Cobalt sulphide catalyst prepared via a new method involving the precipitation reaction between cobaltous acetate and ammonium sulphide solutions has been shown to be favourably active for the catalytic decomposition of H2S when compared with data for other transition metal sulphides.
The BET surface area of this unsupported catalyst is about an order of magnitude higher than cobalt sulphide formed by direct sulphidation of cobalt oxide with H2S gas. XRD, SEM and TEM analyses were used to obtain bulk composition and morphological characteristics. Catalyst specimen calcined at 823 K showed the best activity.
The kinetics of the decomposition reaction has been studied over this new preparation. Experiments conducted at atmospheric pressure between 933-983 K using about 11 feed compositions showed that below 40% H2S/Ar the reaction was essentially 1st order with respect to H2S partial pressure. Beyond this point, rate remained invariant with feed composition. A mechanism involving catalysis via co-ordinative unsaturation sites on the CoS was proposed and kinetic model based on the cleavage of the surface H-S bond as the rate-determining step appeared to be the most adequate representation of the rate data. Hydrogen production rates at all temperatures also paralleled the behaviour seen for H2S decomposition. Activation energy for H2S decomposition and H2 production rates were estimated as 111 kJ mol-1 and 88 kJ mol-1 respectively 相似文献
Methane partial oxidation (MPO) is considered as an alternative method to produce hydrogen because it is an exothermic reaction to afford a suitable H2/CO ratio of 2. However, carbon deposition on a catalyst is observed as a major cause of catalyst deactivation in MPO. In order to find suitable catalysts that prevent the carbon deposition, NiO-MgO/Ce0.75Zr0.25O2 (CZO) supported catalysts were prepared via the co-impregnation (C) and sequential incipient wetness impregnation (S) methods. The amount of Ni loading was fixed at 15 wt-% whereas the amount of MgO loading was varied from 5 to 15 wt-%. The results revealed that the addition of MgO shifted the light-off temperatures to higher temperatures. This is because the Ni surface was partially covered with MgO, and the strong interaction between NiO and NiMgO2 over CZO support led to the difficulty in reducing NiO to active Ni0 and thus less catalytic activity. However, among the catalysts tested, the 15Ni5Mg/CZO (S) catalyst exhibited the best catalytic stability for MPO after 18 h on stream at 750°C. Moreover, this catalyst had a better resistance to carbon deposition due to its high metallic Ni dispersion at high temperature. 相似文献
The removal of low concentrations of hydrogen sulfide by adsorption and catalytic combustion has been studied. Concentration of hydrogen sulfide by adsorption from waste-gas streams is best effected by molecular sieve 13X, if the stream is dry, and by activated carbon, if the gas stream is moist.
Low-temperature catalytic oxidation of hydrogen sulphide in moist gas streams can be effected over activated carbon. The reaction appears to involve ionized hydrogen sulfide, dissolved in water condensed in the pores of the carbon.
At high temperatures, both supported platinum and palladium catalysts are found to be oxidation catalysts. Palladium is the best catalyst for methane oxidation but is partially deactivated in the presence of sulfur-containing gases. In contrast, platinum was more active for the same reaction in the presence of sulfur-containing gases.
Both metals were found to promote the oxidation of hydrogen sulfide above ca. 150°C. The power rate laws describing the kinetics of reaction were determined. 相似文献
TiO2-V2O5 was prepared and evaluated as an energy storage material for photocatalysts with high capacity and initial charging rate. The compound was successfully obtained by sol-gel technique and effects of compound composition and calcination temperature on the energy storage ability were investigated. The synthesized compounds were characterized by means of X-ray powder diffraction (XRD), scanning electron microscopy equipped with energy-dispersive X-ray analysis (SEM-EDX) and transmission electron microscopy (TEM). The results reveals that the compound of Ti:V molar ratio equal to 1:0.11 calcined at 550 degrees C exhibited superior energy storage ability than parent substances and 1.7-times higher capacity and 2.3-times higher initial charging rate compared to WO3, indicating that the compound is a remarkable alternative to conventional energy storage substances. 相似文献
In this study, Ni/Ce0.75Zr0.25O2 catalyst was doped with different amounts of Sn by co-impregnation method. The catalysts were characterized by BET, H2 chemisorption, XRD, TPR, TEM, XPS and tested for iso-octane partial oxidation (iC8POX) to H2 in the temperature range of 400–800 °C at atmospheric pressure. The results showed that most of Sn species were present on the surface of Ni particles and did not modify the reducibility of the support. Addition of a small amount of Sn (<0.5 wt.%) lowered the catalytic activity for iso-octane partial oxidation by less than 5% while the extent of carbon deposition was decreased by more than 50%. However, Sn loadings higher than 1 wt.% caused a massive drop in catalytic activity. This indicates that as long as the Ni surface is only partially covered with Sn species, the active sites for the partial oxidation of iso-octane remain intact, while the surface site ensembles required for carbon formation are blocked. 相似文献
Dye-sensitized solar cells (DSSCs) were fabricated using natural dyes extracted from rosella, blue pea and a mixture of the extracts. The light absorption spectrum of the mixed extract contained peaks corresponding to the contributions from both rosella and blue pea extracts. However, the mixed extract adsorbed on TiO2 does not show synergistic light absorption and photosensitization compared to the individual extracts. Instead, the cell sensitized by the rosella extract alone showed the best sensitization, which was in agreement with the broadest spectrum of the extract adsorbed on TiO2 film. In case that the dyes were extracted at , using water as extracting solvent, the energy conversion efficiency (η) of the cells consisting of rosella extract alone, blue pea extract alone and mixed extract was 0.37%, 0.05% and 0.15%, respectively. The sensitization performance related to interaction between the dye and TiO2 surface is discussed. The explanations are supported by the light absorption of the extract solution compared to extracts adsorbed on TiO2 and also dye structures. The effects of changing extracting temperature, extracting solvent and pH of the extract solution are also reported. The efficiency of rosella extract sensitized DSSC was improved from 0.37% to 0.70% when the aqueous dye was extracted at instead of and pH of the dye was adjusted from 3.2 to 1.0. Moreover, DSSC stability was also improved by the changes in conditions. However, the efficiency of a DSSC using ethanol as extracting solvent was found to be diminished after being exposed to the simulated sunlight for a short period. 相似文献