Adsorption and decomposition of H2S on Pd(1 1 1) surface: a first-principles study

Gradient-corrected density functional theory was used to investigate the adsorption of H₂S on Pd(1 1 1) surface. Molecular adsorption was found to be stable with H₂S binding preferentially at top sites. In addition, the adsorption of other S moieties (SH and S) was investigated. SH and S were found to be preferentially bind at the bridge and fcc sites, respectively. The reaction pathways and energy profiles for H₂S decomposition giving rise to adsorbed S and H were determined. Both H₂S_(ad) → SH_(ad) + H_(ad) and SH_(ad) → S_(ad) + H_(ad) reactions were found to have low barriers and high exothermicities. This reveals that the decomposition of H₂S on Pd(1 1 1) surface is a facile process.     

On the combination of different transport mechanisms for the simulation of steady-state mass transfer through composite systems using permeation through stainless steel supported silicalite-1 membranes as a model system

A method to calculate the steady-state multicomponent mass transfer in heterogeneous structures is presented. For this, different transport mechanisms represent different regions inside the composite system. The solving scheme allows the calculation of the molar flow rates along the different transport pathways and the estimation of unknown transport parameters based on experimental data.

The steady-state mass transfer of hydrogen and sulfur hexafluoride through a sinter metal supported MFI zeolite membrane is examined as a model system. The support is simulated using the dusty gas model, the molecules passing the zeolite layer may follow transport mechanisms like Knudsen diffusion, surface diffusion or activated gas diffusion. The configuration used, with data from single gas experiments, can predict the binary system only at high temperatures. The problems arising at low temperatures are due to the oversimplified assumption that adsorbed and desorbed molecules do not interact on their way through the MFI zeolite micropores.

However, because of the modular structure of the approach, it can be easily extended to more advanced transport models to account for interactions between the different molecules. And the method can be applied equally well to other systems, such as palladium composite membranes or membranes with catalytic activity.     

Preparation and electrochemical properties of sulfur-acetylene black composites as cathode materials

A sulfur-acetylene black (AB) composite was synthesized by thermally treating a mixture of sublimed sulfur and AB. The sulfur-AB composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) tests. From the results, we confirmed that sulfur was well dispersed on nano-scale and embedded inside nano-pores of the acetylene black with the steric chain structure in the composite. The electrochemical performance of the composite as cathode materials was evaluated by the galvanostatic method, cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). The sulfur-AB composite, which can effectively confine the diffusion of dissolved polysulfides in organic electrolyte and stabilize the structure during the charge and discharge process, showed high capacity and good cycle performance. The discharge capacity of the sulfur-AB composite was maintained at 500 mAh/g after 50 cycles.     

Regulated and unregulated emissions from a light-duty diesel engine with different sulfur content fuels

Five different sulfur content fuels were used on a light-duty diesel engine to study the effect of fuel sulfur on emissions. Four regulated emissions: smoke, nitrogen oxide (NO_x), unburned hydrocarbon (HC) and carbon monoxide (CO) emissions of the engine were investigated, as well as three unregulated emissions: formaldehyde (HCHO), acetaldehyde (MECHO) and sulfur dioxide (SO₂). The smoke emission decreases continuously and remarkably with the fuel sulfur content, and the fuel sulfur has more influence on smoke emission at lower engine load. The concentration of NO_x emissions did not change significantly with the different sulfur content fuels. As the fuel sulfur content decreases, the concentrations of HC and CO emissions have distinct reduction. The HCHO emission values are very low. The MECHO emission decreases with increasing engine load, and it continuously decreases with the fuel sulfur content and it could not be detected at higher engine load with 50 ppm sulfur fuel. The SO₂ emission increases continuously with the engine load, and obviously decreases with the fuel sulfur contents.     

吹脱法处理稀土硫氨废水试验研究

针对高氨氮、高硬度,较难处理的稀土硫氨废水,采用吹脱法进行了脱氨试验研究。通过单因素试验得出：在pH=12、吹脱温度T=30℃、吹脱时间t=3h的条件下,氯铵废水氨氮含量可由10383.8mg/L降低到316mg/L,去除率可达96.9%。     

中国煤中硫氮的赋存状态研究

煤中的硫、氮在煤利用转化过程中的释放对环境和生物健康影响巨大。笔者从煤中硫、氮的分布、结构,同位素研究等几方面对中国煤中硫、氮的赋存状态研究进行了总结,并提出了今后的研究方向和热点问题。     

Urea particle coating for controlled release by using DCPD modified sulfur

The shell of sulfur coated urea was easily cracked due to sulfur being friable. Sulfur was modified with dicyclopentadiene (DCPD) to increase its strength and abrasion resistance. SEM images showed that the micro-structure of modified sulfur was denser and more uniform than pure sulfur. The strength of modified sulfur increased with the DCPD/S ratio. Experiments of urea particle coating with sulfur and modified sulfur were carried out in a fluidized bed coater. The shell of coated urea particles with modified sulfur was more compact than that with pure sulfur. The modification retarded the sulfur phase transformation from monoclinic to orthorhombic, avoiding the crack formation in the coating shell of sulfur. The modified sulfur coated urea particles can be produced with thinner shell and higher strength, and had better controlled release properties.     

硫磺汽化管失效原因及对策

通过对原高温硫磺汽化管失效原因的分析,提出了改进管子化学成分的方案,实践证明这一方案是有效的。     

Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in W/O Microemulsion

Sulfur nanoparticles were synthesized from hazardous H₂S gas using novel biodegradable iron chelates in w/o microemulsion system. Fe³⁺–malic acid chelate (0.05 M aqueous solution) was studied in w/o microemulsion containing cyclohexane, Triton X-100 and n-hexanol as oil phase, surfactant, co-surfactant, respectively, for catalytic oxidation of H₂S gas at ambient conditions of temperature, pressure, and neutral pH. The structural features of sulfur nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), diffused reflectance infra-red Fourier transform technique, and BET surface area measurements. XRD analysis indicates the presence of α-sulfur. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in w/o microemulsion system is nearly uniform in size (average particle size 10 nm) and narrow particle size distribution (in range of 5–15 nm) as compared to that in aqueous surfactant systems. The EDS analysis indicated high purity of sulfur (>99%). Moreover, sulfur nanoparticles synthesized in w/o microemulsion system exhibit higher antimicrobial activity (against bacteria, yeast, and fungi) than that of colloidal sulfur.     

Electrochemical gold deposition from sulfite solution: application for subsequent polyaniline layer formation

Electrochemical gold deposition from sulfite solutions was studied by means of voltammetry, EIS and EQCM. A gold film electrode was used for polyaniline layer formation by electrochemical oxidation of aniline. The standard electrochemical reduction potential of the reaction [Au(SO₃)₂]³⁻ + e⁻ = Au + 2 SO₃²⁻ was determined, and is equal to 0.116 V (vs. NHE). Both solution stirring and temperature increase accelerate the electrochemical reduction of gold, when the electrode potential is below −0.55 V. When the potential is above −0.55 V the electrochemical reduction proceeds via passive layer formation. Our study suggests that the passive layer consists of chemically adsorbed sulfite ions and sulfur. The gold film deposited from sulfite solution is a high quality substrate suitable for conducting polymer layer formation. This technique, where a polymer layer electrode is prepared by thin gold film deposition onto a metal surface and by subsequent polymer layer formation, can be applied in sensor research and technology.