In situ structure‐function studies of oxide supported rhodium catalysts by combined energy dispersive XAFS and DRIFTS spectroscopies

DOI: 10.1063/1.2644606

Authors: John Evans (University of Southampton; Diamond Light Source) , Andrew J. Dent (Diamond Light Source Ltd) , Sofia Diaz-Moreno (Diamond Light Source) , Steven G. Fiddy (CCLRC Daresbury Laboratory) , Bhrat Jyoti (University of Southampton) , Mark A. Newton (ESRF) , Moniek Tromp (University of Southampton)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: X-ray Absorption Fine Structure - XAFS 13
Peer Reviewed: No

State: Published (Approved)
Published: February 2007

Abstract: The techniques of energy dispersive EXAFS (EDE), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and mass spectrometry (MS) have been combined to study the structure and function of an oxide supported metal catalyst, namely 5 wt% Rh/Al2O3. Using a FreLoN camera as the EDE detector and a rapid‐scanning IR spectrometer, experiments could be performed with a repetition rate of 50 ms. The results show that the nature of the rhodium centers is a function of the partial pressures of the reacting gases (CO and NO) and also temperature. This combination of gases oxidizes metallic rhodium particles to Rh(CO)2 at room temperature. The proportion of the rhodium adopting this site increases as the temperature is raised (up to 450 K). Above that temperature the dicarbonyl decomposes and the metal reclusters. Once this condition is met, catalysis ensues. Gas switching techniques show that at 573 K with NO in excess, the clusters can be oxidized rapidly to afford a linear nitrosyl complex; re‐exposure to CO also promotes reclustering and the CO adopts terminal (atop) and bridging (2‐fold) sites.

Journal Keywords: Absorption Spectroscopy; Aluminium Oxides; Carbon Monoxide; Catalysis; Fine Structure; Fourier Transform Spectrometers; Fourier Transformation; Gases; Infrared Spectra; Interfaces; Mass Spectroscopy; Nitric Oxide; Oxidation; Partial Pressure; Rhodium

Subject Areas: Chemistry, Technique Development

Facility: ID24 at ESRF

Added On: 26/08/2010 08:09

Discipline Tags:

Physical Chemistry Technique Development - Chemistry Catalysis Chemistry

Technical Tags: