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首页> 外文学位 >Carbon monoxide hydrogenation and propylene conversion over palladium-impregnated ZSM-5 and SAPO molecular sieves.
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Carbon monoxide hydrogenation and propylene conversion over palladium-impregnated ZSM-5 and SAPO molecular sieves.

机译：在钯浸渍的ZSM-5和SAPO分子筛上进行一氧化碳加氢和丙烯转化。

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The catalytic properties of ZSM-5 and silicoaluminophosphate (SAPO) molecular sieves, studied during CO hydrogenation over Pd/ZSM-5 and Pd/SAPO catalysts and during propylene conversion over ZSM-5 and SAPO catalysts, have been correlated with their physico-chemical characteristics, as determined by infrared spectroscopy, ammonia desorption experiments, and electron microscopy. Reaction rates and product distributions from syngas conversion over Pd/ZSM-5 were greatly affected by the zeolitic cation. While sodium and lanthanum cations enhanced the CO hydrogenation activity of the palladium sites, Pd/NaZSM-5 yielded primarily oxygenates (methanol and dimethyl ether), while Pd/HZSM-5 and Pd/LaZSM-5 catalyzed the formation of light alkanes and polymethylbenzenes. Synthesis of C{dollar}sb2{dollar}+ hydrocarbons from syngas occurred through a bifunctional pathway, which included palladium-catalyzed methanol synthesis followed by methanol conversion on strong acid sites within the ZSM-5 micropores. A similar route accounted for the formation of C{dollar}sb2{dollar}+ alkanes during CO hydrogenation over palladium-impregnated silicoaluminophosphate (SAPO) molecular sieves. The conversion of oxygenates to hydrocarbons over SAPO catalysts followed an autocatalytic pathway. For both Pd/ZSM-5 and Pd/SAPO catalysts, the rate of palladium-catalyzed olefin hydrogenation and the characteristics of the molecular sieves, including acidity, micropore diameter, and particle size, played an important role in determining the product distribution.; The physical and chemical properties of ZSM-5 and SAPO molecular sieves were also compared to their activity for propylene conversion. ZSM-5 catalysts possessing strong acid sites yielded the most products, primarily of C{dollar}sb4{dollar}-C{dollar}sb7{dollar} olefins. Despite attaining propylene conversion levels far below equilibrium predictions, the reaction over HZSM-5 and CoZSM-5 appeared to be thermodynamically controlled. SAPO molecular sieves, showing significantly less activity than the ZSM-5 catalysts, deactivated quickly. Mass transfer phenomena influenced the rate of catalyst deactivation as well as the product distribution over SAPO-5 and SAPO-34. Conversion of propylene over SAPO-11 yielded only hexene products. As with the CO hydrogenation studies, trends observed during propylene conversion over ZSM-5 and SAPO catalysts were directly related to specific structural or chemical properties of the molecular sieves.
机译：在Pd / ZSM-5和Pd / SAPO催化剂上进行CO加氢以及在ZSM-5和SAPO催化剂上进行丙烯转化期间，研究了ZSM-5和硅铝磷酸盐（SAPO）分子筛的催化性能与它们的物理化学相关联通过红外光谱，氨解吸实验和电子显微镜确定的特性。沸石阳离子对Pd / ZSM-5合成气转化反应速率和产物分布的影响很大。尽管钠和镧阳离子增强了钯位点的CO加氢活性，但Pd / NaZSM-5主要产生含氧化合物（甲醇和二甲醚），而Pd / HZSM-5和Pd / LaZSM-5催化形成轻质烷烃和聚甲基苯。由合成气通过双功能途径合成C {dolb} sb2 {dollar} +烃，该途径包括钯催化的甲醇合成，然后在ZSM-5微孔内的强酸位点上进行甲醇转化。一种类似的途径解释了在钯浸渍的硅铝磷酸盐（SAPO）分子筛上进行CO加氢过程中C {sbssb2 {美元} +烷烃的形成。在SAPO催化剂上，含氧化合物向烃的转化遵循自动催化途径。对于Pd / ZSM-5和Pd / SAPO催化剂，钯催化的烯烃加氢速率和分子筛的特性（包括酸度，微孔直径和粒径）在决定产物分布方面起着重要作用。还将ZSM-5和SAPO分子筛的物理和化学性质与其对丙烯转化的活性进行了比较。具有强酸中心的ZSM-5催化剂产生的产物最多，主要是C {dollar} sb4 {dollar} -C {dollar} sb7 {dollar}烯烃。尽管达到的丙烯转化水平远低于平衡预测值，但HZSM-5和CoZSM-5上的反应似乎是热力学控制的。 SAPO分子筛的活性大大低于ZSM-5催化剂，因此很快失活。传质现象影响了催化剂的失活速率以及SAPO-5和SAPO-34上的产物分布。丙烯在SAPO-11上的转化仅产生己烯产物。与CO加氢研究一样，通过ZSM-5和SAPO催化剂在丙烯转化过程中观察到的趋势与分子筛的特定结构或化学性质直接相关。

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