Pt/Si-MCM-41介孔结构对低温NO+H_2+O_2反应的影响(英文)

Influences of Mesoporous Structure on the NO+H_2+O_2 Low Temperature Reaction over Pt/Si-MCM-41 Catalyst

将Pt/Si-MCM-41用于H2选择催化还原(H2-SCR)消除NO的反应.X射线衍射分析、N2吸附/脱附、氢吸附和透射电镜等分析结果表明,介孔Si-MCM-41具有大的比表面积和孔体积有利于活性组分Pt的分散,Pt/Si-MCM-41催化剂在富氧和80000h-1空速的条件下,其H2-SCR低温活性在100℃达到60.1%,优于Pt/Si-ZSM-5和Pt/SiO2催化剂,其选择性在120℃可达70%.当Si-MCM-41的介孔结构被破坏时,H2-SCR反应活性明显下降,最大活性在120℃仅为15%.漫反射红外光谱(DRIFTS)测试表明,—NO3物种是Pt/Si-MCM-41催化剂在H2-SCR反应中的主要中间物种.

It was found that Si-MCM-41 mesoporous molecular sieves as a support of noble metal Pt could be used for the selective catalytic reduction of NO by hydrogen （H2-SCR） under lean-burn conditions. Pt/Si-MCM-41, together with Pt/Si-ZSM-5 and Pt/SiO2, was characterized by X-ray diffraction analysis （XRD）, nitrogen adsorption/desorption, hydrogen adsorption, and transmission electron microscopy （TEM）. The results indicated that Pt/Si-MCM-41 had the best H2-SCR activity in comparison with Pt/Si-ZSM-5 and Pt/SiO2 catalysts and that the maximum conversion of NO was up to 60.1% at 100 ℃ and a gas hourly space velocity （GHSV） of 80000 h^-1 under lean-burn conditions. Characterization showed that the large surface area and pore volume of MCM-41 favored the dispersion of Pt. The maximum NO conversion of Pt/Si-MCM-41 catalyst decreased obviously to 15% at 120 ℃ when the pore structure of Si-MCM-41 support was destroyed. The reaction mechanism over Pt/Si-MCM-41 was investigated using in situ diffuse reflectance infrared spectroscopy （DRIFTS）, which revealed that the main reaction intermediates should be nitrate species during NO reduction.