Preferred Label : fractional selectivity;
Detailed label : fractional selectivity in catalysis;
IUPAC definition : The term selectivity (S) is used to describe the relative rates of two or more competing
reactions on a catalyst. Such competition includes cases of different reactants undergoing
simultaneous reactions or of a single reactant taking part in two or more reactions.
For the latter case, S may be defined in two ways. The first of these defines a fractional
selectivity, S F, for each product by the equation \[S_{{F}} \frac{\xi _{i}}{\sum
\xi _{i}}\] The second defines relative selectivities, S R, for each pair of products
by \[S_{{R}} \frac{\xi _{i}}{\xi _{j}}\] In each case, ξ i and ξ j are the rates of
increase of the extent of reactions i i /i and i j /i respectively, i.e. \[\xi
_{i} \frac{\mathrm{d}\xi _{i}}{\mathrm{d}t}\] and \[\xi _{j} \frac{\mathrm{d}\xi _{j}}{\mathrm{d}t}\]
where ξ i and ξ j are the extents of reactions i and j respectively.;
Origin ID : F02496;
See also
The term selectivity (S) is used to describe the relative rates of two or more competing
reactions on a catalyst. Such competition includes cases of different reactants undergoing
simultaneous reactions or of a single reactant taking part in two or more reactions.
For the latter case, S may be defined in two ways. The first of these defines a fractional
selectivity, S F, for each product by the equation \[S_{{F}} \frac{\xi _{i}}{\sum
\xi _{i}}\] The second defines relative selectivities, S R, for each pair of products
by \[S_{{R}} \frac{\xi _{i}}{\xi _{j}}\] In each case, ξ i and ξ j are the rates of
increase of the extent of reactions i i /i and i j /i respectively, i.e. \[\xi
_{i} \frac{\mathrm{d}\xi _{i}}{\mathrm{d}t}\] and \[\xi _{j} \frac{\mathrm{d}\xi _{j}}{\mathrm{d}t}\]
where ξ i and ξ j are the extents of reactions i and j respectively.
