PULSE-QUENCH CATALYTIC REACTOR STUDIES REVEAL A CARBON-POOL MECHANISM IN METHANOL-TO-GASOLINE CHEMISTRY ON ZEOLITE HZSM-5
PULSE-QUENCH CATALYTIC REACTOR STUDIES REVEAL A CARBON-POOL MECHANISM IN METHANOL-TO-GASOLINE CHEMISTRY ON ZEOLITE HZSM-5
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DOI：
10.1021/ja973920z
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发表时间：
1998-03
影响因子：
15
通讯作者：
Patrick W. Goguen;Teng Xu;D. H. Barich;Timothy W. Skloss;Weiguo Song;Zhike Wang;J. Nicholas;J. F. Ha
中科院分区：
文献类型：
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作者：
Patrick W. Goguen;Teng Xu;D. H. Barich;Timothy W. Skloss;Weiguo Song;Zhike Wang;J. Nicholas;J. F. Ha
HZSM-5沸石催化甲醇制汽油（MTG）化学1的机理是多相催化中研究最深入的问题之一。使用密封样品的原位核磁共振方法已被多个小组应用，以更好地了解 MTG 化学。 2-5 最近的理论研究主要集中在吸附物质的结构6 和导致第一个碳-碳键的反应途径。 7-9 该反应的两个特征很明显：甲醇与二甲醚和水达到平衡，并且在开始大量碳氢化合物合成之前有一个诱导期。我们在与传统流动反应器相同的条件下，在 MTG 化学的首次 NMR 研究中使用了我们最近开发的脉冲猝灭催化反应器 10。在从反应温度快速（200 ms）淬灭后，在室温下通过 NMR 表征催化剂床上的有机物质。此外，通过气相色谱或GC-MS对高温下离开反应器的挥发性产物进行分析。图 1 报告了脉冲淬火实验中催化剂床的 13C MAS NMR 谱，其中 [13C]-甲醇在 643 K 下注入到床 11 上，并在淬火之前与连续 He 载气流反应 200 ms 至 16 s。诱导期在反应的前 2 秒内很明显：甲醇部分转化为二甲醚，但检测到的唯一碳氢化合物是在 1 秒及之后的 GC 痕迹中看到的痕量乙烯，有时在催化剂的 NMR 谱中看到痕量异丁烷。四
The mechanism of methanol-to-gasoline (MTG) chemistry1 catalyzed by zeolite HZSM-5 is one of the most intensively studied problems in heterogeneous catalysis. In situ NMR methods using sealed samples have been applied by several groups in an effort to better understand MTG chemistry. 2-5 Recent theoretical investigations have focused on the structure of adsorbed species6 and reaction pathways leading to the first carbon-carbon bond. 7-9 Two features of the reaction are clear: methanol equilibrates with dimethyl ether and water and there is an induction period before the onset of extensive hydrocarbon synthesis.We have used our recently developed pulse-quench catalytic reactor10 in the first NMR study of MTG chemistry under conditions identical to conventional flow reactors. The organic species on the catalyst bed were characterized by NMR at room temperature following a rapid (200 ms) quench from reaction temperature. In addition, the volatile products which exited the reactor at high temperature were analyzed by gas chromatography or GC-MS. Figure 1 reports 13C MAS NMR spectra of the catalyst beds from pulse-quench experiments in which [13C]-methanol was injected onto the bed11 at 643 K and allowed to react with continuous He carrier gas flow for between 200 ms and 16 s prior to quench. The induction period was obvious in the first 2 s of the reaction: methanol was partially converted to dimethyl ether, but the only hydrocarbons detected were traces of ethylene seen in the GC traces at 1 s and later and sometimes traces of isobutane seen in the NMR spectra of the catalyst. Four