Thermo-programmed reduction

As already discussed, the size, the shape and the dispersion are characteristic parameters of metal particles and will determine their properties. It is possible to characterize them as follows (i) The size of the metal particles (transmission electron microscopy, (TEM) [79-81], extended X-ray absorption fine structure (EXAFS) [82, 83]), (ii) their structures (X-ray diffraction (XRD), TEM), (iii) their chemical composition (TEM-EDX, elemental analysis), (iv) the chemical state of the surface and bulk metal atoms (X-ray photoelectron spectroscopy (XPS)), Mossbauer [84], thermo-programmed-reduction (TPR)), (v) chemisorption capacity toward probe molecules such as H2, O2, NO and CO (volumetric or dynamic measurements) [85-90]. 

Temperature Programmed Reduction and Thermo-Magnetic Analysis. The results of temperature programmed reduction experiments performed on a catalyst prepared by incipient wetness impregnation and the physical mixture are presented in Fig. 1. 

The cobalt content was determined by atomic absorption at the service central d analyse du CNRS (Vemaison, France). Differential thermal and thermo gravimetric analyses (DTA/TG) were conducted in flowing air (75 mL min ) at a heating rate of 5°C min . Surface area analysis was performed using the BET method. N2 was selected as the adsorbent, and analysis was performed at liquid nitrogen temperature (-196 C). X-ray diffraction (XRD) measurements were made at room temperature (X =1.5418 A). The diffraction patterns have been indexed by comparison with the Joint Committee on Powder Diffraction Standards (JCPDS) files. Temperature Programmed Reduction (TPR) was performed using a 5% H2/Ar mixture (30 inL min - 5°C min ). 

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