In situ X-ray absorption spectroscopic study on the reducibility of cobalt-containing aluminophosphate molecular sieves

Real-time X-ray absorption spectra (XAS) during the course of temperature-programmed reduction (TPR) were recorded to investigate the reducibility of cobalt on aluminophosphate molecular sieve AIPO-5. When incorporated into the AIPO-5 framework via hydrothermal synthesis, cobalt exhibited high resistance to reduction by hydrogen. In contrast, cobalt could be fully reduced in the temperature range between 400 and 500 degreesC when supported on the surface of AIPO-5. The coordination number (NCo-Co) for the first shell was 8.5 on the reduced catalyst with a cobalt loading of 5 wt.%, corresponding to an average particle size of 35 Angstrom. (C) 2003 Elsevier Science B.V. All rights reserved.