Abstract
Asphaltenes, complex molecules in crude oil, cause significant challenges in oil production and refining due to their tendency to form agglomerates and precipitate. This study investigates the effectiveness of preparation method of metal oxide-based adsorbents (NiO and Fe(2)O(3)) in removing asphaltenes. Nanostructured NiO and Fe(2)O(3) xerogels and aerogels were produced through the Pechini-type and epoxide-derived sol - gel methods and employed for the adsorption of Ap1, a specific asphaltene extracted from Iranian crude oil. The nanomaterials were characterized by XRD, N(2) adsorption-desorption, FE-SEM, EDS, and FT-IR. The influence of synthesis parameters, including citric acid to metal precursor molar ratio, type of adsorbent, textural characteristics, adsorption temperature, sol-gel protocols, calcination temperatures, and drying conditions, on the adsorbent performance was systematically studied. The NiO(X-300) xerogel synthesized by the epoxide-derived sol - gel with calcination at 300 °C exhibited the highest asphaltene adsorption capacity (q = 558 mg/g) among all xerogels tested. This capacity was 102% and 87% higher than those achieved on optimized reference NiO(P-600) (q = 276 mg/g) and Fe(2)O(3)(P-600) (q = 298 mg/g) adsorbents prepared by the Pechini-type method, respectively. The textural properties of both NiO and Fe(2)O(3) materials were improved upon supercritical CO(2) drying of the epoxide-derived gels, leading to the nanostructured NiO(A-300) (q = 699 mg/g) aerogel with significantly higher (~ 135%) asphaltene adsorption capacity than Fe(2)O(3)(P-600). For the best aerogels, NiO(A-300) and Fe(2)O(3)(A-450), the adsorption isotherms and the kinetic data were best fitted by the Jovanovic and the Elovich models, respectively. Ap1 exhibited rapid adsorption onto NiO(A-300) and NiO(X-300), achieving equilibrium within 20 min. The adsorption process was demonstrably spontaneous and exothermic.