Efficient downstream processing of renewable alcohols using zeolite adsorbents

Increasing energy prices, global warming, and concerns for environmental pollution has been pushing the chemical industry to look for alternatives for traditional, fossil-based chemical feedstocks. Important platform molecules are alcohols, which can be produced from renewable feedstocks via fermentation. The implementation of these fermentation processes to produce chemicals leads to important challenges regarding the downstream purification. Adsorption-based purification technologies are alternatives for traditional energy-intensive distillation processes. The well-defined pore structure of zeolites makes them ideal candidates for the removal of alcohols from these complex fermentation mixtures, which contain cells and cell debris, acids, sugars, lipids, and proteins. The following chapter covers important aspects in the adsorption mechanism of alcohols and water in (mainly) hydrophobic zeolite pores, such as cluster formation and hydrogen bonding. These effects inevitably also play a role when looking at the diffusion of alcohols inside the zeolite pores. Finally, this chapter will cover some examples of studies where hydrophobic zeolites have been used to recover bio-alcohols, such as biobutanol and bioethanol, from model solutions or fermentation broths via fixed-bed separations.