The conversion of chloromethane to light olefins over SAPO-34: The influence of dichloromethane addition
The conversion of chloromethane to light olefins over SAPO-34: The influence of dichloromethane addition
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DOI：
10.1016/j.apcata.2009.07.047
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发表时间：
2009-10
影响因子：
5.5
通讯作者：
M. H. Nilsen;S. Svelle;Sharmala Aravinthan;U. Olsbye
中科院分区：
文献类型：
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作者：
M. H. Nilsen;S. Svelle;Sharmala Aravinthan;U. Olsbye
考察了CH_2Cl_2杂质对SAPO-34催化剂上CH_3Cl转化为烯烃的影响。在（Al+P）/Si=11的典型SAPO-34催化剂上，在400°C、WHSV=8h-1、p（CH 3Cl）= 620毫巴和p（CH 2Cl 2）= 65毫巴下，CH 3Cl与CH 2Cl 2以10：1的比率共反应。结果表明，CH_2Cl_2促进了芳香族化合物的生成，并导致CH_3Cl制烯烃反应催化剂的快速失活。然而，通过加入CH 2Cl 2，通常观察到在达到最大转化率之前活性增加的诱导期显著缩短。以10：1的比例进料12 CH 3Cl和13 CH 2Cl 2的混合物导致形成具有约5%13C的烯烃，其与在相同实验中保留在SAPO-34晶体内的芳烃（反应中间体和焦炭）中的13 C含量不可区分。这表明CH 2Cl 2参与了导致两种产物的反应，包括芳香族反应中间体的形成和失活。通过研究二甲苯/二氯甲烷混合物和2，5-二甲基苄基氯单独的反应，发现将二氯甲烷中的碳原子引入气相产物和焦炭中的假设反应步骤是合理的。在CH 3Cl至烯烃的所需转化率和CH 2Cl 2添加的有害影响之间的密切机械联系对商业SAPO-34基CH 3Cl至烯烃应用中的CH 3Cl原料的纯度施加了限制。
The effect of CH2Cl2impurities on the conversion of CH3Cl to olefins over SAPO-34 has been investigated. CH3Cl was co-reacted with CH2Cl2in a 10:1 ratio at 400°C, WHSV=8h−1, p(CH3Cl)=620mbar and p(CH2Cl2)=65mbar, over a typical SAPO-34 catalyst with (Al+P)/Si=11. It was observed that CH2Cl2promotes the formation of aromatic compounds and leads to rapid deactivation of the catalyst for the CH3Cl to olefins reaction. The induction period, which is typically observed as an increase in activity before maximum conversion is reached is, however, significantly shortened by the addition of CH2Cl2. Feeding a mixture of12CH3Cl and13CH2Cl2in a 10:1 ratio led to formation of olefins with about 5%13C, which was indistinguishable from the13C content in the aromatic hydrocarbons (reaction intermediates and coke) retained inside the SAPO-34 crystals in the same experiment. This shows that CH2Cl2takes part in the reactions leading to both products, including the formation of aromatic reaction intermediates, and deactivation. Hypothesized reaction steps for the incorporation of carbon atoms from CH2Cl2into both gas phase products and coke were found to be plausible by studying the reactions of xylene/CH2Cl2mixtures and of 2,5-dimethylbenzyl chloride alone. The intimate mechanistic links between the desired conversion of CH3Cl to olefins and the detrimental effects of CH2Cl2addition imposes restrictions on the purity of the CH3Cl feedstock in a commercial SAPO-34 based CH3Cl to olefins application.