Molybdenum oxide loaded ceria catalysts for the selective production of monomeric alkyl phenols from the hydrogenolysis of Kraft lignin

Lignin, an aromatic biopolymer produced in large quantities as a byproduct of biorefineries, has garnered significant attention for its potential to be valorized into valuable compounds. This demands for the development of an efficient catalyst. This study is the first evaluate the catalytic efficiency of a synthesized Mo-loaded CeO 2 (5Mo/CeO 2 -syn) catalyst for an in-situ upgradation of lignin oil. The 5Mo/CeO 2 -syn catalyst demonstrated exceptional performance, achieving a high lignin liquefaction yield of 66.7 wt%, compared to 48.1 wt% for 5Mo/CeO 2 -com and 35.5 wt% for the non-catalytic (N-cat) reaction. The effects of varying metal loadings and different alcoholic solvents were systematically investigated for kraft lignin (KL) depolymerization. The results of GC–MS and elemental analysis for the bio-oils revealed a significant increase in calorific value (36 MJ/kg, 5Mo/CeO 2 -syn), attributed to the efficient removal of oxygenates. The N-cat bio-oil contained a high proportion of guaiacyl (G-type) phenols (73.4 %), which were significantly reduced during catalytic reactions as they were transformed into alkyl (H-type) phenols. The GPC analysis also evaluated for the lignin and optimum bio-oils, to confirm the breakage of the macro-polymeric structure of lignin into respective monomeric compounds. Moreover, the 5Mo/CeO 2 -syn catalyst was further evaluated across four catalytic cycles, demonstrating its stability and reusability.