Catalysis

Name:
Catalysis
Detailed information:
One of the most important phenomena in nature, catalysis is the loosening of the chemical bonds of two (or more) reactants by another substance in such a way that a fractionally small percentage of the latter can greatly accelerate the rate of the reaction while remaining unconsumed. See Catalyst. Thus, one part by volume of catalyst can activate thousands of parts of reactants. Though the mechanism of their action is not completely known, the electronic configuration of the surface molecules of the catalyst is often the critical factor. The surface irregularities give rise to so-called active points at which intermediate compounds can form. Most industrial catalysis is performed by finely divided transition metals or their oxides. Solid catalysts may combine chemically (bond) at the surface with one or more of the reactants. This is known as chemisorption and occurs on only a small portion of the catalyst surface (i.e., at the active points); it results in changing the chemical nature of the chemisorbed molecules. Catalysis of chemical reactions by surfaces must proceed by chemisorption of at least one of the reactants. Catalysis and catalytic mechanisms permeate almost every aspect of chemistry and are of such wide-ranging importance that they have long been the subject of continuing research. Many interrelated disciplines are involved, among them organometallic reactions (stereospecific catalysts), electrochemistry, colloid and surface chemistry, coordination chemistry, and biochemistry. One example of comparatively recent investigation is so-called cluster catalysis, in which a metal is bonded to carbon monoxide to form a metallic cluster anion. Such aggregations or crystallites may be up to 12 Å in diameter. Metal cluster research is motivated by the need to develop selective catalysts for C₁ compounds, in view of the likelihood that the basic raw materials for chemistry in the future will be derived from coal or biomass rather than oil. Another research development is the creation of a uniquely shaped catalyst particle that permits greater efficiency because of the increase in surface-to-volume ratio. Such particles are known as amphora catalysts.