In Situ FTIR Spectroscopic Imaging of Asphaltene Deposition from Crude Oil under n-Heptane and Acetone Flows

Abstract

Asphaltene deposition from crude oil, induced by n-heptane and acetone flows in a microfluidic device, was studied by optical and FTIR spectroscopic imaging techniques in situ. It was found that n-heptane and acetone penetrate crude oil in completely different ways, which is responsible for the formation of deposits with different structures and chemical compositions. The contact of the n-heptane flow with crude oil leads to fast aggregation of asphaltenes at the interface, resulting in the formation of a compact deposit fixed to the surface. Subsequent slow diffusion of n-heptane into crude oil causes asphaltene aggregation and precipitation of loose deposits. In the case of acetone, the flocculant diffuses (faster than n-heptane) into crude oil, which results in removal of its soluble components and in the formation of deposits appearing as strips as well. The distribution of the functional groups (–OH(NH), CH2–CH3, C=O, C–O, S=O) in the deposits is spatially heterogeneous. The asphaltenes deposits formed at the flocculant-crude oil interface are richer in the functional groups than those formed during diffusion. No carbonyl groups were revealed in the deposits formed in the acetone flow, while oxygen-containing groups such as –OH(NH) and S=O were present, which was an unusual result.

Resin–Paraffin Aggregation Processes in Waxy Oil Revealed by Vanadyl Porphyrin Spin Probe

“…Currently, a number of methods are being developed that allow obtaining information about the structure, dynamics, and local environment of heavy components in oils at the atomic and molecular level, among which spectroscopic (FTIR spectroscopy, ,, small-angle scattering (SAS), − and dynamic light scattering (DLS)) , and resonance (NMR and electron spin resonance (ESR)) ,− methods can be distinguished. Each of these methods has advantages and limitations.…”