Working with Other Active Hydrogen Atoms

Working with Other Active Hydrogen Atoms.273... 

If the light intensity is kept low the atom and radical concentrations are small so that loss of hydrogen atoms by reactions (4) and (5) is unimportant, and if concentrations of products are kept low reactions (6)-(8) are unimportant. Back and van der Auwera worked under these conditions, so that the rate of hydrogen production was a measure of the rate of reaction (1). They found that reaction (1) proceeds with a rather low efficiency, in contrast to the behaviour of other saturated hydrocarbons where the efficiency is close to unity. The efficiency also increases markedly with temperatoe. It may be that reaction (1) has a small activation energy. 

A comparative review on the evaluation of the catalysts Al, A2, B1 and B2 reveals that activity and dispersity are two closely related parameters which is influenced by the mode of preparation especially with respect to removal of chloride or to the final calcination temperature. Earlier works had identified benzene hydrogenation on supported platinum catalysts as a facile or structure insensitive reaction(5). A facile reaction may be defined as one for which the specific activity is practically independent of its mode of preparation(6). In other words all surface atoms are believed to be the active sites in a facile reaction without any dependence on the coordination number of site or on the collective properties of the crystallite. 

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