No abstract

A new fully automated saturates, aromatics, resins, and asphaltenes (SARA) separation for asphalt bitumen and petroleum residua has been developed and optimized. This system performs separations on 2 mg sample portions utilizing four columns packed with different stationary phases. The direction of solvent flow is controlled by automated four-port and six-port switching valves. The asphaltenes precipitate out of solution within a ground polytetrafluoroethylene (PTFE) packed column in an excess of heptane. The heptane-soluble maltenes pass through glass beads, aminopropyl bonded silica, and activated silica packed columns where chromatographic separation of the maltenes occurs. The saturates material is not retained, and it passes through all three adsorption columns. The more highly polar and pericondensed aromatic resins are retained by the glass bead column, and the remaining resins are adsorbed on the aminopropyl silica column. The glass bead column minimizes irreversible adsorption of resins by preventing the more polar resins from reaching the aminopropyl silica column. The aromatics are adsorbed on the activated silica column. In the next step of the method, the asphaltenes are selectively redissolved from the PTFE column with cyclohexane, toluene, and methylene chloride:methanol (98:2 v/v), yielding highly alkyl substituted asphaltene components, less alkyl substituted pericondensed aromatic asphaltenes, and precoke pericondensed aromatic asphaltenes, respectively. In the final steps, the aromatics and resins are eluted from their respective columns. An evaporative light scattering detector is used to quantify the amounts of each fraction, and an optical absorbance detector set at 500 nm records the relative amounts of pericondensed aromatic material with extended π systems that absorb visible light contained within the eluting fractions. The entire system is regenerated to the original column activity with a toluene and heptane solvent flush sequence, prior to the next injection. An automated separation is performed every four hours compared to several days for a corresponding gravimetric manual method.

This thesis has been read by each member of the thesis committee and has been found to be satisfactory regarding content, English usage, format, citations, bibliographic style, and consistency, and is ready for submission to the College of Graduate Studies.

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.

The automated Asphaltene Determinator coupled with saturates, aromatics, and resins (SAR−AD) separation is a powerful characterization tool initially designed for the rapid and repeatable analysis of asphalt bitumen and petroleum residua. By virtue of the evaporative light scattering detector (ELSD) and the fact that saturates and a portion of aromatics do not contain chromophores, making them undetectable in the 500 or 700 nm detectors, the complete quantification of petroleum fractions by this method is somewhat restricted to samples that do not contain a significant amount of volatiles. Crude oils can contain more than 70% of volatile material, which is not detected by the ELSD. To overcome the SAR−AD volatile limitation, a quantitative vacuum distillation method was developed to capture the volatiles and produce unaltered residua that does not lose volatiles in the ELSD. To complete the characterization, the volatiles are analyzed for their saturate, aromatic, and reactive olefin contents by proton nuclear magnetic resonance spectroscopy ( 1 H NMR). The data from these two methods are combined in the form of a modified colloidal instability index to give a more complete profile of the original whole crude oils.