GuaiacolHDOon La‐modified Pt/Al2O3: Influence of rare‐earth loading

Abstract

AbstractThe stability of the catalyst used in hydrodeoxygenation (HDO) of biomass‐derived oils needs improvement. La has been applied in delaying Al2O3phase‐change under reaction conditions. Lanthanum (0.5–8 wt.%)‐γ‐alumina was studied as Pt (1 wt.%) carrier aimed at guaiacol (GUA) HDO. Materials characterization included N2physisorption, X‐ray diffraction (XRD), thermal analysis, FTIR, UV–vis, and TPR. Solids pore size (~8–10 nm) was suitable for GUA (kinetic diameter~0.668 nm) hydrotreating. Mixed carriers were amorphous (XRD), suggesting well‐dispersed La domains; meanwhile, carbonates/bicarbonates were formed (from CO2) due to the basic surface properties of modified supports (FTIR). That could impart catalyst stability by inhibiting coking through the passivation of Lewis acidity on Al2O3. Pt reducibility increased with La loading in various formulations. However, that was not reflected in enhanced GUA HDO (T = 488 K and P = 3.2 MPa, batch reactor), presumably due to the strong metal–support interaction (SMSI), where LaOxcovered the metallic Pt particle surface. GUA HDO on various catalysts was approximated by pseudo‐first‐order kinetics (integral regime,k), where deviations were observed as La loading increased, presumably by an SMSI state that could affect the rate‐determining step of the reaction mechanism. Basic sites provided by rare‐earth could contribute to altering HDO reaction pathways as well. At 1 wt.% rare‐earth, GUA HDO was maximized (k~25% higher than that on Pt/Al2O3), with that material also exhibiting similar deoxygenation (85%–90% at total GUA conversion) to the latter Pt over pristine alumina. Conversely, both parameters significantly diminished over the catalyst of the highest La content. Materials at low rare‐earth concentrations deserve further studies focused on catalyst stability under HDO conditions.