Abstract

Potassium polyferrites K₂\({\text{Fe}}_{{1 - q}}^{{{\text{II}}}}\)M_q\({\text{Fe}}_{{10}}^{{{\text{III}}}}\)O₁₇ (where M is Mg and Zn) and K_2–2qFe^IIM_q\({\text{Fe}}_{{10}}^{{{\text{III}}}}\)O₁₇ (where M is Ca and Sr; q = 0–0.4) are synthesized to determine the effect of the size of a doubly charged dopant ion on their catalytic properties. The mechanism of the effect of doubly charged cation additives on the activity, selectivity, and corrosion resistance of potassium β'' polyferrite is identified. It is shown for the first time that doubly charged cations are distributed differently in the structure of β'' polyferrite depending on their size: either they are in a spinel-like block and then replace Fe²⁺ ions, or they replace potassium in interblock space. The Mg²⁺ and Zn²⁺ ion additives sharply reduce the catalytic activity and selectivity of β'' polyferrite. Such additives are undesirable. Small amounts of Ca²⁺ and Sr²⁺ cations greatly improve the corrosion resistance of the catalysts due to a drop in the mobility of potassium ions within a cation-conducting layer.

中文翻译：

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双电荷离子添加剂对催化活性钾铁氧体活性和化学稳定性的影响

摘要

钾多铁氧体K ₂ \（{\ text {Fe}} _ {{1-q}} ^ {{{\ text {II}}}} \\） M _q \（{\ text {Fe}} __ {{10 }} ^ {{{{\ text {III}}}} \\} O ₁₇（其中M为Mg和Zn）和K _{2–2 q} Fe ^II M _q \（{\ text {Fe}} _ {{10} } ^ {{{\ text {III}}}} \） O ₁₇（其中M为Ca和Sr；q= 0-0.4）合成以确定双电荷掺杂剂离子的大小对其催化性能的影响。确定了双电荷阳离子添加剂对β''聚铁酸钾的活性，选择性和耐蚀性的影响机理。首次表明，双电荷阳离子根据其尺寸在β''聚铁氧体结构中的分布不同：要么是它们呈尖晶石状，然后取代了Fe ²⁺离子;要么是它们之间的取代了钾离子空间。Mg ²⁺和Zn ²⁺离子添加剂会大大降低β''聚铁氧体的催化活性和选择性。这样的添加剂是不希望的。少量的Ca ²⁺和Sr ²⁺ 由于钾离子在阳离子导电层中的迁移率下降，阳离子极大地改善了催化剂的耐腐蚀性。