Showing papers on "Cobalt sulfide published in 2002"
TL;DR: In this article, the authors investigated the effect of high calcination temperatures on the sulfidation performance of CoW and NiW model catalysts and found that the HDS activity of NiW/Al2O3 is a factor 5−6 times higher than for W/Al 2O3.
Abstract: The interaction of Co (or Ni) and W with the Al2O3-support influences the sulfidation behavior and thiophene hydrodesulfurization (HDS) activity of CoW and NiW model catalysts. High calcination temperatures retard the sulfidation of Co, Ni, and W to high temperature and lead to incomplete sulfidation at 400 °C. In bimetallic catalysts, the presence of W prevents the strong interaction of Co and Ni with the Al2O3 support and partially blocks the diffusion of Co and Ni into the support, thereby facilitating the sulfidation of Co and Ni. For CoW/Al2O3 catalysts bulk cobalt sulfide and WS2 are formed during sulfidation and hence no promotion effect is observed. However, the HDS activity of NiW/Al2O3 is a factor 5−6 times higher than for W/Al2O3. This strong promotion effect is ascribed to the formation of the NiWS phase by redispersion of preformed bulk Ni sulfide to the edges of WS2 slabs as observed with X-ray photoelectron spectroscopy (XPS). Both the calcination and sulfidation temperature have a strong i...
81 citations
TL;DR: In this paper, a co-impregnation of K2CO3/Co-MoS2 on activated carbon was described by X-ray diffraction (XRD) and BET, which showed that cobalt and molybdenum sulfides are found in the Co3S4 and Co9S8 phases.
Abstract: Supported K2CO3/Co–MoS2 on activated carbon was prepared by a co-impregnation technique and has been characterized by X-ray diffraction (XRD) and BET. Active ingredients ranged from 39 to 66% and included molysulfide and cobalt sulfide. XRD analysis indicates that cobalt and molybdenum sulfides are found in the Co3S4 and Co9S8 phases. These catalysts were performance tested in a fixed-bed reactor under higher alcohol synthesis conditions, 2000–2400 psig and 270–330 °C. Active chemicals on the carbon extrudates decreased the surface area dramatically, as measured by BET. Surprisingly, at the high level of active chemicals, alcohol productivity and selectivity were decreased. An increase in the reaction temperature led to a decrease in the selectivity of methanol and an increase in selectivity of hydrocarbons. Total alcohol productivity was also increased as gas hourly space velocity (GHSV) was increased. Co9S8 may play a role in the catalyst aging process. In prolonged reaction periods (140 h), sulfur is lost from the surface, possibly as H2S. The quantity of Co9S8 on the surface appears to increase as the catalyst ages.
51 citations
TL;DR: In this paper, a modified chemical bath deposition with cobalt dichloride (CoCl2) and sodium sulfide (Na2S) aqueous solutions was performed on glass substrates using X-ray diffraction and scanning electron microscopy.
48 citations
TL;DR: In this paper, Cobalt-containing mixed sulfide with the structure of MoS 2 was prepared, having a specific surface area of 75m 2 ǫg −1 and demonstrating a high activity in the thiophene hydrodesulfurization (HDS) model catalytic test.
20 citations
TL;DR: In this article, the effect of electrolyte solution on the output characteristics of a photoelectrochemical cell based on cadmium selenide and cobalt sulfide was studied.
Abstract: Results of spectrophotometric measurements in concentrated polysulfide solutions used as electrolytes in regenerative photoelectrochemical transducers are presented. The equilibrium constants are determined and the distribution of ions species in the solutions is calculated. The effect of electrolyte solution on the output characteristics of a photoelectrochemical cell based on cadmium selenide and cobalt sulfide was studied.
12 citations
TL;DR: In this paper, the interaction between the Co sulfide coating formed on a glassy carbon electrode and Cu(I)-ammonia complexes solution was investigated by cyclic voltammetry.
Abstract: The interaction between the Co sulfide coating formed on a glassy carbon electrode and Cu(I)-ammonia complexes solution was investigated by cyclic voltammetry in 0.1 M KClO4, 0.1 M NaOH and 0.05 M H2SO4 solutions. It was determined that, after treating the cobalt sulfide coating formed by two deposition cycles with Cu(I)-ammonia complexes (0.4 M, pH 8.8–9.0, τ=180 s, T=25±1°C), an exchange occurs between the coating components and Cu(I). Copper(I) substitutes 75% of the Co(III) compounds present in the coating (~1.81×10–7 mol cm–2) because of Cu2O (1.36×10–7 mol cm–2) formation. The rest of the Co(II) and Co(III) sulfide compounds are also replaced by copper with formation of Cu2–
x
S with a stoichiometric coefficient close to 2 (~1.9). After modifying the cobalt sulfide coatings with Cu(I) ions, the total amount of metal (Co+Cu) increases, owing to the sorption of Cu(I) compounds. In addition, the number of deposition cycles decreases from 3 to 1.5 [1 cycle involves cobalt sulfide layer formation and 0.5 cycle is attributed to modifying by Cu(I) ions]. The coatings modified in the above-mentioned manner may be successfully used for plastic electrochemical metallization as Cu2–
x
S coatings formed by three deposition cycles.
10 citations
Patent•
28 Mar 2002
TL;DR: In this article, a method for recovering cobalt oxide from waste cobalt sludge by dissolving Co completely and removing Mn due to addition of suitable reagents(H2SO4, H2O2, Na2S, etc.) and control of reaction condition(pH).
Abstract: PURPOSE: Provided is a method for recovering cobalt oxide from waste cobalt sludge by dissolving Co completely and removing Mn due to addition of suitable reagents(H2SO4, H2O2, Na2S, etc.) and control of reaction condition(pH). CONSTITUTION: The method for recovering pure cobalt oxide is as follows: calcining waste cobalt sludge generated from petrochemical industry to oxidize cobalt and remove impurities; reacting the oxidized cobalt sludge with 4 equivalent of H2SO4, and adding 5-10vol.%(based on the amount of H2SO4) of H2O2 slowly to improve dissolution of cobalt oxide; filtering to remove insoluble impurities and adjusting the pH of filtrate to be pH5.5 with an alkali for removal of Al, Fe, Cu, etc.; adjusting the pH of Co solution containing Mn to be less than pH1, and adding Na2S or (NH4)2S, for separation of Mn resulted from precipitation of cobalt sulfide(CoS); washing and calcining at high temperature in air.
2 citations
TL;DR: In this article, it was shown that a cobalt sulphide coating formed by two cycles (one cycle includes the treatment of the surface with the solution of Co(II) ammoniate complex: hydrolysis of the adsorbed Co-II compounds; and sulphidation (in Na 2 S solution) of the products of the hydrolyse) contain ∼15% CoS, which in 0.1 M KClO 4 solution is reduced in the region of potentials of hydrogen evolution, and Co hydroxosulphide.
Abstract: Cobalt sulphide coatings formed by two cycles (one cycle includes the treatment of the surface with the solution of Co(II) ammoniate complex: hydrolysis of the adsorbed Co(II) compounds; and sulphidation (in Na 2 S solution) of the products of the hydrolysis) contain ∼15% CoS, which in 0.1 M KClO 4 solution is reduced in the region of potentials of hydrogen evolution, and Co hydroxosulphide. Reduction of the latter occurs at the potentials from -0.4 to -0.8 V in 0.1 M KClO 4 solution and in the potential region 0.2 - 0.3 V in 0.05 M H 2 SO 4 . The reduction occurs in the solid phase and is reversible. After treating such a coating with a solution of Cu(II) ions, only CoS interacts with Cu(II), giving, as a result of redox and exchange processes, Cu 2-x S.
1 citations
TL;DR: In this article, cyclic voltammetry was used to investigate cobalt sulfide coatings by means of X-ray photoelectron spectroscopy, and they were shown to contain CoS(OH), CoS and Co(OH)2 after treating them with AgNO3 solution.
Abstract: Cobalt sulfide coatings have been investigated by means of cyclic voltammetry in 01 M KClO4 and 01 M NaOH solutions and analyzed using X-ray photoelectron spectroscopy They have been shown to contain CoS(OH), CoS and Co(OH)2 After treating such Co sulfide coatings with AgNO3 solution, their composition changes: both the cobalt and oxygen content decreases and Ag (up to 85 at%) appears in the coating as Ag2S, Ag2O and metallic Ag Co(II) compounds react with Ag+ ions according to an exchange reaction [CoS+2Ag++2H2O→Ag2S+Co(OH)2+2H+] In the course of the reaction of Co(OH)2 with silver ions, a redox process occurs, giving metallic silver [Co(OH)2+Ag++H2O→Ag°+Co(OH)3+H+ or Co(OH)2+Ag+→Ag°+CoO(OH)+H+] Ag2S reduction takes place at more positive potentials than Cu reduction; therefore sulfide layers of cobalt modified with silver ions, unlike unmodified ones, may be plated with Cu from both acid and alkaline electrolytes
1 citations
01 Jan 2002
TL;DR: In this paper, the effect of electrolyte solution on the output characteristics of a photoelectrochemical cell based on cadmium selenide and cobalt sulfide was studied.
Abstract: Results of spectrophotometric measurements in concentrated polysulfide solutions used as elec- trolytes in regenerative photoelectrochemical transducers are presented. The equilibrium constants are de- termined and the distribution of ions species in the solutions is calculated. The effect of electrolyte solution on the output characteristics of a photoelectrochemical cell based on cadmium selenide and cobalt sulfide was studied. Concentrated sulfide-polysulfide solutions are com- monly used as electrolytes that can stabilize the op- eration of photoelectrochemical transducers (PECT) based on cadmium chalcogenides. It is believed that sulfide ions are oxidized by holes from the valence band
TL;DR: In this paper, an increase in both the cycle number of cobalt sulphide coating formation and the temperature of Co(II) ammonia solution leads to the increase in mass of both cobalt sulfide coatings and Co in it.
Abstract: An increase in both the cycle number of cobalt sulphide coating formation and the temperature of Co(II) ammonia solution leads to the increase in mass of both cobalt sulphide coatings and Co in it. The mass of cobalt sulphide coating increases with time when they are exposed to air. The reason for this is that Co(II) sulphide compounds formed when Co(II) reacts with S 2 , are oxidised by atmospheric oxygen to Co(III) compounds. The electrical resistance of Co sulphide coating formed by 7 cycles is equal to 10 7 Ω cm -2 , however, in contrast to widely used Cu 2-x S coatings, they may be successfully over-plated with nickel even if they are formed only by one cycle.