Cu-Mg/Al复合氧化物催化碳颗粒物燃烧性能的研究

恒定二价与三价阳离子比为3(nM2+/nM3+=3),采用共沉淀法制备不同Cu含量的系列水滑石前驱物, 800 ℃焙烧4 h形成复合氧化物(CuO质量百分数分别为0％、5％、10％、15％、20％、30％、40％)用作柴油车排放碳颗粒物燃烧的催化剂,并采用XRD、BET、TG-DSC、FT-IR、TPR等表征手段研究了Cu、Mg含量对材料前驱物物化性能的影响及对其衍生复合氧化物催化碳颗粒物燃烧性能的影响．结果表明,Cu、Mg含量对材料的热稳定性、比表面和催化氧化活性有显著的影响. Mg有助于提高催化剂的热稳定性; Cu含量增加,催化剂比表面下降,但比表面不是影响催化剂活性的主要因素. CuO含量为15％时,催化剂具有最好的催化活性和稳定性,碳颗粒物的起燃温度(T10)和半转化温度(T50)分别为336 ℃和409 ℃.在CuO含量≤30％时可以形成结构完整的水滑石前驱物, CuO含量为40％时出现Cu(OH)2杂相; CuO含量< 20％时,经高温焙烧可得到均匀的复合氧化物, CuO含量≥20％时出现CuO偏析． TPR结果表明焙烧温度和复合氧化物的组成决定了材料的可还原性能．

Catalytic Combustion of Soot over Cu-Mg/Al Composite Oxides

Keeping the atomic ratio of nM2+/nM3+ at 3, series of CuMgAl-O oxides (wCuO=0％, 5％, 10％, 15％, 20％, 30％, 40％,denoted as (0, 5, 10, 15, 20, 30, 40)CMAO respectively) were derived from calcination of Cu substituted Mg/Al-mixed anionic clay precursors(CuMgAl-hydrotalites, CMA-HTs), which were synthesized by co-precipitation methods. XRD, TG-DSC, TPR and FT-IR were used to study the influences of the Cu, Mg content upon the properties of precursors and prepared catalysts. Mg could improve thermal stability of catalysts in some degree. With the increase of Cu content, the surface area of catalysts decreased. However, the surface area was not an important factor in soot catalytic combustion. Activity tests showed the calcination affected the activity of CMAO catalysts significantly, and that 15CMAO-800 was the optimal catalyst for soot catalytic combustion and the T10 and T50 were 336 ℃ and 409 ℃ respectively. Moreover, complete structures of hydrotalcite precursors could be formed when wCuO≤30％. However, Cu(OH)2 phase appeared when wCuO =40％. When wCuO < 20％, homogeneous composite oxides could be obtained by calcination at 800 ℃, but CuO phase was isolated when wCuO≥20％. TG-DTA and FT-IR showed that the content of Cu, Mg had significant influences on the thermal decomposition characteristics of CuMgAl-hydrotalcites. TPR results showed that the reduction ability of catalysts was determined by the calcination and composition.