Mn-Al和Cu-Mn-Al复合氧化物催化苯甲醇选择氧化反应

用溶胶-凝胶法制备了不同组成的Mn-Al和Cu-Mn-Al复合氧化物两组催化剂,用于苯甲醇选择氧化反应.用X射线衍射(XRD)、N2物理吸附(BET)、扫描电镜(SEM)、H_2程序升温还原(H_2-TPR)、O_2程序升温脱附(O_2-TPD)和X射线光电子能谱(XPS)技术对催化剂进行了结构表征,考察了催化剂组成对催化活性的影响.结果表明:以甲苯为溶剂,O_2为氧化剂,353 K反应5 h,Mn_2Al和Cu_(0.3)Mn_(0.7)Al_2催化剂上的苯甲醇转化率分别为36.6%和40.9%,苯甲醛选择性均为100%.进一步研究表明:催化剂活性与其H2还原性和O_2吸附性有关,高活性的催化剂吸附氧多,生成的活性氧易参与反应.

Selective catalytic oxidation of benzyl alcohol over Mn-Al and Cu-Mn-Al composite oxide catalysts

A series of Mn-Al and Cu-Mn-Al composite oxides with different compositions were prepared by sol-gel method and applied in selective oxidation of benzyl alcohol to benzaldehyde. The catalysts were characterized by means of techniques such as X-ray diffraction (XRD), N2 physisorption (BET), Scanning electron microscope (SEM), Temperature-programmed reduction of hydrogen (H2-TPR), Temperature-programmed desorption of oxygen (O2-TPD), and X-ray photoelectron spectroscopy (XPS). The effect of reaction conditions and catalyst compositions on catalytic activity was investigated. It is shown that the high conversion of benzyl alcohol can be obtained under the following reaction conditions: O2 is used as oxidant, toluene as solvent, the content of benzyl alcohol 0.1ml, reaction temperature 353K, and reaction time 5h. Among Mn-Al composite oxides, the catalyst with composition of Mn2Al exhibits high catalytic activity, over which the conversion of benzyl alcohol reaches 36.6%. Of Cu-Mn-Al composite oxide catalysts, the Cu0.3Mn0.7Al2 with 40.9% conversion of benzyl alcohol is more active than others. Over all catalysts, the selectivity of benzaldehyde maintains 100%. The characterization data indicates that the catalyst with higher activity has more deficit oxygen, more facile adsorption and activation for oxygen to participate in the oxidation reaction of benzyl alcohol.