Shape Effect of ZnO Crystals as Cocatalyst in Combined Reforming-Hydrogenolysis of Glycerol
Shape Effect of ZnO Crystals as Cocatalyst in Combined Reforming-Hydrogenolysis of Glycerol
复制标题
ZnO晶体作为甘油联合重整-氢解助催化剂的形状效应
DOI：
10.1021/cs400526s
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发表时间：
2013-10-01
期刊：
影响因子：
12.9
通讯作者：
Zong, Baoning
中科院分区：
文献类型：
--
作者：
Hu, Jiye;Fan, Yiqiu;Zong, Baoning
通过调节前驱体浓度，采用简单的溶液法可控合成了不同长径比的六方片状和棒状ZnO晶体。用扫描电子显微镜（SEM）观察了合成的ZnO晶体的形貌和尺寸。通过X射线衍射（XRD）、透射电子显微镜（TEM）和选区电子衍射（SAED）对样品的结构和生长习性进行了表征。结果表明，随着前驱体浓度的降低，ZnO晶体沿c轴方向沿着伸长，{001}晶面直径减小，形貌由六方盘状向棱柱状演化。结果，ZnO晶体的{100}非极性面和{001}极性面的比例彼此不同。在无H2-存在下，以ZnO晶体为助催化剂，Ni 40 Mo 10为骨架催化甘油重整-氢解反应。一个显着的，形状依赖于对C3氢解产物的选择性和1，2-丙二醇（1，2-PDO）的生产率的影响被确定。具有较大比例的非极性平面的ZnO在甘油到C3产物的CRH中更有效。确定了{100}非极性平面的表面积与1，2-PDO的产生速率之间的良好线性关系。这是由于甘油重整过程中化学吸附的CO2原位增强了ZnO非极性面的刘易斯酸性，大大加速了甘油脱水生成丙酮醇（1，2-PDO的中间体）的过程。
Disk- and rod-shaped hexagonal ZnO crystals with various length-to-diameter aspect ratios were controllably synthesized via a facile solution route by adjusting the precursor concentration. The shape and the dimension of the synthesized ZnO crystals were observed by scanning electron Microscopy (SEM). The wurtzite structure and the growth habit were determined by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) coupled with selected area electron diffraction (SAED). It is found that with the lowering of the precursor concentrations, the ZnO crystals were elongated along the c-axis, and the diameter of the {001} planes was reduced, leading to shape evolution from hexagonal disk to prismatic rod. As,a result, the ZnO crystals ere different from each other in the proportion of the {100} nonpolar planes and the {001} polar planes. The well-defined ZnO crystals were used as the cocatalyst with skeletal Ni40Mo10 in the combined reforming-hydrogenolysis (CRH) of glycerol in the absence of adventitious H-2. A remarkable, shape dependent effect on the selectivity to the C3 hydrogenolysis products and the production rate of 1,2-propandiol (1,2-PDO) was identified. ZnO with a larger proportion of the nonpolar planes was more effective in the CRH of glycerol to the C3 products. An excellent linear relationship between the surface area of the {100} nonpolar planes and the production rate of 1,2-PDO was identified. This is attributed to the in situ enhancement of the Lewis acidity of the nonpolar planes of ZnO by chemisorbed CO2 from the reforming of glycerol, which greatly accelerates the dehydration of glycerol to acetol, the intermediate to 1,2-PDO.