The Nature of Carbon Dioxide in Bare Ionic Liquids

FCT- PTDC/QUI-QFI/31508/2017; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. Grant Numbers: 158804/2017-01, 001; Conselho Nacional de Desenvolvimento Científico e Tecnológico. Grant Numbers: 406260/2018-4, 406750/2016-5, 465454/2014-3; Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul. Grant Numbers: 16/2552-0000, 18/2551-0000561-4; Fundación Séneca. Grant Number: 20790/PI/18.Ionic liquids (ILs) are among the most studied and promising materials for selective CO2 capture and transformation. The high CO2 sorption capacity associated with the possibility to activate this rather stable molecule through stabilization of ionic/radical species or covalent interactions either with the cation or anion has opened new avenues for CO2 functionalization. However, recent reports have demonstrated that another simpler and plausible pathway is also involved in the sorption/activation of CO2 by ILs associated with basic anions. Bare ILs or IL solutions contain almost invariable significant amounts of water and through interaction with CO2 generate carbonates/bicarbonates rather than carbamic acids or amidates. In these cases, the IL acts as a base and not a nucleophile and yields buffer-like solutions that can be used to shift the equilibrium toward acid products in different CO2 reutilization reactions. In this Minireview, the emergence of IL buffer-like solutions as a new reactivity paradigm in CO2 capture and activation is described and analyzed critically, mainly through the evaluation of NMR data.authorsversionpublishe

CO2 Electroreduction in Ionic Liquids

CO2 electroreduction is among the most promising approaches used to transform this green-house gas into useful fuels and chemicals. Ionic liquids (ILs) have already proved to be the adequate media for CO2 dissolution, activation, and stabilization of radical and ionic electrochemical active species in aqueous solutions. In general, IL electrolytes reduce the overpotential, increase the current density, and allow for the modulation of solution pH, driving product selectivity. However, little is known about the main role of these salts in the CO2 reduction process the assumption that ILs form solvent-separated ions. However, most of the ILs in solution are better described as anisotropic fluids and display properties of an extended cooperative network of supramolecular species. That strongly reflects their mesoscopic and nanoscopic organization, inducing different processes in CO2 reduction compared to those observed in classical electrolyte solutions. The major aspects concerning the relationship between the structural organization of ILs and the electrochemical reduction of CO2 will be critically discussed considering selected recent examples

Sistema catalítico, e, processo para remoção de compostos heteroátomicos de correntes de hidrocarbonetos

Universidade Federal do Rio Grande do SulQuímicaDepositad

Uso de nanopartículas derivadas de organocalcogenetosmetálicos como catalisadores para obtenção de hidrogênio a partir da fotólise da água

Universidade Federal de Santa MariaUniversidade Federal do Rio Grande do SulQuímicaDepositad

Selective CO2 hydrogenation to formic acid with multifunctional ionic liquids

The development of simple, cost-effective and sustainable methods to transform CO2 into feedstock chemicals is essential to reduce the dependence on fossil fuels of the chemical industry. Here, we report the selective and efficient catalytic hydrogenation of CO2 to formic acid (FA) using a synergistic combination of an ionic liquid (IL) with basic anions and relatively simple catalysts derived from the precursor Ru3(CO)12]. Very high values of TON (17000) and TOF have been observed and FA solutions with concentrations of up to 1.2 M have been produced. In this system, the imidazolium based IL associated with the acetate anion acts as precursor for the formation of the catalytically active Ru-H species, catalyst stabilizer and as an acid buffer, shifting the equilibrium towards free formic acid. Moreover, the IL acts as an entropic driver (via augmentation of the number of microstates), lowering the entropic contribution imposed by the IL surrounding the catalytically active sites. The favorable thermodynamic conditions enable the reaction to proceed efficiently at low pressure pressures, and furthermore the immobilization of the IL onto a solid support facilitates the separation of FA at the end of the reaction

Efficient Electrocatalytic CO2 Reduction Driven by Ionic Liquid Buffer‐Like Solutions

We show here that electrocatalysis of CO2 reduction in aqueous electrolytes containing the ionic liquid (IL) 1-n-butyl-2,3dimethylimidazolium acetate ([BMMIm][OAc]) and dimethyl sulfoxide (DMSO) proceeds at low overpotentials (−0.9 V vs. Ag/AgCl) at commercially-available Au electrodes, and with high selectivity for CO production (58% faradaic efficiency at –1.6 V vs Ag/AgCl). 0.43 mol of CO2 per mol of IL can be absorbed into the electrolyte at atmospheric pressure, forming bicarbonate and providing a constant supply of dissolved CO2 to the surface of the electrode. We also show that electrocatalysis of CO2 reduction in the electrolyte is facilitated by stabilization of CO2 radical anions by the imidazolium cations of the IL and buffer-like effects with bicarbonate

Treatment and characterization of biomass of soybean and rice hulls using ionic liquids for the liberation of fermentable sugars

We investigated the changes in the physical structure of cellulose recovered from soybean and rice hulls treated with the ionic liquids 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) and 1-butyl-3-methylimidazolium acetate ([bmim][Ac]). The characterization was carried out by a combination of thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Regenerated cellulose from soybean hull showed loss of crystallinity and high structural disruption caused by both ionic liquid treatments as compared to the untreated material. In contrast, rice hull presented only a small structural disruption when treated with [bmim][Ac] and was practically unaffected by [bmim][Cl], showing that this biomass residue is recalcitrance towards physico-chemical treatments, possibly as a consequence of its high composition content in silica. These results suggest the use of soybean hull as a substrate to be treated with ionic liquids in the preparation of lignocellulosic hydrolysates to be used in second-generation ethanol production, whereas other methods should be considered to treat rice hull biomass