Catalytic transformations of acids, aldehydes, and phenols in bio-oil to alcohols and esters

Acids, aldehydes, and phenols have negative effects on the properties of bio-oil. In this paper, n-butanal, acetic acid, and phenol were selected as model compounds of aldehydes, acids, and phenols, respectively. To convert these compounds into stable and combustible oxygenated organics (alcohols and esters), separate hydrogenation-esterification (SHE) of n-butanal, phenol, and acetic acid was carried out. 100% conversions of n-butanal and phenol were achieved over C-supported catalysts (Ru/C, Pt/C, and Pd/C) with high selectivity to desired products. With the catalysis of SO42−/ZrO2/SBA-15, the yields of butyl acetate and cyclohexyl acetate were 75.89% and 30.97% respectively, which were higher than those over HZSM-5. Based on the results, one-pot hydrogenation-esterification (OHE) of n-butanal, phenol and acetic acid was tested. In OHE, yields of desired products (alcohols and esters) reached 95%, which were higher than those in SHE. Hydrogenation-esterification is a promising method to convert aldehydes, phenols, and acids in bio-oil to stable and combustible organics.