Catalytic oxidation of hydrogen sulphide by air over an activated carbon fibre

Activated carbon fiber (ACF), FN-200CF-15, made from coal tar, oxidized hydrogen sulphide effectively to sulphuric acid at an inlet concentration of 200 ppm and space velocity (SV = flow rate/packing volume) of 100 h⁻¹ (sulphur load 11 g-S/day kg-fiber) for one and a half months only by keeping the moisture content of ACF more than 50%. This phenomenon is different from granular activated carbon (GAC) reported previously.     

Direct oxidation of hydrogen sulphide to sulphur using impregnated activated carbon catalysts

Low concentrations of H₂S were directly oxidized to sulphur and small quantities of SO₂, over seven different activated carbons with or without impregnation. The effectiveness of virgin activated carbon was tested at 175°C, 700 kPa, and O₂/H₂S ratio with 5% greater than stoichiometry. The conversion of H₂S was 99.9 mol% with SO₂ production of 3–6%, for 360 min runtime for Fisher coconut shell activated carbon and 648 min for Envirotrol bituminous (EB) activated carbon. Then the activated carbons became deactivated due to deposition of sulphur on the surface. Under these conditions mesoporous activated carbons such as EB and Hydrodarco had the longest breakthrough time. The addition of 5.5 wt% ammonium iodide, potassium iodide and potassium carbonate individually to EB decreased the production of SO₂ while having minimal effect on the overall H₂S conversion. The addition of 5.5 wt% NH₄I decreased the average SO₂ production from 2.5% to 0.9%. The activation energy for the H₂S oxidation on the 5.5 wt% NH₄I on EB activated carbon was determined to be 40 kJ/mol.     

Catalytic oxidation of hydrogen sulphide on activated carbons

Activated carbon is a suitable adsorbent for removal of hydrogen sulphide from natural, synthesis or other product gases. The process depends predominantly on physical adsorption, though catalytic oxidation is also involved. During catalytic oxidation the H₂S is converted in the presence of oxygen to elemental sulphur, which is adsorbed onto the internal surface of the activated carbon, thus leading to a sulphur load of up to 120% by weight. The oxidation rate depends on the partial pressure of both reactants, H₂S and O₂ and is largely controlled by the characteristics of the activated carbon. The activity of the catalyst can be improved by impregnating the activated carbon with promoters such as iron and iodine. The regeneration of spent carbon is currently carried out using hot gas desorption methods at temperatures around 450 °C.     

二氧化钛基催化剂催化氧化甲醛的研究进展

甲醛（HCHO）是一种主要的室内空气污染物,具有高致癌性和致突变性,催化氧化是一种理想而有效的室内消除甲醛的方法。二氧化钛作为载体负载贵金属催化剂在甲醛催化氧化反应中表现出优良的催化性能。本文综述了近年来二氧化钛基催化剂催化氧化甲醛的研究进展,主要总结了二氧化钛的吸附机理,二氧化钛晶体结构、表面形貌及微观结构、表面活性氧物种和还原性等对二氧化钛基负载贵金属催化剂催化氧化甲醛性能的影响,重点关注了催化剂的化学结构性质与甲醛氧化活性的关系,并归纳了一部分甲醛催化氧化反应机理。最后指出二氧化钛基催化剂在甲醛催化氧化反应中未来研究方向为：合理设计TiO₂各种缺陷和晶面暴露,同时提高贵金属的分散性和原子利用效率,继而进一步提高催化剂的性能;在保持催化剂高活性、高稳定性的同时,推进设计实际应用整体式催化剂的研究进程。     

Influences of surface functional groups on catalytic activity over activated carbon catalysts for sulfur dioxide removal from flue gases

The catalytic oxidation of sulfur dioxide in flue gases over activated carbon catalysts was studied. Catalysts made from different materials or by different methods were markedly different. The catalysts were characterized by BET isotherms and X-ray power diffraction. The acidic and basic sites and/or strength on the catalysts were determined by temperature-programmed desorption, while surface functional groups were determined by X-ray photoelectron spectroscopy. The catalytic activity depended on oxygen-containing surface functional groups with Brønsted basicity properties. These groups on a furfural residue activated carbon could be increased by a suitable treatment to enhance the catalytic activity but other catalysts in this study showed no activity enhancement with a similar treatment.     

Photocatalytic decomposition of acetaldehyde in air over titanium dioxide

The photocatalytic decomposition of acetaldehyde in air at initial concentrations ranging from 3 to 200 mg m⁻³ has been studied in a semitransparent closed box with an inlet volume of 0.056 m³. The photocatalytic reactors consisted of a glass tube, 250 mm long with inside diameters of 28, 35, or 45 mm, whose inner surface was coated with a thin film of titanium dioxide, and a 6‐W blacklight fluorescent lamp located at the axis of the glass tube. The decomposition of acetaldehyde was almost complete within 1–3 h and its main product was carbon dioxide. A kinetic study showed that the photocatalytic reaction obeys a Langmuir adsorption isotherm. Although the light intensity was certainly decreased with the distance from the light source, the degree of this decrease was much smaller than the degree of the decrease in the kinetic constants, which suggests that the light intensity is not simply proportional to the degree of the photo‐excitation of TiO₂ and the rate of the resulting photocatalytic decomposition of acetaldehyde. © 1999 Society of Chemical Industry     

活性炭载体对TiO2/AC光催化降解苯酚影响研究

分别以典型煤基活性炭和椰壳活性炭为载体,采用溶胶-凝胶法制备了TiO2/AC复合光催化剂,采用低温氮气吸附、X射线衍射、扫描电镜等对其性能进行了表征,分析了活性炭载体对复合光催化剂性能的影响.结果表明:TiO2在椰壳活性炭载体上的负载率高于煤基活性炭,TiO2负载使椰壳活性炭的比表面积和微孔容明显减小,TiO2溶胶对微...     

Selective oxidation of secondary amines over titanium silicalite molecular sieves,TS-1 and TS-2

Titanium silicalite molecular sieves, TS-1 and TS-2 having MFI and MEL structures, respectively, catalyze the oxidation of secondary amines to the corresponding hydroxylamines using hydrogen peroxide as the oxidant. Higher concentrations of H₂O₂ lead to further oxidation of hydroxylamine to nitrone. Diffuse reflectance spectroscopy shows the formation of a titanium peroxo complex upon addition of hydrogen peroxide to the TS-1 catalyst. The titanium peroxo complex oxidizes the substrate and reforms to a titanyl group.     

Kinetics and reaction mechanism of catalytic oxidation of low concentrations of hydrogen sulfide in natural gas over activated carbon

The kinetics of the hydrogen sulfide oxidation process, producing mostly sulfur and water, was studied using 0.25 to 1.0 g Hydrodarco activated carbon catalyst and varying the O₂/H₂S ratio (molar basis) in the feed gas between 0.5 to 0.6 in the temperature, and pressure ranges from 125 to 200°C and 225 to 780 kPa. SO₂ was obtained as an undesirable by-product during H₂S oxidation reaction or as a product during regeneration of the catalyst. The feed gas contained 0.9 — 1.3 mol% H₂S with approximately 80 mol% CH_4. In this paper, the factors affecting the H₂S conversion and SO₂ formation are presented. The rate expressions for (a) H₂S conversion and (b) SO₂ formation were developed from the Langmuir-Hinshelwood surface control reaction model. The experimental data were well correlated by the rate equations. Also, the rate parameters were evaluated and correlated with temperature. The activation energies for H₂S oxidation and SO₂ production reactions were calculated to be 34.2 and 62.5 kJ/mol, respectively. Partial pressures of oxygen and H₂S were found to influence H₂S conversion whereas, the presence of water in the feed gas up to 10.5 mol% did not affect H₂S conversion significantly. Heats of adsorption for various species on the active sites were calculated. SO₂ production was, as expected, enhanced at higher temperature, and its rate was much smaller than the oxidation rate of H₂S under the reaction conditions used.     

活性炭负载催化剂臭氧催化氧化处理印染废水研究

以堇青石蜂窝陶瓷、硅藻土、活性氧化铝和活性炭作为载体、金属氧化物(FexOy、CuO、NiO、MnxOy、BaO)作为催化活性组分,对臭氧催化氧化印染废水进行了试验对比,并对影响载铁型活性炭催化剂臭氧催化氧化印染废水的因素进行了研究。结果表明,载铁型的催化剂活性相对较高,当焙烧温度为750℃时,催化性能最好。利用载铁型活性炭催化剂,在臭氧质量浓度为10mg/L、pH值为6、反应时间为60min的条件下,催化氧化具有最佳的效果,COD去除率达86%;催化剂的重复利用性好,连续使用12次,COD的去除率仍可达64%。     

棉杆活性炭负载Co-B催化剂催化硼氢化钠水解制氢的性能

采用棉杆生物质废弃物为原料、H₃PO₄为活化剂, 在流化床中化学活化制备棉杆活性炭, 并将其作为载体负载Co-B组分, 制备了棉杆活性炭基Co-B催化剂(Co-B/C)。以该催化剂应用于硼氢化钠水解制氢, 系统考察了活性炭活化条件(活化温度、活化时间、活化剂用量m_H3PO4/m_CS)、水解反应温度及催化剂循环使用次数对催化产氢性能的影响。同时, 使用N₂物理吸附、FTIR、XRD和SEM等技术对活性炭载体及催化剂进行了表征。结果表明:在活化温度500℃、活化时间1 h、m_H3PO4/m_CS为0.75条件下制得的活性炭载体, 负载14.5%Co的催化剂表现出最佳催化性能:反应温度为25℃时, 平均产氢速率可以达到12.06 L·min^-1·(g Co)^-1, 催化剂表现了较高活性。催化产氢反应的活化能为44.61 kJ·mol^-1。循环使用5次后, 催化剂仍保持初次活性的54%。     

Application of alumina supported gold-based catalysts in total oxidation of CO and light hydrocarbons mixture

Gold nanoparticles supported on alumina have been produced using the anionic exchange method and ammonia washing procedure. The catalysts are tested in the reaction of total oxidation of a mixture of light hydrocarbons and carbon monoxide in order to study the possibility of application in the reduction of cold start emissions. The obtained results are promising according to the temperature range observed for the oxidation of unsaturated hydrocarbons. The results obtained for acetylene confirms the difference of oxidation of this hydrocarbon over gold catalysts. An ageing procedure has been employed. This procedure does not affect the comportment of the catalysts versus hydrocarbon oxidation.     

The influence of sulfur dioxide on propane oxidation activity over supported platinum and palladium

Earlier studies have shown that sulfur dioxide and metal-support interaction can strongly influence propane oxidation over platinum. In particular, oxidation activity is enhanced when platinum is supported on sulfated -alumina or zirconia compared to -alumina. Therefore, it is of interest to compare the performance of palladium under the same experimental conditions. Four model catalysts were examined: Pt/-alumina, Pt/zirconia, Pd/-alumina and Pd/zirconia. The metal loading was kept at or below 0.05 wt% to emphasize changes in activity attributable to metal-support interaction. Reaction rates were measured with and without sulfur dioxide. Surface sulfation was analyzed by measuring acid strength and evaluating spectra obtained by Fourier-transform infrared spectroscopy. In contrast to platinum, sulfation does not promote propane oxidation on Pd/-alumina, and Pd/zirconia is less active than Pd/-alumina.     

Effect of carbon dioxide on the selectivities obtained during the partial oxidation of methane and ethane over Li+/MgO catalysts

AtT 650 °C carbon dioxide either formed during reaction or added to the system increases the selectivity for the desired hydrocarbon products during the oxidative coupling of methane and the oxidative dehydrogenation of ethane reaction over Li⁺/MgO catalysts. Similarly, CO₂ inhibits secondary reactions of CH₃-radicals with the surface of the Li⁺/MgO. The improved selectivities are attributed to the poisoning effect that CO₂ has on the secondary reactions of alkyl radicals with the surface.     

Hydrogen peroxide promoted wet air oxidation of phenol: influence of operating conditions and homogeneous metal catalysts

The promoted wet air oxidation of phenol has been investigated through the addition of hydrogen peroxide as a source of free radicals. The reaction has been shown to proceed in two stages, an initial fast reaction associated with hydrogen peroxide consumption and a second slower step that occurs at a rate comparable with conventional wet air oxidation. An increase in temperature has a positive effect on both stages, while oxygen partial pressure only influences the second slower stage. The influence of pH on phenol oxidation is shown to be significant with the highest efficiency achieved at very alkaline conditions when phenol is completely dissociated. The catalytic activity of homogeneous metal salts was investigated in both the presence and absence of hydrogen peroxide. The combined addition of hydrogen peroxide and a bivalent metal (ie copper, cobalt or manganese) is shown to enhance the rate of phenol removal. However, in the absence of hydrogen peroxide only copper exhibited catalytic activity. Finally, a reaction mechanism involving different radical species has been proposed. From the experimental results the apparent activation energy (96.9 ± 3.5 kJ mol⁻¹) and pre‐exponential factor (1.6 ± 0.2 10¹⁰ s⁻¹) were calculated for hydrogen peroxide decomposition into hydroxyl radicals. © 1999 Society of Chemical Industry     

过氧化氢氧化苯酚铜锰复合氧化物催化剂的制备

采用固相法制备了新型催化剂铜锰复合氧化物催化剂。利用高效液相色谱法对苯酚过氧化氢氧化反应产物进行分析,以苯酚转化率和苯二酚收率为评价指标,对催化剂进行了评价。结果表明,催化剂性能随铜与锰物质的量比、焙烧温度、焙烧时间和研磨时间等因素的增大呈先升高再降低的趋势,并与络合剂的还原性有关。确定最佳工艺条件为:室温下,按锰与铜物质的量比1:2将Cu_2(OH)_2CO_3、MnCO_3和适量H_2C_2O_4·2H_2O混匀,置于研钵匀速研磨10 min,马弗炉400℃焙烧2 h。最佳条件下,苯酚转化率为63.7%,苯二酚收率为59.1%。     

临界点干燥仪制备的Pt-P25的电催化析氢反应性能探究

在各种制氢工艺中,电解水是一种获得氢能源的重要途径,Pt是析氢反应(HER)中最理想的催化剂.由于Pt基材料的稀缺性和高成本限制了其大规模应用,因此迫切需要开发一种低含量、高效的铂催化剂.P25是一种晶格缺陷密度很高的混晶型TiO2,载流子浓度大,具有良好的催化效果.本文采用临界点干燥仪,以商业化混晶TiO2(P25)...     

二氧化氯催化氧化处理活性艳红染料废水催化剂的制备与应用

研究了二氧化氯催化氧化用催化剂的制备条件与催化剂性能。实验结果表明，在工业催化剂载体上负载Cu^2+活性组分的催化剂制备优化条件为：w(Cu²⁺)=6%，焙烧温度500 ℃，焙烧时间4 h。用此催化剂进行二氧化氯催化氧化处理COD为2 700 mg·L^-1的活性艳红染料配制废水时，COD去除率达75%；催化剂寿命与再生实验表明，该方法在技术与经济上都具有较强实用性。     

类水滑石负载的二氧化钛制备及对苯酚羟基化反应的活性

利用微波晶化法合成了四元类水滑石前体,以此为载体制备了负载TiO2的水滑石催化剂,考察了其对苯酚羟基化反应的活性,结果表明:负载TiO2类水滑石催化剂表现出了较好的羟化反应活性,研究了苯酚羟化的反应工艺条件对催化剂活性的影响,确定了适宜的羟基化反应条件为:温度为70℃、反应时间为60min、催化剂用量为0.53g、30%的H2O2用量为24mL、苯酚加入量为5.0g。在此条件下,苯酚的转化率为89%。