Stability of Colloidal Iron Oxide Nanoparticles on Titania and Silica Support

被引：9

作者：

Krans, Nynke A. ^{[1
]}

van Uunen, Donal L. ^{[1
]}

Versluis, Caroline ^{[1
]}

Dugulan, Achim Iulian ^{[2
]}

Chai, Jiachun ^{[3
]}

Hofmann, Jan P. ^{[3
]}

Hensen, Emiel J. M. ^{[3
]}

Zecevic, Jovana ^{[1
]}

de Jong, Krijn P. ^{[1
]}

机构：

[1] Univ Utrecht, Debye Inst Nanomat Sci, Inorgan Chem & Catalysis, NL-3584 CG Utrecht, Netherlands

[2] Delft Univ Technol, Fundamental Aspects Mat & Energy Grp, NL-2629 JB Delft, Netherlands

[3] Eindhoven Univ Technol, Dept Chem Engn & Chem, Inorgan Mat & Catalysis, NL-5600 MB Eindhoven, Netherlands

来源：

CHEMISTRY OF MATERIALS | 2020年 / 32卷 / 12期

基金：

欧洲研究理事会;

关键词：

FISCHER-TROPSCH SYNTHESIS; PARTICLE-SIZE; LOWER OLEFINS; SYNTHESIS GAS; CATALYSTS; MOSSBAUER; COBALT; REDUCTION; ALUMINA; SURFACE;

D O I：

10.1021/acs.chemmater.0c01352

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：

Using model catalysts with well-defined particle sizes and morphologies to elucidate questions regarding catalytic activity and stability has gained more interest, particularly utilizing colloidally prepared metal(oxide) particles. Here, colloidally synthesized iron oxide nanoparticles (FexOy-NPs, size similar to 7 nm) on either a titania (FexOy/TiO2) or a silica (FexOy/SiO2) support were studied. These model catalyst systems showed excellent activity in the Fischer- Tropsch to olefin (FTO) reaction at high pressure. However, the FexOy/TiO2 catalyst deactivated more than the FexOy/SiO2 catalyst. After analyzing the used catalysts, it was evident that the FexOy-NP on titania had grown to 48 nm, while the FexOy-NIP on silica was still 7 nm in size. STEM-EDX revealed that the growth of FexOy/TiO2 originated mainly from the hydrogen reduction step and only to a limited extent from catalysis. Quantitative STEM-EDX measurements indicated that at a reduction temperature of 350 degrees C, 80% of the initial iron had dispersed over and into the titania as iron species below imaging resolution. The Fe/Ti surface atomic ratios from XPS measurements indicated that the iron particles first spread over the support after a reduction temperature of 300 degrees C followed by iron oxide particle growth at 350 degrees C. Mossbauer spectroscopy showed that 70% of iron was present as Fe2+, specifically as amorphous iron titanates (FeTiO3), after reduction at 350 degrees C. The growth of iron nanoparticles on titania is hypothesized as an Ostwald ripening process where Fe2+ species diffuse over and through the titania support. Presynthesized nanoparticles on SiO2 displayed structural stability, as only similar to 10% iron silicates were formed and particles kept the same size during in situ reduction, carburization, and FTO catalysis.

引用

页码：5226 / 5235

页数：10