Effect Of Sulfiding Temperature Research Articles

Effect of sulfidation temperature on component transformation and catalytic performance of direct coal liquefaction catalyst

A series of iron sulfide catalysts were prepared in 5% H2S/N2 atmosphere at different pre-sulfidation temperatures, and their catalytic activity for naphthalene hydrogenation was studied at 360°C in 1% H2S/H2 atmosphere at 5MPa. The component transformation of the catalyst under varied pre-sulfidation temperature and reaction conditions was researched using MES, XRD and XPS. The results revealed that the sulfidation process was in the form of sulfurizing from surface to interior in the order of FeS2→FeS, Fe1−xS→Fe3S4→Fe2O3 during which transferring sulfur to the body phase was benefited from the rise of temperature. After contacting 1% H2S/H2 gas, the particles rapidly transformed to Fe1−xS from outside to the inside. By adjusting sulfidation conditions, the Fe1−xS content was high while the particle size was small, which made it possible to obtain the greatest activity of the catalyst.

Effect of sulfidation temperature on the catalytic activity of MoO3/CeO2–Al2O3 toward sulfur-resistant methanation

The effect of sulfidation temperature on the catalytic activity of MoO3/CeO2–Al2O3 toward sulfur-resistant methanation was studied. The prepared catalysts were characterized by N2 physisorption (BET), X-ray diffraction (XRD), Raman spectroscopy (RS), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The XRD and XPS results indicated that CeO2 was sulfided at sulfidation temperatures above 500°C. During sulfidation at 500°C or above, Ce3+ ions diffused into the catalyst, and/or Al3+ ions migrated to the surface of the catalyst. These two changes enhanced catalyst stability and decreased catalytic activity. The initial catalytic activity decreased as the sulfidation temperature increased. This decrease occurred for the following reasons: the decrease in BET surface area, the undesired sulfidation of CeO2 on the surface, and the crystallization of amorphous MoS2 to form MoS2 crystals. Finally, CeO2 and MoO3 sulfidation mechanisms were proposed for temperatures greater than 500°C.

Effect of sulfidation temperature on the catalytic behavior of unsupported MoS2 catalysts for synthetic natural gas production from syngas

Unsupported MoS2 catalysts were obtained by thermal decomposition of ammonium tetrathiomolybdate (ATM) or ammonium heptamolybdate (AHM) using sulfur powder as sulfiding agent at variable sulfidation temperature (400–550°C). The CO conversion, selectivity and yield of CH4 on the catalysts were studied for the methanation reaction. It was found that CO conversion increased with temperature rise at first, reached maximum value at sulfidation temperature of 450°C and then decreased sharply with further increase of temperature. The catalyst derived from ATM could get higher CO conversion than the catalyst from AHM because of the structural similarity between ATM and MoS2. XRD analysis demonstrated that amorphous MoS2 was favorable for the methanation reaction and a crystal transition of MoS2 nanoparticle happened during the methanation reaction. The higher the sulfidation temperature was, the more easily regular crystal structure of MoS2 formed. TEM characterization results showed that at the optimum sulfidation temperature of 450°C, the length and stacking degree of MoS2 crystallite were the highest and so more active sites could reside on the edges of MoS2 slabs for CO methanation. The crystal growth of MoS2 particle and its structure change are probably the reasons for the deactivation of the MoS2 catalysts with the increase of sulfidation temperature. In addition, it is the loss of surface sulfur that caused deactivation of the catalyst with reaction time.

Effect of sulfidation temperature on CoO–MoO3/γ-Al2O3 catalyst for sulfur-resistant methanation

The effect of sulfidation temperature on the catalytic activity of CoO–MoO3/γ-Al2O3 catalyst toward sulfur-resistant methanation was studied. The prepared catalysts were characterized by N2-physisorption (BET), Temperature-programmed sulfidation (TPS), X-ray diffraction (XRD), Raman spectroscopy (RS), and Transmission electron microscope (TEM). The combined results of TPS, XRD, and RS indicated that CoMoO4 species in CoO–MoO3/γ-Al2O3 catalyst would be sulfided when the sulfidation temperature was at or higher than 300 °C. The catalyst sulfided at 400 °C exhibited the highest catalytic activity because there were the most CoMoS structures in the catalyst. When the sulfidation temperature was higher than 400 °C, the catalytic activity decreased with increasing sulfidation temperature. This decline was primarily caused by the formation of Co9S8 and MoS2 crystals. The CoMoS(II) formation did not favor the catalytic activity, because the formation of this species resulted in the occurrence of Co9S8 and crystalline MoS2 in catalysts.

Effect of sulfidation temperature on the intrinsic activity of Co–MoS 2 and Co–WS 2 hydrodesulfurization catalysts

The effect of presulfidation temperature on the magnetic property, local structure, and intrinsic hydrodesulfurization activity of Co–Mo(W)–S has been studied with SiO 2-supported Co–Mo and Co–W sulfide catalysts prepared by exposing presulfided MoS 2/SiO 2 and WS 2/SiO 2, respectively, to a vapor of Co(CO) 3NO. A TPS study shows that complete sulfidation of Mo(W) precursors to Mo(W)S 2 particles is required for the formation of Co–Mo(W)–S Type II. The intrinsic activity of Co–W–S Type II is 1.6 times as high as that of Co–Mo–S Type II. The Co K-edge EXAFS analysis of Co–Mo(W)–S confirms the formation of dinuclear Co sulfide clusters on Mo(W)S 2 edges. The intrinsic activity of Co–Mo–S is correlated with the Co–S–Co antiferromagnetic interaction strength, suggesting modifications of the electronic state and local structure of Co–Mo–S by MoS 2–O-support interactions, in conformity with the EXAFS analysis.

Thin pyrite (FeS 2) films prepared by thermal-sulfurating iron films at various temperatures

The structure and morphology of polycrystalline FeS 2 thin films prepared by sulfurating iron films sputtered on glass substrates are reported. The effect of sulfidation temperature on the formation of the FeS 2 thin films has been investigated under 80 kPa sulfur pressure and 20 h annealing time. There is a nearly complete transformation from iron into polycrystalline FeS 2 between 400–600°C sulfidation. Moreover, the film of 400°C sulfidation has approximate FeS 2 stoichiometrical composition and uniform microstructure. With tile increase in sulfidation temperature, the grain size and amount of FeS 2 crystallises increase.

Effect of sulfiding temperature on the initial activity of [formula omitted] catalysts used for the upgrading of an Australian coal-derived liquid

Effect of sulfiding temperature on the initial activity of [formula omitted] catalysts used for the upgrading of an Australian coal-derived liquid

Effect of Sulfiding Temperature on Activity and Structures of CO‐MO/AL2O3 Catalysts. ii

AbstractThe changes, which take place in the structural and catalytic properties of Co‐Mo/Al2O3 catalysts sulfided at different temperatures, have been elucidated by means of high resolution electron microscopy (HREM), ir, XRD, and chemisorption of oxygen. It was observed that high temperature sulfiding induces a growth in the Co‐Mo‐S crystals which are MoS2‐like with Co occupying edge positions. For all the catalysts, Co‐Mo‐S was found to be the most important feature in determining the HDS activity and it was found that the changes, which occur with the HDS activity, can be explained in terms of the changes in the total MoS2 edge area and its Co coverage. When saturation edge coverage is exceeded, segregation of excess Co in the form of Co9S8 takes place. Differences in the hydrogenation activity can be explained in terms of variations in the relative number of promoted vs. unpromoted MoS2 edge sites. Upon increasing the sulfiding temperature, the nature of the Co‐Mo‐S structure changes from a low temperature form (Type I Co‐Mo‐S) to a high temperature form (Type II Co‐Mo‐S). It is suggested that support interactions are less important for Type II Co‐Mo‐S than for Type I.

Effect of sulfiding temperature on dispersion and chemical states of the components of cobalt-molybdenum and nickel-molybdenum

Effect of sulfiding temperature on dispersion and chemical states of the components of cobalt-molybdenum and nickel-molybdenum