Monday, May 4, 2009
9-22
High Silica Zeolites as an Alternative to Amine Based Adsorbents in Succinic acid Recovery
Cagri Efe, Adrie J.J. Straathof, and Luuk A.M. van der Wielen. Department of Biotechnology, Delft University of Technology, Julianalaan 67, Delft, 2628 BC, Netherlands
Succinic acid is one of most attractive renewable C4 basic chemicals to replace the current chemical building blocks. However, the separation of succinic acid from fermentation broth requires further improvement for sustainable and economical operation. A fundamental improvement would be obtained by selective removal of succinic acid from a low pH fermentation medium (~pH=4) while leaving the succinate salts in the medium. Our approach involves the silicalite molecular sieve adsorbents which adsorb hydrophobic molecules.
Three different powder zeolites, CBV-901, CP811C-300 and CVB 28014, were screened for succinic acid removal from aqueous media. CVB-28014 showed the highest equilibrium loading and was used for the follow up studies. In the presence of Na+, the succinic acid adsorption dropped in parallel with the succinic acid dissociation and the adsorbent didn’t show a significant affinity for charged succinate. At pH ~ 4.4, the adsorbent still performed efficiently. Higher temperatures reduced the equilibrium loadings. But, the effect was too weak to be used for regeneration. Still, it can be used as an auxiliary process condition. In presence of acetic acid at initial concentrations of 25% of that of succinic acid like occurring in fermentation, the equilibrium loading of succinic acid dropped but the succinic acid capacities were still sufficient. Succinic acid in ethanol solution showed a poor adsorption behavior so that regeneration can be achieved by using an adsorption competitive solvent like ethanol. The current results show this type of zeolite is an attractive option for the separation of succinic acid from fermentation media.