4-6-dimethyldibenzothiophene and dibenzothiophene

Ultradeep desulfurization of fuels is a method of enormous demand due to the generation of harmful compounds during the burning of sulfur-containing fuels, which are a major source of environmental pollution. Among the various desulfurization methods in application, adsorptive desulfurization (ADS) has low energy demand and is feasible to be employed at ambient conditions without the addition of chemicals. The most crucial factor for ADS application is the selection of the adsorbent, and, currently, a new family of porous materials, metal organic frameworks (MOFs), has proved to be very effective towards this direction. In the current review, applications of MOFs and their functionalized composites for ADS are presented and discussed, as well as the main desulfurization mechanisms reported for the removal of thiophenic compounds by various frameworks. Prospective methods regarding the further improvement of MOF's desulfurization capability are also suggested.

Topics: Adsorption; Fossil Fuels; Metal-Organic Frameworks; Models, Molecular; Molecular Structure; Structure-Activity Relationship; Sulfur Compounds; Thiophenes

To remove dibenzothiophene (DBT) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) adsorbed on alumina, silica and sepiolite through biodesulfurization (BDS) using Rhodococcus Rhodochrous spp., that selectively reduce sulfur molecules without generating of gaseous pollutants.. The adsorption of DBT and 4,6-DMDBT was affected by the properties of the supports, including particle size and the presence of surface acidic groups. The highest adsorption of both sulfur-containing organic molecules used particle sizes of 0.43-0.063 mm. The highest percentage removal was with sepiolite (80 % for DBT and 56 % for 4,6-DMDBT) and silica (71 % for DBT and 37 % for 4,6-DMDBT). This is attributed to the close interaction between these supports and the bacteria.. Biodesulfurization is effective for removing the sulfur-containing organic molecules adsorbed on inorganic materials and avoids the generation of gaseous pollutants.

Topics: Adsorption; Aluminum Oxide; Biodegradation, Environmental; Magnesium Silicates; Rhodococcus; Silicon Dioxide; Sulfur; Thiophenes

The reaction between [V(IV)OSO(4)] and the tetradentate N(2)O(2)-donor Schiff base ligand, N,N-bis(o-hydroxybenzaldehyde)phenylenediamine (sal-HBPD), obtained by the condensation of salicylaldehyde and o-phenylenediamine in a molar ratio of 2 : 1 respectively, resulted in the formation of [V(IV)O(sal-HBPD)]. The molecular structure of [V(IV)O(sal-HBPD)] was determined by single crystal X-ray diffraction, and confirmed the distorted square pyramidal geometry of the complex with the N(2)O(2) binding mode of the tetradentate ligand. The formation of the polymer-supported p[V(IV)O(sal-AHBPD)] proceeded via the nitrosation of sal-HBPD, followed by the reduction with hydrogen to form an amine group that was then linked to Merrifield beads followed by the reaction with [V(IV)OSO(4)]. XPS and EPR were used to confirm the presence of oxovanadium(IV) within the beads. The BET surface area and porosity of the heterogeneous catalyst p[V(IV)O(sal-AHBPD)] were found to be 6.9 m(2) g(-1) and 180.8 Å respectively. Microanalysis, TG, UV-Vis and FT-IR were used for further characterization of both [V(IV)O(sal-HBPD)] and p[V(IV)O(sal-AHBPD)]. Oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated using [V(IV)O(sal-HBPD)] and p[V(IV)O(sal-AHBPD)] as catalysts. Progress for oxidation of these model compounds was monitored with a gas chromatograph fitted with a flame ionization detector. The oxidation products were characterized using gas chromatography-mass spectrometry, microanalysis and NMR. Dibenzothiophene sulfone (DBTO(2)) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO(2)) were found to be the main products of oxidation. Oxovanadium(IV) Schiff base microspherical beads, p[V(IV)O(sal-AHBPD)], were able to catalyse the oxidation of sulfur in dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to a tune of 88.0% and 71.8% respectively after 3 h at 40 °C. These oxidation results show promise for potential application of this catalyst in the oxidative desulfurization of crude oils.

Topics: Catalysis; Crystallography, X-Ray; Models, Molecular; Molecular Structure; Oxidation-Reduction; Thiophenes; Vanadates

Two synthetic, polymer-derived carbons were modified with urea to incorporate nitrogen surface functional groups. Then they were investigated as adsorbents of dibenzothiophene (DBT) and 4, 6-dimethyldibenzothiophene (DMDBT) from simulated diesel fuel under dynamic conditions with the total concentration of sulfur being 20 ppmw. The materials before and after adsorption were characterized using elemental analysis, XPS, adsorption of nitrogen, potentiometric titration, and thermal analysis. The incorporation of nitrogen species caused a visible increase in the adsorption capacity. However, selectivity evaluated on the basis of the adsorption of naphthalene decreased. Whereas at low surface coverage the volume of pores smaller than 10 A is important, with the progress of adsorption the surface chemistry gradually starts to play a more important role via either polar or acid/base interactions. The latter are important for the selectivity of adsorption when the aromatic hydrocarbons are present. Although polar interactions are weaker than the acid-base ones, the centers that they represent seem to be more favorable to attract DBT and DMDBT than arenes. There is an indication that nitrogen-containing groups contribute to chemical transformations of DBT and DMDBT/oxidation and promote the involvement of oxygen from the surface groups in the reactive adsorption.

Topics: Adsorption; Carbon; Chemical Industry; Gasoline; Naphthalenes; Nitrogen; Polymers; Protons; Sulfonic Acids; Sulfur; Surface Properties; Thiophenes

A new isolated dibenzothiophene (DBT) desulfurizing bacterium, identified as Mycobacterium sp. ZD-19 can utilize a wide range of organic sulfur compounds as a sole sulfur source. Thiophene (TH) or benzothiophene (BTH) was completely degraded by strain ZD-19 within 10h or 42 h, and 100% DBT or 4,6-dimethyldibenzothiophene (4,6-DMDBT) was removed within 50h or 56 h, respectively. Diphenylsulfide (DPS) possessed the lowest desulfurization efficiencies with 60% being transformed within 50h and 80% at 90 h. The desulfurization activities of five substrates by resting cells are in order of TH>BTH>DPS>DBT>4,6-DMDBT. In addition, when DBT and 4,6-DMDBT were mixed, they could be simultaneously desulfurized by strain ZD-19. However, DBT appeared to be attacked prior to 4,6-DMDBT. The desulfurization rate of DBT or 4,6-DMDBT in mixture is lower than they are desulfurized separately, indicating that the substrate competitive inhibition is existent when DBT and 4,6-DMDBT are mixed.

Topics: Biodegradation, Environmental; Mycobacterium; Phylogeny; RNA, Ribosomal, 16S; Sulfur; Sulfur Compounds; Thiophenes; Time Factors

Photooxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT) sensitized by N-methylquinolinium tetrafluoborate (NMQ(+)BF4-) has been investigated in O2-saturated acetonitrile solutions. Nearly 100% oxidation of DBT and DMDBT was observed, and the oxidized products are predominantly composed of sulfoxides and sulfones, which are formed via photoinduced electron transfer (ET). Such ET processes were studied with fluorescence quenching of NMQ+, time-resolved transient absorption measurement, and ESR experiments. The fluorescence of NMQ+ is efficiently quenched by DBT and DMDBT via diffusion-controlled processes, with bimolecular quenching constants of 1.6 x 10(10) M(-1) s(-1) for DBT and 2.3 x 10(10) M(-1) s(-1) for DMDBT. The electron-transfer nature of the quenching is evidenced by the transient absorption measurement of the neutral radical NMQ*, which is formed by electron transfer from the substrates (DBT or DMDBT) to the excited singlet state of NMQ+. The ESR spectra of the superoxide radical anion (O2*-) trapped by 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in the photooxygenation of DBT and DMDBT as well as their sulfoxides manifest that O2 traps an electron from NMQ* to form O2*-. The fact that the formation of sulfoxides and sulfones is greatly suppressed in the presence of benzoquinone (BQ), an efficient electron trap for NMQ* and O2*-, further indicates an ET process in the photooxidation of DBT and DMDBT. As inferred from the control experiments, the role of singlet oxygen (1O2) in the photooxidation is negligible. The intermediates responsible for the formation of sulfoxides and sulfones have been examined in detail.

Topics: Borates; Fluorine; Oxidation-Reduction; Photochemistry; Quinolinium Compounds; Thiophenes

New desulfurizing bacteria able to convert dibenzothiophene into 2-hydroxybiphenyl and sulfate were isolated from contaminated soils collected in Mexican refineries. Random amplified polymorphic DNA analysis showed they were different from previously reported Rhodococcus erythropolis desulfurizing strains. According to 16S rRNA gene sequencing and fatty acid analyses, these new isolates belonged to the genus Rhodococcus. These strains could desulfurize 4,6-dimethyldibenzothiophene which is one of the most difficult dibenzothiophene derivatives to remove by hydrodesulfurization. A deeply hydrodesulfurized diesel oil containing significant amounts of 4,6-dimethyldibenzothiophene was treated with Rhodococcus sp. IMP-S02 cells. Up to 60% of the total sulfur was removed and all the 4,6-dimethyldibenzothiophene disappeared as a result of this treatment.

Topics: Biodegradation, Environmental; Gasoline; Rhodococcus; Soil Microbiology; Sulfur; Thiophenes