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Comprehensive Study on Ni- or Ir-Based Alloy Catalysts in the Hydrogenation of Olefins and Mechanistic Insight
ACS Catalysis ( IF 11.3 ) Pub Date : 2021-03-01 , DOI: 10.1021/acscatal.0c04615 Jia-qi Bai 1 , Masazumi Tamura 2 , Akira Nakayama 3 , Yoshinao Nakagawa 1 , Keiichi Tomishige 1
ACS Catalysis ( IF 11.3 ) Pub Date : 2021-03-01 , DOI: 10.1021/acscatal.0c04615 Jia-qi Bai 1 , Masazumi Tamura 2 , Akira Nakayama 3 , Yoshinao Nakagawa 1 , Keiichi Tomishige 1
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Metal-alloyed atomic catalysts such as single-atom alloys have attracted much attention due to their high atom economy and their unique catalytic properties. Recently, we found that a SiO2-supported Ni-Ir alloy (Ni-Ir/SiO2) was an effective heterogeneous catalyst for the hydrogenation of styrene and that the isolated Ni atom surrounded by Ir metal atoms, an Ir-alloyed Ni single atom, in the Ni-Ir alloy was the main active site, showing much higher activity in comparison with the monometallic Ir/SiO2 and Ni/SiO2. Reports on such effective metal-alloyed non-noble-metal single-atom catalysts are limited, and their catalytic potential should be clarified. In this study, bimetallic catalysts composed of non-noble metals and noble metals were comprehensively scrutinized in the hydrogenation of styrene as a model reaction. Among various combinations, Ni-Ir/SiO2 (introduced Ni/Ir molar ratio 1) showed the largest rate enhancement (7-fold) in comparison with the monometallic counterpart catalysts, while a SiO2-supported Co-Ir alloy (Co-Ir/SiO2, introduced Co/Ir molar ratio 4) and Ni-Pt alloy (Ni-Pt/SiO2, introduced Ni/Pt molar ratio 0.25) were also effective. The activity orders were Co-Ir/SiO2 > Ir/SiO2 > Co/SiO2 and Ni-Pt/SiO2 > Pt/SiO2 > Ni/SiO2, and the (Co-Ir/SiO2)/(Ir/SiO2) and (Ni-Pt/SiO2)/(Pt/SiO2) activity ratios were 3.5 and 2.5, respectively. Moreover, Ni-Ir/SiO2 showed higher activity for the hydrogenation of various olefins in comparison to the monometallic Ir/SiO2 and Ni/SiO2. The reaction mechanism of styrene hydrogenation over the Ir-alloyed Ni single atom of Ni-Ir/SiO2 was proposed on the basis of spectroscopic studies such as FTIR, XPS, and XRD, kinetic studies such as the effect of substrate concentration and H2 pressure, the isotopic effect of hydrogen, and the effect of the reaction temperature, and DFT calculations. The rate-determining step is the second hydrogenation of the half-hydrogenated styrene adspecies on an Ni atom by H species on Ir atoms in the Horiuti–Polanyi mechanism. The single Ni atom in Ir metal atoms has two roles: (1) formation of the reactive half-hydrogenated styrene adspecies on Ni atom and (2) formation of the reactive H species on Ir atoms by the electron transfer from an Ni atom to Ir atoms. These roles resulted in a low activation energy, leading to a large rate enhancement in comparison to the monometallic counterpart catalysts.
中文翻译：
镍或铱基合金在烯烃加氢中的综合研究及机理研究
金属合金原子催化剂，例如单原子合金，由于其高原子经济性和独特的催化性能而备受关注。最近，我们发现SiO 2负载的Ni-Ir合金（Ni-Ir / SiO 2）是一种有效的苯乙烯加氢多相催化剂，并且分离出的Ni原子被Ir金属原子包围，即Ir合金化的Ni单原子。 Ni-Ir合金中的原子是主要的活性位点，与单金属Ir / SiO 2和Ni / SiO 2相比，活性更高。这种有效的金属合金化非贵金属单原子催化剂的报道有限，应阐明其催化潜力。在这项研究中，由非贵金属和贵金属组成的双金属催化剂在苯乙烯加氢中作为模型反应得到了全面的研究。在各种组合中，与单金属配对催化剂相比，Ni-Ir / SiO 2（引入的Ni / Ir摩尔比1）显示出最大的速率增强（7倍），而SiO 2负载的Co-Ir合金（Co- Ir / SiO 2，引入的Co / Ir摩尔比4）和Ni-Pt合金（Ni-Pt / SiO 2，引入的Ni / Pt摩尔比0.25）也是有效的。活性顺序为Co-Ir / SiO 2 > Ir / SiO 2> Co / SiO 2和Ni-Pt / SiO 2 > Pt / SiO 2 > Ni / SiO 2以及（Co-Ir / SiO 2）/（Ir / SiO 2）和（Ni-Pt / SiO 2）/ （Pt / SiO 2）活性比分别为3.5和2.5。而且，与单金属Ir / SiO 2和Ni / SiO 2相比，Ni-Ir / SiO 2对各种烯烃的氢化具有更高的活性。Ni-Ir / SiO 2的Ir合金Ni单原子上苯乙烯加氢的反应机理在诸如FTIR，XPS和XRD等光谱研究，动力学研究（例如底物浓度和H 2压力的影响，氢的同位素效应，反应温度的影响以及DFT计算）的基础上提出了SnO。决定速率的步骤是在Horiuti-Polanyi机理中，通过Ir原子上的H物种对Ni原子上的半氢化苯乙烯类分子进行第二次氢化。Ir金属原子中的单个Ni原子具有两个作用：（1）在Ni原子上形成反应性半氢化苯乙烯基；（2）通过从Ni原子到Ir的电子转移，在Ir原子上形成反应性H物种。原子。这些作用导致活化能低，与单金属对应催化剂相比，导致速率大大提高。
更新日期：2021-03-19
中文翻译：
镍或铱基合金在烯烃加氢中的综合研究及机理研究
金属合金原子催化剂，例如单原子合金，由于其高原子经济性和独特的催化性能而备受关注。最近，我们发现SiO 2负载的Ni-Ir合金（Ni-Ir / SiO 2）是一种有效的苯乙烯加氢多相催化剂，并且分离出的Ni原子被Ir金属原子包围，即Ir合金化的Ni单原子。 Ni-Ir合金中的原子是主要的活性位点，与单金属Ir / SiO 2和Ni / SiO 2相比，活性更高。这种有效的金属合金化非贵金属单原子催化剂的报道有限，应阐明其催化潜力。在这项研究中，由非贵金属和贵金属组成的双金属催化剂在苯乙烯加氢中作为模型反应得到了全面的研究。在各种组合中，与单金属配对催化剂相比，Ni-Ir / SiO 2（引入的Ni / Ir摩尔比1）显示出最大的速率增强（7倍），而SiO 2负载的Co-Ir合金（Co- Ir / SiO 2，引入的Co / Ir摩尔比4）和Ni-Pt合金（Ni-Pt / SiO 2，引入的Ni / Pt摩尔比0.25）也是有效的。活性顺序为Co-Ir / SiO 2 > Ir / SiO 2> Co / SiO 2和Ni-Pt / SiO 2 > Pt / SiO 2 > Ni / SiO 2以及（Co-Ir / SiO 2）/（Ir / SiO 2）和（Ni-Pt / SiO 2）/ （Pt / SiO 2）活性比分别为3.5和2.5。而且，与单金属Ir / SiO 2和Ni / SiO 2相比，Ni-Ir / SiO 2对各种烯烃的氢化具有更高的活性。Ni-Ir / SiO 2的Ir合金Ni单原子上苯乙烯加氢的反应机理在诸如FTIR，XPS和XRD等光谱研究，动力学研究（例如底物浓度和H 2压力的影响，氢的同位素效应，反应温度的影响以及DFT计算）的基础上提出了SnO。决定速率的步骤是在Horiuti-Polanyi机理中，通过Ir原子上的H物种对Ni原子上的半氢化苯乙烯类分子进行第二次氢化。Ir金属原子中的单个Ni原子具有两个作用：（1）在Ni原子上形成反应性半氢化苯乙烯基；（2）通过从Ni原子到Ir的电子转移，在Ir原子上形成反应性H物种。原子。这些作用导致活化能低，与单金属对应催化剂相比，导致速率大大提高。
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