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合成出不同晶型结构的锰氧化物,考察了以它们为载体负载Pd后催化苯酚氧化羰基化合成碳酸二苯酯(DPC)的活性,并通过X射线衍射、N2吸附、电位滴定和X射线光电子能谱对催化剂进行了表征,分析了载体的晶型结构和表面氧物种对催化剂活性的影响。实验结果表明,锰氧八面体分子筛(K-OMS-2)和层状δ-MnO2为载体时催化剂的活性较高,DPC收率可达8.4%和9.2%。K-OMS-2和δ-MnO2中锰的平均氧化态较低,低价锰的存在导致更多的晶格缺陷和空位的形成,有利于活性的提高。催化剂表面氧物种主要为晶格氧和羟基氧,羟基氧的含量越高,形成的氧空位越多,催化活性越高。
Manganese oxides with different crystal structures were synthesized. The catalytic activity of Pd (PP) for the oxidative carbonylation of phenol to DPC was investigated. The effects of XRD, N2 adsorption, potentiometric titration and X-ray diffraction The photoelectron spectroscopy was used to characterize the catalysts. The effects of the crystal structure of the support and the surface oxygen species on the catalyst activity were analyzed. The experimental results show that the catalyst activity is high when manganese-oxygen octahedral molecular sieve (K-OMS-2) and layered δ-MnO2 are supported as carriers, and the yield of DPC can reach 8.4% and 9.2%. The average oxidation state of manganese in K-OMS-2 and δ-MnO2 is lower. The existence of low-price manganese leads to more lattice defects and vacancy formation, which is beneficial to the increase of activity. The oxygen species on the surface of the catalyst are mainly lattice oxygen and hydroxyl oxygen. The higher the content of oxyhydroxide, the more the oxygen vacancies are formed and the higher the catalytic activity.