How hard is mechanism elucidation in catalysis? Combinatorial analysis of C1 chemistry

Most chemical reactions occur over multiple steps whose identity is elucida ted by experiment, yielding a reaction mechanism. Knowledge of cognitive sc ience suggests that mechanism elucidation can be viewed as a knowledge-guid ed search within a combinatorial space. The MECHEM computer program searche s this space comprehensively for the simplest plausible mechanisms. We use MECHEM to find mechanisms for Fischer-Tropsch chemistry and CO2 re-forming of methane, both heterogeneous catalytic reactions of current importance. T he results reveal hundreds of equally simple mechanisms consistent with evi dence. Hence, mechanism elucidation in catalysis is a much harder problem t han is ordinarily realized.