Abstract:With the rapid development of global urbanization and industrialization, the yield of municipal sludge is increasing rapidly. The lack of technologies to process large amounts of municipal sludge in a timely manner has caused severe environmental pollution and resource waste. Therefore, the efficient disposal and recycling of sewage sludge has become key research focuses in the fields of energy and environment. Although hydrothermal liquefaction effectively converts sludge organics into biocrude, the resulting oil has high nitrogen, oxygen, and sulfur contents, and low carbon-to-hydrogen ratio, limiting its applications as a fuel. To address this issue, we investigate the upgrading of sludge-derived biocrude using acid-modified and metal-loaded ZSM-5 zeolites to enhance fuel quality. ZSM-5 was modified with HNO3 or CH3COOH, followed by loading with 5% Ni or Ru via impregnation. Four catalysts (Ni/HNO3/ZSM-5, Ru/HNO3/ZSM-5, Ni/CH3COOH/ZSM-5, and Ru/CH3COOH/ZSM-5) were characterized using SEM, BET, and XRD analyses. Biocrude upgrading experiments were conducted at 380 ℃ for 3 h with 0.005 g of catalyst. Product analysis included elemental composition, GC-MS, and FTIR. BET analysis revealed that the dealumination effect caused by acid treatment resulted in partial pore collapse, reducing the specific surface area, pore size, and pore volume of the catalyst. XRD analysis showed that the MFI topology of ZSM-5 was not significantly changed by acid treatment and metal loading. The prepared catalyst was then used in the biocrude upgrading experiment, and the results showed that Ru/HNO3/ZSM-5 achieved the highest upgraded oil yield at 36.1%, with hydrocarbon content increasing by 24.19% and acid content decreasing by 6.49% compared to raw biocrude. Elemental analysis showed that the carbon content increased, while nitrogen, oxygen, and sulfur contents decreased. GC-MS revealed a significant reduction in oxygenates and nitrogenous compounds, along with increased levels of esters and alkanes. FTIR confirmed reduced C=O and C—O bond intensities, indicating effective deoxygenation. Notably, HNO3-modified catalysts exhibited higher denitrogenation efficiency, whereas CH3COOH-modified catalysts enhanced desulfurization, likely due to their distinct pore structures and acidities. This work highlights the synergistic effects of acid type and metal selection on the catalytic performance of ZSM-5, with Ru/HNO3/ZSM-5 emerging as the optimal catalyst due to its balanced acidity, structural stability, and efficient metal dispersion. The upgraded oil exhibited fuel properties similar to those of biodiesel, with enhanced stability and reduced environmental risks. Acid modification and metal loading synergistically improved the catalytic performance of ZSM-5, offering a viable pathway for sludge-derived biofuel refinement. These findings provide a promising strategy for refining sludge-derived biofuels and advance the understanding of catalyst design principles for sustainable energy applications. Future research should focus on optimizing reaction parameters and evaluating long-term catalyst stability to facilitate industrial adoption. Close-