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Influence of the calcination temperature on the activity of hydroxyapatite-supported palladium catalyst in the methane oxidation reaction
Applied Catalysis B: Environment and Energy ( IF 22.1 ) Pub Date : 2020-06-26 , DOI: 10.1016/j.apcatb.2020.119280
Zouhair Boukha , Andoni Choya , Marina Cortés-Reyes , Beatriz de Rivas , Luis J. Alemany , Juan R. González-Velasco , José I. Gutiérrez-Ortiz , Rubén López-Fonseca

In the present study, a series of four hydroxyapatite (HAP) supported palladium samples, with a Pd loading close to 0.5%, obtained through their calcination at 773, 873, 973, or 1073 K has been investigated. These samples have been characterized using a wide battery of complementary techniques. From these studies, it was found that the rise of the calcination temperature induces a progressive dehydroxylation of the support and a structure evolution of the species containing Pd2+, from tetrahedral (Td) to square planar geometry (D4h). Moreover, this enhances markedly the metal-support interactions. For instance, at the highest temperature (1073 K), Pd particles were found encapsulated by a thin support layer. Consequently, two distinct reducible species have been identified; one of them manifests SMSI. This increase in the Pd-HAP interaction strength seems to (i) expand the HAP lattice, (ii) change the Pd2+ coordination from Td to D4h geometry, (iii) promote PdO reduction and (iv) suppress CO chemisorption. These entire properties do compensate the poor textural properties and benefit the efficiency and stability of the Pd active phase in methane oxidation reaction.



中文翻译:

煅烧温度对羟基磷灰石负载钯催化剂甲烷氧化反应活性的影响

在本研究中,已经研究了通过在773、873、973或1073 K下煅烧获得的一系列四个载有羟基磷灰石(HAP)的钯样品,钯含量接近0.5%。这些样品已使用各种互补技术进行了表征。从这些研究中发现,煅烧温度的升高诱导了载体的逐步脱羟基作用以及含Pd 2+的物质的结构演变,从四面体(Td)变为方形平面几何形状(D 4h)。此外,这显着增强了金属与载体的相互作用。例如,在最高温度(1073 K)下,发现Pd颗粒被薄的支撑层包裹。因此,已经确定了两个不同的可还原物种;其中之一体现了SMSI。Pd-HAP相互作用强度的这种增加似乎(i)扩展了HAP晶格,(ii)将Pd 2+配位从Td改变为D 4h几何形状,(iii)促进了PdO的还原并(iv)抑制了CO化学吸附。这些全部性能确实弥补了不良的结构性能,并有利于甲烷氧化反应中Pd活性相的效率和稳定性。

更新日期:2020-06-26
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