作为空气污染物的主要成分之一，挥发性有机化合物(VOCs)会极大地破坏生态环境并损害人体健康。在众多消除 VOCs的方法中，吸附法由于操作简单、成本低廉的优势而在工业上得以广泛应用。催化燃烧法则因去除效率高，适用范围广且无二次污染等优点被认为是 VOCs消除最有效的手段之一。
目前，活性炭是最常用的 VOCs吸附剂，但存在再生困难、抗湿性差、易燃等诸多问题。与活性炭等常规吸附剂相比，沸石分子筛作为 VOCs吸附剂其主要优势在于：(1)沸石分子筛的疏水性可调，通过调控分子筛骨架的硅铝比可以调节分子筛的亲疏水性，高硅铝比的沸石分子筛有着优异的疏水性能，从而可以有效降低在一定湿度条件下水对 VOCs分子的竞争吸附；(2)均一的孔径分布可以有效地进行分子识别，从而使吸附剂对VOCs的选择性吸附性大大提高；(3)沸石分子筛一般由硅铝构成，本身不可燃且水热稳定性好，因此能够与微波加热等其他手段相结合以降低吸附剂重生能耗，提高操作安全性；(4)沸石分子筛比表面积大，吸附容量高，是作为蜂窝转轮吸附技术中吸附剂的理想材料，而该技术是目前工业大规模消除VOCs的研究热点。因此，沸石分子筛由于其独特的性质，被视为一种简单高效、选择性好的VOCs吸附剂。现阶段，催化燃烧VOCs所使用的催化剂常用金属氧化物作为载体，但是金属氧化物比表面积相对较小且孔道结构不均一，因此严重影响了催化剂对VOCs的催化燃烧效率，限制了催化燃烧活性的提高。而与金属氧化物载体相比，沸石分子筛材料具有均一的孔道结构以及相对较大的比表面积等优点，而将具有较好吸附选择性和吸附容量的沸石分子筛作为载体，负载活性组分后可以实现催化剂催化燃烧性能的显著提高，从而成为VOCs催化燃烧的理想催化剂。
本文综述了目前沸石分子筛材料作为吸附剂和催化剂载体的负载型催化剂消除各类VOCs的研究进展。对于沸石分子筛作为VOCs吸附剂，我们小结了影响其吸附容量和吸附选择性的因素，发现分子筛的孔道大小和阳离子类型与VOCs的吸附情况密切相关。在此基础上，进一步简单介绍了分子筛蜂窝吸附转轮技术的研究现状。对于沸石分子筛作为催化剂载体，我们总结了其用于各类VOCs催化燃烧的研究情况，如烷烃类、芳烃类和醛类等。探究了催化性能的影响因素及相应的催化机理，发现分子筛的孔道结构、阳离子类型、硅铝比等都会显著影响沸石分子筛负载型催化剂的催化活性。最后，探讨了沸石分子筛应用于VOCs消除目前所存在的问题，同时展望了该领域未来的研究和发展方向。
Volatile organic compounds (VOCs) are a major component in air pollutants and pose great risks to both human health and environmental protection. Currently, VOC abatement in industrial applica‐tions is through the use of activated carbons as adsorbents and oxide‐supported metals as catalysts. Notably, activated carbons easily adsorb water, which strongly hinders the adsorption of VOCs;conventional oxides typically possess relatively low surface areas and random pores, which effec‐tively influence the catalytic conversion of VOCs. Zeolites, in contrast with activated carbons and oxides, can be designed to have very uniform and controllable micropores, in addition to tailored wettability properties, which can favor the selective adsorption of VOCs. In particular, zeolites with selective adsorptive properties when combined with catalytically active metals result in zeo‐lite‐supported metals exhibiting significantly improved performance in the catalytic combustion of VOCs compared with conventional oxide‐supported catalysts. In this review, recent developments on VOC abatement by adsorptive and catalytic techniques over zeolite‐based materials have been briefly summarized.
参考文献
| [1] | A.-F. Cosseron;T.J. Daou;L Tzanis.Adsorption of volatile organic compounds in pure silica CHA, *BEA, MFI and STT-type zeolites[J].Microporous and mesoporous materials: The offical journal of the International Zeolite Association,2013:147-154. |
| [2] | R. Beauchet;P. Magnoux;J. Mijoin.Catalytic oxidation of volatile organic compounds (VOCs) mixture (isopropanol/o-xylene) on zeolite catalysts[J].Catalysis Today,20073/4(3/4):118-123. |
| [3] | W.B. Li;J.X. Wang;H. Gong.Catalytic combustion of VOCs on non-noble metal catalysts[J].Catalysis Today,20091/2(1/2):81-87. |
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%