Ruthenium dioxide nanoparticles in ionic liquids: synthesis, characterization and catalytic properties in hydrogenation of olefins and arenes

Abstract

A reação de NaBH 4 com RuCl 3 dissolvido no líquido iônico 1-n-butil-3-metilimidazólio hexafluorfosfato (BMI.PF 6) é um método simples e reprodutível para a síntese de nanopartículas de RuO 2 estáveis com distribuição estreita e diâmetro da partícula entre 2-3 nm. As nanopartículas de RuO 2 foram caracterizadas por XRD, XPS, EDS e TEM. Estas nanopartículas mostraram alta atividade catalítica tanto na catálise heterogênea quanto na hidrogenação bifásica líquido-líquido de olefinas e arenos sob condições moderadas de reação. Experimentos de envenenamento com Hg(0) e CS 2 , e análises de XRD e TEM de partículas isoladas após a catálise indicaram a formação de nanopartículas de Ru(0). As nanopartículas podem ser reutilizadas em condições de catálise heterogênea até 10 vezes na hidrogenação de 1-hexeno rendendo um número total de ciclos catalíticos de 175.000 para átomos de Ru expostos. The reaction of NaBH 4 with RuCl 3 dissolved in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF 6) ionic liquid is a simple and reproducible method for the synthesis of stable RuO 2 nanoparticles with a narrow size distribution within 2-3 nm. RuO 2 nanoparticles were characterized by XRD, XPS, EDS and TEM. These nanoparticles showed high catalytic activity either in the solventless or liquid-liquid biphasic hydrogenation of olefins and arenes under mild reaction conditions. Hg(0) and CS 2 poisoning experiments and XRD and TEM analysis of particles isolated after catalysis indicated the formation of Ru(0) nanoparticles. The nanoparticles could be re-used in solventless conditions up to 10 times in the hydrogenation of 1-hexene yielding a total turnover number for exposed Ru atoms of 175,000.

Nanoscale Ru(0) Particles: Arene Hydrogenation Catalysts in Imidazolium Ionic Liquids

“…The dimension of particle size (around 3.0 nm) of these nanoparticles is similar to that observed for the nanoparticles prepared by the decomposition of [Ru(COD)(COT)] 18,27 or the reduction of ruthenium oxide 26,41 dispersed in imidazolium ILs. The narrow size distribution and low agglomeration of the small Ru-NPs in the ILs 2, 4, and 5 indicate the good properties of these ILs for the synthesis, immobilization, and stabilization of Ru-NPs.…”

Ruthenium Nanoparticles in Ionic Liquids – A Saga

“…Ru-NPs were first generated in ionic liquids during an investigation of the catalytic hydrogenation behaviour of RuO 2 in these media [55,56]. Heavy metals such as mercury as well as molecules such as CS 2 bind strongly and irreversibly to noble metals, therefore blocking active catalytic sites.…”

“…Some examples for catalyst-recycling in batch reactions show the promising potential for their recyclability without significant loss of catalyst activity ( Table 2: Entry A) [55][56][57]81]. It is impor-tant to note that the stability of NPs is superior in ILs in comparison to NPs under solventless conditions.…”

Metal oxide and bimetallic nanoparticles in ionic liquids: synthesis and application in multiphase catalysis

“…One of the early examples by Dupont et al described the application of small-sized RuO 2 NPs (2 -3 nm) prepared from RuCl 3 · 3H 2 O in 1-n -butyl-3-methylimidazolium hexafluorophosphate (C 4 C 1 I.PF 6 ) as a precursor for the catalytic hydrogenation of alkenes and arenes [32,33] . The NPs are suitable as recyclable catalysts for the hydrogenation of 1-hexene, 2,3-dimethyl-2-butene, cyclohexene, 1-methyl-1-cyclohexene, benzene, toluene, and p -xylene under 4 bar H 2 at 75 ° C. The NPs could be recycled for 10 runs under solventless conditions for the hydrogenation of 1-hexene with a total turnover number (tTON) for exposed Ru atoms of 175,000.…”

“…However, only few reports exist on metal oxides and bimetallic alloy or core-shell NPs in ILs, as precursors and/or catalysts for transformations in multiphase systems [13, 32 -55] . Their potential applications cover such fields as hydrogenation reactions [32,33,36,40,45] , hydrogenolysis [39,56] , C-C coupling [41] , C-C bond cleavage [13] , dehalogenation of arenes [55] , condensation reactions [54] , oxidation [46] , as well as electrochemical applications [42, 47, 51 -53, 57, 58] . The scope of the present review is to discuss the mentioned traditional catalytic applications, excluding electrochemical applications.…”