Refining catalyst business shows signs of strong recovery in 2004–2007
- Publisher
- Elsevier Science
- Year
- 2004
- Weight
- 79 KB
- Volume
- 2004
- Category
- Article
- ISSN
- 1351-4180
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✦ Synopsis
Heterogeneous catalytic chemists have always known that size matters. Since catalysis is a surface effect, and active surface is a function of particle size, it is obvious that particle size is an important variable. However, the observations may be counter-intuitive. Recent work 1 on the deep oxidation of n-hexane and toluene over platinum on alumina has shown the surface reaction to be faster for larger platinum crystallites. This is attributed to a decrease in the Pt-O bond strength with enlargement of the Pt crystal size.
Conversely, some nano-particulate catalysts are more active than their larger cousins, presumably because of electronic effects which take effect at these small dimensions. This is particularly true of gold catalysts.
The particle size of the support can also be important. Recent Spanish work 2 has shown that the activity of gold on ceria can be increased by two orders of magnitude if the ceria is made nanoparticulate.
It is now obvious that catalyst optimization requires much more than optimization of gross elemental composition as is achieved by current combinatorial techniques. For oxide catalysts it requires also the optimisation of morphology on several scales, which is achieved by optimising processing conditions (ageing, washing, drying, calcining) which is difficult to achieve in today's combinatorial equipment.
Nanoscience is fast becoming recognised, as evidenced by the five books listed in Bookshelf, and nano-catalysis likewise 3,4 . This is an idea whose time has come.