封装型Pd@S-1催化剂中Pd状态对低浓度甲烷催化氧化性能的影响

The effect of Pd state of encapsulated Pd@S-1 catalyst on the catalytic oxidation performance of low concentration methane

在甲烷催化燃烧反应中,封装型Pd@S-1催化剂表现出高活性和高稳定性,活性组分Pd的状态是影响其活性的重要因素.本文通过乙二胺辅助原位封装法合成Pd@S-1催化剂,通过调节催化剂后处理温度和气氛调控Pd状态,探究其对甲烷催化燃烧反应的影响.性能评价结果表明,相比空气焙烧后处理方式,氢气还原的Pd@S-1-H_(2)催化剂表现出更高的活性,其甲烷完全转换温度(T_(100))为390℃.催化剂表征结果表明活性的提高主要归因于H_(2)还原可降低Pd颗粒尺寸、增加活性Pd物种和活性氧物种.此外,水蒸气影响实验结果表明Pd@S-1-H_(2)催化剂表现出优异的抗水性.因此,采用氢气还原处理不仅能够提高Pd@S-1催化剂的甲烷催化氧化活性,同时能够有效抑制其发生水中毒.

Pd catalyst encapsulated in S-1 zeolite(Pd@S-1)exhibits high activity and stability in methane combustion,and the state of Pd is one of the important factors affecting the catalytic performance of Pd@S-1.In this paper,Pd@S-1 catalyst was synthesized by an ethylenediamine-assisted in-situ encapsulation method,and the effect of Pd state on methane combustion was investigated by adjusting the atmosphere for catalyst post-treatment.Catalytic performance evaluation showed that Pd@S-1-H_(2)(i.e.Pd@S-1 pretreated in H_(2))catalyst exhibited higher activity with a full conversion temperature(T_(100))of 390℃by simply switching from conventional calcination(in air)to H_(2) reduction.Catalyst characterization showed that the improved catalytic activity of Pd@S-1-H_(2) was mainly attributed to the decreasing of Pd particle size(by H_(2) reduction)leading to an increased density of active Pd species,as well as the increasing of reactive oxygen species.In addition,the Pd@S-1-H_(2) catalyst possessed excellent water resistance,whereas the Pd@S-1-Air catalyst(i.e.Pd@S-1 calcined in air)was seriously deactivated in the presence of water.