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USE OF IONIC LIQUIDS FOR ENERGY SCIENCE

Venerdì 16 giugno alle ore 14:00-16:00

Aula Magna di Ingegneria – Via Loredan 20, Padova

 

Prof. Hiroyuki Ohno, Ph.D. FRSC
President of Tokyo University of Agriculture and Technology

 Ionic liquids (ILs) are salts composed by only ions.  The most noteworthy point of ILs is their quite low melting point.  Other remarkable properties are high ion conductivity and high ion density.  These are quite useful to design ion conductive matrix.  For energy conversion systems, ion conductive materials are essentially important.  ILs provided non-volatile and highly ion conductive fluids, but there arose new weak points.  For example, not only target ions such as lithium cation or proton but also component ions of the ionic liquids migrate under potential gradient resulting low transport number of the target ions.

There are two major ways to improve transport number of the target ions; one is polymerized ionic liquids and the other is the use of zwitterions. The ionic conductivity of monomeric ionic liquid was very high due to extended -conjugated electron orbital of alkylimidazolium cation after introducing vinyl group.  However, the ionic conductivity dropped considerably after polymerization due to lowered number of carrier ions and elevation of local viscosity.  To lower the glass transition temperature of the polymerized ionic liquids, flexible spacer was introduced between polymerizable vinyl group and ionic liquid unit.  Some of them are vigorously examined for applications such as batteries, capacitors, and actuators.  On the other hand, zwitterion-type ionic liquids were prepared and polymerized to enhance the cation transport number.   Mixture of zwitterions and acid or salt gave selective ion transport properties.

The other application is the dissolution of biomass with ionic liquids.  Extraction of valuable resources from biomass is an important subject defending against the threat to future energy crisis.  Extraction of cellulose was a major target for this subject.  However, it is difficult to extract polysaccharides such as cellulose with molecular liquids under mild condition.   We have succeeded to prepare polar ILs that solubilized cellulose under mild condition.  We have analyzed the required factors for ions to dissolve cellulose under mild condition, and reported that 1-alkyl-3-methylimidazolium phosphonate- and phosphinate-type ionic liquids extracted polysaccharides from bran and even wood powder due to their very high proton accepting properties.  Recently, lignin, the other component of biomass, draws attention as valuable resources for aromatic compounds.  Lignin forms complex networks in the biomass, and it is quite difficult to extract lignin.  Since it is possible to extract lignin fragments only after decomposition, the extraction of lignin generally requires harsh condition. We also challenged to extract lignin fragments under mild condition.   For that, we proposed new type of liquids inspired by polar ionic liquids.  I will talk about some recent results on the mild dissolution of cellulose and lignin with ILs or other new liquids.

Introducono il seminario:

Prof. Massimo Guarnieri – Centro “Giorgio Levi Cases”, Università degli Studi di Padova
Prof. Vito Di Noto – Centro “Giorgio Levi Cases”, Università degli Studi di Padova

 

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