High-sulfur bitumens

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. 

Table 8-4). The process can be used to convert a wide range of feedstocks with high sulfur and heavy metals, including heavy oils, oil sand bitumen, residua, and visbroken residua. As a note of interest, the HSC process both employs continuous reactors where as the original Eureka process uses two batch reactors. 

This process is suitable for the desulfurization of high-sulfur residua (atmospheric and vacuum) to produce low-sulfur fuel oils or catalytic cracking feedstocks. In addition, the process can be used, through alternate design types, to upgrade high-sulfur crude oils or bitumen that are not suitable for the more conventional refining techniques. 

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). 

Sulfur, carbon and hydrogen stable isotope ratios of pyrite, kerogens, and bitumens of two high-sulfur Monterey formation samples from the onshore Santa Maria Basin in California were determined. Kerogens from these were pyrolyzed at 300°C for periods of 2, 10 and 100 hours in closed systems and the yields and isotopic compositions of S-containing fractions (residual kerogens, bitumens and hydrogen sulfide) were determined. 

A very severe problem has arisen in South Russia and Kazakhstan as a result of stockpiling millions of tons of elemental sulfur over the past few decades. This sulfur has been extracted from high sulfuric oil and natural gas but has not been used because it is chemically unstable when it comes into contact with atmospheric gases and moisture and thus can become a serious ecological threat. The last problem might be resolved by transform ing the orthorhombic sulfur modification (equilibrium under ambient conditions) into its polymeric modification the latter is chemically more inert and can be used as a valuable component of large scale composite materials such as sulfur concrete, sulfur bitumen, and so on. 

Compared with a high-sulfur, metal-rich crude oil from the Boscan field of Venezuela (3), the vanadium contents of most of the tar sand bitumens see Table I) are relatively low, particularly in view of the high sulfur values of some of the bitumens. If tar sand bitumens are the residues of crude oils which have lost their light ends, it might be expected that metals, which are always concentrated in the heavier... 

Asphaltene A polyaromatic component of some crude oils that has a high molecular mass and also high sulfur, nitrogen, oxygen, and metal contents. In practical work asphaltenes are usually defined operationally by using a standardized separation scheme. One such scheme defines asphaltenes as those components of a crude oil or bitumen that are soluble in toluene but insoluble in n-pentane. 

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 high sulfur cost in comparison to bitumen during that period, the blending and storage problems encountered and the health/safety concerns had affected the use of sulfur in asphalt works. The development of solid flour pellets, added directly to the asphalt mixing process, and changes in sulfur/bitumen cost eliminated the abovementioned problems. 

The LC-Fining process has been applied to desulfurization of bitumen extracted from the Athabasca tar sands (Bishop, 1990). In one reported instance, a low-solids bitumen and a high-solids bitumen were employed as feedstocks whereupon good conversion of the bitumen to lower-sulfur products was noted... 

Most of the sulfur present in crude oils and bitumens is organically bound, (i.e., bound to carbon) because dissolved hydrogen sulfide and elemental sulfur usually represent only a minor part of the total sulfur. Organic sulfur is present in low- to medium-molecular-weight molecules, but the largest fraction is in the high-molecular-weight components (25-26. 28-291... 

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). 

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