A Study on the Adsorption and Catalytic Oxidation of Asphaltene onto Nanoparticles

The use of nanoparticles, including metal oxide surfaces, as asphaltene adsorbents is a potential method of removing and/or upgrading asphaltenes. The adsorption of two asphaltene types, extracted from two types of Iranian crude oil, onto nanoparticles (TiO2, SiO2, and Al2O3) are assessed and the thermal behavior of the adsorbed asphaltenes is examined under an oxidizing atmosphere through thermogravimetric and differential scanning calorimetry (TG/DSC) analyses. The extracted asphaltenes are characterized through the X-ray diffraction technique, and adsorption isotherms are measured through UV-Vis spectrophotometry of the asphaltene-toluene model solutions. The isotherm data of all the nanoparticles are adequately fitted by the Langmuir model, indicating that asphaltenes form monolayer coverage on solids surface sites. The adsorption capacities of asphaltenes onto the metal oxides follow the order of Al2O3> TiO2> SiO2. The results indicate that asphaltene with high aromaticity has more adsorption affinity, indicating the effect of the chemical structural of the asphaltenes. The results of asphaltene oxidation tests reveal that the presence of nanoparticles leads to a decrease in oxidation temperature (~100 °C) and activation energy. The effects of nanoparticles on asphaltene oxidation are catalytic.