(467b) Molecular Design of Solvents for 2nd Generation Biofuels Separation Processes
The second generation biofuels are based on the use of biomass , mainly from lignocellulosic sources, as raw materials for the production of biofuels and for the chemical and paper industry. Many challenging separations problems are faced for the conversion of cellulosic materials in fuels and chemicals. Even though there are different wood processing, in the present work we focus mainly on the process of detoxification of hydroxilates; that will be used for the production of ethanol and other chemicals by fermentation processes.
In this work, the ECOFAC molecular design of solvents program (Cismondi and Brignole ) is upgraded to deal with the separation of organic chemicals found in wood hydroxilates, that are toxic for the fermentation process. For this purpose, the last UNIFAC parameter data bank revision are updated with new parameters reported in the literature for the components of interest. Examples of selection of solvents for different toxic components are presented and a strategy, for solvent selection with multiple objetive optimization goals, is presented. The ECOFAC program is also updated for the prediction of environmental properties, among others: octanol ? water partition coefficients and water solubilities of organic compounds.
The program also incorporates a more general molecular design procedure to generate families of lignocellulosic derivatives that are toxic for the fermentation process. In this way potential solvents can be screened in their capacity to separate these products. As a difference with a typical extraction process the raffinate is in this separation problem the product to be recovered and for this reason the primary solvent properties are more restrictive than in conventional extraction processes.
Another option under development for this particular type of application is the use of A-UNIFAC, an group contribution approach taking into account association.
References  M.Cismondi and E.A.Brignole, Molecular Design of Solvents: An efficient search algorithm for branched molecules. Ind. Eng. Chem. Res. 43(2004) 784-790