Dealuminated Y Zeolites for Destruction of Chlorinated Volatile Organic Compounds
Dealuminated Y Zeolites for Destruction of Chlorinated Volatile Organic Compounds
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DOI：
10.1006/jcat.2002.3591
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发表时间：
2002-07
影响因子：
7.3
通讯作者：
R. López-Fonseca;J. I. Gutiérrez-Ortiz;M. A. Gutiérrez-Ortiz;J. González-Velasco
中科院分区：
文献类型：
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作者：
R. López-Fonseca;J. I. Gutiérrez-Ortiz;M. A. Gutiérrez-Ortiz;J. González-Velasco
本文研究了（NH_4）_2SiF_6化学脱铝处理Y型分子筛对氯代烃燃烧的催化性能。因此，在200至550°C之间的干燥和潮湿（15，000 ppm的水）空气中的贫氯烃浓度（约1000 ppm）的条件下，在具有不同Si/Al比的两种Y沸石上评价二氯甲烷（DCM）、1，2-二氯乙烷（DCE）和三氯乙烯（TCE）的深度催化氧化。与未脱铝的催化剂相比，脱铝后的催化剂具有更高的CVOC氧化活性。活性的提高归因于催化剂脱铝过程中形成的强Bronsted酸中心。发现破坏的容易程度按以下顺序降低：DCE>DCM>TCE。形成的主要氧化产物是CO、CO2、HCl和Cl 2。此外，还检测到其他一些氯化副产物/中间体，即分别在DCE、DCM和TCE的氧化过程中产生的氯乙烯、氯甲烷和四氯乙烯。水的加入略微降低了沸石的活性，并显著改变了产物分布。因此，发现副产物的产生显著减少。水也在一定程度上促进了CO2的选择性，并通过Deacon反应导致氯完全反应为HCl。
Chemical dealumination by (NH4)2SiF6 treatment has been investigated as an effective method for improving the catalytic behaviour of Y zeolites for chlorinated hydrocarbon combustion. Hence, the deep catalytic oxidation of dichloromethane (DCM), 1,2-dichloroethane (DCE), and trichloroethylene (TCE) was evaluated over two Y zeolites with different Si/Al ratios, at conditions of lean chlorocarbon concentration (around 1000 ppm) in dry and humid (15,000 ppm of water) air between 200 and 550°C. Catalyst-subjected to dealumination exhibited a higher activity in CVOC oxidation compared with that of the untreated one. The activity increase was attributed to the strong Bronsted acidic sites formed during catalyst dealumination. The ease of destruction was found to decrease in the following order: DCE>DCM>TCE. The main oxidation products formed were CO, CO2, HCl, and Cl2. In addition, some other chlorinated by-products/intermediates were detected, namely vinyl chloride, methyl chloride, and tetrachloroethylene in the oxidation of DCE, DCM, and TCE, respectively. The addition of water slightly diminished the zeolite activity and markedly changed the product distribution. Hence, by-product generation was found to be significantly reduced. Water also promoted somewhat the CO2 selectivity and led to complete reaction of chlorine to HCl by the Deacon reaction.