Effect of alumina and silica–alumina supported NiMo catalysts on the properties of asphaltenes during hydroprocessing of heavy petroleum

• Characterization of asphaltenes recovered at different temperatures (380–410 °C) using two different catalysts.
• Smaller size of asphaltenes and less concentrated in metals with NiMo/SiO2–Al2O3.
• Asphaltenes from NiMo/Al2O3 are more aromatic and concentrated in nitrogen.
• NiMo/SiO2–Al2O3 catalyst enhances metal removal in liquid products.

Asphaltenes were precipitated from a heavy residue and from its hydrotreated products at constant pressure, liquid-hourly space-velocity and hydrogen-to-oil ratio (100 kg/cm2, 0.25 h−1, and 5000 ft3/bbl, respectively). The effect of reaction temperature was studied in the range of 380–410 °C. The experiments were carried out in a two fixed-bed reactor unit. The first test used a NiMo/γ-Al2O3 catalyst and the second test a NiMo/SiO2–Al2O3 catalyst. It was observed that the molecules of asphaltenes formed after reaction from the NiMo/SiO2–Al2O3 catalyst are smaller in size and less concentrated in metals than those originated from NiMo/γ-Al2O3 catalyst, which are more concentrated in nitrogen and the asphaltenes structure is more aromatic. The NiMo/SiO2–Al2O3 catalyst enhances metal removal in liquid products.

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