Influence of Ni/Mo Ratio and Lanthanum Loading on Clay-Supported Ni–Mo Catalysts for In-Situ Rice Bran Pyrolysis: Optimizing Bio-Oil Yield, Deoxygenation, and Desulfurization

The high cost of post-pyrolysis upgrading of pyrolysis bio-oil due to its high oxygen and sulphur contents poses severe drawbacks to its use. This study investigates the influence of the Ni/Mo weight ratio and La loading on yield, deoxygenation, and desulfurization of bio-oil during in-situ catalytic pyrolysis of rice bran. The pyrolysis was performed at 450°C in a fixed bed reactor, using the catalysts synthesised via the sequential incipient wetness impregnation and calcination, with La loadings varied between 1–3 wt%, Ni between 2–10 wt%, and Mo between 2–10 wt% to identify the most effective compositions. A mesoporous catalyst with a surface area of 205.45 m²/g achieved a maximum bio-oil yield of 28.23% at a 1:1 Ni/Mo weight ratio with 1 wt% La. The low La concentration provides the balanced acidity and metal dispersion, promoting Ni hydrogenation potential and the cracking ability of Mo. A balanced Ni/Mo weight ratio also favoured sulphur removal due to the synergy of Ni promoting C–S bond cleavage and Mo facilitating sulphur adsorption. Furthermore , higher Mo content loading produced enhanced sulphur reduction due to the availability of more Mo sites for sulphur adsorption. At a 2:1 Ni/Mo weight ratio with 2 wt% La loading, La regulates acidity and enhances metal dispersion to boost Ni-driven hydrogenation, while Mo stabilises Ni active sites, achieving 89% bio-oil deoxygenation. The bio-oil exhibits diesel-range properties with higher energy value and predominant long-chain hydrocarbons. The in-situ catalytic reaction enhanced cracking and decarboxylation, which reduces the oil's oxygen and sulphur contents at the source, thus reducing the complexity and post-pyrolysis upgrading cost.