The new on-column precipitation and redissolution separation technique developed at Western Research Institute (WRI) uses a continuous flow system to precipitate and redissolve various chemical species from oil. Although high-performance liquid chromatography (HPLC) equipment is used, the separation does not involve chromatographic adsorption mechanisms. Separations are conducted using a ground polytetrafluoroethylene (PTFE)-packed column, and they are strictly solubility-based. The asphaltene determinator method based on the new technique involves precipitation of asphaltene components from residua on the column using a heptane mobile phase. The precipitated material is redissolved at 30 °C in three steps using solvents of increasing solubility parameter: cyclohexane, toluene, and methylene chloride/methanol (98:2, v/v). This method has been optimized with rigorous daily quality control (QC) checks, and it is now in routine use. Several new applications for the method were demonstrated. These include monitoring pyrolysis severity during cracking reactions, determining total pericondensed aromatic (TPA) content, and providing profiles of the solubility distributions of the pericondensed aromatic components, including a new detailed characterization approach for asphaltene component molecules.
Current
asphalt binder production has significantly changed since
the Strategic Highway Research Program Superpave days as a result
of a number of economic, technical, and environmental reasons. Petroleum
sources and product demands have changed considerably, and as a result,
refining technologies have had to adapt as well as asphalt suppliers.
Blending of crude oils and refining streams as well as additive treatment
at various stages of extraction or refining by the addition of additives
is now common practice and is continuing to grow. Considering asphalt
as a straight-run vacuum residue from a single crude oil is now the
exception. Most of the aforementioned changes can enhance binder properties
when they are designed and controlled well. However, some of these
changes trigger concerns about the quality and consistency of the
delivered asphalt binder, especially as current specifications appear
insufficient to ensure satisfactory field performance of the end products.
The Asphalt Industry Research Consortium (AIRC) was launched by the
Western Research Institute in 2015 to help industrial partners evolve
with the changing asphalt binder landscape. This study provides select
insights produced from the eight partners who helped launch the AIRC
program to perform chemomechanical characterization of 52 asphalt
binders from around the world. In this study, multiple techniques
were instrumental to diagnose various refining processes, compositions,
and binder modifiers. These techniques include rheology–Black
space analysis, saturates, aromatics, resins–asphaltene Determinator (SAR-ADTM), Fourier transform infrared spectroscopy, Waxphaltene Determinator (WD),
differential scanning calorimetry, and gel permeation chromatography/size-exclusion
chromatography. This paper presents the potential of these techniques
for diagnosing air-blown, high-asphaltene-content, high-wax-content,
visbroken, styrene–butadiene–styrene-modified, ethylene–vinyl
acetate-modified, and paraffin-modified binders and blends. The authors
also believe that well-formulated and compatible blends of any of
these production or modification methods may perform well in the field.
Links are made between chemically based techniques and understanding
how these are manifested in the physical/mechanical properties of
the materials.
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