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首页> 外文期刊>Catalysis science & technology >A mechanistic study of syngas conversion to light olefins over OXZEO bifunctional catalysts: insights into the initial carbon–carbon bond formation on the oxide
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A mechanistic study of syngas conversion to light olefins over OXZEO bifunctional catalysts: insights into the initial carbon–carbon bond formation on the oxide

机译：氧兹双功能催化剂的合成气转化为烯烃的机械研究：对氧化物上最初的碳 - 碳键形成的见解

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摘要

Direct conversion of syngas into light olefins (C2=–C4=) using bifunctional catalysts composed of oxide and zeolite (OXZEO) has attracted extensive attention in both academia and industry. However, the reaction intermediate produced over the oxide surface is still under debate, and direct atomic-level spectroscopic evidence is still lacking. Herein, we choose ZnGa2O4, Ga2O3 and ZnO combined with mordenite (MOR) zeolite as bifunctional catalysts, which show remarkable distinctions in product selectivity. Ex situ NMR detects several C2+ species (acetate, propionate, and isobutyrate) in addition to C1 species on the oxide surface during syngas conversion. Isotope 13C-labeling experiments and DFT calculations reveal that the first carbon–carbon bond may be attributed to ketene forming on the oxide, which can either be transformed into other C2+ species on the oxide surface or diffuse into zeolite for a subsequent reaction. This provides direct spectroscopic evidence for the initial carbon–carbon bond formation on the oxide. The difference in the intermediates on the oxide can account for the difference in product selectivity on OXZEO bifunctional catalysts, in which ketene formation may lead to high selectivity to ethylene.
机译：使用由氧化物和沸石（Oxzeo）组成的双功能催化剂（Oxzeo）直接转化合成胶（C2 = –C4 =）已引起了学术界和工业的广泛关注。然而，在氧化物表面上产生的反应中间体仍在争论中，直接原子水平的光谱证据仍然缺乏。本文中，我们选择Znga2O4，Ga2O3和ZnO与冬丁岩（MOR）沸石作为双功能催化剂，在产品选择性方面表现出显着的区别。除了在合同体转化期间，EX NMR还检测出几种C2+物种（乙酸，丙酸和异丁二烯酸酯）。同位素13C标记的实验和DFT计算表明，第一个碳 - 碳键可能归因于氧化物上形成的酮 - 可以将其转化为氧化物表面上的其他C2+物种，或者可以弥漫到Zeolite中以进行后续反应。这为氧化物上初始碳 - 碳键形成提供了直接的光谱证据。氧化物中中间体的差异可以解释oxzeo双功能催化剂上产品选择性的差异，其中酮的形成可能导致对乙烯的高选择性。

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