Heterogeneous process short-time catalysis

In the sixties of past century, a few patents issued to Bergbau Chemie [5,48,49] and to Mobil Oil [50-52], respectively described the use of CFPs as supports for catalytically active metal nanoclusters and as carriers for heterogenized metal complexes of catalytic relevance. For the latter catalysts the term hybrid phase catalysts later came into use [53,54], At that time coordination chemistry and organo-transition metal chemistry were in full development. Homogeneous transition metal catalysis was expected to grow in industrial relevance [54], but catalyst separation was generally a major problem for continuous processing. That is why the concept of hybrid catalysis became very popular in a short time [55]. 

In relation to the field of heterogeneous catalysis, an advantage of PL is that solid samples can be easily investigated. Other assets include its high sensitivity (often samples of less than a few tens of mg only are needed), the short analysis times required, and the different types of data, as discussed in the previous sections, which can be obtained from the investigation of the spectral and temporal profiles of both the excitation and emission processes (Anpo and Che, 1999). 

Although there is a lot of information available about surfaces and surface species there is unfortunately no direct translation between such information and a more detailed understanding of the actual heterogeneous catalysis processes. There are several reasons for this surface studies normally have to be carried out in ultra-high vacuum and at low temperatures, a far cry from the conditions of a catalytic reaction which may typically only occur at temperatures of greater than 100°C and pressures of several bar. The residence times of the species that participate in catalyses are normally very short and their concentration is very low, thus it has only quite recently become possible to derive any meaningful information from the surface studies about the catalyses. Furthermore, although many species are detected on surfaces, most are spectator species, which do not participate in, and are unaffected by, the desired catalyses. 

---