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Abstract

Crude oil and oil products are affected by fouling processes during production,
transport, processing and storage. Fouling processes can be of physical, chemical or
biological nature, with physical fouling usually resulting from heat exposure, chemical
fouling being long term changes in the composition as a result of reactions within the
oil product and biological fouling being the result of microbial activity.
In this study, the influence of the factors air, water, sand, copper and iron on
chemical fouling processes has been examined. Experiments were performed with a
light oil fraction at temperatures of 150, 300 and 450 °C for 72 hours to gain insight
into the kinetics of the reaction as well.
Samples were analysed using a prototype Orbitrap Elite for high resolution mass
spectrometry of liquid fouling products and transmission electron microscopy for solid
deposits formed as a result of the reactions.
The experiments performed at 150 °C did not result in deposit formation and showed
small compositional changes towards higher complexity in the mass spectrometric
analysis.
At 300 °C, in some reactions performed in presence of air and iron sulphate, deposit
formation occurred. Only minimal differences between experiments performed under
inert or non-inert conditions as well as in presence of water were detected.
The presence of copper or copper sulphate resulted in an increase of nitrogen
containing compounds, while the presence of iron and iron sulphate led to an
increase of oxidized compounds. The main constituents of the sample were
hydrocarbons without heteroatoms.
At a temperature of 450 °C, deposit formation has been observed in all experiments.
Reactions in the absence of metals resulted in a slight increase of oxidized species,
the presence of iron led to a stronger increase of oxidized constituents. Copper and
copper sulphate led to the formation of oxidized molecules containing up to 5
nitrogen atoms.
The complexity of molecules in all classes increased with rising temperature. While
most processes observed in the mass spectrometric analysis took part in the
heteroatom containing classes, the majority of the constituents can be found in the
heteroatom free hydrocarbons. Only two samples were examined by electron
microscopy, showing the formation of graphene like layers in both measurements.
The presence of iron led to the formation of multi walled nanotubes.