Catalytic oxidation of chlorobenzene over Pd/perovskites
Catalytic oxidation of chlorobenzene over Pd/perovskites
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DOI：
10.1016/j.apcatb.2008.04.023
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发表时间：
2008-10-25
影响因子：
22.1
通讯作者：
Leclercq, G.
中科院分区：
文献类型：
--
作者：
Giraudon, J. -M.;Elhachimi, A.;Leclercq, G.
研究了预还原钯/镧系钙钛矿LaBO 3（B = CO，Mn，Fe，Ni）催化剂对氯苯（PhCl; 1000 ppmv）的催化氧化性能。使用湿浸渍技术制备催化剂，并使用硝酸钯作为钯前体。将催化性能与负载在常规载体即γ-Al 2 O3上的参比钯催化剂的催化性能进行比较。发现氯苯破坏的容易性遵循基于T-50值（50%的氯苯转化为产物的温度）的顺序：Pd/LaMnO 3 + δ（243摄氏度）> Pd/LaFeO 3（270摄氏度）> Pd/Al 2 O 3（348摄氏度）> Pd/LaCoO 3（360摄氏度）> Pd/LaNiO 3（408摄氏度）。氯苯的完全转化达到约。320-500摄氏度，但在这些温度下会形成大量的多氯苯。准原位XPS研究在Pd/LaCoO 3和Pd/LaFeO 3上在全局过程的每个阶段之后进行监测，即在煅烧、还原和暴露于从室温到230和310摄氏度（Pd/LaFeO 3）以及到280摄氏度（Pd/LaCoO 3）的流动反应混合物（在空气中的1000 ppmv PhCl）之后。结果表明，煅烧处理导致钯的BE高于PdO的BE，并且（B/La）（xps）< 1，这证明XPS表面富集了镧。在H-2处理后，表明钯被完全还原，而B阳离子是未还原的（Fe 3+）或还原的（Co 3+变成Co 2+和Co 0）。在反应气氛中，Pd-0逐渐（氧）氯化，而钙钛矿网络重建与生产LaOCl和Co 3 O 4。预还原的Pd/LaBO 3比单独的钙钛矿对PhCl转化更有活性，但显著提高了PhCl的氯化速率。在不同的催化剂Pd/LaFeO 3之间的PhCl氧化和氯化速率表现出最好的折衷。(C)2008 Elsevier B. V.保留所有权利。
The catalytic performances of pre-reduced palladium catalysts supported on lanthanum based perovskites LaBO3 (B = CO, Mn, Fe, Ni) were investigated for the total oxidation of chlorobenzene (PhCl; 1000 ppmv) in air. The catalysts were prepared using a wet impregnation technique and Pd-nitrate was used as a palladium precursor. The catalytic performances were compared to those of a reference palladium catalyst supported on a conventional support, namely gamma-Al2O3. Easiness of chlorobenzene destruction was found to follow the sequence based on the T-50 values (temperature at which 50% of chlorobenzene was converted into products): Pd/LaMnO3+delta (243 degrees C) > Pd/LaFeO3 (270 degrees C) > Pd/Al2O3 (348 degrees C) > Pd/LaCoO3 (360 degrees C) > Pd/LaNiO3 (408 degrees C). Complete conversion of chlorobenzene is reached at ca. 320-500 degrees C, but at those temperatures substantial amounts of polychlorinated benzenes are formed. Quasi in situ XPS studies were monitored on Pd/LaCoO3 and Pd/LaFeO3 after each stage of the global process, namely after calcination, reduction and exposure to the flowing reactive mixture (1000 ppmv PhCl in air) from room temperature to 230 and 310 degrees C (Pd/LaFeO3) and to 280 degrees C (Pd/LaCoO3). It Was shown that the calcination treatment leads to a palladium which a BE higher than that of PdO and to a (B/La)(xps) < 1 which attests of a lanthanum enrichment at the XPS surface. After H-2 treatment it was shown that palladium is totally reduced while the B cation is either unreduced (Fe3+) or reduced (Co3+ into Co2+ and Coo). In the reactive atmosphere, Pd-0 is progressively (oxi)chlorined while the perovskite network is reconstructed with productions of LaOCl and Co3O4. The pre-reduced Pd/LaBO3 are more active than the perovskite alone for PhCl transformation but substantially increase the chlorination rate of PhCl. Among the different catalysts Pd/LaFeO3 shows the best compromise between PhCl oxidation and chlorination rates. (C) 2008 Elsevier B.V. All rights reserved.