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.

Asphaltene-containing deposits formed on the CaF2 window induced by n-heptane flow in a microfluidic device have been investigated using an IR microscope and an imaging macro chamber (IMAC) with FPA detection. This is the first example of the ex situ infrared imaging of the deposits from crude oil formed under dynamic conditions of flocculant flow. It has been shown that fast aggregation of asphaltenes in n-heptane flow leads to the formation of deposit rich in heteroatom-containing functional groups: (О–Н, N–H, C=O, C–O, and S=O).

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