Reversible Restructuring of Silver Particles during Ethylene Epoxidation

被引：56

作者：

van Hoof, Arno J. F. ^{[1
]}

Filot, Ivo A. W. ^{[1
]}

Friedrich, Heiner ^{[2
]}

Hensen, Emiel J. M. ^{[1
]}

机构：

[1] Eindhoven Univ Technol, Schuit Inst Catalysis, Lab Inorgan Mat Chem, POB 513, NL-5600 MB Eindhoven, Netherlands

[2] Eindhoven Univ Technol, Lab Mat & Interface Chem, POB 513, NL-5600 MB Eindhoven, Netherlands

来源：

ACS CATALYSIS | 2018年 / 8卷 / 12期

关键词：

heterogeneous catalysis; ethylene epoxidation; silver; chlorine; restructuring; redispersion; tomography; ELECTROLYTIC SILVER; HETEROGENEOUS CATALYSIS; SHAPE CHANGES; OXIDATION; NANOPARTICLES; FORMALDEHYDE; SELECTIVITY; METHANOL; KINETICS; GOLD;

D O I：

10.1021/acscatal.8b03331

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

The restructuring of a silver catalyst during ethylene epoxidation under industrially relevant conditions was investigated without and with vinyl chloride (VC) promotion. During non-VC-promoted ethylene epoxidation, the silver particles grow and voids are formed at the surface and in the bulk. Electron tomography highlighted the presence of voids below the Ag surface. A mechanism is proposed involving reconstruction of the silver lattice and defect sites induced by oxygen adsorption on the external surface and grain boundaries, which finally create pores. Promotion of the catalytic reaction by VC suppresses to a significant extent void formation. The use of VC also redisperses silver particles, initially grown during ethylene epoxidation without VC. This process is rapid as the average size decreased from 172 to 136 nm within 2 h. These insights emphasize the dynamic nature of the silver particles during the ongoing ethylene epoxidation reaction and indicate that particle size and morphology strongly depend on reaction conditions.

引用

页码：11794 / 11800

页数：13

共 34 条

[1] VARIATION OF THE MORPHOLOGY OF SILVER SURFACES BY THERMAL AND CATALYTIC ETCHING [J].