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.