Impact of Potassium Addition on the Performance of Ni/MgAl2O4 Catalysts in Steam Reforming of Bio-Oil Model Compounds

• Published in: ACS Engineering Au 2025-02, Vol.5 (1), p.10-26
• Main Authors: Taschin, Alan R., Petrolini, Davi D., Braga, Adriano H., Baiotto, Alexandre, Ferreira, Adriana Paula, Lopez-Castillo, Alejandro, Santos, João Batista O., Bueno, José M. C.
• Format: Article
• Language: English
• ISSN: 2694-2488; 2694-2488
• DOI: 10.1021/acsengineeringau.4c00034

Ni/MgAl2O4 catalysts with and without K promotion were tested in steam reforming of phenol (SRP), ethanol (SRE), and butanol (SRB), to evaluate the effect of K on catalytic activity and methane formation. The catalysts were prepared by a wet impregnation method and were characterized using nitrogen adsorption, in situ XRD, H2-TPR, TEM, XPS, and XANES techniques. Catalytic evaluations were performed at temperatures ranging from 250 to 650 °C. DFT calculations were employed to study the hydrogenation of CH x species on Ni modified by K. The addition of K to the Ni catalysts weakened the NiO-support interaction, causing NiO agglomeration and an increase in Ni particle size. The effect of K on CH4 formation was strongly influenced by the structure of the reformed molecule, leading to the formation of different CH x species during the reaction. The introduction of K into the Ni catalyst suppressed formation of CH4 by hydrogenation of CH, with this effect diminishing for CH2 and being absent for CH3 species. DFT calculations of the interaction between CH x species absorbed in an Ni4 cluster (CH x -Ni4) and K, particularly KOH, indicated that species such as HOKH x C–Ni4 were stabilized, with decreased energies of −291.5, −242.4, and −27.7 kJ/mol for CH, CH2, and CH3, respectively. The increased heat of adsorption for CH and CH2 species reduced their hydrogenation activity toward methane.