Aromatic Organosulfur Compounds Research Articles

Bacterial Biological Factories Intended for the Desulfurization of Petroleum Products in Refineries

The removal of sulfur by deep hydrodesulfurization is expensive and environmentally unfriendly. Additionally, sulfur is not separated completely from heterocyclic poly-aromatic compounds. In nature, several microorganisms (Rhodococcus erythropolis IGTS8, Gordonia sp., Bacillus sp., Mycobacterium sp., Paenibacillus sp. A11-2 etc.) have been reported to remove sulfur from petroleum fractions. All these microbes remove sulfur from recalcitrant organosulfur compounds via the 4S pathway, showing potential for some organosulfur compounds only. Activity up to 100 µM/g dry cell weights is needed to meet the current demand for desulfurization. The present review describes the desulfurization capability of various microorganisms acting on several kinds of sulfur sources. Genetic engineering approaches on Gordonia sp. and other species have revealed a variety of good substrate ranges of desulfurization, both for aliphatic and aromatic organosulfur compounds. Whole genome sequence analysis and 4S pathway inhibition by a pTeR group inhibitor have also been discussed. Now, emphasis is being placed on how to commercialize the microbes for industrial-level applications by incorporating biodesulfurization into hydrodesulfurization systems. Thus, this review summarizes the potentialities of microbes for desulfurization of petroleum. The information included in this review could be useful for researchers as well as the economical commercialization of bacteria in petroleum industries.

Biodesulfurization of the mixture of dibenzothiophene and its alkylated derivatives by Sphingomonas subarctica T7b

Organosulfur compounds classified as dibenzothiophenes (DBTs) and their derivatives are contained in petroleum. When used as fuel, these substances release SOx emissions, thus contributing to air pollution, acid rain, and climate change. Therefore, it is necessary to reduce the content of these organic sulfur compounds in fuels and one way to achieve this is through bacterial desulfurization. This study reports the biodesulfurization process of a mixture of DBT, 4-hexyl DBT, 4,6-dibutyl DBT, and various organosulfur compounds in light gas oil (LGO). The experiment was conducted by treating 1 mL of aromatic organosulfur compounds with 100 mg/L in \textit{n}-tetradecane or 1 mL LGO with 5 mL mineral salts in sulfur-free medium, incubated at 27 °C for 5 days with shaking at 273 rpm. Gas chromatography analyses revealed that the growing Sphingomonas subarctica T7b cells desulfurized and converted 88.29% of DBT to 2-hydroxybiphenyl as a metabolite while a mixture of DBT and 4,6-dibutyl DBT was desulfurized at 86.40\% and 7.00%, respectively. Furthermore, the mixture of DBT, 4-hexyl DBT, and 4,6-dibutyl DBT had a desulfurization percentage of 84.40%, 41.00%, and 6.66%, respectively, after five days of incubation. The compounds were observed to desulfurize slightly better as single compounds compared to when mixed with other aromatic sulfur compounds.

Science and Technology Progress on the Desulfurization Process of Crude Oil

Currently, crude oil still remains an irreplaceable energy source for chemical industrial processes, transportation systems, electricity, and other human activities. However, crude oil contains sulfur elements as the major impurities in the form of aliphatic and aromatic organosulfur compounds. During the combustion of fuel, these organosulfur compounds are converted to harmful SOx gases; thus, many countries strictly limit the maximum sulfur content in the fuels. To fulfill the government regulation, refineries are trying to decrease the maximum sulfur content in crude oil through several desulfurization technologies, such as hydrodesulfurization, adsorption, oxidative‐desulfurization, alkylation, and biodesulfurization. Each desulfurization technology has its own advantages and disadvantages. In this review article, we aimed to briefly summarize the progress in the developing science and technology of each desulfurization process of crude oil. Several fields in the desulfurization process are still facing challenges to create better designs and development for a safer future of the world.

High‐performance adsorptive desulfurization by ternary hybrid boron carbon nitride aerogel

AbstractSeparation of aromatic organosulfur compounds is vital for upgrading the feed to clean fuel products, however, it remains a formidable challenge for the present adsorbents. Herein, a series of novel aerogel‐like boron carbon nitride (BCN) with three‐dimensional interconnected porous networks were fabricated via a hydrogel template and freeze‐casting strategy. The as‐prepared aerogel‐like BCN had a variable carbon content and a flexible size of graphene domain on its porous structure. The optimal BCN aerogel represents the top‐level of adsorptive desulfurization (ADS) capacity for aromatic organosulfur compounds (30.8 mg S/g adsorbent), strikingly higher than the state‐of‐the‐art aerogels adsorbents (17.1 mg S/g adsorbent) reported under similar conditions. A selective adsorption for dibenzothiophene in the presence of aromatic hydrocarbons, nitrogen compounds were also achieved on BCN aerogel. The adsorption isotherm and XPS measurement reveal heterogeneous adsorption on the BCN aerogel via π–π and Lewis acid–base interactions.

Homology Modeling and In Silico Docking Studies of DszC Enzyme of Streptomyces sp. VUR PPR 101

Sulfur dioxide released during the combustion of fossil fuels causes hazardous effects to living beings. The traditional hydrodesulfurization (HDS) which is employed to remove sulfur components from fossil fuels is not effective in the reduction in aromatic organosulfur compounds like benzothiophene (BT), dibenzothiophene (DBT) and its derivatives. Biodesulfurization process by microorganisms is considered as an effective one over HDS in the removal of sulfur from fuels. DBT, which is a typical recalcitrant organosulfur compound, is considered as a model compound for biodesulfurization studies. Microbes which employ 4S pathway for the removal of sulfur from DBT are commercially so significant. The 4S pathway encompasses four reactions involving three enzymes. The present work deals with the DszC enzyme which catalyzes the first two reaction steps of 4S pathway. The 3D structure of DszC enzyme protein of Streptomyces sp. VUR PPR 101 was modeled and validated. Four mutant DszC enzyme proteins viz., Q119I, H221L, F161A and N129A, were constructed. Wild and mutant DszC proteins were docked against the substrates, DBT and dibenzothiophene sulfoxide (DBTO). Based on the Libdock scores of the docked complexes, the mutant proteins F161A and H221L were found with the highest affinity toward DBT and DBTO, respectively.

The synthetic strategies of hierarchical TS-1 zeolites for the oxidative desulfurization reactions

With the increasingly stringent standards for limiting sulfide content in liquid fuels, oxidative desulfurization (ODS) has become a promising ultra-deep desulfurization process in fuel desulfurization. TS-1 zeolites show great potential as catalysts for ODS reactions, due to its remarkable oxidation activity at low temperatures and pressure. However, the inherent microporous structure of conventional TS-1 zeolites restricts the mass transportation and renders the active sites in the microporous space of TS-1 zeolites inaccessible for bulky aromatic organosulfur compounds. Fabrication of hierarchical TS-1 zeolites by incorporating meso-/macropores into microporous TS-1 zeolites is an effective strategy to improve mass transportability. In recent years, abundant efforts have been dedicated to developing synthetic strategies of hierarchical TS-1 zeolite, thereby improving its catalytic performance in the ODS process. This mini-review addresses the synthetic methods of hierarchical TS-1 catalysts and their catalytic performance in the ODS reactions. In addition, some current problems and prospects of synthesis routes for constructing hierarchical TS-1 catalysts have also been revised. We expect this mini-review to shed light on the more efficient preparation strategies of hierarchical TS-1 zeolites for the ODS process. Construction of hierarchical TS-1 zeolites for the oxidative desulfurization reactions.

Headspace Characterization and Quantification of Aromatic Organosulfur Compounds in Garlic Extracts Using Surface-Enhanced Raman Scattering with a Mirror-in-a-Cap Substrate.

Surface-enhanced Raman scattering (SERS) has been deployed in the analysis of food at solid and aqueous states. However, its capability has not been fully explored in headspace profiling. To develop an innovative SERS method for analyzing headspace volatile compounds in foods. A volatile-capture device was developed by depositing a film of silver nanoparticles in a vial cap to capture the volatiles released from a model flavor compound (garlic). SERS peaks at 1632, 1400, 1291, 1191, 731, and 577 cm-1 were identified in the headspace of the garlic sample, which was representative of an organosulfur compound (diallyl disulfide), and its concentration was determined at 135 ppm, which was comparable to the value determined using GC. Preparation and analysis could be carried out in <10 min for the SERS method. The sensitivity of the SERS method (10 ppm), however, was slightly less than that of the GC method (5 pm). The SERS method was able to quantify the concentration of diallyl disulfide in the headspace of a raw garlic ethanolic extract. Compared to GC, the SERS method had a much shorter analysis time and simpler sample preparation procedure than GC when analyzing large numbers of samples. The innovative "mirror-in-a-cap" substrate was simpler and faster than other reported SERS substrates used for this purpose. Additionally, SERS has much better portability and the potential for real-time monitoring of changes in the garlic headspace concentration during manufacturing and processing.

Catalytic inter- and intramolecular coupling of aryl sulfones

Catalytic transformations of aromatic organosulfur compounds involving C–S bond cleavage have garnered increasing attention in the cross-coupling arena. However, little attention has been paid to coupling reactions of aryl sulfones at this moment. In this paper, catalytic inter- and intramolecular coupling reactions of aryl sulfones are summarized to expand the utility of aryl sulfones in organic synthesis.

Quantum Chemical Evaluation of Deep Eutectic Solvents for the Extractive Desulfurization of Fuel

Sulfur compounds in fuels are converted to SOx during combustion, poisoning automotive catalytic converters and creating serious environmental concerns (e.g., acid rain). The efficient desulfurization of liquid fuel is thus a critical step toward minimizing SOx emissions and their associated environmental impact. To address this problem, governments worldwide have passed stringent legislation regulating the maximal sulfur levels allowable in fuels. In the petroleum refining industry, the conventional method for removing sulfur from fuel is catalytic hydrodesulfurization which, while highly efficient for removing mercaptans, thioethers, and disulfides, shows limited performance in removing aromatic organosulfur compounds exemplified by dibenzothiophene. To meet these strict environmental targets, innovative strategies beyond hydrodesulfurization for the deep desulfurization of fuel are sought. One key strategy entails the oxidation of refractory organosulfur compounds in liquid fuel, coupled with efficient...

Utilisation of aromatic organosulfur compounds as sulfur sources by Lipomyces starkeyi CBS 1807.

Aromatic organosulfur compounds that contain aryl carbon-sulfur bonds are rare in nature but occur frequently in industrial processes and products. The utilisation of aryl sulfur compounds as a sulfur source has not been described previously among the budding yeasts (phylum Ascomycota, sub-phylum Saccharomycotina). A total of 31 strains representing 30 species and 28 genera of the budding yeasts were assayed for utilisation of benzene sulfonate as source of sulfur. Lipomyces starkeyi CBS 1807 was the only strain in this screen that was able to utilise benzene sulfonate as a sulfur source. Further study of L. starkeyi demonstrated that it could also utilise methyl phenyl sulfoxide, 1-naphthalene sulfonate, 2-naphthalene sulfonate, 1-anthraquinone sulfonate and 2-anthraquinone sulfonate as sulfur sources but not diphenylsulfone. This study represents the first reported case of the utilisation of sulfonated naphthalenes and anthraquinones as sulfur sources by a fungus. However, it should be stressed that the remaining 30 strains in this study were not assayed for the utilisation of these additional aryl sulfur compounds as sulfur sources. The present study highlights the potential of L. starkeyi and related species as a source of novel enzyme activities with possible applications in chemical manufacturing, disposal of xenobiotics and bioremediation.

Characterization of aromatic organosulfur model compounds relevant to fossil fuels by using atmospheric pressure chemical ionization with CS2 and high-resolution tandem mass spectrometry.

The chemistry of desulfurization involved in processing crude oil is greatly dependent on the forms of sulfur in the oil. Sulfur exists in different chemical bonding environments in fossil fuels, including those in thiophenes and benzothiophenes, thiols, sulfides, and disulfides. In this study, the fragmentation behavior of the molecular ions of 17 aromatic organosulfur compounds with various functionalities was systematically investigated by using high-resolution tandem mass spectrometry. Multiple-stage tandem mass spectrometric experiments were carried out using a linear quadrupole ion trap (LQIT) equipped with an atmospheric pressure chemical ionization (APCI) source. (+)APCI/CS2 was used to generate stable dominant molecular ions for all the compounds studied except for three sulfides that also showed abundant fragment ions. The LQIT coupled with an orbitrap mass spectrometer was used for elemental composition analysis, which facilitated the identification of the neutral molecules lost during fragmentation. The characteristic fragment ions generated in MS(2) and MS(3) experiments provide clues for the chemical bonding environment of sulfur atoms in the examined compounds. Upon collision-induced dissociation (CID), the molecular ions can lose the sulfur atom in a variety of ways, including as S (32 Da), HS(•) (33 Da), H2 S (34 Da), CS (44 Da), (•) CHS (45 Da) and CH2 S (46 Da). These neutral fragments are not only indicative of the presence of sulfur, but also of the type of sulfur present in the compound. Generally, losses of HS(•) and H2 S were found to be associated with compounds containing saturated sulfur functionalities, while losses of S, CS and (•) CHS were more common for heteroaromatic sulfur compounds. High-resolution tandem mass spectrometry with APCI/CS2 ionization is a viable approach to determining the types of organosulfur compounds. It can potentially be applied to analysis of complex mixtures, which is beneficial to improving the desulfurization process of fossil fuels. Copyright © 2016 John Wiley & Sons, Ltd.

Density Functional Theory Study of the Adsorption and Desulfurization of Thiophene and Its Hydrogenated Derivatives on Pt(111): Implication for the Mechanism of Hydrodesulfurization over Noble Metal Catalysts

Desulfurization of thiophene and its hydrogenated derivatives on Pt(111) are studied using self-consistent periodic density functional theory (DFT), and the hydrodesulfurization network is mapped out. On Pt(111), thiophene has two types of adsorption configurations (parallel cross-bridge and partially tilted bridge-hollow), and for its hydrogenated derivates, the molecule is gradually lifted up from the surface with the addition of hydrogen atoms. In all the adsorbed thiophenic compounds, the S atom is always sp3 hybridized; the C atom in the methylene group is always sp3 hybridized, whereas it is either sp2 or sp3 hybridized in the methyne group, depending on how the group interacts with the surface Pt atoms. On the basis of the thermodynamic and kinetic analysis of the elementary steps, a direct desulfurization pathway is proposed for the hydrodesulfurization of thiophene on Pt(111). In contrast to the common thought that hydrogenation toward aromatic organosulfur compounds would make desulfurization easier, the present work clearly demonstrates that hydrogenations of thiophene on Pt(111) do not reduce the energy barrier for the C–S bond cleavage.

Quantitative structure–chromatographic retention relationship for polycyclic aromatic sulfur heterocycles

Polycyclic aromatic sulfur heterocycles (PASHs) are of concern in petroleum geochemistry and environmental chemistry. In the present study, geometrical optimization and electrostatic potential calculations have been performed for 114 PASHs reported previously at the HF/6-31G* level of theory. A group of 25 statistically based parameters have been extracted. Linear relationships between gas-chromatographic retention index (RI) and the structural descriptors have been established by stepwise linear regression analysis. The result shows that two quantities derived from positive electrostatic potential on molecular surface, V s + ¯ (the average value of the positive electrostatic potentials on molecular surface) and σ + 2 (a measure of dispersion tendency of positive electrostatic potential), together with V mc (the molecular volume) and E HOMO (the energy of the highest occupied molecular orbital) can be well used to express the quantitative structure–retention relationship (QSRR) of PASHs. Predictive capability of the model has been demonstrated by leave-one-out cross-validation with the cross-validated correlation coefficient ( R CV) of 0.992. Furthermore, when splitting the 114 PASH samples into calibration and test sets in the ratio of 2:1, a similar treatment yields an equation of almost equal statistical quality and very similar regression coefficients, validating the robustness of our model. Predictions for six PASHs from other source have also been made. The QSRR model established may provide a new powerful method for predicting chromatographic properties of aromatic organosulfur compounds.

Adsorptive removal of aromatic organosulfur compounds over the modified Na-Y zeolites

The adsorptive removal of organosulfur compounds including dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) on the various ion-exchanged Na-Y zeolites (with single Cu2+, Zn2+, Ag+ and the combined Cu2+–Zn2+, Zn2+–Nd3+, Ni2+–Nd3+) in the model systems (the n-octane solutions of sulfur compounds and in some cases with small fraction of benzene/toluene) has been systematically compared. The pre-oxidation of the sulfur compounds together with adsorption procedure over Ag-Y and CuZn-Y adsorbents and the solo-oxidation of the sulfur compounds without adsorption were also performed for comparison. It was observed that the desulfurization efficiency follows the order of direct adsorption>oxidation-adsorption>direct-oxidation. The CuZu-Y was found to be a promising competitor to Ag-Y in terms of the desulfurization performance, and the former is more stable than the latter. The influence of various parameters on desulfurization of Ag-Y and CuZn-Y was investigated. The characterization results of the fresh and used samples provide insights into the characteristics of various adsorbents and the sort of interactions between the adsorbed sulfur compounds and the exchanged metal ions. A full regeneration of used Ag-Y can be achieved by air-calcination at 450°C.

Chemical studies on tobacco smoke. II. Comparison of the yields of several selected components in the smoke from five major Turkish tobacco varieties

With the increasingly stringent standards for limiting sulfide content in liquid fuels, oxidative desulfurization (ODS) has become a promising ultra-deep desulfurization process in fuel desulfurization. TS-1 zeolites show great potential as catalysts for ODS reactions, due to its remarkable oxidation activity at low temperatures and pressure. However, the inherent microporous structure of conventional TS-1 zeolites restricts the mass transportation and renders the active sites in the microporous space of TS-1 zeolites inaccessible for bulky aromatic organosulfur compounds. Fabrication of hierarchical TS-1 zeolites by incorporating meso-/macropores into microporous TS-1 zeolites is an effective strategy to improve mass transportability. In recent years, abundant efforts have been dedicated to developing synthetic strategies of hierarchical TS-1 zeolite, thereby improving its catalytic performance in the ODS process. This mini-review addresses the synthetic methods of hierarchical TS-1 catalysts and their catalytic performance in the ODS reactions. In addition, some current problems and prospects of synthesis routes for constructing hierarchical TS-1 catalysts have also been revised. We expect this mini-review to shed light on the more efficient preparation strategies of hierarchical TS-1 zeolites for the ODS process.