Tailoring the Composition of Bio‐oil by Vapor‐Phase Removal of Organic Acids

Selective removal of organic acids from biomass pyrolysis vapors was demonstrated. A broad adsorbent range was tested with CaCO 3 showing the best selectivity. Extensive material characterization demonstrated that the acid removal occurred through monolayer adsorption on CaCO 3 . Adsorbent regeneration was achieved by in situ heat treatment of the postreaction adsorbent where the adsorbed acid was converted into a ketone. The mitigation of the loss of other products was achieved by using surface modified CaCO 3 materials, resulting in a significant improvement in the selectivity toward organic acid removal. The surface modification appeared to lead to formation of a metal‐carboxylate intermediate consisting of both acetate and carbonate groups. Acetate group on the CaCO 3 surface resulted in the suppression of side reactions. Generally, a higher acid removal was accompanied with a greater loss of other compounds, which could be tuned by using CaCO 3 with different surface modification.