室内挥发性有机化合物及其炭吸附净化

新型建筑装饰材料和日用化学品的大量使用,使得挥发性有机化合物(vOCs)不断释放到室内,由此导致室内空气品质(IAQ)下降.介绍了室内空气环境中VOCs的来源及其去除方法,并重点介绍了炭吸附净化法的研究进展.认为活性炭纤维吸附净化VOCs效率高,节能效果显著,是目前改善室内空气品质最有前景的技术之一.     

Adsorption of volatile organic compounds by means of activated carbon fibre-based monoliths

Activated carbon fibre monoliths (ACFMs) were prepared from the rejects of polymeric fibres (Nomex™). These were carbonised, agglomerated with a phenolic resin and steam activated at burnoff degrees between 0 and 40%. Adsorption experiments with n-butane at 30 °C show that, at high adsorbate concentrations, the amount adsorbed is a function of pore volume, but at low concentrations this mainly depends on pore size distribution. The porosity of Nomex-based ACFMs is formed by narrow micropores, which permit higher amounts of vapour to be adsorbed in low concentrations compared to monoliths prepared from different commercial activated fibres and a commercial granular activated carbon, which exhibits wider pores. The agglomeration of Nomex-fibres to form ACFMs does not cause any loss in adsorption properties with respect to non-agglomerated activated fibres. From the adsorption experiments of different vapours on a Nomex-based ACFM (40% burnoff) it was found that at high concentrations (p/p_o=1) the adsorbed volume was independent of the nature of the adsorbate and depended only on pore volume. However, at low vapor concentrations (p/p_o=0.004), the amount adsorbed depended on the adsorbate being well correlated to the molecular parachor and the polarizability of the adsorbates     

Adsorption and desorption of small molecule volatile organic compounds over carbide-derived carbon

Carbide-derived carbon (CDC) was prepared by selective extraction of titanium from titanium carbide in a flow of freshly prepared chlorine. The dynamic adsorption and desorption performance of CDC of small molecule volatile organic compounds (VOCs) including methanol, acetaldehyde and acetone, was investigated and compared with that of two types of commercial activated carbons. The physicochemical properties of carbons were characterized by nitrogen adsorption, temperature programmed desorption, Raman spectroscopy and transmission electron microscopy. It was observed that the CDC could adsorb much more VOCs than commercial activated carbons (especially for the less polar methanol). The desorption behavior of VOCs from the saturated CDC was similar to that of commercial activated carbons, with adsorbed VOCs desorbed in the maximum degree at 110–150 °C, which indicated that the adsorption sites for the VOCs on the three carbon adsorbents were similar and the saturated CDC could be effectively regenerated by simple heat treatment just like commercial activated carbons. Based on the characterizations, the large adsorption capacity of CDC was attributed to its larger micropore volume, narrower pore distributions (0.7–1.5 nm), as well as higher specific surface area than those of two commercial activated carbons.     

Thermocatalytic treatment of toxic organic compounds

Thermocatalytic treatment of toxic organic compounds is being introduced at OAO Zaporozhkoks. Industrial tests of a thermocatalytic reactor with activated silica-fiber packing prove satisfactory.     

Breakthrough data analysis of adsorption of volatile organic compounds on granular activated carbon

Volatile Organic Compounds (VOCs) such as methanol, ethanol, methyl ethyl keton, benzene, n-propanol, toluene, and o-xylene were adsorbed in a laboratory-scale packed-bed adsorber using granular activated carbon (GAC) at 101.3 kPa. The adsorber was operated batchwise to obtain the breakthrough curves of VOCs under the adsorption conditions such as adsorption temperatures (298–323 K), flow rates of nitrogen (60×10⁻⁶-150×10⁻⁶m³/min), GAC amount of 0.002 kg, and concentration of VOCs (3,000–6,000 ppmv). The adsorption kinetics was obtained by fitting the experimental breakthrough data to the deactivation model, combining the adsorption of VOCs and the deactivation of GAC. The adsorption isotherm, and adsorbed amount and adsorption heat of VOCs were obtained using the breakthrough curve: the former for comparison with the conventional isotherm models, the latter for correlation with the physical properties of VOCs.     

Adsorption of chlorinated volatile organic compounds in a fixed bed of activated carbon

Adsorption isotherms of dichloromethane and 1,1,2-trichloro-1,2,2-trifluoroethane on an activated carbon pellet, Norit B4, were studied. For these chemicals, the Sips equation gave the best fit for the single component adsorption isotherm. The adsorption affinity on activated carbon was greater for dichloromethane than that of 1,1,2-trichloro-1,2,2-trifluoroethane. An experimental and theoretical study was made for the adsorption of dichloromethane and 1,1,2-trichloro-1,2,2-trifluoroethane in a fixed bed. Experimental results were used to examine the effect of operation variables, such as feed concentration, flow rate and bed height. Intraparticle diffusion was able to be explained by a surface diffusion mechanism. An adsorption model based on the linear driving force approximation (LDFA) was found to be applicable to fit the experimental data.     

挥发性有机化合物催化氧化技术

基于环境友好,对使用催化氧化法去除挥发性有机化合物(VOCs)的原理、特点以及催化剂、工艺流程等研究进行综述。挥发性有机化合物完全催化氧化机理分为:Mars-van Krevelen(MVK)模型、Langmuir-Hinshelwood(L-H)模型和Eley-Rideal(E-R)模型。复合金属氧化物催化剂是研究的热点,去除VOCs的核心是使反应温度降低,即具有低温和高活性的催化剂。延长催化剂寿命、提高去除效率也可以带来良好的节能效果和降低投资成本。对于低浓度和大体积VOCs排放,可通过吸附+催化混合法先进技术实现去除,且成功应用于实践。     

挥发性有机化合物的净化处理技术

有机废气中大多含有低浓度的苯、甲苯、苯乙烯、多环芳烃等挥发性有机化合物（VOCs）。治理VOCs污染是大气污染治理的重要组成部分。叙述了吸收法、吸附法、生物法和低温等离子体4种废气净化技术的原理和国内外研究进展情况,并对其发展前景和研究方向进行了探讨。最后认为有机废气的联合协同处理方法是今后的一个重要研究方向。     

活性炭吸附法在挥发性有机物治理中的应用研究进展

挥发性有机化合物(VOCs)是一类重要的大气污染物,其所带来的环境污染问题已经引起全世界的关注.活性炭吸附法是治理VOCs污染的有效手段.本文从介绍VOCs治理技术出发,简述了活性炭吸附法在VOCs治理中的使用现状,概括了活性炭吸附法治理VOCs的工艺技术和存在问题,指出变温-变压吸附、变电吸附以其高效节能环保的优点,在VOCs治理中具有较好的发展前景.分析了活性炭表面化学性质、吸附质的物性、操作条件对活性炭吸附法治理VOCs的影响,为VOCs治理专用活性炭的改进和新产品的开发,提供了理论依据.在总结现有研究进展的基础上,预测了活性炭吸附法治理VOCs技术的发展趋势,提出对工艺的改进以及与其他VOCs废气处理技术的耦合使用,针对不同VOCs排放场所开发不同活性炭品种和VOCs回收装置将是以后研究的重要方向.     

基于流向变换技术处理工业有机废气的控制系统设计

综述了基于催化燃烧方法处理工业有机废气的控制系统的设计,指出该系统的控制对象为流向变换反应器,采用PLC控制系统完成控制功能。介绍了这种处理方法的理论依据,并提出控制系统的控制目标。以及对该处理过程的控制方法,以及控制系统的硬件构成和程序设计。最后以实例说明该处理方法及其控制策略的有效性。     

不同孔径活性炭吸附挥发性有机物的分子模拟

借助Materials Studio软件建立了0.902nm、1.997nm、3.000nm、4.000nm孔径的活性炭狭缝孔模型,采用巨正则蒙特卡洛模拟（Grand Canonical Monte Carlo）的模拟方法计算了其对挥发性有机物（VOCs,如异己烷、苯、甲苯、丙酮和甲醇）的吸附数据,考察了活性炭孔径的变化对VOCs吸附性能的影响,并对实际应用进行指导。模拟结果显示：活性炭对VOCs的吸附受孔径和吸附能的共同影响,在293.15K、各物质饱和蒸气压p₀下,随着孔径的增大,吸附质吸附剂之间的亲和力呈下降趋势。活性炭孔径由0.902nm增加到4.000nm对异己烷、苯、甲苯的饱和吸附量逐渐增大,而4.000nm孔径活性炭对丙酮饱和吸附量小于3.000nm孔径活性炭,3.000nm、4.000nm孔径活性炭对甲醇饱和吸附量小于1.997nm孔径活性炭。在工业废气VOCs吸附回收中选择0.902～1.997nm孔径活性炭能够达到最佳效果。     

Adsorption of multicomponent volatile organic compounds on semi-coke

Experimental and theoretical studies were made on the adsorption of toluene, ethyl acetate, benzene and their binary and ternary mixtures by semi-coke in an isothermal condition of 293 K. Breakthrough curves of these volatile organic compounds (VOCs) were measured by a gas chromatograph. The results showed that the adsorptive orders of these three VOCs were: toluene > ethyl acetate > benzene. The phenomenon of “roll-up” was observed in the breakthrough curves and under this condition, the more strongly adsorbed species displace the weaker ones. H₂O₂ was used to activate the semi-coke and the activation enhanced the adsorption capacity of semi-coke to all the three VOCs, especially to toluene. The extended Langmuir equation agrees well with the experimental isotherm data for binary and ternary mixtures and the error is below 5%.     

挥发性有机化合物催化消除前沿技术及研究进展

挥发性有机化合物(VOCs)是可吸入有害物质形成的重要前体,是大气污染物的重要组成部分。催化氧化法作为末端技术是目前处理VOCs最有效的途径之一。本文讨论了VOCs的热催化氧化、光催化氧化和光热协同催化氧化的研究进展,重点研究常用VOCs的催化氧化机理以及相关催化剂的构筑。其中,热催化燃烧主要以贵金属(Pt、Pd、Au、Ag等)、过渡金属(Mn、Co、Cr等氧化物)及复合型催化剂研究展开;光催化氧化以TiO₂和C₃N₄为典型催化剂进行讨论;光热协同催化研究主要包括碳基催化剂、贵金属负载型以及过渡金属负载型催化剂的开发与应用。此外,本文对基于催化剂的热催化、光催化和光热催化去除VOCs的开发和研究提出了进一步的展望。     

挥发性有机物回收模拟计算

针对低密度聚乙烯催化剂制备过程中会产生多组分有机尾气的问题,采用常压膜分离工艺,利用PRO/Ⅱ模拟软件对异戊烷、戊烷、四氢呋喃等有机溶剂进行了回收模拟计算。考察了冷凝温度、分离膜面积、溶剂渗透系数及分离膜渗透侧压力等工艺参数的影响。研究结果表明:冷凝温度不是决定溶剂净化度的主要指标,分离膜面积、溶剂在分离膜中的渗透系数、分离膜渗透侧压力均可显著影响净化气中VOCs的含量。对于一定的分离体系和分离净化目标,存在最优的膜面积和最低渗透系数要求。膜分离技术作为一种新兴的气体分离技术,未来可以较好地应用于高附加值有机物的回收领域。