Study of Asphaltenes Adsorption on Metallic Surface Using XPS and TOF-SIMS

X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) were used to characterize an adsorbed layer of four different asphaltenes on a stainless steel surface. Surface composition indicated different atomic concentrations of C, S, N, and O with similar chemical nature of their functional group as aromatic and aliphatic hydrocarbon. The presence of nitrogen compounds as pyrrolic and pyridinic, sulfur as thiophenic and carbon as carboxylic and hydrogenated (C−O) were confirmed by both XPS high-resolution binding energies and the high sensitive ToF-SIMS analysis of the detected negative fragments of nitrogen and sulfur. Depth profiling showed a carbidic nature on surface after surface sputtering with no surface sulfur and nitrogen. The optimum sputtering rate needs to be identified to allow studying and characterizing the asphaltene metallic interface.