Sulfur Impregnation on Activated Carbon Fibers through H2S Oxidation for Vapor Phase Mercury Removal

Sulfur was impregnated onto activated carbon fibers (ACFs) through H2S oxidation catalyzed by the sorbent surface in a fixed-bed reactor. By changing the temperature and duration of the sulfur impregnation process, ACFs with different sulfur contents were developed. Characterization of ACFs before and after sulfur impregnation was conducted by surface area analysis, energy dispersive X-ray analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy, and temperature programmed desorption. Vapor phase mercury adsorption experiments were carried out in a fixed-bed reactor. Sulfur was impregnated mainly as elemental sulfur and the amount of sulfur deposited on the ACF increased with an increase in impregnation temperature. Higher temperature leads to more uniform sulfur distribution inside the sorbent pores. The impregnation process can be explained by a combination of pore filling and monolayer adsorption, with the former mechanism predominating at low temperatures. In the absence of sulfur, the mercury adsorption capacity can be correlated with surface area and pore volume.     

Carbonization and graphitization

A review is made of recent electron microscope observations relating to the carbonization and graphitization of a variety of carbonaceous precursors. The different behaviors of graphitizing and non-graphitizing carbons are elucidated, and the effect of sulphur as a cross-linker is determined. The resulting processes are shown to apply to a wide variety of materials ranging from cokes to carbon fibers.     

水泥中硫的高频红外分析方法研究

采用高频红外吸收法测定了水泥中硫的含量,并对样品作测定前的预处理(物理处理),在测定中选用复合型助熔剂,解决了高频感应炉中因顶吹氧气流的作用而导致的样品喷溅问题。该法可准确测定水泥中0.001％～5％的硫,回收率为98.6％～102.5％,RSD为0.78％～1.35％。     

羰基合成原料气中羰基硫、二氧化碳脱除技术的探讨

采用NHD工艺,在近4 MPa的压力下,将羰基合成原料气中的羰基硫与二氧化碳脱除。为降低能耗,进一步优化气体净化流程,设想采用变压吸附工艺,在进压缩机前将二氧化碳脱除。考察了羰基硫与二氧化碳在吸附剂上的选择性。     

炼焦煤与焦炭间硫转化关系的研究

取武钢炼焦生产用煤56种,进行实验室坩埚炼焦实验,研究煤与焦炭间硫的转化关系,以降低焦炭的硫分并合理用煤。研究结果表明,对于单种炼焦煤,煤焦间硫的转化率(ΔS)随挥发分(Vd)的增加而降低,且有较好的相关性;焦炭硫分与炼焦煤硫分的比例系数(ΔS/K)也随挥发分(Vd)的增加而降低。不管是单种炼焦煤还是其配合煤,其焦炭的硫分均随炼焦煤硫分的增加而增加,且有很好的相关性。     

Application of modified montmorillonite for desulfurization during the combustion of hard coal

Series of modified with vanadium, cobalt, nickel, manganese and copper montmorillonite were compared as additives for desulfurization during combustion of hard coal. Samples of coal with added montmorillonite were subject to a 2 h a flow reactor in the air atmosphere, at 1173 K. The weight ratio of montmorillonite:coal was 1:500. Changes in sulfur dioxide contents in flue gasses caused by the additive were investigated by means of an exhaust gas analyzer. During the co-combustion of coal with montmorillonite modified with vanadium was removed 58-84% of SO₂ from flue gasses. Application of Co and Ni led to a reduction in SO₂ emissions by 35-53% and 83-90%, respectively. For additions of Ni, Cu and Mn was observed to reduce emissions of SO₂ by 60-73%. As a result of using diversified preparatory procedures on montmorillonite additives DESOX obtained were materials with different physicochemical properties. Sulfate forms obtained after the combustion process with addition of montmorillonite additives are amorphous and very well dispersed.     

Bismuth sulfide and its carbon nanocomposite for rechargeable lithium-ion batteries

Bi₂S₃ and Bi₂S₃/C nanocomposites prepared by high-energy mechanical milling were evaluated as electrode materials in lithium secondary batteries. For a Bi₂S₃/C nanocomposite, Bi₂S₃ nanocrystallites were well distributed in an amorphous carbon matrix. The reaction mechanism of the Bi₂S₃/C electrode was also examined during the first cycle. The Bi₂S₃/C nanocomposite anode showed superior electrochemical performance (ca. 500 mAh g⁻¹ and 85% of the capacity retention over 100 cycles).     

Kinetic investigation of sulfurized polyacrylonitrile cathode material by electrochemical impedance spectroscopy

To understand more about the sulfur composite prepared by sulfurized polyacrylonitrile at 300 °C, electrochemical impedance spectroscopy (EIS) is employed to investigate the electrochemical properties of the sulfur composite cathode during discharge process. The impact of discharge depth on the performance of sulfur composite materials is investigated. The electrolyte solution resistance, the charge transfer resistance and the interface impedance are evaluated from the EIS analysis. The charge transfer resistance and the interface impedance increase during delithiation and decrease during lithiation, while the concentration of Li⁺ in the composite decreases and increases, respectively. Meanwhile the electrolyte solution resistance is likely to keep stable. The interface resistance and charge transfer resistance of the sulfur composite cathode decrease rapidly after initial lithiation, while Li⁺ diffusion coefficient and exchange current density increase rapidly. After the initial lithiation, they are likely to keep stable. This study reveals more characteristics of the sulfur composite, which is considered to be a promising candidate for large capacity cathode material.     

New insight into the interaction of sulfur with diesel NOx storage catalysts

A commercial NO_x-storage catalyst (NSC) has been subjected to different aging procedures on the engine bench simulating 100,000 km mileage. The aging consisted of cyclical sulfur exposure, subsequent sulfur removal and testing of the catalytic activity. More aggressive desulfation procedures result in more efficient sulfur removal and consequently good high temperature NO_x-conversion. However, low temperature NO_x-performance is lower than for agings employing more moderate desulfation conditions.

Sulfur post mortem analyses reveal a slight decrease of residual sulfur concentration over the length of all catalysts after completion of the aging. BET and CO-chemisorption data are in line with the increase of temperature from catalyst inlet to outlet during the desulfation. The conversion of BaCO₃ to BaSO₄ during the sulfur poisoning was followed by IR, TPD and TPR. A quantitative analysis of the data shows that at the end of the agings all residual sulfur is mainly located at barium sites as opposed to other oxide components like e.g. alumina or ceria. TPR data suggest that prolonged rich purges of the sulfated catalyst lead to an efficient decomposition of sulfates however some sulfur is being trapped in the form of BaS which seems difficult to remove under constant rich conditions.

XPS data suggest that the bulk sulfur amounts in the catalyst may be decoupled from the actual concentration at the catalyst surface. In that sense, the residual sulfur concentration might be limited in some cases as a criterion to assess the performance of a NSC. More reducing desulfation conditions cause the residual sulfur to be present in the form of more reduced sulfur species (sulfites, sulfides) on the catalyst.