Sulfidation Behavior Research Articles

Behavior of silver sulfide in the system Ag2S-Fe(NO3)3-HNO3-H2O

Behavior of silver sulfide in the system Ag2S-Fe(NO3)3-HNO3-H2O was studied at 25, 55, and 80°C using the method of the simplex-lattice experiment design. The quantitative dependences of Ag2S oxidation on the concentrations of the acid and Fe3+ were determined. The isoconcentration diagrams were obtained.

Electrochemical behavior and composition of bismuth sulfide coatings

Cyclic potentiodynamic voltammetry and X-ray photoelectron spectroscopy were used to study the electrochemical behavior and composition of bismuth sulfide coatings deposited by successive ionic layer adsorption and reaction on glassy carbon in a colloid solution of bismuth(III) compounds, with Na2S as a sulfidizing agent.

Development of iron oxide sorbents for Hg 0 removal from coal derived fuel gas: Sulfidation characteristics of iron oxide sorbents and activity for COS formation during Hg 0 removal

The aim of this study is to develop a process for the removal of Hg 0 using H 2S over iron oxides sorbents, which will be located just before the wet desulfurization unit and catalytic COS converter of a coal gasification system. It is necessary to understand the reactions between the iron oxide sorbent and other components of the fuel gas such as H 2S, CO, H 2, H 2O, etc. In this study, the sulfidation behavior and activity for COS formation during Hg 0 removal from coal derived fuel gas over iron oxides prepared by precipitation and supported iron oxide (1 wt% Fe 2O 3/TiO 2) prepared by conventional impregnation were investigated. The iron oxide samples were dried at 110 °C (designated as Fe 2O 3-110) and calcined at 300 and 550 °C (Fe 2O 3-300 and Fe 2O 3-550). The sulfidation behavior of iron oxide sorbents in coal derived fuel gas was investigated by thermo-gravimetric analysis (TGA). COS formation during Hg 0 removal over iron oxide sorbents was also investigated using a laboratory-scale fixed-bed reactor. It was seen that the Hg 0 removal activity of the sorbents increased with the decrease of calcinations temperature of iron oxide and extent of sulfidation of the sorbents also increased with the decrease of calcination temperature. The presence of CO suppressed the weight gain of iron oxide due to sulfidation. COS was formed during the Hg 0 removal experiments over Fe 2O 3-110. However, in the cases of calcined iron oxides (Fe 2O 3-300, Fe 2O 3-550) and 1 wt% Fe 2O 3/TiO 2, formation of COS was not observed but the Hg 0 removal activity of 1 wt% Fe 2O 3/TiO 2 was high. Both FeS and FeS 2 were active for Hg 0 removal in coal derived fuel gas without forming any COS.

Friction and wear of polyphenylene sulfide composites filled with micro and nano CuO particles in water-lubricated sliding

The tribological behavior of polyphenylene sulfide (PPS) composites filled with micro and nano CuO particles in water-lubricated sliding condition were studied. Pin-on-disk sliding tests were performed against a steel counterface of surface roughness 0.09–0.11 μm. The lubrication regimes were established from friction data corresponding to various combinations of loads and sliding speeds. Later experiments were performed using the sliding speed of 0.5 m/s and contact pressure of 1.95 MPa, which corresponded to boundary lubrication regime. Micro CuO particles as the filler were effective in reducing the wear of PPS but nano CuO particles did not reduce wear. The steady state wear rate of PPS-30 vol.% micro CuO composite was about 10% of that of unfilled PPS and the coefficient of friction in this case was the lowest. The examination of the topography of worn pin surfaces of nano CuO-filled PPS by SEM revealed grooving features indicating three-body abrasion. The transfer films formed on the counterfaces during sliding were studied by optical microscopy and AFM. The wear behavior of the composites in water-lubricated sliding is explained using the characteristics of worn pin surfaces and transfer films on the counterface.

High temperature oxidation–sulfidation behavior of Cr–Al 2O 3 and Nb–Al 2O 3 composites densified by spark plasma sintering

The high temperature oxidation–sulfidation behavior of Cr–Al 2O 3 and Nb–Al 2O 3 composites prepared by mechanical alloying (MA) and spark plasma sintering (SPS) has been studied. These composite powders have a particular metal–ceramic interpenetrating network and excellent mechanical properties. Oxidation–sulfidation tests were carried out at 900 °C, in a 2.5%SO 2 + 3.6%O 2 + N 2(balance) atmosphere for 48 h. The results revealed the influence of the sintering conditions on the specimens corrosion resistance, i.e. the Cr–Al 2O 3 and Nb–Al 2O 3 composite sintered at 1310 °C/4 min showed better corrosion resistance (lower weight gains) compared with those found for the 1440 °C/5 min conditions. For the former composite, a protective Cr 2O 3 layer immediately forms upon heating, whereas for the later pest disintegration was noted. Thus, under the same sintering conditions the Nb–Al 2O 3 composites showed the highest weight gains. The oxidation products were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy.

Reaction of singlet oxygen with some benzylic sulfides

Product distribution, total quenching rate ( k T), and rate of chemical reaction ( k r) with singlet oxygen have been determined for some alkyl, benzyl, α-methylbenzyl, and cumyl sulfides. Their contributions depend on the steric hindering around the sulfur atom. In protic solvents, the sulfoxide is the main product via a hydrogen-bonded persulfoxide. In apolar solvents, intramolecular α-H abstraction leads to oxidative C–S bond cleavage, with varying efficiency. The behavior of sulfides is compared to that of alkenes and amines.

Autocatalysis-like behavior of hydrogen sulfide on hydrodesulfurization of polyaromatic thiophenes over a synthesized molybdenum sulfide catalyst

Abstract Hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene over a synthesized nanosize-MoS 2 catalyst were investigated in a batch reactor. The catalytic activity in hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene increased remarkably with H 2 S being remained in the reaction zone. The HDS reactions of the two substrates over the present catalyst were found to proceed via a network where direct desulfurization and hydrogenation routes are essentially involved. The product contribution from the hydrogenation route is much more pronounced. Isomerized components were also identified. Dibenzothiophene and 4,6-dimethyldibenzothiophene exhibited almost identical results in terms of the reactivity and selectivity. The increase in the catalytic activity with H 2 S is probably due to the increase in the number of the potentially active sites modified by H 2 S. The kinetic investigation of the hydrodesulfurization reactions revealed the autocatalysis-like phenomena attributed to the potentially modified active sites by self-produced H 2 S. TEM image reveals that the synthesized MoS 2 may consist of a bent and/or a closed round layers which might play an important role in such autocatalysis behaviors of H 2 S in the hydrodesulfurization of polyaromatic thiophenes.

High Temperature Sulfidation Resistance of DO3 - Ordered FeAl Tested in H2S-rich Gases

AbstractThe sulfidation behaviour at 973 K in a 30 vol.% H2S-H2-H2O-N2 gas mixture of Fe-25 % at. Al, DO3-ordered alloys, binary or alloyed with niobium, was investigated. Binary alloys presented a quite good sulfidation resistance in comparison with 321 stainless steel, even if a large amount of iron sulfides FeS grew over the alumina layer on corroded samples. The sulfidation resistance of DO3 alloys could be significantly improved by an oxidation treatment prior to corrosion test. The Nb in iron aluminides was supposed to preferably react with S and therefore, to enhance sulfidation resistance through preventing the nucleation and growth of harmful FeS. Unfortunately, the scales of Nb-allloyed FeAl contained only a small amount of Nb3S4 which did not prevent efficiently the formation of iron aluminides FeS. Adding Nb to Fe-25Al even resulted in a severe deterioration of the microstructure during sulfidation due to intense diffusion of S inward the sample.

Precipitation Behavior of Copper, Tin and Manganese Sulfide at High Temperature in Fe-10%Cu-0.5%Sn Alloys

Tramp elements such as Cu or Sn cause a severe hot shortness. Any tramp elements have been rejected and diluted below a certain limit by the use of virgin iron source. On the other hand, the steel properties are improved if Cu precipitates are very fine and uniformly dispersed in steels. Cu is the useful alloying element for increasing hardness and improving of r-value. Recently, it has been found that MnS precipitates have a good positive effect on the heterogeneous precipitation of Cu in grains. In this study a confocal scanning laser microscope with an infrared image furnace was used to carry out the in-situ observation of precipitation behavior at high temperature. To estimate the phase diagram, alloys were analyzed by a differential scanning calorimetry (DSC) method. It is clear that the domain of γFe phase becomes smaller and the domain of the liquid phase becomes larger with the addition of Sn. As a result of observation by the confocal laser microscope, the number of precipitates increased at higher temperatures with MnS than without MnS. The observed precipitates are classified into three types. Type “I” is the Cu (Sn) precipitate at the γFe grain boundary. Type “II” is the precipitate found in the γFe grains. One is the Cu (Sn) and another complex precipitate is composed of εCu, (Mn, Cu) S and Cu7.2S4. Type “III” is the smallest εCu precipitate in the αFe grains. They nucleated after γ/α phase transformation and the size is less than 100 nm.

Effect of partial charge parametrization on the fluid phase behavior of hydrogen sulfide

The effect of partial charge parametrization on the fluid phase behavior of hydrogen sulfide is investigated with grand canonical histogram reweighting Monte Carlo simulations. Four potential models, based on a Lennard-Jones + point charge functional form, are developed. It is shown that Lennard-Jones parameters can be tuned such that partial charges for the sulfur atom in the range -0.40 < q(s) < -0.252 will lead to an accurate reproduction of experimental vapor-liquid equilibria. Each of the parameter sets developed in this work are used to predict the pressure composition behavior H2S-n-pentane at 377.6 K. While the mixture calculation provides a means of reducing the number of candidate parameter sets, multiple parameter sets were found to yield an excellent reproduction of both the pure component and mixture phase behavior.

Sulphide/phosphide precipitation associated with carbon saturation in Ti–15V–3Cr–3Sn–3Al–0.2C

Titanium sulphide precipitates, Ti 3S, and sulphur-enriched titanium phosphide precipitates, Ti 3(P, S), have been observed in a Ti–15V–3Cr–3Sn–3Al–0.2C alloy with sulphur less than 10 wt ppm and phosphorus of about 50 wt ppm. No such precipitates have been found in standard low C (90 ppm) Ti-153. The titanium sulphide has a formula of Ti 3S and an orthorhombic structure with lattice parameters of a = 1.01 nm, b = 0.79 nm and c = 0.32 nm determined using TEM diffraction analysis. The sulphur-enriched titanium phosphide has a formula of Ti 3(P, S) with a P:S ratio of about 2:1. It has the same tetragonal structure as does the Ti 3P and similar lattice parameters. Titanium sulphide precipitates have a well defined orientation relationship with the beta matrix which is ( 0 1 0 ) T i 3 S //{1 3 0} β and [ 0 0 1 ] T i 3 S //〈0 0 1〉 β. Three variants of Ti 3S precipitates, perpendicular to each other, were observed and their habit planes in the beta matrix are {1 3 0}. Ti 3S has a morphology of a thin layer with a thickness along [0 1 0] axis of less than 50 nm and up to 50 and 20 μm in other two axes, respectively. The precipitation behaviour of the titanium sulphide during both continuous cooling and isothermal treatment is strongly affected by the carbon solution in the beta matrix.

EXAFS study on the sulfidation behavior of Pd, Pt and Pd–Pt catalysts supported on amorphous silica and high-silica USY zeolite

The sulfur tolerance of monometallic Pd, Pt and bimetallic Pd–Pt catalysts supported on slightly acidic ultra-stable Y (USY) zeolite (SiO 2/Al 2O 3 = 390) and on non-acidic silica, having mesopores with a pore diameter of 3 or 10 nm, were investigated using the CO adsorption method and the extended X-ray adsorption fine structure (EXAFS) method. Well-dispersed noble metal particles supported on USY zeolite and silica with an average pore diameter of 3 nm showed high surface sulfur tolerance and high catalytic hydrogenation activity, although bulk phase sulfidation simultaneously occurred. The synergistic effects of sulfur tolerance were significant in the bimetallic Pd–Pt particles supported on USY zeolite and silica with an average pore diameter of 3 nm. On the other hand, on silica with an average pore diameter of 10 nm, the surface sulfur tolerance of low dispersed noble metals was the lowest, although its bulk phase sulfur tolerance was the highest. The Pd K-edge and Pt L III-edge EXAFS spectra indicated a strong interaction between the well-dispersed noble metal particles and the supports of the USY zeolite and silica with an average pore diameter of 3 nm. This distorted structure may increase the sulfur tolerance of noble metals, though some surface and bulk phase sulfidation simultaneously occurred.

Thermal Sulfidation Behavior of Ti-Ni Alloys

Ti and Ni sulfides were formed on the surface of Ti-Ni alloys by isothermal annealing at various sulfur pressures, and then microstructures of the surface sulfide layers were investigated by means of scanning electron microscopy and X-ray diffractions. Morphology of sulfurized surface changed from granular shape to porous shape at the sulfur pressure of 80 kPa, which is related to the change in sulfide from NiS1.97 to NiS. Two-layered sulfide was observed in which the inner layer was mainly Ti8.2S11 , and the outer layer was a mixture of NiS1.97 and NiS. The discharge curve of the Ti and Ni sulfides cathode formed on the Ti-Ni current collector at the first cycle showed a plateau voltage of 1.6 V, and the discharge capacity was found to be about 530 mAh/g-NiS1.97.

Friction and wear studies using Taguchi method on polyphenylene sulfide filled with a complex mixture of MoS 2, Al 2O 3, and other compounds

The tribological behavior of polyphenylene sulfide (PPS) filled with molybdenum-concentrate (MC) deposit from Armenia was studied. The deposit MC was a complex mixture of compounds such as MoS 2, SiO 2, CuS, Al 2O 3, and others. Whereas MC as the filler in particulate form reduced the steady state wear rate of PPS, the optimum reduction in wear was found to occur with the addition of polytetrafluoroethylene (PTFE) along with PPS. The behavior of PPS composites made with MC and PTFE sliding against a steel counterface was investigated as a function of the MC and PTFE proportions, sliding speed, and counterface roughness. For this purpose, pin-on-disk configuration and the design of experiments approach utilizing Taguchi's orthogonal arrays were used. Of all the above factors, the change in MC proportion, while PTFE was also present, had the greatest effect on the reduction in wear rate. The variation of the coefficient of friction was found to be in the narrow range of 0.27–0.33. The lowest wear rate was found in the case of PPS + 17 vol.% MC + 10 vol.% PTFE composite sliding at 1.5 m/s against a counterface roughness of 0.1 μm Ra. Optical and scanning electron microscopy of the transfer films were performed for observation of the features such as coverage, thickness, topography, and bonding. Friction and wear results are discussed in terms of these observations.

Behavior of Sulfides of Nonferrous Metals in Hydrochloric-Acid Leaching of Residues Formed in Synthesis of Carbonyl Nickel

Specific features of hydrochloric-acid leaching of residues formed in synthesis of carbonyl nickel without removal and with forced removal of the gas phase were studied.

めっき廃液中の銅，亜鉛およびニッケルの硫化反応による選択的分離回収

Selective recovery of copper, zinc and nickel from electroplating wastewater was studied by precipitating the metal sulfides formed by sulfuration treatment. CuSO4, ZnSO4 and NiSO4 involved in model solutions and those of plating wastewater were adjusted to 100-120mg dm−3 of the initial metal concentration. Two kinds of sulfurating agents, sodium sulfide (Na2S) and sodium hydrosulfide (NaHS) of 6.8×10−2 mol dm−3, were employed.As a result, it was found that Na2S was more effective for the separation of the metal sulfides precipitated. The formation of metal sulfides was dependent on the pH value of the solution. In the sulfuration process using Na2S, copper was first separated from the solution as copper sulfide in pH1.4-1.5, followed by the formation of zinc sulfide in pH2.4-2.5. Subsequently, nickel sulfide was precipitated after the formation of copper and zinc sulfides in the residual solution in pH5.5-6.0.The same results of the formation behavior of copper sulfide, zinc sulfide and nickel sulfide in a simulated plating solution were obtained for those in an electroplating solution.

Effect of transfer film structure, composition and bonding on the tribological behavior of polyphenylene sulfide filled with nano particles of TiO 2, ZnO, CuO and SiC

The tribological behavior of polyphenylene sulfide (PPS) filled with inorganic nano particles was studied. The fillers investigated were TiO 2, ZnO, CuO and SiC whose sizes varied from 30 to 50 nm. The polymer composites were compression molded with varying proportions of these fillers. Wear and friction tests were performed in a pin-on-disk configuration at a sliding speed of 1.0 m/s, nominal pressure of 0.65 MPa, and counterface roughness of 0.10 μm Ra. The polymer composite pins slid against hardened tool steel counterfaces. The transfer films of the composite materials formed on the counterfaces during sliding were studied by optical microscopy and X-ray photoelectron spectroscopy (XPS) and the adhesion between the transfer film and counterface was measured in terms of the peel strength. It was found that the wear rate of PPS decreased when TiO 2 and CuO were used as the fillers but increased with ZnO and SiC fillers. The optimum wear resistance was obtained with 2 vol.% CuO or TiO 2. These filled composites had the coefficients of friction lower than that of the unfilled PPS. The wear behavior of the composites is explained in terms of the topography of transfer film and adhesion of transfer film to the counterface as observed from peel strength studies. There is a good correlation observed between the transfer film–counterface bond strength and wear resistance.

Corrosion Behaviour of Fe-XAl-0.3Y Alloys at High Temperature Sulfidation Environment(Ps2=10-3Pa)

The sulfidation behaviour of Fe-XAl-0.3Y(X=5, 10, 14, 25 <TEX>$wt.\%$</TEX>) alloys was investigated at 1123 K in <TEX>$H_2/H_{2}S$</TEX> gas atmosphere for <TEX>$1\sim24$</TEX> hrs using SEM/EDX, XRD and EPMA. The weight changes of Fe-XAl-0.3Y alloys followed the parabolic rate law, Sulfidation rates of iron aluminide alloys with high Al content were one-twentieth lower than that of 5Al alloys. This is due to the formation of protective <TEX>$Al_{2}O_3$</TEX> oxides on the surface of 10Al, 14Al and 25Al alloys. By calculating partial pressure of impurity oxygen contained <TEX>$H_2/H_{2}S$</TEX> gas, the <TEX>$Al_{2}O_3$</TEX> oxides formation could be explained using Fe-Al-S-O thermodynamic stability diagram. The sulfidation product scales of the 5Al alloy showed that thick iron sulfide scale(FeS) containing porosities formed during early stages of sulfidation. With continued sulfidation, aluminum sulfide was formed at the alloy/scale interface.

The Sulfidation of Inconel 738 in H2/H2S/Ar Gas Mixture at 500–900°C

The sulfidation behavior of the cast nickel-base superalloy Inconel 738 (IN-738) was studied over the temperature range 500–900°C in three various ratios of H2/H2S/Ar atmospheres having sulfur partial pressures in the range 10−4–102 Pa. The sulfidation kinetics followed the parabolic rate law in all cases, and the sulfidation rates increased with increasing temperature and sulfur partial pressure. In general, the scales formed were heterophasic and duplex, consisting of an outer layer composed mostly of nickel sulfides (mostly NiS and Ni3S2, and minor Ni7S6 detected at T > 750°C) plus some CoS2/Co3S4, CoMo2S4, NiCo2S4, and minor chromium sulfide (Cr2S3/Cr3S4), while the inner layer contained a mixture of nickel sulfides and minor amounts ofA12S3 and Cr2S3/Cr3S4. The amount of NiS decreased and that of Ni3S2 increased with increasing temperature. The dependence of the sulfidation rate constants (K p ) and Ps(2)(the n value) was significantly higher at T ≥ 850°C as compared to that measured at lower temperatures (T ≤ 850°C).

Sulfidation behavior of Fe–40Al sheet in H 2–H 2S mixtures at high temperatures

The sulfidation behavior of a 200 μm thick Fe–40at.%Al sheet has been investigated at temperatures between 973 K and 1273 K in H 2–H 2S mixtures with H 2S contents of 0.052–9.7vol%. The Fe–40Al sheet exhibited excellent sulfidation resistance at temperatures below 1073 K in all the H 2S–H 2 mixtures. This may be attributed to the formation of a thin alumina film on the surface of the Fe–40Al sheet during sulfidation, identified by AES analysis. At temperatures higher than 1173 K, the Fe–40Al sheet also exhibited good sulfidation resistance in the 0.052%H 2S–H 2 mixture, and there was only a slight increase in mass gain with temperature. This compares favorably with Fe–20Cr–11Al (in at.%) foil which was severely sulfidized even at 973 K in the 0.052%H 2S–H 2 mixture, and showed markedly increased mass gain with increased H 2S content and temperature.