Biofuel Production From Model Bio-Oil: Impact of Perovskite-Based Catalysts and Metal Oxide Mixtures on Upgrading and Selectivity

Abstract

Biofuel production was conducted using model bio-oil to examine the upgrading performance of perovskite-based and metal oxide catalysts. Bare and Ce, Co, Sr, Mo, and tungstophosphoric acid-doped LaFeO3 perovskite-based catalysts were synthesized via sol-gel method. The bio-oil upgrading activity of commercial La2O3, alpha-Fe2O3, and alpha-Fe2O3/La2O3 metal oxide catalysts compared to LaFeO3-based catalyst was also investigated. Catalyst properties were characterized by XRD, TGA/DTG, N-2 adsorption/desorption, SEM-EDX, FTIR, DRIFTS, and Raman techniques. Activity tests were performed at 400 degrees C at under atmospheric pressure. A model bio-oil mixture was formulated with hydroxy propanone/formic acid/furfural (2:4:3 mass ratio), and a dilution ratio of 30:70 (bio-oil mixture/alcohol) was applied. Ethanol and methanol were examined as co-reactants. Ethanol-assisted upgrading resulted in higher deoxygenation efficiency and enhanced iso-paraffin selectivity compared to methanol. Increasing the calcination temperature of LaFeO3 from 700 to 800 degrees C improved crystallinity and raised the overall bio-oil conversion from 69.4 to 83.4%. The bare LaFeO3 catalyst calcined at 800 degrees C exhibited high iso-paraffin selectivity (69.4 vol%) and oil-phase selectivity (80.3%). The superior upgrading performance of LaFeO3 was attributed to its orthorhombic perovskite lattice structure and mild surface acidity, favoring cracking, deoxygenation, and coke suppression. Ce-doped LaFeO3 (x = 0.1) enhanced oxygen mobility and promoted olefin selectivity resulting in the highest overall bio-oil conversion (83.8%). At higher Ce contents (x = 0.2), CeO2 side-phase formation promoted naphthene selectivity. In contrast, Sr-, Co-, and Mo-doped LaFeO3 catalysts showed higher oxygenated content. Compared with alpha-Fe2O3/La2O3 mixed catalyst, which exhibited 16.0 wt% coke formation, LaFeO3 showed low coke deposition (0.24 wt%). Long-term stability testing of LaFeO3 revealed only a very small amount of carbon formation (1.39 wt%) and no catalyst deactivation. Similar product distributions were obtained in both short-term and long-term tests. [GRAPHICS]