Synthesis and Characterization of Mixed–Metal Oxide Nanoparticles (CeNiO3, CeZrO4, CeCaO3) and Application in Adsorption and Catalytic Oxidation–Decomposition of Asphaltenes with Different Chemical Structures

Abstract

This study investigates the catalytic activity of mixed–metal oxide nanoparticles with different surface acidities on asphaltene adsorption followed by catalytic oxidation–decomposition. Three different types of mixed–metal oxide nanoparticles (CeNiO3, CeCaO3 and CeZrO4) were synthesized, and their size, structure, and acid properties were characterized by field–emission scanning electron microscopy (FE–SEM), energy-dispersive X-ray spectroscopy (EDX), the high–resolution transmission electron microscopy (HR-TEM), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurement and ammonia temperature-programmed desorption (NH3–TPD). Asphaltenes were extracted from two different Iranian crude oil samples (Kuh-e-Mond with API = 12.8 and Bangestan with API = 23.8). For all the three mixed-metal oxide nanoparticles, the isotherm data fitted well to the Langmuir model for both asphaltene types. Results showed that the adsorption capacity and affinity of nanoparticles decreases in the order of CeNiO3 > CeCaO3 > CeZrO4 for both types. Asphaltenes adsorbed over nanoparticles were subjected to oxidation–decomposition in a thermogravimetric analyzer (TGA) to study the catalytic effect of nanoparticles. Results showed the oxidation−decomposition temperature of asphaltene decreased about 155–180°C for Kuh-e-Mond asphaltene and 95–150°C for Bangestan asphaltene in the presence of nanoparticles, showing their catalytic effect.