Abstract:

Methane, the primary constituent of natural gas, shale gas, and flammable ice, serves as a crucial carbon-based energy source and chemical feedstock. Traditional gas reserves are universally acknowledged as limited and non-renewable resources over an extended timespan stretching from decades to millennia. Biomethane, with its unique renewable properties, showcases remarkable development potential and presents a compelling supplement and even alternative for fossil fuel. Although catalytic hydrothermal processes appear as promising valorization routes to transfer biomass to sustainable methane, the safety and supply source of high-pressure hydrogen remain key factors restricting the widespread application. Herein, a catalytic approach without an external hydrogen source was developed to transform waste biomass resources into CH₄ under the Ni-Mo catalyst. The total carbon yield of gas products reached up to 92.2%, of which the yield of methane and C₂-C₄ hydrocarbons were 44.9% and 3.0%, respectively. And it’s calculated that approximately 343.6 liters of CH₄ could potentially be generated from 1 kilogram of raw biomass. Ni-based catalysts exhibited the robust activity in cleaving C-C and C-O bonds. And the introduction of an appropriate amount of molybdenum significantly enhanced catalytic performance of reforming and subsequent methanation reaction, likely due to the high adsorption capacity of highly dispersed Ni-Mo catalysts for carbon monoxide and hydrogen molecules, facilitating the methanation reaction. The pathway of catalytic methane production might be inferred that CO, H₂ and a large number of oxygen-containing intermediates were formed via decarbonylation, dehydrogenation, and retro-aldol condensation reaction under hydrothermal condition. These intermediates then underwent the reforming reaction to generate H₂ and CO₂, ultimately forming CH₄ through the methanation reaction.

Key words: Waste biomass, Ni-Mo catalyst, Methane, Hydrogen, Without external hydrogen source