Catalytic oxidation of propane over palladium alloyed with gold: an assessment of the chemical and intermediate species
Catalytic oxidation of propane over palladium alloyed with gold: an assessment of the chemical and intermediate species
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DOI：
10.1039/c8cy01704b
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发表时间：
2018-12-07
影响因子：
5
通讯作者：
Zhong, Chuan-Jian
中科院分区：
文献类型：
--
作者：
Kareem, Haval;Shan, Shiyao;Zhong, Chuan-Jian
了解丙烷的催化氧化对于开发不仅用于排放系统中的烃的催化氧化而且用于化学加工工业中的选择性氧化的催化剂是重要的。对于钯基催化剂，很少有人知道有关的化学或中间物种参与丙烷氧化的识别。我们在这里描述的丙烷的催化氧化的调查结果与不同组成的金（PdnAu 100-n）的负载型钯纳米合金，侧重于探测化学或中间物种的催化剂上的相关性的催化剂的组成和合金相结构。除了增强的催化活性外，还揭示了催化活性对Pd：Au组合物的强烈依赖性，在反应温度方面，在Pd：Au比为50：50时显示出最大活性。这种依赖性也反映在其对热化学处理条件的依赖性上。虽然与n类似的纳米合金的活性在氧下的热化学处理后显示出很小的变化，与n 50的纳米合金的活性< 50 and n >显示出相反的趋势。重要的是，这种催化协同作用与化学和中间物质的细微差异有关，这些化学和中间物质已经通过使用漫反射红外傅里叶变换光谱（DRIFTS）的原位测量而被鉴定为具有不同的碳纳米管组合物的催化剂。对于丙烷在Pd：Au比为50：50的高活性催化剂上的催化氧化，鉴定的主要物质包括乙酸盐和碳酸氢盐，与鉴定具有50% Au的催化剂的碳酸氢盐和甲酸盐相比显示出细微的差异（活性基本上不存在）。在Pd中合金化50%的Au被认为增加了Pd的亲氧性，这促进了第一个碳-碳键的断裂和丙烷的氧化。研究结果对钯与Au合金的催化协同作用以及活性钯合金催化剂的设计也有一定的指导意义。
Understanding the catalytic oxidation of propane is important for developing catalysts not only for catalytic oxidation of hydrocarbons in emission systems but also for selective oxidation in the chemical processing industry. For palladium-based catalysts, little is known about the identification of the chemical or intermediate species involved in propane oxidation. We describe herein findings of an investigation of the catalytic oxidation of propane over supported palladium nanoalloys with different compositions of gold (PdnAu100-n), focusing on probing the chemical or intermediate species on the catalysts in correlation with the bimetallic composition and the alloying phase structure. In addition to an enhanced catalytic activity, a strong dependence of the catalytic activity on the bimetallic composition was revealed, displaying an activity maximum at a Pd:Au ratio of 50:50 in terms of reaction temperature. This dependence is also reflected by its dependence on the thermochemical treatment conditions. While the activity for nanoalloys with n similar to 50 showed little change after the thermochemical treatment under oxygen, the activities for nanoalloys with n < 50 and n > 50 showed opposite trends. Importantly, this catalytic synergy is linked to the subtle differences of chemical and intermediate species which have been identified for the catalysts with different bimetallic compositions by in situ measurements using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). For the catalytic oxidation of propane over the highly-active catalyst with a Pd:Au ratio of 50:50, the major species identified include acetate and bicarbonate, showing subtle differences in comparison with the identification of bicarbonate and formate for the catalyst with 50% Au (activity is largely absent). The alloying of 50% Au in Pd is believed to increase the oxophilicity of Pd, which facilitates the first carbon-carbon bond cleavage and oxygenation of propane. The implications of the findings on the catalytic synergy of Pd alloyed with Au and the design of active Pd alloy catalysts are also discussed.