Abstract
Predicting the compatibility of crude oils from different streams can be done by applying models that use the solubility parameter of the oils. The approximate solubility parameter value of a given crude oil can be calculated by observing the asphaltene precipitation onset caused by titration with n-heptane. For oils whose precipitation onset is not well defined, a small quantity of another petroleum with easily detected onset can be added. It would be ideal to always use the same petroleum for this addition, but this is obviously not possible. The purpose of this study was to replace this petroleum by a synthetic molecule. Therefore, molecules were selected and synthesized to obtain structures containing aromatic ring, aliphatic chain and heteroatom. The molecules were characterized by infrared spectrometry, gas chromatography-mass spectrometry, elemental analysis and gel permeation chromatography. Nitrated cardanol, polycardanol obtained by addition polymerization (PCA) and nitrated PCA presented the desired behavior. However, the concentration of the molecule in toluene needs to be adjusted in function of the characteristics of the petroleum. For a particular crude oil, when model molecule present solubility in a wider solubility parameter range, lower concentration will require to identify the precipitation onset of that oil.
Highlights
Crude oils from different streams are typically mixed before primary processing at refineries
The experimental determination of δ is not trivial, so the approximation denoted by equation 1 has been used, assuming the solubility parameter of the mixture equal to 16.35 MPa1/2.17 This approximation assumes that the asphaltene precipitation occurs at a fixed point of 16.35 MPa1/2
To obtain molecules that could be added to a crude oil sample to improve the identification of the asphaltenes precipitation onset by the procedure of titration with n-heptane and detection by near-infrared spectroscopy (NIR), as can be obtained by adding an oil sample defined as a standard (APS), we synthesized structures containing aromatic rings and hydrocarbon chains and/or hydrophilic groups
Summary
Crude oils from different streams are typically mixed before primary processing at refineries. Incompatibility between these oils can lead to precipitation of asphaltenes, which is undesirable.[1,2,3,4,5,6,7] Asphaltenes can be defined, based on their structure, as molecules with relatively high molar mass composed of condensed aromatic rings, cyclic structures, and a small number of aliphatic hydrocarbon chains, as well as functional groups (such as carbonyl, amine and hydroxyl) and elements (such as sulfur, nickel and vanadium).
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