LIQUID CHROMATOGRAPHIC SEPARATIONS AS A BASIS FOR IMPROVING ASPHALT COMPOSITION-PHYSICAL PROPERTY CORRELATIONS

ABSTRACT

It is widely known that asphalts yielding similar results in standard tests like penetration may in fact exhibit significantly different performance with respect to product manufacturing, application, or durability. Thus, a need exists for more definitive testing, especially with respect to defining the chemical composition of asphalt. Direct spectroscopic analysis of asphalt is difficult because of its compositional complexity, high degree of association between compounds present, and high, overall average molecular weight/boiling range. Hence, prior liquid chromatographic separation into compound classes or types can greatly enhance the level of information obtainable from spectroscopic methods, as well as provide information on types and quantities of compounds present. The scheme discussed involves initial separation into acid, base, and neutral types using development of routine test methods to significantly higher levels of sophistication than those currently available.     

STUDIES ON LARGE CRUDE OIL ALKANES. II. ISOLATION AND CHARACTERIZATION OF AROMATIC WAXES AND WAXY ASPHALTENES.

ABSTRACT

Isolation of very large alkane components as described in the first paper within this series, fail in some cases. This work describes two non-routine isolation procedures applied to two different non-typical petroleum fractions. The first one comprises a chromatographic approach applied for the separation of alkanes from alkylaromatic compounds derived from paving asphalt waxes. The second separation procedure was developed for the isolation of alkane fractions associated with asphaltenes that precipitated during long crude oil storage periods, resulting in highly insoluble organic composites

In the first case, the isolated fractions were characterized by spectroscopic and chromatographic methods. The evidence showed that long chain naphtheno-aromatic molecules behave like waxy asphalt components, which interact by unusual mechanisms with solid sorbents. Their chromatographic behavior was found to be between typical alkanes and typical aromatics. This behavior is caused by the simultaneous presence of three functionalities

The second sample type was characterized by spectroscopic methods only. The results permitted to assess that the waxy composite from crude oil tank sediments precipitated selectively, including highly aromatic and long alkyl chain asphaltenes as well as very large n-alkanes.     

STUDIES ON LARGE CRUDE OIL ALKANES. II. ISOLATION AND CHARACTERIZATION OF AROMATIC WAXES AND WAXY ASPHALTENES.

Isolation of very large alkane components as described in the first paper within this series, fail in some cases. This work describes two non-routine isolation procedures applied to two different non-typical petroleum fractions. The first one comprises a chromatographic approach applied for the separation of alkanes from alkylaromatic compounds derived from paving asphalt waxes. The second separation procedure was developed for the isolation of alkane fractions associated with asphaltenes that precipitated during long crude oil storage periods, resulting in highly insoluble organic composites

In the first case, the isolated fractions were characterized by spectroscopic and chromatographic methods. The evidence showed that long chain naphtheno-aromatic molecules behave like waxy asphalt components, which interact by unusual mechanisms with solid sorbents. Their chromatographic behavior was found to be between typical alkanes and typical aromatics. This behavior is caused by the simultaneous presence of three functionalities

The second sample type was characterized by spectroscopic methods only. The results permitted to assess that the waxy composite from crude oil tank sediments precipitated selectively, including highly aromatic and long alkyl chain asphaltenes as well as very large n-alkanes.     

SUPER CRITICAL FLUID EXTRACTION AS ONE OF THE MOST EFFECTIVE METHODS FOR SEPARATION AND ANALYSIS OF ASPHALT

This paper briefly reviews several chromatographic separation methods for analysis of asphalt, and recommends the supercritical fluid extraction as one of the most effective methods for separation and analysis of asphalt. Several different kinds of asphalt have been used as samples. The experimental results are discussed.     

SUPER CRITICAL FLUID EXTRACTION AS ONE OF THE MOST EFFECTIVE METHODS FOR SEPARATION AND ANALYSIS OF ASPHALT

ABSTRACT

This paper briefly reviews several chromatographic separation methods for analysis of asphalt, and recommends the supercritical fluid extraction as one of the most effective methods for separation and analysis of asphalt. Several different kinds of asphalt have been used as samples. The experimental results are discussed.     

废胶粉改性沥青存储稳定性能试验研究

研究在分析橡胶沥青改性机理与存储稳定性关系的基础上,总结提高橡胶沥青存储稳定性的思路和方法,提出优选后的实验室内制备橡胶沥青的高速剪切工艺,并通过橡胶沥青离析试验法和红外光谱测试法等一系列试验方法,分析橡胶粉的粒度、用量以及改性剂等因素对橡胶沥青存储稳定性能的影响。     

INFRARED STUDY OF THE AGING OF ASPHALTS IN CONTACT WITH AGGREGATES

ABSTRACT

The purpose of this work was to identify chemical compound types produced at or near the asphalt/aggregate interface during oxidative aging. Diffuse reflectance infrared Fourier transform (DRIFT) spectrometry was used to analyse samples of asphalt that had been oxidatively aged in contact with aggregate for various periods of time. Aging products were studied as a function of time, distance from the aggregate surface, asphalt composition, and aggregate composition. Three compound types were observed to form upon aging—sulfoxides, ketones, and carboxylic acids. All three compounds types are thought to cause hardening and cracking of asphalts. The composition of the virgin asphalt was a key factor in determining the kind and amounts of aging products formed. The amount of products formed was also related to aging time. Evidence for the concentration of any one aging product on or near the asphalt/aggregate interface was not found     

MODEL STUDIES AND INTERPRETIVE REVIEW OF THE COMPETITIVE ADSORPTION AND WATER DISPLACEMENT OF PETROLEUM ASPHALT CHEMICAL FUNCTIONALITIES ON MINERAL AGGREGATE SURFACES

Moisture-induced damage in petroleum asphalt pavements, which results in a loss of pavement tensile strength, is a significant contributor to pavement performance problems such as rutting, shoving, flushing and cracking. Results of the present study provide fundamental information on some of the chemistries of moisture-induced damage. Model compounds containing polar chemical functional group types found in asphalts were used to simulate the adsorption-water displacement characteristics of asphalt molecules on mineral aggregate surfaces. A comparative and interpretative discussion of the model compound studies and earlier studies on actual asphalt-aggregate mixtures is presented. Carboxylic acids were confirmed as the functional type most strongly adsorbed on most mineral aggregate surfaces; however, they were also the functional type most easily water displaced. Pyridine-type functionality similar to that found in asphalts reduced the sensitivity of asphalt-aggregate mixtures to moisture damage. Results suggest that prior treatment of aggregates with antistripping agents rather than their prior addition to the asphalts should improve the moisture resistance of mixtures. The reaction of carboxylic acids with aggregate surfaces prior to the reaction of the aggregate surfaces with pyridine-type functionality greatly increased the sensitivity of the pyridine types to displacement by water. Also, the reaction of pyridine with carboxylic acid functionalities prior to their adsorption on aggregate surfaces also increased their sensitivity to water displacement. Results of the model compound studies provided further interpretation of the results of earlier fundamental studies on the adsorption and water displacement characteristics of actual asphalt components from aggregates typically used in paving mixtures. Results are interpreted with regard to their usefulness in finding pragmatic solutions to pavement pavement moisture damage problems. Further needed research is also suggested.     

INVESTIGATION AND EVALUATION OF PETROLEUM ASPHALT AGING PROPERTY ON OXYGEN ABSORPTION BY INVERSE GAS LIQUID CHROMATOGRAPHY

The aging mechanisms and performances on oxygen absorption of ten petroleum asphalts were studied and evaluated by the inverse gas liquid chromatography with the Aging Comprehensive Index, the Aging Subtraction Number, the Aging Total Area and the Aging Character Factor methods based on the changes of the retention coefficients of analytical compounds in the petroleum asphalt chromatographic column during continuous aging caused by oxygen absorption under an oxygen flow rate of 15∼30 ml/min at 140°C, after the inert support was evenly coated with toluene-dissolved petroleum asphalt and packed into the chromatographic column. The relative polarity of petroleum asphalt and the retention coefficients of analytical compounds increase after absorbing oxygen and the changes of the retention coefficients of the oxygen-containing analytical compounds, especially phenol are evidently greater than those of the nitrogen and sulfur-containing and aromatic analytical compounds. There are obvious differences between the retention coefficients of analytical compounds in the petroleum asphalt columns from different sources and between their changes with the aging on oxygen absorption. The repeated determinations of these evaluation methods show that the standard deviations are less than 1.63 and the variable coefficients under 0.2. The test data are found.to be reliable by Grubhs examination at 95% confidence level. Of the four evaluation methods the Aging Subtraction Number method is the most simple and convenient in operation and takes least time in evaluation.     

Investigation and Improvement of Storage Stability of SBS Modified Asphalt

Three different types of storage stability of SBS modified asphalts were investigated by hot storage test. It's found that during hot storage the performance of SBS modified asphalt deteriorated although phase separation didn't happen. Mechanism of storage stability of SBS modified asphalt was discussed. The different hot storage stability of three SBS modified asphalts could be well interpreted with the interface layer principle. Based on the interface layer principle, a new way that asphalt was chemically modified by SBS was put forward to improve hot storage stability and other using performances. The results indicated that the asphalt chemically modified by SBS had good hot storage stability and other using performances were significantly improved. Fluorescence microscopy was used to study SBS modified asphalt phase morphology, and the SBS chemically modified asphalt showed two interlocked continuous phases.