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Thermostable Rh Metal Nanoparticles Formed on Al2O3 by High-Temperature H2 Reduction and Its Impact on Three-Way Catalysis
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2019-09-26 , DOI: 10.1021/acs.jpcc.9b06657
Masato Machida 1 , Yuki Uchida , Yuri Ishikawa , Satoshi Hinokuma 1 , Hiroshi Yoshida 1 , Junya Ohyama 1 , Yuki Nagao 2 , Yoshinori Endo 2 , Katsuya Iwashina 2 , Yunosuke Nakahara 2
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2019-09-26 , DOI: 10.1021/acs.jpcc.9b06657
Masato Machida 1 , Yuki Uchida , Yuri Ishikawa , Satoshi Hinokuma 1 , Hiroshi Yoshida 1 , Junya Ohyama 1 , Yuki Nagao 2 , Yoshinori Endo 2 , Katsuya Iwashina 2 , Yunosuke Nakahara 2
Affiliation
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The influence of high-temperature H2 reduction treatment on Rh and Pd catalysts supported on Al2O3 was studied in relation to thermal aging in air. After air-aging at ≥900 °C, the Rh/Al2O3 catalyst was more strongly deactivated compared with the Pd/Al2O3 catalyst. As has been widely recognized, the solid-state reactions between Rh oxide and Al2O3 decreased the active surface area and stabilized inactive Rh3+ species. The activity was restored by the postreduction treatment with 20% H2/He at 200 °C, whereas a striking enhancement of activity was achieved by the reduction at 800–1100 °C, where substantial deactivation occurred for Pd/Al2O3. A mechanistic interpretation is proposed based on local structural characterization, which explains these contrasting thermal behaviors. The high-temperature reduction treatment produced active and thermostable Rh metal nanoparticles, which were highly dispersed on Al2O3. The observed dispersion (as high as ∼20% after reduction at 1000 °C) is among the highest for supported Rh catalysts reported in the literature. This is in complete contrast to the rapid sintering of Pd and other precious metals (Ru and Pt) into large metal agglomerates greater than 50 nm. Because the thermal behavior observed for Rh/ZrO2 under both oxidizing and reducing atmospheres was similar to that of Pd/Al2O3, the stability of metal nanoparticles depended not only on metal species but also on the interactions with support materials. An important implication of this study is that Al2O3 is a very efficient support for anchoring Rh metal nanoparticles via interfacial Rh–O–Al bonding under strong reducing conditions, in contrast to the well-known incompatibility with Rh oxide under oxidizing conditions.
中文翻译：
高温H 2还原在Al 2 O 3上形成的热稳定Rh金属纳米颗粒及其对三效催化的影响
研究了高温H 2还原处理对Al 2 O 3负载的Rh和Pd催化剂与空气中热老化的影响。后空气老化在≥900℃下中，Rh / Al的2 ö 3催化剂更强烈失活与所述的Pd / Al的比2 ö 3催化剂。众所周知，Rh氧化物和Al 2 O 3之间的固态反应降低了活性表面积并稳定了非活性Rh 3+物种。通过20％H 2的还原后处理恢复了活性/ He在200°C，而活性显着增强是通过在800–1100°C下还原而实现的，Pd / Al 2 O 3发生了明显的失活。基于局部结构特征提出了一种机械解释，解释了这些相反的热行为。高温还原处理产生活性和热稳定的Rh金属纳米颗粒，它们高度分散在Al 2 O 3上。观察到的分散度（在1000°C下还原后高达约20％）是文献报道的负载型Rh催化剂中最高的。这与将Pd和其他贵金属（Ru和Pt）快速烧结成大于50 nm的大型金属团块形成了鲜明的对比。因为在氧化和还原气氛下观察到的Rh / ZrO 2的热行为与Pd / Al 2 O 3相似，所以金属纳米颗粒的稳定性不仅取决于金属种类，还取决于与载体材料的相互作用。这项研究的重要意义是Al 2 O 3 与众所周知的在氧化条件下与Rh氧化物的不相容性相反，它是在强还原条件下通过界面Rh-O-Al键固定Rh金属纳米颗粒的非常有效的支持。
更新日期：2019-09-26
中文翻译：
高温H 2还原在Al 2 O 3上形成的热稳定Rh金属纳米颗粒及其对三效催化的影响
研究了高温H 2还原处理对Al 2 O 3负载的Rh和Pd催化剂与空气中热老化的影响。后空气老化在≥900℃下中，Rh / Al的2 ö 3催化剂更强烈失活与所述的Pd / Al的比2 ö 3催化剂。众所周知，Rh氧化物和Al 2 O 3之间的固态反应降低了活性表面积并稳定了非活性Rh 3+物种。通过20％H 2的还原后处理恢复了活性/ He在200°C，而活性显着增强是通过在800–1100°C下还原而实现的，Pd / Al 2 O 3发生了明显的失活。基于局部结构特征提出了一种机械解释，解释了这些相反的热行为。高温还原处理产生活性和热稳定的Rh金属纳米颗粒，它们高度分散在Al 2 O 3上。观察到的分散度（在1000°C下还原后高达约20％）是文献报道的负载型Rh催化剂中最高的。这与将Pd和其他贵金属（Ru和Pt）快速烧结成大于50 nm的大型金属团块形成了鲜明的对比。因为在氧化和还原气氛下观察到的Rh / ZrO 2的热行为与Pd / Al 2 O 3相似，所以金属纳米颗粒的稳定性不仅取决于金属种类，还取决于与载体材料的相互作用。这项研究的重要意义是Al 2 O 3 与众所周知的在氧化条件下与Rh氧化物的不相容性相反，它是在强还原条件下通过界面Rh-O-Al键固定Rh金属纳米颗粒的非常有效的支持。
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