Porous sponges recover butanol
Purifying butanol thus requires a huge amount of energy. Scientists, however, developed new materials that work like a sponge. They are capable to adsorb butanol selectively from that soup of waste and bacteria. Results are promising, but the process to remove butanol out of these sponges can still be improved.
At home, we have a black cat. And he loves carboard boxes. When we were moving, he spontaneously jumped into every box. Apparently, he is not the only one. The internet is full of pictures of cats spontaneously jumping into the weirdest containers. Why they do that? Probably because it is cosy and warm. The cosier, the better.
What does this have to do with biobutanol recovery? A lot. Scientists discovered materials with extremely tiny pores. Those pores are almost a million times smaller than the diameter of a human hear. Just like cats love to jump into boxes, will certain chemicals love to stay inside these cosy pores. By playing with the chemistry of these materials, certain chemicals will be repelled, but others will stick into the pores of these materials. Just like cats are picky when choosing their nest.
During my PhD, I investigated whether we could use such materials to recover butanol from our soup of waste and bacteria. Not easy. Our sponge must commit to some severe criteria. First of all, it has to be able to capture large amounts of butanol. Secondly, it must not adsorb sugars, fats and other chemicals. The largest problem is water, which sticks most easily to these materials.
We screened a large number of candidates and were able to identify two who worked very well. Those materials are capable to adsorb butanol in large amounts. Even better. We could also recover the adsorbed butanol by heating our sponges. Butanol evaporates from the pores and can be used as a chemical. The sponge itself can also be reused. This technique thus has a large potential.
But, there is still some more work. We could recover the adsorbed butanol and re-use our sponge. But the heating process itself could be further optimized. It is still not clear at what temperature butanol evaporates optimally, without using too much energy. Maybe it is not necessary to recover all butanol, which would allow us to use milder temperatures. This still requires further research.
Interested in the technical side? The full story can be found in following publications:
Claessens, B. et al. Identifying selective adsorbents for the recovery of renewable isobutanol. ACS Sustain. Chem. Eng. acssuschemeng.0c02316 (2020). https://doi.org/10.1021/acssuschemeng.0c02316
Claessens, B. et al. Capturing renewable isobutanol from model vapor mixtures using an all-silica beta zeolite. Chem. Eng. J. 412, 128658 (2021). https://doi.org/10.1016/j.cej.2021.128658