Optimization of Allyl Alcohol Production from Glycerol over Iron Oxide Catalyst

Abstract

Glycerol is a major by-product of biodiesel production and has attracted great interest as a precursor for the preparation of various valuable chemicals. Conversion of glycerol over α-Fe₂O₃ catalyst in a fixed-bed flow reactor was investigated to understand the catalytic activity of iron oxide for the selective production of allyl alcohol. Addition of formic acid to the glycerol feed was effective in improving allyl alcohol production because decomposition on the catalyst formed hydrogen atoms, which were consumed in dehydroxylation of glycerol and reduction of α-Fe₂O₃ to Fe₃O₄ during glycerol conversion. Moreover, the allyl alcohol yield was further increased using potassium-loaded α-Fe₂O₃ catalyst, which was attributed to change in the acid sites. The original acid sites of α-Fe₂O₃, mainly Lewis acid sites, were occupied by potassium, and Brønsted acid sites formed during glycerol conversion. To further enhance the allyl alcohol yield, we attempted to minimize the polymerization reaction by optimizing the potassium loading, W_cat/F_glycerol value (i.e., contact time), and reaction temperature. The highest allyl alcohol yield of 39.8 C-mol% was achieved over 1 mol% potassium-loaded α-Fe₂O₃ at 623 K and with W_cat/F_glycerol of 1 h.