The present invention relates to a method for selecting at least one catalyst from a catalyst library on the basis of the reactivity thereof in a chemical conversion process, characterised in that it comprises at least the following steps: (e) testing the catalytic activity of a first catalyst from said catalyst library with respect to a reaction medium containing, as the compounds to be converted, at least one reactivity probe having a labelling system and including at least one reaction unit capable of reacting in said chemical conversion; (f) analysing the reaction medium after said catalytic test for the purpose of qualitatively and/or qualitatively characterising the resulting compounds; (g) repeating steps (a) and (b) for at least one other catalyst in said library; and (h) comparing the analysis results for each catalyst in order to characterise at least one catalyst having the required reactivity in said chemical conversion.