Zoya N. Lashchinskaya, Anton A. Gabrienko, Alexander V. Toktarev, Alexander G. Stepanov
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引用次数: 0
摘要
银改性沸石在碳氢化合物原料价值化和有机化合物氧化方面表现出良好的特性。在金属改性沸石上选择性氧化轻烯的科学兴趣框架内，在 296-773 K 的温度下，通过 13C (CP) MAS NMR 光谱监测了 Ag/H-ZSM-5 沸石上丙烯在分子氧存在下的转化过程。据推测，氧气和丙烯竞争 Ag+ 吸附位点，从而促使丙烯吸附在沸石的布氏硬度酸位点（BAS）上，并通过低聚和共聚进一步转化。在分子氧氧化丙烯的产物中，只有二氧化碳被 13C MAS NMR 检测到，这意味着 Ag/H-ZSM-5 在烯烃全氧化过程中具有很高的活性。因此可以推断，银改性沸石不是丙烯选择性氧化为氧化丙烯和含羰基有机物的理想催化剂。
13C MAS NMR Mechanistic Study of Propene Transformation on Silver-Modified ZSM-5 Zeolite in the Presence of Molecular Oxygen
Silver-modified zeolites have demonstrated promising properties for hydrocarbon feedstock valorization and the oxidation of organic compounds. Within the frame of the scientific interest for selective oxidation of light alkenes on metal-modified zeolites, the transformation of propene on Ag/H-ZSM-5 zeolite in the presence of molecular oxygen has been monitored by 13C (CP) MAS NMR spectroscopy at 296–773 K. Silver-allyl intermediate species have been detected by 13C CP/MAS NMR, indicating that Ag+ sites are involved in propene transformation. It is assumed that oxygen and propene compete for the Ag+ adsorption sites, thus prompting propene adsorption on zeolite Brønsted acid sites (BAS) and its further transformation by oligomerization and conjunct polymerization. Among the products of propene oxidation by molecular oxygen, only carbon dioxide has been detected by 13C MAS NMR, implying high activity of Ag/H-ZSM-5 in alkene total oxidation. It is thus inferred that silver-modified zeolite is not a promising catalyst for propene selective oxidation to propene oxide and carbonyl group containing organics.
期刊介绍：
Applied Magnetic Resonance provides an international forum for the application of magnetic resonance in physics, chemistry, biology, medicine, geochemistry, ecology, engineering, and related fields.
The contents include articles with a strong emphasis on new applications, and on new experimental methods. Additional features include book reviews and Letters to the Editor.
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