As environmental awareness grows, hydrodesulfurization (HDS) catalysts have become crucial in petroleum refining, yet their use results in oil-laden waste, poses environmental risks, and complicates subsequent treatment. Efficient oil removal is thus critical for processing spent catalysts. This study systematically compares three de-oiling methods, extraction, chemical thermal washing, and pyrolysis, to identify the optimal de-oiling method. In the experiments, extraction achieves a 94.12% oil removal rate at a liquid-to-solid ratio of 10 mL/g, a temperature of 45 °C, and a time of 60 min, maintaining around 90% efficiency after five cycles of solvent recovery. Chemical thermal washing achieves an oil removal rate of 96.26% after 4 h at 90 °C, with 0.15 wt.% SDS, 3.0 wt.% NaOH, and a liquid-to-solid ratio of 10 mL/g. The heavy oil emulsion is then decomposed with 4% CuO and 5% H₂O₂. The pyrolysis method removes 96.19% of oil at 600 °C in 60 min. While the extraction and chemical thermal washing methods are effective, they produce wastewater, raising environmental concerns. In contrast, the pyrolysis method is more environmentally friendly. SEM, EDS, and FT-IR analyses show that after oil removal, the metal structures on the alumina support of the spent HDS catalyst are clearly exposed, facilitating the subsequent recovery of valuable metals.

Al-2at.% Nd alloy with a gradient cooling rate was prepared using a wedge-shaped mold in a vacuum environment. The relationship between gradient cooling behavior and the microstructure and properties of the Al-2at.% Nd alloy was investigated. The stability of the Al₁₁Nd₃ phase and the mechanical properties were confirmed through first-principles calculations. The results indicated that as the cooling rate decreased, the transformation of grain morphology in Al-2at.% Nd occurred as follows: a mixture of columnar grains and equiaxed grains→equiaxed grains. The grain size of the alloy increased. Discontinuous skeletal eutectic phases, α-Al and Al₁₁Nd₃, formed within the alloy, resulting in a reduction in the number of phase boundaries and grain boundaries. The hardness of the alloy decreased by 25.53%, and this pattern of change closely aligned with the calculated results.

This research focuses on the synergistic effect of the cooling rate and solute neodymium (Nd) content on the microstructure and physical properties of aluminum-neodymium (Al-Nd) alloys. The results indicate that the cooling rate has a significant impact on the grain morphology, size, and morphology of eutectic Al₁₁Nd₃ in the alloy. As the cooling rate decreases, the grains transform from columnar crystals to equiaxed crystals, exhibiting different distribution characteristics in various regions, and the eutectic transforms from skeletal to lamellar and then to acicular. The Nd content affects the eutectic growth and solubility, reaching the maximum solubility at 11 wt.% Nd. Due to the longer diffusion time of Nd atoms in the slow-cooling region and the formation of compounds, the lattice constant in the slow-cooling region is larger. In terms of physical properties, the hardness and electrical conductivity of the alloy are inversely related. The hardness increases with an increases of the cooling rate and Nd content, which is attributed to grain refinement and solid solution strengthening, while the electrical conductivity decreases. These findings are of important theoretical and practical significance for optimizing the performance and application of Al-Nd alloys.

As environmental awareness grows, hydrodesulfurization (HDS) catalysts have become crucial in petroleum refining, yet their use results in oil-laden waste that poses environment risks and complicates subsequent treatment. Efficient oil removal is thus critical for processing spent catalysts. This study systematically compares three de-oiling methods: extraction, chemical thermal washing, and pyrolysis, to identify the optimal de-oiling method. In the experiments, the extraction achieves 94.12% oil removal rate at a liquid-to-solid ratio of 10 mL/g and 45℃ in 60 minutes, maintaining around 90% efficiency after five cycles of solvent recovery. The chemical thermal washing achieves oil removal rate of 96.26% after 4 hours at 90℃, with 0.15 wt.% SDS, 3.0 wt.% NaOH, and a liquid-to-solid ratio of 10 mL/g. The heavy oil emulsion is then decomposed with 4% CuO and 5% H2O2. The pyrolysis method removes 96.19% of oil at 600℃ in 60 minutes. While the extraction and chemical thermal washing methods are effective, they produce wastewater, raising environmental concerns. In contrast, the pyrolysis method is more environmentally friendly. SEM, EDS, and FT-IR analyses show that after oil removal, the metal structures on the alumina support of the spent HDS catalyst are clearly exposed, facilitating the subsequent recovery of valuable metals.