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首页> 外文期刊>Catalysis science & technology >Structure-activity correlation in aerobic cyclohexene oxidation and peroxide decomposition over CoxFe3-xO4 spinel oxides
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Structure-activity correlation in aerobic cyclohexene oxidation and peroxide decomposition over CoxFe3-xO4 spinel oxides

机译：有氧环己烯氧化和过氧化物分解Coxfe3-XO4尖晶石氧化物的结构活性相关性

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摘要

Nanoparticulate CoxFe3-xO4 (0 <= x <= 3) catalysts were prepared by spray-flame synthesis and applied in liquid-phase cyclohexene oxidation with O-2 as oxidant. The catalysts were characterized in detail using N-2 physisorption, XRD, TEM, XPS, FTIR, Raman, and Mossbauer spectroscopy. A volcano plot was obtained for the catalytic activity in cyclohexene oxidation as a function of the Co content with a maximum at x = 1. Thus, CoFe2O4 achieved the highest degree of cyclohexene conversion and the fastest decomposition rate of the key intermediate 2-cyclohexene-1-hydroperoxide. Kinetic studies and a stability test were performed over CoFe2O4, showing that cyclohexene oxidation follows first-order kinetics with an apparent activation energy of 58 kJ mol(-1). The catalytic hydroperoxide decomposition during cyclohexene oxidation was further investigated using H2O2 and tert-butyl hydroperoxide as simpler surrogates resulting in similar volcano-type correlations. The increase in catalytic activity with increasing Fe content with a maximum at x = 1 is ascribed to the increasing concentration of octahedrally coordinated Co2+ cations in the spinel structure leading to the presence of coordinatively unsaturated Co-3c(2+) surface sites, which are identified to be the most active sites for 2-cyclohexene-1-hydroperoxide decomposition in cyclohexene oxidation.
机译：纳米含量Coxfe3-XO4（0 <= x <= 3）通过喷雾型合成制备催化剂，并用O-2作为氧化剂施加在液相环己烯氧化中。使用N-2物理学，XRD，TEM，XPS，FTIR，Raman和Mossbauer光谱详细介绍了催化剂。获得了环己烯氧化中的催化活性的火山图，这是CO含量的函数，最大值在x = 1处。 1-氢过氧化物。动力学研究和稳定性测试是在COFE2O4上进行的，表明环己烯氧化遵循一阶动力学，明显的活化能为58 kJ mol（-1）。使用H2O2和TERT叔丁基氢过氧化物作为更简单的替代物，进一步研究了环己烯氧化过程中催化氢过氧化物的分解，从而导致相似的火山型相关性。随着Fe含量的增加，催化活性的增加，最大值在x = 1处的最大值归因于在尖晶石结构中八面体配位的二氧化碳+阳离子的浓度增加，从而导致存在协调性不饱和CO-3C（2+）表面位点，这些表面位点是被确定为环己烯氧化中2-环己烯-1-羟化氧化物分解的最活跃的位点。

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