Sulfur compounds in petroleum

Sulfur constitutes about 0.052 wt % of the earth s cmst. The forms in which it is ordinarily found include elemental or native sulfur in unconsohdated volcanic rocks, in anhydrite over salt-dome stmctures, and in bedded anhydrite or gypsum evaporate basin formations combined sulfur in metal sulfide ores and mineral sulfates hydrogen sulfide in natural gas organic sulfur compounds in petroleum and tar sands and a combination of both pyritic and organic sulfur compounds in coal (qv). 

The presence (and concentration, if known) of corrosive materials, other than the typical concentrations of sulfur compounds in petroleum hydrocarbon streams. 

Engineered biocatalysts with altered specificity have been developed. A Rhodococcus strain capable of DBT as well as BT desulfurization has been developed by cloning dsz genes into a strain-containing BT desulfurization pathway. The variety of sulfur compounds in petroleum feedstocks and complexity of the problem may require use of a consortium rather than a single bacterial strain. Alternately, use of multiple bioreactors each with a single dominant strain may be employed to achieve maximum desulfurization [299],... 

Seemingly, T. thiooxidans is able to attack the sulfur-sulfur bond quite readily and the sulfur-carbon bond with some difficulty, if at all. Since a large portion of the sulfur compounds in petroleum are of the monosulfide-aromatic type, more attention is paid to this facet. 

The relative importance attached to sulfur compounds in petroleum may, at first, seem unwarranted, but the presence of sulfur compounds in any crude oil can only result in harmful effects. For example, the presence of sulfur compounds in finished petroleum products such as gasoline will cause corrosion of engine parts, especially under winter conditions when water containing sulfur dioxide (from the internal combustion) may collect in the crankcase. On the other hand, mercaptans cause the corrosion of copper and brass in the presence of air and also have an adverse effect on the color stability of gasoline and other liquid fuels. 

Table 3-3 Types of Organic Sulfur Compounds in Petroleum... 

A number of reviews related to the identification of sulfur compounds in petroleum should be mentioned. Dean and Whitehead (30) summarized work on separation and identification of sulfur compounds in petroleum and shale oil in 1967. Drushel (7) reviewed sulfur compound types with an emphasis on the available analytical methods as of 1970. Mehmet (31) and Gal pern (32) also reviewed sulfur compounds in petroleum in 1971 with some speculation on their origin. The major contributions of API Project 48 reported by Coleman et al. in 1971, Rail et al. in 1972, and Thompson in 1981 will be discussed below (33-35) More recent summaries of sulfur compounds by Aksenov and Kamyanov in 1981 (36) and by Gal pern in 1985 (37), discuss OSC in petroleum, processed petroleum fractions, shale oil, coal derived liquids and related products. These reviews include much of the Soviet literature. In 1975 and 1978 Orr (28-291 discussed sulfur in the petroleum system with somewhat... 

Figure 1. Examples of non-thiophenic sulfur compounds in petroleum and related materials.

As is evident from the focus of this symposium, there is a great interest in sulfur compounds in petroleum. In addition, there is no doubt that microbial metabolism has played a major role in the quantity and quality of the World s petroleum. Yet there is relatively little information on the microbial metabolism of OSC found in petroleum. This paper provided a thorough review of the literature on the topic but it discussed only 20 pure OSC. I am not aware of work which has been done with any other compounds. In their studies of several crude oils, Rail et al. (13) isolated and identified 176 organic sulfur compounds which were grouped into 13 classes. Many more sulfur compounds have been identified since their work. Thus there is much more to be learned about microbial transformations of these compounds. 

Sulfur oxides (S02 and S03) present in flue gases from upstream combustion operations adsorb onto the catalyst surface and in many cases form inactive metal sulfates. It is the presence of sulfur compounds in petroleum-based fuels that prevent the super-sensitive base metal catalysts (i.e., Cu, Ni, Co, etc.) from being used as the primary catalytic components for many environmental applications. Precious metals are inhibited by sulfur and lose some activity but usually reach a lower but steady state activity. Furthermore the precious metals are reversibly poisoned by sulfur compounds and can be regenerated simply by removing the poison from the gas stream. Heavy metals such as Pb, Hg, As, etc. alloy with precious metals and permanently deactivate them. Basic compounds such as NH3 can deactivate an acidic catalyst such as a zeolite by adsorbing and neutralizing the acid sites. 

Table 4 Some typical sulfur compounds in petroleum...

Ohshiro, T. Izumi, Y. Microbial desulfurization of organic sulfur compounds in petroleum. Biosci. Biotechnol. Biochem. 1999, 62 (1), 1-9. 

API and Bureau of Mines Projects. Some of the most important current work on the sulfur compounds present in petroleum is being carried out under the auspices of the American Petroleum Institute under Project 48 which was organized in 1948 to conduct fundamental studies on the synthesis, properties, and identification of sulfur compounds in petroleum. At present. Project 48 consists essentially of four phases (1) production and purification of sulfur compounds and the determination of their common physical properties (2) measurement of thermodynamic properties of pure sulfur compounds (3) identification and measurement of sulfur compounds in crude oil and (4) development of methods of synthesis and identification of sulfur compounds. Work on the first three phases, combined as Project 48A, is being conducted at the U. S. Bureau of Mines under the supervision of H. M. Smith as project director. Work on the fourth... 

Decomposition of Sulfur Compounds in Petroleum During Distillation. 

Hall, M. E., Polarographic Studies of Sulfur Compounds in Petroleum, paper presented... 

Properties, and Identification of Sulfur Compounds in Petroleum. A Report on API Research Project 48, Preprint of paper presented at the 32nd Annual Meeting of API, Chicago, Ill., Nov. 10, 1952. 

The copper strip test methods are used to determine the corrosiveness to copper of gasoline, diesel fuel, lubricating oil, or other hydrocarbons. Most sulfur compounds in petroleum are removed during refining. However, some residual sulfur compounds can have a corroding action on various metals. This effect is dependent on the types of sulfur compounds present. The copper strip corrosion test measures the relative degree of corrosivity of a petroleum product. 

The copper strip test methods are used to determine the corrosiveness to copper of diesel fuel and are a measure of the relative degree of corrosivity of diesel fuel. Most sulfur compounds in petroleum are removed during refining. However, some residual sulfur compounds can have a corroding action on various metals, and the effect is dependent on the types of sulfur compounds present. One method (ASTM D-130, IP 154) uses a polished copper strip immersed in a given quantity of sample and heated at a temperature for a time period characteristic of the material being tested. At the end of this period the copper strip is removed, washed, and compared with the copper strip corrosion standards (ASTM, 2000). This is a pass/fail test. In another method (ASTM D-849) a polished copper strip is immersed in 200 ml of specimen in a flask with a condenser and placed in boiling water for 30 min. At the end of this period, the copper strip is removed and compared with the ASTM copper strip corrosion standards. This is also a pass/fail test. 

Hydrodesulfurization [HDS, Eq. (1)] is the process by which sulfur is removed from fossil materials upon treatment with a high pressure of H2 (3.5-17 MPa) at high temperature (300-425 °C) in the presence of heterogenexius catalysts, generally transition metal sulfides (Mo, W, Co, Ni) supported on alumina [1]. About 90% of the sulfur in fossil materials is contained in thiophenic molecules, which comprise an enormous variety of substituted thiophenes, and benzo[b]thiophenes, di-benzo[b,d]thiophenes as well as other fused-ring thiophenes, most of which are generally less easily desulfurized over heterogeneous catalysts than any other sulfur compound in petroleum feedstocks (e.g., thiols, sulfide, and disulfides). 

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