Liquid Membranes in Catalysis

: The supported ionic liquid (SIL) membranes have demonstrated huge potential for numerous applications in current separation science and catalysis. Membrane technology allows for separation of complex mixtures of gases, vapours, liquids and /or solids below trivial conditions. Simultaneous chemical transformations can also be achieved in membranes by using catalytically active materials comprising the membrane or embedded catalysts in the custom built membrane reactors. In the present editorial, the remarkable contribution of liquid membranes in catalysis is highlighted. Some recent applications are presented and compared with conventional methods. In addition, SILs and their applications in catalysis, catalytic membranes and recent advances in membrane separation processes are briefly described.

Novel Ionic Conducting Composite Membrane Based on Polymerizable Ionic Liquids

In this work, the design and characterization of new supported ionic liquid membranes, as medium-temperature polymer electrolyte membranes for fuel-cell application, are described. These membranes were elaborated by the impregnation of porous polyimide Matrimid® with different synthesized protic ionic liquids containing polymerizable vinyl, allyl, or methacrylate groups. The ionic liquid polymerization was optimized in terms of the nature of the used (photo)initiator, its quantity, and reaction duration. The mechanical and thermal properties, as well as the proton conductivities of the supported ionic liquid membranes were analyzed in dynamic and static modes, as a function of the chemical structure of the protic ionic liquid. The obtained membranes were found to be flexible with Young’s modulus and elongation at break values were equal to 1371 MPa and 271%, respectively. Besides, these membranes exhibited high thermal stability with initial decomposition temperatures > 300 °C. In addition, the resulting supported membranes possessed good proton conductivity over a wide temperature range (from 30 to 150 °C). For example, the three-component Matrimid®/vinylimidazolium/polyvinylimidazolium trifluoromethane sulfonate membrane showed the highest proton conductivity—~5 × 10−2 mS/cm and ~0.1 mS/cm at 100 °C and 150 °C, respectively. This result makes the obtained membranes attractive for medium-temperature fuel-cell application.

Novel and Reusable Mesoporous Silica Supported 4-Methylbenzenesul- fonate-functionalized Ionic Liquids for Room Temperature Highly Efficient Preparation of 2,4,5-Triaryl-1H-imidazoles

A series of mesoporous materials supported ionic liquids were prepared and tested as effective and practical catalysts for the synthesis of 2,4,5-triaryl-1H-imidazoles. The effects of type of catalysts, catalyst amount, and catalyst stability have also been investigated in detail, the catalyst Ti-SBA-15@ILTsO exhibited excellent activity in excellent yields of 92 % ~ 99 % with low catalyst amount at room temperature within 1 h. In addition, the supported ionic liquid can be easily recovered and reused for six times with satisfactory catalytic activity. Furthermore, a general synergetic catalytic mechanism for the reaction was proposed. Maybe this work employing Ti-SBA-15@ILTsO as highly efficient and stable catalyst for the synthesis of 2,4,5-triaryl-1H-imidazoles has potential commercial applications. Resumen. Se prepararon y probaron una serie de materiales mesoporosos soportados con líquidos iónicos como catalizadores eficaces y prácticos para la síntesis de 2,4,5-triaryl-1H-imidazoles. También se investigaron en detalle los efectos del tipo de catalizadores, la cantidad de catalizador y la estabilidad del catalizador. El catalizador Ti-SBA-15@ILTsO mostró una excelente actividad con rendimientos excelentes del 92 % ~ 99% con una baja cantidad de catalizador a temperatura ambiente en 1 h. Además, el líquido iónico soportado puede recuperarse fácilmente y reutilizarse durante seis veces con una actividad catalítica satisfactoria. Por otro lado, se propuso un mecanismo catalítico sinérgico general para la reacción. Este trabajo que emplea Ti-SBA-15@ILTsO como catalizador altamente eficiente y estable para la síntesis de 2,4,5-triaril-1H-imidazoles puede tener aplicaciones potencialmente comerciales.

Rh NPs Immobilized on Phosphonium- based Supported Ionic Liquid Phases (Rh@SILPs) as Hydrogenation Catalysts

A series of phosphonium-based supported ionic liquid phases (SILPs) was prepared for the immobilization of Rh nanoparticles (Rh@SILP). The influence of systematic variations in the structure of the ionic liquid-type molecular modifiers (anion, P-alkyl chain length) on the formation and catalytic properties of Rh nanoparticles (NPs) was investigated. Both the nature of the anion and the length of the P-alkyl chain were found to have a strong impact on the morphology of the NPs, ranging from small (1.2–1.7 nm) and well-dispersed NPs to the formation of large NPs (9.9–16.5 nm) and/or aggregates. The catalytic properties of the resulting Rh@SILP materials were explored using the hydrogenation of benzylideneacetone and biomass-derived furfuralacetone as model reactions. The changes in ring and C=O hydrogenation activity as a function of the SILP structure and the Rh NPs size allowed for the selective synthesis of products with distinct molecular functionalities.