Teresa Ignasiak

Oxygen distribution and hydrogen bonding in Athabasca asphaltene

Abstract The oxygen distribution in the Athabasca asphaltene has been investigated. On the average, 75% of the oxygen is present in the form of hydroxyl groups. I.r. studies indicate that these hydroxyl groups exist almost entirely as hydrogen-bonded complexes which do not dissociate in carbon tetrachloride. The decrease in the molecular weight of the acetylated, methylated and silylated asphaltene suggests that the hydrogen bonding is intermolecular in character. The i.r. spectra of the asphaltene fractions extracted with polar solvents showed the presence of free OH, NH and carbonyl groups. The strong hydrogen-bonding properties of the Athabasca asphaltene were confirmed in i.r. measurements of the interaction with phenol, and molecular weight determinations of asphaltene 2,7-naphthalenediol and 4,4′-dihydroxy-3,3′-dimethyldiphenyl mixtures.

Reaction of Athabasca asphaltene with tetralin

Abstract Interaction of Athabasca asphaltene with a hydrogen-donating solvent such as tetralin at temperatures between 195 and 390 °C has been investigated. The reaction resulted in lowering the molecular weight of the treated asphaltene. At 390 °C, 50% of the original asphaltene was converted into pentane-solubles and the sulphur and oxygen contents were each depleted by about 40%. The results, which were interpreted in terms of thermal cleavage of sulphide bonds, are complementary to those obtained in the radical-ion electron-transfer reduction of the asphaltene with potassium in tetrahydrofuran. The negligible amount of coke formation at 390 °C proves the excellent stabilizing properties of tetralin in thermal reactions.

Separation and characterization of clay from Athabasca asphaltene

Abstract Athabasca bitumen separated from the associated mineral matter by Soxhlet extraction contains fine clay particles and inherent ash. Empirical relations have been developed to estimate the percentage of clay and inherent ash present in the asphaltene fraction which concentrates in large measure the mineral constituents present in the bitumen. The ash level, Y , of the asphaltenes is related to the weight per cent of clay, C t , by an expression of the form Y = 0.872 C t + 0.582. The ash level of the asphaltene fraction is also correlated with the infrared absorbance. A , at 1032 cm −1 which gives an approximate empirical relation of the form A = 0.0648 Y + 0.294. Greater accuracy at low ash levels can be achieved by measuring A at 1040 cm −1 above the base line drawn from 960 to 1140 cm −1 . This results in the equation A = 0.0709 Y + 0.0124 when a standard KBr pellet thickness of 0.833 mm and concentration of 2 mg asphaltene per 300 mg KBr is used. X-ray diffraction used to characterize the clay minerals shows decreasing crystallinity as the particle size diminishes. The infrared absorbance of this mineral matter indicates decreasing intensity of the band at 2930 cm −1 , associated with adsorbed and occluded organic matter, relative to the two characteristic clay bands at 3697 and 3620 cm −1 as the particle size decreases. Trace element analysis of the asphaltene inherent ash, by inductively coupled argon plasma, shows the major metallic constituents to be vanadium, nickel and iron with minor amounts of calcium, potassium, aluminium and sodium.

Preparative gel permeation chromatography of Athabasca asphaltene and the relative polymer-forming propensity of the fractions

Abstract Athabasca asphaltene has been separated according to molecular weight on Bio-Beads SX-1 gel. The number-average molecular weights of the five arbitrary fractions obtained by this fractionation range from 1200 to 17000. The chemical, spectral and thermal properties of the fractions are all similar but their polymer-forming propensities are markedly different. The significance of this latter property, which is defined in terms of the amount of CH2Cl2-insoluble material produced upon thermolysis at 300 °C, increases rapidly with increasing molecular weight of the fraction. In contrast the whole asphaltene does not form polymer at 300 °C under the same conditions and it is concluded that the chain propagating steps are terminated by a variety of inhibitors that are contained in the asphaltene agglomerate. During gel permeation chromatography separation the clay present in the asphaltene concentrates in the higher-molecular-weight fractions. This affinity to attract the clay is thought to be related to the physical, and not the chemical, properties of these higher-molecular-weight materials. The clay also exerts a catalytic effect on the polymerization of the asphaltene fractions which is most pronounced in the highest-molecular-weight fraction and gradually decreases with decreasing molecular weight.

Squalene in petroleum asphaltenes

Squalene, 2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexaene, a new biological marker, has been detected in various petroleum asphaltenes and their pyrolysis products. Since squalene is the most common triterpenoid in nature and the biological precursor of the important tetra- and pentacyclic triterpane markers, its detection in asphaltene suggests new ways for marker correlations.

Application of non-reductive alkylation in liquid ammonia to studies on macromolecular structure of coals and bitumen-derived asphaltene

Abstract The reaction of non-reductive ethylation of a coal anion generated in the presence of a strong base (sodium and/or potassium amides) in liquid ammonia is an efficient method for coal solubilization. Under the reaction conditions used, over 50 wt % of vitrinites separated from carboniferous bituminous coals became soluble in chloroform. The chloroform extracts were characterized by relatively low molecular weights ranging from 600 to 12000. At the same time, Athabasca oil sand asphaltene, which, under reductive conditions, degrades relatively easily to lower molecular weight species, did not display any molecular weight changes on reacting with amides in liquid ammonia. This fact stresses the non-destructive character of non-reductive alkylation. It appears, therefore, that the molecular weights of chloroform soluble portions of ethylated vitrinites reflect the molecular size of the original vitrinites. These results contradict the concept of coal having a highly crosslinked macro-molecular structure.

Carotenoids in petals of some perennial Medicago species

Abstract The carotenoid content in the petals of fourteen Medicago species was examined, together with eight species studied previously, caratenoids in all the known perennials of the genus are reported. The species can be arranged in relationship groups on the basis of their interfertility. No major carotenoid was species- or groupspecific; a few minor pigments, however, were group- or species-specific. The amount of carotenoids ranged from 7 μg/g dry matter in violet-flowered M. sativa to 2120 μg/g in brownish-yellow M. platycarpos. Xanthophylls constituted 76–99% of the total, with lutein as the major component. β-Carotene, lutein and flavoxanthin were ubiquitous in petals. In M sativa leaves β-carotene, lutein, violaxanthin and neoxanthin constituted 88% of the total. The xanthophylls were esterified in petals but not in leaves.