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首页> 外文期刊>Catalysis science & technology >Supercritical flow synthesis of PtPdFe alloyed nanoparticles with enhanced low-temperature activity and thermal stability for propene oxidation under lean exhaust gas conditions
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Supercritical flow synthesis of PtPdFe alloyed nanoparticles with enhanced low-temperature activity and thermal stability for propene oxidation under lean exhaust gas conditions

机译：超临界流PtPdFe合金的合成纳米粒子与增强低温丙烯的活性和热稳定性在精益排气条件下氧化

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摘要

Supercritical flow technology was used for the one step production of PtPd and PtPdFe nanoparticles supported on high surface area gamma-Al2O3. Fe addition to PtPd nanoparticles enhanced the propene oxidation activity of the fresh catalysts. For instance, the turnover frequency of a catalyst with 0.12 wt% Fe was 0.06 s(-1) at 120 degrees C, three times higher than the analogous PtPd catalyst. Fe was also incorporated as a substitute element for the PtPd precious metal content ((PtPd)(x-y)Fe-y, x = 0.75 wt% and y = 0-0.25 wt%), and a relationship between the activity for propene oxidation and the ratio of Fe to PtPd was found. The optimum ratio in terms of activity was found for the (PtPd)(0.65)Fe-0.10/gamma-Al2O3 catalyst, allowing precious metal savings of 19% when compared to the PtPd/gamma-Al2O3 commercial reference catalyst. Additionally, the T50 (temperature of half conversion) for propene oxidation was lowered by 10 degrees C under fresh conditions and 20 degrees C, after hydrothermal aging (750 degrees C/3h, 10% O-2, 10% H2O). Synchrotron X-ray powder diffraction showed that Fe incorporation causes contraction of the PtPd lattice, implying that the PtPdFe alloy formation is responsible for the improved propene oxidation activity. Even after aging, the lattice remained contracted suggesting that the alloyed nanoparticles are stable under the harsh operating conditions of catalytic converters. The lattice contraction effect can be associated with the propene oxidation kinetics, leading to a weaker binding of oxygen on the PtPdFe nanoparticle surface, which can induce a higher surface reaction rate.
机译：超临界流体技术是用于一个一步PtPd和PtPdFe纳米颗粒的生产支持高表面积gamma-Al2O3。除了PtPd纳米颗粒增强的丙烯氧化活性的新鲜催化剂。0.12 wt %铁催化剂的0.06秒(1)高于120摄氏度,三次类似PtPd催化剂。替代元素的PtPd珍贵金属含量((PtPd) (x - y) Fe-y x = 0.75 wt %y = 0 - 0.25 wt %),以及之间的关系活动为丙烯氧化和的比值菲PtPd被发现。活动被发现的(PtPd) (0.65) fe - 0.10 / gamma-Al2O3催化剂,允许贵金属储蓄的19%相比PtPd / gamma-Al2O3商业参考催化剂。对丙烯(温度的转换)氧化降低10摄氏度下新鲜条件和20摄氏度,在热液老化(750摄氏度/ 3 h, 0 2 10%,水10%)。同步加速器x射线粉末衍射显示铁公司PtPd引起收缩格,这意味着PtPdFe合金的形成负责提高丙烯氧化活动。这表明合金的收缩纳米粒子稳定下的严厉催化转换器的操作条件。可以关联到晶格收缩的影响丙烯氧化动力学,导致弱PtPdFe绑定的氧气纳米颗粒的表面,可以诱导更高表面反应速率。

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