Determination of sulfur in asphalts by selective oxidation and photoelectron spectroscopy for chemical analysis

“…Pyrolysis studies of asphaltenes also suggest that S is present predominantly in two forms, sulfide and thiophenic. Approximately 25% of the total sulfur in asphaltene is present as a (saturated) cyclic or alkyl sulfide and is converted to H 2 S during pyrolysis. ,, In addition, thiophene, benzothiophene, and dibenzothiophene, as well as their alkyl derivatives, are present in the liquid products. − During pyrolysis, however, approximately, 35% of the asphaltene S is recovered in the coke product, thus, little is known about the structure of these heteroatom molecules.…”

Section: Introductionmentioning

confidence: 99%

Subfractionation and Characterization of Mayan Asphaltene

et al. 1998

View full text Add to dashboard Cite

Mayan crude, residuum, and hydrocracked asphaltenes have been separated into two fractions by extended Soxhlet extraction in n-heptane. Although the solubility, composition, and molecular structures differ slightly, the greatest difference between the two asphaltene fractions is the degree to which they associate in solution. The vapor-phase osmometry molecular weight, molecular size by size-exclusion chromatography, and small-angle neutron scattering indicate that approximately 25% of Mayan asphaltene is not highly associated in aromatic solvents and, thus, is noncolloidal. By contrast, the remaining asphaltene forms large, rodlike colloidal particles in solution and has a higher apparent molecular weight. Although laser desorption mass spectrometry indicates that the molecular weight of the individual molecules in maltenes and asphaltenes is not very different, high-resolution mass spectrometry indicates that the size of the aromatic core of asphaltenes is significantly larger than those in maltenes. Furthermore, the tendency of the residuum fractions to form coke during thermal cracking is likely related to the size of the largest polyaromatic rings.

show abstract

“…XPS analysis can obtain information of the state and environment of atoms in the sample, which can be further analyzed for information of the surface structure. Such powerful ability of XPS is particularly useful for studying the oxidative aging of asphalt binders, − for which a sufficiently thin sample (e.g., a few μms) can be easily prepared and oxidized with uniform oxidation throughout the entire depth of the sample in a relatively short period of time (e.g., 2 h at 130 °C) . The XPS technique was used in this study to validate the bulk asphalt model by determining and comparing the amounts of generated functional groups before and after asphalt oxidation.…”

Section: Validation Of the Atomistic Modelmentioning

confidence: 99%

“…The slight difference between the experimental results and numerical predictions might come from the machine or operation errors related to XPS. In preparing samples for XPS analysis, the asphalt samples were vacuumed at the room temperature following the procedure established by Ruiz et al 37 The samples (in dry powders) were then pressed onto a piece of thin indium foil (0.1 mm thick) as the sample substrate. Graphite tape was not used as sample substrate for the carbon-based asphalt to avoid peaks from the graphite tape, which would otherwise add to the carbon peak, potentially skewing or overwhelming the data in XPS spectrum.…”

Section: ■ Quantum Chemistry Perspective Of Asphalt Oxidationmentioning

confidence: 99%

Quantum-Chemistry Study of Asphalt Oxidative Aging: An XPS-Aided Analysis

Pan

Yang

Lloyd

2012

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

Asphalt derived from crude oil (or petroleum) is an important base organic material for many industrial purposes. Oxidative hardening occurs throughout the service life of asphalt materials, which could significantly change the desired physicochemical properties. The study of asphalt oxidative hardening has thus far been focused on the changes in the physical properties, mainly the viscosity and ductility of bulk asphalt. Such phenomenological approaches meet the direct engineering needs, however do not help understand the fundamental physicochemical mechanisms of asphalt hardening. From this standpoint, this paper aims at exploring the chemical basis of asphalt oxidative hardening by establishing an ab initio quantum chemistry (QC) based physicochemical environment, in which the possible chemical reactions between asphalt ingredients and oxygen, as well as the incurred changes in their physical behavior, can be readily studied. X-ray photoelectron spectroscopy (XPS) was used to validate the bulk asphalt model, of which the results showed high agreement to the model predictions, and thereby prove the validity of the QC-based models developed for studying the oxidative behavior of general asphalt materials.

show abstract

Determination of sulfur in asphalts by selective oxidation and photoelectron spectroscopy for chemical analysis

Cited by 33 publications

References 8 publications

Supercritical fluid fractionation and detailed characterization of the sulfur heterocycles in a catalytically cracked petroleum vacuum residue

Supercritical fluid fractionation and detailed characterization of the sulfur heterocycles in a catalytically cracked petroleum vacuum residue

Subfractionation and Characterization of Mayan Asphaltene

Quantum-Chemistry Study of Asphalt Oxidative Aging: An XPS-Aided Analysis

Contact Info

Product

Resources

About