催化剂协同介质阻挡放电去除VOCs的研究概述

综述了近年来催化剂对介质阻挡放电提高VOCs去除率、减少副产物产量的研究进展,讨论了不同类型催化剂与水蒸气对介质阻挡放电过程的影响及反应机理,分析了反应器中常见副产物的分解机理,展望了未来相关催化剂的发展前景。指出改性催化剂在不同反应条件下与不同介质阻挡反应器的结合有助于进一步研究。     

介质阻挡放电脱硫脱硝过程特性

氮氧化物和硫氧化物在介质阻挡放电(DBD)反应器中的脱除率与很多因素有关,如氧气含量、相对湿度和烟气中SO_2的初始浓度等。本文通过改变SO_2初始浓度、氧气含量和相对湿度来研究脱除氮氧化物和硫氧化物过程中的反应机理。结果发现,在N_2/SO_2/NO体系中SO_2初始浓度在较大范围内变化对NO和SO_2的脱除率影响很小;而N_2/NO/SO_2/H_2O体系中相对湿度的增加对SO_2的脱除的影响较NO的影响大,增加烟气中相对湿度能明显减少SO_2在烟气中的浓度;N_2/NO/SO_2/O_2体系中氧气的增加对SO_2的脱除效率影响不明显,但能促进NO氧化成NO_2或者其他的氮氧化物,同时,在一定的条件下,也能加速NO的生成。探讨NO和SO_2的反应机理,发现SO_2的反应主要与OH和水合电子有关,而NO的反应与O、N等活性基相关。     

介质阻挡放电技术再生Pd/AC催化剂的机理探讨

利用介质阻挡放电对失活钯炭催化剂(Pd/AC)进行再生,并通过催化臭氧氧化硝基苯反应评价再生后催化剂的活性。运用扫描电镜(SEM)、比表面积测定(BET)、热重分析(TG)等测定手段对Pd/AC进行表征;并对放电过程进行臭氧产量测定和等离子体发射光谱诊断,分析了Pd/AC催化剂再生的机理。结果表明,催化剂经放电处理30 min后再生率为95%;利用在最优条件下再生的Pd/AC进行催化臭氧氧化反应,硝基苯的降解率为87%;再生过程中臭氧贡献率仅为25.6%,表明放电过程中产生的强氧化性自由基是促使催化剂再生的主要因素。     

活性炭吸附协同介质阻挡放电降解甲硫醚

采用活性炭协同介质阻挡放电技术对恶臭物甲硫醚去除进行了研究.结果表明,甲硫醚去除率随着能量密度的提高而上升.在相同能量密度下,等离子体反应器中引入活性炭可以显著提高去除率.当能量密度大于288 J·L-1时,甲硫醚去除率＞98%.甲硫醚去除率随着初始浓度和气体流量的增大而降低.本实验中,湿度显著影响甲硫醚在活性炭协同等...     

介质阻挡放电技术处理挥发性有机物的研究进展

介质阻挡放电技术在处理低浓度挥发性有机物（VOCs）过程中具有反应快速、工艺简单及适应范围广等优点而受到广泛关注。本文从介质阻挡放电单独使用和介质阻挡放电协同催化两方面进行了概括总结。首先,简述了介质阻挡放电处理VOCs所用的驱动电源和等离子体发生器的研究现状及气体性质对VOCs降解性能的影响;其次,介绍了介质阻挡放电协同催化的两种方式（内置式和后置式）及各自情况下采用不同催化剂强化VOCs去除性能、提高能量效率、抑制副产物生成的过程机理;最后,分析了介质阻挡放电技术处理低浓度VOCs过程中存在的关键问题,并提出了未来的重要研究方向为：等离子体催化体系中VOCs的界面反应机理;催化剂的抗积碳性能的提高;适用于多组分VOCs的高效催化剂的开发。     

双介质阻挡放电降解苯酚废水研究

研究了双介质阻挡放电降解苯酚废水过程中不同因素对苯酚降解效果的影响,确定了最佳反应条件,并初步探讨其反应机理。采用自制双介质阻挡放电反应器,以模拟苯酚废水为研究对象,研究了苯酚废水浓度、输入电压、废水曝气量、反应时间等因素对苯酚降解效率的影响。结果表明:输入电压为5 k V,曝气气水比为40∶1,反应时间60 min,降解质量浓度为200 mg/L的模拟苯酚废水,苯酚最大去除率达到95.3%;其中苯酚废水浓度、输入电压、曝气气水比对试验结果影响较大。     

介质阻挡放电低温等离子体脱硫脱硝过程的研究

考察介质阻挡放电低温等离子体反应器两端电压、电源频率、烟气湿度、氧气含量等因素对NO和SO_2脱除率的影响。结果表明,随着反应器两端电压的增加,NO和SO_2的脱除率提高,在电压16 k V后,脱除率提高变缓;随着频率增加,NO和SO_2的脱除率先增加后减小,频率10 k Hz时,NO和SO_2脱除率达到最大;烟气相对湿度的增加,可以大幅提高SO_2的脱除率,氧气含量的增加,却导致NO的脱除率降低。     

低温SCR脱硝催化剂研究进展

氮氧化物NOx(NO, NO2和N2O)是全球大气污染的主要污染物之一,引起光化学烟雾、酸雨、臭氧层破坏等环境问题,严重影响人们的生存环境和生活质量,引起了世界各国的广泛关注。针对固定源和移动源燃烧排放,各国制定了日益严格的排放标准。目前主要的脱硝技术分为选择性催化还原(SCR)、选择性非催化还原(SNCR)、氧化脱硝和活性炭吸附脱硝等。SNCR的应用有较高的条件,影响其成功运行的主要因素有温度、氨氮比、氨气在烟气中的分布和停留时间等,故SNCR的工业应用存在一定的局限性。SCR脱硝技术比其它脱硝技术应用更广泛,其中脱硝多安排于除尘脱硫后,此时温度多处于100?250℃之间。为提高SCR脱硝性能,低温SCR脱除NOx是目前研究最热门的烟气脱硝技术。本工作综述了近年来低温SCR脱硝催化剂的研究进展,介绍了锰基催化剂、钒基催化剂及碳基催化剂的发展现状,对单组分Mn基催化剂、负载型Mn基催化剂和复合型Mn基催化剂进行了综述,从V基催化剂的制备对脱销的影响和脱硝机理进行了表述,综述了过渡金属掺杂对C基催化剂的影响,阐述了烟气中H2O和SO2对催化反应的影响及低温SCR反应的脱硝机理,对低温SCR催化剂进行了总结并对其未来发展进行了展望。     

电晕放电与介质阻挡放电净化氰化氢的机理

利用电晕放电以及介质阻挡放电两种低温等离子体产生方式净化氰化氢(HCN),同时对二者的反应机理进行探讨。结果表明,在电晕放电中当输入能量比(SIE)达到8.3 kJ/L,HCN净化效率为76%,在介质阻挡放电中当SIE为11.9 kJ/L时,HCN净化效率为94%;通过Gaussian软件利用密度泛函理论(DFT)引入外电场,计算分析了两种不同放电方式在HCN净化过程中的差异,在引入外电场之后HCN分子的分子结构以及体系能量均发生了变化,在不同的放电方式中,HCN转化的中间产物—OCN在电晕放电中主要转化为CO₂与N₂,而在介质阻挡放电中HCN更容易与体系中—OH结合生成H₂O与—CN,—CN会在介质阻挡放电中的高电子、粒子密度的作用下聚合为C₃N₄。     

高压脉冲介质阻挡放电协同臭氧溶气降解聚丙烯酰胺模拟废水

利用高压脉冲介质阻挡放电与臭氧联用的上流式反应器,考察了高压脉冲介质阻挡放电、臭氧和二者协同处理聚丙烯酰胺的降解情况以及COD和BOD5/COD的变化趋势;另外研究了反应器内加入TiO2催化剂对处理效果的影响,并探讨了其作用机理。结果表明,停留时间为10min时,放电协同臭氧溶气对聚丙烯酰胺的降解率可达51%,比单独放电和单独臭氧分别提高了27%和4%。加入TiO2催化剂后,COD去除率达到65%,BOD5/COD提高到0.37。     

Enhancement of VOCs removal using a novel double-tube packed bed catalytic dielectric barrier discharge (DPDBD) reactor

We developed a novel double-tube packed bed catalytic dielectric barrier discharge (DPDBD) reactor to degrade toluene. The DPDBD reactor contains four discharge cells with one power supply, namely, A–D. NiO/γ-Al₂O₃ is packed in cell A to effectively destroy the branched chains in toluene. TiO₂/γ-Al₂O₃ is packed in cell B owing to its high catalytic oxidation activity to weaken the benzene rings and mineralize the generated partial aromatic compounds. Cell C is a pure DBD process without any catalyst packed to thoroughly mineralize all the generated aromatic compounds and convert CO into CO₂ and NO into NO₂. γ-Al₂O₃ is packed in cell D to reduce the concentrations of byproducts, including O₃ and NO generated by air through oxidation. The combinations of the four discharge cells are optimized by the treatment of −3000 mg m⁻³ of toluene at 11 kV. In comparison with a double-tube dielectric barrier discharge (DDBD) reactor without catalyst packing and with a total discharge length of 6 cm, the selectivity of CO₂ was significantly improved from 45% to 57% when the discharge lengths of A, B, C, and D are 2, 4, 4, and 2 cm, respectively. Furthermore, the concentrations of O₃ and NO in the outlet can also be effectively reduced from 2.80 and 210 mg m⁻³ to 1.30 and 60 mg m⁻³, respectively. We also investigated the effects of applied voltage and styrene initial concentration.     

Hydrophobic coating of silicate phosphor powder using atmospheric pressure dielectric barrier discharge plasma

A stable superhydrophobic coating was successfully deposited on commercial silicate‐based orange phosphor by using atmospheric pressure dielectric barrier discharge plasma with hexamethyldisiloxane (HMDSO) and HMDSO/toluene mixture as precursors. Owning to the good optical properties, the deposited film acts not only as a hydrophobic protective layer but also as an antireflection optical thin film capable of improving the phosphor photoluminescence efficiency. The plasma‐polymerized film based on Si?O?Si backbone containing methyl and phenyl nonpolar functional groups exhibited high‐water‐repellent characteristics. It was found that the water contact angle gradually increased with increasing the aging time and remained unchanged at about 140° after 1‐month aging. Besides, the thermal stability of the coated phosphor under high‐temperature condition was substantially enhanced by the aging. The findings of this work can contribute to improving the durability and reliability of the phosphor, eventually the long‐term stability of phosphor‐based light emitting diodes in practical applications. © 2014 American Institute of Chemical Engineers AIChE J, 60: 829–838, 2014     

乙醇胺对介质阻挡耦合电晕放电同时脱除NO、SO2的影响

采用自行设计的介质阻挡耦合电晕放电等离子体反应装置进行了模拟烟气同时脱硫脱硝的研究,分别考察乙醇胺（HOCH₂CH₂NH₂,MEA）在不同模拟烟气体系中对NO、SO₂脱除的影响,深入探讨了MEA在放电过程中与NO的作用机理。结果表明：在N₂/O₂/SO₂/NO体系中,0.56% MEA的加入可以显著消除O₂对NO脱除的抑制作用;在N₂/CO₂/SO₂/NO体系中,MEA会吸收进入体系中的部分CO₂,以减弱CO₂对NO脱除的抑制;在N₂/O₂/CO₂/H₂O/NO/SO₂体系中,0.56% MEA的加入既可以有效减弱H₂O的影响,也可以使NO的脱除率达到71.28%,继续将MEA的体积分数增大至1.20%时,可将该体系下NO脱除率提高到81.25%;同时,MEA可以在短时间内高效吸收体系内的SO₂,且几乎不受其他气体成分的影响,SO₂脱除率保持在95%左右。     

Continuous flow removal of acid fuchsine by dielectric barrier discharge plasma water bed enhanced by activated carbon adsorption

Continuous processes which allow for large amount of wastewater to be treated to meet drainage standards while reducing treatment time and energy consumption are urgently needed. In this study, a dielectric barrier discharge plasma water bed system was designed and then coupled with granular activated carbon (GAC) adsorption to rapidly remove acid fuchsine (AF) with high efficiency. Effects of feeding gases, treatment time and initial concentration of AF on removal efficiency were investigated. Results showed that compared to the N2 and air plasmas treatments, O2 plasma processing was most effective for AF degradation due to the strong oxidation ability of generated activated species, especially the OH radicals. The addition of GAC significantly enhanced the removal efficiency of AF in aqueous solution and shorten the required time by 50%. The effect was attributed to the ability of porous carbon to trap and concentrate the dye, increasing the time dye molecules were exposed to the plasma discharge zone, and to enhance the production of OH radicals on/in GAC to boost the degradation of dyes by plasma as well as in situ regenerate the exhausted GAC. The study offers a new opportunity for continuous effective remediation of wastewater contaminated with organic dyes using plasma technologies.     

钠添加剂对介质阻挡-电晕放电耦合法尿素脱除NO的影响

利用自主设计的介质阻挡-电晕放电耦合装置进行脱除NO的实验研究,在N₂/O₂/NO体系中,考察加入不同钠添加剂（Na₂CO₃、NaOH、CH₃COONa）对尿素脱除NO的影响,同时探讨其在脱除NO过程中的作用机理。结果表明：在研究范围内,仅添加尿素时,NO脱除率随尿素含量的增加而增大,当输入电流为0.83A,尿素分解产生氨气的体积分数为0.3%时,NO脱除率为64.23%,此时体系中有CO生成且随尿素含量的增加而增加;少量钠添加剂的加入可显著提高NO脱除率,且脱除率随钠添加剂含量的增加而增大,此时CO生成量得到有效抑制。在加入量相同的条件下,各种钠添加剂对尿素脱除NO均有促进作用,促进作用大小依次为：NaOH > Na₂CO₃ > CH₃COONa,当加入氢氧化钠与尿素质量比为10∶10时,输入电流仅为0.83A时,脱除率可达90.71%;电流为5A,脱除率达95.71%,此时体系中几乎无CO生成。     

介质阻挡放电等离子体反应器降解盐酸四环素

采用介质阻挡放电等离子体反应器降解盐酸四环素（TC）,研究了输入功率、放电间距、气体流量、初始浓度等参数对盐酸四环素降解效果的影响,结果表明当输入功率为1.3 W,放电间距为2.5 mm,气体流量为150 ml·min^-1,初始浓度为100 mg·L^-1时降解效果最好,放电处理30 min盐酸四环素的降解率达到92%。动力学研究表明盐酸四环素的降解过程符合拟二级动力学方程。检测了降解过程中生成的中间产物,提出了盐酸四环素的降解路径与机理。