(216ap) Designing Ionic Liquids for the Removal of Phenolic Compounds From Bio-Oils: A Microscopic Approach

Authors: 
De Conto, J. F., Universidade Tiradentes
Egues, S., Universidade Tiradentes
Santana, C. C., Universidade Tiradentes
da Rocha, S. R. P., Wayne State University



The production of biofuels from residual biomass has great potential as it not only considers the conversion of carbon rich waste sources into energy, but also provides for an opportunity to use agricultural waste instead of edible biomass.  In the thermochemical process, which is a widely employed process, the biomass is submitted to high temperatures in the absence of oxygen, thus producing a biofuel called bio-oil.  Bio-oil is a brown viscous liquid, chemically unstable and with large amounts of phenolic compounds.  They are the ones responsible for the high viscosity, instability and aging (oxidation) of the bio-oil, which prevents its direct use as a fuel source.  It is of great relevance, therefore, to develop new strategies to improve the quality of the bio-oil by removing such undesirable products.

In this work we determine the affinity of various phenols (representative of those undesirable compounds present in the bio-oil) with ionic liquid candidates using atomic force microscopy (AFM).  The strategy consists in modifying a glass substrate with the ionic liquid and the AFM tip with a moiety possessing strong interaction to the ionic liquid on the substrate.  A reduction in the force between tip and substrate in a solution containing the phenolic compounds of interest indicates strong affinity between phenol-ionic-liquid, and a relative scale of interaction is thus determined.  Ionic-liquids investigated in this work include 1-propyl-3-methylimidazolium chloride and 1-propyl-3-methylimidazolium bis(trifluoro-methylsulfonyl) imide, and the phenolic compounds include phenol, 4-cyanophenol and 2-tert-butyl-6-methylphenol.  We characterized the ionic-liquid modified substrate by contact angle goniometry and XPS, and report the force curves for the different phenolic compounds and ionic-liquids.  This work is relevant as it will allow us to synthesize hybrid organic-inorganic materials such as silica modified with ionic liquids that can be used to remove phenolic compounds from bio-oils.