本科毕业翻译低温催化氧化相关.docx

1、本科毕业翻译低温催化氧化相关Low-temperature catalytic oxidation of aldehyde mixtures using wood fly ash: Kinetics动力学, mechanism, and effect of ozone使用木飞灰对乙醛混合物进行低温催化氧化：动力学、反应机理和臭氧影响的研究作者：Praveen Kolar a , James R. Kastner bA. Biological and Agricultural Engineering, Box 7625, Weaver Labs, North Carolina State Uni

2、versity, Raleigh NC 27695-7625, United StatesA. 美国北卡罗来纳州州立大学罗利NC27695-7625号，威乌尔实验室，生物和农业工程7625信箱B. Air Pollution Engineering Laboratory, 505 Driftmier Engineering Center, Biological and Agricultural Engineering, The University of Georgia, Athens, GA 30602, United StatesB. 美国乔治亚大学雅典GA30602号，生物与农业工程50

3、5 Driftmier 工程中心，空气污染工程实验室AbstractPoultry家禽 rendering致使 emissions contain volatile挥发性的 organic compounds (VOCs) that are nuisance讨厌的东西，损害, odorous难闻的, and smog and particulate matter precursors先驱，前导. Present treatment options, such as wet scrubbers使净化, do not eliminate a significant fraction of the

4、VOCs emitted including, 2-methylbutanal 甲基丁醛(2-MB), 3-methylbutanal异缬草醛, and hexanal正己醛. This research investigated the low-temperature (25160) catalytic oxidation of 2-MB and hexanal vapors in a differential微分的，差别的，特异的, plug 插入flow reactor流动反应器 using wood fly ash (WFA) as a catalyst and oxygen and

5、ozone as oxidants. The oxidation rates of 2-MB and hexanal ranged between 3.0 and 3.5 10-9mol g-1s-1 at 25and the activation energies were 2.2 and 1.9 kcal mol-1, respectively.The catalytic activity of WFA was comparable to other commercially available metal and metal oxide catalysts. We theorize th

6、at WFA catalyzed a free radical reaction in which 2-butanone丁酮 and CO2 were formed as end products of 2-MB oxidation, while CO2 , pentanal正戊醛, and butanal正丁醛 were formed as end products of hexanal oxidation. When tested as a binary二元的 mixture at 25 and 160, no inhibition抑制 was observed. Additionally

7、, when ozone was tested as an oxidant at 160, 100% removal was achieved within a 2-s reaction time. These results may be used to design catalytic oxidation processes for VOC removal at poultry rendering facilities设施，设备 and potentially可能地、潜在地 replace energy and water intensive 加强的，集中的air pollution tr

8、eatment technologies currently in use.摘要家禽排泄物是对人有损害的、难闻的物质，它是烟雾和细小颗粒物的前身，包含挥发性有机化合物（VOC）。当前的处理方式，比如湿净化法，不能有效消除排放的VOC中一些重要的部分，包括甲基丁醛、异缬草醛和正己醛。本实验研究了在特异的流动反应器中甲基丁醛和正己醛蒸汽的低温（25160）催化氧化。其中使用木飞灰做为催化剂，氧气和臭氧做为氧化剂。25时甲基丁醛和正己醛的氧化率范围为3.0和 3.5 10-9mol g-1s-1，二者的活化能分别为2.2和1.9 kcal mol-1。木飞灰（WFA）的催化活性不亚于其他商业可获得的

9、金属和金属氧化物催化剂。我们推理WFA催化了一个自由基反应，在此反应中，丁酮和CO2做为甲基丁醛氧化的终产物得以形成，而CO2、正戊醛和正丁醛做为正己醛氧化的终产物得以形成。当在25和160进行二元混合物测试时未发现抑制作用。此外，当在160下以臭氧做为氧化剂进行测试时，在2秒的反应时间内实验就达到了100%的去除率。这些结果可用来设计家禽设施中VOC去除的催化氧化过程，并有可能代替现在使用的能量和水消耗多的空气污染处理技术。1. Introduction1.引言 Many industrial operations generate aldehydes 乙醛as air pollutants

10、 (Baumann et al., 2000; Fullana et al., 2004). For example, 3-methylbutanal (3-MB), 2-methylbutanal (2-MB), and hexanal are generated in poultry rendering operations when animal by-products are processed (Kastner and Das, 2002). The aldehydes are odorous (Brewer et al., 1999), and contribute to atmo

11、spheric ozone and particulate matter formation. Typically, chemical wet scrubbers are used to treat aldehydes and other volatile organic compounds (VOCs) by oxidizing them with chemical oxidants, such as ClO2 and/or O3 (Kastner and Das, 2005 ). However, on-site analysis of the wet scrubbers indicate

12、d low removal efficiencies when treating aldehydes (typically 50%), due to lack of reactivity between the aldehydes and ClO2 (Kastner et al., 2003 ). 许多工厂产生空气污染物乙醛。例如，在动物副产物处理过程中家禽设施中会产生异缬草醛、甲基丁醛和正己醛。乙醛很难闻，并且会导致大气臭氧和细小颗粒物的形成。特别地，化学湿净化法被用来处理乙醛和其他挥发性有机化合物，用诸如ClO2和/或O3做为化学氧化剂来氧化这些成分。但是，现场的湿净化法分析在处理乙醛时显

13、示了较低的去除率（通常小于50%），这是因为乙醛和ClO2之间缺乏相互作用。Traditional treatment technologies such as adsorption吸附, incineration焚烧，烧灼灭菌, and biological filtration筛选 have limitations (Tsou et al., 2003 ).Adsorption only transfers and concentrates the VOCs from a gas phase onto a solid phase and needs further treatment fo

14、r complete removal ( Everaert and Baeyens, 2004). Incineration requires combustion of the VOCs at high temperatures (10001200_C) using natural gas as a fuel source, is costly and contributes to greenhouse gas production (Gervasini and Ragaini, 2000 ). Biological filtration systems need long residenc

15、e times (3060 s) and thus have large footprints. Hence, an effective alternative technology is needed to treat the aldehyde fraction from rendering emissions.传统的处理技术，例如吸附、焚烧和生物过滤都有局限性。吸附只是将VOC从气相中转移和浓缩到了固相上，要想完全除去需要进一步的处理。焚烧需要在很高的温度下（1000-1200）使用天然气做为燃料对VOC进行燃烧，这种方法成本高并且会产生温室气体。生物过滤系统需要很长的停留时间（30-60

16、秒），因此会有大量的印记。所以，需要研究一种有效的可替换的技术来处理排放物中的乙醛。Catalytic oxidation is a promising alternative technology to treat VOCs (Gervasini and Ragaini, 2000). The process involves reaction between VOCs and an oxidant, aided by a catalyst. Catalysts lower oxidation temperatures by providing alternate routes to end

17、 products, whose activation energies are less than that of non-catalytic reactions and typically increase reaction rates. Lowering the reaction temperature lowers treatment costs and reduces the production of greenhouse gases. Expensive metals (e.g., gold,platinum) and metal oxides (e.g., nickel oxi

18、de, ruthenium, etc.) have been tested as catalysts with a high degree of success. However, research has been limited on the development of catalysts from inexpensive materials, especially solid wastes.催化氧化技术是一种很有前景的可用来替换的处理VOC的技术。处理过程为在催化剂辅助的条件下VOC和氧化剂进行反应。催化剂通过提供比非催化剂过程所需活化能低的途径来使得氧化温度降低并能增加反应速率。降低

19、反应温度可以降低处理成本且减少温室气体的产生。将贵金属和金属氧化物做为催化剂的实验已经有很高的成功率。但是，有关从非贵金属材料，尤其是固体废弃物得到催化剂的实验还很有限。Many solid waste sources contain metals or metal oxides of sufficient surface area to be reused再生的，重复利用 as catalysts ( Klose et al., 2000).Wood fly ash (WFA), as an example, is produced in large amounts in the USA (

20、5.5 Mt y-1), with a majority land filled ( Demeyer et al.,2001). Analysis of WFA revealed crystalline透明的，水晶般的 phases of metal oxides (magnetite磁铁矿 and hematite赤铁矿) and activated carbon in its structure.WFA catalytically催化地 oxidizes H2S using O2, and oxidizes volatile organic sulfur compounds and pro

21、panal正丙醛, in the presence of ozone (Kastner et al., 2005, 2008 ). 很多固体废弃物含有表面积很大的金属或金属氧化物，可以重复利用做催化剂。例如WFA，在美国产量很大（5.5 Mt y-1），绝大多数地方都有。对WFA的分析显示了金属氧化物（磁铁矿和赤铁矿）的透明质地以及它的构造里的活性炭。在臭氧存在的条件下，用O2对H2S进行WFA催化氧化，对挥发性有机硫化合物和正丙醛进行氧化。Additionally, WFA catalytically oxidizes 3-MB at room temperature via a free

22、radical mechanism ( Kolar et al., 2007 ). However, a complete carbon balance on the reactions was not performed and it is unclear if complete oxidation occurred. Additionally, this work focused on single aldehyde乙醛 (3-MB) oxidation, when in reality, rendering emissions consist of aldehyde mixtures,

23、making it difficult to predict the catalytic performance based on a single compound.Hence, it is critical to evaluate WFA as a low-cost catalyst to treat aldehyde mixtures normally encountered in rendering emissions.The objectives of this study were to evaluate WFA as a low-cost catalyst for treatin

24、g a binary二元的 aldehyde mixture at low-temperatures (25160 _C), determine the kinetics动力学 of oxidation reactions and activation parameters参数, identify and quantify the oxidation products, perform a complete carbon balance, and determine the effect of ozone on the oxidation processes. 另外，在室温下WFA通过一个自由

25、基反应催化氧化异缬草醛。但是此反应并未显示完全的碳平衡，且尚不清楚是否进行了完全氧化。此外，本实验是基于单乙醛氧化的，而实际上排放物是由醛混合物组成的，这使得基于单组份的实验难以预测其催化效果。因此，评估WFA做为低成本催化剂来处理排放物中常见的醛类混合物是很重要的。本实验的目的就是对WFA做为一种低成本催化剂在低温条件下（25160）处理二元的醛混合物进行评估，确定氧化反应的动力学原理和活化参数，识别和量化氧化产物，形成完全的碳平衡，以及确定臭氧对氧化过程的影响。2. Experimental 2-MB and hexanal (95%, SigmaAldrich) were used as

26、 representative aldehydes醛类 in this study because of their consistent occurrence in poultry rendering emissions ( Kastner and Das, 2002).2. 实验 本实验使用甲基丁醛和正己醛（95%）做为代表性的醛类，因为它们在家禽排放物中是不断产生的。2.1. WFA characterization The WFA used in this study was obtained from a paper mill造纸厂. The physical and chemica

27、l properties性能 were determined previously (Ko-lar et al., 2007 ). In this study a scanning electron microscope (SEM) was used to image the WFA and energy dispersive分散的 spectroscopy (EDS能量色散谱，能谱分析仪) used to determine the elemental composition of the ash particle surface (see Supplemental material (SM

28、). SM 1.1).2.1 WFA的表征 本实验使用的WFA是从一个造纸厂获得的。其物理和化学性能已提前确定。本实验使用了扫描电镜（SEM）来形成WFA的图像，使用能谱分析仪（EDS）来确定飞灰颗粒表面的元素组成（看补充材料）。2.2. Description of experimental setup and analytical methods All gas/solid phase reactions were carried out in a 30-cm long,2.5-cm diameter (ID) continuous flow, differential packed-be

29、d reactor system, as described previously (Kastner et al., 2005and SM 1.21.3). A combination of gas chromatographs equipped with mass selective 质谱仪and flame ionization detectors 火焰离子化检测器were used for analysis on the reactants and end products.2.2 实验装置的描述及分析方法 如之前描述的一样，所有的气相/固相反应都是在一个长30cm直径2.5cm不断流动

30、的反应体系中进行的。使用气相色谱-质谱联用仪和火焰离子化检测器来分析反应物和终产物。2.3. General experimental procedures We determined the kinetics of individual aldehydes, kinetics of a binary mixture, the effect of temperature, and the effect of 1500 ppmv ozone on oxidation of 2-MB and hexanal. The total flowfor the entire study was betwe

31、en 2.0 and 5.0 L min-1 (GHSV = 0.00110.0055 h_1). For studies in which air was used as an oxidant, the ratio of oxygen to substrate基质，基片，酶作用物 ranged between 525:1 and 10 000:1. Similarly for experiments with ozone as an oxidant the ratio ranged between 3.75:1 and 5:1. Detailed experimental procedure

32、s are outlined in the SM 1.41.6.2.3 实验过程 我们进行了单组份醛的动力学研究、二元醛混合物的动力学研究、温度、1500ppmv臭氧对甲基丁醛和正己醛氧化的影响。整个实验总体流量在2.0到5.0L min-1之间。在以空气作为氧化剂的实验中，氧气与基质的比从525:1到10000:1不等。同样地，在以臭氧作为氧化剂的实验中，这种比例从3.75:1到5:1不等。详细的实验过程在补充材料1.4-1.6上。3. Results and discussion3.1. Effect of oxygen and evidence of catalytic activity Preliminary experiments were conducted to determine the effect of oxygen on catalytic oxidation of aldehydes. When ultra极端的 high pure helium氦气 (5 L min-1,25 _C) was used as the carrier gas (no oxygen present), fractional removal of 2-MB was limited to 2% which was probably due to sampl