Influence of paramagnetic metals on the asphaltene aggregation behavior

Asphaltenes are complex and the most polar oil components with molecular weights estimated between 500 and 1000 Da which are soluble in benzene and toluene. The structure of asphaltenes and the elemental composition depend on origin, source rocks, depositional environment, diagenetic and thermal history. Asphaltenes contain condensed aromatic and saturated rings, aliphatic moieties, and some heteroatoms. They also contain metals, such as nickel, iron and vanadium. Asphaltenes may aggregate and precipitate during the downstream and upstream processes and cause many serious problems in production, refining and transportation. We will present here the results of aggregation study of asphaltenes isolated from the heavy crude oil (C) atmospheric (AR) and vacuum residues (VR). Asphaltenes were isolated from crude oil samples according to the standard method. The influence of metals, such as vanadium, nickel and iron on asphaltene aggregation have also been explored. DOSY NMR technique was applied to separate components from crude oils according to their diffusion coefficients. DOSY is a pseudo two-dimensional NMR experiment in which proton chemical shifts represent one dimension and translational diffusion coefficients represent another one. NMR signals of different species were separated according to their diffusion coefficients.