Effect of water treatment and Fe doping on Pt sintering and the propane oxidation activity of Pt/Al2O3
Effect of water treatment and Fe doping on Pt sintering and the propane oxidation activity of Pt/Al2O3
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DOI：
10.1016/j.apcata.2016.04.033
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发表时间：
2016-07
影响因子：
5.5
通讯作者：
A. Tomita;T. Miki;Y. Tai
中科院分区：
文献类型：
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作者：
A. Tomita;T. Miki;Y. Tai
研究了水处理和Fe掺杂对1wt%Pt/Al_2O_3催化剂高温烧结的影响。在700℃和800℃下老化5h后，经水处理的催化剂的铂分散度高于未处理的催化剂，表明水处理抑制了铂的烧结。改善的程度取决于铁的含量。X射线衍射、PtLiI和FeKedge X射线吸收精细结构测量表明，所有老化催化剂中的铂不与Fe物种合金化，金属铂颗粒和三价铁物种存在，水处理和Fe含量对铂和铁的价态没有影响。因此，在700800℃温度范围内，低铁含量(Fe/Pt摩尔比：≈=1)的催化剂能有效地抑制铂的烧结，可能是由于氧化铝表面的铁氧化物对铂纳米颗粒起到了钉扎的作用。相反，较高的Fe含量(Fe/Pt摩尔比和≳=5)促进了铂的烧结，但降低了丙烷氧化温度。这可能是由于在氧化反应过程中促进了丙烷单键H键的解离吸附。
The effect of water treatment and Fe doping on Pt sintering at high temperature was studied for 1wt%Pt/Al2O3catalysts. After aging for 5 h at 700 and 800 °C, the water-treated catalysts had higher Pt dispersions than the corresponding untreated catalysts, indicating that Pt sintering was suppressed by water treatment. The degree of improvement depended on Fe content. X-ray diffraction and PtLIIIand FeKedge X-ray absorption fine structure measurements indicated that Pt was not alloyed with Fe species; that metallic Pt particles and trivalent Fe species existed in all of the aged catalysts; and that both water treatment and Fe content did not affect the Pt and Fe valence states. Thus, the effective suppression of Pt sintering in catalysts with low Fe content (molar ratio of Fe/Pt ≈ 1) at 700–800 °C is probably due to iron oxides on the alumina surface functioning as pinning sites for Pt nanoparticles. In contrast, high Fe contents (molar ratio of Fe/Pt ≳ 5) promoted Pt sintering, but lowered the propane oxidation temperature. This is probably due to the promotion of dissociative adsorption of the propane Csingle bondH bond during the oxidation reaction.