Understanding the Dechlorination of Chlorinated Hydrocarbons in the Pyrolysis of Mixed Plastics
Understanding the Dechlorination of Chlorinated Hydrocarbons in the Pyrolysis of Mixed Plastics
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DOI：
10.1021/acssuschemeng.0c06461
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发表时间：
2021-01-15
影响因子：
8.4
通讯作者：
Leeke, Gary A.
中科院分区：
文献类型：
--
作者：
Jiang, Guozhan;Monsalve, D. A. Sanchez;Leeke, Gary A.
热解蒸气中含氯烃的脱氯作用知之甚少。为了揭示脱氯机理，采用异辛烷掺杂2-氯丁烷、2-氯丁烷和氯苯组成的模型混合物，研究了氯代烃的碱吸附脱氯反应。之所以选择这三种氯化烃，是因为它们通常可以由含有聚氯乙烯（PVC）的混合塑料废物的热解产生。将混合物连续泵送通过Na 2CO 3或CaCO 3/氧化铝床，并使用GC-MS鉴定脱氯产物并跟踪脱氯反应。当氯与具有相邻脂族氢的脂族碳键合时，氯化化合物首先经历脱氯化氢反应以形成HCl和烯烃，随后HCl与吸收剂中的碱反应。在我们的实验中，2-氯丁烷转化为2-丁烯，2-氯丁烷转化为苯乙烯。通过红外光谱和X射线衍射证实了盐酸的形成以及随后与吸收剂中碱组分的反应。在碱的存在下，脂族氯化烃在180 ℃的温度下进行脱氯。从芳香族氯化化合物中除去氯以不同的机理进行，其中通过氧化铝和烃介质的存在显著促进C-Cl键断裂。结果表明，氯苯发生脱氯反应，生成苯酚和苯。
The dechlorination of chlorine containing hydrocarbons in pyrolysis vapor is poorly understood. In order to shed new light on the dechlorination mechanism, a model mixture composed of iso-octane doped with 2-chlorobutane, 2-chloroethylbenzene, and chlorobenzene was used to study the dechlorination of chlorinated hydrocarbons by alkali adsorption. These three chlorinated hydrocarbons were selected as they can be typically produced from the pyrolysis of mixed plastic waste containing polyvinyl chloride (PVC). The mixture is pumped continuously through a Na2CO3 or CaCO3/alumina bed, and GC-MS is used to identify the dechlorination products and to follow the dechlorination reactions. When chlorine is bonded to an aliphatic carbon with an adjacent aliphatic hydrogen, the chlorinated compound first undergoes a dehydrochlorination reaction to form HCl and olefins, and subsequently the HCl is reacted with the alkali in the absorbents. In our experiments, 2-chlorobutane is converted to 2-butene, and 2-chloroethylbenzene is converted to styrene. The formation of HCl and subsequent reaction with alkali components in the absorbent is verified by IR spectroscopy and XRD. In the presence of an alkali, the aliphatic chlorinated hydrocarbons underwent dechlorination at a temperature of 180 degrees C. The removal of chlorine from aromatic chlorinated compounds operates in a different mechanism, in which the C-Cl bond scission is promoted significantly by the presence of an alumina and hydrocarbon medium. It was found that chlorobenzene undergoes dechlorination forming phenol and benzene.