Removal Of Sulfur Compounds Research Articles

Separation of thiophene/n-heptane mixtures using PEBAX/PVDF-composited membranes via pervaporation

Composited membranes made of poly (ether-block-amide)/polyvinylidene difluoride (PEBAX 2533/PVDF) were prepared for separation of thiophene/n-heptane mixtures via pervaporation. PEBAX 2533 was selected based on its solubility parameter calculated by the group contribution method. The membranes' sorption properties were studied in swelling experiments. The suitability of the membranes for the separation of mixtures was explored via pervaporation experiments. Swelling experiments showed that the degree of swelling increased with increasing temperature and thiophene concentration. The effects of thiophene feed concentration and operation temperature on pervaporation performance were investigated. Experimental results showed that increases in the thiophene concentration and system temperature both not only led to significant increase in total flux, but also caused decrease in separation factor. This result also showed that PEBAX/PVDF-composited membranes are more selective to thiophene than to n-heptane. When feed thiophene concentration was 1000μg/g and feed temperature was 40°C, total flux and separation factor were 3.8kg/(m2h) and 4.0, respectively. Elemental analysis (CHNS-O) was performed to determine the molar ratio of polyether and polyamide in PEBAX 2533. The results showed that this molar ratio was 10:1. The membranes were characterized by scanning electron microscopy (SEM) to study surface and cross-sectional morphologies. SEM images showed that there is an interface between the PEBAX 2533 separation layer and the PVDF support layer. The surface of the PEBAX 2533 separation layer was dense and had no obvious defects. The activity energy was calculated according to the Arrhenius equation. Pervaporation results were compared with those reported in the literatures. This work may provide useful insights into the viability of the removal of sulfur compounds from gasoline via pervaporation.

Preparation of highly dispersed tungsten species within mesoporous silica by ionic liquid and their enhanced catalytic activity for oxidative desulfurization

A series of W-containing mesoporous silicas with different calcination temperatures were in situ synthesized by using [(n-C8H17)3NCH3]2W2O11 not merely as a novel template but also the W precursors. The catalysts were characterized by N2 adsorption–desorption, XRD, XPS, HRTEM, EDS, ICP, FTIR, and UV–vis DRS analysis. The N2 adsorption–desorption and HRTEM results indicated that these catalysts possessed mesoporous structure with relatively uniform pores and large internal surface areas. The XRD, ICP and HRTEM results indicated that the W species were highly dispersed on the surface and into the mesoporous silicas matrix. The catalysts also showed excellent catalytic performance on the removal of refractory bulky molecule sulfur compounds from the model oil with H2O2. Based on the removal of DBT in the model oil, the optimal calcination temperature of the catalysts is 450°C. The catalytic activity of different sulfur-containing substrates was also investigated. After 8-times recycling, the sulfur removal could still reach 99.2% without any significant decrease.

Chemisorption of hydrogen sulphide and methanethiol by light expanded clay aggregates (Leca)

Removal of volatile sulphur compounds from livestock waste air by biological air filtration may be enhanced by application of packing materials with reactive properties. In this study, light expanded clay aggregates (Leca®) was tested with respect to sorption and potential chemical degradation of H2S, Methanethiol (MT) and Dimethyl sulphide (DMS). Leca was selected due to its content of minerals, including iron, and due to its high specific surface area. The performance of Leca was evaluated based on breakthrough curves and by comparing the difference between the inlet and outlet gas concentrations. Whereas DMS did not appear to be removed by Leca, both H2S and MT were removed with variable efficiency depending on the specific conditions. Dimethyl disulphide (DMDS) and dimethyl trisulphide (DMTS) were demonstrated to be produced during the degradation process in relatively high yields. A comparison between ambient air and nitrogen gas conditions showed that the chemisorption of H2S and MT did not necessarily need oxygen to be present. X-ray analysis of Leca showed an abundance of Fe2O3. It is therefore hypothesized that Fe2O3 in Leca can remove H2S and MT by chemisorption. Both air velocity and moisture content clearly affected the capacity of Leca for removal of H2S and MT. Lower removal is seen at higher air velocities, whereas higher moisture content enhances removal. However, chemisorption of MT by Leca appears to be limited above a threshold moisture level. Potential reaction mechanisms are discussed in relation to the observed effects. The results implicate that Leca can be used as a filter material with reactive properties provided that moisture content is controlled and that an adequate air velocity is used.

Immobilized fenton‐like ionic liquid: Catalytic performance for oxidative desulfurization

MCM‐41‐supported Fenton‐like ionic liquid catalysts were synthesized by the grafting method and applied in the removal of sulfur compounds in model oil. The structure and property of the catalysts were characterized by Fourier transform infrared spectra, X‐ray diffraction, diffuse reflectance spectra, transmission electron microscopy, thermogravimetric and differential scanning calorimetry, and N2 adsorption‐desorption. Results suggested that Fenton‐like ionic liquid was supported on mesoporous material MCM‐41. Different desulfurization systems were studied. The results indicated that at room‐temperature (30°C) for 1 h, MCM‐41‐supported Fenton‐like ionic liquid in extraction combined with catalytic oxidative desulfurization (ECODS) system showed a high catalytic activity with H2O2 as the oxidant, and [Omim]BF4 as the extractant. Different factors, such as temperature, the amount of H2O2, solvent, and different sulfur‐containing compounds for sulfur removal were investigated. Through the gas chromatography‐mass spectrometer (GC‐MS) analysis, dibenzothoiphene sulfone was proved to be the only product of dibenzothiophene oxidizing reaction. Furthermore, the process of ECODS was confirmed by GC‐MS results. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4696–4704, 2013

Removal of refractory organic sulfur compounds in fossil fuels using MOF sorbents

The stringent new regulations to lower sulfur content in fossil fuels require new economic and efficient methods for desulfurization of recalcitrant organic sulfur. Hydrodesulfurization of such compounds is very costly and requires high operating temperature and pressure. Adsorption is a non-invasive approach that can specifically remove sulfur from refractory hydrocarbons under mild conditions and it can be potentially used in industrial desulfurization. Intensive research has been conducted in materials development to increase their desulfurization activity; however, even the highest activity obtained is still insufficient to fulfil the industrial requirements. To improve the adsorption capacity and sorbent regeneration, more work is needed in areas such as increasing specific desulfurization activity, hydrocarbon phase tolerance, sulfur removal at higher temperature, and development of new porous substrates for desulfurization of a broader range of sulfur compounds. This work comprehensively describes the adsorption of organo-sulfur compounds present in liquid fuels on metal-organic framework (MOF) compounds. It has been demonstrated that the extent of dibenzothiophene (DBT) adsorption at temperatures close to ambient (304 K) is much higher on MOF systems than on the benchmarked Y-type zeolite and activated carbons. In addition, the DBT adsorption capacity depends strongly on the MOF type as illustrated by the much higher extent of adsorption observed on the Cu-(C300) and Al-containing (A100) MOF systems than on the Fe-containing (F300) MOF counterpart.

Desulfurization of Liquid Hydrocarbon Streams via Adsorption Reactions by Silver-Modified Bentonite

Removal of organic sulfur compounds from its solution has been investigated by using adsorption. The purpose of this study is to investigate the removal of dimethyl disulfide (DMDS) in liquid hydrocarbon streams with bentonite modified by Ag+. The addition of Ag+ on the bentonite significantly enhanced the adsorption capacity of DMDS. The adsorbents were characterized by nitrogen adsorption, X-ray diffraction (XRD), and thermal analysis (TGA). Fourier transform infrared (FT-IR) spectroscopy showed that the type and number of surface acidic sites on the adsorbents could increase the adsorption capacity. Several factors that influence the desulfurization capability, including loading, reaction temperature, and calcination temperature, were studied. The maximum sulfur adsorption capacity was obtained at a silver loading of 6 wt %, and the optimum calcination temperature was 150 °C. Spectral shifts of the ν(C–S), ν(S–S), and ν(Ag–S) vibrations of the complex compound obtained by the reaction of Ag+ and DMDS w...

Adsorption and Removal of Sulfur or Nitrogen-Containing Compounds with Metal-Organic Frameworks (MOFs)

Adsorption and Removal of Sulfur or Nitrogen-Containing Compounds with Metal-Organic Frameworks (MOFs)

Imidazolium-based Alkylsulfate Ionic Liquids and Removal of Sulfur Content From Model of Gasoline

Two ionic liquids, butyl-methyl-imidazolium octylsulfate, [BMIM][OCSO4], and ethyl-methyl-imidazolium ethylsulfate, [EMIM][EtSO4], were demonstrated to be effective for the removal of aromatic sulfur compounds such as benzothiophene and thiophene from model of gasoline. Organic compounds with higher aromatic π-electron density were favorably adsorbed by using ionic liquids. It was shown that the extractive ability of the alkylsulfate ILs was dominated by the structure and size of cation and anion. The cation and anion structure and size of ionic liquids are important factors affecting the absorption capacity for aromatic compounds. It is found that [BMIM][OCSO4] has the best effect on the selective removal of sulfur compounds from gasoline. Sulfur extractive selectivity for specified IL followed the order BT>T>3-MT>2-MT.

Pervaporation and Vapor Permeation Tutorial: Membrane Processes for the Selective Separation of Liquid and Vapor Mixtures

Pervaporation and vapor permeation are membrane-based processes proposed as alternatives to conventional separation technologies. Applications range from organic solvent removal from water, ethanol, or butanol recovery from fermentation broths, solvent/biofuel dehydration to meet dryness specifications, and organic-organic separations such as the removal of sulfur compounds from gasoline. Unlike membrane filtration processes, which rely on an applied liquid pressure gradient and size sieving to accomplish a separation, pervaporation and vapor permeation separate compounds based on a chemical activity driving force and the sorption and diffusion of the compounds through the membrane. These properties enable the separation of even miscible liquid mixtures.

Mesoporous titania–silica–polyoxometalate nanocomposite materials for catalytic oxidation desulfurization of fuel oil

A series of mesoporous titania–silica–polyoxometalate (HPW–TiO2–SiO2) nanocomposite materials with different silica–titania ratios were prepared in the presence of non-ionic surfactant by evaporation induced self-assembly method. XRD, TEM, nitrogen adsorption–desorption isotherm and FTIR measurements indicated these materials possess mesoporous structure with relatively uniform channel-like pores and large internal BET surface areas. The incorporated polyoxometalate clusters preserve intact their Keggin structure into the mesoporous frameworks. The nanocomposites were used as catalysts for oxidative desulfurization of model fuel, which was composed of dibenzothiophene (DBT) and hydrocarbon, while H2O2 is used as oxidant. The catalytic oxidation results show that the catalysts are very active in refractory bulky molecule organosulfur compounds in fuel oil. The mesoporous HPW–TiO2–SiO2 also shows high selectivity for DBT oxidation in the presence of benzene and achieved the goal of desulfurization. The surface acid strength and acidic sites were characterized by NH3–TPD and Py-FT-IR. It revealed that Lewis acidic sites play an important role in the removal of organic sulfur compounds from the DBT–petroleum ether–benzene system. After regeneration of used catalysts three times, the activity of catalysts has not obviously decreased.

Investigation of Influential Parameters in Deep Oxidative Desulfurization of Dibenzothiophene with Hydrogen Peroxide and Formic Acid

An effective oxidative system consisting of hydrogen peroxide, formic acid, and sulfuric acid followed by an extractive stage were implemented to remove dibenzothiophene in the simulated fuel oil. The results revealed such a great performance in the case of H2O2 in the presence of formic and sulfuric acids that led to the removal of sulfur compounds. Sulfuric acid was employed to increase the acidity of media as well as catalytic activity together with formic acid. The oxidation reaction was followed by a liquid-liquid extraction stage using acetonitrile as a polar solvent to remove produced sulfones from the model fuel. The impact of operating parameters including the molar ratio of formic acid to sulfur (), hydrogen peroxide to sulfur (), and the time of reaction was investigated using Box-Behnken experimental design for oxidation of the model fuel. A significant quadratic model was introduced for the sulfur removal as a function of effective parameters by the statistic analysis.

Immobilization of room temperature ionic liquid (RTIL) on silica gel for adsorption removal of thiophenic sulfur compounds from fuel

ImCl-silica gel (SG-ImCl) was prepared by directly immobilized [1-methylimidazole][Cl] (ImCl) onto silica gel (SG) using co-condensation of ionic liquid modified organosilane and tetraethoxysilane (TEOS) as silica source in strong acid condition. The properties of the samples were characterized by FTIR, elemental analysis, 29Si MAS NMR, SEM, BET. The results suggested that [1-methylimidazole][Cl] had been successfully immobilized on silica gel. The structure and morphology of SG-ImCl was varied with the content of ImCl. Moreover, SG-ImCl with suitable content of ImCl exhibited higher adsorption capacity than pure SG for a series of thiophenic sulfur compounds and could remove them from fuel.

Removal of sulfur compounds from light fractions of South Uzbek oils

A new method of ridding light fractions of South Uzbek oils of sulfur compounds is described. It is shown that upon oxidation of the sulfur compounds not only their solubility changes, but also their boiling point rises markedly. The boiling points of the oxidized sulfur compounds and the respective hydrocarbons differ by several scores of degrees. This allows separation of oxidized sulfur compounds by fractional distillation. Fractional distillation makes the purification process much simpler compared to the extraction method and reduces energy consumption substantially.

Adsorptive Desulfurization of Natural Gas Using Lithium-Modified Mesoporous Silica

The dynamic adsorption and desorption behaviors of lithium-modified mesoporous silica adsorbents (YSP-Li and MCF-Li) were investigated to remove sulfur compounds from natural gas. A mixture of methane and methyl mercaptan (291 μmol/mol) was used as feed gas. The adsorption capacities were determined from breakthrough experiments conducted at different temperatures and flow rates. The dynamic thermal desorption of both adsorbents was studied by applying stepwise temperature increases using nitrogen or methane. Both adsorbents could easily be regenerated at 100 °C with a purge gas. MCF-Li exhibited stronger adsorption affinity and higher adsorption capacity to methyl mercaptan than YSP-Li even though its surface area and the doping amount of Li were smaller. The desorption from MCF-Li was more affected by the applied purge gas (CH4 or N2) than YSP-Li.

Simultaneous removal of sulphide and nickel by the compound of Chitosan Schiff Base from crude oil under microwave irradiation

A study has been carried out for simultaneous desulfurization and demetalization by electric desalting from crude oil based on the oxidation of alkyl thiophene and nickel compounds with the compound of Chitosan Schiff Base under the condition of microwave irradiation (SDDM). Besides, an investigation has been made about the influence of Chitosan Schiff Base compound dose, initial temperature, and microwave time on desulfurization and demetalization. By using the optimized conditions for SDDM, up to 56% of sulfur and 82% of nickel removal rates were achieved for model compounds in crude oil samples. With the same conditions but without microwave the removal efficiency was lower than 56% for sulfur model compound and than 82% for nickel porphyrin in crude oil samples. Additionally, in order to develop a fundamental understanding of the SDDM mechanism of sulfides, a molecular simulation of sulfur compounds was performed with both the Hartree–Fock (HF) and second-order Moller–Plesset (MP2) levels of theory for the calculation of reaction kinetic rate by using Gaussian 03 program package. In comparison with conventional desulfurization and demetalization technology, the proposed SDDM process can accomplish the simultaneous removal of sulfur and nickel compounds from crude oil under relatively mild conditions.

Enhancement of bunker oil biodesulfurization by adding surfactant

Biodesulfurization (BDS) is a promising method to remove sulfur compounds from diesel and gasoline. However, the information on BDS of heavy oil is scanty, which might be due to their "undesirable" physical properties and more complicated sulfur diversities. In this study, the BDS of one kind of heavy oil, bunker oil MFO380 was investigated. The biocatalyst was obtained by the enrichment with oil sludge as the seed and using dibenzothiophene (DBT) as the sole sulfur source. The enriched biocatalyst (microbial mixed culture) could selectively remove sulfur from DBT and DBT was transformed into 2-hydroxybiphenyl, which indicates that the BDS process is beneficial to non-destructive carbon bonds and thus can maintain the calorific value. The bunker oil BDS results showed that after 7 days of incubation, the removal efficiency of sulfur in MFO380 was only 2.88 %, but this could be significantly improved by adding surfactants Triton X-100 or Tween 20. This effect could be attributed to greatly reduced viscosity of heavy oil and increased mass transfer of sulfur compounds in heavy oil into water. Adding Triton X-100 achieved the highest removal efficiency of sulfur, up to 51.7 % after 7 days of incubation. The optimal amount of Triton X-100 was 0.5 g/50 ml medium. When toluene was added as an organic solvent for MFO380, the BDS activity was improved, while lower than the effect of adding surfactants.

Isolation and characterization of a facultative methanotroph degrading malodor-causing volatile sulfur compounds

Simultaneous removal of methane and malodor-causing volatile sulfur compounds (MVSCs), both emitted from landfills, is a desirable characteristic for methane-mitigation approaches. A methanotrophic bacterium was isolated from a microbial consortium, enriched with methane and dimethyl sulfide (DMS). It grew in the complex nutrient medium R2A without methane, and stably exhibited methanotrophic activity after facultative growth. It was identified as Sphingopyxis sp. MD2 by comparison of the 16S rRNA gene. It belongs to Sphingomonadales, whose members have not shown methanotrophic activity, phylogenetically distinct from orders of known methanotrophs. The MD2 biomass increased at a growth rate of 1.18d−1 when methane was used as the sole growth substrate. An inhibition test with allylthiourea and PCR/sequencing confirmed the presence of particulate methane monooxygenase in MD2. DMS decreased the methane oxidation rate (2634±146μmolegDCW−1h−1) by 12%, while H2S had no effect on the methane oxidation rate. Interestingly, methanethiol (MT) enhanced the methane oxidation rate by more than 50%. MD2 degraded H2S and MT, regardless of the presence of methane. MD2 also degraded DMS in the presence of methane, indicating co-metabolism. These combined results indicate that MD2 may be a promising biological resource for simultaneous removal of methane and MVSCs.

Process Simulation Based on Experimental Investigations for 3-Methylthiophene Alkylation with Isobutylene in a Reactive Distillation Column

A new approach that substitutes the original two-step olefinic alkylation of thiophenic sulfur (OATS) technology with a reactive distillation (RD) column was proposed to remove sulfur compounds from fluid catalytic cracking (FCC) gasoline. 3-Methylthiophene (3MT) and isobutylene (IB) were designated as the model compounds for sulfide and olefin, respectively; NKC-9 cation exchange resin mixed with the 2 mm × 2 mm θ ring packing was used as the catalyst bed. The process parameters such as feed composition, molar ratio of 3MT to IB, and reflux ratio were investigated experimentally in the RD column. Simulation for this process was carried out by using the equilibrium stage model—the RADFRAC module of Aspen Plus. The multicomponent vapor–liquid equilibria were predicted by an UNIQUAC method, and the kinetics model that is essential in the RD process was obtained from our previous work. The key design factors (e.g., number of reactive and nonreactive stages, location of feed stage, column pressure, mass ratio...

Mechanistic Features of Ultrasound-Assisted Oxidative Desulfurization of Liquid Fuels

A new technology for the removal of sulfur compounds from liquid fuels is oxidative desulfurization. Although several studies have reported the enhancement effect of ultrasound irradiation on oxidative desulfurization, the exact mechanism underlying this enhancement is not known yet. In this study, we have addressed this issue with dual approach of coupling experiments with mathematical model for cavitation. Results of this study have given interesting revelation of interaction between mechanism of ultrasound, cavitation, and oxidation system. Isolation of cavitation phenomenon helps to increase the extent of oxidation. This effect is attributed to formation of hydrogen and carbon monoxide during transient collapse of cavitation bubbles due to thermal dissociation of hexane vapor entrapped in the bubble, which hamper the action of O species generated from the oxidation system. Transient cavitation itself does not give rise to radical formation, because of rather low temperature peaks reached during collap...

Deep Desulfurization of Model Oil Using Ionic Liquid and Active Carbon Binary System

Ionic liquid (IL) N-methyl-N-methylimidazoliumdimethyl phosphate ([DMIM][DMP]) and active carbon (AC) binary system were established and demonstrated to be effective for the deep removal of sulfur compounds (Dibenzothiophene, DBT) from model oil at room temperature. Mass ratio of IL to active carbon on the extractive performance, desulfurization temperature, time and desulfurization reagent to model oil were investigated. In the first stage desulfurization efficiency of binary system, IL and active carbon were 65.09%, 51.72% and 47.3%，which was followed the order of binary system > IL > active carbon. It was suitable to carried out desulfurization process with mass ratio of IL to active carbon in 1:1, binary system to model oil in 1:1 for 10 min at 25-45oC. In the optimiazed condition, desulfurization efficiency of binary system was nearly 100% after the fifth stage desulfurization process.