Sulfur Impurities Research Articles

Unveiling the effects of doping small nickel clusters with a sulfur impurity

Small free-standing Ni clusters have been widely investigated during the last decade, but not many of their derived chalcogenides, despite their interest in technology and the new prospects that the nanoscale may open. The present work uncovers the effects of the S-doping on the structural, electronic, and magnetic properties of $$\hbox {Ni}_n$$ , n = 1–10 clusters. Density functional theoretical calculations within the generalized gradient approximation for the exchange and correlation were conducted to explore the structural, electronic, and magnetic properties of the resulting $$\hbox {Ni}_n\hbox {S}$$ chalcogenide nanoparticles. The sulfur impurity is always adsorbed on the threefold hollow sites available on the nickel host, in qualitative agreement with recent results of S adsorption on Ni(111) surfaces. S-doping tends to enlarge the average Ni–Ni inter-atomic distance but enhances the thermodynamical stability of Ni clusters. It also increases the vertical ionization energy and electron affinity. However, S-doping has a small effect on the magnetism of small Ni clusters. According to the spin-dependent HOMO–LUMO gap, most of these clusters are good candidates as molecular junctions for spin filtering at low bias voltage.

Влияние примесей серы и фосфора на длительную прочность монокристаллов сплава ЖС36-ВИ при испытаниях на базе до 1000 часов

Влияние примесей серы и фосфора на длительную прочность монокристаллов сплава ЖС36-ВИ при испытаниях на базе до 1000 часов

Continuous Measurement of Odorant Composition for Liquefied Petroleum Gas

In Chile, commercial liquefied petroleum gas (LPG) is customarily odorized with dimethyl sulfide (DMS) and tert-butyl mercaptan (TBM) at a rate of about 10 grams of odorant per 1 cubic meter of LPG. The current control of the odorization practice involves the human nose to detect the odor in some cases, and the determination of total sulfur concentration in others. None of those methods provide the speciation of the sulfur species in LPG.On the other hand, both DMS and TBM are higher boiling than propane or butane. Therefore, the odorant concentration emanating from the odorized liquid is not uniform in the vapors released. Furthermore, the gas will also be much leaner than the odorized liquid. For those reasons, the Chilean industry recommends analyzing the odorant directly from the liquid phase.To address the problem of odorant quantification at the industry this research aims to develop a reliable and objective measure for odorized LPG that allow not only verify the odorization itself but also quantify the species incorporated with the fuel, and other sulfur compounds present naturally in the LPG. In this regard, an Automated Gas Chromatograph (Auto-GC) with an electrochemical detector was coupled with an LPG valve, which continuously takes samples of 1 µL of liquid propane. The extracted sample is then vaporized and injected into the Auto-GC to be analyzed.The methodology is capable of distinguishing and quantifying distinct odorants near real-time (within 8 minutes), as well as other sulfur impurities present in the LPG such as tetrahydrothiophene (THT) and methyl mercaptan (MeSH). Typical retention times for TBM and DMS corresponded to 282 s and 418 s respectively. More importantly, the proposed method provides meaningful information to verify the optimum odorization, i.e., the minimum value to alert in case of leak and maximum level that assures efficient combustion.

Sulfur – induced embrittlement in high-purity, polycrystalline copper

Tensile tests were carried out in high-purity, polycrystalline copper alloys with three concentrations of sulfur impurities (14, 27 and 7920 at ppm) at temperatures between 20 °C and 400 °C. The ductility drops with increasing sulfur concentration and temperature while the ultimate tensile strength increases. The alloys exhibit a grain size of several millimeters and contain mostly random grain boundaries (GBs). The microstructure and composition is investigated by transmission electron microscopy (TEM) and atom probe tomography (APT). The microstructure of the samples with sulfur contents of 14 and 27 ppm consists of globular grains and neither of the microanalytical techniques employed reveals the formation of Cu-sulfides or sulfur segregation to GBs. Even after annealing at 500 °C, no sulfide formation or sulfur segregation to GBs was detected. In the alloy with a sulfur content of 7920 ppm, a dendritic structure is observed and in the interdendritic region monoclinic Cu2S precipitates with a size range from 5 nm to several μm are observed at GBs and also within the grains. The influence of S on the ductility is discussed considering the TEM and APT results.

Molecular dynamics simulation for desulphurization of hydrocarbon fuel using ionic liquids

Ionic liquids, forming a newer class of green solvents, have shown potential in solvent extraction due to their remarkable physical and chemical properties, which can be tailored for specific tasks. Ionic liquids are one of the potential extractants for desulphurization of crude oil to produce ultra-low sulphur fuels. However, due to the constraints of economic feasibility and the broad domain of Ionic liquids, their varying affinity towards sulphur impurities along with the overall expensive methods of production, limit the selection of an Ionic Liquid that provides optimum extraction rates. We investigated the biphasic extraction of two sulphur compounds, thiophene and dibenzothiophene (DBT) from dodecane by using ionic liquid systems of ethyl methyl imidazolium (EMI) and butyl methyl imidazolium (BMI) cations; and tetrafluoroborate (BF4) and thiocyanate (SCN) anions. The molecular arrangement and extraction mechanism of both sulphur compounds at the interface of dodecane-ionic liquid system are studied by molecular dynamics (MD) simulations. We observed that electrostatic interactions between the aromatic plane of sulphur compounds and cations of ionic liquids are the major forces responsible for the extraction of sulphur compounds.

Simulation, exergy analysis and optimization of a shale oil hydrogenation process for clean fuels production

Because of high contents of unsaturated hydrocarbons, sulfur, nitrogen and other impurities in shale oil, its potential use as an alternative fuel is limited. Shale oil hydrogenation technology is an efficient technique for upgrading shale oil to remove heteroatomic compounds. The whole shale oil hydrogenation process is modeled and simulated firstly in this paper, including embedding the kinetic models of hydrogenation reactions. The corresponding-state group contribution method is applied to estimate the physical properties of the components of shale oil. The performance of the shale oil hydrogenation process is analyzed by exergy analysis. The results indicate that the exergy efficiency of the shale oil hydrogenation process is about 69.20%. The energy bottleneck is the furnaces and compressors because the energy consumption of these devices is 59% and 24% of that of the shale oil hydrogenation process. Furthermore, to optimize the performance of this process, the key parameters of the process are investigated and optimized. The preferable reaction temperature of the hydrorefining and the hydrocracking reactors is 350–375 °C and 375–400 °C. The reaction pressure and catalyst grading ratio are suggested to 16–17 MPa and 1:3:3 for maximizing the yield of products with ultra-low nitrogen and heteroatomic compounds.

A XANES Study of Sulfur Speciation and Reactivity in Cokes for Anodes Used in Aluminum Production

Availability of anode raw materials in the growing aluminum industry results in a wider range of petroleum cokes being used to produce carbon anodes. The boundary between anode grade cokes and what previously was considered non-anode grades are no longer as distinct as before, leading to introduction of cokes with higher sulfur and higher trace metal impurity content in anode manufacturing. In this work, the chemical nature of sulfur in five industrial cokes, ranging from 1.42 to 5.54 wt pct S, was investigated with K-edge XANES, while the reactivity of the cokes towards CO2 was measured by a standard mass loss test. XANES identified most of the sulfur as organic sulfur compounds. In addition, a significant amount is identified (16 to 53 pct) as S-S bound sulfur. A strong inverse correlation is observed between CO2-reactivity and S-S bound sulfur in the cokes, indicating that the reduction in reactivity is more dependent on the amount of this type of sulfur compound rather than the total amount of sulfur or the amount of organic sulfur.

Unexpected pressure induced ductileness tuning in sulfur doped polycrystalline nickel metal

The sulfur induced embrittlement of polycrystalline nickel (Ni) metal has been a long-standing mystery. It is suggested that sulfur impurity makes ductile Ni metal brittle in many industry applications due to various mechanisms, such as impurity segregation and disorder-induced melting etc. Here we report an observation that the most ductile measurement occurs at a critical sulfur doping concentration, 14 at.% at pressure from 14 GPa up to 29 GPa through texture evolution analysis. The synchrotron-based high pressure texturing measurements using radial diamond anvil cell (rDAC) X-ray diffraction (XRD) techniques reveal that the activities of slip systems in the polycrystalline nickel metal are affected by sulfur impurities and external pressures, giving rise to the changes in the plastic deformation of the nickel metal. Dislocation dynamics (DD) simulation on dislocation density and velocity further confirms the pressure induced ductilization changes in S doped Ni metal. This observation and simulation suggests that the ductilization of the doped polycrystalline nickel metal can be optimized by engineering the sulfur concentration under pressure, shedding a light on tuning the mechanical properties of this material for better high pressure applications.

Hexane Aromatization: Analysis of the K-Edges of S and K Provides New Insight into H2S Poisoning of Pt/KL

The purpose of this investigation was to examine the effect of sulfur impurity on 1%Pt/KL-zeolite catalyst by co-feeding 500 ppbv hydrogen sulfide (H2S) during hexane aromatization under industrially relevant conditions using a plug flow reactor. Product selectivity and hexane conversion were measured with time-on-stream and compared to a clean run carried out under otherwise identical conditions. Sulfur addition to the feed accelerated the rate of deactivation as observed by rapid declines in both hexane conversion and benzene selectivity; hexene selectivity, the product of the less structurally sensitive dehydrogenation reaction, increased significantly. After 20 h, which was enough time to observe sufficient deactivation, the reaction was stopped. For the purpose of catalyst characterization, after cooling to 150 °C, the catalyst was preserved in Polywax 725 to prevent catalyst oxidation. XANES analysis at the potassium K-edge suggests that the local environment for potassium was not significantly altered by sulfur addition, while sulfur K-edge results indicate that sulfur bound to platinum to form platinum sulfide (PtS, not PtS2). Platinum sulfide is likely responsible for accelerating Pt growth, as observed in DRIFTS of adsorbed CO and HR-TEM/STEM micrographs.

Corrosion behaviour of electrodeposited nanocrystalline nickel-iron (NiFe) alloys in dilute H2SO4

Electrodeposited nanocrystalline and conventional polycrystalline NiFe alloys of similar iron content were investigated to understand the effect of grain size on the corrosion behaviour of these materials. Potentiodynamic polarization testing in 1N H2SO4 revealed similar active-passive-transpassive behaviour with negligible differences in the Tafel and transpassive regions regardless of grain size. It is shown that differences in the region of active dissolution are the result of strong contributions of sulfur impurities in the nanocrystalline electrodeposits rather than being due to grain size alone.

Comparison of different cyclic organic carbonates in the oxyalkylation of various types of lignin

The synthetic versatility and the low toxicity of cyclic alkyl carbonates has driven a wider interest in their use to access new biobased and environmentally friendly polymer building blocks, especially as alkylating reagents. Here, we report for the first time, the synthesis of biobased polyols from lignins of different sources (hardwood, softwood, annual plants) and pulping processes (organosolv, kraft, soda) by oxyalkylation with ethylene (EC), propylene (PC), butylene (BC) and glycerol carbonate (GC). The synthesis of lignin polyols was performed using optimized conditions regarding catalysts, catalyst-to-biomass ratio, reaction time, temperature and amount of cyclic carbonates. To better understand the oxyalkylation of the various types of lignins using different cyclic organic carbonates, the generated polyols were comprehensively characterized by FTIR, 1H, 13C, and 31P NMR spectroscopy as well as size exclusion chromatography (SEC). Emphasis was set on the hydroxyl amount, the degree of substitution (DS) and the alkyl chain. This oxyalkylation strongly facilitates the generation of a uniform lignin polyol equipped with two alkyl units on the aliphatic and phenolic hydroxyl groups. Higher degrees of substitution were achieved using cyclic organic carbonates in the following order EC>GC>PC>BC, reaching a maximum of DS 0.96 for a hardwood kraft lignin. Additionally, the influence of ash, sulfur and polysaccharide impurities as well as lignins molar masses was elucidated.

Rational Design of a Water-Storable Hierarchical Architecture Decorated with Amorphous Barium Oxide and Nickel Nanoparticles as a Solid Oxide Fuel Cell Anode with Excellent Sulfur Tolerance.

Solid oxide fuel cells (SOFCs), which can directly convert chemical energy stored in fuels into electric power, represent a useful technology for a more sustainable future. They are particularly attractive given that they can be easily integrated into the currently available fossil fuel infrastructure to realize an ideal clean energy system. However, the widespread use of the SOFC technology is hindered by sulfur poisoning at the anode caused by the sulfur impurities in fossil fuels. Therefore, improving the sulfur tolerance of the anode is critical for developing SOFCs for use with fossil fuels. Herein, a novel, highly active, sulfur‐tolerant anode for intermediate‐temperature SOFCs is prepared via a facile impregnation and limited reaction protocol. During synthesis, Ni nanoparticles, water‐storable BaZr0.4Ce0.4Y0.2O3− δ (BZCY) perovskite, and amorphous BaO are formed in situ and deposited on the surface of a Sm0.2Ce0.8O1.9 (SDC) scaffold. More specifically, a porous SDC scaffold is impregnated with a well‐designed proton‐conducting perovskite oxide liquid precursor with the nominal composition of Ba(Zr0.4Ce0.4Y0.2)0.8Ni0.2O3− δ (BZCYN), calcined and reduced in hydrogen. The as‐synthesized hierarchical architecture exhibits high H2 electro‐oxidation activity, excellent operational stability, superior sulfur tolerance, and good thermal cyclability. This work demonstrates the potential of combining nanocatalysts and water‐storable materials in advanced electrocatalysts for SOFCs.

Thermal analysis and kinetics of the oxidative roasting process of a copper smelter dust

As a result of the increasing global demand for refined copper, the reserves of primary sources of copper have been decreasing at a tremendously fast rate; which thus makes secondary copper processing an ever-increasing importance within the global copper industry. Copper smelter dust (CSD) is a potential secondary source of copper that is produced during copper pyrometallurgy. The significant amount of copper value these CSDs often plays host to prompts the need to develop processes to meaningfully remove sulfur and other associated impurities from it, prior to subsequent treatment in the copper recovery process. Hence, this present work carried out a thermal analysis and kinetic study on the oxidative roasting process of copper smelter dust under non-isothermal condition in air using DSC-TGA equipment. The non-isothermal experiments were carried out at heating rates of 5, 10, 15, and 20 °C/min, from room temperature up to 1000 °C. The intermediate phases formed in each stage of the oxidative roasting of the CSD were identified. After the first weight loss step, sulfate compounds were mainly formed in the second stage, and approximately 48% of sulfur contained in the metallurgical waste was removed. In the third stage, the sulfur removal reaction was carried out; the rest of sulfur was nearly removed in this stage. Kinetics of the third stage was analyzed from the dynamic DSC-TGA data by means of Coats and Redfern equation. The nucleation and growth model yielded a satisfactory fit to these experimental data.

Molecular composition of organic impurities in extrapure sulfur

We have determined the molecular composition of organic impurities in extrapure sulfur obtained by the distillation purification of sulfur recovered from gaseous hydrocarbons. Using vacuum extraction, we obtained a concentrate of impurities highly volatile compared to the major component. Gas chromatography/ mass spectrometry analysis indicated the presence of impurities in the form of hydrocarbons with up to eight carbon atoms and their thio, oxy, and nitro derivatives. The detection of this group of impurities accounts for the distinctive features of the preparation of sulfur with low carbon and oxygen contents through ultrapurification of gas-derived sulfur.

Waste Valorization Process: Sulfur Removal and Hematite Recovery from High Pressure Acid Leach Residue for Steelmaking

The current study put the emphasis on developing a novel and environmentally friendly waste valorization process to refine hematite from the residue of the high-pressure acid leaching (HPAL) of nickel laterite ore. The developed process consists of an alkaline leaching step utilizing sodium hydroxide to reduce the sulfur impurity content in the HPAL residue. This novel process is very efficient as it can be run at room temperature in a significantly short residence time (10 min). The refined HPAL residue has sulfur content below the accepted threshold by the steelmaking industry; hence, it can potentially be used as a raw material. The proposed waste valorization process has the double advantage of generating a commercially valuable product from otherwise a waste stream and simultaneously providing environmental benefits through reducing the amount of scrapped leach residue and costs associated with constructing and maintaining storage facilities.

Raman-spectroscopic investigation of sulfate ion concentration change in a continuously stirred tank reactor during the preparation of a cathode material precursor

The concentration of sulfate ions was continuously monitored by Raman spectroscopy during the preparation of cathode material precursors. The obtained spectra were used for the quantitative analysis of sulfate ions by comparison with a reference solution, and a gradual increase of sulfate ion concentration was detected. Using a mathematical approach, a time-dependent equation describing sulfate ion concentration was theoretically derived, and the calculated concentrations were compared with the measured ones, showing good agreement between these values. Due to the increased sulfate ion concentration, the metal hydroxide cathode precursor became more contaminated with elemental sulfur. Two as-obtained hydroxide powders with different sulfur impurity contents were calcined with a lithium source, producing cathode materials. Electrochemical analysis of the prepared cathode materials showed that morphological aspects (such as particle size) more highly affected the cathode performance more than the sulfur impurity content.

Defect Dominated Charge Transport and Fermi Level Pinning in MoS2/Metal Contacts.

Understanding the electronic contact between molybdenum disulfide (MoS2) and metal electrodes is vital for the realization of future MoS2-based electronic devices. Natural MoS2 has the drawback of a high density of both metal and sulfur defects and impurities. We present evidence that subsurface metal-like defects with a density of ∼1011 cm–2 induce negative ionization of the outermost S atom complex. We investigate with high-spatial-resolution surface characterization techniques the effect of these defects on the local conductance of MoS2. Using metal nanocontacts (contact area < 6 nm2), we find that subsurface metal-like defects (and not S-vacancies) drastically decrease the metal/MoS2 Schottky barrier height as compared to that in the pristine regions. The magnitude of this decrease depends on the contact metal. The decrease of the Schottky barrier height is attributed to strong Fermi level pinning at the defects. Indeed, this is demonstrated in the measured pinning factor, which is equal to ∼0.1 at defect locations and ∼0.3 at pristine regions. Our findings are in good agreement with the theoretically predicted values. These defects provide low-resistance conduction paths in MoS2-based nanodevices and will play a prominent role as the device junction contact area decreases in size.

Damage associated with the interaction between hydrogen and microstructure in a high sulfur 17-4PH steel for studs

A great number of failure cases of precipitation hardenable 17-4PH steels have been described in the literature. Structural components working in harsh environments failed due excessive hardness. A maximum hardness of 33 HRC was specified for service in aggressive media. However, high impurity levels and chromium carbide precipitation may cause failure, even when the correct final heat treatment is applied and the hardness is below the maximum limit. This fact is investigated in this work, where a 17-4PH steel with 0.027%S was evaluated after hydrogen cathodic charging. Specimens with three different commercial heat treatments were evaluated. Specimens with treatments A (solution treated) and H900 (aged for the peak of hardness) showed inter and transgranular microcracks, pores and cracks associated with sulfide inclusions. Specimen with treatment H1150 (overaged), with low hardness, experienced intergranular attack and pores nucleation in the inclusions. The high sulfur steel was also more susceptible to pitting corrosion, which can also contribute to the hydrogen embrittlement process in high chloride solutions. It is recommended to limit the sulfur and other impurities contents to values lower than those specified by the usual standards.

Identification of uranium signatures relevant for nuclear safeguards and forensics

The paper describes the applicability of different characteristics (signatures) in nuclear safeguards and forensics for assessment of uranium material provenance in terms of production process. The study follows a uranium ore concentrate production from an ore to a U3O8 product. It turned out that rare-earth elemental pattern, radiochronometry (age of ore body and material production date), sulphur and organic impurities are useful to find out the origin or history of the material, while certain trace-elements and isotopics of Pb or Sr were found to be inconclusive. The results will be important to understand the signatures in nuclear safeguards and forensics.

ОБ ОБЛАГОРАЖИВАНИИ ВЫСОКОСЕРНИСТОГО МАЗУТА АСТРАХАНСКОГО ГАЗОВОГО КОНДЕНСАТА

The process of catalytic hydroprocessing of residual gas-condensate raw materials is one of the ways to improve the quality and expand the product assortment of the enterprise. Hydrocatalytic technology of refining high-sulphur fuel oil includes the process of heat treatment, when hydrogen is acting as a reagent under high pressure in the presence of catalysts, which reduces the concentration of impurities (metals, sulphur and nitrogen compounds) in the product. The article offers and substantiates operation principles of catalytic hydrogenation of fuel oil in the Astrakhan gas processing plant, and main technological parameters of the process. There has been carried out the preliminary economic assessment the qualified processing 500 t/year of fuel oil. To develop the technology for qualified fuel oil processing there has been created an experimental setup, which is operating under high pressure. The scope of major parameters of experimental research has been defined. Astrakhan fuel oil refining using hydrogenation catalytic process allows to obtain the high quality oil product with sulphur content less than 1% of mass. Using the hydrogenate is feasible as a marine fuel component, because it helps to decrease environmental burden from combustion product emissions.