Bitumen sulfur content

Trinidad asphalt has a relatively uniform composition of 29% water and gas, 39% bitumen soluble in carbon disulfide, 27% mineral matter on ignition, and 5% bitumen that remains adsorbed on the mineral matter. Refining is essentially a process of dehydration by heating the cmde asphalt to ca 165°C. The refined product averages 36% mineral ash with a penetration at 25°C of about 2 (0.2 mm), a softening point (ring and ball method) of 99°C, a flash point (Cleveland open cup) of 254°C, a sulfur content of 3.3%, and a saponification value of 45 mg KOH/g. The mineral matter typically contains... 

In addition to attempts to define petroleum, heavy oil, bitumen, and residua, there have been several attempts to classify these materials by the use of properties such as API gravity, sulfur content, or viscosity (Speight, 1999). However, any attempt to classify petroleum, heavy oil, and bitumen on the basis of a single property is no longer sufficient to define the nature and properties of petroleum and petroleum-related materials, perhaps even being an exercise in futility. 

The sulfur content varies from about 0.1 wt% to about 3 wt% for the more conventional crude oils to as much as 5 to 6% for heavy oil and bitumen. Depending on the sulfur content of the crude oil feedstock, residua, may be of the same order or even have a substantially higher sulfur content. 

The sulfur content of petroleum varies from less than 0.05 to more than 14 wt% but generally falls in the range 1 to 4 wt%. Petroleum with less than 1 wt% sulfur is referred to as low-sulfur, and that with more than 1 wt% sulfur is referred to as high-sulfur. The refining industry considers heavy oils, residua, and bitumen to be high-sulfur feedstocks. Hence they are the focus of many conversion and desulfurization scenarios. 

Sulfur content in crude oils and natural bitumens varies from less than 0.05 to more than 14 weight percent, but few commercially produced crude oils exceed 4% sulfur. Tissot and Welte (25) show a frequency distribution of crude oils based on over 9,000 samples and report the average sulfur content as 0.65%. The distribution is clearly bimodal with a minimum at about 1% sulfur. Oils with less than 1% sulfur are classified as low-sulfur, and those above 1% as high-sulfur. In general, high-sulfur oils are derived from carbonate or carbonate-evaporite rock sequences whereas low-sulfur oils are derived largely from clay-rich clastic sequences f25-26.28-29). 

The concentrations of the total alkylthiophenes (except thiophene hopanoids) in the bitumens show a depth profile somewhat similar to that of the total sulfur content (cf. Figures 6a and Id). The high concentrations of alkylthiophenes in Facies B compared to A and C are consistent with the proposed incorporation of inorganic sulfur species into specific funtionalised lipids in anoxic marine environments (6-12). 

Figure 2 Sulfur contents of residual kerogens, bitumens and...

The conventional approach to asphalt analysis has been to extract the bitumen with an organic solvent and then to characterize bitumen and minerals separately. Sulfur content and melting point are commonly measured properties of bitumen. Minerals are generally screened and then subjected to simple quantitative tests. Measurement of weight loss on ignition helps to distinguish between calcium carbonate, which loses... 

Analyses of a series of asphalts from layers spanning more than a millennium at the single site of Eshunna are presented in Table III. All nine samples were analyzed by Forbes and the seven largest by Nellen-steyn (4) as well. The asphalts averaged 19-36% bitumen (a little less than in Table II) and about 10% vegetal matter. Sulfur contents of the bitumens were more consistent than in Table II with only two exceptions for Forbes (D and H) and one for Nellensteyn (5), all were 7.3 1.0%. Minerals content of the bitumens was 5.5 2.5%. The ratio of carbonate to silica was 2 1 to 4 1 except for samples A (and 1) and C (and 3) in... 

These analyses support a significant series of inferences with respect to the sources of asphalt. DiflEerences in asphalt composition, mineral color, and especially sulfur content of the bitumen indicate that lowland and highland asphalts were not derived from the same raw materials. Mesopotamian asphalts simply do not match those found in the usually earlier settlements along the Tigris tributaries. Presumably new sources upstream along the Euphrates were used. They would certainly be more convenient than overland shipment from the east. Lesser diflEerences... 

Comparison of Heavy Oils with Bitumen. Many of the analyses indicate that the heavy oils are very similar to the original bitumen. Hydrogen-to-carbon atomic ratios are in the range of 1.65-1.69, which is similar to the bitumen (1.64). Nitrogen and sulfur contents are similar to values for the bitumen (see Table I). Nickel concentrations of heavy oils are slightly lower than the concentration in the bitumen. Vanadium analyses for heavy oils range from lower than to higher than vanadium in the bitumen. 

The heavy oil collected on the fourth day contains more low-boiling components than the other heavy oils. Vanadium and nickel analyses are lower than for bitumen. The hydrogen-to-carbon ratio and nitrogen and sulfur contents are similar to values for bitumen. IR and NMR spectra indicate that this sample has much greater aromatic-olefinic content than the other heavy oils. The IR spectrum has weak bands for olefins but a strong aromatic band at 1600 cmThe integral for the NMR spectrum indicates 35% aromatic-olefinic content and 65%... 

Data calculated from that for composite synthetic crude obtained after coking and Unifining of extracted bitumen, from Bachman and Stormont [2]. Before Unifining (hydrogenation) mean density of the composite stream would be somewhat higher, and sulfur content would be about 3%. Proportions of distillate components are approximate carbon content quoted is the coke residue on pyrolysis of bitumen. 

In the more localized context of the Athabasca deposit, inconsistencies arise presumably because of the lack of mobility of the bitumen at formation temperature (approximately 4°C, 39°F). For example, the proportion of bitumen in the tar sand increases with depth within the formation. Furthermore, the proportion of the nonvolatile asphaltenes or the nonvolatile asphaltic fraction (asphaltenes plus resins) in the bitumen also increases with depth within the formation that leads to reduced yields of distillate from the bitumen obtained from deeper parts of the formation. In keeping with the concept of higher proportions of asphaltic fraction (asphaltenes plus resins), variations (horizontal and vertical) in bitumen properties have been noted previously, as have variations in sulfur content, nitrogen content, and metals content. Obviously, the richer tar sand deposits occur toward the base of the formation, but the bitumen is generally of poorer quality. 

Bitumen can be separated into a variety of fractions using a variety of techniques that have been used since the beginning of petroleum science. In general, the fractions produced by these different techniques are called saturates, aromatics, resins, and asphaltenes. Much of the focus has been on the asphaltene fraction because of its high sulfur content and high cokeforming propensity. 

Another source of vanadium, of interest in biological and environmental contexts, are fossil fuels such as peat, coal, bitumen, oil-shales, asphalts and crude oil. The vanadium content of hard coal can vary from 0.007 to 0.34%. Crude oil from Albania (0.034%), the Volga-Ural region (0.061%) and Venezuela (0.12%) (upper limit in all three cases) is particularly rich in vanadium.I l A high vanadium content is often associated with high sulfur contents. The reasons for the notable enrichment of vanadium in fossils compared with bio-mass precursors such as bacteria, protozoans, algae, plants and animals are still under debate. Possible mechanisms for a secondary input of vanadium in decaying... 

The sulfur content of petroleum is an important property and varies widely within the rough limits 0.1% w/w to 3.0% w/w, and a sulfur content up to 8.0% w/w has been noted for tar sand bitumen. Compounds containing this element are among the most undesirable constituents of petroleum because they can give rise to plant corrosion and atmospheric pollution. Petroleum can evolve hydrogen sulfide during distillation as well as low-boUing sulfur compounds. 

A test method (ASTM D-1552) is available for sulfur analysis the method covers three procedures applicable to samples boiling above 177°C (350°F) and containing not less than 0.06 mass % sulfur. Thus the method is applicable to most fuel oils, lubricating oils, residua, and coke, and coke containing up to 8% by weight sulfur can be analyzed. This is particularly important for cokes that originate from heavy oil and tar sand bitumen, where the sulfur content of the coke is usually at least 5% by weight. 

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