Magnetic CoFe2O4 nanocrystal: A novel and efficient heterogeneous catalyst for aerobic oxidation of cyclohexane
Magnetic CoFe2O4 nanocrystal: A novel and efficient heterogeneous catalyst for aerobic oxidation of cyclohexane
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DOI：
10.1016/j.molcata.2009.03.010
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发表时间：
2009-07
影响因子：
--
通讯作者：
Jinhui Tong;Lili Bo;Zhen Li;Z. Lei;C. Xia
中科院分区：
文献类型：
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作者：
Jinhui Tong;Lili Bo;Zhen Li;Z. Lei;C. Xia
采用简单的溶胶-凝胶自燃烧法制备了5种不同CoII：FeIII摩尔比（1：4.0，1：2.8，1：2.0，1：1.5，1：1.1）的磁性纳米晶尖晶石型钴铁氧体复合氧化物，并用X射线衍射（XRD）、傅立叶红外光谱（FT-IR）和透射电镜（TEM）对其进行了表征。在无溶剂、无还原剂的条件下，考察了它们在氧气氧化环己烷反应中的催化性能。结果表明，该催化剂对环己烷的多相氧化反应具有较高的催化活性。特别是以纯CoFe_2 O_4为催化剂，在418 K、1.6MPa的初始氧压下反应6.0h，转化数达到288，环己酮和环己醇的选择性达到92.4%。考察了初始氧气压力、反应温度、反应时间和自由基引发剂对CoFe 2 O 4催化氧化环己烷反应的影响。该催化剂可以很容易地通过外部磁体分离，并且在连续五次重复使用时没有观察到明显的活性损失。CoFe_2O_4对直链烷烃的氧化也有很好的催化效果。
Magnetic nanocrystalline spinel-type cobalt ferrite complex oxides were prepared by a simple sol–gel auto-combustion method at five different molar ratios of CoIIto FeIII(1:4.0, 1:2.8, 1:2.0, 1:1.5, and 1:1.1) and characterized by X-ray diffractometry (XRD), Fourier transform infrared spectrophotometry (FT-IR) and transmission electron microscopy (TEM). Their catalytic performance was evaluated in the oxidation of cyclohexane with oxygen as oxidant in the presence of neither solvents nor reducing agents. It has been revealed that the catalysts had high catalytic activities for heterogeneous oxidation of cyclohexane. Especially, when pure CoFe2O4was used as catalyst; excellent results with turnover number of 288 and 92.4% selectivity for cyclohexanone and cyclohexanol was obtained under 1.6MPa of initial oxygen pressure at 418K after 6.0h of reaction. The influences of initial oxygen pressure, reaction temperature, reaction time, and free-radical initiator on the oxidation of cyclohexane over CoFe2O4were investigated. The catalyst can be easily separated by an external magnet and no obvious loss of activity was observed when reused in five consecutive runs. CoFe2O4was proved to be also efficient for oxidation of linear alkanes.