以聚乙二醇(PEG)作为分散剂, 采用共沉淀法合成La-Co-O复合氧化物, 考察添加不同分子量的PEG (0, 2 000, 6 000, 20 000 g·mol-1) 对复合氧化物的物化性质及苯完全氧化性能的影响。 采用N2物理吸附、 XRD、 SEM、 H2-TPR、 O2-TPD和XPS进行催化剂表征。 苯完全氧化反应结果显示催化剂活性顺序为LCO-PEG6000>LCO>LCO-PG20000>LCO-PG2000, LCO-PEG6000催化剂在383 ℃时对苯的转化率达到99%, 比LCO低126 ℃。 N2物理吸附实验表明所制备的样品的SBET均为9～10 m2·g-1。 XRD分析显示合成的催化剂均为LaCoO3钙钛矿主相伴生少量La2O3和Co3O4杂相, 但添加PEG有利于钙钛矿主相的形成。 尤其是添加PEG6000有效地抑制了催化剂颗粒的团聚, 合成的样品颗粒均匀且尺寸最小。 H2-TPR和O2-TPD结果表明该催化剂具有更高的还原性能和晶格氧迁移能力, 同时XPS分析显示表面活性Co3＋含量最高, 这些性质使其具有最高的催化氧化活性。

La-Co-O mixed oxides (LCO) were prepared by co-precipitation method with the presence of polyethylene glycol (PEG) as dispersant. The influence of adding different molecular weight of PEG (0, 2 000, 6 000, 20 000 g·mol-1) on the physicochemical and catalytic properties of La-Co-O mixed oxides for total oxidation of benzene was investigated. The samples were characterized by means of N2 physical adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction by H2 (H2-TPR), temperature-programmed desorption of O2 (O2-TPD), and X-ray photoelectron spectroscopy (XPS). The order of catalytic activity was found to be LCO-PEG6000>LCO>LCO-PG20000>LCO-PG2000. Particularly, LCO-PEG6000 exhibited benzene conversion of 99% at temperature as low as 383 ℃, which was 126 ℃ lower than that of LCO. The characterization result reveals that all samples had a BET surface area of about 9～10 m2·g-1. The XRD result shows that on all samples LaCoO3 perovskite was mainly formed together with a small amount of La2O3 and Co3O4. The addition of PEG was favorable for the formation of LaCoO3 perovskite. Particularly, the addition of PEG-6000 effectively suppressed the agglomeration of LaCoO3 perovskite, giving rise to small and uniform particles as observed by SEM. Moreover, the results of H2-TPR and O2-TPD indicate that the obtained La-Co-O mixed oxides showed higher reducibility and lattice oxygen mobility, and the Co 2p XPS analysis suggests that more surface Co3+ active species were presented by the addition of PEG-6000. These properties are thought to contribute to the high activity in benzene total oxidation.