Michele O. Vieira

Rationalizing the role of the anion in CO2 capture and conversion using imidazolium-based ionic liquid modified mesoporous silica

Covalently supported ionic liquids in mesoporous materials were prepared by grafting 1-methyl-3-(3-trimethoxysylilpropyl)imidazolium chloride in MCM-41. Subsequently, the [Cl−] anion was changed to [BF4−], [PF6−] or [Tf2N−]. These materials that present an advantageous combination of the properties of mesoporous solid materials and ionic liquids were evaluated for CO2 sorption as well as catalysts for CO2 conversion into cyclic carbonate using propylene oxide. The material with the [Cl−] anion had the best performance for both CO2 sorption and conversion. A CO2 sorption of 11 w/w% on the adsorbent was achieved and the cycloaddition reaction exhibited a conversion of 67% with 82% selectivity with the catalyst remaining active after 5 cycles, proving that the same sorbent/catalyst setup can be used for both CO2 capture and conversion. Based on the experimental data and electronic-structure numerical simulations, we have hypothesized two major reasons why chloride out performs other anions when adsorbed on MCM-41 unlike unsupported ionic liquids.

A New Approach to CO2 Capture and Conversion Using Imidazolium Based-Ionic Liquids as Sorbent and Catalyst

Although the carbon capture and storage (CCS) technologies are receiving great attention for mitigation of greenhouse gas effect, the increasing costs and energy penalties associated to its implementation are still major drawbacks. However, the use of CO2 as a C1 building block in organic synthesis can be very attractive for the design of environmentally friendly processes. In this work, we have studied both the CO2 sorption and catalytic activities of some imidazolium based ionic liquids (ILs) for cyclic carbonate synthesis. The work demonstrates that the presence of a nucleophilic group in the catalytic system can enhance its performance by the use of an IL with a halide anion or by mixing a halide co-catalyst with ILs. The latter approach allowed to obtain an effective system for CO2 capture constituted by a fluorinated IL plus ZnBr2 that performs cyclic carbonate synthesis with 90% yield and 82% of selectivity.

Surface Active Ionic Liquids as Catalyst for CO2 Conversion to Propylene Carbonate

CO2 capture is an efficient possibility to mitigate environmental impacts. An efficient transformation of CO2 into useful chemicals is a need from environmental protection and resource utilization viewpoint. Cyclic carbonates, such as propylene carbonate is used in numerous technologies. We hereby report eight surface active ionic liquids (SAILs) composed of the well-known cations ([bmim+] and [TBA+]) and long-alkyl-chain anions ([C12SO4−], [C12ESO4−], [C12BSO3−] and [C12SAR−]). In this work, we have studied catalytic activities of SAILs for cyclic carbonate synthesis. The work demonstrates that [TBA+] is more active as a catalyst because the higher molecular volume increases the distance cation/anion, consequently, a weaker electrostatic interaction cation/anion results in a more nucleophilic anion. The [TBA][C12SO4] was the SAIL that presented better catalytic activity, reaching 79.2% of conversion and 87.7% of selectivity, besides the high capacity of recycles and possible use for the catalysis of other cyclic carbonates.Graphical Abstract