含钯类水滑石衍生复合氧化物Pd/M3AlO(M=Mg,Co, Ni,Cu, Zn)催化剂上氯苯的催化氧化

采用共沉淀法制备了系列含Pd类水滑石材料, 类水滑石基体为M3Al-HT (M=Mg, Co, Ni, Cu, Zn), 经焙烧制备出含Pd类水滑石衍生复合氧化物催化剂. 通过X射线衍射(XRD), 热重-差热分析(TG-DTG), H2程序升温还原(H2-TPR), O2程序升温脱附(O2-TPD)和N2吸脱附等表征技术手段研究了不同二价金属元素对含Pd类水滑石衍生复合氧化物催化剂物理化学性质及其对挥发性有机污染物氯苯催化氧化性能的影响. XRD和TG-DTG结果表明, 不同二价金属元素, 除Cu外, 都能形成类水滑石层状结构, Pd在不同类水滑石前驱物中均能良好分散. 不同的二价金属元素对催化剂性能的影响不同, 其中Pd/Co3AlO催化剂表现出最高的氯苯催化氧化活性, 其起燃温度和全转化温度分别为182和283 ℃. H2-TPR和O2-TPD测试表明, Pd和类水滑石衍生复合氧化物存在着协同作用, Pd的引入促进了复合氧化物的还原, 从而影响氧化物的氧化还原性能. Pd/M3AlO系列催化剂的活性主要受催化剂的氧化还原性能及其表面活性氧物种的影响.

Catalytic Oxidation of Chlorobenzene on Composite Oxide Pd/M3AlO (M=Mg, Co, Ni, Cu, Zn) Catalysts Derived from Pd-Contained Hydrotalcite Precursors

A series of Pd-containing hydrotalcite precursors (M_3Al-HT) with different M~(2+)(M=Mg, Co, Ni, Cu, Zn) ions were synthesized by a co-precipitation method. Pd/M_3AlO catalysts were derived from these hydrotalcite-like compounds by calcination. X-ray Diffraction (XRD), thermogravimetry-differential thermal gravimetry (TG-DTG), N_2 adsorption and desorption, temperature programmed reduction (H_2-TPR), and temperature programmed desorption (O_2-TPD) techniques were used to study the influence of different M~(2+) ions on the composition and structures of the Pd/ M_3AlO catalysts and their performance during the catalytic oxidation of chlorobenzene. XRD and TG-DTG data showed that hydrotalcite precursors could be successfully prepared with different M~(2+) ions except Cu~(2+) ion. And Pd was well dispersed in different hydrotalcite precursors. The M~(2+) ions greatly influence the activities of the serial catalysts. Among the investigated catalysts, the activity of the Pd supported Co-containing oxide was found to be much higher than the other catalysts. The light-off and complete oxidation temperatures were 182 and 283℃, respectively. H_2-TPR and O_2-TPD results show that higher reduction abilities and higher intensities of the surface oxygen active species as well as the synergetic effect between Pd and Co contribute to excellent Pd/Co_3AlO catalytic activity.