气相色谱法定量分析气体中二氧化硫

本试验采用气相色谱方法，以防吸附处理的Restek Sulfur（φ2mmφ2000mm）填充柱，5μL定量管，程序控制，自动阀进样方式对二氧化硫标准气体进行采样分析，拟合绘制标准曲线，得到曲线的线性方程为log[SO2]-0．6672log（Peak Area）-1．2653，R=0．9963。通过对吸收液的吸收及再生过程进行采样分析，得出此方法可对实验气体的连续采集，实时测定，这将为后序的气液平衡数据的采集提供数据来源。该方法操作简便，能够准确、快速的测定气体中的二氧化硫的含量，减少了人为注样过程引起的误差。     

Reduction of carbon dioxide in 3-dimensional gas diffusion electrodes

Experiments on the electrochemical reduction of CO₂ were carried out by using a Cu/PTFE-bonded gas diffusion electrode (GDE) to investigate the effect of solvents, Cu/C ratio and electrolyte concentration on the characteristics of reduction products The experimental conditions were a voltage range from -2 0 to -3 5 V vs saturated calomel electrode (SCE) and electrolyte concentration from 0 1 M to 0 5 M Significant performance differences were found between water and organic solvent (isobutanol + EtOH) The GDE was more active with water than that with organic solvent And then, in the case of the Cu/PTFE-bonded gas diffusion electrode using organic solvent, the maximum faradaic efficiencies of reduction products were achieved in a Cu/C ratio of 0 5 The faradaic efficiency of C₂H₄ among the reduction products decreased as the Cu/C ratio increased, whereas, those of CO and alcohol increased Since the difference in pH at the electrode influences the variation of product selectivity, the faradaic efficiency of C₂H₄ might increase due to the pH increase caused by electrolyte concentration difference     

Observed electrochemical oscillations during the oxidation of aqueous sulfur dioxide on a sulfur modified platinum electrode

The electrochemical oxidation of aqueous sulfur dioxide has been investigated on a sulfur modified polycrystalline platinum electrode. It has been found that time and potential-based current oscillations occur on a modified electrode in the oxidation region >0.7 V vs. SHE. The oscillation is specific to catalytic oxidation on sulfur modified platinum and is not observed on an unmodified electrode. Using i–R compensation techniques, the oscillation has been found to stem from electrochemical origins; the interfacial potential being an essential variable. The influence of other controllable variables including holding potential, sulfur dioxide concentration and sulfuric acid concentration have also been investigated for their effects on the oscillation. The electrochemical oscillation is explained here in part by the intermediate formation of dithionate. Two possible mechanisms, including a dual pathway mechanism, are explored.     

The electrochemical oxidation of aqueous sulfur dioxide: A critical review of work with respect to the hybrid sulfur cycle

Literature regarding the mechanism of the electrochemical oxidation of aqueous sulfur dioxide to sulfuric acid has been critically evaluated to provide a detailed understanding of the reaction under various applied conditions. This reaction is of high relevance to the hybrid sulfur cycle for large scale hydrogen production, as well as other industrial applications such as flue gas desulfurisation. Widespread disagreement in the literature and non-reproducible behaviour of the electrochemical oxidation reaction has been found in this review to often be a result of poorly defined electrode preconditioning procedures. It has also been found that the mechanistic pathway of the oxidation reaction is heavily influenced by the electrode material, solution pH and the applied anodic potential. These factors are thought to influence adsorption and the reductive formation of sulfur species at low potentials.     

Activation of monolithic catalysts based on diatomaceous earth for sulfur dioxide oxidation

The formation of the active phases during the activation process of monolithic catalysts based on V₂O₅–K₂SO₄ supported on diatomaceous earth for SO₂ to SO₃ oxidation in flue gases, has been shown to be a crucial factor to achieve satisfactory catalytic performance. As the temperature is increased from room temperature to 470°C, SO₂ and SO₃ are taken up by the green catalyst and the precursors are transformed into the active species. The role of each component of the catalyst during the activation was analyzed by studying the behavior towards SO₂ adsorption of four materials, which contained: diatomaceous earth, diatomaceous earth + V, diatomaceous earth + K, and diatomaceous earth + V + K. The influence of the potassium sulfate accessibility in the green catalyst was studied by using two different preparation methods, which gave rise to differences in the catalysts SO₂ adsorption properties and catalytic performance. Furthermore, the influence of the activation atmosphere was studied using nitrogen, oxygen or a flue gas composition. It was shown that pyrosulfate species should be formed at temperatures below 400°C, to keep the vanadium in the active 5+ oxidation state.     

ADA氧化法脱硫堵塔原因分析及对策

主要阐述了改良蒽醌二磺酸钠(ADA)脱硫原理及系统运行过程中的积硫原因,对如何控制溶液组分及磺化酞菁钴(OMC)的添加,避免脱硫吸收塔挂壁和塔板积硫进行了分析,并提出整改措施。     

Characteristics of carbon dioxide hydrogenation in a fluidized bed reactor

Characteristics of CO₂ hydrogenation were investigated in a fluidized bed reactor (0.052 m IDxl.5 m in height). Coprecipitated Fe-Cu-K-Al catalyst (d_ρ=75–90 Μm) was used as a fluidized solid phase. It was found that the CO₂ conversion decreases but the CO selectivity increases, whereas the space-time-yield attains maximum values with increasing gas velocity. The CO₂ conversion has increased, but CO selectivity has decreased with increasing hydrogenation temperature, pressure or H₂/CO₂ ratio in the fluidized bed reactor. Also, the CO, conversion and olefin selectivity appeared to be higher in the fluidized bed reactor than those of the fixed bed reactor. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University     

气相色谱法定量分析气体中二氧化硫

本试验采用气相色谱方法，以防吸附处理的Restek Sulfur（Ф2mm×2000mm）填充柱，5μL定量管，程序控制，自动阀进样方式对二氧化硫标准气体进行采样分析，拟合绘制标准曲线，得到曲线的线性方程为log[SO2]=0．667210g（Peak Area）-1．2653，R=0．9963。通过对吸收液的吸收及再生过程进行采样分析，得出此方法可对实验气体的连续采集，实时测定，这将为后序的气液平衡数据的采集提供数据来源。该方法操作简便，能够准确、快速的测定气体中的二氧化硫的含量，减少了人为注样过程引起的误差。     

An experimental investigation into uncatalyzed oxidation of toluene and pseudocumene by sulfur dioxide

The uncatalyzed oxidation of toluene and pseudocumene by sulfur dioxide has been studied at pressures ranging from 200 to 300 atm; and at tempratures from 250 to 350°C. It was found that under these conditions, toluene is readily oxidized and that the main oxidation product is benzoic acid. Pseudocumene, however, oxidizes to mono- and di-carboxylic acids rather than to trimellitic acid. Power law rate equations are proposed for the two oxidations. Activation energy for toluene oxidation is estimated to be 47.6 Kcal/gm. mole while for pseudocumene oxidation the value is 71.2 Kcal/gm. mole.     

Electrochemical reactivity of aqueous SO2 on glassy carbon electrodes in acidic media

The electrochemical reactivity of dissolved SO₂ on glassy carbon (GC) electrodes was studied in sulfuric and perchloric acid solutions. The surface changes accompanying voltammetric scans were analysed with the aid of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The influence of the GC pretreatment (polished versus electrochemically activated) on the oxidation of SO₂ was examined. It was found that GC samples electrochemically treated so to develop a reduced graphite oxide film on the surface were more active for SO₂ oxidation. The reduction of SO₂ was observed to take place at potentials below 0.0 V to yield soluble sulfide species. This species was reoxidized on positive scans to form a sulfur deposit, consisting of an underlying layer of chemisorbed sulfur (161.9-162.3 eV) and an on-top layer of bulk elemental sulfur with S₈-like structure (163.6-163.8 eV). Surface sulfur did not impart electrocatalytic activity for the oxidation of SO₂.     

Catalytic wet air oxidation of phenol in concurrent downflow and upflow packed-bed reactors over pillared clay catalyst

An experimental study is presented for comparing the behavior of a packed bed reactor in the catalytic liquid-phase oxidation of aqueous phenol with two modes of operation, downflow and upflow. The operating parameters investigated included temperature, reactor pressure, gas flowrate, liquid hourly space velocity and feed concentration. Because of the completely wetted catalyst, the upflow reactor generally performs better for high pressures and low feed concentrations when the liquid reactant limitation controls the rate. The interaction between the reactor hydrodynamics, mass transfer, and reaction kinetics is discussed. For both operation modes, complete phenol removal and significant total organic carbon (TOC) reduction can be achieved at rather mild conditions of temperature (150-170 °C) and total pressure (1.5-3.2 MPa). The results show that the phenol and TOC conversion are considerably affected by the temperature, while the air pressure only has minor influence. Total elimination of TOC is difficult since acetic acid, as the main intermediate, is resistant to catalytic wet oxidation. All tests were conducted over extrudates of Fe-Al pillared clay catalyst, which is stable and maintains its activity during the long-term experimental process. No significant catalyst deactivation due to metal ion leaching and polymer deposition was detected.     

Conversion of sulfur dioxide to sulfate and hydrogen sulfide by Desulfotomaculum orientis

The autotrophic, sulfate-reducing bacterium, Desulfotomaculum orientis, grew in batch culture with molecular hydrogen (H₂) as an energy source, carbon dioxide (CO₂) as a carbon source and sulfur dioxide (SO₂) as the terminal electron acceptor. At high H₂ partial pressure, SO₂ was stoichiometrically reduced to hydrogen sulfide (H₂S). At low partial pressures of hydrogen (< 0.025 atm), SO₂ was both oxidized to sulfate and reduced to hydrogen sulfide. These results indicated a new mode of sulfur metabolism for D. orientis.     

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。     

Theoretical and experimental studies of the effect of side reactions in copper deposition from dilute solutions on packed-bed electrodes

This paper analyses the effect of side reactions, such as the reduction of oxygen or Fe(III), on copper deposition from dilute acid sulfate solutions. Fundamental studies with a rotating disc electrode were performed to determine the potential regions where the reactions take place and also to calculate kinetic parameters under the conditions of the experiments. Applied studies carried out in a through-flow electrochemical reactor with a packed bed cathode formed by a stack of nets are reported. The experimental data are compared with theoretical results, according to the continuous model, to corroborate its reliability for the case of simultaneous electrochemical reactions. It was found that the agreement between the mathematical treatment and the experimental data is similar to the case of a single reaction in the electrode. Taking into account the side reactions, criteria for the selection of bed thickness parallel to the current flow are discussed.     

焦炭硫含量的技术经济研究

以6m焦炉及2 800m3高炉的实际生产作业数据为对象,研究了焦炭硫含量对焦炭质量指标、高炉操作指标、铁水质量指标的影响,同时研究了焦炭硫含量变化对焦炭成本、铁水成本的综合影响。     

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％。     

Electrochemical oxidation of benzene and biphenyl in liquid sulfur dioxide: formation of conductive deposits

The electrochemical oxidation of benzene and biphenyl in liquid SO₂ on a platinum electrode results in the formation of passivating films when performed in the presence of a quaternary ammonium perchlorate as a background electrolyte. In contrast, when the electrolyte is a quaternary ammonium tetrafluoroborate, dendrite-like conducting deposits are obtained. Elemental analyses, ir and xps spectra show that the films and deposits are products of the polyphenylene type containing variable amounts of oxygen. The oxidation product of benzene obtained in the presnece of BF₄^? is not conductive in the dry state when it is purified and exempt from electrolyte (σ < 10^?8 Ω^?1 cm^?1), whereas the unpurified product is fairly conductive in the dry state (σ = 10^?3 Ω^?1 cm^?1).     

Electrochemical oxidation of 1,3,5-trimethoxybenzene in aqueous solutions at gold oxide and lead dioxide electrodes

A kinetic study of the electrochemical oxidation of 1,3,5-trimethoxybenzene (TMB) by direct electron transfer at treated gold disk was combined with results of electrolysis in order to produce total degradation into CO₂ and H₂O at Ta/PbO₂ anode. The oxidation of TMB at gold electrode was studied by cyclic voltammetry. The cyclic voltammogram shows one irreversible anodic peak (I) corresponding to the oxidation of adsorbed TMB molecules. The proposed mechanism is based on the hypothesis of two-electron oxidation of TMB molecule leading, via intermediate of a radical cation, to the formation of the 2,4,6-trimethoxyphenol (TMP) and an adsorbed polymeric film. The TMP molecule undergoes a rapid oxidation leading to the formation of 2,6-dimethoxy-p-benzoquinone (DMBQ) as a major product. Degradation of TMB was studied by galvanostatic electrolysis using Ta/PbO₂ anode. The influence of initial TMB concentration and applied current density was investigated. Measurement of total organic carbon (TOC) and analysis by HPLC were used to follow this degradation. The experimental data indicated that the removal of TMB follows a pseudo first-order kinetic. The efficiency of the electrochemical process increases at lower current density and higher TMB initial concentration while it decreases with the TOC removal progress.     

Effect of sulfur in catalytic partial oxidation of methane over Rh–Ce coated foam monoliths

A potentially important technology to convert natural gas to syngas is catalytic partial oxidation (CPO) over precious metal catalysts. However, natural gas contains small amounts of sulfur compounds which can poison the catalyst. It is therefore of interest to investigate the effect of sulfur on the performance of CPO. In this work CPO experiments have been performed over Rh–Ce coated foam monoliths with CH₃SH added to methane. The result of ppm levels of sulfur is a large (C) temperature increase, along with lower methane conversion and lower hydrogen selectivity. A doubling of the sulfur level from 14 to 28 ppm does not result in significant changes, showing that the effect saturates at a few ppm. The poisoning effect has been investigated by analyzing both effluent and spatially resolved data and is shown to be due to severe hindrance of steam reforming by adsorbed sulfur.