Carbonylation of ethane with carbon monoxide over Zn-modified ZSM-5 zeolites studied by in situ solid-state NMR spectroscopy
Carbonylation of ethane with carbon monoxide over Zn-modified ZSM-5 zeolites studied by in situ solid-state NMR spectroscopy
复制标题
原位固态核磁共振波谱研究乙烷与一氧化碳在 Zn 改性 ZSM-5 沸石上的羰基化反应
DOI：
10.1016/j.jcat.2016.11.009
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发表时间：
2017
影响因子：
7.3
通讯作者：
Deng Feng
中科院分区：
文献类型：
--
作者：
Wang Xiumei;Xu Jun;Qi Guodong;Wang Chao;Wang Weiyu;Gao Pan;Wang Qiang;Liu Xiaolong;Feng Ningdong;Deng Feng
采用原位固体核磁共振技术研究了在Zn改性ZSM-5分子筛（简称Zn/ZSM-5）上乙烷与CO羰基化合成羧酸的反应，并在298-623 K温度范围内交替使用13 C同位素标记的反应物监测共反应。NMR实验结果表明，在反应过程中形成了表面乙基锌和甲氧基锌物种，并确定为关键中间体。通过在反应体系中加入O2和H2，进一步考察了这些中间体在氧化和还原条件下的反应活性。发现乙烷最初被活化成锌-乙基物质，其显示出与有机金属化合物如二乙基锌类似的反应性。乙基锌物种与CO氧化产生的CO2的相互作用产生丙酸。通过乙基锌物质经由形成的乙烯中间体脱氢形成副产物如芳烃。我们还发现，乙烷发生氢解，并产生副产物甲烷，这导致通过与CO2羧化形成乙酸。此外，CO被转化为表面甲氧基物种，其可以与CO通过Koch型羰基化反应生成乙酸。
The carbonylation reaction of ethane with CO to produce carboxylic acid was studied over zinc-modified ZSM-5 zeolite (denoted as Zn/ZSM-5) using in situ solid-state NMR spectroscopy.13C-isotope-labeled reactants were alternatively used to monitor the co-reaction at temperatures of 298–623 K. The NMR experimental results demonstrated that surface zinc-ethyl and methoxy species were formed and identified as key intermediates in the reaction. The reactivity of these intermediates was further explored under both oxidizing and reducing conditions by adding O2and H2into the reaction system. It was found that ethane was initially activated into zinc–ethyl species that show reactivity similar to that of organometallic compounds such as diethyl zinc. The interaction of zinc–ethyl species with CO2resulting from the oxidation of CO produces propanoic acid. Side products such as aromatics were formed by dehydrogenation of zinc–ethyl species via the formed ethene intermediates. We also found that hydrogenolysis of ethane occurred and gave rise to byproduct methane, which led to the formation of acetic acid by carboxylation with CO2. Additionally, CO was converted into surface methoxy species, which could react with CO to produce acetic acid via a Koch-type carbonylation reaction.