本体结构对复杂的基于Mo-V的氧化物催化剂表面动力学的影响,ACS Catalysis

当前位置： X-MOL 学术 › ACS Catal. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

本体结构对复杂的基于Mo-V的氧化物催化剂表面动力学的影响
ACS Catalysis ( IF 11.3 ) Pub Date : 2017-03-29 00:00:00 , DOI: 10.1021/acscatal.7b00130
Annette Trunschke ₁ , Johannes Noack _{1,

2} , Sergej Trojanov ₃ , Frank Girgsdies ₁ , Thomas Lunkenbein ₁ , Verena Pfeifer _{1,

4} , Michael Hävecker _{1,

5} , Pierre Kube ₁ , Christoph Sprung ₁ , Frank Rosowski ₆ , Robert Schlögl ₁

Affiliation

已知由四种金属Mo，V，Te和Nb组成的混合氧化物是低级烷烃选择性氧化的有效催化剂。这种混合氧化物的出色催化性能归因于所谓的M1晶相的存在，该相在结构的金属位置包含所有四个元素。在目前的工作中，通过水热合成制备了仅由Mo和V组成的M1相。通过施加200°C的合成温度可实现高结晶度。研究了纯相混合的MoV氧化物作为丙烷氧化的催化剂。与以前的报告相比，理想的氧化产物丙烯酸在无Te的M1结构上大量形成，这意味着不一定需要Te作为负责选择性氧插入的活性集合的组成部分。然而，与由四种金属Mo，V，Te和Nb组成的M1结构相比，MoV M1氧化物的选择性较低。通过结合基于同步加速器的单晶结构分析和近环境压力X射线光电子能谱确定了原因。对MoV M1氧化物的晶体结构的测定表明，V对M1结构的六边形通道中的位点有部分占据，而这些位点在MoVTeNb M1氧化物中被Te占据。在反应条件下MO键（M = V，Te）的水解导致六角形通道中的金属迁移到表面。⁵⁺种，因此具有很高的选择性。

"点击查看英文标题和摘要"

The Impact of the Bulk Structure on Surface Dynamics of Complex Mo–V-based Oxide Catalysts

Mixed oxides composed of the four metals Mo, V, Te, and Nb are known to be efficient catalysts in selective oxidation of lower alkanes. The outstanding catalytic performance of such mixed oxides is attributed to the presence of the so-called M1 crystal phase that contains all four elements in the metal positions of the structure. In the present work, an M1 phase composed only of Mo and V has been prepared by hydrothermal synthesis. High crystallinity was achieved by applying a synthesis temperature of 200 °C. The phase-pure mixed MoV oxide was studied as catalyst in the oxidation of propane. In contrast to previous reports, the desirable oxidation product acrylic acid is formed over the Te-free M1 structure in significant amounts, implying that Te is not necessarily required as a component of the active ensemble responsible for selective oxygen insertion. The MoV M1 oxide is, however, less selective compared to that of the M1 structure composed of the four metals Mo, V, Te, and Nb. The reason has been determined by applying a combination of synchrotron-based single crystal structure analysis and near-ambient-pressure X-ray photoelectron spectroscopy. Determination of the crystal structure of MoV M1 oxide reveals partial occupation of sites in the hexagonal channels of the M1 structure by V, which are occupied by Te in MoVTeNb M1 oxide. Hydrolysis of the M-O bonds (M = V, Te) under reaction conditions leads to migration of the metal in the hexagonal channels to the surface. Accumulation of more than 50 at % V on the surface of the MoV M1 oxide most likely causes postcombustion of formed acrylic acid, whereas enrichment of Te at the surface of MoVTeNb M1 oxide results in dilution of surface V⁵⁺ species and, consequently, high selectivity.

更新日期：2017-03-29

点击分享查看原文

点击收藏

公开下载

阅读更多本刊新发论文本刊介绍/投稿指南