Effect of Vulcanization Temperature on the Activity of NiW/Al2O3 Catalyst

The influence of curing temperature on catalytic desulfurization, nitrogen and acid removal of NiW/Al2O3 hydrotreating catalyst during the curing tprocess was studied. The catalyst with incomplete curing was re⁃cured and its hydrogenation performance was studied. The structure of the vulcanized catalyst was characterized by physical adsorption (BET), X⁃ray diffraction (XRD) and X⁃ray photoelectron spectroscopy (XPS). The results showed that the sulfur content and degree of vulcanization on the catalyst increased with the increase of vulcanization temperature, and the carbon accumulation also increased, which led to the decrease of the specific surface area, pore volume and average pore size of the catalyst. After vulcanization, the active phase of the catalyst changed from low active W6+ and Ni2+ to high active W4+ and Ni-W-S phases. After revulcanization, the pore volume and average pore size of the catalyst decreased, while the specific surface area, sulfur and carbon contents increased. The increase in carbon deposition covered part of the active center and reduced the atomic ratio of W and Al on the catalyst surface, resulting in the aggregation of active metals in the vulcanized state and reduced the activity of the catalyst, indicating that the revulcanized catalyst was difficult to achieve complete vulcanized catalyst activity.