The activity and mechanism of uranium oxide catalysts for the oxidative destruction of volatile organic compounds

Uranium oxide based catalysts have been investigated for the oxidative destruction of volatile organic compounds (VOCs) to carbon oxides and water. The catalysts have been tested for the destruction of a range of organic compounds at space velocities up to 70 000 h⁻¹. Destruction efficiencies greater than 99% can be achieved over the appropriate uranium based catalyst in the temperature range 300–450°C. Volatile organic compounds investigated include benzene, butylacetate, cyclohexanone, toluene, methanol, acetylene, butane, chlorobutane and chlorobenzene. The catalysts are thermally stable, destroy low concentrations and mixtures of VOCs and lifetime studies indicate that deactivation during oxidation of chlorinated VOCs did not occur. A temporal analysis of products (TAPs) reactor is used to investigate the mechanism of oxidation of VOCs by uranium oxide catalysts. Studies indicated that VOCs were oxidised directly to carbon oxides on the catalyst surface. A combination of TAP pulse experiments with oxygen present and absent in the gas phase has indicated that the lattice oxygen from the catalyst is responsible for the total oxidation activity. This has been confirmed by studies using isotopically labelled oxygen which indicates that the catalyst operates by a redox mechanism.     

家具厂挥发性有机物气体催化燃烧处理方案探讨

目前,在诸多行业生产中会产生大量的VOC废气,该气体严重造成了空气污染。通过催化燃烧技术对其进行处理,使其在催化剂的作用下在300℃左右燃烧氧化分解成CO2和H2O。燃烧过程产生的热能可用热交换器回收利用,达到废气利用和节能的目的。从测试数据来看,95%的VOC废气被去除,可知该方法的可行性。     

The effect of the nature of vanadium species on benzene total oxidation

The nature of the vanadium species present on V₂O₅/Al₂O₃ catalysts was investigated by using solid state ⁵¹V NMR, diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD) and temperature programmed reduction (TPR). ⁵¹V NMR and DRS analyses indicated the presence of V⁵⁺ in tetrahedral symmetry at low vanadium loading. A surface polymeric vanadium species and/or the bulk crystalline V₂O₅ were mainly observed at high vanadium loading as also detected by XRD. The positions of the absorption edges determined through the UV–VIS spectra allowed distinguishing between various tetrahedral symmetries. After TPR, the average oxidation state of vanadium depended on the vanadium content. The nature of vanadium species was related to the catalyst behavior on the benzene oxidation reaction. The catalysts containing high vanadium content were more active suggesting that a high amount of V⁴⁺ is responsible for the higher activity.     

The role of carbon deposition on precious metal catalyst activity during dry reforming of biogas

Gold and palladium were supported on a mesoporous TiO₂ for total oxidation of volatile organic compounds (VOCs). Mesoporous high surface area titania support was synthesised using of Ti(OC₂H₅)₂ in the presence of CTMABr surfactant. After removing the surfactant molecules, 0.5 or 1.5 wt% of palladium and 1 wt% of gold were precipitated on the support by, respectively, wet impregnation and deposition–precipitation methods. The activity for toluene and propene total oxidation of the prereduced samples follows the same order: 0.5%Pd-1%Au/TiO₂ > 1.5%Pd/TiO₂ > 0.5%Pd/TiO₂ > 1%Au-0.5%Pd/TiO₂ > 1%Au/TiO₂ > TiO₂. Moreover, a catalytic comparison with samples based on a conventional TiO₂, shows the catalytic advantage of the mesoporous TiO₂ support. The promotional effect of gold added to palladium could be partly explained by small metallic particles (TEM), but meanly by metallic particles made up of Au-rich core with a Pd-rich shell. Moreover, the hydrogen TPR profile of 0.5%Pd-1%Au/TiO₂ shows only the signal attributed to small PdO particles. Gold also implies a protecting effect of the support under reduction atmosphere. Operando diffuse reflectance infrared fourier transform (DRIFT) spectroscopy was carried on and allowed to follow the VOCs oxidation and the formation of coke molecules, but also a metallic electrodonor effect to the adsorbed molecule which increases in the same order as the activity for oxidation reaction. The presence of coke after test was also shown by DTA–TGA by exothermic signals between 300 and 500 °C and by EPR (g = 2.003).     

Effect of temperature on the performance of a biofilter inoculated withPseudomonas putida to treat waste-air containing ethanol

The microbes ofPseudomonas putida (KCTC1768) were fixed on the biofilter-packing media comprising an equivolume mixture of granular activated carbon (GAC) and compost, by recycling the liquid medium containing incubatedPseudomonas putida (KCTC1768). A biofilter experiment was performed to observe its transient behavior under the operating condition of 2,180 ppmv of ethanol-inlet concentration and 158 g/m³/h of ethanol-inlet load for the five consecutive temperature-stages of operation ranging from 25 °C to 40 °C. For the five temperaturestages of operation their removal efficiencies were measured and were compared with each other. The optimum operating temperature of the biofilter turned out to beca. 30 °C, which was consistent with the previous experimental result of Lim and Park. However, the optimum incubation-temperatures ofPseudomonas putida (KCTC1768) and the equivalent (i.e., NCIMB8858) were announced to be of 26 °C and 25 °C by Korea Collection for Type Cultures (KCTC) and National Collections of Industrial, Food and Marine Bacteria (NCIMB), respectively. It was also confirmed by the experiment in which the microbes were incubated in the same liquid medium as in the previous work of Lim and Park at temperature ranging from 20 °C to 40 °C and their growth rates were subsequently measured. Thus, the optimum operating temperature of a biofilter inoculated withPseudomonas putida (KCTC 1768) was proved to be 30 °C, which was higher than its optimum incubation-temperature byca. 5 °C     

The Influence of Area-Specific Ventilation Rate on the Emissions from Construction Products

Abstract Experiments were performed using small-scale climate chambers, including the new Chamber for Laboratory Investigations of Materials Pollution and Air Quality (CLIMPAQ), to gain knowledge about the influence of ventilation rate per plane specimen area (specific ventilation rate) on emission rates. Emissions from pieces of linoleum, waterborne acrylic paint, nylon carpet, and sealant were quantified at different specific ventilation rates. A trained sensory panel used the decipol scale and chemical analysis quantified some major Volatile Organic Compounds (VOCs) after the specimens had been conditioned in the chambers for six days. The results showed that the specific ventilation rate (L/s m2) may influence the emission rates. In both sensory and chemical terms, emission rates increased when ventilation was increased. At low specific ventilation rates the emission rate was proportional to the specific ventilation rate. For higher ventilation rates the emission rates stabilized and became independent of ventilation. The chemical measurements showed that only the emissions from the tested paint were influenced by ventilation rates above those comparable to 0.5 h^?1 in a typical room. The emissions quantified by the sensory panel continued, however, to be influenced by ventilation even at rates higher than 5 h^-1.     

装饰材料中VOC的散发规律及其影响因素

本文简要分析了装饰材料中VOC的散发机理，包括VOC在材料内部的扩散和从材料表面到周围空气的散发，在此基础上根据VOC散发的双指数模型和环境试验舱实验揭示了VOC随时阃衰减的规律，给出了影响装饰材料中VOC散发的因素，这些因素包括温度、相对湿度、空气流速、氧化剂和材料的表面特性等，最后介绍了一些控制VOC的方法。     

水性涂料VOC含量测定中水分含量测量方法对比

归纳了水性涂料VOC含量的限量值,讨论了水性涂料VOC含量的测定方法,对VOC含量测定中测水分含量的两种测定方法——卡尔·费休法和气相色谱法的精密度和准确度进行了考察。试验表明,卡尔·费休法的精密度和准确度不及后者。     

节能减排与涂料产品

分析了涂料行业产生温室气体排放的原因。介绍了我国现有低VOC涂料产品的优缺点。提出开发高性能节能涂料,为节能减排作贡献。     

Aromatic volatile organic compounds absorption with phenyl-based deep eutectic solvents: A molecular thermodynamics and dynamics study

The suitability of phenyl-based deep eutectic solvents (DESs) as absorbents for toluene absorption was investigated by means of thermodynamic modeling and molecular dynamics (MD). The thermodynamic models perturbed-chain statistical associating fluid theory (PC-SAFT) and conductor-like screening model for real solvents (COSMO-RS) were used to predict the vapor–liquid equilibrium of DES–toluene systems. PC-SAFT yielded quantitative results even without using any binary fitting parameters. Among the five DESs studied in this work, [TEBAC][PhOH] consisting of triethyl benzyl ammonium chloride (TEBAC) and phenol (PhOH), was considered as the most suitable absorbent. Systems with [TEBAC][PhOH] had lowest equilibrium pressures of the considered DES–toluene mixtures, the best thermodynamic characteristics (i.e., Henry's law constant, excess enthalpy, Gibbs free energy of solvation of toluene), and the highest self-diffusion coefficient of toluene. The molecular-level mechanism was explored by MD simulations, indicating that [TEBAC][PhOH] has the strongest interaction of DES–toluene compared to the other DESs under study. This work provides guidance to rationally design novel DESs for efficient aromatic volatile organic compounds absorption.