Alkyl dibenzothiophenes

Folsom, B. R. Schieche, D. R. DiGrazia, P. M., et al., Microbial Desulfurization of Alkylated Dibenzothiophenes From a Hydrodesulfurized Middle Distillate by Rhodococcus Erythropo-lis 1-19. Applied and Environmental Microbiology, 1999. 65(11) pp. 4967-4972. 

Kobayashi, M. Horiuchi, K. Yoshikawa, O., et al., Kinetic analysis of microbial desulfurization of model and light gas oils containing multiple alkyl dibenzothiophenes. Bioscience Biotechnology and Biochemistry, 2001. 65(2) pp. 298-304. 

Matsui, T., and Maruhashi, K., Isolation of Carotenoid-Deficient Mutant From Alkylated Dibenzothiophene Desulfurizing Nocardioform Bacteria, Gordonia Sp TM414. Current Microbiology, 2004. 48(2) pp. 130-134. 

Boehm and Farrington [18] successfully applied this technique to marine sediments. However, lacking the analytical capabilities to resolve all of these alkylated species, other techniques must be employed. It has been determined that the most environmentally stable alkylated dibenzothiophenes... 

Hydrodesulfurization (HDS) is an important process in petrochemical refinery as it allows deaeasing the sulfur content in diesel fuel. Compounds such as alkylated dibenzothiophene (DBT) raise some problems in HDS. The alkyl groups, especially when located in the 4 and 6 positions of the ring (see Figure 18) make alkylated DBT resistant to classical HDS catalysts because of the methyl groups that prevent the thiophenic sulfur atom to be in contact with the active site of the catalyst. 

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorobiphenyls (PCBs), and polychlorophenols (PCPs) are well-known artifacts ubiquitous in the present environment. Due to their lipophilic-ity and resistance to metabolism or chemical degradation these have the potential to accumulate in the food chain and cause toxic effects [1, 2]. Polycyclic aromatic sulfur heterocycles (PASHs) along with different kinds of polycyclic aromatic compounds (PACs) also occur widely in the environment [3,4]. In particular, alkylated dibenzothiophenes have previously been found to be persistent residues in the marine environment after oil spills. Dibenzothiophene and its alkylated derivatives have been found to accumulate in fish and other marine organisms [5-7]. 

Dibenzothiophenes show increasing bioconcentration factors and octa-nol/water partition coefficients with increasing alkyl substitution [38]. It is not known how persistent PCDTs and PCTAs are in the environment. However, alkylated dibenzothiophenes have previously been found to be persistent oil residue compounds in marine organisms and especially in sediments. DBT derivatives, which are abundant in crude oil, represent a group of most persistent oil residues in the marine environment. Alkyl substituents retard microbial degradation. However, some microbes are known which degrade DBT derivatives [7, 39-41]. Oxidation of the derivatives of dibenzothiophene to the respective sulfoxides and sulfones is possible [42]. 

Pine needles from the surroundings of metal reclamation plant probably contained PCDTs in low concentrations. Quantitative determinations were not made due to much interference by other compounds of similar type [49]. The concentrations of TeCDDs were in the range of 5-50 pg/g per dry weight of needles and the concentrations of TeCDFs in the range of 4-15 pg/g. Quite high concentrations of alkylated dibenzothiophenes in pine needles in a recipient area of the emissions from a pulp and paper mill have been measured, which might suggest that PCDTs could also be taken up by needles [56]. 

Chakhmakhchev S, Suzuki M, Takayama K (1997) Distribution of alkylated dibenzothiophenes in petroleum as a tool for maturity assessments. Org Geochem 26, 483-490. 

Among these blendstocks, the alkyl dibenzothiophenes with alkyl groups at the four- or/and six-positions are typical representatives of the refractory sulfur compounds, which are difficult to remove using the conventional HDS process. Thus, to satisfy the environmental regulations, deep desulfurization and ultra-deep... 

TMBT, 2,3-DMBT, and the minor species 2,3,5-TMBT and 2,3,6-TMBT. The more detailed analyses of a diesel fuel by Ma et al. (1994) showed 61 sulfur compounds. These were, again, almost exclusively alkyl benzothiophenes and alkyl dibenzothiophenes. An example for the sulfur composition of gasoline is given in Table 10.13. 

In addition, gasoline contains benzothiophenes and alkylated benzothiophenes, while dibenzothiophene and alkylated dibenzothiophenes can be detected in jet fuels and diesel. Polycyclic sulfur compounds with three or more rings are found in heavy fuel oils [109]. A typical sulfur compound of diesel fuel is 4,6-dimethyldibenzothio-phene [109]. 

Oxidative addition of thiophene and other sulfur-containing heterocycles to low-valent metal centers is a key step in the catalytic HDS process, carried out by the petrochemical industry on a multimillion ton scale to remove sulfur compounds from petroleum oil derivatives. These heterocycles react with [NiH(dippe)]2 (a source of the Ni dippe fragment) under mild reaction conditions to give thianickelacycle complexes (Scheme 59 and Equation (85)). Alkylated dibenzothiophenes are among the least reactive components of the crude oil distillate ... 

Figure 15.7. Alkyl-dibenzothiophene oxidation to the corresponding sulfone.

In general, there are two possible reaction pathways for removal of sulfur from dibenzothiophene (DBT) and alkylated dibenzothiophenes as shown in Figure The first pathway is by direct extraction of the sulfur atom from the molecule. The second pathway is by prehydrogenation of one aromatic ring followed by extraction of the sulfur atom. 

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