Abstract

Effect of the chemical composition and crystal structure type of gadolinium complex oxides on their catalytic activity is studied. It is shown that nanocrystalline powders Gd₂Ti₂O₇, Gd₂Zr₂O₇, and Gd₂Hf₂O₇ form highly symmetrical face-centered сubic crystal structures having localized (in Gd₂Ti₂O₇) and delocalized (in Gd₂Zr₂O₇ and Gd₂Hf₂O₇) oxygen vacancies. At the same time, low-symmetrical crystal structures are formed in Gd₂(WO₄)₃ (the monoclinic structure) and Gd₂(МоO₄)₃ (a mixture of monoclinic and rhombic structures). Catalytic runs show that formation of the cubic structure contributes to an increase in the degree of conversion of propane and causes a shift in cracking temperatures to lower values. Formation of this type of nanocrystalline oxides facilitates the dehydrogenation reaction with propylene selectivity up to 80% at temperatures up to 700 К. Formation of the mixture of monoclinic and rhombic structures in Gd₂(МоO₄)₃ leads to a shift in the degree of conversion to the catalytic temperature range of 700–900 К, in which the dehydrogenation reaction predominates (80%). In the case of the monoclinic structure of Gd₂(WO₄)₃ in the same cracking temperature ranges the process of degradation occurs in parallel; this decreases propylene selectivity to 50% and promotes an increase in the yield of ethylene to 30%.

中文翻译：

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纳米crystalline复合氧化物的化学和相组成对丙烷裂解过程的影响

摘要

研究了complex复合氧化物的化学组成和晶体结构类型对其催化活性的影响。结果表明，纳米晶体粉末Gd ₂ Ti ₂ O ₇，Gd ₂ Zr ₂ O ₇和Gd ₂ Hf ₂ O ₇形成了高度对称的，以局部为中心（在Gd ₂ Ti ₂ O _7中）和非局部化的面心晶体结构。在Gd ₂ Zr ₂ O ₇和Gd ₂ Hf ₂ O _7中）氧空位。同时，形成的低对称的晶体结构在钆₂（WO ₄）₃（单斜晶结构）和Gd ₂（МоO ₄）₃（单斜晶和斜方晶结构的混合物）。催化运行表明，立方结构的形成有助于丙烷转化度的增加，并导致裂化温度转变为较低的值。这种类型的纳米晶体氧化物的形成促进了脱氢反应，在高达700К的温度下，丙烯的选择性高达80％。单斜晶和斜方晶结构中的Gd的混合物的形成₂（МоO ₄）₃导致转化率转变为催化温度范围为700-900К，其中脱氢反应占主导（80％）。在相同的裂解温度范围内，Gd ₂（WO ₄）₃为单斜晶结构时，降解过程是平行发生的。这将丙烯的选择性降低到50％，并将乙烯的收率提高到30％。