Title : Ab initio tools for upgrading of biomass and production of biofuels
Pyrolysis of lignin, derived from lignocellulosic biomass, produces bio-oils with high oxygen content (20-45 wt.%). These bio-oils can be upgraded by hydrodeoxygenation (HDO), a thermal catalytic process under H2 pressure, to obtain more valuable oxygen-free products. Thus, we combine theoretical and experimental techniques to elaborate, characterize, and test innovative HDO catalysts. Among different catalysts and supports, iron supported on silica proves an optimal selectivity/activity with a low deactivation rate. Different amorphous silica surfaces having various silanol densities (7.2, 5.9, 4.6, 3.3, 2, 1.1 OH/nm2) have been considered. DFT calculations show negligible CO competition on phenol adsorption over those surfaces, which makes them more favorable than conventionally used CoMoS supports. Among them, the one with 3.3 OH/nm2 appears to exhibit the highest selectivity for the direct C-O bond cleavage with less water competition effect.
Then single iron atom catalysts (SACs) supported on mesoporous silica were elaborated following the Sol-gel mechanism using non-ionic (P123) and metallic (CTAF) surfactants as porogen. Tuning the P123/CTAF molar ratio enables to control of the iron loading, as well as the silica structural properties. SACS, Fe-impregnated, and Fe/Cu impregnated catalysts were tested for guaiacol HDO conversion, and results proved that Fe-Cu has a better performance (90% conversion, 70% phenol selectivity) than pure Fe catalysts since the incorporation of Cu facilitates the reduction of Fe(III) species.
We will also show how protonated zeolites and mesoporous silica with optimized silanol density can be used to purify the bio-oils obtained by selectively remove the residual phenol from the feed.