Pilot VOC emissions mitigation by catalytic oxidation over commercial noble metal catalysts for cleaner production

Clean Technologies and Environmental Policy - Catalytic oxidation of volatile organic compounds (VOCs) is a widely used method for VOC emissions mitigation essential for the long-term...     

Different catalytic reactor technologies in selective oxidation of propane to acrylic acid and acrolein

One-step propane partial oxidation to acrylic acid and acrolein has been studied widely. Research on the catalyst systems has been accompanied by investigations of various reactor configurations in order to improve acrylic acid/acrolein yield for achieving industrial applications. Based on the reaction kinetics, lower gas-phase oxygen concentration supports the desired reaction path to the oxygenate products. Therefore, novel reactor concepts that can continuously provide uniform and controllable oxygen concentration have the potential for acrylic acid/acrolein yield enhancement. In this way, alternative reactor technologies from reactor structuring, fluidization to membrane type have been proposed. In this work, the actual state of these efforts is reviewed. The advantages and disadvantages of each concept are pointed out. However, the assessment of a new technology due to the numerous aspects that have to be considered is very difficult. It is suggested that circulating fluidized bed is a much preferred solution with respect to the acrylic acid/acrolein yield improvement.     

Control of spatiotemporal chaos in catalytic CO oxidation by laser-induced pacemakers

Control of spatiotemporal chaos is achieved in the catalytic oxidation of CO on Pt(110) by localized modification of the kinetic properties of the surface chemical reaction. In the experiment, a small temperature heterogeneity is created on the surface by a focused laser beam. This heterogeneity constitutes a pacemaker and starts to emit target waves. These waves slowly entrain the medium and suppress the spatiotemporal chaos that is present in the absence of control. We compare this experimental result with a numerical study of the Krischer-Eiswirth-Ertl model for CO oxidation on Pt(110). We confirm the experimental findings and identify regimes where complete and partial controls are possible.     

Chemisorptive catalytic oxidation process for SO2 from smelting waste gases by Fe(II)

Chemisorption of SO₂ from smelting plant exhaust gases in a single sieve plate column was investigated. Main parameters were SO₂ and O₂ gas and H₂SO₄, FeSO₄ and Al₂(SO₄)₃ liquid concentrations on reaction rate and equilibrium in FeII-EDTA solutions. Absence of inhibitors with this kind of flue gases promote fast kinetics. Optimal process conditions with 3% wt. FeSO₄ catalyst up to 2000 PPM SO₂. Maximum yield of 16% H₂SO₄ could be achieved considering optimal liquid/vapor ratio, oxygen surplus and insert salt concentrations.     

Tuning of catalytic CO oxidation by changing composition of Rh-Pt bimetallic nanoparticles

Recent breakthroughs in synthesis in nanoscience have achieved control of size and composition of nanoparticles that are relevant for catalyst design. Here, we show that the catalytic activity of CO oxidation by Rh/Pt bimetallic nanoparticles can be changed by varying the composition at a constant size (9+/-1 nm). Two-dimensional Rh/Pt bimetallic nanoparticle arrays were formed on a silicon surface via the Langmuir-Blodgett technique. Composition analysis with X-ray photoelectron spectroscopy agrees with the reaction stoichiometry of Rh/(Pt+Rh). CO oxidation rates that exhibit a 20-fold increase from pure Pt to pure Rh show a nonlinear increase with surface composition of the bimetallic nanoparticles that is consistent with the surface segregation of Pt. The results demonstrate the possibility of controlling catalytic activity in metal nanoparticle-oxide systems via tuning the composition of nanoparticles with potential applications for nanoscale design of industrial catalysts.     

NiO nanorings and their unexpected catalytic property for CO oxidation

Nickel oxide (NiO) nanorings were synthesized by controllable thermal decomposition of precursor Ni(OH)(2) nanoplates obtained via the reaction between Ni(NO(3))·6H(2)O and NaOH under hydrothermal conditions. The process of their formation was investigated and an unexpected catalytic property of this novel-shaped material is reported for CO oxidation.     

Decolorization of orange II by catalytic oxidation using iron (III) phthalocyanine-tetrasulfonic acid

Orange II, C.I. Acid Orange 7 (AO7), is oxidatively decolorized via catalytic oxidation by iron(III) phthalocyanine-tetrasulfonic acid (Fe(III)-PcTS) as a biomimetic catalyst and KHSO(5) as an oxygen donor. The nature of the decolorization of AO7 was investigated in the catalyst concentration range of 10-50 microM, in which the initial concentration of AO7 was 417 mg l(-1). A 99.6% decolorization was observed at [KHSO(5)] = 2.5 mM and [Fe(III)-PcTS] = 20 microM after a 3-h reaction period. However, the fact that only 4.9% of the TOC was removed indicated that the conversion to CO(2) was incomplete. The results of a total organic nitrogen analysis of the reaction mixture showed that the nitrogen in the azo chain was mainly converted to N(2) gas. In addition, 38.6% of the AO7 was converted to 1,2-dihydroxynaphthalene, and 21.4% to p-phenolsulfonic acid. These results indicate that the degradation via this catalytic system involves the conversion of AO7 to phenolic compounds, followed by N(2) production. In addition, a Microtox test showed that toxicity of the solution increased as a result of AO7 oxidation using this catalytic system.     

超低VOC涂料用纯丙乳胶制备及其共混研究

乳胶共混是指将不同玻璃化转变温度(Tg)的共聚物乳胶按照一定比例混合,已成为解决乳胶低温成膜和高力学性能之间矛盾的一项重要技术.采用半连续预乳化工艺合成了高Tg(约40℃)的P(MMA/BA/AA)乳胶和低Tg (约-40℃)的P(2-EHA/BMA/AA)乳胶;通过对不同比例的P(MMA/BA/AA)/P(2-EHA...     

Effect of temperature on the catalytic oxidation of CO over nano-sized iron oxide

Nanocrystallite iron oxide powders were prepared by co-precipitation method using highly purified FeCl₃ and NH₄OH solution. The prepared powders were tested for the catalytic oxidation of CO to CO₂. The effect of oxidation temperature on the catalytic reaction was isothermally investigated using advanced quadrpole mass gas analyzer system. The mechanism of the catalytic oxidation reaction was estimated from the experimental data. Fe₂O₃ nanocrystallite of 78 nm shows a good response towards catalytic CO oxidation at the temperature range 200–500 °C. The catalytic oxidation efficiency reached 98% at 400–500 °C. The reaction was found to be first order with respect to CO. The average activation energy of the reaction was found to be 26.3 kJ/mol which is smaller than the values reported in the literatures. The mechanism of CO catalytic oxidation was investigated by comparing the CO catalytic oxidation data in the absence and presence of oxygen. It was found that the catalytic oxidation of CO over Fe₂O₃ nanocrystallite proceeded by adsorption mechanism. Based on the experimental results, Fe₂O₃ nanocrystallite powders can be recommended as a promising catalyst for CO oxidation.     

A continuous flow reaction system for producing acetic acid by wet oxidation of biomass waste

A continuous flow reaction system designed for producing acetic acid by wet oxidation (WO) of biomass with the maximum treatment capacity of 1 kg/h of dry biomass was developed. Experimental runs with rice hulls and starch were conducted at reaction temperatures between 300–320°C, for time of 2 and 3 min, with oxygen supplies between 70 and 100%, and at pressures between 10 and 30 MPa. The influence of each of these parameters was evaluated.     

Thermal abatement of nitrogen-containing hydrocarbons by non-catalytic supercritical water oxidation (SCWO)

This work investigated the destruction of N-containing hydrocarbons namely DBU (1,8-diazobicyclo[5.4.0]undec-7-ene) and DMF (dimethyl formamide) by supercritical water oxidation (SCWO), using hydrogen peroxide as oxidant. Reactions were conducted under temperatures of (400–650 °C), pressures of (50–250 bars), oxidant stoichiometric ratio SR (0.9–12), initial concentrations of organics (0.1–8.4 mM) and residence time τ (6–17 s). Reactions took place in a plug flow continuous reactor and the results were presented in terms of the % removal (of TOC and the organic compound), C-fraction and N-fraction; all plotted as function of the above system conditions. Also, GC-MS analysis for DMF was conducted. Percent removal increased with temperature and complete organic- and >90% TOC removal, was obtained at 500 and 600 °C for DMF and DBU respectively. Conversion increased with the oxidant SR, residence time and initial organic concentration. Pressure affected conversion in the sub- and near-critical conditions but not in the supercritical region, yet an initial value of 150 bar was required to start the reaction. Pseudo first order-, integral power rate law-, and power law models successfully described the kinetic data; and the reaction constants for each model and energy of activation were evaluated.     

Characterization and catalytic performance of Co/SBA-15 supported gold catalysts for CO oxidation

Cobalt-containing SBA-15 supported gold catalysts for low-temperature CO oxidation were prepared and characterized by N₂ adsorption/desorption, X-ray diffraction, transmission electron microscopy, inductively coupled plasma-atom emission spectroscopy and X-ray photoelectron spectroscopy techniques. The effects of cobalt and gold content on the catalyst activity were investigated in detail. Among them, 2% Au/40% Co/SBA-15 shows the highest activity, its complete conversion temperature for CO is at 273 K. It was believed that both the dispersion of Co₃O₄ and the high surface areas caused by SBA-15 contribute to the good activities of cobalt-containing SBA-15 supported gold catalysts. Furthermore, the strong metal-support interaction between gold and cobalt oxides is greatly related to the catalytic performance.     

Sequential chemical treatment of radium species in TENORM waste sludge produced from oil and natural gas production

This paper is dedicated to the treatment of sludge occurring in frame of the Egyptian produced from oil and gas production. The activity levels of three radium isotopes: Ra-226 (of U-series), Ra-228 and Ra-224 (of Th-series) in the solid TENORM waste (sludge) were first evaluated and followed by a sequential treatment for all radium species (fractions) presented in TENORM. The sequential treatment was carried out based on two approaches 'A' and 'B' using different chemical solutions. The results obtained indicate that the activity levels of all radium isotopes (Ra-226, Ra-228 and Ra-224) of the environmental interest in the TENORM waste sludge were elevated with regard to exemption levels established by IAEA [International Atomic Energy Agency (IAEA), International basic safety standards for the protection against ionizing radiation and for the safety of radiation sources. GOV/2715/Vienna, 1994]. Each approach of the sequential treatment was performed through four steps using different chemical solutions to reduce the activity concentration of radium in a large extent. Most of the leached radium was found as an oxidizable Ra species. The actual removal % leached using approach B was relatively efficient compared to A. It is observed that the actual removal percentages (%) of Ra-226, Ra-228 and Ra-224 using approach A are 78+/-2.8, 64.8+/-4.1 and 76.4+/-5.2%, respectively. Whereas in approach A, the overall removal % of Ra-226, Ra-228 and Ra-228 was increased to approximately 91+/-3.5, 87+/-4.1 and 90+/-6.2%, respectively.     

Wet oxidation of lignin model compounds and acetic acid production

To investigate the wet oxidation (WO) pathways of acetic acid production from lignin, 2-methoxyphenol, 2,6-dimethoxyphenol, and phenol, as lignin model compounds were oxidized in a batch reactor at a temperature of 300°C, residence times of 10–60 seconds and oxygen supplies of 50–100%. Oxidation experiments using major intermediate products in WO of lignin model compounds, as reactants were also performed.Based on the intermediate products identified by GC/MS and HPLC, WO pathways of lignin model compounds are discussed. Acetic acid production by WO of lignin model compounds is also discussed. It was found that the yield of acetic acid for lignin model compounds was lower, at about 9%. The reason that lignin model compounds cannot produce a large amount of acetic acid may be contributed to the fact that the oxidation of phenols easily forms unsaturated dicarboxylic acids with 4 carbon atoms, which cannot produce a large amount of acetic acid. However, saturated dicarboxylic acids and glutaconic acid can produce a higher yield of acetic acid. Therefore, it is possible to increase the yield of acetic acid from lignin by controlling reaction pathways to increase the formation of saturated dicarboxylic acids and glutaconic acid.     

扩散渗析法回收湿法炼铜厂电解贫液中的硫酸

采用扩散渗析法回收福建某湿法炼铜厂电解贫液中的硫酸.电解贫液经"砂滤保安过滤扩散渗析"处理,回收酸返回"萃取电积"工段,残液送至堆浸循环使用.投产一年半来,已累计回收硫酸3 929.29t,充分回收利用资源,实现循环经济,创造明显的经济效益,解决了该厂电解贫液的开路难题.     

Effect of water addition on catalytic activity of nanosized gold catalysts for CO oxidation

The effect of water in the reactant gas on the catalytic activity for CO oxidation over Au/Co3O4 catalysts has been investigated. Water in the reactant gas had a negative effect on the catalytic activity for CO oxidation in Au/Co3O4 catalyst. Furthermore, it was observed that the average particle size of gold on Au/Co3O4 catalysts increased after stability testing both in dry and wet conditions.     

Electronic and catalytic studies on Co1 − xCuxMn2O4 for CO oxidation

Spinels of the composition Co_{1 – x} Cu _x Mn₂O₄ (x = 0.0, 0.3, 0.5, 0.7 & 1.0) have been prepared by co-precipitation technique. These were characterized by X-ray diffraction, infra-red spectroscopy, atomic absorption spectroscopy and BET method. The solid state studies such as electrical resistivity, magnetic susceptibility and electron spin resonance have been carried out and attempts have been made to correlate with the catalytic activity of the compounds. The intermediate compositions displayed better catalytic activity than the end compositions for carbon monoxide oxidation due to the phenomena of synergism. Behaviour of the activity pattern has been explained based on cation distribution in tetrahedral (A) and octahedral (B) sites. Crystallographic phase transition is observed from tetragonal to cubic at x > 0.5 by substitution of Cobalt with Copper.     

催化湿式氧化高浓度对氯苯基异氰酸酯生产废水催化剂的研究

以过渡金属氧化物CuO为主活性组分,通过对ZrO2的复合和掺入电子助剂CeO2的考察,研制出适用于催化湿式氧化处理高浓度对氯苯基异氰酸酯生产废水的复合催化荆.在固定床鼓泡式反应器连续反应装置上对废水进行处理,考察了各组分浸渍液浓度、焙烧温度、焙烧时间等制备条件对催化剂的催化活性的影响,确定了最佳制备条件.结果表明:优化制备的CuO-ZrO2-CeO2/TiO2催化荆,用于处理高浓度对氯苯基异氰酸酯生产废水时具有较好的催化活性,在反应温度T=240℃,反应压力P=6.5MPa,空速=2.0h-1,V(气):V(水)=230:1,进水pH=8条件下CODcr去除率达到96.9%,而在相同反应条件下未加催化剂的湿式氧化CODcr去除率只有40.8%.     

Nanostructure SnO2 and supported Au catalysts: Synthesis,characterization, and catalytic oxidation of CO

Nanostructure tin dioxide (SnO₂) powders prepared by sol-gel dialytic processes using tin (IV) chloride and anhydrous alcohol as start materials, ammonia gas as catalyst of the formation of colloid solution and agent of removing Cl⁻, and by introducing dialytic processes to improve and accelerate the formation of gels. From the result of TG–DTA analyses, the dried samples were calcined at 673 K in air for 3 h. Tin dioxide nanoparticles were characterized by thermogravimetry and differential thermal analyses (TG–DTA), X-ray diffraction (XRD), nitrogen adsorption–desorption, X-ray photoelectron spectroscopy (XPS). The average particle size of the as-prepared tin dioxide was about 5 nm. The as-prepared SnO₂ possessed mesoporous structure and large surface area. The Au/SnO₂ catalysts for low-temperature CO oxidation were prepared by the deposition–precipitation method using as-prepared SnO₂ powders as the support. The Au/SnO₂ catalysts exhibited high catalytic activity for low-temperature CO oxidation. The nanostructure SnO₂ has promising applications in sensor, catalyst, catalytic support, mesoporous membranes, etc.