladium is in general less selective than platinum for this reaction due to parallel dehalogenation, and complete inhibition of the C-Cl scission is difficult [16][17]. In this sense it has been reported that the use of a hydrophobic support as activated carbon may inhibit the formation of aniline [17] and an alternative support as CNT can offer further improvement of the catalytic performance [18]. Moreover, recent literature points to graphene oxide as an ideal candidate to act as support for the synthesis Pd nanoparticles [19][20][21].…”