Stabilizing effect of Nd2O3, La2O3 and ZrO2 on Pt·PdO/Al2O3 during catalytic combustion of methane
Stabilizing effect of Nd2O3, La2O3 and ZrO2 on Pt·PdO/Al2O3 during catalytic combustion of methane
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DOI：
10.1016/j.apcata.2003.09.035
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发表时间：
2004-02
影响因子：
5.5
通讯作者：
Y. Ozawa;Y. Tochihara;Ayako Watanabe;M. Nagai;S. Omi
中科院分区：
文献类型：
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作者：
Y. Ozawa;Y. Tochihara;Ayako Watanabe;M. Nagai;S. Omi
在常压固定床流动反应装置上，研究了催化剂PdO/Al(Sub2)O(Sub3)催化剂中La、NdO和ZrO2的添加对催化剂1073K燃烧时催化剂耐久性的影响。用CO化学吸附、X-射线光电子能谱(XPS)、甲烷吸附后的TPD和X射线光电子能谱(XPS)对催化剂的表面性质进行了表征。催化剂的失活是由于PdO向Pd-Pt的转化和PdO和Pd-Pt颗粒的长大，而不是由于载体比表面积的减小、活性物种的挥发和碳的沉积。添加La{sub2}O{sub3}、Nd{sub2}O{sub3}和ZrO{sub2}降低了TPD中PdO/Al{sub2}O{sub2}的脱附温度。这防止了PdO和Pd-Pt颗粒在燃烧过程中的生长。TPD后的XPS分析表明，在PtPdO/ZrO2催化剂中同时加入Lasub2}Osub3}和Ndsub2}Osub3}后，表面Pd的价态保持在比其他催化剂高1100K。La{SUB 2}O{SUB 3}{CENTER DOT}Nd{SUB 2}O{SUB 3}-Pt{CENTER_DOT}PdO/ZRO{SUB 2}{CENTER DOT}Al{SUB 2}O{SUB 3}催化剂的寿命依赖于PdO和Pd-铂颗粒的生长，而不是PdO向Pd-Pt的转变。因此，La{sub2}O{SUB3}{CENTER_DOT}Nd{SUB2}O{SUB3}掺杂的PdO/ZrO{SUB2}{CENTER_DOT}Al{SUB2}O{SUB3}催化剂的寿命明显高于其他催化剂。
The additive effects of lanthanum oxides, neodymium oxides and zirconia in Pt{center_dot}PdO/Al{sub 2}O{sub 3} on the catalyst durability during CH{sub 4} combustion at 1073K were studied using a fixed-bed flow reactor at atmospheric pressure. The surface properties of the catalysts were investigated using CO chemisorption, XRD, TPD after CH{sub 4} adsorption, and X-ray photoelectron spectroscopy (XPS). The catalysts were deactivated by the transformation of PdO to Pd-Pt and by the growth of PdO and Pd-Pt particles rather than by the decrease in the surface area of the supports, volatilization of the active species and carbon deposition. The addition of La{sub 2}O{sub 3}, Nd{sub 2}O{sub 3} and ZrO{sub 2} to Pt{center_dot}PdO/Al{sub 2}O{sub 3} lowered the temperature of O{sub 2} desorption from bulk PdO in TPD. This prevented the growth of PdO and Pd-Pt particles during the combustion. The XPS analysis after TPD indicated that the addition of both La{sub 2}O{sub 3} and Nd{sub 2}O{sub 3} to Pt{center_dot}PdO/ZrO{sub 2}{center_dot}Al{sub 2}O{sub 3} kept the valence of the surface Pd at 1100K higher than of the other catalysts. The lifetime of the La{sub 2}O{sub 3}{center_dot}Nd{sub 2}O{sub 3}-Pt{center_dot}PdO/ZrO{sub 2}{center_dot}Al{sub 2}O{sub 3} catalyst depended on the particle growth of PdO and Pd-Pt more strongly than on the transformation of PdO to Pd-Pt. Consequently, the La{sub 2}O{sub 3}{center_dot}Nd{sub 2}O{sub 3}-doped Pt{center_dot}PdO/ZrO{sub 2}{center_dot}Al{sub 2}O{sub 3} catalyst showed a significantly longer lifetime than the other catalysts.