Steam reforming of levulinic acid as a model compound of bio-oil from the hydrothermal liquefaction of biomass

Identifier:  imarina:9470863

Handle: https://hdl.handle.net/20.500.11797/imarina9470863

Authors:  Lopez, S; Lara, FX; Medina, F; Constantí, M; Montané, D

Abstract:
Hydrothermal liquefaction (HTL) of wet and lignocellulosic biomass yields bio-oil and an aqueous phase rich in furans, aldehydes, ketones, organic acids, and phenolics. Bio-oil can be used as a drop-in fuel after hydrotreatment to enhance its energy density and compatibility with conventional fuels. Steam reforming (SR) of the aqueous phase has been proposed to source hydrogen for hydrotreating the bio-oil. Despite levulinic acid (LA) being a main cellulose-derived product in the aqueous phase of HTL, information on its steam reforming is limited. In this work, we studied the SR of LA on Ni/Mg-Al catalysts obtained from hydrotalcite-like precursors, both unpromoted and promoted with Zr and Ce. The catalysts were synthesized by coprecipitation and calcination at 450, 600 and 750 degrees C, and activated by reduction at 600 degrees C. Activity was tested for 16 h at 500 and 600 degrees C at steam-to-carbon molar ratios (S/C) of 2.4, 5.4 and 8.4. Filamentous and multilayered carbon structures were observed in the unpromoted catalysts, especially at the lower temperature and S/C ratios. Promotion with Zr decreased coking resistance and increased the formation of carbon filaments. Addition of CeO2 reduced the extent of coking, but still multilayered carbon deposits and whiskers were formed. A Ce-promoted catalyst maintained constant activity for 100 h at 600 degrees C, S/C of 8.4, and WHSVLA of 6.47 h-1, achieving complete LA conversion, a fractional yield of hydrogen of 0.91, and selectivity to carbon dioxide, carbon monoxide and methane of 0.83, 0.11 and 0.01, with a carbon balance closure above 96 %.