Characterization of Solid Catalysts

Important data about industrial catalysts include the size, shape, and mechanical strength of the catalyst particles and the (weight) loss on ignition. 

Other data required to classify industrial catalysts are total surface area per unit volume or per unit weight pore volume and pore-size distribution and catalytically active surface area per unit volume or per unit weight. 

With supported catalysts in particular the catalytically active surface is much smaller than the total surface area, because the surface area of the support is usually much larger than the active surface area. With non-supported catalysts, such as Raney metals, it is, however, also highly important to compare the total surface area with the active surface area to assess whether residual alumina covers a significant fraction of the metal surface. Therefore separate measurements of total surface area and catalytically active surface area are required. 

---

Figure 1.13 Raman spectra for a number of transition metal oxides supported on y-AI203 [75,102], Three distinct regions can be differentiated in these spectra, namely, the peaks around 1000 cm-1 assigned to the stretching frequency of terminal metal-oxygen double bonds, the features about 900 cm 1 corresponding to metal-oxygen stretches in tetrahedral coordination sites, and the low-frequency (<400 cm-1) range associated with oxygen-metal-oxygen deformation modes. Raman spectroscopy can clearly complement IR data for the characterization of solid catalysts. (Reproduced with permission from The American Chemical Society.)...

Hunger, M. and Wang, W. (2006) Characterization of solid catalysts in the functioning state by Nuclear Magnetic Resonance spectroscopy. Adv. Catal.,... 

Characterization of Solid Catalysts in the Functioning State by Nuclear Magnetic Resonance Spectroscopy... 

VIII] CHARACTERIZATION OF SOLID CATALYSTS IN THE FUNCTIONING STATE 195... 

For more than five decades, the methods of surface physics and chemistry have provided some of the most incisive results advancing our understanding of the catalytic action of solids at the molecular scale. Characterizations by physical methods have demonstrated the dynamic nature of catalyst surfaces, showing that their structures, compositions, and reactivities may all be sensitive to temperature and the composition of the reactive environment. Thus, the most insightful catalyst characterizations are those of catalysts as they function. This volume of Advances in Catalysis is dedicated to the topic of physical characterization of solid catalysts in the functioning state. Because the literature of this topic has become so extensive, the representation will extend beyond the present volume to the subsequent two volumes of the Advances. 

The growing interest in physical characterization of solid catalysts as they function has stimulated a new series of congresses, the first held in Lunteren (The Netherlands) in 2003 and the second in Toledo in 2006. The subject has been documented in recent books (B. M. Weckhuysen, Ed., In situ Spectroscopy of Catalysts, American Scientific Publishers, 2004, and J. F. Haw, Ed., In situ Spectroscopy in Heterogeneous Catalysis, Wiley-VCH, 2002) and in topical issues of journals Top. Catal. 15 (2001) Phys. Chem. Chem. Phys. 5, issue 20 (2003) and Catal. Today 113 (2006). It is our intention that our set of volumes be more nearly comprehensive than these publications, as well as providing many newer results. 

Hunger and Wang provide an account of advances in the characterization of solid catalysts in the functioning state by nuclear magnetic resonance spectroscopy. Examples include investigations of zeolite-catalyzed reactions with isotopic labels that allow characterization of transition states and reaction pathways as well as characterization of organic deposits, surface complexes, and reaction intermediates formed in catalyst pores. 

UV-vis-NIR spectroscopy is a valuable tool for characterization of solid catalysts on the basis of measurements of electronic and vibrational transitions. The following information may be obtained from the spectra ... 

---